{"Bibliographic":{"Title":"Satellite Doppler positioning : proceedings [of the] International Geodetic Symposium, October 12-14, 1976, hosted by Physical Science Laboratory, New Mexico State University, Las Cruces, N.M. Volume 1.","Authors":"","Publication date":"1976","Publisher":""},"Administrative":{"Date created":"08-17-2023","Language":"English","Rights":"CC 0","Size":"0000698718"},"Pages":["QB\n343\nSatellite\nI53\n1976\nv.1\nDoppler\nPositioning\nVol. 1\nPROCEEDINGS\nINTERNATIONAL\nGEODETIC SYMPOSIUM\nCosponsored by:\nU.S. DEFENSE MAPPING AGENCY\nNATIONAL OCEAN SURVEY, NOAA\nOctober 1976","QB\n343\nSatellite\nI53\n1976\nV.I /\nDoppler\nPositioning\nVOLUME 1\nPROCEEDINGS\nINTERNATIONAL\nMARINE AND EARTH\nGEODETIC SYMPOSIUM\nSCIENCES LIBRARY\nOctober 12-14,1976\nAUG2 6 1977\nHosted by:\nPhysical Science Laboratory\nN.O.A.A.\nU. S. Dept. of Commerce\nNew Mexico State University\nBox 3548\nLas Cruces, N. M. 88003\nCosponsored by:\nU.S. Defense Mapping Agency\nNational Ocean Survey, NOAA\n77\n3014","i\nACKNOWLEDGEMENTS\nThe International Geodetic Sympsoium on Satellite Doppler Positioning\nwas sponsored by The Defense Mapping Agency and The National Ocean Survey\nof The National Oceanic and Atmospheric Administration.\nIt was hosted by Physical Science Laboratory of New Mexico State\nUniversity. Numerous individuals were responsible for the success of the\nsymposium but worth special recognition are Gail Franzen, who coordinated\nthe myriad symposium details, and Mary Dieringer, who organized this entire\nproceedings. Their skillful and untiring efforts are especially appreciated.","ii","iii\nTABLE OF CONTENTS - VOLUME I\nPage\nWELCOME\n1\nRichard P. Peat, Program Chairman\nHarold R. Lawrence, Director, Physical Science Laboratory\nDr. Gerald W. Thomas, President, New Mexico State University\nKEYNOTE ADDRESS\n2\nGeorge Veis, National Technical University of Athens\nTHE DOPPLER CONCEPT AND THE OPERATIONAL NAVY NAVIGATION SYSTEM.\n5\nRichard B. Kershner, Applied Physics Laboratory, The Johns\nHopkins University\nPOSITION DETERMINATION USING THE TRANSIT SYSTEM\n25\nHarold D. Black, Applied Physics Laboratory, The Johns\nHopkins University\nPOINT POSITIONING CONCEPT USING PRECISE EPHEMERIS\n47\nRichard J. Anderle, Naval Surface Weapons Center\nCONCEPT OF SATELLITE DOPPLER POSITIONING USING TRANSLOCATION\nTECHNIQUES\n77\nDavid E. Wells, Atlantic Oceanographic Laboratory, Bedford\nInstitute of Oceanography, Dartmouth, Nova Scotia\nDOPPLER POSITIONING BY THE SHORT ARC METHOD\n97\nDuane C. Brown, DBA Systems, Inc.\nDMATC DOPPLER DETERMINATION OF POLAR MOTION\n141\nBruce R. Bowman, Caroline F. Leroy, Defense Mapping Agency\nTopographic Center\nMEDOC EXPERIMENT OR THE FRENCH POLAR MOTION PROJECT\n159\nB. Guinot, Bureau International de 1'Heure, Paris, France\nF. Nouel, Groupe de Recherches de Géodésie Spatiale, Toulouse,\n(GRGS), France\nSATELLITE TECHNOLOGY APPLIED TO ANTARCTIC MAPPING PROGRAM\n175\nWilliam R. MacDonald, U.S. Geological Survey\nTHE CANADIAN DOPPLER SATELLITE NETWORK.\n187\nJ. Kouba, J. D. Boal, Geodetic Survey of Canada, Surveys and\nMapping Branch, Department of Energy, Mines & Resources,\nOttawa, Canada\nTHE NATIONAL GEODETIC SURVEY DOPPLER SATELLITE POSITIONING PROGRAM.\n207\nWilliam E. Strange, Larry D. Hothem, NGS/NOS/NOAA","iv\nTABLE OF CONTENTS - VOLUME I (Continued)\nPage\nAPPLICATIONS OF DOPPLER SATELLITE SYSTEMS IN REMOTE REGIONS IN AND\nNEAR AUSTRALIA.\n229\nD. McLuskey, The Royal Australian Survey Corps, Department of\nDefense, Canberra Act Australia\nPOSITION PAPER SHOWING COMPARISONS WITH THE AUSTRALIAN GEODETIC\nSURVEY AS AT SEPTEMBER 1976.\n235\nJohn McLuck, Division of National Mapping, Australia\nWORKSHOP ON RECEIVER HARDWARE, FORMATTING AND HANDLING DATA\n241\nP.E.P. White, Applied Physics Laboratory, The Johns Hopkins\nLaboratory\nA PORTABLE GEODETIC POSITIONING SYSTEM WITH REAL-TIME COMPUTATION.\n245\nWalter J. Piurek, James E. Johnson, John Vivian, Satellite\nPositioning Corporation\nDOPPLER SURVEY EQUIPMENT : BACKGROUND, REQUIREMENTS, AND TRENDS\n249\nThomas A. Stansell, Jr., Magnavox Government and Industrial\nElectronics Company, Advanced Products Division\nA CRITICAL ANALYSIS OF FIELD OPERATIONS USING PORTABLE, UNATTENDED\nDOPPLER SATELLITE INSTRUMENTATION\n279\nPaul D. Rodgers, JMR Instruments, Inc.\nSTANDARDIZATION OF DOPPLER POINT POSITIONING RESULTS\n303\nJohn D. Love, Defense Mapping Agency Topographic Center\nATMOSPHERIC DRAG ANALYSES OF LOW-ALTITUDE DOPPLER BEACON SATELLITES.\n343\nK.S.W. Champion, Aeronomy Division, Air Force Geophysics\nLaboratory (AGSC), J.M. Forbes, Space Data Analysis Laboratory,\nBoston College\nMODELING OF RESIDUAL RANGE ERROR IN TWO FREQUENCY CORRECTED DOPPLER\n357\nDATA\nArnold J. Tucker, James R. Clynch, H. Lyle Supp, Radio Sciences\nDivision, Applied Research Laboratories, The University of Texas\nat Austin\nDEVELOPMENT OF DOPPLER ACTIVITY AT I.R.O.E\n377\nL. Ciraolo, L. Mezzani, Istituto di Ricerca sulle Onde\nElettromagnetiche, Firenze, Italia\nCOMPARISON OF DOPPLER DERIVED UNDULATIONS WITH GRAVIMETRIC\nUNDULATIONS CONSIDERING THE ZERO-ORDER UNDULATIONS OF THE GEOID\n389\nRichard H. Rapp, Reiner Rumme1, Department of Geodetic Science,\nThe Ohio State University\nRESULTS FROM PORTABLE DOPPLER RECEIVERS USING BROADCAST AND PRECISE\n399\nEPHEMERIDES.\nCaroline F. Leroy, Defense Mapping Agency Topographic Center","V\nTABLE OF CONTENTS - VOLUME I\n(Continued)\nPage\nMETHODOLOGY AND FIELD TESTS OF GDOP, A GEODETIC COMPUTATION PACKAGE\nFOR THE SHORT ARC ADJUSTMENT OF SATELLITE DOPPLER OBSERVATIONS\n417\nC. Goucher, Institut Géographique National, France\nGEOMETRIC POSITIONING VIA SATELLITE OF A DRILLING PLATFORM IN THE\nNORTH SEA\n427\nA.R. Dennis, Analytical Technology Laboratories, Inc.\nVOLUME II\nRELATING DOPPLER DATUM TO ORDNANCE SURVEY DATUM.\n453\nLt. Col. M.R. Richards RE, Ordnance Survey of Great Britain\nRECOMMENDATIONS OF THE WORKSHOP ON DOPPLER DATA REDUCTION AND\nANALYSIS\n461\nREFERENCE ORBITS FROM RANGE AND DOPPLER OBSERVATIONS\n465\nJ. Berbert, H. Parker, NASA/Goddard Space Flight Center\nA COMPARISON OF SEVERAL DOPPLER-SATELLITE DATA REDUCTION METHODS\n479\nRonald Brunell, JMR Instruments, Inc.\nNEW POSITIONING SOFTWARE FROM MAGNAVOX\n499\nRon Hatch, Magnavox Government and Industrial Electronics\nCompany, Advanced Products Division\nNAVAL SURFACE WEAPONS CENTER REDUCTION AND ANALYSIS OF DOPPLER\nSATELLITE RECEIVERS USING THE CELEST COMPUTER PROGRAM.\n519\nJames W. O'Toole, Naval Surface Weapons Center\nVARIATIONS IN DOPPLER POSITIONS RESULTING FROM DIFFERENCES IN\nCOMPUTER PROGRAMS AND TROPOSPHERIC REFRACTION COMPUTATIONS\n551\nHaschal L. White, Defense Mapping Agency, Aerospace Center\nANALYSIS OF GEOCEIVER RECEIVER DELAYS\n577\nFran B. Varnum, Defense Mapping Agency Topographic Center\nWORKSHOP ON POINT POSITIONING AND TERRESTRIAL ADJUSTMENTS\n587\nEFFECT OF GEOCEIVER OBSERVATIONS UPON THE CLASSICAL TRIANGULATION\nNETWORK\n591\nRobert E. Moose, Soren W. Henriksen, National Geodetic Survey,\nNational Ocean Survey, NOAA\nUPDATING SURVEY NETWORKS - A PRACTICAL APPLICATION OF SATELLITE\nDOPPLER POSITIONING.\n657\nJoseph F. Dracup, Horizontal Network Branch, National Geodetic\nSurvey, NOS, NOAA","vi\nTABLE OF CONTENTS - VOLUME II (Continued)\nPage\nADJUSTMENT OF TERRESTRIAL NETWORKS USING DOPPLER SATELLITE DATA\n675\nMark G. Tanenbaum, Naval Surface Weapons Center\nAN ORB DOPPLER PROGRAM ANALYSIS AND ITS APPLICATION TO EUROPEAN\n707\nDATA.\nJ. Usandivaras, Université de Tucuman, Conicet, Argentine\nP. Pâquet, R. Verbeiren, Observatoire Royal de Belgique,\nBruxelles, Belgium\nCONCEPTS OF THE COMBINATION OF GEODETIC NETWORKS\n727\nD.B. Thomson, E.J. Krakiwsky, Department of Surveying Engineering,\nUniversity of New Brunswick, Fredericton, New Brunswick\nINTRODUCTION TO THE WORKSHOP ON POLAR MOTION.\n747\nPaul Melchior, Royal Observatory of Belgium, Uccle-Bruxelles\nMINUTES OF THE WORKSHOP SESSION ON POLAR MOTION\n755\nJ. Popelar, Department of Energy, Mines & Resources,\nOttawa, Canada\nDETERMINATION OF GEOPHYSICAL PARAMETERS FROM LONG TERM ORBIT\nPERTURBATIONS USING NAVIGATION SATELLITE DOPPLER DERIVED EPHEMERIDES.\n763\nBruce R. Bowman, Defense Mapping Agency Topographic Center\nAPPLICATION OF DOPPLER SATELLITE TRACKING SYSTEM FOR POLAR MOTION\n783\nSTUDIES IN CANADA\nJ.A. Orosz, J. Popelar, Gravity and Geodynamics Division, Earth\nPhysics Branch, Department of Energy, Mines & Resources,\nOttawa, Canada\nDOPPLER DATA TRANSMISSION AND HANDLING AT THE GEODETIC INSTITUTE\n793\nOF UPPSALA.\nMichael 0' 'Shaughnessy, Geod. Inst. Uppsala University,\nUppsala, Sweden\nERRORS OF DOPPLER POSITIONS OBTAINED FROM RESULTS OF TRANSCONTINENTAL\n813\nTRAVERSE SURVEYS.\nB.K. Meade, NOAA, National Ocean Survey, National Geodetic Survey\nDETERMINATION OF NORTH AMERICAN DATUM 1983 COORDINATES OF MAP\n831\nCORNERS\nT. Vincenty, National Geodetic Survey, National Ocean Survey, NOAA\nDOPPLR - A POINT POSITIONING PROGRAM USING INTEGRATED DOPPLER\nSATELLITE OBSERVATIONS\n839\nRandall W. Smith, Charles R. Schwarz, William D. Googe, Defense\nMapping Agency Topographic Center","vii\nTABLE OF CONTENTS - VOLUME II (Continued)\nPage\nCLOSING REMARKS\n891\nOwen W. Williams, Defense Mapping Agency\nLIST OF ATTENDEES\n895\nPHOTOGRAPHS TAKEN AT SYMPOSIUM.\n899","viii","ix\nFORWORD\nRichard P. Peat\nSpecial Projects Division\nDepartment of Programs, Plans and Operations\nDefense Mapping Agency\nThe stimulus for this symposium was provided in August 1975 at the\nXVIth General Assembly of the International Association of Geodesy in\nGrenoble, France. Throughout the Association there was a growing concern\nthat a forum was needed for establishing dialogue among various users of\nsatellite Doppler methods concerning possible future standardization of\ndata formatting, data handling and data reduction.\nTwo U.S. Agencies, the National Ocean Survey and the Defense Mapping\nAgency, accepted the responsibility for organizing and conducting the\nSymposium. The Physical Science Laboratory of the New Mexico State\nUniversity agreed to host the meetings. Later, at its 1975 Fall Meeting\nin San Francisco, the American Geophysical Union voted to sanction the\nproposed Symposium.\nJudging from the enthusiastic reaction of the large audience, which so\nwell represented the international geodetic community, the objectives defined\nby the organizing committee were achieved.\nOn behalf of the Committee, I would like to thank all those hard\nworking participants for their cooperation and valuable contributions,\nwithout which this important forum would not have been possible.","","1\nWELCOME\nRICHARD P. PEAT, Special Projects Division, Department of Programs, Plans\nand Operations, Defense Mapping Agency\nGoodmorning, I'm Dick Peat! I'm the Program Committee Chairman for this\nSymposium and if I seem pleased this morning, it's because I am. There are\n220 of you at the latest count, and we're from 27 different countries, and\nI think that that's proof positive that this session was needed. We all know\nwhat we're here for and I'm not going to spend too much time in formalities\nbut on behalf of the National Ocean Survey and the Defense Mapping Agency,\nwho are the co-sponsors of this symposium, I bid you welcome. During the\nrest of this week, we will be the guests of the very gracious hosts at\nPhysical Science Laboratory of New Mexico State University and for your\nwelcome to PSL, I'm going to introduce to you now Mr. Harold Lawrence who is\nthe Director of the Physical Science Laboratory/New Mexico State University.\nHAROLD LAWRENCE, Director, Physical Science Laboratory\nLet me too add my welcome but to be more formal about this, I would now\nlike to turn the meeting over to Dr. Gerald W. Thomas, President of New Mexico\nState University.\nDR. GERALD W. THOMAS, President, New Mexico State University\nIt's a special pleasure to welcome you here this morning and to add to\nwhat Mr. Peat has said, we're very pleased to particularly have visitors from\nother countries here. New Mexico State University has been involved in programs\nof this nature for many years. We're very pleased to have you on our campus.\nWe hope that while you're in the Las Cruces area, you will take time to look\naround and enjoy southern New Mexico. We're heavily involved, as many of you\nknow, in solar energy research. We hope that you will have time while you're\non campus to visit our new 3-bedroom house which is heated and cooled by solar\nenergy, and also right across the street, our new Department of Agriculture\nbuilding, which is also heated and cooled by solar energy. We hope also that\nyou will have time to enjoy Las Cruces, El Paso, and Juarez while you're here\nand with that, welcome to New Mexico State University.\nRICHARD P. PEAT\nBack when we first started to think about this symposium and to formulate\nsome of the objectives and talk about what we wanted to do here, the first\nthink that we thought about was who can we find to be the keynote speaker for\nthis symposium; somebody who can set the stage, provide the tone for the rest\nof the symposium and we didn't have to think very long. We decided with\nunanimous agreement early on in the Program Committee meetings that George\nVeis was the man who should keynote this symposium. And he has kindly\nconsented to do that, and he's here and he's ready to keynote this symposium\nand so I would like now to introduce George Veis to you. Dr. Veis is Dean\nof the School of Rural and Surveying Engineering at the National Technical\nUniversity of Athens in Greece. You all know that he has been a tireless\nand very productive and very vigorous worker in this field and I can think\nof nobody who is more appropriate for us to hear as a keynote speaker.","2\nKEYNOTE ADDRESS\nGEORGE VEIS\nDean of the School of Rural and Surveying Engineering\nNational Technical University of Athens in Greece\nWhen the organizers of this symposium asked me to give this keynote address,\nmy first reaction, to be honest, was to decline. The reason was that I don't\nconsider myself to be very well acquainted with Doppler tracking and its utiliza-\ntion for satellite work. I have always been considered, maybe erroneously, to\nbe the big defender of optical and photographic tracking for satellite work.\nSome of the reason comes from the fact that in the early 60's there was a move\nto stop the operation of the Baker Nunn network and I was strongly against it,\nbelieving that photographic tracking still had a lot to provide to Geodesy. Due\nto this, some thought I was against electronic tracking, which I was not. I\nhave to state my admiration for the ingenious and elegant way in which Doppler\ninformation can be used to provide an easy way to obtain results of Geodetic\nimportance. So after a second thought, I agreed to deliver this address in a\nway to publicly and officially show my appreciation for this part of satellite\nGeodesy, which I am glad to do.\nI think that satellite Geodesy now has almost 20 years of activity and has\nmade a great impact on satellites in general. I seriously believe that what\nhas been obtained during this last 20 years exceeds what had been gathered in\nthe last thousand years. The success in satellite Geodesy has come about by\nyoung people from different disciplines working together to find the size and\nshape of the earth, the gravity field, and to find positions on the earth.\nSatellites were used from the beginning for making Geodetic studies by\nmaking straight-forward observations in distances and angles. Distances were\nused to improve the gravity field of the earth and locating positions in a\nreally geocentric system on the globe. The Doppler information turned out to\nbe a good way to do orbital work, that is, we measure the radial velocity by\nreceiving a frequency that changes with the relative velocity. This gives an\nintegration over the variation of the range and we get the differences in the\ndistances. It's as simple as that, but sometimes principles are easier under-\nstood than applications. This was the case of Doppler tracking where there\nis a lot of technology and hardware involved and several byproducts that had\nto be solved at the same time.\nWe should be grateful to those including Guier, Newton, and Weiffenbach,\nwho started using Doppler observations to compute the first orbits in the\nearly days. Very soon the idea of inverting the process to navigate became\na reality. At the time, it was thought that 100-200 meter accuracy would be\nthe average requirement for general purpose navigation. The next approach\nwas to use the information not for navigation but to determine permanent\npositions on the earth. Geodesy requires that we work in four dimensions\ninstead of three so time must be taken into consideration since now we are\nnavigating rocks and tectonic plates as well as ships and planes so time is\nvery important.","3\nI think that in general one could see the problem of Doppler tracking\nas very complex and depending on many, many parameters. They include the\nobserving position, the problem of defining the satellite orbit because of\nthe earth's odd gravity field, the effects of the sun and the moon, and\natmospheric drag, to mention only a few.\nThere are many parameters that enter into explaining what the observations\nhave given you. As a rule what people do is decide what they want to investigate\nand call everything else parasitic. So for someone who is just interested\nin finding positions on the earth, he will say the effect of air drag is parasitic,\nlet' get rid of it if we can. However, we are interested in the atmospheric\ndensities at those heights so it is no longer parasitic.\nOur problems very often are not parasitic and in Geodesy, as well as other\nsciences, some way in devised to separate things or to devise schemes in which\nyou could eliminate some of the phenomena that you did not want to solve for.\nA typical example is the late Pageos satellite which was built in such a way\nthat the effects from the solar radiation pressure was minimized so the effect\nyou wanted to measure was dominant in the observations.\nWell at any rate, independent of whether we have decided to use one\nscheme or the other, eliminate effects or have a global solution which will\nhave many, many observations, many, many unknowns (and has the advantage of\nbeing a unique solution but at the same time solves for everything), I think\nit will be appropriate to see what has been achieved during this 20 years.\nI think we can now say that we have obtained by Doppler tracking alone the\nglobal solutions from the work that has been done by Dick Anderle at the Naval\nWeapons Laboratory. We now have included in a unique global solution the positions\nof about 20 points on the earth plus about 40 more positions of the BC-4 network.\nWe know the gravity field well enough now so that it won't affect the positions\nof the stations to the accuracies that we are now working with. Updating models\nis a never-ending problem. You improve the gravity field; after it's improved,\nyou are improving your station position; with an improved station position, you\ngo back to the gravity field. You then come to a stage that you have to improve\nyour instrumentation. You improve your instruments and you have more errors\ncoming out from all the parasitic effects. You have to find models to correct\nfor this and you can go on and on in something that never ends.\nWe have now reached a stage that it has been definitely shown that we could\ndetermine the Polar Motion using Doppler with an accuracy which is comparable\nto\nthe classic astronomic techniques. By using smaller nets, rather than the global\nnetwork, we can observe the satellite from several points at the same time. In\nthis manner, some of the effects observed could be considered parasitic. With\nthe new equipment shown here today, you can go out in the field for a few days\nand get your position very easily. I think that there is no doubt that this is\nthe system that applied Geodesy will be using in the near future.\nHave we solved everything on Doppler tracking? No. Actually, if we had\nwe probably would not be having this symposium unless we just wanted to say how\nwell a job we have done and let's celebrate.","4\nLet me state some of the things that I think still have to be worked on.\nFirst of all, I think that we need to further improve the instrumentation and\nI think that modern technology is such that we would certainly be able to do\nthat. I think that it is maybe necessary to start thinking about what has been\nvery often called the inverted system. Up to now, the ground equipment has been\nrather elaborate and if you want to do geodynamic studies with a higher density\nof ground tracking points, we have to think of systems which will carry most of\nthe expense in the satellite and that the ground station could be as simple and\ninexpensive as possible.\nI think that we still have to do some work on the reduction of data and\ncollection of ionospheric and tropospheric data which at this time may be a\nlimiting factor. There is still work to be done on the theories of celestial\nmechanics and the computation of orbits. We have to improve the gravity field,\nwhich is a continuing thing and will never really end. The question of the\ndefinition of the reference systems must be addressed if we are to reduce some\nof the problems in global solutions. Doppler has its own reference system\nthat must be correlated with other systems used in the past or planned for the\nfuture. A lot of investigation needs to be done in adjusting of present networks.\nFinally I think that we will be faced with the need to coordinate large\nprograms and this is something that astronomers and geodisists have done in\nthe past, and quite successfully I might add, and we have gained a lot of\nexperience in how to do it. I think that it is for these reasons that we have\nto solve all these problems that are brought up at this symposium and we have\nthe problem that we hear what has been achieved in terms of global solutions,\nof small problems from determining stations all over the earth. We have to\nlook at how we are going to solve the future problems that come up and even\nmore, how we are going to organize our future experiments.\nI think this is the first international symposium in that area and I think\nthat we should all congratulate the organizers for taking the initiative to start\nthis symposium which maybe, in the future, will be referred to as the first of\nits kind. This is the first international symposium in Geodesy and we didn't\ncome to celebrate what has been done but primarily to work and try in the\nsecond symposium, to announce much better achievements and prepare for the\nnext generation of problems.\nMy time is up and it is time for the participants in the symposium to\nsay what they have done. Thank you very much.","5\nTHE DOPPLER CONCEPT AND THE OPERATIONAL\nNAVY NAVIGATION SYSTEM\nRichard B. Kershner\nApplied Physics Laboratory\nThe Johns Hopkins University\nThe Navy Navigation Satellite System, also known as the TRANSIT system,\nwas invented in 1958 by the late Frank T. McClure, who was at that time the\nChairman of the Research Center of the Applied Physics Laboratory of The\nJohns Hopkins University. The concept was based on technical developments\ncarried out by George C. Weiffenbach and William H. Guier, who were then on\nthe staff of the same Research Center. Shortly after the launching of the\ninitial Russian Sputnik, these two men made careful measurements of the\nDoppler shift exhibited on signals received from the Sputnik due to the\nrelative motion of the satellite-borne transmitter and a receiving station\nat a fixed location on a rotating earth. In a remarkable technical tour de\nforce they showed that it was possible to determine a quite accurate orbit\nfor the Sputnik by the analysis of a single such Doppler curve. Dr. McClure's\nconcept was to establish orbiting satellites transmitting stable frequencies,\nto receive these frequencies at one or more fixed ground sites measuring\nprimarily the Doppler shift and thus to generate their orbits by the techni-\nque developed by Dr. Guier and Dr. Wieffenbach. Subsequently a user who\nwished to navigate would observe the Doppler shift which he would use to\ndetermine his own unknown position. He would, of course, need to be informed\nof the satellite's orbit and the natural system approach was to use the\nsatellite itself as a means for transmitting this orbit information; e.g.,\nin the form of a modulation of the basic carrier frequency. The system\nconcept, which indeed is the way the system has been implemented, is shown\nin Fig. 1.\nThe system was developed with the primary objective of providing preci-\nsion updates of location of Polaris submarines. Indeed at least one satellite\nhas existed to provide updates to the Polaris fleet continuously since 1964.\nSatellites from 1964 to 1969 had limited life times (up to one year) due to\nvarious problems, most particularly a \"wear-out\" failure mode due to the\neffect of thermal cycling. The last of these problems was resolved by 1967\nand all Oscar satellites launched since 1967 are still operable. There are\nsix satellites which currently serve the constellation; three of these were\nbuilt by the Applied Physics Laboratory of The Johns Hopkins University and\nthree by the Radio Corporation of America Astro-Electronics Division. The\ntotal system reliability is shown in Fig. 2, where the column headed \"Out of\nService Time\" means the total time in which the corresponding satellite did\nnot have a totally valid navigation message and accordingly was not available\nto provide a navigation fix to the user. These impressive figures are a\ntribute both to the simplicity and inherent reliability in the system design\nand the competence of the group responsible for the day-to-day system opera-\ntion, which is a Navy group called the Navy Astronautics Group with head-\nquarters at Point Mugu, California.","6\nThe problems that were expected in the initial consideration of the\nsystem to have an impact on the accuracy achieved were:\n1. Frequency stability of the satellite oscillator,\n2. Ionospheric refraction,\n3. Tropospheric refraction,\n4. Accurate orbit determination and prediction.\nThe first three of these factors proved substantially less difficult than\nanticipated and until very lately have not influenced the accuracy achievable\nbecause errors were dominated by the orbit determination and prediction\nproblems. The fourth problem, which turned out to be primarily problems of\ngeodesy, proved much more challenging than expected. Accordingly, I will\ndispose of the first three items rather quickly and concentrate the rest of\nmy talk on the interrelations between geodetic progress and the accuracy\nachieved by the TRANSIT system program.\nProgress in oscillator stability from the beginning of the program to\ndate is summarized in Figs. 3 and 4. It will be seen that by 1974 we had\nachieved in the TIP II oscillator a satellite-borne crystal oscillator which,\nwith averaging times less than 1000 seconds, is actually better than a low\nnoise cesium standard. It will also be seen from Fig. 3 that the contribu-\ntion of the oscillator's stability to overall system error has remained\nessentially negligible compared to other sources of error throughout the\nhistory of the program.\nIonospheric refraction is a more complicated matter. First of all it is\na strong function of the frequency transmitted and goes down rapidly with\nincreasing frequency. However, the brute force solution of simply using a\nfrequency high enough to make ionospheric refraction negligible was not\navailable to us in the early 1960's when system decisions had to be made.\nIn the interest of satellite reliability we felt constrained to use fre-\nquencies achievable with solid state devices and at this date 400 MHz appeared\nas high as one could reasonably expect to achieve with long life amplifiers.\nHowever, the fact that the amount of refraction was strongly frequency depen-\ndent suggested a means of correcting for at least the first order of iono-\nspheric effect by transmitting not one but two coherent frequencies and\nmeasuring the ionospheric refraction by noting the difference in the Doppler\ngenerated. Accordingly from the beginning we planned on a pair of coherent\nfrequencies with a first order refraction correction and ultimately settled\non 150 MHz and 400 MHz as the operational pair. This proved very effective\nindeed and the remaining uncorrected ionospheric error is quite small. A\ncomplete discussion of this matter would require a paper of its own since\ntime of day, geographical location, total solar activity, and many other\nfactors are significant variables. Let me be content with indicating a few\ntypical values. Studies based on data from Austin, Texas in 1962, a time of\nsolar minimum, indicate that position errors due to high order uncorrected\nionospheric refraction effects with data below 10° discarded averaged about\n2.6 meters. Data again from Austin in 1969, a time of very high solar activity,\naveraged as much as 13 meters, again with a 10° data cut off.","7\nAt TRANSIT frequencies the tropospheric effect are very much smaller\nthan the ionospheric and for navigation is made even smaller by discarding\nextremely low elevation data. However, a great deal of work has been done on\ntropospheric refraction by Helen Hopfield of the Applied Physics Laboratory\nand this work is quite significant, precisely because the tropospheric effects\nare frequency independent. Thus by going to sufficiently short wave lengths,\ne.g., optical frequencies, the ionospheric effects can be virtually eliminated,\nbut the tropospheric effects are as big as ever and hence dominant. The next\npaper by Harold D. Black will discuss this matter further.\nAnd so we come to the primary subject of this paper which is the inter-\nrelationship between the geodetic progress and the accuracy of the TRANSIT\nsystem both for navigation and surveying. The interdependence of the TRANSIT\nsystem and the geodetic effect was recognized very early in the program. A\npaper1 I wrote in May 1961 contains the following paragraphs:\n\"The precision of measurement now possible with TRANSIT techniques is\nquite good. But both the determination of orbit during a 1-day period and\nthe ability to extrapolate the orbit for 1 day are presently limited (to a\nfew tenths of a mile in each case) by inaccuracies in the present model of\nthe force field (gravitational field, drag, etc.). On a worldwide basis,\nthere are further difficulties introduced by the unavailability of sufficient-\nly accurate datum ties.\n\"Meeting the ultimate program goals for TRANSIT thus requires consider-\nable improvement in the present knowledge of these factors (roughly the shape\nand mass distribution of the earth). This is the primary remaining develop-\nment challenge of the TRANSIT program.\n\"Fortunately, the TRANSIT system itself provides one of the most powerful\ntools available for accomplishing these goals. Furthermore, considerable\neffort using both TRANSIT and other techniques is planned, or already under-\nway, not only in the TRANSIT program, but by many other programs in the Army,\nNavy, Air Force, and NASA. It is clear that the next year or two will see\ntremendous advances in these basic problems of geodesy.\" \"\nThe first TRANSIT satellite to achieve orbit was TRANSIT 1-B launched\nin April 1960, into an orbit with an inclination of 51° and with a 470 mile\napogee and 230 mile perigee. It was quickly apparent that the behavior of\nthe orbit departed grossly from what could be expected for a satellite\norbiting an oblate spheroid. This is apparent in Figs. 5 and 6. In fact,\nas is seen in Fig. 5, the apogee radius from the center of the earth actually\nincreased substantially for approximately a month. In view of the large drag\nat perigee, which should have caused a resulting substantial decrease in\napogee radius, this was quite remarkable. With approximately two months\ntracking it was shown that both apogee and perigee did in fact decrease\nlinearly but had superimposed a sinusoidal oscillation whose period was\nprecisely the period of precession of perigee. In other words, the orbit\nbehaved quite differently depending on whether perigee occurred in the\nnorthern hemisphere or southern hemisphere and thus indicated a substantial\nnorth/south dissymmetry in the gravitational field of the earth. This fact\nwas recognized both by Dahlgren and by the Applied Physics Laboratory and","8\nwas quantitatively well explained by the inclusion of the odd zonal harmonic\nJ3 (the pear shaped term) whose existence had been announced2 by O'Keefe in\nDecember 1959 from long term tracking of Vanguard I. In fact, Cohen and\nAnderle of Dahlgren announced³ in 1960 the determination of a value of J3\nvery close to O'Keefe's value from one month of TRANSIT 1-B tracking data.\nThus the very first satellite to be successfully launched in the TRANSIT\nsystem demonstrated clearly the extreme power of the Doppler tracking tech-\nnique for developing important geodetic results. By the next spring, May\n1961, with the addition of TRANSIT 2-A data, Newton et al determined4 values\nfor J3, J5 and J7.\nIn the spring of 1961, TRANSIT 4-A was successfully placed in orbit\nand simultaneously tracking data became available from overseas stations,\nspecifically the TRANSIT station in England, This made possible for the first\ntime the examination of longitude dependent tracking errors. Fig. 7 shows\nthe along track error for TRANSIT 4-A on July 20, 1961, as a function of UT.\nThe very substantial sinusoidal variation in this tracking error is obvious\nand can only be explained by the assumption of a substantial ellipticity of\nthe earth's equator, with approximately 1000 ft. difference between the major\nand minor axis. The same conclusion, that the earth's equator was elliptical,\nhad been announced 5 in June 1961 by Imre Izsak of the Smithsonian Astro-\nphysical Laboratory based on optical observation of satellite orbits. This\nwas the first truly revolutionary result of the new science of satellite\ngeodesy since it had been an article of faith among American geodesists and\ngeophysicists that longitude dependent terms in the geoid were necessarily\nquite small.\nBy late 1962 TRANSIT tracking was based on a geoid containing all har-\nmonic coefficients through J4 and generally we were able to reduce tracking\nresiduals to the order of 100 meters. Then in 1963 TRANSIT 5BN-2 was success-\nfully orbited and a new phenomenon was observed. The along track error\nexhibited a very pronounced sinusoidal variation with an amplitude of about\n100 meters and a period of the order of 21/2 days (see the bottom curve on\nFig. 8). While it was still possible to obtain an orbit with tracking\nresiduals of the order of 100 meters over a period as long as 4 days, when\nused for navigation in the normal method envisioned for the operational\nTRANSIT system there was a serious amplification factor which created navi-\ngation errors as large as 400 to 500 meters. The reason for this can be\nseen in the top curve of Fig. 8. Operationally an orbit is determined for\nTRANSIT by taking the tracking data from a relatively brief period, for\nexample one day, and obtaining the best fit. This orbit is then predicted\ninto the future and this predicted orbit is inserted into a satellite and\nused by the navigator. If the fitting interval happens to correspond to a\nperiod when the satellite is \"running fast\" the departure of the prediction\nfrom the actual orbit is greatly exaggerated. A navigation based on a one\nday prediction can indeed be in error by 400 or 500 meters as shown by\nFig. 8. The explanation for the sinusoidal along track error was given by\nS. Yionoulis6 and was the first specific demonstration of the need to consider\nresonant geodetic terms. The problem stems from the existence of (for\nexample) 13th order longitude dependent geoid structure (J13) and its effect\non a satellite with a period of very nearly 1/13 of a day. By 1965 TRANSIT","9\norbits were based on a geoid with coefficients through Joe 8 and the 13th and\n14th order resonance terms. With this geoid tracking residuals with the\norder of 80 meters were obtained routinely. At about this time the record of\ngeodetic progress based on the TRANSIT system can no longer be followed in\npublic literature since a change in DOD policy made future results classified,\nalthough results obtained from NASA programs were still published in the open\nliterature.\nDuring 1968 a greatly expanded geoid with terms through J 15 15 was introduced\nand tracking residuals dropped to the order of 15 meters. In 1974 compensa-\ntion for polar motion was introduced and tracking residuals dropped to the\norder of 9 meters. Very recently the official WGS 1972 geodesy was adopted\nwith terms through T20 20 and tracking residuals dropped to about 6 meters.\nFig. 9 summarizes the history of tracking accuracy as a function of the\nincreasingly accurate geodesy on which the orbit determination was based.\nFrom the mid-1960's it was recognized that if advantage was taken of\nthe greatly increased accuracy achievable by tracking multiple passes at a\nfixed site that the TRANSIT system was capable of yielding results of survey\nquality and indeed since it was available globally and since the accuracy of\na fixed point determination was independent of distance of the point from any\npreviously observed site it provided the most accurate available method of\nremote site survey. The lower curve in Fig. 9 shows the accuracy with which\na fixed point can be determined on a global basis by averaging the order of\n50 TRANSIT passes.\nNormally for survey use one uses orbits determined after the fact, that\nis, orbits which use tracking data both before and after the time at which\nthe observation is made rather than the predicted orbit stored in the\nsatellite. However, a recent Canadian report states that they are achieving\n] meter accuracy for survey purposes using the stored (predicted) orbit from\nthe satellite. Figs. 10, 11, 12, 13 and 14 show typical bulls-eye plots of\nnavigation fixes using the stored (predicted) orbit in 1964, 1967, 1973,\n1974 and 1976. We've come a long way baby!","10\nReferences\n1. R. B. Kershner, \"TRANSIT Program Results\", Astronautics, May 1961\n2. J. A. O'Keefe and A. Eckels, Harvard Announcement Card, No. 1520\n(29 Dec. 1958); J. A. O'Keefe, A. Eckels, R. K. Squires, Science 129,\n565 (1959); Astron. J., 64, 245 (1959)\n3. C. J. Cohen and R. J. Anderle, \"Verification of Earth's \"Pear Shape\"\nGravitational Harmonic\" Science, 23 Sept. 1960\n4. R. R. Newton, H. S. Hopfield, R. C. Kline, \"Odd Harmonics of the Earth's\nGravitational Field\" Nature, 13 May 1961\n5. I. G. Izsak, \"A Determination of the Ellipticity of the Earth's\nEquator from the Motion of Two Satellites\", Astrophys. J. , 66, p. 226,\n1961\n6. S. M. Yionoulis, \"A Study of the Resonance Effects Due to the Earth's\nPotential Function\", J. Geophys. Res. Vol. 70, No. 24, 1965, Vol. 71,\nNo. 4, 1966","NAVY NAVIGATION SATELLITE SYSTEM\nLONGITUDE\nDATA PROCESSOR\nTIME\nCOMPUTER\nLATITUDE\nTIME T3\nORBITAL PARAMETERS\nRECEIVER\nDOPPLER SIGNAL\nNAVIGATOR\n(HIGH ACCURACY)\nTIME\nTRACKING\nSTATION\nCORRECTION\nOBSERVATORY\nTIME\nTIME (UT-2)\nTIME\nNAVAL\nORBITAL\nPARAMETERS\nNEW\nTRACKING\nSTATION\nINJECTION STATION\nTRANSMITS NEW ORBITAL\nCONTROL\nPARAMETERS & TIME\nDOPPLER DATA\nCORRECTION (UT-1)\nCENTER\nREFRACTION\nCORRECTED\nCOMPUTING CENTER\nTIME T1\nORBITAL PARAMETERS\n& TIME CORRECTION\nSIGNALS\nDOPPLER\nCOMPUTES FUTURE\nDIGITALIZES DOPPLER\nRECEIVES RECORDS &\nTRACKING\nSTATION\nSIGNALS","12\nRELIABILITY\nSATELLITE\nJULY 1976\n(SYSTEM)\n99.9701 %\n99.9884%\n99.9591%\n99.9925%\n99.9508%\n99.9776%\nSATELLITE CONSTELLATION\n11 HRS. 34 MINS\n9 HRS 28 MINS\n32 HRS 55 MINS\n93 HRS 51 MINS\n38 HRS 6 MINS\n31 OCT. '68\n26 APR. '75\n1 HR 48 MINS\n29 APR. '76\n27 FEB. '76\nSERVICE\n1 JUL. '73\nOUT OF\nTIME\nFIG. 2\nSERVICE\n111 MOS.\n110 MOS.\n106 MOS.\n71 MOS.\n33 MOS.\n431 MOS.\nTIME\nIN\n18 MAY. '67\n14 APR. '67\n27 AUG. '70\n29 OCT. '73\n25 SEP. '67\nLAUNCH\nDATE\nSATELLITE\n30120\n30130\n30140\n30190\n30200\nNO.","13\n72\n00\n01","14\n5 YEARS\n108\n1 YEAR\nSUMMARY OF OSCILLATOR PERFORMANCE\n107\nLOW NOISE CESIUM\n106\nAVERAGING TIMES (SECONDS)\n1 DAY\n105\n0-13\nFIG. 4\n104\n5E OVEN-2.5 MHz 5th OVERTONE\nSULZER DOUBLE OVEN 2.5 MHz\n10³\n5th OVERTONE\nASSOCIATION\n102\n101\n10°\n10-12.\n10-14\n10-15\n10-9\n10-10\n10-11\n10-13\n10-8\nAf\nf","15\nSEPT 1960\n1080\n1020\n960\n900\n840\n780\nSATELLITE REVOLUTIONS, n\n720\nCOMPUTED: RA = 7131.79-0.01505n + 6.03 sin 0.004079 (n - 314)\nAPOGEE RADIUS FROM CENTER OF EARTH\n660\n600\nTRANSIT IB ORBIT\nFIG. 5\n540\n480\n420\n360\n300\n240\nOBSERVED\n180\n120\n60\no\n7129\n7128\n7127\n7126\n7125\n7124\n7123\n7122\n7121\n7120\n7119\n7118\n7117","SEPT 1960\n1080\n1020\nCOMPUTED : Rp = 6745.57 - 0.00297 n + 5.41 sin 0.004079 (n + 456)\n960\nPERIGEE RADIUS FROM CENTER OF EARTH\n900\n840\nTRANSIT IB ORBIT\nSATELLITE REVOLUTIONS, n\n780\n720\n660\nFIG. 6\n600\n540\n480\n420\n. OBSERVED\n360\n300\n240\n180\n120\n60\no\n6750\n6749\n6747\n6748\n6746\n6745\n6740\n6739\n6744\n6743\n6742\n6741\n6738","17\n-------\n24\nTRANSIT 4A, ALONG-TRACK ERROR AS A FUNCTION OF UT FOR\n18\n20 JULY 1961\nHOURS UT\nFIG. 7\n12\n6\n:\n0\n2\n1\n0\n-1\n-2\n10\nx\nSAVIONA\nT","18\n122\n009\n00€\n0\n00E-\n009-\n009\n0\n00€\n00E-\n009-","3.5 GEODESY (THRU J8 PLUS 13th AND 14th ORDER RESONANCE)\nWGS-72 GEODESY\n(THRU20)\n20\nPOLAR MOTION\nCOMPENSATION\nTRACKING ACCURACY HISTORY OF TRANSIT\n75\n74\n73\n4.5 GEODESY\n(THRU J 15)\n15\n72\n71\n8\n70\n1st ORDER IONOSPHERIC CORRECTION\nFIG. 9\n69\n1.0 GEODESY (THRU J4)\n4\n68\n67\nLOW ORDER ZONAL AND\nYEAR 19\n66\nOTHER MODEL\nREFINEMENTS\n65\n(MINIMUM 50 PASSES\nFIXED SITE SURVEY\n64\nACCURACY\nASSUMED)\n63\nOPERATIONAL\n62\nSYSTEM\n61\n60\n59\n10\n100\n1.0\n1000","20\n.2\n0\n4\n-.2\n0\n.2\n.4\nLONG\nMK-X1 1984 ALL SATELLITES\nFIG. 10\nJUDSON BIGELOW INC.\nNO. 02","21\nLAT\nSHE\n05\n0\n05\n1\n= 05\n0\n05\n1\nLONG\nMK-K3 1267 ALL CATELLITES DATS 001-120\nFIG. 11","IG.--------\n22\n0.10\n0.05\nFIX RESULTS AT STATION 110\nDecember 1973\nLONG (NM)\n12\n0.00\n-0.05\n-0.10\n0.10\n0.05\n0.00\n-0.05\n-0.10","23\n0.10\n0.05\nFIX RESULTS AT STATION 110\nMarch 1974\nLONG(NM)\nFIG. 13\n0.00\n-0.05\n-0.10\n-0.05\n0.05\n0.00\n0.10","-----------\n0.10\nFIX RESULTS AT STATION 110 FOR PERIOD\n0.05\n1 Jan. - 30 Jun 76\nLONG (NM)\nFIG. 14\n0.00\n-0.05\n-0.10\n0.00\n-0.05\n0.05\n0.10\n-0.10","25\nPOSITION DETERMINATION USING\nTHE TRANSIT SYSTEM\nHarold D. Black\nThe Johns Hopkins University\nApplied Physics Laboratory\nJohns Hopkins Road\nLaurel, Maryland 20810\nAbstract\nMeasuring the 3-dimensional coordinates of a\npoint on the Earth's surface has always been difficult.\nWithin the last 10 years, it has become appreciably easier\nand more precise. Today, measuring the 3-dimensional\ncoordinates of a point in a globally-applicable coordi-\nnate system is a routine, commercially-available service\nprovided we are content with accuracies of about 1:106\nand precisions of about 1 meter.\nSomewhat ironically, these results are obtained\nusing a navigation system. In the correct sense, however,\nthis is possible only as a result of careful and deliberate\ndesign.\nThe use of the Navy Navigation Satellite System\n(\"Transit\") in position determination is described\ntogether with recent results and improvements.\nAn easily-implemented algorithm for removing\ntropospheric-refraction biases is given and the effects\nof removing these biases experimentally demonstrated.","26\nIntroduction\nAt the onset I would like to distinguish\nbetween:\na) \"Navigation\" and \"Surveying\".\nI will reserve \"navigation\" for positioning\nof a moving vehicle (ship) and \"surveying\" for posi-\ntioning of an earth-fixed point.\nb) \"Precision\" and \"Accuracy\".\nPrecision is a measure of the internal consis-\ntency of a set of numbers. Accuracy is a more stringent\nrequirement and requires comparison of a given measure-\nment with an absolute standard. The precision of this\nsystem (any system) is easy to certify simply by making\nrepeated measurements. The accuracy is a much more\ndifficult question and first requires agreement on the\ndefinition of an absolute standard and then comparison\nwith this standard.\nThe Transit System has been repeatedly described\n[Guier and Weiffenbach, 1960; Kershner and Newton, 1962;\nKershner, 1965] and it would be extremely redundant to\nrepeat those descriptions here. It suffices to say that\na long survey article is to be published in a forthcoming\nissue of Navigation, The Journal of the Institute of\nNavigation. The more recent improvements in the system\nwere a) corrections for polar motion (introduced in\nJanuary 1974) , b) a change of geopotential models from\nAPL 4.5 [Black, 1968] to WGS-72 [Seppelin, 1974] in\nDecember 1975 [Space Department Staff, 1975-76]. This\nlast reference contains a current error budget for the\nnavigation solution.","27\nCorrelated Error Sources\nEffects of a Removing Polar Motion\nFor a long time we tolerated the 5-10 m biases\ndue to polar motion. We tolerated them because: we did\nnot know how to remove them without requiring that all\nnavigators change their software.\nErrors this \"small\" are usually unimportant\nto navigators. Errors this \"large\" are very important\nto surveyors. Unless the surveyor repeatedly visited\nthe site over a period of a year, he would be unaware\nof the existence of this error. He would position the\nsite with respect to a slowly changing coordinate system\nand his usual measures of \"accuracy\" would not detect\nthe bias; his precision-measures (scatter) would tell\nhim nothing of its existence [see Pisacane, et al., , 1973\nfor an experiment describing the net effects of uncor-\nrected polar motion on the navigation solution].\nWe were able to remove this error source --\nor rather reduce it down to the 1 meter level -- without\nrequiring users to alter their equipment (or software)\nin any way. \"Dramatic\" proof that we successfully re-\nmoved the polar motion effect was provided by the quality\ncontrol computations -- if you knew when to look for\nit (see Fig. 1) One meter seems to be about the error\nlevel in the known coordinates of the instantaneous pole\n[Beuglass and Anderle, 1972]. The pole of the earth-\nfixed coordinate system associated with the fix is called\nthe \"C.I.O. \" [Conventional International Origin; Mueller,\n1969] -- or in France, the O.C.I.\nEffects of an Improved Geopotential Model on Surveyed Position\nThe accuracy of the satellite ephemeris is\nstrongly influenced by the data distribution (in time\nand space), the data precision, and the accuracy of the\n*\nThe Earth's pole is not fixed in the Earth but moves\nabout 10 meters every 12-14 months [Pisacane, et al. ,\n1973] .","28\nSAT 30130\nPOLAR MOTION\nCOMPUTATION\n30\nBEGAN\n20\n10\n280\n320\n360\n400\n440\n480\n520\nDAY 1973\nFIG. 1 Position Effect of Introducing Polar Motion Computation on Satellite\nUncertainty","29\ngeopotential model. Improvements in the geopotential\nmodel have, until now, resulted in appreciable improve-\nments in the overall system precision [Kershner, 1976].\nThe most recent change, in December 1975, provides an\nexample of this improvement; cf. Figs. 2 and 3:\nWe changed from a 15th order geopotential\nmodel to a 20th order model. According to Kaula's rule-\nof-thumb (Fig. 4), this reduced the rms uncertainty in\nthe satellite position from 15-20 m to 4-6 m, (see Fig.\n4.5 for the actual results). It is clear from Fig. 4,\nhowever, that future improvements from this source will\nbe by previous standards relatively small; we are beyond\nthe point of diminishing returns.\nThe geodesy (geopotential) errors are corre-\nlated errors and, consequently, obtaining higher internal\nconsistency within the global datum required that some\npositions change as the geopotential model is improved.\nWe believe that the recent change has disturbed very few\nusers of the Transit System. We had thought -- simulation\nhad indicated -- that the 1975 change in geopotential\nmodel would change all stations by less than 5 m. We\nwere correct only in a global (rms) sense: There is one\narea in the middle of the Indian Ocean where shifts as\nlarge as 15 m occurred [Holland, et al. 1976]. Over\nthe Earth the rms shift in surveyed position was about\n5 m. If it is ever desirable to change geopotential\nmodels and/or tracking station coordinates again, then\nthe implied positional changes will be of-the-order-of\na meter or two. This is one of the reasons why we hesi-\ntate to claim an accuracy of 1 m for the system.\nDrag and Radiation Pressure Biases\nFor surveyors using the NNSS, the largest source\nof single-pass position error are drag and radiation pres-\nsure biases: the drag and radiation pressure forces acting\non the satellite are difficult ones to model. Drag in parti-\ncular has a strong weather-like characteristic [Eisner, 1967;\nKing-Hele, 1975]. Moreover, drag, unlike radiation pressure\ncauses a secular error in the satellite along-track error.","30\n60\nAPL 4.5 Geopotential model\n40\n20\n(u)\n0-\n-40\n-60\n45 PASSES\n(ALL SATELLITES)\na LAT 32m\n-80\na LONG 29m\nD = 264-277, 1975\n-100\n-80\n-60\n-40\n-20\n0\n20\n40\n60\n80\nLONG (m)\nJHU/APL\n7/76\nFIG.\n2 Transit System Navigation Results September 1975\n60-\nWGS-72 Geopotential model\n40\n20\n-\n(m)\n0-\nLAT\n-40\n-60\nRCVR - WRN - 5\n48/52 PASSES\noLAT = 17m\n-80-\noLONG = 18m\nFEB 10-25, 1976\n-100\n-80\n-60\n-40\n-20\n0\n20\n40\n60\n80\nLONG (m)\nJHU/APL\n6/16/76\nFIG. 3 Transit System Navigation Results February 1976","31\n100\n80\n60\n40\n20\n10\n8\n6\n4\n2\n8\n10\n12\n14\n16\n18\n20\nSatellite the Geopotential at Position 1100 Coefficients km Error Caused at by Truncating 22\nDegree n\nSatellite\nDegree\nn,\nAltitude\nFIG.\n4","32\nSAT 30130\nWGS-72 IMPLEMENTED\n30\n20\n10\n0\n235\n275\n315\n355\n395\n435\n475\nDAY 1975\nFIG. 4.5 Effect of Introducing WGS-72 Geopotential Model\non the RMS Satellite Position","33\nOn the other hand, the satellite altitude was\nspecified (1100 km) so that the drag force is typically\nseveral orders of magnitude less than the radiation\npressure. Radiation pressure computation also has its\nproblems [Ebert, 1973]; the force is discontinuous in\ntime, requires detailed knowledge of the satellite sur-\nface (emissivity/absorptivity) properties, and satellite\norientation control.\nThe most important consequence of this uncer-\ntainty is that a period error is embedded in \"tracked\ninto\") the satellite initial conditions. In the pre-\ndicted ephemerides, which are required by the operational\nsystem, a linearly increasing along-track error is a\ndirect consequence. This error, in turn, causes a lati-\ntude error which changes sign with the direction of\nsatellite motion; of one sign when the satellite is\ntraveling north-to-south and another when traveling\nthe opposite direction. The surveyor should then attempt\nto include equal numbers of north-going and south-going\npasses in his final position determination.\n\"And now\nfor the good news\" The system is carefully managed\nto control this (and other) error sources. The frequency\nwith which the orbit specification is regenerated is\nquite important here. Figs. 5, 6, and 7 show the slope\nof the along-track error growth for satellites 30130,\n30140, and 30190. It is typically true that the along-\ntrack error growth rate is about 1-2 meters per satellite\nperiod. The improvement in the system that came with\nthe introduction of WGS-72 is clearly evident. We have\nno explanation of the different character of the error\nas seen in the different satellites. It could be (as a\nguess) a consequence of the different attitude behavior\nof the satellites as the orbit planes occupy different\npositions relative to the sun. We checked a 48-pass data\nsample to see if we could detect any secular increase\nin the latitude error with elapsed time; time since the\norbit had been regenerated. Fig. 8 shows the result of\nthe experiment; the (absolute value of the) latitude error\nas a function of time since the orbit was regenerated.\nIf there is any secular change it is in the noise of the\nfix determination -- and this is where it is intended to\nbe. We utilized all satellites in the experiment.","34\nSAT 30130\n4\n3\n2\n1\n0\n-1\n-2\n-3\n-4\n-130\n-90\n-50\n-10\n30\n70\n110\nDAY 1976\nFIG. 5 Slope of the Along Track Error\nSAT 30140\n4\n3\n2\n1\n0\n-1\n-2\n-3\n-4\n-130\n-90\n-50\n-10\n30\n70\n110\nDAY 1976\nFIG. 6 Slope of the Along Track Error\nSAT 30190\n3\n2\n1\n0\n-1\n-2\n-3\n-130\n-90\n-50\n-10\n30\n70\n110\nDAY 1976\nFIG. 7 Slope of the Along Track Error","35\n200\n150\n100\n50\n0\n0\n1000\n2000\n3000\n4000\nFIG. 8 Time Elapsed Since Orbit Regeneration (sec)","36\nTropospheric Refraction*\nAt current levels of surveying precision, the\n(totally) uncorrected tropospheric effects would be an\nunconscionable source of error -- about 20-25 meters\nmostly in longitude. The tropospheric effect manifests\nitself as an error in the instantaneous range from the\nobserver to the satellite. Typical values of this error\nare shown in Fig. 9. The error is largest at low eleva-\ntion angles; typically 80 meters for a satellite on the\nobserver's horizon and about 2.3 meters (instantaneously)\nwhen directly overhead.\nAt very low elevation angles (below 5°), the\nphysical effects are more complicated than we have\nrepresented here: The bending of the rays for example\ncontributes (subtracts) 3 meters at 1° [Hopfield, 1976].\nWe do not recommend that data below 5° be used.\nFor data above, we have recently found a precise\neasily-computed form (for the tropospheric refraction\nrange effect) based on the Hopfield quartic model of tropo-\nspheric refractivity [Hopfield, 1969, 1971]:\n(1)\nAs = Asd + As W\nwherein\nT - 3.96\nI (h=hare)\n(2)\n= 2.343\nP\n.\nT\n(3)\nAs = k W I (h=h w/e)\n-1/2\n2\ncos e\nI (h,e) =\n1 -\n(4)\n1 + (1-lc)/(rs/h)\n*My understanding of this problem is almost totally due\nto Helen Hopfield.","37\n100\n0°C\n80\nINTERES\n60\nST\n40\n20\n0\n0\n20\nELEVATION ANGLE (DEG) 60\n40\n80\nFIG. 9 Tropospheric Range Effect","38\nha = 148.98 (T-3.96) meters above the station\nh\n= 13,000 meters\nW\nl C\n0.85\n=\n0.28\n-- Summer in tropics or mid-latitudes\n0.20 -- Spring or Fall in mid-latitudes\nk\n0.12 Winter in maritime mid-latitudes\n=\nW\n0.06 Winter in continental mid-latitudes\n0.05\npolar regions\nAsd' AS are the dry atmosphere and humid (wet) atmos-\npheric contributions to the tropospheric range correction.\nAS should be added to the straight-line (geometric)\ndistance so that the sum will correspond to the elec-\ntromagnetically measured distance. As is given in meters.\nT is the surface temperature in degrees Kelvin. P is\nthe surface pressure in standard atmospheres (1 atm =\n1013.25 mb = 14.696 psi). r s is the distance from the\ncenter of the Earth to the station antenna. e is the\nelevation angle.\nThe function I varies from unity at e = 90°\nto about 10 at e = 5°; a single precision computation\nof I suffices quite nicely. The term (T-3.96) /T can\nbe replaced with 0.986 since it changes at most + 0.2%.\nThe principal temperature dependence enters via ha.\nAn 80°C drop in temperature (from 40°C to -40°C)\nincreases AS about 0.5 meter at the lowest elevation\nangles and leaves As unchanged at the highest elevation\nangles. Only then for the most precise work, is it\nnecessary to measure the temperature, and even in these\ninstances, a crude estimate (+ 5°C) suffices.\nIn many practical applications the pressure\ncan be treated as a constant: For stations at sea level,\na severe tropical storm is required to decrease P to 0.93\n[Climatological Data, 1974]. The surface pressure will","39\nof course change with the height of the station above sea\nlevel. For example, at Quito, Ecuador, 2812 meters above\nsea level, the pressure is typically 0.72 atm. For precise\nwork, the pressure should be measured with a precision of\n1/2% to keep the associated range error below 10 cm.\nTo check the validity of the above equations,\nwe implemented them in a navigation program and navigated\n48 passes of data acquired at the doppler sites on days\n268-269, 1970 from satellite 30140. Since neither the\npressure nor temperature measurements were available we\nrelied on the inflexibility of Eqs. 1-4 and simply assumed\nthat the temperature at all sites is 15°C, the pressure is\n1 atm, and kw = 0.2. The following locations were repre-\nsented in the data:\nAlaska\nMaryland\nEngland\nMaine\nJapan\nMinnesota\nNew Mexico\nCalifornia\nSamoa\nHawaii\nOnly passes having maximum elevation angles lying between\n15° and 80° were included. We navigated the data three\ndifferent ways (all three utilized the identical satellite\nephemeris) :\nFirst:\nwith no tropospheric correction\nSecond:\nwith the model we have just described\nThird:\nwith the Yionoulis implementation\nof the Hopfield model [Yionoulis, 1970]\nResults from these three are shown in Figs. 10, 11, and 12.\nThe second and third sets are essentially the\nsame.\nThe advantages of including the tropospheric\ncorrection -- even in a navigation solution -- are clearly\napparent. In precise surveying, tropospheric range cor-\nrection is mandatory.","40\n(NO TROPOSPHERIC CORRECTION)\n40\n20\n(un)\n0\n-20\n-40\n-100\n-80\n-60\n-40\n-20\n0\n20\n40\n60\n80\n100\nLONGITUDE (m)\nFIG. 10 Fixed Site Navigation","41\nCORRECTED FOR TROPOSPHERIC\nEFFECTS USING EQS. 1 TO 4 OF TEXT\n40\nSAT 30140\n268/269 1970\n20\n(m\n0\n-20\n-40\n-20\n-100\n-80\n-60\n-40\n0\n20\n40\n60\n80\n100\nLONGITUDE (m)\nFIG. 11 Fixed Site Navigation","42\n(WITH TROPOSPHERIC CORRECTION)\n40\n20\n(m)\n0\n-20\n-40\n-100\n-80\n-60\n-40\n-20\n0\n20\n40\n60\n80\n100\nLONGITUDE (m)\nFIG. 12 Fixed Site Navigation","43\nAs a final note; tropospheric corrections\nhave been included from the beginning in the Transit\norbit generation and updating computation.\nAn overriding consideration throughout the\ndevelopment of the Transit System has been to make it\nas precise as is technically possible with the hope\nthat it would become the primary standard of accuracy\nfor surveying on a global scale.\nAcknowledgment\nI am indebted to:\n1. Helen Hopfield and Arie Eisner for help in\npreparing this paper.\n2. The U. S. Navy Astronautics Group, the\noperating agency of the Transit System, for supplying\nsome of the quality control statistics on the system\nperformance.\nReferences\nBeuglass, L. K. and Anderle, R. J. \"Refined Doppler\nSatellite Determination of the Earth's Polar Motion, \"\npublished in Henriksen, S. W. , et al., eds; The\nUse of Artificial Satellites for Geodesy, Monograph\nNo. 15, American Geophysical Union, Washington, D.C.,\np. 181 et seq., 1972.\nBlack, H. D. , Doppler Tracking of Near-Earth Satellites,\nJHU/APL Report TG-1031, 1968.\nClimatological Data, U. S. Dept. of Commerce, NOAA,\nEnvironmental Data Service, Annual, Vol. 25, No. 13,\np. 87, 1974.\nEisner, A., Atmospheric Density Studies, JHU/APL Report\nTG-951, 1967.\nEbert, W. L. , Errors in the Ephemerides of Satellites\nCaused by Numerical Integration, JHU/APL TG-1233,\n1973.\nGuier, W. H. , and Weiffenbach, G. C. A Satellite\nDoppler Navigation System, Proceedings of IRE,\nVol. 48, pp. 407-516, 1960.","44\nHolland, B. B. , Eisner, A., , and Yionoulis, S. M., \"The\nEffect of WGS-72 Geopotential in NNSS on Station\nSurveys,\" for possible presentation at the AGU Fall\nAnnual Meeting in December 1976.\nHopfield, H. S. , \"Two-Quartic Tropospheric Refractivity\nProfile for Correcting Satellite Data, \" J. of Geophys.\nRes. , Vol. 74, No. 18, pp. 4487-4499, 1969.\nHopfield, H. S. , \"Tropospheric Effect on Electromagneti-\ncally Measured Range: Prediction from Surface\nWeather Data,\" Radio Science, Vol. 6, pp. 357-367,\n1971.\nHopfield, H. S., Tropospheric Effects on Signals at Very\nLow Elevation Angles, JHU/APL Report TG-1291,\nMarch 1976.\nKershner, R. B. , and Newton, R. R. \"The Transit System,\" \"\nJournal of the Institute of Navigation, Vol. 15,\npp. 129-144, 1962.\nKershner, R. B. \"Present State of Navigation by Doppler\nMeasurement from Near-Earth Satellites, APL Technical\nDigest, Vol. 5, No. 2, pp. 2-9, 1965.\nKershner, R. B. , \"The Doppler Concept and the Operational\nNavy Navigation System,\" to be presented at the\nInternational Geodetic Symposium on Satellite Doppler\nPositioning, October 12-14, 1976 in Las Cruces, New\nMexico.\nKing-Hele, D. G., \"A View of Earth and Air, The Bakerian\nLecture, 1974, Philos. Trans. of the Royal Society\nA, Vol. 278, No. 1277, pp. 67-109, 6 March 1975.\nMueller, Ivan I., Spherical and Practical Astronomy as\nApplied to Geodesy, Frederick Ungar Publishing Co.,\nNew York, 1969.\nPisacane, V. L., Holland, B. B. and Black, H. D. \"Recent\n(1973) Improvements in the Navy Navigation Satellite\nSystem,\" NAVIGATION, Journal of the Institute of\nNavigation, Vol. 20, No. 3, pp. 224-229, Fall 1973.\nSeppelin, Thomas O., \"The Department of Defense World\nGeodetic System 1972,\" The Canadian Surveyor,\nVol. 28, No. 5, pp. 496-506, December 1974.","45\nStaff of the Space Analysis and Computation Group,\nJHU/APL, \"Planned Improvements in the Transit\nSystem (1975), \" NAVIGATION, Journal of the Institute\nof Navigation, Vol. 22, No. 4, pp. 352-360, Winter\n1975-76.\nYionoulis, S. M., \"Algorithm to Compute Tropospheric\nRefraction Effects on Range Measurements,\" J. of\nGeophys. Res. , Vol. 75, p. 7636, 1970.","46","47\nPOINT POSITIONING CONCEPT\nUSING PRECISE EPHEMERIS\nR. J. Anderle\nNaval Surface Weapons Center\nDahlgren, Virginia\nIntroduction\nPrecise ephemerides for one or more Navy Navigation Satellites are\ncomputed on alternate days based on 48 hours of observations made at\nOver 20 stations distributed around the world. During some periods,\ndata from a number of stations in addition to those shown on Figure 1\nmay be utilized, or one or two of those shown may not be operating.\nThe four stations providing data for use in computing the orbit\ninjected into the operational system are shown by the symbol (x) on\nthe figure. The operational ephemeris differs from the refined\nephemeris in: (1) it is available in real time, (2) it is predicted\nrather than a post fitted ephemeris , (3) it is based on data from\nfour rather than twenty stations, (4) certain variations in the\nmathematical model, (5) the truncation error in the predicted ephemeris,\nand (6) the timeliness with which improvements in the mathematical\nmodel are adopted. The differences in the mathematical model have\nprobably been below two meters since November 1975. The remaining\neffects probably reach 10 meters, a portion of which would be averaged\nout in computing the positions of stations on the basis of data ob-\ntained from multiple satellite passes.\nBoth the fitted operational and the refined \"long-arc\" ephemerides\nhave root mean square errors of about 2 meters due to uncertainties\nin the drag and gravity model, a portion of which is probably averaged\nout in solutions based on multiple satellite passes. A way of re-\nmoving these errors is to use short spans of data in the orbit fit\nsuch as in the short arc, translocation, or similar modes of computation.\nHowever, the gain in mathematical accuracy and possible gain in speed\nof field operations (if more satellites are used) must be balanced against\nthe losses due to: (1) loss of strength of solution due to use of\nfewer stations to compute the equivalent of the reference orbit, (2)\ngeometric weaknesses of certain station configurations, (3) pro-\npagation of error if extensions of the net are required, and (4)\nadditional cost due to additional stations.\nThis report on the determination of the positions of stations using\nthe precise ephemeris discusses first the method used to compute the\nprecise ephemeris and then the method of positioning the stations on\nthe basis of that ephemeris. Details of the computations are also\ngiven by Anderle (1974), O'Toole (in press), and Beuglass (1975).","48\nRefined Ephemeris\nMathematical Model\nThe equations of motion of the satellite and variational equations\nfor the forces are numerically integrated by a tenth order Cowell\nprocess with UTC time as the argument of the integration. The inte-\ngration is carried out in an inertial reference frame fixed by the\nmean equator and equinox of 1950.0, and the gravitational field of\nthe earth is rotated to the true equator and right ascension at each\nintegration step. Residuals of observation are formed in the inertial\nframe after rotating the station position through precession, nutation\nand hour angle and through the correction from the CIO pole to the\ninstantaneous pole. Constants for the precession and nutation terms in\nthe transformation are taken from the American Ephemeris and Nautical\nAlmanac. The (UTC-UTl) correction is an extrapolation based on the\npreceding week of data from the U. S. Naval Observatory since the ab-\nsolute origin for the right ascension of the satellite is of no\nconsequence in the final computed station positions provided that earth-\nfixed satellite positions are used. The pole position components are\nfound as parameters of the solution.\nEquations of Motion\nThe force equation includes terms for the gravitational field of\nthe earth, moon and sun, the lunar and solar solid earth tide effects,\natmospheric drag, and solar radiation pressure. The gravitational\nfield of the earth is given in a spherical harmonic expansion con-\ntaining about 400 terms, and earth tides are based on a Love's number\nof 0.26, where these constants were found in general geodetic solutions\nfor over a thousand parameters based on over a year's worth of data\ndistributed amoung about a dozen satellites. The gravity field used\nin the computations was revised at the following times in recent years:\n20 February 1967\nNWL-8D\n18 April\n1968\nNWL-8H\n13 Feb\n1970\nNWL-9B\n2 Jan\n1973\nNWL-10E\nDifferences in satellite position computed with these various fields\nare typically about 5 meters where the highest frequency is the\ndifferences corresponding to the orbit period. The atmospheric density\nis given in an exponential form with altitude, and a scale factor for\nthe drag is obtained as a parameter of each solution. Solar radiation\npressure is calculated in the cone angle formed by the sun and the\nearth, and the scale factor for the radiation was found in least squares\nfits to several weeks of observation of Navigation Satellites.","49\nObservation Equation\nData obtained by the four navigation stations have traditionally\nbeen converted to frequency in forming the observation equations. These\nstations determine the time to count a pre -set number of beat cycles\nbetween the received frequency and the ground station reference\nfrequency, and the number of cycles counted is set SO that the count\nlasts a little under one second. The computed frequency is associated\nwith the time midway through the count. Data from all other stations\nis converted to a range difference over the time interval between the\nstart and end of the count. The use of range difference avoids the\nnecessity of corrections for non-linear frequency changes which would\nbe required for long count intervals. Tropospheric refraction cor-\nrections are based on the model given by Hopfield (1973). Classical\nsecond order Doppler corrections and time transmission corrections are\nmade.\nThe Doppler and range difference observations within a pass are\nweighted by the reciprocal square of the standard deviation of the\nfiltered residuals from an orbit best fitting the data for the individual\npass (that is, for filtering purposes a solution is made for the bias\nparameters and the well determined orbit constants which best fit\neach satellite pass, where the number of well determined orbit constants\nin a local reference frame is determined automatically in a pass by\npass basis) The \"observation\" of the nominal scale factor of unity\nfor the tropospheric refraction is weighted by 100, corresponding to\na 10% uncertainty in refraction. Other a-priori data, such as\nfrequency bias, orbit constants, drag scaling factor, and positions of\nnew stations are given very low weight so that they are essentially\nfree parameters.\nCoordinates of base stations have been changed at the following\ntimes in recent years:\n20 February 1967\nNWL-8E\n19 January 1968\nNWL-8F\n20 December 1970\nNWL-9C\n18 October 1971\nNWL-9D\nThe NWL-8E coordinates were found in a general solution for geodetic\nparameters based on over a year's data distributed among seven\nsatellites. The NWL-8F coordinates were obtained by transforming the\nNWL-8E coordinates from the mean pole of 1966.7 to the CIO pole. The\nNWL-9C coordinates were found in a solution based on 40 days of data\nin 1970 holding the pole fixed at preliminary BIH values (Beuglass\nand Anderle) ; the differences of the NWL-9C coordinates from the NWL-8F\ncoordinates were about 3m. The NWL-9D coordinates revised the heights\nof three of the stations.","50\nParameters of the Solution\nA summary of the parameters of the solution for the refined\nephemeris based on two days of observation is:\n6 Constants of Integration\n1 Drag Scaling Factor\n2 Components of Pole Position\n1 Frequency Bias for Each Satellite Pass\n1 Refraction Bias for Each Satellite Pass\n3 Components of Station Position for any station\nfor which precise coordinates have not been determined\nThe total number of parameters is therefore 9+2N S for N passes\np\n(about 200) and N S new stations (0 to 5). The program used for this\nsolution has the capability of also including as unknowns (UTC-UTl)\n(which is singular), the time rate of change of (UTC-UTl) (which is\nless than the effects of systematic errors in the solution, solar\nradiation pressure constant (which is better determined from longer\ndata spans, and relatively constant), three components of average thrust\non a given schedule (which is not needed for precise ephemerides)\n,\nfrequency drift for each pass (which is not needed for refined\nephemerides) , three components of position of each station and 10 to\n20 gravity coefficients. The components of position of each station\ncould be introduced as unknowns with 2m uncertainty for the a-priori\nvalues to improve the weighting of the data for each pass and the\ncovariance of the solution or the gravity coefficients could be in-\ntroduced as unknowns with appropriate uncertainty for the a-priori\nvalues to improve the weighting, covariance and fit; however, it is\njudged at this time that the gain to be obtained would not offset the\nloss due to the complexity introduced into the problem of identifying\nmalfunctions of equipment or input errors.\nFuture Changes\nNo changes are contemplated in the gravity field in the near\nfuture, although the problem is under periodic review. A revision of\nthe station coordinates of about two meters is anticipated in 1976\nto improve the consistency of the data as determined by review of\ndata over the past several years (Anderle, 1975). The desirability of\nintroducing additional station coordinate or gravity coefficient\nparameters will be reviewed periodically in the event that some new\nfactor would change the current decision. As time permits, (1)\nbetter values will be introduced for the precession and nutation con-\nstants and the lunar solar ephemeris, (2) earth's albedo, atmospheric,\nand ocean tidal effects will be added to the force field, and (3)\ntidal effects on station position will be added. Since these effects\nvary from 1 to 50 cm, they will not have a major impact on accuracy,\nbut in aggregate, or with other improvements, they should be of some","51\nbenefit. Experiments with observations of the TIP (drag compensating)\nnavigation satellites may show that increased accuracy will be achieved\ndue to the elimination of effects of at least the fluctuations in\natmospheric drag; alternatively, drag compensation may permit the com-\nputation of pole position at shorter intervals of time.\nPoint Positioning\nThe mathematical model for point positioning varies from agency to\nagency and even within an agency. All solutions for positions made\noperationally by U.S. Government agencies to date have been based on\nthe assumption that the satellite orbit is perfect and includes as\nfree parameters the three components of station position and a frequency\nbias for each pass. Refraction bias may or may not be a parameter for\neach pass according to the custom of the agency. All computations of\nposition of Geoceiver, JMR, and Marconi equipment performed by the Naval\nSurface Weapons Center have included a refraction bias parameter,\nwhere the standard atmosphere is given a weight corresponding to a 10%\nuncertainty. The program used by the Naval Surface Weapons Center\nto compute the positions of CCID and Doppler equipment did not include\na refraction bias parameter until 1 January 1976, despite the fact that\norbit computations based on these data did consider such a parameter as\ndescribed in the previous section. The remainder of the mathematical\nmodel is consistent with that described for the computation of the\nrefined ephemeris, except that the observational equations are usually\nformed in the earth-fixed reference frame since this is the preferred\nframe for producing the refined ephemeris (to avoid the confusion\narising from the approximate UTC-UT1 correction used in computing the\nrefined ephemeris). .\nA good case can be made for including the orbit constants as para-\nmeters for each pass, weighting the a-priori constants by about 2m for\nposition components and about 1mm/sec for velocity components. This\nprocedure makes the covariance of the solution more meaninfgul. The\nonly disadvantage to the procedure is that it might mask the condition\nof equipment which is just marginally good; but the disadvantage could\nbe overcome by providing special diagnostic data.","52\nResults\nData Precision and Ephemeris Accuracy\nThe lower curves of Figures 2 and 3 show the standard errors in slant\nrange and in along track position, respectively, of the satellite (or\nthe station) for observations of a single satellite pass (Anderle, in\npress) . The graphs show that if only random errors of observation, a\nfrequency bias, and a refraction bias are considered, a single pass of\ndata would yield the two components of position of the satellite (or of\nthe station) to a precision of better than 75 cm for satellites passing\nat least 30 degrees above the station horizon. On the other hand, the\nupper curves on the figures show that the actual residuals with respect\nto the refined ephemeris are 2.5 and 1.6 m in slant range and along track\nposition for elevation angles above 30 degrees. These values provide\nthe best available information on the accuracy of the computed ephemeris\nconsidering such factors as errors in the gravity field and drag, but\nneglecting errors in origin, orientation and scale of the coordinate\nsystem.\nThe 2.5 m residuals in slant range reflect the net effect of the\nradial and out-of-plane orbit error. In most simulations of the effects\nof gravity errors on the ephemeris, the radial error was less than the\nout-of-plane error, but the studies were not extensive enough to assign\na ratio between the two error components with any reasonable degree of\nconfidence. In view of these uncertainties and the possibility that\nthe gravity field has been optimized to reduce errors at the observing\nstations, the rms periodic error in the refined ephemeris should be\nrounded up to 2m in each component of satellite position.\nExternal Tests\nDistances between sites derived from Doppler observations using the\nrefined ephemeris are found to be aobut one part per million long in\ncomparison with distances derived from terrestrial geodimeter measure-\nments, Very Long Base Line Interferrometric (VLBI) measurements of\nradio stars, or lunar laser measurements. The reason for the discrepancy\nis unknown, and derived Doppler positions in the NWL-9D system are\nfrequently scaled down to account for the difference. The adjusted\npositions are then consistent with geodimeter measurements over intra-\ncontinental distances to .7m and consistent with VLBI measurements over\nintercontinental distances to lm. (Anderle, in press).","53\nLong Term Consistency\nIn order to test the consistency of solutions for station positions\non a world wide basis, the coordinates of the base stations have been\ncomputed relative to the refined ephemeris at five day intervals\nstarting in 1973 for eight stations and in 1974 for the remaining\nstations. The standard deviation of the positions was found to be 70 cm\nin latitude and 90 cm in longitude and height. The standard errors in\nthe rates of change of the coordinates were 25cm/yr and 10cm/yr for\nsolutions based on 1.3 and 2.5 years of data, respectively. Computed\nrates of change of the coordinates were generally consistent with these\nstandard errors, except that the height changes for 30% of the stations\nwere excessive. The excessive height changes were probably due to\naliasing of the seasonal refraction effect which occurred because a\nrefraction bias parameter was not used in these position computations\nuntil 1976 (Anderle, 1975). Table 1 gives the rates and residuals while\nthe solutions for longitude, latitude, and height are given in Figures\n4,5, and 6, respectively.\nFigures 7a and 7b show that Doppler determinations of pole position\nare as consistent with the astronomic determinations of pole position as\nthe two astronomic services are with each other. The agreement in\nrecent years is about 0.5m.\nAccuracy Summary\nThe refined ephemeris has periodic errors of about 2m in each\ncoordinate due to uncertainties in the earth's gravitational field and\neffects of variations in atmospheric density on the computed satellite\nposition. Ground station positions derived from the ephemeris in the\nNWL-9D coordinate system are about one part per million long for un-\nknown reasons. To correct the scale and rotate the system in longitude\nto be consistent with gravimetric data in North America, NWL-9D co-\nordinates may be transferred to the NWL-10F system (which is consistent\nwith DoD WGS-72) as follows:\nLongitude\n11F = 19D + \"260\nGeocentric Latitude Y\n99\n=\nRadius\n9D - 5.27 m\nThe resulting coordinates are believed to be accurate to .7 . to\n.9 m in the given coordinate system. The origin of coordinate system is\nbelieved to be consistent with the center of mass of the earth to about\n1 m although the angular momentum vector may differ in orientation from\nthe reference system for star catalogues by 3 to 5 m. (However,\nthe variations in the pole position are followed to an accuracy of .5 m).","54\nReferences\nAnderle, R. J. , \"Transformation of Terrestrial Survey Data to Doppler\nSatellite Datum\", Journal of Geophysical Research, 79(35), 1974.\nAnderle, Richard J., \"Long Term Consistency in Positions of the Sites\nDetermined from Doppler Satellite Observations\", Naval Surface\nWeapons Center Report NSWC/DL TR-3433, November 1975.\nAnderle, R. J. \"Error Model for Geodetic Positions Derived from Doppler\nSatellite Observations\", Bulletin Geodesique, in press.\nBeuglass, Larry K. and Richard J. Anderle, \"Refined Doppler Satellite\nDeterminations of the Earth's Polar Motion\", Geophysical Monograph\nSeries Vol 15, American Geophysical Union, Washington, 1972.\nBeuglass, Larry K., \"Computation of Positions of Doppler Satellite\nObserving Stations\", Naval Surface Weapons Center Report, NSWC/DL\nTR-3137, June 1975.\nHopfield, H. S., \"Two-Quartic Tropospheric Refractivity Profile for\nCorrecting Satellite Data\", Journal of Geophysical Research, 74(18),\n4487-4499, 1973.\nO'Toole, James W., \"The 'CELEST' Computer Program for Computing\nSatellite Orbits, Naval Surface Weapons Center Report, in press.","55\nSPAN\nAVG NO\nRATE (cm/yr)\nRESIDUALS (cm)\nSTA\nLOCATION\n(Yrs)\nPASSES\nLONG\nLAT\nHT\nLONG\nLAT\nHT\n18\nThule\n1.3\n33\n-2+11\n-5+9\n-35+19\n43\n34\n72\n311\nMaine\n1.3\n17\n-13+32\n-16+23\n-5424\n109\n77\n80\n111\nMaryland\n1.3\n15\n7+21\n-29+13\n-31+25\n74\n49\n90\n192\nTexas\n1.3\n10\n-2+25\n-12+25\n-61+46\n74\n73\n135\n103\nNew Mexico\n2.5\n15\n16+10\n-34+7\n-89-10\n94\n67\n92\n323\nMinnesota\n1.3\n11\n25+33\n-75+19\n-129-26\n113\n62\n88\n334\nCalifornia\n1.3\n10\n-38+26\n-25-15\n-59+18\n99\n56\n69\n14\nAlaska\n1.3\n31\n47+19\n-28+10\n-5920\n67\n34\n71\n340\nHawaii\n1.3\n12\n-19+31\n-19+22\n-113+28\n108\n78\n98\n24\nSamoa\n1.3\n13\n62+31\n-32+19\n89+29\n110\n66\n103\n23\nGuam\n1.3\n12\n-16+29\n-59+18\n-74+32\n95\n59\n105\n13\nJapan\n1.2\n18\n7+15\n4+17\n-35+22\n50\n54\n71\n27\nJapan\n1.3\n15\n-36+30\n-36+27\n-105+37\n107\n97\n129\n22\nPhilippines\n1.3\n12\n28+27\n-56+22\n10+29\n103\n83\n109\n112\nAustralia\n2.5\n17\n-9+7\n7+5\n14+6\n66\n45\n54\n8\nBrazil\n2.5\n13\n46+9\n-8+8\n16+11\n82\n75\n101\n19\nMcMurdo\n2.5\n20\n4+21\n-29+22\n-52+19\n112\n115\n99\n16\nEngland\n2.5\n18\n5+8\n-5+5\n7+9\n73\n48\n81\n21\nUccles\n2.5\n21\n-5+7\n8+6\n-7+7\n65\n53\n69\n20\nSeychelles\n1.3\n12\n11+28\n-29+19\n-9+19\n94\n65\n64\n105\nAfrica\n2.5\n13\n34+15\n10+9\n-60+11\n129\n77\n89\nTable 1\nConsistency of Computed Station Positions\nfrom 1973-1975","JAPAN\nGUAM\nSAN MIGUEL\nADELAIDE\n.\nD\no\nMc MURDO\n&\no SEYCHELLES\nPRETORIA\nFLORENCE\nBELGIUM\no\nGRASSE\nENGLAND\nSAOPAULO\nMAINE\nMARYLAND\nTHULE\nOTTAWA\nNEW MEXICO\nO\nA\nMINNESOTA\nCALGARY\n0\n.\nCALIFORNIA\nCOOPERATING\nX\nx NAVIGATION\nGEOPHYSICS\nANCHORAGE\nSAMOA\nHAWAII\no\nx\nO","------------------\n90°\nFIG. 2 Weighted Residuals and Standard Error in Slant Range\n+\n60°\nELEVATION ANGLE\n30°\nRESIDUAL\nSTANDARD\nERROR\n0\n10\n5\n0","90°\nFIG. 3 Weighted Residuals and Standard Error in Along Track Position 1975\n60°\nELEVATION ANGLE\n30°\nRESIDUAL\nSTANDARD\nERROR\n0\n10\n5\n0","59\nTHREE YEAR SOLUTIONS FOR\nLONGITUDE\n1973\n1974\n1975\n2\nTHULE\n0\n2\nMAINE\n2\no\n-2\nMARYLAND\n2\n0\n2\nTEXAS\n2\no\n-2\nFIG. 4A Three Year Solutions for Longitude","60\nTHREE YEAR SOLUTIONS FOR\nLONGITUDE\n1974\n1975\n1973\n2\no\n-2\nNEW MEXICO\n2\n(\n0\n-2\nMINNESOTA\n2\n0\n-2\nCALIFORNIA\n2\no\n-2\nALASKA\nL\nFIG. 4B Three Year Solutions for Longitude","61\nTHREE YEAR SOLUTIONS FOR\nLONGITUDE\n1973\n1974\n1975\n2\n0\n-2\n13\n27\nJAPAN\n2\n(\no\n01\nGUAM\n-2\n2\no\nSAMOA\n2\n2\no\nHAWAII\n-2\nFIG. 4C Three Year Solutions for Longitude","62\nTHREE YEAR SOLUTIONS FOR\nLONGITUDE\n1973\n1974\n1975\n2\nPHILLIPINES\no\n2\nAUSTRALIA\n(v)\n2\n0\n-2\nBRAZIL\n2\no\n2\nMC MURDO\n2\no\n-2\nFIG. 4D Three Year Solutions for Longitude","63\nTHREE YEAR SOLUTIONS FOR\nLONGITUDE\n1973\n1974\n1975\n2\n0\n2\nENGLAND\n2\nE\no\nSTANDARD\n-2\nUCCLES\n2\no\n-2\nAFRICA\n2\no\n-2\nSEYCHELLES\nFIG. 4E Three Year Solutions for Longitude","64\nTHREE YEAR SOLUTIONS FOR\nLATITUDE\n1973\n1974\n1975\n2\nTHULE\no\n-2\n2\nMAINE\nE\no\nINFORMATION\n2\n2\nMARYLAND\n0\n2\nTEXAS\n2\no\n-2\nFIG. 5A Three Year Solutions for Latitude","65\nTHREE YEAR SOLUTIONS FOR\nLATITUDE\n1974\n1973\n1975\n2\no\n-2\nNEW MEXICO\n2\n(\no\n87\n-2\nMINNESOTA\n2\no\n-2\nCALIFORNIA\n2\n0\nALASKA\n2\n-\nFIG. 5B Three Year Solutions for Latitude","66\nTHREE YEAR SOLUTIONS FOR\nLATITUDE\n1975\n1973\n1974\n2\no\n13\n27\n- 2\nJAPAN\n2\n(u)\no\n-2\nGUAM\n2\no\nSAMOA\n-2\n2\no\nHAWAII\n-2\nFIG. 5C Three Year Solutions for Latitude","67\nTHREE YEAR SOLUTIONS FOR\nLATITUDE\n1974\n1975\n1973\n2\nPHILLIPINES\n0\n-2\nAUSTRALIA\n2\no\n-2\nBRAZIL\n2\no\n-2\nMC MURDO\n2\no\n-2\nFIG. 5D Three Year Solutions for Latitude","68\nTHREE YEAR SOLUTIONS FOR\nLATITUDE\n1973\n1974\n1975\n2\no\n2\n-\nENGLAND\nUCCLES\n(4)\n2\no\n-2\nSEYCHELLES\n2\no\n-2\nAFRICA\n2\no\n-2\nFIG. 5E Three Year Solutions for Latitude","69\nTHREE YEAR SOLUTIONS FOR\nHEIGHT\n1973\n1974\n1975\n2\nH\nHH\no\nTHULE\n2\n2\nH\nMH\no\nMAINE\nHH\n-2\n2\nH\nH\no\nMARYLAND\n2\nH\n2\no\nTEXAS\nHI\n-2\nH\nFIG. 6A Three Year Solutions for Height","70\nTHREE YEAR SOLUTIONS FOR\nHEIGHT\n1973\n1974\n1975\nH\n2\n0\nH\n-2\nNEW MEXICO\nH\n2\nH\no\n- 2\nMINNESOTA\nH\nM\n2\nH\nHH\no\n-2\nCALIFORNIA\n2\nH\nHI\nH\no\nHHH\nH\n-2\nALASKA\nFIG. 6B Three Year Solutions for Height","71\nTHREE YEAR SOLUTIONS FOR\nHEIGHT\nHH\nH\nHAWAII\nH\n2\no\nHH\n2\nSAMOA\nH\nH\n2\nH\no\n-2\nH\nGUAM\n2\nHH\nH\nH\no\nH\n2\nJAPAN\nH\n2\nH\nH\nH\nHIHHH\nH\nHIHH\no\nHH\n-2\nH\nFIG. 6C Three Year Solutions for Height","72\nTHREE YEAR SOLUTIONS FOR\nHEIGHT\n1973\n1974\n1975\nH\n2\nH\nH\nPHILLIPINES\nH\nHHH HH\nH\n0\nHH\nHH\nH\nHITH\nH\nH\nH\nH\n2\nHH\nH\nAUSTRALIA\n2\n0\nHHH\n-2\nBRAZIL\nH\n2\no\n-2\nMC MURDO\nHH\nH\nH\n2\nHH\no\nHH\n2\nw\nFIG. 6D Three Year Solutions for Height","73\nTHREE YEAR SOLUTIONS FOR\nHEIGHT\n1973\n1974\n1975\nENGLAND\n2\no\n2\nUCCLES\n2\nH\nH\n(\no\n07\n-2\nSEYCHELLES\nH\n2\nH\nHH\no\nHH\nHHH\nHH H\n-2\nAFRICA\n2\n0\nHH\n-2\nFIG. 6E Three Year Solutions for Height","74\ni\nDPMS-BIH\n3\n2\n1\n0\n-1\n-2\n-3\n-4\nDPMS-ILS\n(II)\n3\n2\n1\n0\n-1\n-2\n-3\nBIH-ILS\n3\n2\n1\n0\n-1\n-2\n-3\n1964\n1965\n1966\n1967\n1968\n1969\n1970\n1971\n1972\n1973\n1974\n1975\nYEAR\nFIG. 7A Comparison of X Component of Pole Position","75\nDPMS-BIH\n3\n2\nI\n0\n-1\n-2\n-3\nDPMS-ILS\n3\n2\n1\n0\nP\n-1\n-2\n-3\nBIH-ILS\n3\n2\n1\n0\n-1\n2\n-3\n-4\n1964\n1965\n1966\n1967\n1968\n1969\n1970\n1971\n1972\n1913\n1974\n1975\nYEAR\nFIG. 7B Comparison of Y Component of Pole Position","76","77\nCONCEPT OF SATELLITE DOPPLER POSITIONING USING\nTRANSLOCATION TECHNIQUES\nDavid E. Wells\nAtlantic Oceanographic Laboratory\nBedford Institute of Oceanography\nDartmouth, Nova Scotia, Canada\nAbstract\nSatellite Doppler positioning error sources can be classified as\nephemeris errors, refraction errors and receiver errors. The effects of the\nfirst two are correlated between stations simultaneously tracking a satellite\npass. Westerfield and Worsley gave the name \"translocation\" to techniques\nwhich take advantage of this correlation to improve accuracy. Currently any\ntechnique which includes simultaneous observations, but does not include\nexplicit modeling of satellite dynamics can be called a translocation\ntechnique. Translocation thus spans the gap between point positioning and\nshort arc techniques. Variations in translocation include two-dimensional\nand three-dimensional translocation; two station and multistation transloca-\ntion; the rigour with which simultaneity of the data is enforced; different\nreceiver deployment strategies; and the sophistication with which ephemeris\nand refraction errors, and their interstation correlations, are modeled.\nTranslocation does not usually require specialized hardware, however\nAlbertine and Ascher have suggested methods of supplementing the Doppler\ndata with measurements of the satellite-to-station slant range differences\nbetween stations simultaneously tracking the same satellite.\nThe Translocation Concept\nIn 1964 investigators at the Johns Hopkins University Applied Physics\nLaboratory collected data from 12 Transit satellite passes on each of two\nreceivers sharing a common antenna. At that time the radial standard devia-\ntion of a two-dimensional, single pass Transit position fix was about 100 m\n(Newton, 1967). However, the rms radial dispersion of the differences between\neach pair of these 12 two-dimensional fixes was only 7.3 m (Westerfield and\nWorsley, 1966) Subsequent tests using pairs of stations separated by up to\n1700 km indicated that relative positioning accuracy from simultaneously\nobserved passes degraded with station separation, but was still about twice\nas accurate at 1700 km as the \"stand alone\" single station accuracy (Kershner,\n1965).\nThe use of simultaneous data from separate stations to determine the\nrelative position of one station with respect to another was given the\nname translocation by Westerfield and Worsley. Originally this concept was\napplied to two-dimensional (2D), single pass, two-station relative positions.\nIt was extended to three-dimensional (3D), multipass, two-station relative\npositions by Smith (1970), and to 3D multipass, multistation relative posi-\ntions by Kouba (1976).","78\nThe Rationale Behind Translocation\nSatellite Doppler positioning error sources can be classified as\nephemeris errors, refraction errors, and receiver errors. Both ephemeris\nerrors and refraction errors are correlated between stations which track the\nsame satellite pass. However the degree of correlation depends on station\nseparation and relative orientation. Let us first find intuitive explana-\ntions for the factors controlling this correlation, and then review the\nexperimental evidence which has accumulated.\nThere are four cases to consider in the correlation of refraction errors\nbetween stations. Doppler satellite data are affected by both tropospheric\nand ionospheric refraction. In each case, either a correction is not applied,\nand it is the full refraction effect correlation that is of interest; or a\ncorrection is applied and we are interested in the residual effect correla-\ntion only. Both the troposphere and ionosphere are subject to instabilities\n(e.g., weather fronts and diurnal shifts) which degrade or destroy the spatial\ncorrelation of the refractive effects.\nIn the troposphere under stable weather conditions, the full refraction\ncorrection at 20° elevation varies by 1 cm for every 1.7 mb pressure change;\n0.4° temperature change; or 0.3 mb water vapor pressure change. The\nvariation of pressure with distance under stable conditions is a few hundred\nkm per mb (a hurricane has typically 10 km/mb and a strong storm 40 km/mb).\nTemperature and vapor pressure are more variable. In the next section, tests\nof the correlation of both tropospheric and ionospheric refraction are\npresented.\nEphemeris errors are perfectly correlated between stations which are\nsufficiently close that the station-satellite geometry can be taken as identi-\ncal. As the station separation increases, the correlation decreases for\ndifferent reasons, depending on whether the separation is oriented parallel\nor perpendicular to the satellite subtracks (respectively North-South or\nEast-West in low and middle latitudes for polar Transit satellites.)\nFor parallel separations, the time of closest satellite approach to\neach station will differ. In this situation, there are two irreconcilable\ndata selection criteria. Doppler observations at a single station which are\nasymmetric about the time of closest approach tend to introduce biases into\nthe solution. On the other hand a rigorous application of the translocation\nconcept demands that the Doppler observation intervals be identical for each\nstation. 'Fig. 1 shows the increasing conflict between these two criteria\nas a function along-the-satellite-track (North-South) station separation.\nIf a satellite pass subtrack falls between two stations, then the\neffects of cross-track ephemeris errors and refraction errors will have\nopposite signs at the two stations. The correlation in this case is negative.\nThis results in another two irreconcilable data selection criteria. A set of\nsatellite passes at a single station which are asymmetrically distributed in\nthe cross-track direction tend to introduce biases into the solution. On\nthe other hand, a rigorous application of the translocation concept demands\nthat passes falling between the stations be rejected, resulting in a bimodal","79\ndistribution in the cross-track direction. Fig. 2 shows the increasing con-\nflict between these two criteria as a function of across-the-satellite-track\n(East-West) station separation.\nAs the cross-track station separation increases, the angle subtended at\nthe satellite by the station separation vector increases, at different rates\nfor satellite passes having different closest approach elevation angles.\nAssuming a cross-track ephemeris error or refraction error of one metre\noriented along the slant range vector between the satellite and the near\nstation, the effect of this error on the slant range vector to the far station\nis shown in Fig. 3.\nNote that ephemeris errors are often predominantly in the along-track\ndirection (particularly for predicted ephemerides), and that the correlation\nof along-track errors is not degraded in any of the ways discussed here.\nTherefore an along-track error correlation will remain between stations\ncapable of tracking the same pass, even with station separations of as much\nas 4000 km in any orientation.\nTests of Translocation\nMany tests of translocation have been performed since the original tests\nin 1964. Tables 2 to 8 give results of tests of 2D translocation. Tables\n9 to 14 give results of tests of 3D translocation. Table 1 summarized the\ncharacteristics of each test. Tables 6, 7, 8, 14 are previously unpublished.\nThe basic measurement of translocation performance is the vector differ-\nence between the \"true\" and translocated station separation vectors. We call\nthis vector difference the discrepancy vector D. In the absence of an exter-\nnal standard for the \"true\" station separation vector, the mean or median of\nrepeated translocations is used. In Tables 2 to 8 the median value of the\nmagnitudes D of the discrepancy vectors from repeated 2D single pass trans-\nlocations has been used as the translocation performance indicator. In\nTables 9 to 14 the magnitude of the single discrepancy vector from each 3D\nmultipass solution has been used. However, in Tables 10 and 11, repeated 3D\nfour-pass solutions have been computed, and the root mean square (rms) value\nof the magnitudes of the discrepancy vectors has been used as the translocation\nperformance indicator.\nThe effectiveness of translocation in reducing the effect of ephemeris\nerrors can be seen from Table 5 line 5, where the precise ephemeris fails to\nimprove on the results obtained with the less accurate broadcast ephemeris.\nTable 5 lines 4 and 6 indicate that ionospheric refraction is highly correlated\nbetween stations separated by 37 km. Table 6 indicates that this correlation\npersists to several hundred km, and that tropospheric refraction is highly\ncorrelated out to 1000 km separations.\nTranslocation takes advantage of the correlation of ephemeris and refrac-\ntion errors, and therefore is more effective when the uncorrelated receiver\nerrors are minimized. If receiver errors dominate, translocation provides\nvery little benefit. Receiver errors are more likely to dominate at short\nstation separations, where the ephemeris and refraction errors are highly\ncorrelated, than at longer separations where the correlation is less.","80\nNoisy oscillators and timing circuit delays and jitter are two major\nreceiver error sources. Table 7 line 4 shows the effect of oscillator noise\nof the order of 20 parts in 1010. Geodetic receivers reduce the effects of\ntiming delays and jitter by incorporating a local clock in the receiver. The\neffect of this improved time recovery is shown in Table 5 lines 3 and 8;\nTable 7 lines 1 and 2; and Table 8.\nThe effect of orientation of the translocation line to the satellite\ntrack is shown in Tables 10 and 11. Table 11 results indicate that the\nstandard deviation of the magnitude of the discrepancy vector from a 3D N-pass\nsolution is (5.6 m + 2 ppm) IVN for along-track lines,\n(5.6 m + 10.8 ppm) N for cross-track lines.\nAbove latitude 70° the association of \"along-track\" with \"north-south\"\nand \"cross-track\" with \"east-west\" is no longer valid, since the polar Transit\nsatellites are tracked as they cross the pole, in which case \"cross-track\" can\nmean \"north-south\". The orientation of satellite passes becomes increasingly\ndispersed as one approaches the pole, and it is a useful strategy to maintain\na record of these orientations for data analysis and selection purposes. The\ndata for Tables 7 and 8 were acquired above latitude 70°.\nTable 5 lines 4 and 7 indicate that the choice of a shorter Doppler inte-\ngration interval length has a significant effect on accuracy.\nTable 8 indicates that careful pass selection (in this case by elevation\nangle) can significantly improve results.\nAlthough it is not shown here, 2D translocation at separations of order\n100 m is very seriously affected by non-common Doppler observations. On the\nother hand, Tables 11 and 12 demonstrate the validity of using equal numbers\nof Doppler observations at both stations, rather than rigorously simultaneous\nobservations at both stations, for 3D multipass translocations from 5 to 2000 km\nseparations. Tables 11 and 12 also indicate that 3D simultaneous point posi-\ntioning (in which all data is used, whether common to both stations or not)\ngives results only slightly degraded from translocation, for station separa-\ntions from 5 to 800 km, but provides better results than translocation for\nseparations longer than 800 km.\nFigures 4, 5 and 6 summarize the results of some of these tests.\nTranslocation Strategies\nThe observational and computational strategies one should adopt in Doppler\nsatellite positioning depends on the number of available receivers, the\nstation separations required, whether one's priorities are to maximize\naccuracy or minimize survey cost for a specified accuracy, and the respective\npriorities of absolute and relative positioning accuracies.\nObviously at least two receivers are required before simultaneous obser-\nvations can be made. If only two receivers are available, a common deployment\nstrategy is the \"star\" or master-slave technique, where one receiver is kept\nat a base station and the second \"slave\" receiver is operated at a sequence\nof stations surrounding the base camp. This technique can be used when more\nthan two receivers are available, advantages being that the base station can","81\nbe the logistics center, and that it is possible to use simplified slave\nreceivers (perhaps recording Doppler counts only). However, these may not be\nreal advantages in the light of receiver hardware capable of unmanned operation,\nparticularly if the area to be surveyed is beyond the useful translocation\nrange from one base station.\nAn alternative deployment strategy is for the network of receivers to\nslowly migrate across the survey area, by staggered shifting of one receiver\nat a time, as described in Kouba (1976).\nAll of the tests reviewed in this paper treated translocations as a two\nstation relative positioning technique. In fact the processing in almost\nevery case used the difference between point positioning solutions computed\nseparately, with the data first edited to conform to translocation require-\nments. If we accept the eventual goal of 10 cm Doppler satellite positioning\naccuracy, it is more appropriate to accept the data from all available stations\nat once, allowing each pass to update the coordinates of each station tracking\nit. In this case the rigorous translocation concept can be enforced for short\nstation separations, and not enforced for longer separations, and the ephemeris,\nrefraction and other errors which are correlated between stations can be\nestimated as part of the solution in both cases.\nThe advantages of enforcing rigorous simultaneity of the data are\ngreatest with the shortest station separations, and are questionable above\nabout 200 km. However, Kouba (1976) has shown that the inter-station correla-\ntion decreases slowly with a decrease in common data, when the ephemeris and\nrefraction errors are modeled in the solution, rather than handled by the\nrigorous application of the translocation concept. In this case the orienta-\ntion dependence of translocation is eliminated for separations up to 2000 km,\nand equivalent relative positioning accuracies are obtained with either broad-\ncast or precise ephemerides (Kouba and Wells, 1976). A similar situation\nexists when the orbit itself, rather than only the orbit errors, is modeled\nin the solution, as is the case with short arc solutions. Note that the\nsimultaneous operation of several receivers is still required, but that passes\nand Doppler observations are not rejected according to the translocation con-\ncept.\nLet us consider an alternative translocation algorithm. In Fig. 7, Sij\nis the slant range from the satellite at time ti to station j. Between t1\nand t2 the Doppler observation equations at stations 1 and 2 have the form\n(1)\nN1 = a1 + b1 (S21 - S11)\n(2)\nN2 = a2 + b2 (S22 - S12)\nand\n( Nz - 82)\n(3)\nAS2\nAS1\n=\n-\n,\nwhere AS is the slant range difference from the satellite to each of the two\nstations at ti. If the two stations are using the same local oscillator or","82\nif both are using precise clocks (such as cesium standards) then b1 = b2 and\na1 and a2 differ only due to the different receiver timing delays. If these\ndelays too are measured to determine their difference Aa (maintaining satellite\ntiming of the Doppler integration intervals) then we obtain\n(4)\nAa)= AS2 AS1\n.\nWhen the station separation R is small enough (say less then 1 km), we\ncan consider the vectors Sil and Si2 to be parallel, with unit vector Si.\nThen the projection of R onto Si is ASi = R . Si and AS2 - AS1 = R . (S2-S1) or\n1 N 2\n(5)\n,\nthat is, the Doppler count difference between the two stations is a direct\nobservation of the station separation vector R.\nAlbertine (1974a; 1974b) has extended this approach by making additional\nmeasurements, replacing the left hand side of equation (5) by comparing the\n32 kHz signal phases from receivers 1 and 2. He indicates that with some\nhardware development, azimuths accurate to about 25 arcseconds should be\nobtainable with separations of 100 m.\nWhen the station separation R is larger, the expression on the right\nhand side of equation (5) is replaced by the more complicated\nAS2 - AS1 = S21 (1 S21 S21 )\n(6)\n-\n,\nhowever, the principle of determining R by this approach remains valid.\nAscher (1974) has considered the advantages of supplementing the Doppler\nmeasurements by directly measuring the time lags AS using accurate clocks.\nHis simulations indicate that at station separations up to order 100 km these\nmeasurements would improve both relative and absolute positioning accuracy;\nand that the time lag measurements alone would provide results almost as\ngood as both Doppler and time lag measurements together.\nSummary\nWe have seen that there are many variations of the translocation concept,\nincluding 2D and 3D translocation; two station and multistation translocation;\nthe rigor with which simultaneity of the data is enforced; different receiver\ndeployment strategies; and the sophistication with which ephemeris and refrac-\ntion errors and their interstation correlations are modeled. The common\nfactor in all these variations is that two or more receivers be operated in\nthe same survey area simultaneously, in order to improve relative positioning\naccuracy. In this context the translocation concept spans the gap between\nindependent point positioning on the one hand, and the short arc technique\non the other.","83\nThe character of translocation techniques changes as the station separa-\ntion changes from short (less than 1 km) to medium (up to a few hundred km)\nto long.\nAt short separations translocation is seriously degraded by even the\noccasional non-simulated observation. It is important to use stable local\noscillators (or a common oscillator if the equipment is not too far separated), ,\nand to make improved time recovery measurements. Refraction corrections need\nnot be made, nor ephemeris errors modeled.\nAt medium separations, enforcing rigorous data simultaneity still improves\nthe results significantly. Refraction effects are still highly correlated,\nalthough the residual effects after making the usual corrections may not be\nso highly correlated. It is more important to apply rigorous translocation\nwhen the ephemeris errors are larger (as for predicted ephemerides). An\nalternative translocation algorithm, and additional time lag measurements,\nmay provide advantages.\nAt long separations, enforcing rigorous data simultaneity introduces\nserious asymmetrics into the data, and an accuracy dependent on the orienta-\ntion (across-track or along-track) of the station separation. Better alter-\nnatives are to enforce equal numbers of observations for each pass at all\nstations, and/or to estimate the ephemeris and refraction errors as part of\na multistation solution, (in which not all passes need be tracked at all\nstations). .\nAcknowledgements\nMuch of the author's knowledge of translocation has been learned in\ndiscussions with Pat Martin, Alan Thorndike, and Gillespie of the Arctic Ice\nDynamics Joint Experiment.","84\nBibliography\nAlbertine, J.R. (1974a). An azimuth determination system using the Navy Navi-\ngation Satellites. Johns Hopkins University Applied Physics\nLaboratory Technical Memorandum TG-1235. May.\nAlbertine, J.R. (1974b). An azimuth determination system utilizing the Navy\nNavigation Satellites. Journal of the Institute of Navigation\n21, 54-60.\nAscher, L.\n(1974). Relative Positioning by Navigation Satellite using\nDoppler Shifts and Propagation Delays as Observables. Ph.D.\nThesis, Iowa State University.\nBrunell, R.D. (1976). A Comparison of Several Doppler Satellite Data Reduc-\ntion Methods. These proceedings.\nDefense Mapping Agency (1972). Report of the DOD Geoceiver Test Program. DMA\nReport 0001. July.\nDennis, A.R. (1976). Geocentric Positioning via Satellite of a Drilling\nPlatform in the North Sea. These proceedings.\nDenzler, D.W.R. (1972). Translocation Reference Manual. Johns Hopkins Uni-\nversity Applied Physics Laboratory Technical Memorandum TG-1174.\nJanuary.\nGloeckler, F.M. (1972). Recent Translocation Results using Navigation Sat-\nellites. National Technical Information Service accession number\nAD-785 625/5GA.\nGloeckler, F.M., Muniz, R.R. and Schmeidel, G.W. (1974). Doppler Transloca-\ntion Test Program. National Technical Information Service\naccession number AD-A009 772/5GA.\nHatch, R. (1976). New Positioning Software from Magnavox. These proceedings.\nKershner, R. B. (1965). Present State of Navigation by Doppler Measurement\nfrom near Earth Satellites. Applied Physics Laboratory Technical\nDigest 5, no. 2, 2-9. November-December.\nKouba, J. (1976) Doppler Satellite Control in Establishing Geodetic Control\nNetwork. Publications of the Earth Physics Branch, Vol. 45,\nNo. 3, 167-184.\nKouba, J. and Boal, J.D. (1976). Canadian Doppler Satellite Network. These\nproceedings.\nKouba, J. and Wells, D.E. (1976). Semi Dynamical Doppler Satellite Geodesy.\nBulletin Geodesique 50, 27-42.","85\nKrakiwsky, E.J., Wells, D.E. and Kirkham, B.P. (1972). Geodetic Control from\nDoppler Satellite Observations. The Canadian Surveyor 26, 146-162.\nKrakiwsky, E.J., Wells, D.E. and Thomson, D.B. (1973). Geodetic Control from\nDoppler Satellite Observations. The Canadian Surveyor 27, 141-148.\nNewton, R.R. (1967). The Navy Navigation Satellite System. Space Research VII,\n2, 735-763.\nPiurek, W.J., Johnson, J.E. and Vivion, J. (1976). A portable Geodetic\nPositioning System with Real-Time Fix Computation. These proceedings.\nRutscheidt, E.H. (1974). Worldwide Geodetic Positioning from Satellites with\nPortable Doppler Receivers. Proceedings of the Fourteenth Inter-\nnational Congress of Surveyors. Washington.\nSchwarz, C.R., Sharp, C.B. and Smith, R.W. (1972). Geoceiver Tests: USA\nTOPOCOM Operations and Phase I Results. U.S. Army Topographic\nCommand Geodetic Memorandum No. 1668. February.\nSchwarz, C.R., and Smith, R.W (1972). Accuracies and Errors Associated with\nMiniaturized Doppler Receivers. U.S. Army Topographic Command\nGeodetic Memorandum No. 1670. April.\nSmith, R.W. (1970). Results of ITT 5001 Doppler Receiver Tests. U.S. Army\nTopographic Command Geodetic Memorandum No. 1651. September.\nSmith, R.W. and Williams, G.E. (1971). Error Analysis of Doppler Positioning\nwith the ITT 5500 Integrated Doppler Receiver. U.S. Army Topo-\ngraphic Command Geodetic Memorandum No. 1660. July.\nSpradley, L.H. (1976). Control Network Extension Through Satellite Transloca-\ntion. These proceedings.\nWells, D.E. (1974). Doppler Satellite Control. University of New Brunswick\nDepartment of Surveying Engineering Technical Report No. 29.\nWesterfield, E.E. and Worsley, G. (1966). Translocation by Navigation Satellite.\nApplied Physics Laboratory Technical Digest 5, No. 6, July-\nAugust 1966, 2-10.","Gloeckler et al, 1974\nKrakiwsky et al, 1972\nKrakiwsky et al, 1973\nSchwarz et al, 1972\nSmith and Williams,\nRutescheidt, 1974\nWesterfield and\nKershner, 1965\nWorsley, 1966\nDenzler, 1972\nWells, 1974\nSource\n1971\nIntegration\nInterval\nvaries\nFurther Characteristics Included in Table Captions.\n120 S\n120 S\n120 S\n4.6\n120\n120\n120\n4.6\nSummary of Translocation Test Characteristics.\n30\n30\n30\n30\nRecovery\nvaries\nvaries\nvaries\nyes\nyes\nyes\nTime\nno\nno\nno\nno\nno\nno\nno\nFrequencies\nvaries\nvaries\nTable 1\nyes\nyes\nyes\nyes\nyes\nyes\nyes\nyes\nyes\nno\nno\nTwo\nEphemeris\nbroadcast\nbroadcast\nbroadcast\nbroadcast\nbroadcast\nbroadcast\nbroadcast\nbroadcast\nbroadcast\nprecise\nprecise\nprecise\nvaries\nSeparations\n90-1700 km\n0- 72\n30- 930\n0- 89\n116-1110\n0- .07\n496\n276-1078\n0-1600\n104-1867\n6- 27\n0- 196\n59- 276\nStation\nYear\ntest\n1964\n1964\n1967\n1972\n1973\n1974\n1975\n1970\n1971\n1971\n1972\n1972\n1973\nof\nDimensions\n2\n2\n2\n2\n2\n2\n2\n3\n3\n3\n3\n3\n3\nTable\n2\n3\n4\n5\n6\n7\n8\n9\n10\n11\n12\n13\n14","87\nDistance\nD\n(median)\nLine\n(km)\n(m)\n1\n90\n14\n2\n280\n18\n3\n360\n28\n4\n530\n24\n5\n1700\n52\nTable 2\nFrom Kershner (1965) .\nD\n(median) is the median of the magnitudes of the discrepancy vectors from\nall 2D single pass translocations.\nDistance\nNo. of\nD (median)\nLine\n(km)\nPasses\n(m)\n1\n0\n12\n4\n2\n0.1\n16\n4\n3\n17\n16\n10\n4\n72\n23\n12\nTable 3\nFrom Westerfield and Worsley (1966) ,\nwho quote similar results without ionospheric refraction correction, and\ndegradation by a factor of 3 when Doppler observations are not rigorously\nsimultaneous. True station separation is median of repeated 2D translocations. .\nD (median)\nDistance\nAzimuth\nLine\n(km)\n(degrees)\n(m)\n1\n30\n5\n2\n53\n8\n3\n262\n10\n13\n4\n328\n45\n24\n5\n462\n-10\n14\n6\n504\n65\n21\n7\n832\n20\n14\n8\n930\n-85\n20\nTable 4\nFrom Denzler (1972).\nApproximately 20 passes per line.\n.","88\nD\nDistance\nAzimuth\nNo. of\n(median)\nLine\n(km)\n(degrees)\nPasses\n(m)\nRemarks\n1\n0\n46\n3.1\nCommon antenna, common\noscillator\n2\n0\n93\n3.1\nCommon antenna, separate\noscillator\n3\n9\n-35\n94\n3.3\n4\n37\n-80\n20\n2.3\n30 seconds, two frequencies\n5\n37\n-80\n12\n2.4\n30 seconds, two frequencies,\nprecise ephemeris\n6\n37\n-80\n17\n3.1\n30 seconds\n7\n37\n-80\n18\n4.4\nTwo frequencies\n8\n37\n-80\n20\n11.0\nNo time recovery\n9\n57\n25\n154\n5.0\n10\n89\n85\n11\n8.8\nTable 5\nFrom Gloeckler et al (1974) .\nUnless otherwise noted, broadcast ephemeris, single Doppler frequency, improved\ntime recovery, and 120 second Doppler counts are used. True station separa-\ntion is mean of repeated 2D translocations.\nD\nDistance\nAzimuth\nNo. of\n(median)\nLine\n(km)\n(degrees)\nPasses\n(m)\n1\n116\n-70\n41\n9\n2\n265\n-80\n31\n9\n3\n549\n-40\n26\n14\n4\n901\n55\n23\n10\n5\n1110\n85\n15\n16\n6\n116\n-70\n40\n7\n7\n265\n-80\n29\n8\n8\n549\n-40\n25\n16\n9\n901\n55\n22\n10\n10\n1110\n85\n16\n16\n11\n116\n-70\n34\n8\n12\n265\n-80\n26\n11\n13\n549\n-40\n26\n18\n14\n901\n55\n20\n21\n15\n1110\n85\n13\n31\nTable 6\nReprocessing of data in Wells (1974) .\nLines 1-5 were computed applying both ionospheric and tropospheric refraction\ncorrections, Lines 6-10 were recomputed with only the ionospheric correction.\nLines 11-15 were recomputed with only the tropospheric correction. True Station\nseparation is median of repeated 2D translocations with both ionospheric and\ntropospheric corrections.","89\nD\nDistance\nAzimuth\nNo. of\n(median)\nLine\n(m)\n(degrees)\n(m)\nRemarks\npasses\n1\n0\n101\n2.5\nCommon antenna, common\noscillator\n2\n0\n47\n20\nCommon antenna, common\noscillator, no time\nrecovery\n3\n0\n21\n3.2\nCommon antenna, separate\noscillator\n4\n0\n27\n15\nCommon antenna, separate\noscillator, noisy\noscillator\n5\n3.6\n11\n2.1\nSeparate antenna, common\noscillator\n6\n69\n-75\n48\n2.5\nSeparate antenna, common\noscillator\n7\n69\n-75\n50\n4.5\nSeparate antenna, separate\noscillator\nTable 7\nShort range translocations from Arctic Ice Dynamics Joint Experiment.\nTrue station separation is that surveyed in the field.\nD (median)\nDistance\nAzimuth\nNo. of\nLine\n(km)\n(degrees)\n(m)\nRemarks\npasses\n1\n496\n-75\n8\n12\nTime recovery, 20°-60°\npasses\n2\n496\n-75\n8\n14\nNo time recovery, 20°-\n60° passes\n3\n496\n-75\n17\n29\nTime recovery, 0°-75°\npasses\n4\n496\n-75\n17\n23\nNo time recovery, 0°-\n75° passes\nTable 8\nMedium range translocation from Arctic Ice Dynamics Joint Experiment.\nTrue station separation is median of repeated 2D translocations.","90\nDistance\nAzimuth\nD (tr)\nNo. of\nLine\n(km)\n(degrees)\n(m)\npasses\n1\n276\n-85\n52\n2.1\n2\n842\n-70\n44\n3.4\n3\n901\n40\n40\n13.8\n4\n930\n0\n32\n11.3\n5\n985\n-15\n35\n6.2\n6\n1078\n50\n36\n9.4\nTable 9\nFrom Krakiwsky et al (1972) .\nD (tr) is the magnitude of the discrepancy vector from one 3D multipass trans-\nlocation. True station separations are from a special adjustment of geodetic\nnetworks in eastern Canada.\no D (4-pass)\nDistance\nAzimuth\nLine\n(km)\n(degrees)\n(m)\n1\n0\n5.4\n2\n100\n0\n5.1\n3\n300\n0\n5.8\n4\n500\n0\n6.0\n5\n800\n0\n6.4\n6\n1200\n0\n7.5\n7\n1600\n0\n7.5\n8\n100\n90\n5.6\n9\n300\n90\n6.9\n10\n500\n90\n7.7\n11\n800\n90\n9.3\n12\n1200\n90\n12.2\n13\n1600\n90\n15.2\nTable 10\nSimulation results from Smith and Williams (1971)\no\nD (4-pass) is the rms value of the magnitude of the discrepancy vectors from\nrepeated 3D 4-pass translocations These results indicate o D (tr) for 3D\nN-pass - translocation is (10.2 m + 3.4 ppm) /VN for along-track lines and\n(10.2 m + 11.4 ppm) /VN for across-track lines.","91\nD (tr)\no\nDistance\nAzimuth\nNo. of\nD (4-pass)\nD (SPP)\nLine\n(km)\n(degrees)\nPasses\n(m)\n(m)\n(m)\n1\n104\n80\n16\n0.7\n2.9\n1.2\n2\n266\n0\n26\n1.8\n4.2\n1.8\n3\n278\n-30\n122\n2.3\n2.3\n4\n301\n-70\n28\n0.5\n5.0\n0.9\n5\n420\n0\n23\n2.4\n2.9\n6\n641\n15\n24\n2.3\n3.0\n2.2\n7\n768\n80\n96\n1.4\n6.9\n1.6\n8\n779\n0\n26\n1.0\n4.1\n1.1\n9\n783\n85\n87\n1.1\n5.8\n1.3\n10\n793\n75\n73\n3.5\n3.8\n11\n879\n20\n118\n1.5\n1.8\n12\n899\n5\n36\n1.5\n3.4\n1.7\n13\n929\n-45\n39\n2.7\n1.7\n14\n998\n10\n122\n3.7\n3.3\n15\n1060\n5\n93\n1.4\n1.2\n16\n1082\n-85\n28\n0.7\n5.4\n0.8\n17\n1093\n80\n30\n2.9\n12.4\n2.1\n18\n1095\n30\n101\n3.4\n2.7\n19\n1523\n35\n78\n4.1\n2.7\n20\n1867\n80\n24\n4.6\n9.3\n2.0\nTable 11\nFrom Schwarz et al (1972) .\nD\n(SPP) is the magnitude of the discrepancy vector obtained by differencing\nthe simultaneous point position of each station. Equal numbers of Doppler\nobservations for each pass at each pair of stations was enforced, rather than\nrigorously simultaneous data. True station separations are from the High\nPrecision Geodimeter Traverse.","92\nD\nD\nDistance\nAzimuth\nNo. of\n(tr)\n(SPP)\nLine\n(km)\n(degrees)\nPasses\n(m)\n(m)\n1\n6\n-55\n45\n1.5\n1.3\n2\n6\n10\n47\n1.8\n2.1\n3\n9\n-75\n45\n0.8\n1.8\n4\n11\n-20\n44\n2.3\n1.8\n5\n13\n20\n38\n0.7\n0.6\n6\n13\n20\n51\n0.8\n1.0\n7\n15\n-65\n44\n1.8\n1.8\n8\n16\n0\n49\n0.5\n1.3\n9\n20\n-75\n37\n1.1\n0.9\n10\n20\n-75\n56\n0.4\n0.6\n11\n22\n-25\n48\n1.3\n2.7\n12\n23\n-40\n48\n0.9\n0.6\n13\n23\n5\n46\n1.6\n2.8\n14\n27\n70\n41\n0.4\n0.8\nTable 12\nFrom Rutscheidt (1974) .\nEqual numbers of Doppler observations for each pass at each pair of stations\nwas enforced, rather than rigorously simultaneous data. True station\nseparations from a special adjustment of the geodetic networks in the Washing-\nton urban area.\nD\nDistance\nAzimuth\nNo. of\n(tr)\nLine\n(km)\n(degrees)\nPasses\n(m)\n1\n.01\n31\n2.1\n2\n15\n10\n71\n5.6\n3\n59\n15\n109\n2.9\n4\n93\n-80\n106\n3.6\n5\n116\n-75\n102\n4.1\n6\n165\n-45\n95\n4.5\n7\n196\n-50\n111\n3.3\nTable 13\nFrom Krakiwsky et al (1973) .\nTrue station separations from special adjustment of geodetic networks in\neastern Canada.","93\nDistance\nAzimuth\nD\nNo. of\n(tr)\nLine\n(km)\n(degrees)\nPasses\n(m)\n1\n59\n15\n55\n3.7\n2\n93\n-80\n39\n4.5\n3\n102\n-40\n38\n7.8\n4\n116\n-75\n65\n3.0\n5\n117\n55\n34\n8.3\n6\n150\n-80\n53\n4.0\n7\n165\n-45\n73\n2.9\n8\n196\n-50\n37\n6.3\n9\n265\n-75\n50\n3.7\n10\n276\n-85\n83\n3.6\nTable 14\nData from Wells (1974). .\nThree orbit biases estimated for each two-station pass solution. True station\nseparations from special adjustment of geodetic networks in Canadian Maritime\nprovinces.\n100\n20\n80\n45°\n60\n70°\n40\n20\no\nO\n500\n1000\n1500\n2000\nALONG TRACK SEPARATION ( km )\nFIG. 1\nThe effect of rigorously enforcing simultaneity of data between stations\nwith an along-track (north-south) separation upon Doppler symmetry about\nclosest approach. 100% asymmetry means all data are to one side of closest\napproach. Deletion of data below 7.5° elevation is assumed.","94\n100\n80\n60\n40\n20\nO\no\n500\n1000\n1500\n2000\nCROSS TRACK SEPARATION (km )\nFIG. 2\nThe effect of rigorously enforcing rejection of passes falling between stations\nwith a cross-track (east-west) separation upon cross-track pass symmetry. 100%\nasymmetry means no pass to the east of the station can be matched to a pass\nwhose subtrack is equidistant from the station but to the west. Deletion of\npasses with maximum elevations below 15° is assumed.\n1.0\n20°\n45°\n.9\n.8\n70°\nO\n500\n1000\n1500\n2000\nCROSS TRACK SEPARATION (km)\nFIG. 3\nThe slant range error at the farthest of two stations on the same side of a\nsatellite pass, given an error of one metre oriented along the slant range\nvector to the nearest station, as a function of maximum satellite elevation\nat the station nearest the subtrack, and the cross-track separation.","95\nTABLE 3\n10\nTABLE 5\n5\nO\nO\n50\n100\nSEPARATION ( km )\nFIG. 4\nMedians of magnitudes of discrepancy vectors from repeated 2D single pass trans-\nlocations for medium station separations. Table 3 data is with an ionospheric\nrefraction correction but no improved time recovery. Table 5 data is with no\nionospheric refraction correction, but with improved time recovery.\nTABLE 2\n50\n40\n30\nTABLE 4 (EW)\n20\nTABLE 4 (NS)\nTABLE 6\n10\no\no\n500\n1000\n1500\n2000\nSEPARATION (km)\nFIG. 5\nMedians of magnitudes of discrepancy vectors from repeated 2D single pass trans-\nlocations for long lines. Tables 2 and 4 data were collected in the middle\n1960' S, and Table 6 data in 1973.","96\nTABLE 9\n10\nTABLE II\n5\nO\nO\n500\n1000\n1500\n2000\nSEPARATION ( (km)\nFIG. 6\nMagnitude of discrepancy vector from 3D multipass translocations. Table 9\ndata used the broadcast ephemeris, and was without improved time recovery.\nTable 11 data used the precise ephemeris and improved time recovery.\nt2\nt,\nS21\nS12\nS22\nS11\nI\nR\n2\nFIG. 7\nTranslocation station geometry. .","97\nDOPPLER POSITIONING BY THE SHORT ARC METHOD\nDuane C. Brown\nPresident, DBA Systems, Inc.\nMelbourne, Florida\nAbstract\nThe Short Arc Method has progressed to the point where rms accuracies\nof relative positioning on the order of 0.25 m have been demonstrated from\nthe reduction of sets of 40 or so passes using the Broadcast Ephemeris. An\noutline of the essentials of the Short Arc Method, as implemented in the\nprogram SAGA III, is provided. Because the Short Arc Method using the\nBroadcast can produce appreciably higher accuracies in relative positioning\nthan can be expected from Point Positioning using the Precise Ephemeris, it\nis suggested that a re-examination is in order concerning the design of\ncurrent projects in support of the readjustment of the North American Datum.\nIntroduction\nJust what constitutes the Short Arc Method seems to be subject to wide-\nspread misunderstanding. In the DMA \"Report of the Geoceiver Test Program\"\n(DMA Report 0001, July 1972) it is stated that \"a minimum of one station\nmust be constrained in a [short arc] network adjustment in addition to the\nuse of some orientation constraints (azimuth and elevation angles).\" Anderle\n(1974) states that \"\nin the short-are technique, Doppler stations are\ndeployed at three known locations to determine the satellite orbit to be\nused in computing the location of a fourth station\nThere are two\ndisadvantages to using short-arc procedures: first, more receivers must be\ndeployed, increasing costs of field operations. Secondly, short arc results\nare sensitive to the geometry of the network, and errors propagate in\nsuccessive extensions based on the same technique.\" Rutscheidt (1974) states\n\"\ndue to the high accuracy obtained with the point positioning mode and\nsince a number of portable receivers are required for the short arc mode,\nthe latter technique is both impractical and uneconomical.\" In reporting on\na program of the National Geodetic Survey (NGS) to establish approximately\n150 Doppler stations within the United States and its possessions in support\nof the readjustment of the North American Datum, Strange, Hothem and White\n(1975) and Hothem (1975) make no mention whatever of the short arc method.\nThis omission is significant for it suggests that no serious consideration\nwas given to the use of the short arc method in a program of such long range\nimportance.\nA11 of the foregoing references indicate a basic lack of comprehension\nof the nature of the short arc method and of its potential for superior\naccuracies. Both the DMA Report and Anderle are simply misleading rather\nthan untrue in their statements regarding the short arc method. While the\nmethod can, indeed, be applied under the conditions they indicate, it is by\nno means restricted to such conditions and, in practice, should not be used\nunder such conditions. Contrary to the statement made by Rutscheidt, the\nshort arc method when properly used can be expected to be from 3 to 5 times\nmore accurate than point positioning and, moreover, can be expected to lead","98\nto a far more efficient field operation. Rutscheidt's statement would be\naccurate if it were reversed. As for the now nearly completed NGS 150-station\nproject, the pity of it is that if the short arc method had been employed at\nthe outset, the field work could have been completed in under 6 months (as\nopposed to over two years) and typical rms accuracies of better than 0.25\nmeter could have been produced for relative positions (as opposed to approxi-\nmately 1.0 meter).\nThese prefatory remarks are, the author trusts, sufficiently unsettling\nto bestir interest in the present paper which is devoted to dispelling unsound\nnotions of widespread currency concerning the short arc method.\nEssentials of the Short Arc Method\nThe short arc method was originated in Brown, Bush, Sibol (1963), (1964).\nAt that time it was referred to as NEO-EMBET (N-Epoch Orbital-Error Best\nEstimate of Trajectory). The method was further elaborated on in Brown\n(1964) and Brown, Hartwell and Stephenson (1965) and was applied to the\nreduction of Geodetic SECOR data in Brown (1966). Almost a decade ago in\nrecommendations to NASA on the formulation of the GEOS-C program (as reported\nin Brown (1967a)) the conclusion was reached \"\na properly designed and\nexecuted short arc dynamic approach to satellite geodesy is by far the most\neffective means for establishing nets of global scope as well as for nets of\na more localized intra-continental character.\" In this same report, some\ntwo years before the emergence of the first Geoceiver it was stated \"\nthe\nquestion arises as to which [ranging] system is to be recommended [in con-\njunction with Geos-C]. Possibilities include Ranging Lasers, Geodetic SECOR,\nGoddard Range & Range Rate System, C-Band Radar and Tranet Doppler (we may\nnow regard Tranet Doppler as an ambiguous ranging system by virtue of the\ndevelopment of the Geoceiver). If only one ranging system were to be per-\nmitted, we would unhesitatingly recommend the Geoceiver over all others. If\nthe Geoceiver, which is now in final development stages, should perform\naccording to specifications (and we can see no reason why it should not), it\ncould well be the most significant development of the decade in geodetic\ntracking systems. The present conference on Doppler positioning may be\nviewed as an affirmation of the validity of this prediction.\nFurther early applications of the short arc method were reported in\nBrown (1967b), (1968). The specific application of the short arc method\nto observations made by Geoceiver was addressed in the computer program\nSAGA (Short Arc Geodetic Adjustment) reported in Brown and Trotter (1969).\nSubsequent applications and refinements of SAGA were reported in Brown\n(1970), Brown and Trotter (1973) and Hadgigeorge (1974). In Brown (1975)\nresults of the first short arc applications using the then newly developed\nJMR-1 receivers were reported. Here, the short arc method used in conjunction\nwith the broadcast ephemeris of the Navy Navigational Satellites demonstrated\nrms accuracies of relative positioning within a net of 5 stations observing\ntypically 15 to 20 passes of 0.91 m in north, 0.21 meters in east and 0.23 m\nin height.\nAs applied to Doppler observations, the short arc method converts the\nmeasured cumulative cycle count Nj corresponding to measured time tj to a","99\nmeasure of slant range rj by means of the following equation derived in Brown\nand Trotter (1969).\n+ (1 + I)T, + a2tj +\n(1)\nThe derivation of this equation is based on the assumption that the frequencies\nof the oscillators of both the satellite and doppler receiver are subject to\nlinear drifts over the duration of a pass governed by expressions of the\nform:\n=\n(2)\n= +\nin which\n= tj-to where to = time at initiation of cycle counting.\nfoo,\nfoo\n= adopted values of satellite and receiver frequencies,\n8f0\nSEO,\n= biases in foo and foo at Tj = 0 (initiation of cycle\ncounting),\nfo,\n= drift rates of f o and f o .\nA11 quantities in the observational equation (1) have explicit physical\ninterpretations. The quantities 10 and Afoo are defined by the expressions\n10\nwavelength of adopted frequency\n= of satellite\noscillator (c=vacuo\nvelocity of light);\nAE00 = foo-foo = adopted value of offset frequency.\nThe six unknown error coefficients ao through a5 are of the form\n= range at initiation of cycle count rescaled according\nto proportional error in adopted wavelength,\n(8f0- f') = error in adopted frequency offset scaled by\n,\n= relative drift rates scaled by 10/2,\nSEO\nfoot\n= proportional bias in frequency of satellite\noscillator,\n= bias in timing synchronization of receiver clock at\ninitiation of cycle count,","100\na5 = error in coefficient used for correction of tropospheric refraction\n(in SAGA f (Ej)=1/[sin Ej + (sin2) + K) 12/11/2 where E. denotes elevation\nangle and K is a constant computed from meteorological data).\nThe final term Ar accounts for the combined value of a number of preprocessing\ncorrections including the following:\n(a) two frequency correction for ionospheric refraction (with some\nreceivers such as the JMR-1 this correction is performed by the\nreceiver itself); ;\n(b) nominal correction for tropospheric refraction;\n(c) correction for propagation delay;\n(d) correction for special relativistic effect (time dilation);\n(e) correction for general relativistic effect (gravitational red\nshift).\nExplicit expressions for each of these precorrections are to be found in\nBrown and Trotter (1969).\nIn many treatments of doppler data reduction equation (1) is replaced\nby the range-difference equation\n(3)\n10\nN--1\n(\nj-1'\n+\n+ higher order terms\nrj-r-1\n=\na1\n-\nj\n(usually neglected)\n+ Dr j - Ar j-1\nwhich follows by replacing j by j-1 in (1) and subtracting the resulting\nexpression from r rj. When the range-difference equation is employed, the\nerror coefficient ao disappears and coefficients beyond a1 (frequency offset)\nare usually not retained, being regarded as negligibly small when time\nintervals Tj-Tj-1 are not too large. In most reductions adopting the range-\ndifference approach random errors of measurement are assumed to be associated\nwith the scaled cycle count difference = 10 (Nj-Nj-1). That is to say,\nthe error in measurement is assumed to reside in ANj and is considered to\nbe serially uncorrelated from one count to another. This assumption is a\ncarryover from reductions appropriate to older Doppler receivers which\ncounted cycles of beat frequency over a succession of short intermittent\nintervals and is not appropriate to the newer receivers (such as Geoceiver\nand its successors) which accumulate cycle counts in strictly continuous and\nunbroken sequences. Nonetheless, equation (3) persists as the basis for\nmany reductions of Doppler observations. In the program SAGA, shortly to be\ndiscussed, options exist for the utilization of either the ranging equation\n(1) or the range-difference equation (3). When the range-difference option\nis exercised, the higher order error coefficients a1 through a5 are retained\nrather than being suppressed as is customarily practices. For purposes of\nfurther exposition consideration will mainly be limited in this paper to","101\ndevelopments based on the exercise of equation (1) as the appropriate obser-\nvational equation for geodetic Doppler receivers.\nInasmuch as in (1) can be replaced by the expression\nrX)()(\n(4)\nwherein\nX.,Y.,Z. jj'jj'j = coordinates of satellite at time\nj'\nX',Y',Z' = coordinates of Doppler receiver,\nequation (1) may be regarded as being functionally of the form\n(5) f(X',Y',Z', , ao, a1, a2, a3, a4, a5; T;) = 0.\nAt this point, it is appropriate to recognize that many satellite passes\nwould ordinarily be employed in the determination of the geodetic position\nof a given station and that on each pass a fresh set of error coefficients\nwould have to be recovered (the possibility of a priori constraints on the\nerror coefficients will be considered later). In view of this, the index 'k'\nis introduced to connote the kth pass of a total of n passes and equation (5)\nis rewritten as\n(6)\nf(X',Y',\nZ',\nTjk)\n=\nk = 1,2, ...,n\nin which nk denotes the number of points observed on the kth pass. If it is\nmomentarily assumed that the orbit is perfectly known, the coordinates Xjk,\nYjk,Zjk will in turn be perfectly known. The system of observational equations\nrepresented by (6) will then consist of - Enk equations in 3+6n unknowns\nk=1\nconsisting of the 3 coordinates of the station X',Y',Z' and a separate set of\n6 error coefficients for each of the n passes. Accordingly, if the entire\nset of s observational equations generated by all n passes is subjected to a\nleast squares adjustment, a set of normal equations of order 3+6n will be\ngenerated. When n is very large, the solution of such a system might seem\nto pose a formidable problem. However, this is not the case, for the coefficient\nmatrix of the normal equations turns out to have the bordered, block-diagonal\nstructure illustrated in Figure 1. In this figure the unshaded blocks consist\nof zeros. A coefficient matrix of such bordered, block-diagonal form is said\nto constitute a first order partitioned system. Schematically, the coefficient","102\nr\nFIGURE 1. Structure of coefficient matrix of normal equations\nfrom simultaneous adjustment of n passes from single station\n(i. e., conventional point positioning approach).\nmatrix N of a first order partitioned system can be represented as\n(7)\nN\nThe sense of this diagram is the following: the horizontal and vertical\narrows represent solid rows and columns, respectively, of elements that are\nnot necessarily zero. The diagonal arow represents a block diagonal array\nof non-zero submatrices. The blank regions between the arrows represent the\nportion of the matrix that are completely filled with zero elements. The\narrow heads are indicative of the fact that the size of the matrix can grow\nwithout preset limit (i.e., an indefinitely large set of passes can be","103\nobserved). This diagrammatic representation of a first order partitioned\nsystem is a convenient point of departure for later considerations of higher\norder partitioned systems arising in conjunction with the short arc method.\nAlthough the dimensions of the first order partitioned system increase\ndirectly with the number of passes n, its solution presents no difficulties\nbecause, as was originally shown in Brown (1958), the block diagonality of\nthe system can be exploited to effect an efficient reduction. It suffices\nhere merely to mention that in the application to the problem at hand, the\nreduction leads ultimately to a collapsed system of normal equations of\norder 3x3 (corresponding to the unknown coordinates of the station) and that\nthe overall computational effort increases only linearly with the number of\npasses n rather than with the cube of n as would otherwise be the case.\nThe reduction just outlined constitutes the essentials of the method of\npoint positioning. However, it should be mentioned that in less rigorous\ntreatments of the method, a strictly simultaneous reduction along the above\nlines is not actually performed. Instead a dichotomous reduction along the\nfollowing lines is employed. First, the range-difference equation (3) is\nadopted with only the frequency offset term a1 of the error model being\nretained. Then, approximate values for the coordinates of the station are\ntemporarily enforced so that a separate least squares solution for a1 can be\nmade for each pass. The value of a so obtained for each of the n passes is\nthen regarded as being perfectly known, and the coordinates of the station\nare treated as unknown in a second least squares solution embracing observa-\ntions from all passes. This generates a 3x3 system of normal equations for\nthe recovery of the coordinates. Should the coordinates thus obtained differ\ntoo greatly from the starting approximations, the above two-step process is\nrepeated. This alternation of reductions is continued as many times as\nneeded to produce satisfactory convergence.\nWith the basics of the method of point positioning having been outlined,\nit is appropriate to proceed to the consideration of the short arc method.\nUnlike point positioning, the short arc method regards the coordinates Xjk'\nYjk,Zjk appearing in (6) as no longer being perfectly known. Instead, they\nare regarded as subject to errors inherited from imperfect orbital elements.\nThus, Xjk,Yjk,Zjk are replaced in (6) by expressions of the form\nXjk = 81 = Y Ok Z 0k' , X Ok ok ok' 'jk'\n(8)\n(X\njk = 82\nZ\nX\n'jk'\n0k\n0k\nOk\nOk'\n0k\n0k\ng3 Z 0k , 0k' ok' ok' 'jk'\nwhere XOK,Yok,20k, XOK,Yok,20k denote the components of position and velocity\nof the satellite at the epoch defined by Tjk = 0 (i.e., they constitute the\nstate vector for the kth pass). This substitution causes (6) to assume the\nfunctional form","104\n(9)\nf\n(X',\nY'\nZ',\nXOK\"Yok\"Zoki\nTj) = 0\n'kk'\n0k'\nOk\n0k\nj=1,2,...,NL\nk=1,2,...,n\nIn the case of Navy Navigational Satellites the elements of the state vector\nare known to a worthwhile degree of accuracy from the broadcast ephemeris\n(typically to better than 25 m for positional components and .02 m/sec for\nvelocity components). This information can be introduced via a supplemental\nset of observational equations of the form\n=\nOk\nYok = Yok\n(10)\n=\n0k\nOk\nk\n1,2,...n\n=\nin which the superscripts '0' connote 'observed' or a priori values of the\nstate vector and the v's are corresponding observational residuals subject\nto a specified 6x6 covariance matrix AK. In addition to a priori constraints\ngoverning certain of the error parameters. These can be introduced by means\nof observational equations of the form\n(11)\n,\nk=1,2,\nn\nin which the residuals of the six a priori error coefficients of the kth pass\nare subject to a specified 6x6 covariance matrix .\nIf the observational equations (9), supplemented by a priori constraints\ngiven by (10) and (11), are subjected to a least squares adjustment, one again\nobtains a first order partitioned system of normal equations, this time of\norder (3+12n)x(3+12n) and of the form indicated in Figure 2. Here, the\nblock diagonal elements are seen to consist of 12x12 matrices each corresponding\nto the six elements of the state vector and the six error coefficients for the\npass. Once again, the algorithm for first order partitioned regression can\nbe applied to effect an efficient solution of the system.\nThe short arc reduction just outlined considers that only a single\nstation participates in the observation of each pass and, as such, may be said\nto constitute point positioning by the short arc method. of considerably\ngreater interest and effectiveness is the general short arc method in which\nany conceivable combination of stations within a given net may observe a given\npass. The observational equations governing this situation are generated from\n(9) by introducing the index i to indicate the ith station in a net of m stations.","105\nFIGURE 2. Structure of coefficient matrix of normal\nequations from simultaneous adjustment of n passes from\nsingle .station when state vectors are allowed freedom\nto adjust (short arc point positioning).\nThis leads to a system of equations of the form\n(12) f(X!,Y!,Z!, 'Ok' Y Ok Z Ok' N. ijk' aoik'a1i ijk'\n1\n=\nj=1,2,\nk=1,2,...,n\nin which it is understood that not all stations necessarily participate in\nthe observation of any given pass (i.e., the Pk - m stations numbered 11,","106\nare considered to observe pass k). Under this formulation a net\n12,\nPk\nembracing a large number of stations, perhaps hundreds, can be generated through\nobservations made by a relatively small number of receivers circulating\nthroughout the net.\nWhat is entailed by the multi-station short arc reduction is best\nindicated by means of a concrete example. Toward this end Figure 3 has been\nprepared to show the form of the coefficient matrix of the normal equations\ngenerated by a simple net of three stations in which all stations observe\nall passes. It will be noted that this system is essentially of the bordered,\nblock-diagonal form characteristic of the first order system. However, the\ndiagonal blocks comprising this system are twice as large as their counter-\nparts in the normal equations for a single-station short arc reduction\n(Figure 2). Moreover, each major diagonal block is itself seen to have a\nfiner structure corresponding to that of a first order partitioned system.\nFor the more general problem involving an indefinitely large number of stations\nthe diagrammatic representation presented in Figure 4 is appropriate. This\nclearly shows that the coefficient matrix of the normal equations from a\nfully general short arc adjustment is a bordered, block-diagonal matrix,\nthe diagonal blocks of which are themselves bordered, block diagonal matrices --\nin other words, a first order partitioned system of first order partitioned\nsystems. A system having such a structure has been termed a second order\npartitioned system.\nIt might be assumed that a direct application of the algorithm for a\nfirst order partitioned system cound be used to effect the reduction of a\nsecond order system. Indeed it could, but as shown in Brown and Trotter (1969),\nsuch a reduction would be grossly inefficient when even a moderate number of\nstations participate in the observation of common passes. Instead, it is\nshown in this reference that a special algorithm tailored to the finer struc-\nture of the second order partitioned system can be developed to effect a\nsolution that remains efficient no matter how many stations participate in the\nobservation of common passes. It is beyond the scope of this paper to go\ninto the algorithm for the reduction of second order partitioned systems. It\nsuffices to mention that the algorithm developed in Brown and Trotter (1969) is\nwhat makes the general multistation short arc reduction computationally\nfeasible. By virtue of the efficient implementation of this algorithm, the\nadvanced short arc program SAGA III (the version proprietary to DBA Systems\nand programmed on DBA's 48K word Sigma 5 computer) can accommodate a total\nnet of several hundred stations in which subnets of as many as 65 stations\ncan participate in the observation of common passes. More generally, on a\ngiven computer the number of stations in the overall net is limited mainly\nby available disk memory, and the number of stations participating on common\npasses is limited mainly by available core memory.\nProperties of the Short Arc Method\nA number of other special features of the short arc reduction as embodied\nin SAGA merit mention (details are to be found in Brown and Trotter (1969))\n(a) a variety of a priori constraints can be imposed on coordinates of\nground stations (offsets, distances, azimuths, elevations, etc.);","107\nStructure of coefficient matrix of normal of n passes. equations from short arc\nFIGURE adjustment 3. of three station net observing set","108\nFIGURE 4. Schematic of coefficient matrix characteristic\nof a second order partitioned system of normal equations.\n(b) errors in successive Doppler observations may be treated as being\nserially correlated by virtue of the exercise of an optional process\ncalled autoregressive feedback (this option assumes particular\nsignificance with the high data rates afforded by short count\nDoppler) ;\n(c) as mentioned earlier, options exist for the exercise of either\nthe range or the range-difference versions of the observational\nequations (the autoregressive feedback option is operative,\nhowever, only in conjunction with the ranging equation) ;\n(d) for mission planning or error analyses the program can be run in\na simulation mode wherein artificial observations are internally\ngenerated to drive the program;\n(e) the program outputs the full covariance matrix of the computed\ncoordinates of all stations in the net (the error propagation is\nfully rigorous taking not only into account the serially correlated\nnoise in each observational channel, but also the a priori covariance\nmatrices of the orbital state vectors and of the coefficients of\nthe error models) ;","109\n(f) from the just mentioned covariance matrix, which reflects accuracies\nof the coordinates in the satellite frame of reference (WGS-72), a\nsecond covariance matrix is also computed to reflect the internal\nor relative accuracies of the coordinates with respect to an\narbitrarily adopted local origin.\nOn the basis of the foregoing outline of the short arc method it can be\nappreciated that the method of point positioning merely corresponds to that\nlimited and special case of the single-station short arc reduction in which\nthe orbital state vector is regarded as being totally free of error (i.e.,\nthe a priori covariance matrices of the orbital state vectors are treated as\nnull matrices). This fact cannot be emphasized too strongly, for the mis-\nconceptions mentioned in the introduction arise from a failure to comprehend\nthis reality. How can the short arc method be criticized relative to the\nmethod of point positioning when the latter is an almost trivial special\ncase of the former? The reason stems from the fact that the short arc method\ncan be exercised, if so desired, without recourse to a priori orbital con-\nstraints by virtue of feature (a) listed above. When this is done, it\nindeed becomes necessary to exercise constraints on three stations sufficient\nto define uniquely the coordinate system being used. This special capability\nor option of the short arc reduction has been misconstrued as being an\nessential requirement of the method. It is not. When worthwhile a priori\norbital constraints are available, as with either the NAG broadcast ephemeris\nor the NWL precise ephemeris, no constraints need be applied to the coordinates\nof the stations. Nor does the short arc reduction require a multiplicity of\nreceivers; it can be applied to isolated observations made by a single\nreceiver either in the conventional point positioning mode (orbits enforced)\nor in the decidedly superior short arc point positioning mode in which errors\nin orbital state vectors are properly taken into account. Be this as it may,\nthe short arc method is used to best advantage when two or more stations\nobserve passes in common, for relative accuracies of a high order can be then\nobtained even with ephemerides of fairly poor accuracy. Here, the short arc\nmethod enjoys all of the benefits of (and more) of the method of translocation\nwithout suffering any of its many disadvantages. When, for instance, the NAG\nbroadcast ephemeris with its typical rms accuracies of 25 m in-track, 17 m\ncross-track and 8 m radial is exercised in a properly designed short arc net,\nrelative accuracies on the order of a few tenths of a meter are to be expected\nfor the coordinates of stations observing 30 to 40 passes in common. By\ncontrast, when the method of point positioning is employed in conjunction with\nthe NWL precise ephemeris (typical rms accuracies of about 3 m) accuracies of\nrelative positioning on the order of one meter are to be expected from the\nreduction of 30 to 40 passes. In the former case, the necessary observations\ncould normally be expected to be gathered over a 2 to 3 day period, whereas\nin the latter case some 7 to 10 days may be required. Thus not only is the\nshort arc method using the broadcast ephemeris some 3 to 5 times more accurate\nin relative positioning than the method of point position using the precise\nephemeris, but also the data gathering time is only one third as long. Hence,\nconsiderations of both accuracy and economy overwhelmingly favor the short\narc method. In the remainder of this paper material supporting the above\ncontention will be presented.","110\nAnother Look at the DOD Geoceiver Test Program\nIt seems likely that much of the misunderstanding concerning the short\narc method can be traced to the DOD Geoceiver Test Program (DMA Report 0001).\nHere, emphasis was placed almost totally on the use of the method without\nbenefit of a priori orbital constraints. Thus, the coordinate system was\ndefined though the exercise of various baseline constraints with the inevitable\nresult that errors in the coordinates of the stations used to define the\nconstraints were propagated throughout the short arc net (a shortcoming\nemphasized in the remark of Anderle quoted in the introduction). Moreover,\nin 10 of the 11 reductions reported, a preliminary version of SAGA without\ncycle count editing and several other refinements was exercised. However,\nthe last of the reported reductions was performed with a refined version of\nSAGA and, moreover, exercised the precise ephemeris with a priori orbital\nconstraints of 5 meters in position and .005 meters in velocity (one sigma)\non 17 out of the total of 70 passes employed (the remaining 53 passes used\nthe NAG ephemeris and were carried without a priori orbital constraints).\nThe resulting rms discrepancies in latitude, longitude and height for the\ncombined results of Phases I and II of the test were reported in Table F-12\nof the report to be 1.1m, 1.3m and 1.7m, respectively. This result was\nachieved following a 7 parameter similarity transformation (three translations,\nthree rotations and scale) relating the short arc survey with the High\nPrecision Geodimeter Traverse (HPGT). The average number of passes per\nstation was about 31 and ranged from a low of 9 (for two stations) and a high\nof just over 60 (for two stations). Comparable results for the solution based\non point positioning using the precise ephemeris (Table D-4 of the report)\nwere rms discrepancies of 1.9m, 2.2m and 1.4m, respectively, from reductions\nhaving an average of 78 passes per station (low 23, high 100). Thus, overall,\nthe short arc method yielded moderately higher accuracies from less than half\nthe average number of passes (of which only half, again, were exercised with\na priori orbital constraints) Unfortunately, attention was not called to\nthis fact in the report, and the presentation was dominated by a mass of\nshort arc results based on unsound premises. As a result, the full power\nand flexibility of the short arc method failed to emerge from the study.\nThis situation was later rectified by Hadgigeorge (1974) who redid the\nreductions for Phase I (Figure 5) with the full exercise of appropriate\na priori constraints on orbital state vectors derived from the precise\nephemeris (one sigma constraints of 5m in position and .005 m/sec in velocity\nwere exercised). His main results which are reproduced here as Tables 1\nand 2 yielded rms discrepancies relative to the HPGT following a seven\nparameter similarity transformation of .94m, .92m and .79m, respectively, in\nX, Y, and Z. These results were obtained from an average of 21 passes per\nstation (low 9, high 44) and compare very closely with the corresponding\npoint positioning rms discrepancies of .83, .89 and .92m, respectively, as\nindicated in Table D-3 of the DMA report (discrepancies there are given in\nterms of latitude, longitude and height). The point positioning results,\nit should be noted, were obtained from an average of 107 passes per station\nranging from a low of 34 to a high of 206. It is perhaps significant that\nboth solutions yield virtually identical RSS errors (i.e., [(94) + (.92) 2\n+\n(.79) 22 [.83) 2 + (.89) 2 + (.92) = 1.53m). This suggests that the\ndiscrepancies are dominated by errors in Geodimeter traverse. It will be","111\nTable 1. Differences in Geoceiver Station Positions, SAGA Solution Results\nMinus Modified CCD Survey (from Hadgigeorge (1974))\nNo. of\nStation No.\nDx(m)\nDy(m)\n(m)\nox (m)\noy(m)\noz (m)\nPasses\n10003\n-0.00\n0.00\n0.00\n0.03\n0.02\n0.03\n44\n10006\n0.77\n-0.45\n2.96\n0.54\n0.38\n0.31\n11\n10018\n-0.53\n0.99\n0.89\n0.47\n0.27\n0.26\n25\n10019\n-3.13\n-0.59\n1.27\n0.32\n0.22\n0.19\n28\n10020\n-0.82\n-0,43\n0.98\n0.47\n0.29\n0.27\n9\n10022\n-1.40\n0.47\n-0.59\n0.26\n0.17\n0.18\n14\n10023\n-1.21\n-0.78\n0.15\n0.24\n0.15\n0.17\n16\n20000\n-1.35\n2.02\n0.70\n0.56\n0.45\n0.38\n21\n20001\n-1.27\n1.94\n0.58\n0,56\n0.45\n0.38\n21\n20015\n-0.03\n2.79\n-0.91\n0.53\n0.39\n0.30\n19\n20016\n-0.89\n-0.20\n0.12\n0.19\n0.12\n0.14\n30\n30025\n-3.11\n2.44\n0.29\n0.45\n0.35\n0.31\n12\n30026\n-1.80\n0.79\n1.90\n0.41\n0.30\n0.26\n19\nMeans:\n-1.23\n0.75\n0.70\n0.40\n0.31\n0.26\n20.6\nTable 2. Datum Shift Discrepancy Vectors and Transformation Parameters\n(from Hadgigeorge (1974)).\nStation No.\nAx (m)\nDy (m)\nDz (m)\n10003\n-0.74\n0.43\n0.39\n10006\n-2.09\n-1.02\n-1.90\n10018\n0.04\n-1.25\n0.55\n10019\n1,63\n0.84\n-0,33\n10020\n-0.50\n0.94\n-0.20\n10022\n0.50\n0.20\n1.06\n10023\n0.44\n1.49\n0.22\n20000\n-0.31\n-0.35\n0.20\n20001\n-0.39\n-0.24\n0.31\n20015\n-0.70\n-0.49\n1.07\n20016\n0.33\n1.17\n0.08\n30025\n1.53\n-1.60\n0.64\n30026\n0.27\n-0.12\n-0.99\n0.942\nrms\n0.919\n0.786\nAlpha = -0.36 t 0. 11 (arc sec)\nOmega = 0.32 + 0.14 (arc sec)\nKappa = 0.04 t 0.07 (arc sec)\nScale = 1.0000001 I 0.4x 10-6","112\nCOLUMBUS\nFRANKTON\n<30026\n10019\nHOWARD Co. 20000\nMETAMORA\nBELTSVILLE 20001\n30028\nGREENVILLE\n30027\nBLOOMFIELD\nTIPTON\nMARYSVILLE 30025\n10006\nSUMMIT\n10020\n10021\nIUKA\nGREENVILLE\n10022\n10003\n@\nMATHISTON\n10023\nWOODBINE\n20015\nLEGEND\nCOLUMBIA\n20016\nFIXED GEOCEIVER\nJONESTOWN\nMOBILE GEOCEIVER\n10018\nCOMPLETED GEODIMETER OBSERVATIONS (HPGT)\nPLANNED GEODIMETER OBSERVATIONS (HPGT)\nFIGURE 5. Layout of network for DoD Geoceiver test, Phase I.\nnoted from Table 1 that the analytical error propagation performed in con-\njunction with the short arc adjustment led to estimated standard deviations\nin X, Y, Z of e .40, .31 and .26 m, respectively. If these values are assumed\nto be valid, it would follow from the rms discrepancies in Table 2 (.942,\n.919 and .786 m) that standard deviations of the errors of the Geodimeter\ntraverse are approximately [ ( . .942) 2 - (.40) 2 2 = .85, [ (.919) 2 - (.68)\n2 1 1/2\n.86\n=\nand [(786)2 - (.26) 2 ] = .74 m, in X, Y, and z, respectively.\nIt is noteworthy that the scale resulting from the transformation indicated\nthe bottom of Table 2 is insignificantly different from unity (the differ-\nat\nence is 0.1 + 0.4 ppm). Insofar as Phase I (the Eastern half of the U.S.)\nof the Geoceiver Test Program is concerned, then, Doppler scale resulting from\nthe short arc method is in virtually perfect agreement with terrestrial\n(geodimeter) scale. On the other hand, the short arc reduction reported in\nTable F-12 of DMA 0001 for the combination of Phases I and II (Eastern and\nWestern halves of U.S.) yields a difference in scale of 1.8 ppm (no standard\ndeviation given) and is thus in good agreement with the value of 1.5 + 0.3 ppm\nreported in Table 5 of Strange, Hothem and White (1975). The fact that short\narc results from Phase I failed to indicate a significant difference between\nDoppler and terrestrial scales, whereas the short arc results from the com-\nbination of Phase I and II do indicate a significant difference suggests that\nsystematic errors in the HPGT for the Western U.S. may well be the source of\nthe apparent scale discrepancy. Thus, the DOD tests do not necessarily","113\nestablish the existence of a scale error in Doppler surveying when the short\narc method is employed. While the VLBI comparisons reported in Table 6 of\nStrange, Hothem and White (1975), do indeed establish a significant scale\nbias of about 1.0 ppm for point positioning using the precise ephemeris, it\nremains to be shown that such is also inherent in the short arc method.\nTo demonstrate more vividly the power of the short arc method, Hadgi-\ngeorge also performed a reduction leading to the results listed below in\nTables 3 and 4. Here, the reduction was limited to the subset of passes of\nthe original reduction that were observed by five or more stations in common\nwith Station 10003. As can be seen from Table 3, this selection led to an\naverage of about six passes per station, with three of the stations having\nonly four passes. Yet, as can be seen from Table 4, rms discrepancies in\nX, Y, Z of only 1.26, 1.20 and 1.21 m were obtained. If allowance is made\nfor the rms contribution of errors in the geodimeter traverse as estimated\nabove (.85, .86 and .74 m), the portion of these discrepancies attributable\nto Doppler become .93, .84 and .92 m in X, Y, and Z. This demonstrates that\nwhen the short arc method is used in conjunction with the precise ephemeris,\nlocal coordinates having standard deviations of better than one meter can be\nexpected from the reduction of only 6 passes. With point positioning using\nthe precise ephemeris the reduction of some 40 passes is required to produce\ncomparable results. When only 6 passes are used, it follows from Figure 13\nand 14 of DMA 0001 that rms accuracies of about 3 meters are to be expected.\nCompared with the short arc method, then, point positioning may be said to\nhave a statistical efficiency of only about 10% with respect to relative\npositioning.\nThe foregoing results demonstrate that when the data gathered under the\nDOD Geoceiver Test are subjected to a proper analysis, the superiority of the\nshort arc method with respect to accuracies emerges as overwhelming and indis-\nputable. The method of point positioning must be recognized for what it is,\nnamely the special case of the short arc method in which errors in the orbital\nephemeris are simply ignored. But the errors are there and they are significant\neven with the precise ephemeris. Ignoring them exacts severe penalties not\nonly in accuracies but also, as will be seen presently, in gross inefficiencies\nin field operations.\nShort Arc Accuracies Over Short Distances\nA basic problem with the DOD Geoceiver Test is that the Geoceiver Traverse\nturned out to be os insufficient accuracy to serve as a definitive standard\nfor the evaluation of short arc accuracies for stations separated by distances\nof mahy hundreds of kilometers. On the other hand, over relatively short\ndistances of a few tens of kilometers accuracies of a few centimeters can be\nexpected from a geodimeter traverse. Here, the geodimeter traverse can\nprovide an unassailable standard. Moreover, in many potential commercial\napplications of Doppler surveying separations of tens of kilometers rather\nthan hundreds of kilometers are of primary interest. In view of this, DBA\nrecently undertook a simple 48 hour test of the short arc method involving a\npair of stations located on the Central Florida Geodimeter net and separated\nby about 30 kilometers. The objective was to determine whether Doppler sur-\nveying by the short arc method could compete over such intermediate distances","114\nTable 3. Differences in Geoceiver Station Positions, SAGA Solution Results\nMinus Modified CCD Survey (from Hadgigeorge (1974)).\nNo. of\n0x(m)\nDy(m)\nDz (m)\n(m)\noy(m)\noz (m)\nStation No.\nPasses\n10003\n0.00\n-0.00\n0.00\n0.03\n0.02\n0.03\n12\n10006\n1.17\n2.25\n0.03\n0,71\n0.52\n0.35\n4\n10018\n-1.25\n1.60\n0.90\n0.67\n0.45\n0.26\n5\n10019\n-3.79\n-0.86\n1.90\n0.54\n0.28\n0.27\n7\n0.78\n10022\n-3.29\n-0.44\n0.38\n0.23\n0.25\n5\n10023\n-0.69\n-0.45\n0.52\n0.36\n0.23\n0.23\n6\n20000\n-2.46\n1.18\n0.39\n0.74\n0.50\n0.44\n4\n20001\n-2.42\n1.14\n0.33\n0.74\n0.50\n0.44\n7\n20015\n-4.00\n3.31\n-2.29\n1.26\n0.66\n0.57\n5\n20016\n-2.74\n-0.15\n1.29\n0.28\n0.19\n0.20\n9\n30025\n-2.37\n1.56\n0.17\n0.66\n0.37\n0.38\n4\n30026\n-2.88\n0.34\n2.76\n0.58\n0.32\n0.30\n8\nMeans:\n-2.06\n0.89\n0.46\n0.64\n0.39\n0.34\n6.4\nTable 4. Datum Shift Discrepancy Vectors and Transformation Parameters\n(from Hadgigeorge (1974))\nStation No.\n0x(m)\nAy(m)\nDz(m)\n10003\n-1.71\n1.15\n0.45\n10006\n-2.49\n-2.15\n0.48\n10018\n0.08\n-0.30\n-0.30\n10019\n1.61\n1.22\n-1.49\n10022\n1.36\n0.27\n0.86\n10023\n-1.16\n1.64\n-0.08\n20000\n-0.33\n-0.51\n0.07\n20001\n-0.38\n-0.45\n0.14\n20015\n1.61\n-1.55\n2.77\n20016\n0.97\n1.66\n-0.81\n30025\n-0.08\n-1.10\n0.25\n30026\n0.52\n0.11\n-2.35\n1.258\n1.195\n1.206\nrms\nAlpha = -0.07 I 0.14 (arc sec)\nOmega = 0.22 I 0.18 (are sec)\nKappa & 0.004 I 0. 10 (arc sec)\nScale = 1.0000008 I 0.5 x 10-6","115\nwith conventional ground traversing performed to normal first order standards\nof 1:50,000. A JMR-1 receiver was placed at each of the two stations indicated\nin Figure 6 and were operated continuously for a period of 48 hours in Jan-\nuary 1976. A meterograph at each station provided continuous readings of\npressure, temperature and humidity for use in making precorrections for trop-\nospheric refraction. The cutoff elevation angle of 10° was selected in the\nreduction and the short count data rate of nominally 1 point/4.6 sec was\nadopted. All reducible passes, a total of 25 in all, gathered during the 48\nhour period were carried in the short arc solution effected by SAGA III.\nOnly the broadcast ephemeris was used in the reduction with one sigma a priori\nconstraints of 25, 17 and 8 m being exercised on positional components in\nthe in-track, cross-track and radial directions, respectively, and constraints\nof 0.02 m/sec being exercised on the corresponding components of velocity.\nThe main results of the reduction are presented in Table 5.\nTABLE 5. Results of 48 hour, 2 station, Central\nFlorida test of short arc method.\nAN\nAE\nAU\nStation\n(meters)\n(meters)\n(meters)\n1\n- .200\n- .092\n- .056\n2\n+ .200\n.092\n.056\nRMS\n.200\n.092\n.056\nHere are listed the discrepancies between Doppler and terrestrial surveys that\nremain following the removal of the mean datum translation common to both\nstations. The total rms discrepancy for all three components turns out to\nbe {[(200) 2 + (.092) 2 + (.056) 2 ]/3}} = 131 m. The distance between the\nstations according to the terrestrial survey is 29,360.880 m as compared with\na distance of 29,360.940 m according to the Doppler survey. This discrepancy\nof .060 m is fortuitously small and corresponds to a proportional accuracy of\n1:489,000 in the length of the baseline. In the horizontal direction perpen-\ndicular to the baseline the discrepancy is greater, amounting to .395 m,\nwhich corresponds to a proportional accuracy of 1:74,000. These results\nindicate, then, that Doppler surveying by the short arc method using the\nbroadcast ephemeris and as few as 25 passes can produce accuracies comparable\nto those to be expected from first order ground traversing over distances as\nshort as 20 km.\nThe reduction just reported exercised the range-difference option of\nSAGA III. Very nearly the same results were obtained with the exercise of\nthe ranging option. The reason for reporting results from the former here\nis to facilitate comparisons of rms values of residuals, for NGS and other\nU.S. governmental agencies employ the range-difference approach. Hothem\n(1975) of NGS, for example, states \"The standard error of unit weight 100)\nfor the observational residuals of the solution results should range from","116\n107\n1106\nLOKOSEE\nADAMS\nTRANSVERSE MERCATOR PROJECTION\nFIGURE 6. Illustrating locations in Central Florida Geoceiver net of pair of\nstations (LOKOSEE and ADAMS) used in 48 hour test of short are Doppler positioning.\n11 to .20 meter. For marginal data, the 00 is from about .21 to . .30 meters. \"\nIn Table C-7 of DMA 0001 the rms values of the residuals range from a low\n13.4 cm to a high of 19.3 cm and average 15.7 cm. By comparison, the results\nfrom the Central Florida test listed in Table 6 show that rms values of\nresiduals from the short arc method are considerably smaller. For Station 1\nthey range from a low of 2.6 cm and a high of 4.7 cm and average 3.5 cm; for\nStation 2 the low is 3.8 cm, the high is 7.1 cm and the average is 5.0 cm.\nThe larger values for Station 2 can be attributed to the particular receiver\nused rather than the environment, because the receiver has consistently been\nfound to produce somewhat noiser data than the norm for JMR-1 receivers.\nResiduals obtained from the short arc method with Geoceivers tend to be\ncomparable with those obtained from JMR receivers, with rms values of residuals\nof range differences varying typically between 4 and 8 cm. For the most part,\nthen, the method of point positioning yields observational residuals having\nstandard deviations ranging from 3 to 5 times larger than those produced by\nthe short arc method. In this regard, the short arc method is again superior\nby a wide margin.\nField Operations for Short Arc Methods\nThe full potential of the short arc method can be realized only if field\noperations are specifically designed to exploit its superior capability for\nrelative positioning. As a minimum this generally means that one station\n(the base station) should be continuously occupied throughout a project while\none or more additional receivers circulate throughout the remaining stations\nfor relatively short period of occupancy. In this way, all stations become","TABLE 6. Summary of pass statistics from special 48 hour, two-station, Central Florida test.\nRMS Value of\nResiduals\n5.0 cm\n5.1 cm\n4.7\n4.5\n4.5\n4.5\n4.9\n4.4\n4.5\n4.5\n5.3\n5.2\n5.4\n5.4\n4.8\n5.1\n5.1\n3.8\n4.8\n5.1\n4.6\n5.2\n7.0\n4.6\n7.1\n5.1\nSTATION 2\nNumber of\n126.4\nPoints\n166\n165\n164\n148\n71\n145\n96\n163\n77\n143\n136\n124\n62\n108\n83\n164\n109\n102\n109\n122\n138\n127\n118\n180\n141\nRMS Value of\nResiduals\n3.5 cm\n3.9 cm\n3.8\n3.4\n3.8\n3.5\n3.2\n2.7\n3.9\n2.9\n4.6\n3.6\n3.6\n3.7\n4.0\n2.5\n3.8\n2.7\n3.8\n3.2\n3.1\n4.5\n4.7\n3.5\n3.5\n2.6\nSTATION 1\nNumber of\n127.8\nPoints\n70\n142\n163\n148\n166\n112\n73\n145\n176\n123\n64\n121\n106\n87\n166\n143\n141\n99\n133\n133\n137\n153\n95\n118\n181\nMAX. EL.\nANGLE\n12.5°\n36.9°\n33.6\n76.5\n34.0\n40.6\n67.6\n19.9\n56.5\n31.9\n67.3\n31.8\n13.2\n60.2\n13.1\n13.6\n56.3\n35.2\n16.9\n27.2\n24.3\n35.3\n45.7\n40.4\n20.3\n48.1\n(Day, Hour, Satellite No. )\nMEANS:\n12\n19\n18\n19\n20\n13\n20\n14\n13\n12\n18\n19\n20\n20\n19\n14\n13\n14\n18\n13\n20\n14\n13\n14\n19\nPASS\n00h\n03\n03\n05\n06\n06\n07\n08\n12\n15\n16\n18\n00\n06\n01\n15\n07\n08\n14\n17\n17\n18\n19\n20\n01\n15d\n15\n15\n15\n15\n15\n15\n15\n15\n15\n15\n15\n15\n15\n16\n16\n16\n16\n16\n16\n16\n16\n16\n16\n17","118\ninterrelated through connections to the base station. In projects spanning\nlarge countries more than one base station may be called for in an optimal\ndesign. Principles appropriate to the design of short arc nets are covered\nat length in Brown (1976) Later in the present paper, consideration will be\ngiven to a short arc net designed for coverage of the conterminous Unites\nStates.\nFeatures of typical field operations appropriate to the short arc method\nare best brought out by consideration of a specific example concerning a\nproject only recently executed in a Middle Eastern country by DBA under sub-\ncontract to another firm. To protect the anonymity of the client the name\nof the country will not be mentioned in this account. Suffice it to mention\nthat the area of concern in the project is mainly desert extending about\n800 km in one direction and 1400 km in the other -- an overall area very nearly\nthe same as that covered by Phase I of the DOD Geoceiver Test. Altogether,\na total of 16 stations were to be located under the contract to an accuracy\nof 3.0 m (one sigma) . The layout of the net is shown in Figure 7. The\ncentrally located station designated as Station 001 was selected to serve as\nbase station and was equipped with two JMR-1 receivers, the second serving\nboth as backup and as an available spare, should such be needed. Two additional\nfield parties each equipped with a single JMR-1 receiver traveled throughout\nthe country occupying the remaining stations for periods mostly of 36 to 48\nhours. Two of the stations were accessible (as a practical matter) only by\n002\n008\n009\n016\n015\n007\n003\n014\n011\n005\n001\n004\n010\n006\n012\n013\n0\n100\n200\n300\n400\n500 km\nFIGURE 7. Layout of stations in short arc net observed in Middle Eastern country.","119\nairplane and most were rather difficult to reach by land. Thus, the high\ncost of logistics dictated an operation of highest practicable efficiency.\nMinimum operational requirements called for the acquisition of at least 10\npasses at each station in common with the base station. To provide an\nadequate margin of safety, each mobile party, guided by satellite alerts\nprepared in advance, stayed sufficiently long to gather 15 to 20 passes\njudged to be of good quality. Since communications did not exist between\nparties no attempt was made at precise coordination of moves beyond a pair\nof preplanned rendezvous at which data tapes were dispatched to the base\ncamp for readout and evaluation. A graphical chronology of occupancy of\nstations is shown in Figure 8 and a summary of potentially reducible passes\nis provided in Table 7. As can be seen from Figure 8 the field operation\nconsumed a total of 30 days, during which, as it turned out (Table 7),\nabout twice as much data was gathered as was actually targeted for reduction.\nBecause the project was strictly commercial rather than scientific, only as\nmuch data was reduced as had been planned on in the original bidding. A\nschedule of the passes selected for reduction is provided in Table 8. With\nonly two exceptions where 12 and 13 passes were reduced the policy of reducing\nonly 10 passes per mobile station was strictly followed. In every case, all\nselected passes were in common with the base station and, wherever possible,\nwere also in common with the other mobile station. Thus most reduced passes\nwere observed simultaneously by three stations.\nObservations from all 16 stations were adjusted simultaneously in a\nrigorous short arc adjustment. The results of primary interest for present\npurposes consist of the results of the analytical error propagation summarized\nin Table 9. These serve to illustrate an important and as yet not widely\nappreciated point concerning the short arc method. It will be noted that two\nsets of figures are quoted in Table 9, one designated as being representative\nof geocentric accuracies and the other as being representative of relative\naccuracies. The former apply to the coordinates of the stations expressed in\nthe satellite frame of reference, namely WGS-72, whereas the latter refer to a\nlocal net in which the origin is translated to the base station which is then\nconsidered to be error free. It is particularly to be noted that all of the\nmobile stations have geocentric accuracies that are nearly the same as those\ncharacterizing those of the base station. All, in effect, benefit directly\nfrom the large number of passes (96) carried in the reduction for the base\nstation. By virtue of this, the geocentric accuracies of the base station\nare transmitted with but little dilution to all stations in the net. Relative\naccuracies are seen from Table 9 to be considerably higher than geocentric\naccuracies and subject to greater variability in East and Up components. This\nvariability would largely have been eliminated had a pair of base stations\nbeen employed, one centered in the eastern half of the area and one centered\nin the western half. Under these circumstances, rather uniform, relative\naccuracies of under 0.4 meters (one sigma) could have been expected in all\nthree components from the reduction of about 10 passes per station from each\nmobile unit. This was unnecessary in the present instance, inasmuch as the\nrelatively modest required accuracies of 3 meters were already bettered by\na substantial margin.","003\n004\n005\n005\n008\n007","121\nTABLE 7. Summary of raw data collected on Middle East project.\nPERIOD OCCUPIED\nTOTAL NUMBER\nNUMBER OF PASSES OBSERVED:\nSTATION\nOF RECORDED\n(a)\n(b)\n(c)\nFrom\nTo\nPASSES\nBy Single Station\nIn Common With\nIn Common With\nOnly\nOne Other Sta.\nTwo Other Sta\n4\n14\"\nd\n12\n128\n157\n001\n450\n190\n173\n87\n002\n128\n12\n130\n09\n43\n8\n16\n19\n003\n128\n19\n130 05\n30\n2\n9\n19\n004\n130\n15\n132 09\n25\n7\n14\n4\n005\n131\n15\n134 09\n52\n10\n25\n17\n006\n133\n10\n134 14\n24\n2\n9\n13\n007\n135 19\n137\n05\n24\n10\n14\n0\n008\n140 08\n141\n17\n28\n2\n26\n0\n009\n143\n12\n145\n09\n27\n1\n11\n15\n010\n143\n14\n146\n07\n54\n16\n20\n18\n011\n145\n21\n148\n07\n33\n14\n8\n11\n012\n147\n16\n150\n07\n28\n10\n10\n8\n151 11\n013\n153\n04\n34\n10\n10\n14\n151\n15\n153\n014\n09\n29\n1\n14\n14\n015\n153\n14\n155\n09\n34\n13\n13\n8\n016\n154 20\n157\n01\n45\n19\n18\n8\nTABLE 8. Summary of passes selected for final reduction *\nSTATION\nPASSES\nNUMBER OF PASSES REDUCED IN COMMON\nUSED*\nWITH FOLLOWING STATIONS\n1\n2\n3\n1\n5\n6\n7\n8\n9\n10\n11\n12\n13\n14\n15\n16\n001\n96\n10 10 10 12 10 10 10 10 13 10 10 10 10 10 10\n002\n10\n10\n10\n003\n10\n10\n10\n004\n10\n10\n2\n005\n12\n12\n?\n10\n006\n10\n10\n10\n007\n10\n10\n008\n10\n10\n009\n10\n10\n10\n010\n13\n13\n10\n3\n011\n10\n10\n3\n7\n012\n10\n10\n7\n013\n10\n10\n9\n014\n10\n10\n9\n015\n10\n10\n8\n016\n10\n10\n8\n\"In final simultaneous short are reduction of panuca from all 10 stations.","122\nTABLE 9. Gencentric and relative accuracies in meters of Doppler coordinates for Middle East net.\nGEOCENTRIC ACCURACIES (CNE SIGMA) *\nRELATIVE ACCURACIES (ONE SIGMA)\n**\nSTATION\nC X\no\no\no\na\na\nor\nO 2\no\nY\nZ\no o\no\nN\nU\nX\nN\nU\n001\n1.21\n1.64\n1.08\n1.11\n1.67\n1.14\n.00\n.00\n.00\n.00\n.00\n.00\n002\n1.48\n1.81\n1.25\n1.19\n1.85\n1.48\n.90\n.87\n.64\n.46\n.87\n1.01\n003\n1.27\n1.67\n1.14\n1.15\n1.71\n1.22\n.44\n.41\n.37\n.33\n.42\n.45\n004\n1.55\n1.71\n1.19\n1.16\n1.84\n1.41\n.96\n.66\n.51\n.38\n.88\n.84\n005\n1.55\n1.81\n1.23\n1.18\n1.93\n1.43\n1.07\n.95\n.66\n.48\n1.03\n1.04\n006\n1.39\n1.69\n1.17\n1.17\n1.77\n1.29\n.74\n.64\n.48\n.43\n.76\n.66\n007\n1.29.\n1.75\n1.13\n1.17\n1.78\n1.21\n.46\n.59\n.39\n.37\n.58\n.49\n008\n1.50\n2.16\n1.27\n1.18\n2.10\n1.65\n.96\n1.50\n.76\n.46\n1.41\n1.25\n009\n1.41\n1.89\n1.20\n1.19\n1.87\n1.45\n.86\n1.05\n.65\n.49\n1.00\n1.02\n010\n1.34\n1.77\n1.16\n1.15\n1.76\n1.37\n.65\n.81\n.50\n.38\n.73\n.80\n011\n1.41\n1.92\n1.22\n1.21\n1.91\n1.44\n.95\n1.10\n.70\n.52\n1.07\n1.08\n012\n1.42\n1.96\n1.25\n1.22\n1.92\n1.49\n.92\n1.23\n.71\n.55\n1.16\n1.10\n013\n1.39\n1.85\n1.24\n1.19\n1.85\n1.43\n.72\n.88\n.55\n.44\n.84\n.84\n014\n1.42\n1.85\n1.26\n1.18\n1.88\n1.45\n.86\n.85\n.62\n.45\n.86\n.95\n015\n1.40\n1.85\n1.24\n1.19\n1.86\n1.44\n.89\n.89\n.65\n.48\n.86\n1.02\n016\n1.33\n1.81\n1.20\n1.18\n1.82\n1.33\n.74\n.80\n.56\n.46\n.79\n.82\n* with respect to WGS-73.\nwith respect to local origin colnoiding with base station (001).\nThe foregoing results provide the answer to those who concede the superior\naccuracies of the short arc method for relative positioning but do not appreciate\nits accompanying superiority for geocentric positioning. The fact is that the\nhigh geocentric accuracies obtained for the base station (by virtue of the\nlarge number of passes observed and reduced) are transferred directly to all\nother stations with but slight dilution in a properly designed short arc net.\nWhen the base station together with at least two well-separated mobile stations\nparticipate in generating a short arc net, geocentric accuracies (in meters) to\nbe expected for the base station from the reduction of a total of N different\npasses using the broadcast ephemeris is generally given to within + 15% by the\nof thumb : Oy a Z 2 15/VN. Geocentric accuracies of the other stations\nrule\ndepend on the strength of the connection to the base station. With moderately\nstrong connections leading to relative accuracies that are appreciably higher\nthan the geocentric accuracies of the base station one can expect very little\ndilution in the transfer of geocentric accuracies throughout the net. Thus it\nis possible to design a short arc net in which geocentric and relative accuracies\nare both high and quite uniform.\nOrbital Adjustments\nAs mentioned earlier, the distinguishing feature of the short arc method\nis that specific and appropriate consideration is given to errors in the\nephemerides employed. Accordingly, it is necessary to exercise a precise","123\norbital integrator and associated solution of the variational equations in\norder to effect the rigorous adjustment of the elements of the a priori state\nvector. Although the capacity exists in SAGA III to consider spherical\nharmonics through degree and order n,m)=(16,16), it has been found as a\npractical matter sufficient to truncate the gravity field at the relatively\nlow degree and order (n,m)=(4,4). The following procedure is used in SAGA\nIII to generate starting elements of the state vector from the broadcast\nephemeris:\n(a) from up to eight consecutive two minute messages of the broadcast\nephemeris the inertial coordinates X,Y,Z of the orbit are computed\nat each two minute mark;\n(b) separate unconstrained polynomials in T (time), typically of fifth\nor sixth degree, are fitted by least squares to the values of X, Y\nand z, respectively, generated in the previous step;\n(c) the polynomials and derivatives are evaluated at the chosen epoch\n(t=t-to=0) to generate a set of initial approximations X0, Yo, Z0,\nX0,Yo,Zo to the elements of the state vector;\n(d) these initial approximations then serve as starting values in a\nsecondary process of refinement wherein a rigorous least squares\nfit is made of the linearized equations of motion to the values\nof X, Y, Z generated in step (a) ;\n(e) the rigorous orbital fitting process performed under (d) is\niterated to convergence and the resulting final state vector\nis\nretained to serve as the a priori state vector to be used in the\nsubsequent short arc adjustment;\n(f)\nas a measure of quality control, the final residuals in X, Y, Z\nfrom the orbital fit are automatically examined for acceptability\n(rms values typically range from 3 to 5 meters for good data, this\nbeing consistent with expectations from the truncated word lengths\nof the satellite message).\nThe a priori state vectors for those passes found to be acceptable by the\nabove preliminary screening process are then exercised in the short arc\nadjustment with appropriate a priori constraints, currently taken as the\naforementioned 25, 17 and 8 m for in-track, cross-track and radial components\nof position and .02 m/sec for all three components of velocity. Because the\nelements of the state vector are thus subject to constrained adjustment in\nthe short arc adjustment, one obtains corrections to the a priori elements.\nThese, of course, should ideally be consistent with the imposed a priori\ncovariance matrices and thus provide a special check on the acceptability of\nthe adjustment. Those passes that turn out to require corrections that are\nexcessively out of line with expectations are rejected in the final reduction.\nA specific illustration of corrections to the positional components of\nthe state vector is given in Table 10, which is based on the 57 passes reduced\nfor the final two week period of the operation discussed in the preceding","124\nsection. Listed in the table are the u,v,w (in-track, cross-track, and\nradial) corrections to the positional components of the state vector and\nthe corresponding standard deviations of the a posteriori values of these\ncomponents. The rms values of the corrections in V and W of 14.0 and 10.7 m\nare reasonably consistent with their a priori sigmas of 17 and 8 m, respectively,\nand their mean values of 2.3 and -1.9 m differ insignificantly from zero. On\nthe other hand, the rms value of 17.2 m of the corrections to the in-track\ncomponent u is substantially lower than the a priori value of 25 m and,\nmoreover, their mean value of 8.3 m differs significantly from zero (at the\n99% level of confidence). The existence of a significant positive bias in\nthe in-track component has been found also to exist and persist in several\nother projects in Africa and Eurasia, whereas no such bias has yet been\nencountered in projects in North America. The precise reason for the bias\nis unknown at this time but may relate to the fact that the four tracking\nstations used in the generation of the broadcast ephemeris are located in\nthe Western hemisphere. As for the a posteriori sigma of 17.2 m in u, this\nseems to be fairly characteristic of results obtained since the switchover\nin December of 1975 of the broadcast ephemeris to the WGS-72 system, and may\ntherefore well be real (the set of a priori constraints of 25, 17 and 8 m\nwere taken from the study of White, Huber and Taylor (1975)) On the basis\nof current experience, it would perhaps be appropriate in future projects to\nrevise the a priori sigma of u downward to about 15 to 20 m. The persistent\nbias in u for projects outside the Western hemisphere is a matter requiring\nfurther investigation.\nSubject to the above qualifications relating to the in-track component,\nthe orbital adjustments listed in Table 10 are quite satisfactory. The a\nposteriori standard deviations of the orbital components in u, V, W listed\nin the right hand side of the table are seen to average 2.2, 4.9 and 4.0 m,\nrespectively. These represent a substantial improvement over the a priori\nvalues of 25, 17 and 8 m and, indeed, are comparable to what might be expected\nfrom the precise ephemeris. The particular passes having the larger standard\ndeviations (in V and W particularly) are mostly those observed by only two\nstations or those that are of relatively low elevation angle from all parti-\ncipating stations. As a rule, when four well-distributed stations participate\nin the observation of a pass of moderate maximum elevation angle (>20°), one\ncan expect the short arc adjustment to generate a posteriori standard devia-\ntions of between 1 and 2 meters in all three components. When as many as\n6 well-distributed stations participate, the a posteriori standard deviations\nare generally suppressed to well below one meter. Thus a moderately strong\nshort arc net can be expected to yield adjusted orbits that are considerably\nsuperior to those associated with the normal precise ephemeris. In effect,\nthen, the short arc adjustment serves ultimately to transform the broadcast\nephemeris into a precise ephemeris.\nObservational Residuals From Short Arc Reductions\nOne measure of quality control associated with the short arc adjustment\nhas just been discussed, namely, the generation and analysis of adjustments\nto orbital state vectors. Another that will merely be mentioned in passing\nconcerns the reasonableness of the error coefficients obtained for each\nstation for each pass. Except for zero set, and, to some extent, frequency","125\nTABLE 10. Orbital adjustments to positional components of state vectors and associated\nstandard deviations of adjusted components for set of passes from Middle East project.\nORBITAL ADJUSTMENTS\nA POSTERIORI STANDARD DEVIATIONS\nPASS\nIN TRACK\nCROSS TRACK\nRADIAL\no\no W\nV\nNO.\nAu\nDv\nAw\n1\n12.6 m\n19.9 m\n19.9 m\n2.3 m\n4.5m\n1.8m\n2\n1.5\n- 0.4\n- 0.4\n2.4\n3.1\n2.3\n3\n3.8\n- 7.6\n- 7.6\n2.6\n8.4\n5.9\n4\n20.8\n21.9\n21.9\n1.7\n3.8\n1.4\n5\n18.6\n- 4.2\n- 4.2\n1.9\n2.1\n1.8\n6\n8.0\n25.9\n25.9\n3.2\n5.5\n3.8\n7\n- 5.6\n-12.1\n-12.1\n2.1\n1.8\n1.8\n8\n- 2.2\n2.4\n2.4\n4.3\n8.2\n7.5\n9\n14.5\n10.2\n10.2\n2.0\n2.4\n1.9\n10\n20.0\n14.4\n14.4\n1.4\n4.4\n2.2\n11\n13.6\n- 9.6\n- 9.6\n1.4\n4.1\n2.2\n12\n8.0\n- 5.6\n1.4\n1.0\n2.7\n1.7\n13\n52.9\n- 8.1\n7.9\n1.7\n3.5\n3.2\n14\n4.3\n6.2\n12.3\n1.1\n2.4\n1.8\n15\n-10.1\n5.2\n-11.0\n2.3\n6.4\n5.1\n16\n6.9\n- 3.1\n- 2.4\n1.6\n2.8\n1.7\n17\n19.7\n19.3\n-11.2\n1.3\n2.3\n1.4\n18\n0.5\n21.5\n-14.0\n2.5\n5.3\n5.6\n19\n12.2\n- 5.3\n5.7\n1.7\n4.2\n2.3\n20\n14.8\n5.4\n3.7\n1.6\n3.4\n1.2\n21\n7.9\n32.4\n- 9.0\n1.8\n3.7\n1.6\n22\n25.8\n15.8\n- 7.1\n2.3\n7.5\n6.8\n23\n31.0\n-29.5\n- 1.9\n2.4\n3.0\n2.8\n24\n14.1\n- 4.4\n2.3\n2.6\n6.3\n1.8\n25\n-26.6\n- 7.9\n10.7\n2.0\n4.8\n1.7\n26\n24.6\n- 5.0\n-10.8\n1.8\n2.8\n1.5\n27\n32.3\n30.3\n-18.1\n2.0\n4.4\n2.6\n28\n-10.2\n-13.8\n-14.0\n2.0\n2.6\n1.9\n29\n33.3\n4.2\n- 4.3\n1.0\n2.0\n0.9\n30\n31.7\n6.5\n6.0\n2.4\n8.1\n7.2\n31\n2.5\n0.6\n- 4.6\n0.8\n1.5\n1.1\n32\n22.0\n- 7.2\n5.4\n1.9\n5.5\n1.5\n33\n17.7\n- 6.2\n22.8\n3.8\n7.3\n6.6\n34\n18.4\n14.7\n12.1\n2.3\n7.2\n3.3\n35\n17.4\n4.4\n7.9\n1.7\n4.3\n2.1\n36\n13.8\n3.5\n-20.7\n1.1\n2.0\n1.9\n37\n0.0\n15.4\n- 0.4\n2.7\n7.0\n6.4\n38\n16.4\n21.2\n13.1\n3.7\n12.5\n3.7\n39\n8.2\n- 0.9\n1.2\n2.3\n4.3\n3.6\n40\n10.0\n-14.4\n4.1\n3.0\n6.0\n7.1\n41\n11.6\n10.1\n- 3.1\n3.1\n7.0\n7.2\n42\n13.5\n14.7\n-18.0\n1.4\n2.9\n1.6\n43\n19.1\n-16.6\n- 3.4\n1.4\n3.2\n2.1\n-\n44\n13.3\n- 9.1\n-16.8\n1.6\n3.1\n2.0\n45\n1.3\n10.7\n- 4.6\n1.9\n3.0\n2.1\n46\n4.4\n9.5\n- 2.9\n1.0\n2.7\n1.5\n47\n26.8\n3.2\n6.8\n2.2\n4.2\n1.5\n48\n13.2\n-14.3\n- 2.5\n8.7\n6.8\n3.5\n49\n- 1.4\n16.2\n29.0\n2.6\n7.0\n5.0\n50\n15.0\n1.6\n- 6.1\n2.7\n7.1\n4.3\n14.2\n51\n-14.3\n-22.3\n3.3\n6.6\n3.3\n52\n16.1\n-24.1\n- 3.2\n3.4\n9.2\n7.1\n53\n11.9\n15.2\n-20.5\n3.3\n7.6\n6.7\n54\n-16.5\n-12.4\n6.2\n2.5\n7.2\n5.2\n55\n- 8.2\n13.7\n- 3.8\n2.6\n5.9\n2.0\n56\n4.4\n3.4\n- 9.4\n3.8\n8.1\n7.8\n57\n1.3\n11.7\n- 8.6\n1.2\n2.7\n1.3\n8.3m\nMEAN:\n2.3m\n- 1.9m\n4.9m\n2.2m\n4.0m\nKMS:\n17.2\n14.0\n10.7","126\noffset, these coefficients are subject to fairly tight a priori constraints\nwhich should not be seriously violated by the adjustments arising from the\nadjustment. It should, however, be appreciated that within limitations\nconsistent with a priori constraints, the several terms of the error model\nserve not only to account for the physical effects for which they were\nspecifically formulated, but also they serve to accomodate any unmodeled\nsystematic errors that can be represented with reasonable fidelity by linear\ncombinations of terms of the error model. In particular, unmodeled errors\narising from higher order ionospheric refraction and asymmetric tropospheric\nrefraction have such smooth and simple shapes that they are largely amenable\nto implicit compensation by the explicit terms of the error model as long as\nelevation angles do not become too low (below 5 to 10° ) Some idea of the\nnature of the functions that can be implicitly accommodated by the error\nmodel can be gained from consideration of Figure 9 in which the spapes of\nfunctions associated with five of the six error coefficients are plotted for\na specific pass (max E = 50°) in a normalized form in which all functions\nare forced to unity at E = 10° on the descending leg of the pass. The function\nassociated with frequency bias of the satellite oscillator is not plotted\nbecause this term is subject to suppressive a priori constraints by virtue\nof the availability of the precisely monitored frequency from the satellite\nmessage. In linear combination the functions of Figure 9 can assume a modest\nvariety of shapes and amplitudes and so have a moderate capacity for accommo-\ndation of unmodeled effects. However, it is clear from the monotonicity of\nAr\nZERO SET\nTIMING\nOFFSET\nREFRACTION\nFREQUENCY\nDRIFT\nFREQUENCY\nOFFSET\n-1.0\nt= -350 sec\nt= 0\nt= 350 sec\nE= 10\nE=50°\nE 10°\nFIGURE 9. Functional forms of various terms in Doppler error model\nnormalized to unity at E = 10° on descending leg of selected pads\n(Emax = 50°).\nmax","127\nboth the curves and their derivatives on either side of mid-arc that\nunmodeled errors represented by compound curves with more than one inflection\nare not subject to effective accommodation. Such errors, if significant,\nmust therefore emerge, to some extent, in the recovered coordinates of the\ntracking station, but mostly in the observational residuals which thus become\nthe final repository of uncompensated systematic error.\nWith regard to the foregoing consideration, the choice of the ranging\nformulation for the observational equations for Doppler reductions offers\nsignificant advantages over the range-difference formulation. The former\ngenerates residuals that far better reflect the subtleties of uncompensated\nsystematic error and thus are more helpful in the detection and analysis of\nsuch error. An example of this is provided in Figure 10 wherein Geoceiver\nranging residuals from the short arc reduction of three passes are plotted.\nFigures 10a, b, C show the residuals resulting from the exercise of the\nranging equation and Figures 10d, e, f show the corresponding residuals\nfrom the exercise of the range-difference equations. In the upper three plots\nthe residuals are seen to conform rather closely to the hand-fitted, rather\nsinusoidal trends which are deliberately forced to assume bilateral symmetry\nwith respect to the point of closest approach at mid-arc. Such well-defined\ntrends of this general character are found to emerge in a large proportion\nof Geoceiver passes reduced by the short arc method exercising the ranging\noption. The trends are believed to reflect the effects of systematic changes\nin the location of the dual-frequency phase center of the Geoceiver antenna\nwith changing elevation angle. As such, they are susceptible to modeling\nof the form\nDr = (a1sin E + a2sin2E + a3sin3E +\n) sin E\nThe direct incorporation of this simple model into the short arc reduction is\ncomplicated by the fact that not all passes generate residuals having the\nbilateral symmetry displayed in Figures 10a, b, C. Some, instead, display\ntrends with radial symmetry about the point of closest approach as might be\nexpected from a 180° phase slip caused by the passage of the satellite through\nthe vertical null of the antenna pattern. Here, an alternative model is\nappropriate, and the situation is further complicated by the fact that in\nsome passes a significant, quasi-systematic trend attributable to multipath\nmay assume some prominence. Because of such difficulties explicit modeling\nof shifts in the phase center of the antenna has yet to be implemented in\nSAGA. It is clear, however, from Figures 10a, b, C that the successful\nremoval of such effects would lead to considerable improvement in the residuals,\nwith the rms value most likely being reduced to the 2 to 3 cm level.\nThe results just discussed serve to demonstrate the exquisite sensitivity\nof short-arc ranging residuals in revealing the presence of uncompensated\nsystematic errors having amplitudes as low as 5 to 10 cm. The range-difference\noption is far less effective in this regard, as is apparent from the residuals\nplotted in Figures 10d, e, f. Not only are trends mainly obscured, but also\nthe rms values of the residuals are somewhat worse (8.7, 5.6 and 5.5 cm,\nrespectively, as compared with 6.0, 4.7 and 5.0 cm) Thus the range-difference\nformulation is ill-suited to the fine-grained detection and analysis of\nresidual systematic error.","128\nAr (cm)\n+15\ntime\nPASS 1,\n-15\na.\nRMS = 6.0 cm\n+15\n-15\nb.\nPASS 2,\nRMS = 4.7 cm\n+15\nPASS 3,\n-15\nC.\nRMS = 5.0 cm\n+15\nd.\nPASS 1, ,\n-15\nRMS = 8.7 cm\n+15\ne. PASS 2,\n-15\nRMS. = 5.6 cm\n+15\nPASS 3,\nf.\nRMS = 5.5 cm\n-15\nFIGURE 10. Residuals for three Geoceiver passes reduced by short are\nmethod under ranging option (a,h,c) and range-difference option (d,c,f).","129\nThe possibility of extracting information on systematic errors inherent\nin the tracking system itself depends on the fact that in the short arc\nadjustment the effects of orbital errors are properly taken into account and\ndo not therefore contaminate the tracking residuals. Figure 11 shows a plot\nof range-difference residuals for a pass observed by a JMR-1 receiver (a)\nupper, when the orbit defined by the broadcast ephemeris is allowed appropriate\nfreedom to adjust, and (b) lower, when the orbit is allowed no freedom to\nadjust (as in point positioning) The rms error is of the residuals in the\nformer case is 2.7 cm whereas in the latter case it rises fourfold to 10.8 cm.\nBut even more importantly, the residuals from point positioning are totally\ndominated by the systematic trend resulting directly from orbital errors.\nSo pronounced is the artificially induced serial correlation in the residuals\nthat a representative sample of just 7 or so observations is sufficient to\ncarry virtually all the worthwhile information concerning the particular pass.\nThe high sampling rate is thus largely futile insofar as effective improvement\nin accuracies is concerned. Not so, when the short arc method is applied,\nfor here a far higher degree of randomness of residuals is obtained, particularly\nwith range-differences which, as discussed above, are relatively insensitive\nto uncompensated systematic errors in the tracking observations. When the\nranging option is exercised with the same pass, the effects of orbital errors\ngenerate a trend of the same general shape as in Figure 11b but with greatly\nincreased amplitude (to about 0.35 m) . Little wonder, then, that the range-\ndifference approach is almost universally adopted in reductions based on\npoint positioning.\nELEVATION ANGLE\n7.5°\n15\n30°\n45\n60\n60°\n45°\n30°\n15°\n7.5\n.10 m\nSHORT ARC RESIDUALS, RNS as 0.027m\n0\n10m\n.20 m\nPOINT POSITIONING RESIDUALS, RMS - 0.108m\n.10\n0\n10\nm\n20 m\n0\n2\n4\n6\n8\n10\n12\n14 min.\nTIME\nFIGURE 11. Residuals of range differences for the same pass resulting from\n(a) solution effected by Short Arc Geodetic Adjustment (upper) and from (b)\nPoint Positioning (lower).","130\nPotential Application of the Short Arc Method to\nthe Monitoring of Crustal Motion\nAs has already been pointed out, accuracies of relative positioning\nof a few tenths of a meter from a relatively small number of passes (25) have\nalready been demonstrated for short arc Doppler surveying over distances of\n30 km. Moreover, this has been obtained using the broadcast ephemeris.\nAnalytical error propagations indicate that such accuracies should in theory\nbe maintained over distances of several hundred kilometers. However, this\nhas yet to be demonstrated because of the unavailability, until quite recently,\nof a suitable standard. This is a matter that will be touched on briefly at\nthe end of this section. The main topic here concerns a simple exercise\nintended to shed some light on the potential feasibility of the short arc\nmethod for the practical monitoring of tectonic plate motions over distances\nof several hundred kilometers. As is well known, such motions are regularly\nmonitored on either side of major faults by geodimeters over distances of\nup to a few tons of kilometers. However, there is interest on the part of\ngeophysicists on the relative motions of tectonic plates at considerably\ngreater distances from the system of faults. Accuracies sufficient to detect\nmotions on the order of 5 cm/year are desired, and laser systems and VLBI\nsystems are already addressing the task. It is therefore interesting to\nspeculate on what might conceivably be expected from Doppler in this regard.\nTo this end, a computer simulation was performed at DBA on the hypothetical\nconfiguration shown in Figure 12 wherein one pair of stations is located on\none side of the San Andreas fault and a second pair is located on the other\nside. This four station net extends about 350 kilometers in the north-south\ndirection and about 200 km in the east-west direction. The following\nassumptions form the basis for the simulations:\n(a) simultaneous Doppler tracking of Navy Navigational satellites is\nperformed by geodetic type receivers at all four stations;\n(b) a total of 25 well-distributed, reducible passes is observed\n(normal 48 hour operation);\n(c) sampling rate is one readout nominally every 4.6 seconds (short\ncount Doppler) ;\n(d) elevation angle cutoff is 10°;\n(e) ranging option is exercised in SAGA III with standard deviation\nof 5 cm and zero serial correlation;\n(f) no baseline or station constraints are exercised (the net is allowed\nto 'float') ;\n(g) various a priori constraints, as indicated in Table 11, below, are\nexercised on orbital state vectors;\n(h) customary a priori constraints are applied to coefficients of error\nmodels with timing bias for Station 1 constrained to zero on each\npass.","131\n38°\n3\nSAN FRANCISCO\n2\n36°\n4\nSan Andreas\nFault\n1\n34°\nLOS ANGELES\n122°\n120°\n118°\nFIGURE 12. Layout of hypothetical four station net employed in simulation\nof short arc Doppler monitoring of crustal motions on either side of San\nAndreas fault.","132\nIn each of the various simulations the full 12x12 covariance matrix of\nthe X, Y, Z coordinates of the four stations was generated by SAGA III. From\nthis covariance matrix the standard deviations of the distances between the\nstations were computed. These are listed in Table 11. One striking result\nis that even with the imposition of very coarse a priori constraints of 1000 m\nand 1 m/sec (one sigma) on components of the state vector, standard deviations\nof better than 0.5 meters are to be expected for inter-station distances.\nWith constraints more typical of what is to be expected from the broadcast\nephemeris, namely 25 m in position and .02 m/sec in velocity, expected standard\ndeviations are seen to range between a low of 6.2 cm and a high of 29.0 cm,\nthe former corresponding to the most northerly baseline (1, 3) and the latter\ncorresponding to the most easterly baseline (2, 4). When constraints conser-\nvatively applicable to the precise ephemeris (5 m in position and .005 m/sec\nin velocity) are exercised, improvements are seen to be relatively modest,\nparticularly in the north-south direction. This again points out the fact\nthat the value of the precise ephemeris is mainly in absolute rather than\nrelative positioning. The relative weakness of the formal results in the\neast-west direction could be reduced considerably by lowering the cut-off\nangle in elevation to 5°. This, on the other hand, may entail some risks,\nthough these are likely to affect mainly the recovered heights rather than\nhorizontal distances.\nIt is to be emphasized most strongly that the results of the simulation\nare merely indicative of theoretical potential and should be taken with a\nhealthy dose of skepticism. In reality, even the most painstaking of simula-\ntions often turn out to be optimistic by a factor of 2 or 3 because of\nunmodeled systematic errors and significant serial correlations of errors.\nIt is, however, comforting in the present instance that only two days of\nobservations are sufficient to achieve the indicated formal results. Thus\nit is not too far fetched to expect that such results may be obtained in\nactuality from observations made over, say, a 5 to 10 day period. In any\ncase, the results clearly serve to indicate that short arc Doppler surveying\nis a worthy candidate for consideration in studies of crustal motions.\nShould it reasonably well live up to its theoretical potential, the short\narc Doppler method would offer significant advantages over the alternative\napproaches currently being pursued.\nTABLE 11. Results of simulations of short arc Doppler net of Figure 12.\nPRIORI SIGMAS\nSIGMAS OF RECOVERED DISTANCES\nOF STATE VECTORS\nBETWEEN DOPPLER STATIONS\nPOSITION\nVELOCITY\nO\no 13\n014\nO23\nO 24\no 34\n12\n1000 m\n1.00 m/sec\n.243m\n410n\n. 412m\n461\n480\n218m\n25\n.020\n.159\n.062\n.066\n.083\n.290\n.151\n10\n.010\n.125\n.057\n.058\n.075\n.228\n.123\n5\n.100\n.054\n.055\n.071\n178\n.103\n.005","133\nNow that Doppler surveying by the short arc method shows promise of\npushing toward the 5 to 10 cm level in relative positioning, a need exists for\na long baseline of sufficient accuracy to explore the practical limits of the\nmethod. Until rather recently the best candidates, long geodimeter traverses\nwith their characteristic accuracies of about 1:106, were inadequate for this\nexacting task. However, a new Finnish traverse of some 890 km in length and\na reported accuracy of + 12 cm (one sigma), or 1:7,400,000, has been reported\nby Parm (1976). The course of this extraordinary traverse, comprised of 26\nstations in all, is pictured in Figure 13. Simultaneous occupancy by Doppler\nreceivers of, say, four stations at nominal intervals of 300 km could be expected\nto yield a total of some 600 to 800 good, four-station passes during the course\nof one month. From this wealth of data definitive answers could be arrived at\nconcerning a number of fundamental questions, including the matter of possible\nbias in Doppler scale when the short arc method is used. Properly formulated,\nexecuted and analyzed, the suggested undertaking has the potential of becoming\na classic experiment of far reaching implications.\nSuggested Short Arc Net in Support of the\nReadjustment of the North American Datum\nOn the basis of computer simulations it had been pointed out in Brown\n(1970) that a properly designed short arc Geoceiver net covering central North\nAmerica could be expected to yield accuracies in geodetic positioning on the\norder of a few tenths of a meter. Unfortunately, little credence has been\nattached to this projection in most governmental circles, for no U.S. agency\nwith sustained involvement in Doppler surveying has actively exploited the\npotential of the method. Instead, this has been left to the private sector\nwhich can ill-affort the inefficiencies of point positioning. It is well,\ntherefore, as a final exercise to consider how one might go about the task\nof performing a comprehensive short arc survey of the conterminous United\nStates. Two different plans will be suggested, one involving a commitment\nof 5 Doppler receivers for a period of about 150 days and the second a\ncommitment of 13 Doppler receivers for a period of about 50 days. In both\ncases the overall net will be assumed to involve a total of 121 fairly\nevenly spaced stations, and the desired accuracy for relative positioning\nwill be assumed to be between 0.10 and 0.20 meters, one sigma.\nIn both plans, the U.S. is divided into a total of nine operational zones\nof roughly equal area as indicated in Figure 14. A total of four base stations,\nindicated as 001, 002, 003 and 004 in Figure 14, is established. In Plan I\n(5 Doppler receivers), the following operational scenario would be executed:\n(a) base stations 001 and 002 would be continuously occupied for a\nperiod of about 50 days during which three mobile parties operate\nin Zones 1, 2, and 3 with one party in each zone;\n(b) each mobile party will be assigned about 13 stations in its designated\nzone and, guided by satellite alerts and field printouts, will occupy\neach station until a minimum of 40 good passes has been acquired;\n(c) periods of occupancy will average about 60 hours for the typical\nstation, and moves to the next station (a few hundred kilometers","134\n2\n:\n21\n2n\nIN\n30\n1.\nH\n10\nKaamanen SF 280\n277\n275\n268\n267\n264\n262\n301\n303\n295\n321\nTRAVERSE\n320\n0\n50\n100\n200 km\n322\nA\n181\n182\n34\n231\n216\n214\n213\n14)\n143\n338\nJanhiala SF 54\n.\n.\n:\n21\n:\nJot\n32\nFIGURE 13. . High precision traverse and stellar triangulation net\nof Finland relative to primary geodetic network (from Parm (1976) ).\n.","135\naway) will generally require less than 12 hours, so that, on the\naverage, observations will be completed for three mobile stations\nevery three days;\n(d) under the foregoing schedule the operation for Zones 1, 2 and 3\n(a total of 39 stations) would be completed in 39 days, a figure\nthat is increased in this planning exercise to 50 days in order\nto allow for contingencies;\n(e) steps (a), , (b) , (c) , (d) are repeated with base stations 002 and\n003 being continuously occupied for a second period of about 50\ndays and with mobile stations operating in Zones 4, 5, 6 and moving\ngenerally from east to west in each zone;\n(f)\nupon completion of (e) the same observational cycle is repeated\nfor Zones 7, 8, 9 with base stations 003 and 004 being occupied\nfor the final period of 50 days.\nThe rigorous short arc adjustment for Plan I would entail the following:\n(a) under the assumption that on the average 4 out of 5 receivers\nwould participate successfully on the typical pass selected for\nreduction, each such pass would generate about 4x125=500 observa-\ntional equations (short count Doppler is assumed) ;\n7\n4\n004\n8\n003\n001\n5\n2\n002\n9\n3\n6\nFIGURE 14. Illustrating operational zones and system of base stations\nappropriate to short arc Doppler survey of conterminous United States.","136\n(b) the typical pass would generate a total of 6 unknowns corresponding\nto the state vector and a total of 4x5=20 unknowns corresponding\nto the exercise of 5 error coefficients for each of the four parti-\ncipating stations, or a net total of 26 unknowns per pass;\n(c)\napproximately 500 passes would be selected for reduction from each\nof the three phases of the operation, or a total of some 1500 passes\nin all;\n(d) the total number of observational equations generated by the entire\nnet would thus amount roughly to 500x1500=750,000, and the number\nof unknowns in the normal equations for the rigorous short arc\nadjustment would amount to 3x121=363 coordinates of stations plus\n26x1500=39,000, or a grand total, rounded upwards, of roughly 40,000\nunknowns, or a ratio of about 19 observations per unknown (this\nignores the observational equations implicit in the a priori con-\nstraints on parameters)\n(e) through the use of the algorithm for second order partitioned\nregression, the 40,000x40,000 system of normal equations would\nreduce to one of order 363x363 which in turn, through proper\nordering, could be made to assume a banded bordered form with the\nunknowns corresponding to the four base stations forming the border;\n(f)\nthe inversion of the reduced 363x363 system of normal equations\nwould provide the full covariance matrix of the coordinates of the\n121 stations;\n(g) if the broadcast ephemeris had been used exclusively in the reduc-\ntion, the formal standard deviations of the coordinates in the\nWGS-72 system could be expected to range between 0.30 and 0.40\nmeters; formal standard deviations referred to an adopted national\norigin could be expected to range mostly between 0.10 and 0.20\nmeters;\n(h) use of the precise ephemeris with appropriate a priori constraints\non a significant proportion of passes, say 20%, could be expected\nto reduce the formal standard deviations to about 0.20 m in the\nNWL-9D system (the mixing of precise and broadcast ephemerides\nwould require the inclusion in the reduction of appropriate\nadditional parameters relating the NWL-9D and WGS-72 coordinate\nsystems); on the other hand, the use of the precise ephemeris\nwould produce little improvement in accuracies of relative\npositioning.\nIn Plan II (13 receivers) all four base stations would be occupied\nsimultaneously and nine mobile receivers would be employed, one for each\nzone. Operations in each zone would follow the general scenario of Plan I\nwith the typical occupancy being about 60 hours and the typical move requiring\nunder 12 hours, thus conforming to the basic 3 day cycle. Under this scheme,\na total of 9 new stations would be occupied every 3 days and the total opera-\ntion would consume some 39 days, which is rounded up to 50 days to allow for","137\ncontingencies. Under Plan II a total of roughly 600 passes would be carried\nin the final reduction with each pass observed by an average of 7 to 8\nreceivers. Using the more optimistic figure of 8 receivers per pass, one\nfinds that the total number of observational equations to be expected is on\nthe order of 8x125x600=600,000 and the number of unknowns is 3x121+46x600=\n27,963 which may be rounded up to 28,000 to yield a ratio of about 21\nobservations per unknown. The 363x363 reduced system of normal equations\nresulting from the application of second order partitioned regression would,\nas with the system from Plan I, be of banded bordered form but with an\nappreciably wider bandwidth. Accuracies of relative positioning under Plan II\nwould be somewhat higher than those to be expected from Plan I but geocentric\naccuracies relative to WGS-72 would be somewhat worse because of the lower\nnumber of passes reduced.\nIf done commercially, the field work for Plan II would probably call\nfor a consortium of two or three companies, whereas the field work for\nPlan I could easily be accomplished by a single firm. As for costs, either\nplan could be fully executed (field work and data reduction) for under\n$500,000. Data reduction for either plan would require about 8 months following\ncompletion of the field work. Accordingly, Plan I would require a total of\n13 months for the entire project and Plan II a total of 10 months. Either would\ncreate a truly unified net worthy of serving as control for the readjustment of\nthe U.S. portion of the North American Datum. Such a net would be totally\nimmune in relative positioning to such vagaries of the precise ephemeris as\nillustrated in Figure 15 taken from Anderle and Tannebaum (1974). Here,\nstation heights developed from the precise ephemeris for a Brazilian station\nare seen to vary during the course of one year about an approximately sinu-\nsoidal trend having an amplitude of about one meter. This suggests that\nin certain instances strict enforcement of the precise ephemeris could lead\nto errors or dislocations in relative positions (in heights, at least) of\nas much as two meters for stations located in the same general area but\nobserved several months apart. Undoubtedly, problems of this nature are not\nas pronounced for stations located in North America because of the relative\nabundance of permanent Tranet stations throughout the area. Nonetheless,\nreflection on the long term implications of such considerations should give\npause to anyone considering a significant geodetic undertaking which is to\nbe rigidly hung on the not-quite-invariant framework of the precise ephemeris\n(this applies, of course, even more so to the broadcast ephemeris).\nLet it be assumed for the moment that it is indeed practicable to\ngenerate a short arc net for the contiguous United States leading to accuracies\nof 10 to 20 cm as outlined above. Then one can come up with a very basic\nreason for the implementation of the suggested approach in spite of the\nconsiderable commitment already made to the project of point positioning. It\nis simply a matter of doing the best job possible with available technology.\nUnless such a philosophy governs all aspects of an undertaking as fundamental\nas the readjustment of the North American Datum, those involved can hardly\nexpect to derive full satisfaction from the prodigous efforts to be demanded.\nThis is particularly so should considerably superior Doppler nets become\ncommonplace in other countries by virtue of their taking full advantage of\nthe short arc method. It should be appreciated that if the U.S. net were to\nbe reobserved as a short arc net, the observations of the preceding point","138\nHeight Residuals For Brazil\nResiduals Before Fit = 82 CM, After Fit = 78 CM\n4\nDrift = -95 t 36 CM/YR\n3\n2\n1\n0\n(+)\n+\n-1\n-2\n-3\n.4\n0\n90\n180\n270\n300\nDAYS 1973\nFIGURE 15. Variation during course of one year of height of station determined\nby consecutive five day solutions by point positioning using precise ephemeris\n(from Anderle and Tannenbaum (1974)).\npositioning project would not have to be discarded. On the contrary, they\ncould and should be incorporated rigorously into the simultaneous short arc\nadjustment. This would then lead to improved relative accuracies for those\ncombinations of stations of the point positioning project that happen to\nhave been occupied concurrently by Doppler receivers. It would also lead\nto considerable improvement in accuracies of geocentric coordinates through-\nout the net by virtue of the many hundreds of passes of the precise ephemeris\nthereby introduced.\nAside from the basic satisfaction to be derived from a job well done,\nthere is another reason for the redirection suggested above. It is related\nto the projected readjustment of the primary leveling net of the U.S., a\nproject expected to cost about 16 million dollars. Let it be supposed that\nDoppler stations accurate to, say, 10 cm or so were colocated at representative\nstations throughout the primary leveling net. Then, once the observations\nand adjustment of the leveling net were completed, it would become a straight-\nforward matter to employ subsequent short arc surveys by Doppler (or its\nsuccessors) to monitor throughout the country changes in elevation brought\nabout by regional uplift or subsidence. Thus, if tied at the outset to a\nDoppler survey of sufficient accuracy, the primary leveling net would not have","139\nto be redone for generations. In this way, Doppler surveying by the short\narc method could play a pivotal role not only in the readjustment of the\nNorth American Datum but also in the long term preservation of the integrity\nof the new primary leveling net.\nTo conclude this section it must once again be emphasized that the\nforegoing projections are directly dependent on the assumption that the\ntheoretical potential of Doppler surveying by the short arc method can, in\nfact, be realized over distances of several hundred kilometers. This, in\nturn, has yet to be subjected to definitive testing, though the way has now\nbeen opened by the existence of the Finnish High Precision Traverse.\nConclusions\nThe short arc method provides the most rigorous, effective, economical\nand accurate means for the execution of Doppler surveys of highest practicable\ninternal precision and temporal stability.\nReferences\n1972. Report of the DOD Geoceiver Test Program. DMA Report 0001.\n,\nAnderle, R. J., 1974. \"Role of Artificial Earth Satellites in Redefinition\nof the North American Datum.\" The Canadian Surveyor, Vol. 28, No. 5,\nDecember, 1974.\nAnderle and Tannenbaum, 1974. \"Practical Realization of a Reference System\nfor Earth Dynamics by Satellite Methods.\" NWL Technical Report TR-3166,\nJune, 1974.\nBrown, D.C., 1958. \"A Solution to the General Problem of Multiple Station\nAnalytical Stereotriangulation. RCA Missile Test Project Data Reduction\nTechnical Report No. 39, Patrick AFB, Florida.\nBrown, D.C., 1964. \"A Calibration Satellite as a Means for the Evaluation of\nthe Practical Effectiveness of the Concept of Self-Calibration of Tracking\nSystems.\" AFCRL Report No. 64-1004.\nBrown, D.C., 1966. \"Advanced Techniques for the Reduction of Geodetic SECOR\nObservations. Final Report prepared for GIMRADA under U.S. Army Contract\nNo. DA-44-009-AMC-937(X)\nBrown, D.C., 1967a. \"Review of Current Geodetic Satellite Programs and Recom-\nmendations for Future Programs.\" Final Report for NASA Headquarters,\nContract No. NASW-1469.\nBrown, D.C., 1967b. \"Precise Determination of Geodetic Positions by the Method\nof Continuous Traces.\" AFCRL Report No. 67-0558.\nBrown, D.C., 1968. \"Short Arc Optical Survey of the GEOS North American\nTracking Network.\" NASA Report X-550-68-439.","140\nBrown, D.C., 1970. \"Near Term Prospects for Positional Accuracies of 0.1 to\n1.0 Meters from Satellite Geodesy.\" AFCRL Report No. 70-0501.\nBrown, D.C., 1975. \"Central Florida Test of Doppler Surveying with the JMR-1\nReceiver.\" DBA Technical Note No. 75-001.\nBrown, D.C., 1976. \"Doppler Surveying with the JMR-1 Receiver.\" Bulletin\nGeodesique, Vol. 50, No. 1, pp. 9-25.\nBrown, Bush and Sibol, 1963. \"Study of the Feasibility of Rocket and Satellite\nApproaches to the Calibration of Tracking Systems.\" AFCRL Report No.\n63-789.\nBrown, Bush and Sibol, 1964. \"Investigation of the Feasibility of Self-\nCalibration of Tracking Systems.\" AFCRL Report No. 64-441.\nBrown, Hartwell, Stephenson, 1965. \"Geodetic Data Analysis for GEOS A, An\nExperimental Design.\" Final Report, Contract NAS5-9860, prepared by\nDBA Systems for NASA Goddard Space Flight Center.\nBrown, Trotter, 1969. \"SAGA, A Computer Program for Short Arc Geodetic\nAdjustment of Satellite Observations.\" AFCRL Report No. 69-0080.\nBrown, Trotter, 1973. \"Extensions to SAGA for the Geodetic Reduction of\nDoppler Observations.\" AFCRL Report No. 73-0177.\nHadgigeorge, G., 1974. \"AFCRL Contributions to the National Geodetic Satellite\nProgram (NGSP).' Chapter IX. \"Simultaneous Recovery of Satellite and\nStation Positions Utilizing the Short Arc Method.\" AFCRL Report No.\n74-0217.\nHothem, L.D., 1975. \"Evaluation of Precision and Error Sources Associated\nwith Doppler Positioning.\" Paper presented to the 1975 Spring Annual\nMeeting of the American Geophysical Union, Washington, D.C., June 16-19,\n1975.\nParm, T., 1976. \"High Precision Traverse of Finland.\" Publication No. 79\nof the Finnish Geodetic Institute.\nRutcheidt, E., 1974. \"Worldwide Geodetic Positioning from Satellite with\nPortable Doppler Receivers.\" Presented to F.I.G., Washington, D.C.,\nSeptember, 1974.\nStrange, Hothem, White, 1975. \"Results of Satellite Positioning in the United\nStates.\" Paper presented to the 1975 Spring Annual Meeting of the American\nGeophysical Union, Washington, D.C., June 16-19, 1975.\nWhite, Huber, Taylor, 1975. \"Comparison between Naval Surface Weapons Center\nand Navy Astronautics Group Ephemerides for Geoceiver Positioning.\" Defense\nMapping Agency Aerospace Center Technical Report 75-001.","141\nDMATC DOPPLER DETERMINATION\nOF POLAR MOTION\nBruce R. Bowman\nCaroline F. Leroy\nDefense Mapping Agency Topographic Center\n6500 Brookes Lane\nWashington, D. C. 20315\nAbstract\nThe phenomenon of polar motion is discussed, and the histories of the\nseveral worldwide Polar Motion Services are reviewed. The Doppler data\nprocessed by the Defense Mapping Agency Topographic Center (DMATC) for polar\nmotion determination is described. Bi-daily Doppler pole values from 1973 to\n1976 are analyzed using the Maximum Entropy Method (MEM) of spectral analysis.\nThe analysis demonstrates that the high frequency spectrum (4-20 days/cycle)\nis dominated by periodicities resulting from Doppler orbit computations with\ninadequate resonance terms of the Earth's gravity field. After removal of\nthe 27th order resonance effect a standard deviation of 0.4 meter in the X\nand Y pole components is obtained in a regression analysis of 50 days of\nbi-daily values. The analysis also shows that the low frequency spectrum is\ndominated by the annual effect and Chandler Wobble. The MEM provides good\nspectral resolution of these variations, and also shows smaller amplitude\nperiodicities occurring at 1.3, 2.0, 2.5, and 4.0 cycles/year. A computed\namplitude of 0.49 + 0.06 m for the 1.3 cycles/year variation is in good\nagreement with the amplitude previously obtained during the rare times when\nthe period has been observed. The precision of the bi-daily data and the\nhigh resolution of the spectral analysis indicate that the Doppler data will\nbe extremely useful in increasing our understanding of the geophysical effects\nof polar motion.\nIntroduction\nThe Defense Mapping Agency Topographic Center (DMATC) has recently ac-\nquired the capability of determining the daily motion of the Earth's polar\naxis. Studies described in this paper are being undertaken to determine the\nprecision and frequency components of the DMATC computed polar motion.\nPolar motion may be defined as the motion of the instantaneous spin axis\nof the Earth with respect to the geographic pole of the Earth's crust. There\nare several components of polar motion with various periods, amplitudes, and\ncauses. The Chandler component is caused by the spinning of the Earth about\nan axis other than the principal axis of inertia, and has a period of approx-\nimately 430 days and an amplitude of 012 (6 meters on the Earth's surface).\nThe annual component, with a period of 12 months and an amplitude of approx-\nimately 0.1, is due to meteorological effects such as seasonal changes in air\nmasses over the hemispheres and changes in vegetation and snow loading. Each\nof these components produce a counterclockwise rotation, as seen from above\nthe North Pole, and the two alternately reinforce and oppose each other in a\ncycle of about 6 years. Secular motion produces a progressive drift of 0.003\nper year in the direction of 65 degrees West longitude (Markowitz, 1970).","142\nThe cause of this secular motion, as well as small periodic motions at various\nfrequencies, is unknown. Such phenomena as earthquakes and core-mantle\ncoupling (Rochester, 1973) have been suggested as causes.\nPolar motion is not to be confused with precession and nutation. Polar\nmotion produces a latitude and longitude change of the Earth's spin axis but\ndoes not cause a directional change of the spin axis in inertial space. In\ncontrast, precession and nutation result in the Earth's spin axis tracing a\ncone in space. The sun and moon, which are in orbital planes other than the\nEarth's equatorial plane, exert gravitational forces on the Earth's equatorial\nbulge of mass and cause the spin axis rotation effect. The major portion of\nthis motion is called precession and has a period of 25,800 years. The smaller\noscillating portion, with a period 18.6 years, is called nutation.\nDevelopment of Polar Motion Services\nIn the 18th century it was theorized that the poles should move in circles\nin a period of about 305 days. By the late 19th century, changes in latitude\nwere observed at Berlin, and as a result, the International Latitude Service\n(ILS) was established about 1899 to determine the path of the pole. Since\nobservations from several stations well distributed in longitude are necessary\nto determine movement of the pole, the ILS consists of five observatories,\nall at approximately 39 degrees 8 minutes North latitude, but widely distrib-\nuted in longitude: Mizusawa, Japan; Kitab, Union of Soviet Socialist Repub-\nlics; Carlotforte, Italy; Gaithersburg, Maryland; and Ukiah, California.\nEach observatory uses visual zenith telescopes for optical observations of\nstars. All five observatories measure the same stars, thus, eliminating\neffects of errors in star catalogues. The origin, from which ILS polar motion\nis measured, is called the Conventional International Origin (CIO). The CIO\npole, defined by the mean latitude of the ILS stations, is the mean position\nof the true celestial pole from 1900 to 1905. The drift of the CIO pole over\nthe past 70 years has been about 0.25, or 0.0036 per year (Markowitz, 1976).\nThe International Polar Motion Service (IPMS) was established in 1962 to\nreplace the ILS. The IPMS incorporates observations from 59 stations and\nobservatories all over the globe (Yuma, 1975), inclusive of the ILS stations.\nCorrected time and polar motion values determined from ILS and IPMS station\nobservations are currently published by the Central Bureau of the International\nPolar Motion Service in Mizusawa, Japan, on a monthly and annual basis.\nSince 1962, the Bureau International de L'Heure (BIH) has been determining\npolar motion from approximately 40 worldwide stations. Optical observations\nof stars are made with visual zenith telescopes, photographic zenith tele-\nscopes, and Danjon Astrolabes. The BIH results incorporate both latitude\nand time observations.\nTo establish a relationship to the ILS system, the BIH system of 1968\nwas determined such that the average difference between the ILS and BIH pole\npositions was zero for the period 1964-1967 (Guinot, et. al., 1970). Pole\npositions based on a combination of optical observations and Doppler results\nare published monthly in Circulaire D (Guinot, et. al., 1970) and in annual\nreports.","143\nDoppler observations of the polar orbiting U.S. Navy navigation sate-\nllites (NNS) have been used since 1969 to compute daily pole positions. In\n1969, Anderle (1976) found that errors in the assumed position of the pole\nproduced a measurable timing effect when computing the time of arrival of the\nsatellite signal at a tracking station. A station in the meridian in which\nthe pole position error exists will observe an along track, or time, error\nwhen a polar satellite passes over the station, and 12 hours later, the station\nwill observe the same error but with the opposite sign when the satellite\npasses over the station traveling in the opposite direction. Thus, observa-\ntions of a polar satellite can be used to determine the component of pole\nposition error in the meridian of the station.\nPrior to 1971, the pole determination method used by the Naval Surface\nWeapons Center (NSWC) was a series of three least squares programs. First,\norbital parameters, including an atmospheric density scaling factor, were\ndetermined with a 2-day period of Doppler tracking data using nominal pole\npositions. Second, latitude residuals were computed for each satellite pass\nover each station using the orbit determined in step one. Third, the latitude\nresiduals were used to determine the pole position.\nSince April 1975, DMATC has computed the pole position on a daily basis\nusing the method adopted by NSWC in August 1971 and employed at NSWC until\nApril 1975. This method uses 48 hours of observation data in the simultan-\neous least squares solution of orbit constants, pole position, atmospheric\ndensity scaling factor, pass frequencies, and tropospheric refraction\ncorrections. In addition, coordinates of a limited number of stations may\nbe carried as unknowns until precise coordinates have been determined. The\ncomputer program entitled CELEST (0'Toole, 1976) was written by NSWC to\nutilize this method in processing large quantities of Doppler data. In\naddition to the computation of the pole position the primary output of the\nprogram is an Earth fixed precise ephemeris used for point positioning.\nDMATC Doppler derived bi-daily polar motion results are used to compute\n5-day means, where 6 days are included in one report and 4 days in the next.\nResults from at least one satellite, and normally two, are included. The\nreports are mailed to users on a weekly or monthly basis and provided to the\nU.S. Naval Observatory on a weekly basis for inclusion in their Time Service\nAnnouncement, Series 7.\nDoppler Observations used in Polar Motion Computations\nDoppler observations are made daily by a network of approximately 20\nworldwide permanent tracking stations called the TRANET (Fig. 1). The\nTRANET stations receive the 400 MHz and 150 MHz signals transmitted from the\nNNS satellites, beat them against a precise ground station oscillator, and mix\nthe two frequencies to remove the first order ionospheric refraction effects.\nDoppler data are also observed by the \"OPNET\" stations. The four Opera-\ntional Network or OPNET stations are located in Maine, Minnesota, California,\nand Hawaii, and are used primarily for orbit determination for navigation\npurposes. The OPNET data are used by the Navy to determine an orbit that is\nextrapolated and interjected into the NNS satellite, and is known as the","144\nbroadcast ephemeris. The Navy furnishes the OPNET data to DMATC for use in\nprecise ephemeris and polar motion determination. Whereas DMATC has the\nresponsibility for maintaining the TRANET, the Navy Astronautics Group has\nthe responsibility for maintaining the OPNET.\nOccasionally Geoceivers, portable Doppler receivers, are deployed to track\ngeodetic satellites such as GEOS-III. During these times data from NNS sate-\nllites are also collected by the portable receivers and incorporated into the\nprecise ephemeris and polar motion determination.\nTwo satellites are currently being tracked for precise ephemeris computa-\ntions. For the primary or first priority satellite, currently 1970-67A,\napproximately 140 passes are available in the 48-hour time span used for orbit\ndetermination. Approximately 100 passes are available in the 48-hour time\nspan for the orbit determination of 1967-34A, currently the secondary sate-\nllite. The number of passes contributed by each station varies from 2 to 4\npasses per day based upon the latitude of the station, assigned tracking\npriorities, and timeliness of direct data transmission to DMATC. The orbit\ndetermination computations are computed from 3 to 10 days after the observa-\ntion date.\nThe accuracy of the orbit determination is reflected by two statistics.\nFirst, the discontinuity in the ephemeris at the ends of each 48-hour time\nspan has a mean value of 3 meters. Second, the root mean square of the\nresiduals of the least squares adjustment is approximately 3 meters. Thus,\nthese two statistics provide a basis for stating that the precise ephemeris\nis accurate to 3 meters.\nAnalysis of Doppler Pole Values\nDoppler pole values determined by DMATC for 1975 are shown in Fig. 2.\nData obtained from the orbit determination of two NNS satellites, numbers 68\n(1970-67A) and 77 (1973-81A) are plotted along with the 5-day smoothed BIH\nvalues. Fig. 3 extends the plot into 1976. Data from three NNS satellites\nare shown during 1976 because one of the two satellites used for the computa-\ntions of the DMATC precise ephemerides was changed from 77 to 58 (1967-34A) on\nDay 153 of 1976. The figures show that the Y pole component (the axis toward\n90 degrees West longitude) of the Doppler data agrees better with the BIH\nvalues than does the X pole component (the axis toward Greenwich). The\nDoppler data appears to have a daily scatter of approximately 2 meters in\nboth the X and Y components. The Y component values are all in good agreement\nwith no biases readily apparent. However, there are periods when a bias in X\nappears between the values computed from data of the two different satellites.\nDoppler X pole values for the last 60 days of 1975 show a difference between\nvalues from the two satellites. The values obtained from satellite 77 tend to\nbe one-half to one meter lower than the values obtained from satellite 68.\nThe difference between satellite values is even more pronounced when comparing\nthe X pole data during the last 50 days of the span shown in Fig. 3. The X\nvalues obtained from satellite 58 appear to be approximately 1 meter lower than\nthe values obtained from satellite 68. A portion of the bias can be attributed\nto the effect of inadequate resonance gravity coefficients (discussed below)\nin the computation of the different NNS orbits, and part of the bias can be","60'\n40\n20\n20\n40\nA\nSeychelles\nCONTRIBUTING STA.\n80\nI\nFOREIGN TRANET\nS\nA\nDMATC TRANET\n60\nS. Africa\nPSL TRANET\nARL TRANET\n40\nItaly\nBelgium\n20\nEngland\n0\nit\n20\n26\ny\nS. Jose\nAND\nVirginia (DMATC)\nDO\n2\n40\nGREENL\nThule\n40\nOUTH\nAMERIC\nOttawa\n6C\n60°\nTexas (ARL)\nT KH\nWe\n80)\n80°\nMA\nNew Mexico\n100\n(PSL)\n100\nAnchorage\n120\n120\n140\n140\nSemoa\n160\n160\nMcMurdo\n180\n100\nAustralia\n160\n160\nJapan\nGuam\nSan Miguel\nMAC\n140\n140\n(\n120\n120\nA\no\nI\n100\n100\nOCEAN\nINDIA\nA S\n80\n60\n40°\n20\n20)\n40\n0\n60","146\n6.0\n+\n0\n+\n00+ 0\n++\nX Pole Component\n++0+\n+00\n0\n4.0\n+\n+\n+000+00\n0\n00+\n+0\n00\n+0+\n++0++0\n+\n00000\n0\n00\n+ + 000+00\n++++\n0 ++00\n+0\n+0\n0\n000 000+F 0+0+ +\n0 +0 +000 +\n2.0\n0\n000+0\n0\n+0+00+\n+\n++0000+\n00\n+\n+0\n+0000\n0.0\n0\n0\n00\n700\n+\n0\n0+0\n0\n00\n++\n000\n00000\n0\n0\n0000\n+0\n0+00+\n+\n+0\n-2.0\n00\n++0\n0\n+++++\n+0\n00\n0\n0+0\n070\n++00+00\n+\n++00\n0\n-4.0\n+0\n+\n+\n+\n++0 +\n+ 0 0+\n000+00\nSAT 77\n12.0\n0\n0\n0\nSAT 68\n0000\n0\n-0+0++++00+\nBIH\n0000\n8\n+070*00+\n++++(\n+0+00\n0\n10.0\n0\n+0\n00\n0\n0\n000\n0\n0\n+0\n8.0\n0\n00+\n00\n+00\n0\nas\n0\nY Pole Component\n+\n+\n00\n0\n00\n+\n00++\n09\n+00*0\n6.0\n0 +\n+\n+0\n+0\n0+\n01\n+\n0\n00\n0+\n+\n+\n+ 0\n+00\n0\n0\ntoo\n4.0\n000\n0\n0\n+\n0+\n0+0\n0\n+\n0+\n0+0+\n+\n2.0\n+\n+\n0.0\n1\n100\n200\n300\n365\nYear Day 1975\nFig. 2 Pole values during 1975 determined from BIH and from Doppler data\nof satellites 68 (1970-67A) and 77 (1973-81A).","147\n8.0\n00\n6.0\nSAT 77\nSAT 68\n00000\n4.0\nX Pole Component\nSAT 58\n2.0\nBIH\n+0\n+++000\n00+\n0.0\n-2.0\ntoo\n+0\n0+0+\n0\n+00\n0\n-4.0\n00+0\n000\n0\n0\n0+000\n0\nto o o\n0\n00\n++\n+0\n++++\n00\n+0\n000\n0\n0000+ +\n-6.0\n++\n+\n0+\n00\n0+000+6\n00\n14.0\n0\n+0\n00\n00000\n+00\nhus\n0\n0\n0\nod\n0\n40\n00\nof\n12.0\n+0\n+\n0\n00⑉\n0\n0\n10.0\nY Pole Component\n0\n0\n8.0\n00\n0\n++\n000\n+000\n+\n0\n00\n+0\n+\n6.0\n0\n1\n100\n200\n300\n365\nYear Day 1976\nFig. 3\nPole values during 1976 determined from BIH and from Doppler data\nof satellites 58 (1967-34A), 68 (1970-67A), and 77 (1973-81A).","148\nattributed to the different number and locations of stations tracking the\ndifferent satellites (Anderle, 1973).\nThe Doppler bi-daily values were analyzed to determine the standard\ndeviation of the data over a long time period in relation to the 2-day orbit\nreduction data span, and to examine the spectrum for spurious frequencies\nintroduced through the orbit reduction method. The high frequency end of the\nspectrum was resolved using 50-day data spans of the X and Y bi-daily values.\nThe Maximum Entropy Method (MEM) of spectral analysis (Burg, 1967; Ulrych\nand Bishop, 1975) was used for the process. The MEM theory is very useful in\nstudying data of very short spans with respect to the frequencies of interest\nbecause the method is maximally noncommittal with regard to the unavailable\ninformation outside the span. The algorithm given to Ulrych and Bishop (1975)\nwas used with a prediction error filter length of 50 percent of the data\nspan.\nFigure 4 shows the high frequency spectrum of the X pole component for\n5 data spans of 5 different NNS satellites. The predominate feature in almost\nall spectrums is the peak occurring for a period of from 5 to 6 days. This\nperiod results from the lack of adequate resonance coefficients for the 28th\ndegree and 27th order spherical harmonic term representing the Earth's\ngravity field. Resonance occurs when the orbit ground trace repeats the\nsame pattern after an integer number of revolutions of the satellite (refer\nto Wagner and Klosko (1975) for a detailed description of shallow resonance).\nThe shallow resonance experienced by each satellite is a function of the mean\nmotion, inclination, and eccentricity of the orbit, and is, therefore, variable\nfrom one orbit to the next.\nTable 1 lists the observed resonance periods in Fig. 4 and the theoretical\nperiod computed from formulations by Kaula (1966). The agreement between the\nobserved and computed values is excellent except for satellite 60, the only\nsatellite for which no recent data was available. The satellite 58 spectrum\nshows no resonance peak in Fig. 4 because the period is exceptionally long.\nThe spectrum was extended for this satellite and the results appear in\nTable 1. Figure 5 shows the results of the high frequency spectrum of the Y\ncomponent. The results are nearly the same as for the X component although\nthe peaks are not quite as pronounced in the Y spectrum, and the peak for\nsatellite 60 is only questionably present. The most reliable Y spectrums,\ncomputed from 1976 data, are in very good agreement with the X pole spectrum\nfor the same data spans. For satellites 68 and 59 the double peaks at\napproximately 9 and 13 days result from inadequate resonance coefficients of\n13th and 14th order. These terms produce resonance periods of approximately\n1.7 and 2.4 days, but because of the 2-day sample rate of the pole values\naliasing periods of 9 and 13 days appear in the spectrum.\nThe presence of the resonance effect in the pole values is not surprising.\nThe inadequacy of the resonance terms have been observed previously in analy-\nsis of long term orbit perturbations of the NNS polar orbits (Bowman, 1976).\nThe maximum perturbation of the orbit due to the major 28th degree 27th order\nterm represents approximately 20 meters along track for the majority of the\nNNS orbits. The amplitude of the variation in the pole values due to this\nterm was determined from a regression analysis of the 50 days of data for\nsatellite 68 shown in Figs. 4 and 5. The long period and secular variations","149\nSAT 58 (1967-34A)\nDay 183-235, 1976\n0.0\n-1.0\nSAT 59 (1967-48A)\n1.0\nDay 200-250, 1974\n0.0\n1.0\nSAT 60 (1967-92A)\nDay 300-350, 1973\n0.0\n1.0\nSAT 68 (1970-67A)\nDay 184-234, 1976\n0.0\n1.0\nSAT 77 (1973-81A)\nDay 99-151, 1976\n1.0\n0.0\nPeriod\n14\n12\n10\n9\n8\n7\n6\n5\n(Days)\n-1.0\n0.05\n0.10\n0.15\n0.20\n0.25\nFrequency (cycles/day)\nFig. 4 Power spectrums of the X pole component determined from Doppler\ndata of satellites 58, 59, 60, 68, and 77 using 50 day data spans during\n1973 - 1976.","150\nwere removed and an amplitude of 0.35 + 0.1 meter was obtained for both the X\nand Y components. The resulting standard deviations of the fits were 0.4\nmeter for either component. In comparison the pole values have been previously\nfound (Anderle, 1976) to have a standard error of 6 to 8 cm based on 2 days\nof Doppler observations, and a standard deviation of 0.6 m resulting from\nerrors in the gravity field. Thus, the standard deviation of the bi-daily\npole values can be conservately given as 0.4 meter after the 27th order reso-\nnance effect is removed, and the value is most likely even lower after all the\nother induced resonance variations are eliminated.\nSATELLITE\nCOMPUTED PERIOD\nOBSERVED PERIOD\n(DAYS)\n(DAYS)\n58\n27.8\n26.0\n59\n6.2\n6.0\n60\n8.7\n5.7\n68\n6.1\n6.1\n77\n5.1\n5.2\nTable 1. Computed and observed 28th degree 27th order\nresonance periods from X pole component data\nobtained from NNS satellites.\nThe low frequency spectrum of the pole values from 0 to 1.5 cycles/year\nwas analyzed next. Three and one-half years of continuous bi-daily Doppler\ndata were used. The data are comprised of pole results from orbit determina-\ntions of 5 different NNS satellites. The Maximum Entropy Method was used for\nthe spectral analysis to separate the annual and Chandler spectral peaks.\nThe MEM is especially suited to separating effects at very close frequencies\nusing a limited amount of data with regard to the frequencies involved. The\nimportant part of the MEM usage is the correct selection of the prediction\nerror filter length used for smoothing. The improved methods of filter length\nselection described by Ulrych and Bishop (1975) cannot be used because the\nspectra is highly periodic. Therefore, the spectrum of the pole components\nwas obtained using three different filter lengths of 50, 60, and 70 percent\nof the data span. These values were chosen based on the recent results of\nGraber (1975), who found an optimum length equivalent to 62-65 percent of the\npole data. Figure 6 shows the spectrum of the X pole component obtained using\nDoppler data from 1973 to mid-1976. The 50 percent filter length shown in\nFig. 6 smooths the spectrum too much, and the 70 percent filter length starts\nintroducing spurious details in the spectrum while smoothing out too much of\nthe real peaks present. The 60 percent filter length produces the sharpest\npeaks and the best separation of the annual and Chandler effects. This\nresult is in very good agreement with Graber's (1975) findings. The Chandler\npeak occurring at an approximately 450-day period is offset from the generally\naccepted 430-day period. However, Graber (1975) found the same shifting of\nthe period occurring for a number of data samples that he analyzed. The peak\nfrequency shift could be due to statistical variations from use of the Maximum\nEntropy Method noted previously by Ulrych, et. al., (1973), or possibly due to","151\nSAT 58\n0.0\nDay 183-235, 1976\n-1.0\n1.0\nSAT 59\nDay 200-250, 1974\n0.0\n-1.0\nSAT 60\n0.0\nDay 300-350, 1973\n-1.0\n1.0\nSAT 68\nDay 184-234, 1976\n0.0\n-1.0\n-2.0\nSAT 77\nDay 99-151, 1976\n0.0\n-1.0\n14\n12\n10\n9\n8\n7\n6\nPeriod\n5\n(Days)\n0.05\n0.10\n0.15\n0.20\n0.25\nFrequency (cycles/day)\nFig. 5 Power spectrums of the Y pole component determined from Doppler\ndata of satellites 58, 59, 60, and 77 using 50 day data spans during 1973 -\n1976.","152\n4.0\n50%\n3.0\n2.0\n1.0\n4.0\n3.0\n60%\n2.0\n1.0\n4.0\n70%\n3.0\n2.0\n1.0\n0.0\n0.5\n0.0\n1.0\n1.5\nFrequency (cycles/year)\nFig. 6 Power spectrum of the X pole component using continuous 2 day\nvalues from 1973 to mid 1976 determined from Doppler data of\nseveral Navy navigation satellites. Power spectrums are shown for\nprediction error filter lengths of 50, 60, and 70 percent of the data\nspan.","153\nsmall discontinuous phase shifts in the Chandler oscillation (Graber, 1975).\nThe annual peak is also shifted from one cycle per year, so the frequency\nshifts in Fig. 6 are most likely statistical fluxuations introduced by use of\na very short data span incorporating only three complete periods of the annual\nand Chandler variations.\nThe low frequency end of the spectrum was extended to 5.0 cycles per year.\nThe results of the X and Y pole component spectrums are shown in Fig. 7. A\n60 percent prediction error filter length was used. The difference in the peak\namplitudes in the X and Y components is due to the forcing functions of the\noscillations being more a function of one component than the other. As in\nFig. 6 one of the interesting features of the spectrum is the 1.3 cycles per\nyear peak in the X pole component. The origin of the oscillation is unknown\nbut it has been observed previously (Graber, 1975) using pole data obtained\nfrom optical as well as Doppler measurements.\nThe amplitudes of the periods shown in Fig. 7 were determined from a\nregression analysis of five years of Doppler data starting in the middle of\n1971. Table 2 lists the results of the least squares fits. The amplitudes\nobtained from the regression analysis do not correspond precisely with those\nobtained from the power of the spectrum shown in Fig. 7 because the MEM has\na tendency to amplify the maximum points of very periodic data. The amplitude\nof the 1.3 cycles per year frequency observed by Graber (1975) was one-half\nmeter, which is in excellent agreement with the value of 0.49 + 0.06 meter\nobtained in the regression analysis. The other frequencies listed in\nTable 2 have been occasionally observed but the amplitudes are so low compared\nto the data noise level that a real existence for these periods is questionable.\nFREQUENCY\nX\nY\nTOTAL\n(cycles/year)\n(meters)\n0.85\n4.04\n4.22\n5.84\n+ 0.06\n1.0\n3.55\n3.29\n4.84 + 0.06\n1.3\n0.47\n0.12\n0.49 + 0.06\n2.0\n0.19\n0.13\n0.23 + 0.06\n2.5\n0.10\n0.07\n0.12 + 0.06\n4.0\n0.10\n0.04\n0.11 + 0.06\nTable 2. Amplitudes of pole oscillations obtained from a\nregression analysis of 5 years of 2-day Doppler\npole values.\nConclusion\nThe standard deviation of the DMATC Doppler pole values can be conserva-\ntively given as 0.4 meter after the 27th order resonance effect has been\nremoved. Occasionally, a bias of one-half to one meter occurs in the data\nwhen comparing values between two NNS satellites. This difference cannot,\nat present, be definitely explained. Some of the effect can be attributed to","154\n4.0\nY Pole Component\n2.0\n0.0\n4.0\nX Pole Component\n2.0\n0.0\n0\n1.0\n2.0\n3.0\n4.0\n5.0\nFrequency (cycles/year)\nFig. 7 Power spectrums of the X and Y pole components using continuous 2\nday values from 1973 to mid 1976. A 60 percent prediction error filter\nlength was used with the Maximum Entropy Method.","155\ninadequate consideration of the resonant gravity effects, and some to the\nvariation of number and location of tracking stations for the different sate-\nllites, but some long term, unmodeled errors of small magnitude still exist\nin the data.\nThe Doppler bi-daily pole values appear to be very useful in resolving\nlong periodic polar motions of small magnitude. The annual and Chandler\nvariations can be well separated using the Doppler values with the Maximum\nEntropy Method of spectral analysis. Further analysis of longer data spans\nmay help resolve the nature of other periodic effects found in the data, such\nas the 1.3 and 2.0 cycles/year variations. Continuing investigations of\npolar motion through analysis of Doppler pole values will, hopefully, solve\nseveral of the problems previously observed and may eventually lead to a\nbetter understanding of the geophysical effects that are present.\nFuture DMA Participation in Polar Motion Determinations\nThe MEDOC experiment is concerned with the determination of polar motion\nby Doppler tracking of artificial satellites. The purposes of MEDOC are to\ndetermine to what extent and why various computer programs cause systematic\ndifferences in polar motion results, to promote satellite techniques for the\nstudy of Earth rotation, and to lay the groundwork for an international\nscientific service based on satellite techniques. The experiment has been\norganized by the Group de Recherche de Geodesie Spatrale (G.R.G.S.) and has\nreceived financial support from the Centre National de la Recherche\nScientifique, the Institut Geographique National and the Centre National d'\nEtudes Spatiales.\nThe tracking network for the MEDOC experiment will consist of four JMR\nreceivers, five TRANET stations, and four other receivers. DMATC will\nprovide the TRANET data from Australia, Japan, Canada, Belgium and Maryland\nas well as the data from the National Ocean Survey Geoceiver in Ukiah,\nCalifornia for the computation of the MEDOC ephemeris and polar motion.\nObservations of satellite 68 (1970-67A) will be used. The MEDOC group will\nin turn provide their JMR tracking data to DMATC for computation of the precise\nephemeris and polar motion using only MEDOC data. The two ephemerides will\nthen be compared as well as the polar motion results to identify any\nsignificant differences.","156\nReferences\nAnderle, R. J. , Determination of Polar Motion from Satellite Observations,\nGeophysical Surveys 1, 1973, 147-161.\nAnderle, R. J., Polar Motion Determined by Doppler Satellite Observations,\nBull. Géodés. , in press, 1976.\nBowman, B. R. , Determination of Geophysical Parameters from Long Term Orbit\nPerturbations Using Navigation Satellite Doppler Derived Ephemerides,\npaper presented at the International Geodetic Symposium on Satellite\nDoppler Positioning, New Mexico State University, New Mexico, October\n12-14, 1976.\nBurg, J. P., Maximum Entropy Spectral Analysis, paper presented at the 37th\nAnnual International Meeting, Soc. of Explor. Geophy., Oklahoma City,\nOklahoma, October 31, 1967.\nGraber, M. A., Polar Motion Spectra Based Upon Doppler, I.P.M.S., and B.I.H.\nData, Goddard Space Flight Center Report, in press, 1975.\nGuinot, B., Feissel, M., and Granveaud, M., Annual Report for 1970, Bureau\nInternational De L'Heure Report, Paris, 1971.\nKaula, W. M., Theory of Satellite Geodesy, Blaisdell, Waltham, Massachusetts,\n1966.\nMarkowitz, W., Earthquake Displacement Fields and Rotation of the Earth, eds.\nL. Mansinha, D. E. Smylie, and A. E. Beck, D. Reidel, Dordrecht-Holland,\n1970, 69-81.\nMarkowitz, W., Polar Motion: History and Recent Results, Sky and Telescope,\n1976, 99-103.\nO'Toole, J. W., The CELEST Computer Program for Computing Satellite Orbits,\nNaval Surface Weapons Center Report, in press, 1976.\nRochester, M. G., The Rotation of the Earth and Polar Motion, paper presented\nat the Second Geodesy/Solid-Earth and Ocean Physics (GEOP) Research\nConference, Ohio State University, Columbus, Ohio, February 8-9, 1973.\nUlrych, T. J., Smylie, D. E., Jensen, 0. G., and Clarke, G. K. C., Predictive\nFiltering and Smoothing of Short Records by Using Maximum Entropy,\nJournal Geophysics Research, 78, 1973, 4959-4964.\nUlrych, T. J., and Bishop, T. N., Maximum Entropy Spectral Analysis and Auto-\nregressive Decomposition, Review Geophysics and Space Physics, 13, No. 1,\n1975, 183-200.","157\nWagner, C. A., , and Klosko, S. M. , Gravitational Harmonics from Shallow\nResonant Orbits, Goddard Space Flight Center Report No. X-921-75-187,\n1975.\nYumi, S., , Annual Report of the International Polar Motion Service for the\nYear 1973, Central Bureau of the IPMS, Mizusawa, Japan, 1975.","158","159\nMEDOC EXPERIMENT OR THE FRENCH POLAR MOTION PROJECT\nB. Guinot\nBureau International de 1'Heure\nParis, France\nand\nF. Nouel\nGroupe de Recherches de Geodesie Spatiale\nToulouse, (GRGS), , France\nDefinition of the experiment; its purpose\nMEDOC is an experiment of determination of the pole motion by Doppler\nobservations of one of the Transit satellite for the years 1977-1978. As\nalready done so successfully by the Defense Mapping Agency, a global solution\nfor the satellite orbit and the coordinates of the pole will be computed.\nHowever, MEDOC will not be a mere duplication and there are several reasons\nto undertake it in the domains of Science, Promotion of new techniques,\nOperation.\n1. Science. MEDOC will use different stations from those of the DMA\nnetwork and a different model of force, independently established by the\nGRGS. The computing techniques are also independent. Although the campaign\nduration is too short for bringing interesting results on the motion of the\npole, comparative studies with the DMA results will be instructive; the\ninterest of these comparisons is enhanced by the DMA proposal to solve, in\naddition, for the polar motion the MEDOC data with its own techniques. In\nMEDOC, a special attention will be given to the problems raised by the\nchanges in the station network, since these changes are unavoidable in\npractice. If possible, we will consider the data compression at the level of\nthe stations.\nIt must be noted that MEDOC is simultaneous with the EROLD campaign\n(Earth Rotation by Lunar Distances).\n2. Promotion of new techniques. We feel that it is necessary to intro-\nduce the satellite techniques in the observatories. In many of them, there\nis a willingness to participate to these techniques. We hope that MEDOC\nwill provide with a forum for exchange of scientific ideas. It is our intent\nto circulate the available scientific information among the participants and\nwe hope that they will play an active role in evaluating the results and in\nseeking improvements.\n3. Operation. A central service on the Earth rotation dealing with the\nsatellite techniques could appear as a necessity within the next few years.\nBut the practical operation of such a service, on a current basis, and involv-\ning scientific institutions, is not sufficiently known. We feel that a full\nscale experiment will be most informative.","160\nThe station network\nThe general rule in establishing the station network was to seek the\ncooperation of foreign scientific institutions who can contribute not only by\nsending data, but by their scientific activity. Four french receivers (JMR\ntype) are available, their location was chosen in order to optimize the\nbalance of the network.\nSeveral of the scientific institutions involved in the project operate\nDMA Doppler receivers. We are most grateful to the DMA for releasing the\nobservation data of these stations and for their offer to tranmit to us these\ndata under a form which is particularly convenient.\nThe stations of the MEDOC network are (Fig. 1) from East to West (between\nbrackets, participation not yet certain) :\n(Orroral), Australia, Division of National Mapping.\nSmithfield, Australia, DMA station.\nMizusawa, Japan, International Lat. Obs., DMA station.\n(Tehran), Iran, National Geographic Organization.\nDjibouti, Territoire Francais des Afars et des Issas, French\nreceiver.\nPretoria, South Africa, French receiver.\nGraz, Austria, Technical University.\nWettzell, Fed. Rep. of Germany, Institut für angewandte Geodäsie.\nCagliari, Italy, Intern. Astronomical Latitude Station, ILS station.\nUccle, Belgium, Observatoire Royal de Belgique, DMA station.\nSao Paulo, Brasil, Instituto de Pesquisas Espacais, French\nreceiver on loan.\nOttawa, Canada, Earth Physics Branch, DMA station.\nWashington, USA, Applied Physics Laboratory, DMA station.\nMelville Island, Canada, Shell Canada Limited.\nCalgary, Canada, Earth Physics Branch, DMA station.\nUkiah, USA, National Ocean Survey, ILS station.\nTahiti, France, French receiver.\nManagement\nMEDOC has been prepared since the beginning of 1976, in order to set up\nthe network and to refine computer programs.\nThe variety of receivers and participating organisms draw up the\ngeneral following organization:\nData will not be sent on a real time basis, but by air mail\nonce a week.\nDMA is the focus point for all observatories or stations which\nare connected to it and these data will come on magnetic tape\nto the Bordeaux Observatory for processing.\nRaw data collected by JMR receiver are on a mini cassette and\nwill be read at Toulouse (several instruments of this type are\navailable in MEDOC experiement).","161\nIt is strongly wished that data from other receivers be sent\non magnetic tape, although for some of them, programs exist at\nGRGS for reading the data on paper tape.\nSome of the processing will be made on the French IRIS 80 computer of the\nBordeaux University and all the other computations will use the 7600 CDC Com-\nputer of CNES. It will be taken advantage of several years of GRGS experience\nin orbit determination, and in geodynamics for MEDOC. The steps through which\ndata will go can be summarized as described in Fig. 2, the fundamental program\nbeing the orbit computation where the pole coordinates will be determined.\nProcessing\nA reprocessing program was written for Doppler data (Fig. 3). The\noriginality comes from the association of analytical orbit computation for\na long arc with a pass by pass analysis using formalism given by Guier. As\nthe orbit is twisted so much to correspond to the measurements we add a pass\nby pass examination where bad data came out. We can, starting with all the\ndata on a given period, eliminate almost all the erroneous ones. It so\nreduces computer time for the further calculus.\nFigure 4 is an example of a pass analysis where two satellites in fact\nwere tracked and Fig. 5 shows results for a long arc where some error must\nhave occured for a period of time (it was a time datation error).\nPole Position Computation\nThe program is described on Fig. 6. It should be noted that the gravity\nmodel is hold fixed here, except for \"lump\" coefficients. Also, in general,\nthe coordinates of the stations must be known; but if a new station is added\nto the network, we can compute its position with respect to the others.\nSome uses of the program are shown in Figs. 7 and 8 where residuals of the\nalong track component gives information on the quality of the orbit\ndetermination.\nAmong the parameters which are solved for, pole coordinates are two of\nthem. Unfortunately, for lack of a good set of data, results concerning\nthese computations cannot be shown.\nData collected by MEDOC during the first months, will go through this\nprogram by periods of 8 to 15 days in order to prepare an earth model\nsuitable for polar satellite.\nEarth Potential \"Grim Polaire\"\nSo far, GRIM II Model has been published and the associated geoid is\nshown on Figs. 9 and 10. It is an artist description of the model, for it\nis not here the right place to describe it. Although GRIM II Model is good\n(as seen from agreement with other models, for example, by the profile of\nFig. 11, it is certainly not convenient to compute, accurately enough,\norbits of Transit satellites -- none of them took part in GRIM II determina-\ntion (Fig. 12) GRGS has the capability of computing the necessary improved\nEarth models (DYNAMO program).","162\nConclusion\nEven if MEDOC experiment will not solve all the problems tied to pole\ndetermination using orbits of satellites, it is hoped that the technique\nwill be a bit more promoted among the scientific community. In any case,\nsensitivity to various parameters (reference systems, earth potential,\nforces acting on the satellite, stations network), can be tested and estimated\nthrough different technics. With respect to the DMATC, if results are\ndifferent, comparisons will be instructive and, if the agreement is good, the\nmethod will be reinforced to the benefit of the scientific community.\nAcknowledgements\nMEDOC is made possible by the Groupe de Recherches de Géodésie\nSpatiale (France), , which includes teams belonging to the Centre National\nd'Etudes Spatiales, to the Institut Géographique National, to the Observa-\ntories of Paris, Bordeaux and Grasse (CERGA) .\nMEDOC is supported by the Centre National de la Recherche Scientifique.\nAs stated previously, the Defense Mapping Agency's cooperation and the\nobservatories contributions are essential factors in the development of the\nproject.","D\n-TEHRAN\n300°\nPRETORIA\na\nWETTZELL\nDUIBOUTING\nGRAZ\n*\nUCCLE\n0°\nD:\nDOS CAMPOS\nSAO JOSE\n*\n6.0°\nWASHINGTON\nOTTAWA\nFIG. 1 MEDOC network\nMELVILLE\nCALGARY\nUKIAH\n5\n120°\n*\n*\nPAPEETE\nYou\n180.°\nCORRORAL\nMIZUSAWA\nSMITHFIELD\nODD\n240°\nis\nB\no\n80,\nof\n70\n50\n30\no\n-30\n- 50\n7.0\n-80\n-\n-","164\nGRAVITY\nEARTH\nGRIM P.\nFIELD\n5\nPOLE POSITION\nSTATIONS COORDINATES\nORBIT COMPUTATION\nPREPROCESSING\nCOLLECTING\nFIG. 2\nDATA\n&\nEPHEMERIS","165\nBANK\nDATA\nPREPROCESSING OF DOPPLER DATA\nOrbital Parameters\nMaximum Values\nCorrections of\nWeight\nFrequencies\nOUTPUT\nINPUT\nFIG. 3\nPass with high\nAberrant Points\nELIMINATION\nPass too low\nPoints too low\nAf, Lo, Ro, 6\nPoints at 20\n26\nPASS BY PASS ANALYSIS\n+ L. Fs ( t-tc)\nGuier's formalism\nRESIDUALS\nLeast Squares on\nORBIT COMPUTATION\n+ R. Fa\nshort periods J2\nResidual = AF\nA F, Lo, Ro\nLeast Squares\nM quadratic\ne,i constant\nw,a linear","2000\n1ST ITERATION\n1000\nO\nAFTER CONVERGENCE\nTIME OF CLOSEST APPROACH\n- 1000\n2 MINUTES INTERVALS\nFIG. 4","COHERENCE\nINTERNE\n.042\n.008\n.048\n.008\n.010\n.088\n.007\n.050\n.057\n.049\n.027\n.028\n.104\n.010\n.076\n.094\n.035\n.116\nt-tc\nq-tc\n-255.4\n-98.2\n43.3\n-1.6\n4.2\n-150.0\n-160.7\n-40.7\n-160.1\n303.8\n171.5\n145.0\n256.5\n242.4\n127.9\n259.1\n-135.9\n-120.4\nLO\nm\nF(t-tc)\nRO\nm\n-134.4\n93.5\n97.1\n-127.3\n41.1\n-151.2\n-158.0\n135.6\n55.2\n-206.8\n-218.1\n116.5\n126.8\n98.2\n-237.8\n.224.4\n222.0\n-223.6\nLo\nRo\nto\nO2F\nHz\n.023\n-.127\n-.112\n.009\n=.131\n.040\n.011\n-.158\n-.145\n.024\n.018\n-183\n-.171\n-.175\n.056\n-.204\n-.205\n.064\nSTATION H MAX\n41.4\n17.5\n88.8\n18.7\n16.6\n86,2\n14.4\n46.3\n36.9\n31.2\n46.1\n23.4\n71.9\n13.9\n65.7\n60.5\n28.5\n61.9\n641.\n641\n641\n641\n641\n641\n641\n641\n641\n641\n641\n641\n641\n641\n641\n641\n641\n641\nFIG. 5\nRECAPITULATIF\n31\n55\n29\n59\n41\n4'4\n53\n39\n31\n54\n41\n5\n51\n38\n52\n3\n49\n3\nNB DE POINTS\n0\n9\n11\n13\n21\n23\n1\n10\n12\n22\n0\n10\n11\n13\n23\n12\n23\n11\n23\n23\n23\n23\n23\n23\n24\n24\n?4\n24\n25\n25\n25\n25\n25\n26\n26\n26\nDATE\n59\n54\n38\n52\n44\n56\n52\n64\n59\n58\n60\n56\n57\n52\n60\n42\n62\n61\n37\n56\n5\n5\n5\n5\n5\n5\n5\n5\n5\nS\n5\n5\n5\n5\n5\n5\n5\nS\nDATE ET HEUDE DE DEBUT\n1975\n1975\n1975\n1975\n1975\n1975\n1975\n1975\n1975\n1975\n1975\n1975\n1975\n1975\n1975\n1975\n1975\n1975\n49.\n55\n5\n5 25 23 52\n17\n3\n31\n41\n29\n59\n44\n53\n39\n31\n54\n41\n51\n38\n21\n3\nDE PASSAGE\nNUMERO\n0\n9\n11\n13\n21\n23\n1\n10\n12\n22\n0\n10\n11\n13\n9\n12\n11\n21\n5 26 23\nI\n2\n3\n4\n5\n6\n7\n8\n9\n10\n12\n13\n14\n15\n17\n18\n11\n20\nPASS.ELIMINES SI FREQ. SUP. 50.0 HERTZ\nPASS.ELIMINES SI RO SUP. 20000.0 METRES\nPASS.ELIMINES SI LO SUP. 20000.0 METRES\nPASS.ELIMINES SI SIGMA PASS. SUP. 5.0\n23\n23\n23\n23\n23\n23\nS 24\n24\n24\n24\n5 25\n25\n25\n25\n5 26\n26\n26\n26\nPTS ABERRANTS ELIMIN. 15000.0 CYCLES\n5\n5\n5\n5\n5\n5\n5\n5\n5\n5\n5\n5\n5\nS\n5\nPASS. ELIMINES INF. 12.0 DEGRES\nPTS . ELIMINES INF. 8.C DEGRES\nPASS EXTRAITS DU FICHIER\n1975\n1975\n1975\n1975\n1975\n1975\n1975\n1975\n1975\n1975\n1975\n1975\n1975\n1975\n1975\n1975\n1975\n1975\n1975\n1975\nprogram\nSATELLITE STATION\n641\n641\n641\n641\n641\n641\n641\n641\n641\n641\n641\n641\n641\n641\n641\n641\n641\n641\n641\n641\nBANCO\n700671\n700671\n700671\n700671\n700671\n700671\n700671\n700671\n700671\n700671\n700671\n700671\n700671\n700671\n700671\n700671\n700671\n700671\n700671\n700571\nDOP\nDOP\nDOP\nDOP\nDOP\nDOP\nDOP\nDOP\nDOP\nDOP\nDOP\nDOP\nDOP\nDOP\nDOP\nDOP\nDUP\nDOP\nDOP\nDOP","168\nFrequency and drift per station\nGIN PROGRAM\nDIFFERENTIAL CORRECTION\nPOLE POSITION COMPUTATION\nSolar pressure coeff.\nEarth potential coeff.\nOsculating elements\nStations coordinates\nIMPROVEMENT\nPole coordinates\nAir drag coeff.\nFIG. 6\nLEAST SQUARES METHOD\nNUMERICAL INTEGRATION\nSolar Radiation pressure\nPotential of the Earth\nPolar Motion effects\nEarth Tides effects\nLuni-Solar - effects\nFORCE MODEL\nCoriolis Forces\nAir drag","ALONG TRACK RESIDUALS\n169\n*\nGEOS 111\nSECOND OF ARC\n*\n*\n+\n* (DOPPLER)\n*\n6\n**\n*\n*\n*\n3\n*\n*\n*\n(LASER)\n*\n*\n*\nAA\na\nSYNCHRONISATION OF DOPPLER CLOCK\n(MAY 17)\nA\nA,\nA\n*\nA\n*\n*\n*\nA.K\n*\n*\nA\nA\n*\n*\nAFTER REMOVAL\nOF CLOCK DRIFT\n*\n20\n21\n22\n23\n24\n25\n26\n27\n28\nDAYS OF MAY 1975","*\nDISTINENT\n*\nORBIT","Ju\n64\n340\n320\n53\n300\n280\n-42\nO\n260\n-11\n-17\nGRGS BALMINO, / SFB CH. 78 REIGBER, - GRIM i/f=298.255 B.MOYNOT 2 GEOID (1976)\n240\n-42\n220\n19\n200\n180\n11\nFIG. 9\nO\na . 6378.155 Km;\n66\n160\n50\n4\n(82)\n140\n120\nG.\n45\n100\n-30\n-53\n50\n80\n-108\n50\n0\n60\n33\n40\n53\n8\n20\n50\no\n-80\n80\n60\n40\n20\no\n-20\n-40\n-60","172\nGRIM2 - GEOID\nBALMINO, REIGBER, MOYNOT (1976)\nFIG. 10","-----------\n173\n360\n320\nGRIM 2\nGEM 8\n280\n240\nPROFILE Q=40°\nSE III\nLONGITUDE A\n200\nFIG. 11\n160\nGEM 7\n120\nGRIM I\n80\n40\nGRAV.CEM8\nO\n80\n-60\n40\n20\nO\n-40\n-80\n-100\n60\n-20\n-120","h. h.\n10 000\n7 8 9 10 11 12 13 14 15 $ 000\n9\n8\n7\n6\n800\n5\n4\n3\n2\n600\n1\n0\n6\n70°\n80°\nGroutili\n640011\n630492\nFIG. 12\n90°\nG50811\n660051\n610281\nSFB 78\n100°\nprocessed by GRGS and\n110°\n120°\nSatellites","175\nSATELLITE TECHNOLOGY APPLIED TO\nANTARCTIC MAPPING PROGRAM\nW. R. MacDonald\nU.S. Geological Survey\nReston, Virginia 22092\nThe practicality of using Doppler positioning systems in Antarctica for\nestablishing much needed control for mapping required by U.S. and international\nscientists was demonstrated by USGS in 1972. Since 1973 Geoceivers have been\nused primarily by USGS to establish geographic positions for multidisciplinary\nscientific investigations on the Ross Ice Shelf, in Wilkes Land, and at the\nSouth Geographic Pole. For the first time during the 1975-76 austral summer,\nGeoceivers were used in Antarctica to establish control for mapping. This\nwas an international program designed to maximize the United States Antarctic\nResearch Program (USARP) and British Antarctic Survey (BAS) resources for\ntopographic mapping, positioning Landsat imagery, and tying previously inde-\npendent traverses together on a common geodetic datum in an area of mutual\nmapping interest. USGS provided scientific equipment, data preparation and\nanalysis, and two engineers who were both cross-trained and experienced in\nGeoceiver observations and conventional field surveys; BAS supplied extensive\nlogistic support, including accommodations and supplies, airplane (Twin Otter)\nand ship transportation, and manpower support.\nThe combination of Twin Otter airplane and Geoceiver proved to be ideal\nas 31 Doppler stations were occupied at 28 remotely scattered locations ranging\nfrom Seymour Island in the North Antarctic Peninsula southward to the Heritage\nRange of the Ellsworth Mountains (approximately 870,000 km2 2 ) Over the past\nfew years the Geoceiver has proved itself an essential polar surveying instru-\nment; however, when the technology is coupled with the highly mobile transpor-\ntation provided by the Twin Otter, it becomes also a most cost-effective\nsurveying system. This highly successful USGS/BAS program was an outstanding\nachievement of international cooperation in support of the objectives and\nprinciples of the Antarctic Treaty.\nIntroduction\nThe U.S. Geological Survey (USGS) mapping activities in Antarctica are\nin behalf of and funded under grants from the Division of Polar Programs,\nNational Science Foundation. Twenty years have elapsed since USGS began\nsending topographic engineers south to Antarctica--Earth most hostile\nenvironment. Their mission is to establish control to support the\nmapping needs of the U.S. Antarctic Research Program.\nBackground\nDuring the early years mapping control was established on an opportunity\nbasis by engineers using reconnaissance techniques on oversnow\nexploratory traverses and by survey teams traversing along the bases of\nmountain ranges in motor toboggans. However, because of increased\nscientific investigations in the early 1960's, there was a need to\nexpedite the mapping effort. Accordingly, in 1962 USGS undertook the","90\n120\n60\n30\n150\nMcMurdo Station\n1961-62\nPole Station\nLAND\nMAUD\nHallett Station\nFIG. 1\n1962-63\nIce Shelf\n180\nROSS\n1962-66\nRoss\n0\nQUEEN\nSEA\nSEA\n1962-63\n& 1963-64\n1967 - 68\n1966-67\n1969-71\n1967-68\n150\n30\nSiple Station\n120\n(Electronic Distance\nSeason(s) Accomplished\nANTARCTICA TRAVERSE\nThurston Island\nDates Indicate\n1968 69\nUNITED STATES\nMeasurement)\nAdelaide\nStation\nStation\nin\nPalmer\n60\n90","i°","178\nfirst Antarctic EDM traverse supported by Bell gas-turbine helicopters.\nThe operation proved so successful that it paved the way for a decade\nof multidisciplinary scientific and control operations by USARP.\nDuring this period USGS control teams established enough mapping control\nin Antarctica (fig., 1) to produce 88 1:250,000-scale topographic maps\n2\ncovering 950,000 km (fig. 2).\nA New Era\nThe 1972 launching of ERTS-1 (Landsat), which images the same area every\n18 days, paved the way to meet another NSF objective--the compilation of\n000,000-scale maps of Antarctica Experiments proposed and approved\n3\nunder USGS/NASA proposal SR-149 were directed toward this objective and\nthe needs of the polar science community for other imagery products.\nHowever, it was apparent that new technology would have to be introduced\n4,\n7\nto acquire the ground control needed to grid-fit\nthe imagery.\nDoppler positioning by the Navy Navigational Satellite System (NNSS)\nappeared to be the answer. Experiments were successfully conducted in\nAntarctica during the 1971-72 austral summer5 under the NASA proposal,\nto test the feasibility of using the NNSS.\nGeoceivers have subsequently been used by USGS field teams to establish\ngeographic positions for multidisciplinary scientific investigations on\nthe Ross Ice Shelf, in Wilkes Land, and at the Geographic South Pole5 5\nHowever, it was not until the 1975-76 austral summer that the NNSS was\nused for acquiring control for cartographic purposes.\nInternational Cooperation\nAn international cooperative project between the British Antarctic\nSurvey (BAS) and USARP in the Antarctic Peninsula-Ellsworth Mountains\narea, a region of mutual mapping interest, was undertaken during the\n1975-76 austral summer. The project area included the entire land mass\nfrom the tip of the Antarctic Peninsula southward to the Ellsworth\nMountains and east of 84° West longitude to the Weddell Sea. Mapping\nof this area of about 870,000 km 2 has proceeded much too slowly to\nmeet\nthe demands of both BAS and USARP scientists who need base maps to\ncomplete geological, glaciological, and geophysical reports. Landsat\nimage maps of this area should serve as interim base maps for meeting\nmost of these requirements until larger scale topographic maps are\npublished.\nThe project was designed to maximize the resources of USARP and BAS and\naccomplish the common goals of (1) tying various independent survey nets\ntogether on a common datum and (2) providing control for present and\nfuture conventional maps and Landsat mosaics. USGS provided scientific\nequipment, data preparation and analysis, and 2 engineers who were both\ncross-trained and experienced in Geoceiver observations and conventional\nfield surveys; BAS supplies extensive logistical support including\naccommodations and supplies from Adelaide Island, Twin Otter airplane\nand ship transportation, and support personnel; USARP provided airplane\nfuel from Siple Station.","FIG. 3\nAccomplished-1975-76\n1977-78\n1978-80\nPROGRAM\nFOR MAPPING\nDOPPLER\nPlanned","180\nProject Planning\nThe operational control plan was a joint effort whereby, on behalf of\nBAS, the Directorate of Overseas Surveys 6 undertook responsibility for\nthe Antarctic Peninsula area while USGS undertook responsibility for the\nremaining area (fig. 3). Plans were designed to:\nprovide adequate control for block adjustment of small and medium\nscale Landsat imagery and/or 1:250,000-scale reconnaissance maps,\nusing tricamera aerial photography.\ntie existing independent traverses established by BAS and USGS\nsurvey positions to a common datum.\nTo meet these objectives all previous control and fieldnotes were\nanalyzed, stations were then selected on the basis of distribution\nneeds and ease of access by air or ship, identifiability on aerial\nphotographs or Landsat imagery and ease of occupation by the Geoceiver\nobserving party. Before departure the USGS observers carefully studied\neach site by stereoscopic inspection of aerial photographs. Consideration\nwas given to the best possible approach to the proposed Geoceiver site\nand to alternative sites that might be needed if the area proved\nunsuitable for landing the Twin Otter. Final determination was of\ncourse left to the pilot. To aid the pilot, visual navigation packets\ncontaining aerial photographs or Landsat imagery and maps were prepared\nfor each site by BAS/USGS.\nTraining\nTwo primary types of training were provided for this project: basic\nGeoceiver operation; and refresher exercises in field survey methods.\nThe latter was provided at the USGS National Center by members of the\nresearch staff. Little time was needed for this phase as both team\nobservers were experienced in basic field survey methods. Training\nconsisted mainly of checking and organizing equipment.\nGeoceiver training was furnished by the Defense Mapping Agency Topographic\nCenter (DMATC). An excellent 2-week training course was taught by Alan\nJoll at the DMATC electronics laboratory near Herndon, Virginia. Principal\nsubjects were NNSS operations, elementary Geoceiver theory, operating\ntechniques, and troubleshooting.\nMajor Logistic Bases\nThe United Kingdom station, Adelaide (67°46'S, 68° 54'W), located on\nAdelaide Island off the west coast of the Antarctic Peninsula served as\nthe major staging area and resupply base for field operations. However,\nthe U.S. Siple Station (75°56'S, 275°45'W) in Ellsworth Land was used\nas a base camp for observation in the Ellsworth Mountains. This camp\nwas extremely important to the operation as the refueling point that\nenabled the Otter to extend its normal 300-n.mi. radius to 600-n.mi.\nfrom Adelaide Station. The fuel was prepositioned at Siple by a U.S.","181\nNavy VXE-6 Squadron LC-130 Hercules at the request of USARP. The fuel\nwas flown 1300 n.mi from McMurdo Station (U.S.) near Ross Island.\nOther bases used as temporary staging facilities included Stonington\nIsland (U.K., 68°11'S, 66°59'W), Fossil Bluff (U.K., 71°20'S, 68 3°17'W),\nPalmer Station (U.S., 64°03'S, 64°46'W), and the Argentine station\nMarambio (64°14'S, 56°43'W).\nField Operations\nWith excellent support and coordination by BAS, the first Otter sortie\nleft Adelaide Island on January 13, 1976, the day after the USGS men\narrived from South America on the R.R.S. John Biscoe. The field party\nincluded James W. Schoonmaker, Jr. and Karl W. Gatson (USGS), Geoff\nRenner (BAS geophysicist), and Giles Kershaw (pilot) Flying to\npreselected sites and landing as closely as possible, the party\nsimultaneously set up an emergency tent camp and the Geoceiver. In 9\ndays 12 stations were occupied. Two were primary stations required for\ntying the USGS Lassiter Coast traverses of 1970-71 and 1971-72 to the\nworldwide datum. The expedition returned to Adelaide on January 21.\nAlthough aircraft repairs and scheduling forced a slowdown in operations,\nthe party established a Doppler station at Marambio during the period\nJanuary 31-February 4.\nOn February 7 the party left Adelaide Island for the 570 n.mi. flight\nto Siple Station. Although USARP had closed the station for the winter,\npermission was given to use the emergency camp as a staging base for\nflights into the Ellsworth Mountains. Since the flights were far from\nBAS bases, they depended on fuel cached at Siple by USARP. The party\nthen flew south to the Ellsworth Mountains, tying the 1962-63 and\n1963-64 USGS traverses in the Heritage and Sentinel Ranges to the\nsatellite datum. Aircraft mechanical problems and extremely abnormal\ncommunications forced curtailment of flights from Siple. However, the\nDoppler station established at Siple during the 1974-75 season by Max\nVoight was reobserved before the return to Adelaide on February 12.\nData collected during the two seasons indicate the station is moving\ntoward the Bellingshausen Sea on an azimuth of 276° at a yearly rate of\n6.5 m.\nBetween February 3 and March 1, operating from Adelaide in short field\ntrips by Twin Otter and on 1 occasion by helicopter from H.M.C. Endurance,\nthe party established 8 more Doppler stations on the Antarctic Peninsula.\nOn March 4 transport shifted to the sea with the NSF research vessel\nHero supplying transport to 2 stations, 3 Doppler stations were established\nfrom the R.R.S. Bransfield during the return northward to Punta Arenas,\nChile. The last Geoceiver station was occupied on March 26, and the\nparty reached Chile on April 1.","182\nField Camp Procedures\nNormal station operation started after the pilot landed the Twin Otter\n(fig. 4) near a photoidentifiable point. The first task was to locate\nthe station and attempt to set the Geoceiver antenna over it. Where\nthis was possible the work consisted in setting up and then monitoring\nthe Geoceiver for the required number of passes. If an on-center setup\nwas not feasible, the antenna was set up at nearby location (fig. 5),\nselected so that the primary station, an adjacent station, and the\nantenna setup were mutually intervisible. If the primary station was\nnot monumented, a USGS Antarctic tablet (prestamped) was set at the\nphotoidentified point. The distance from the antenna to the primary\nstation was measured with an HP 3805A EDM instrument. Horizontal and\nvertical angles were measured with a Wild T-2 at the primary station.\nAzimuth was determined either by backsighting on a known station or\ntaking a sun shot. Time accurate enough for the sun shot was obtained\nfrom the Geoceiver. The local surveying was checked by measuring the\ndistance from the antenna site to the adjacent station and turning both\nhorizontal and vertical angles at the antenna site and the adjacent\nstation, which was generally unmarked and used only to provide a check\non the distance and direction between the primary station and the\nantenna.\nFor primary stations (established traverse stations) a minimum of 14\npasses of satellite 68 and/or 77 were observed. Because of the project\nlatitudes this normally took about 24 hours. For lower order (Landsat\nimage control) stations only 3 passes were observed--about 4 to 6 hours.\nFIG. 4 J.W. Schoonmaker measuring distance from Geoceiver antenna site to\nprimary station. Twin Otter in background.","183\nFIG. 5 Offset Geoceiver antenna set up for station located on Mt. Ruth\n(highest peak on left), , Alexander Island. Nanson sled was used\nto haul equipment to site from remote tent camp.\nConclusions\nThe combination of the Twin Otter plane and Geoceiver proved to be ideal\nas 31 Doppler stations (fig. 3) were occupied at 28 remote and\nscattered locations ranging from Seymour Island in the north Antarctic\nPeninsula southward to the Heritage Range of the Ellsworth Mountains.\nOf the 31 stations established, 18 were occupied on-center and 13\nrequired offsets. This was an outstanding achievement of international\ncooperation and personal effort. Over the past few years the Geoceiver\nhas proved to be an essential polar surveying instrument; however, when\nthe technology is coupled with highly mobile transportation, such as\nthe Twin Otter affords, it becomes a most cost-effective system for\nestablishing mapping control in Antarctica. The ski-equipped Twin\nOtter, owned and operated by BAS, is a most reliable and versatile\naircraft. In the hands of skilled pilots like Giles Kershaw, the Twin\nOtter may become the bush plane of the Antarctic.","184\nThe cooperation which made the BAS/USGS Doppler program so successful\nis characteristic of that which began in Antarctica following the International\nGeophysical Year (1957-58) and led to a most remarkable agreement--the Antarctic\nTreaty. USGS is pleased to be part of USARP support for international programs\nand share data and technical personnel with the other nations that signed the\nAntarctic Treaty.\nThe revolutionary effect that Landsat and Doppler satellites will have\non mapping Antarctica has been clearly demonstrated by the accomplishments of\nBAS/USGS project reported here. These two new systems should provide carto-\ngraphers with the answer to the double question of the spaceage \"what and\nwhere is it?\"\nFuture Programs\nThe USGS/BAS project proved so successful that a second one is being\nplanned for the 1977-78 austral summer (fig. 3), with subsequent control\nprojects for Landsat image mapping to follow. Plans are also underway to\nuse the NNSS system to tie all the independent traverses established by USGS\nbetween 1957 and 1970 (fig. 3) to a common datum. This work is tentatively\nscheduled to begin in 1980.","185\nReferences\n1.\n\"Topographic Mapping in Antarctica by the U.S. Geological Survey,\"\nGeorge D. Whitmore and R. B. Southard, U.S. Geological Survey,\nAntarctic Journal of the United States, vol. 1, no. 2, March-\nApril 1966\n2. Polar Research: A Survey, National Academy of Sciences, 1970,\nch. 5, p. 127, Cartography Recommendation No. 4 and 5\n3. \"The Cartographic Application of ERTS-RBV Imagery in Polar Regions\"\n1 April 1971, W. R. MacDonald, U.S. Geological Survey\n4.\n\"New Space Technology Advances Knowledge of the Remote Polar Regions\"\nW. R. MacDonald, U.S. Geological Survey, presented at the Third ERTS\nPrincipal Investigator's Symposium, December 1973, Washington, D.C.\n5. \"Antarctic Control Requirements Met by Doppler Satellites,\" R. B.\nSouthard, presented at the XIV Congress of the Federation Inter-\nnationale des Geometres (FIG), September 1974, Washington, D.C.\n6. Directorate of Overseas Surveys, Kingston Road, Tolworth, Surbiton,\nSurrey, KT5 9NS, England\n7.\n\"Gridding of ERTS Images,\" William H. Chapman, U.S. Geological\nSurvey, presented at the Fall Convention of the American Congress\non Surveying and Mapping, September 1974, Washington, D.C.","186","187\nTHE CANADIAN DOPPLER SATELLITE NETWORK\nJ. Kouba\nJ. D. Boal\nGeodetic Survey of Canada\nSurveys and Mapping Branch,\nDepartment of Energy, Mines & Resources,\n615 Booth Street, Ottawa\nAbstract\nGeodetic Survey of Canada has been extensively involved in Doppler\nSurveying for the past three years. During these operations more than 150\npoints were established, with an average separation of 300 km.\nThe field observation technique adopted by the Geodetic Survey of Canada\nwas designed to utilize both precise and broadcast satellite ephemerides, the\nlatter contributing mainly to an increased relative accuracy. The receivers\nas well as the reduction programs were developed in Canada.\nThe procedures for data reduction and analysis are briefly discussed\ntogether with preliminary results which indicate that a sub-meter relative\naccuracy in latitude and longitude has been achieved.\nIntroduction\nThe satellite Doppler positioning was introduced in Canada almost simul-\ntaneously by Shell Canada and the Bedford Institute of Oceanography (BIO)\n[Hittel, 1969; Wells, 1969]. At that time it was a new navigation aid with\nan accuracy of the order of 100 m. The University of New Brunswick (UNB)\njoined both BIO and Shell Canada in a satellite positioning experiment in\neastern Canada in the fall of 1970. [Hittel et al, 1971]. Additional tests\nwere done in 1972 and 1973 jointly by UNB and Geodetic Survey of Canada (GSC)\n[Krakiwsky et al, 1973; Kouba, 1974]. Both UNB and GSC actively participated\nin the designing and testing of the new Doppler instrumentation manufactured\nby the Canadian Marconi Co., receiver model CMA722. The GEODOP reduction\nprogram [Kouba & Boal, 1975] was developed within Shell Canada (1970-72) and\nGSC (1972-74). .\nThe first major GSC Doppler operation was conducted in 1974 using the\nimproved CMA722B with internal doppler count gating. More than 50 points in\nthe Canadian Arctic and Northern Quebec were occupied. (See Fig. 1). The\noperation as well as the evaluation of the new hardware is described in\n[Kouba et al, 1974; Kouba 1975]. In 1975, an additional 75 stations were\nobserved in Western Canada and in 1976 we have completed the coverage in\ncentral and northern Canada with the occupation of 50 points, including the\nreobservation of several at which poor quality data had been obtained in 1974\nor 1975. Eventually we expect to have almost 200 points at a spacing of\n200-500 km. In this paper field operations, experience in data quality\ncontrol and processing are briefly discussed. Also the utilization and analysis\nof Doppler results are discussed.","188\nField Observation During 1974-1976 Doppler Seasons\nThe Doppler field campaigns were conducted by the Supplementary Control\nSection of GSC. It was an operational challenge to co-ordinate up to 8\nreceivers deployed in semi-independent mode in such a remote area as the\nCanadian Arctic [Colwell, 1974, Macquarrie, 1975]. The transportation in most\ncases was provided by chartered or scheduled aircraft and in southern regions\nby vehicle. The observation pattern, basically the same for all three seasons,\nwas selected to yield increased relative accuracy with minimal increase of\nobservation time when compared to independent point positioning. The semi-\nindependent observing is done in groups, with at least one receiver kept\nstationary for the whole period of the group, while the remaining stations\noperate in an independent mode (See Fig. 2). Some overlaps between groups\nand seasons have to be ensured. In such a way, the expected relative\naccuracy is better than 0.5 m (10) level, in particular for neighboring points.\nThe most crucial stage in Doppler surveying is the detection of malfunc-\ntioning receivers while observing in the field. The early detection can save\nlarge amounts of money for transportation and re-observing. We at GSC have\ndevoted considerable effort to designing a simple and reliable field test.\nHowever, the most effective and ultimate test, though with 1-2 weeks delay,\nis our regular GEODOP processing using broadcast ephemeris. Other tests\nwe have tried with mixed results include: measuring reference frequency in\nthe field, computing second and third differences of Doppler counts, simple\ncurve-fitting to Doppler counts, and 2-D single pass fixes.\nA typical occupation period varies with latitude and so we require that\nat least 50 acceptable passes be collected of the satellites for which the\nU.S. Defense Mapping Agency (DMA) precise ephemeris is available. This may\nrequire 3-10 days depending on the number of \"precise\" satellites and station\nlatitude. Most observations were collected in an automatic acquisition mode,\nlocking manually only occasionally when conflict between \"precise\" and other\nsatellite existed. The reference oscillator was kept warm all the time, and\nany power interruption (e.g., stand-by battery failure) was recorded and at\nleast 24 hours was allowed for warm-up. The meteorological data was collected\nevery 4-6 hours or whenever the local weather abruptly changed. The Doppler\ndata was recorded on paper tape, shipped to the main camp where it was\nMajority-voted and then forwarded to the Ottawa GSC office for processing and\nquality control.\nReduction of Doppler Data\nThe Majority-voted paper tapes were first converted on to magnetic tape\nand preprocessed by programs PREDOP [Lawnikanis, 1975] and GEODOP with broad-\ncast ephemeris in point positioning mode. Resulting binary GEODOP edited\nfiles were saved for final processing. From this preprocessing important\nquality control analysis was done. For each receiver and season, the mean\nfrequency-offsets were plotted and frequency drifts computed (See Fig. 3).\nAnalogously, the receiver noise estimates were plotted for each station\n(Fig. 4). Also pass rejection and Doppler count rejection rates were closely\nmonitored (normally below 5% of PREDOP accepted data). Any irregularities in\nfrequency, drift, data noise and rejections might signify poor data quality.","189\nFor example, the o Receiver was much higher for receiver 110 during the period\nof operation with a less stable oscillator. (Fig. 4 and Fig. 3).\nFor the plots for frequency and data noise, the input values for the\nreceiver offset, drift and counting accuracy were assigned for each receiver\nfor the season.\nFigure 5 shows the schematic data flow and corresponding approximate\ncosts to GSC for GEODOP system processing. (Note that the higher figures\nare for GEODOP 15-station runs). The cleaned binary files for each station\nare consolidated into one multistation file for each group, then separated\ninto broadcast file(s), containing passes of satellites with broadcast ephemeris\nonly, and precise one(s) which contain the passes of \"precise\" satellite(s).\nAll the above file handling procedures are executed by program MERGE.\n[Lawnikanis, 1975b]. Then program GEODOP produces results on binary files\nfor both broadcast and precise solutions. These files contain the adjusted\nX, G Y, Z co-ordinates and variance-covariance (fully populated) matrices,\nfor points within the group. The final statistical testing is done\nautomatically, it includes: misclosure tests, tests of residuals and x2 tests\non each pass individually. Also the frequency plots are requested at all\ntimes and carefully checked along with the input program options and computed\nrejection rates. The standard options used for GSC processing are summarized\nin Table 1.\nUtilization of Doppler Results\nBroadcast and precise multistation solutions are adjusted independently,\ni.e., in three dimensions. The GEODOP variance-covariance matrices are aug-\nmented to reflect possible translation biases as suggested by [Kouba 1975a].\nb b\nb\n+ xyz G\n(1) =\nb Eb\nb b b\nwhere\nC\nb =\nG\nand is the fully populated, variance-covariance matrix from a GEODOP\nmultistation run (see Fig. 5 B, C) The diagonal elements in the bias variance-\ncovariance matrix b are assigned as C = 25m 2 for broadcast and C = 1m1 for\nprecise solutions. Then both precise and broadcast solutions are adjusted in\nthree dimensions, this time solving for rotation and scale parameters (broad-\ncast into precise). In the GSC 3D adjustment software this combination is\npossible in one run by directly accepting binary files produced by GEODOP.\nThis 3D adjustment then outputs the adjusted and l (combined precise and\nbroadcast solutions) transformed on to any selected datum (i.e., reference\nellipsoid, shift as Ax, Ay, Az rotations as WX, wy, WZ and scale changes)\nalong with the two-dimensional variance-covariance matrix Epr, which is used\nin GSC Section Adjustment (Helmert-Block type) of triangulation and Doppler\ndata. For more details see [Kouba, 1976b].","190\nNumerous combinations of broadcast and precise solutions augmented\naccording to eqn (1) provide a check on consistency of results and reliability\nof GEODOP variance-covariance matrixes . For large areas we have obtained\naverage variance factors of 3.3 and 2.0 for broadcast and precise combination\nsolutions respectively. These are larger than the statistically expected\nvalue of unity and indicate that error modelling improvements in GEODOP are\nrequired, in particular for larger areas. For small areas, the variance\nfactors were consistantly around the expected value unity.\nG\nFor the final combinations, all were scaled by a factor of 2.0 for\nprecise and 3.3 for broadcast, respectively. These values were obtained from\nthe adjustment of station groups for the whole 1975 season. A sample of this\ncombination are graphically represented in Fig. 6 by the relative error\nellipses between adjacent Doppler stations and numerically in Table 2 and\nTable 3. One can see that a high relative accuracy is implied, often below\n0.5m (10). Adjacent stations belonging to different groups have a lower\nrelative accuracy, e.g. REINDEER-STONEY.\nAccuracy of Doppler Network\nThe above accuracy estimates, strictly speaking, are yet to be confirmed,\nthe problem is the lack of sufficiently accurate standards in Canada.\nAnalyses reported earlier in [Kouba, 1975a; Kouba and Wells, 1976] used our\nprecise point positionings as the standard. The point positionings as\ndetermined by the U.S. National Geodetic Survey (NGS) and Naval Surface Weapons\nCenter (NSWC, formerly NWL) were externally tested by Anderle and Tannenbaum\n(1974) and Strange et al (1975). It remained, however, to verify our precise\npoint positioning, i.e. positioning using CMA722B hardware and GEODOP software.\nTogether with the NGS we observed several points side by side during 1974 and\n1975 seasons. The results for 1975 are summarized in Table 4, comparing the\nU.S. NGS preliminary results observed with Geoceiver and reduced by DOPPLR\n(Smith et al, 1976; Hothem, 1975) to GSC solutions (using CMA722B and GEODOP).\nWe notice a good agreement in and 1, but fairly large discrepancies in h,\nin particular the 4.1m value at station McKENZIE is puzzling. It may be\nconnected with the 6 metre metal tower used for both CMA722B and Geoceiver.\nThere are some differences in both GEODOP and DOPPLR mathematical formulations;\nthe first, a daily abberation-like effect which is included in GEODOP and NSWC\nsoftware and likely not in DOPPLR, probably caused the negative tendancy of\n-0.34m. (Prior to incorporating this effect into GEODOP the mean was 0.00m).\nThe second difference is a tropospheric refraction bias parameter not included\nin DOPPLR. It was observed that inclusion of this bias increases the height\nsolution by about 1.2m + 0.36 (RMS of individual differences) for Geoceiver\nand 0.5m + 0.30 for CMA722B, respectively. When almost the same (Geoceiver)\ndata at different stations with more than 30 passes, were processed by DOPPLR\nand GEODOP with the same options the mean difference was + 0.02m, + 0.03m and\n-0.14 with RMS of individual differences + 0.21m, + 0.15m and + 0.05 in 0, l\nand h, respectively [Kouba, 1975b].\nIn Table 5 the results of the NSWC program [Beuglass, 1975] for the\nCalgary Geoceiver are compared with the GEODOP position of a co-located\nCMA722B receiver. The agreement here is also quite good when one considers the\nlimited sample size, different Doppler count editing and the fact that NSWC","191\nalso inputs satellite clock errors which were not available for GEODOP\nprocessing. We notice a rather large o for Geoceiver 1, namely + 0.059\" as\ncompared to CMA722B + 0.036\", this is most likely due to hardware as an even\nmore significant deterioration is observed for Geoceiver l when the data is\nprocessed by GEODOP without tropospheric refraction bias. In the latter case\nO is increased from + 0.058 (see Table 5) to + 0.082\", while for the CMA722B,\nthere is almost no increase (+ 0.036\" to + 0.037\"). When this Geoceiver data\nis processed with GEODOP (70.5 elevation angle cut-off, 10% trop. refraction\nbias) and compared to NSWC results the RMS agreement was + 0.60m; + 0.43;\nand + 0.54m in 0, l and h with respective means of 0.15m; -0.20m and 0.37m.\nThe last test (summarized in Table 6) was primarily designed to check on\nground reflections and compare results obtained with CMA722B and TRANET hard-\nware. This test was partially prompted by the large difference in h in\nTable 4. Altogether one TRANET and 6 CMA722B receivers were used. Five\nreceivers were stationed outside Ottawa with antennae supported at different\nheights on metal towers, wooden towers or tripods and two stations were in\nOttawa, TRANET atop the Earth Physics Branch Geophysical Laboratory and D2\non the Surveys and Mapping Building of EMR. (Fig. 7). The differences with\nsurveyed positions shown in Table 6 and Fig. 7 are quite encouraging, O values\nnot exceeding 0.30m in and 1. The Ah is subject to errors in the approximate\ngeoid undulations used and possible instrumental bias between TRANET and CMA722B\nequipment. For the total 7 day period, excluding station Shirley B* and\nTRANET**, the RMS agreement is + 0.06, 0.10 and + 0.13m for 0, l and h\nrespectively with the means of -0.16; + 0.02 and + 0.24m. We note that this\nsignificant improvement over the accuracies quoted in [Kouba, 1975a; Kouba &\nWells, 1976] is due to simultaneous observation, short distances and some\nimprovements in CMA722B hardware in early 1975. Although the accuracies given\nhere may not be representative for longer distances, nevertheless they indicate\nthe potential of the CMA722B instrumentation and GEODOP reduction methods.\nSummary\nWe at the Geodetic Survey of Canada have developed and adopted unique\nobserving and reduction methods allowing the utilization of both precise\nand broadcast satellite ephemerides. The precise provides a high global\naccuracy (as well as within the national reference system), the latter con-\ntributes mainly to improved relative accuracy. A complex analysis during the\nfield and preprocessing operations and final reductions serve to minimize\nthe risk of acceptance of erroneous or poor quality data. Apart from this,\nthe final results are checked for consistency in separate three-dimensional\nadjustments, with more or less automatic data flow from Doppler reductions\nto the triangulation adjustments.\nOur hardware (CMA722B) and software (GEODOP) have been tested against\nthe Geoceiver and TRANET equipment and reduction methods of the U.S. National\nSHIRLEY B operated for 2 days only.\nTRANET station observed fewer passes -- only satellites for which precise\nephemerides are computed.","192\nGeodetic Survey and Naval Surface Weapons Center. For sufficiently large\nsamples (more than 30 passes) the agreement was within 0.70m in and 1. Some\ndiscrepancies were noticed in the options and mathematical modelling used by\nthe two U.S. agencies. The latest test indicated a potential relative accuracy\nfor the doppler system of the order of 0.10m from several days of simultaneous\nobserving.\nAcknowledgement\nThe cooperation of the Earth Physics Branch of E.M.R. and the U.S. National\nGeodetic Survey is gratefully acknowledged.\nReferences\nAnderle, R.J. and Mark G. Tanenbaum: \"Practical Realization of Reference System\nfor Earth Dynamics by Satellite Methods\". NWL Technical Report TR-3161,\nAug. 1974.\nBeuglass, L.K., \"Computation of Positions of Doppler Satellite Observing\nStations\", NSWC Technical Report TR-3173, June 1975.\nColwell, R., \"1974 Arctic Doppler Field Report\" Internal Report, Geodetic Survey\nof Canada.\nHittel, A., \"Use of Satellite Survey System in Offshore Exploration\".\nPresented to Annual Geophysical Conference, Royal Dutch Shell, Rijswijk,\nJune 1969.\nHittel, A., Kouba, J., Krakiwsky, E.J., Wells, D.E. and Eaton, R.M., \"Report\non a Doppler Satellite Positioning Experiment in Canada\". Presented to\n64th Annual Convention of the Canadian Institute of Surveying, Ottawa,\nFebruary 1971.\nHothem, L.D., \"Evaluation of Precision and Error Sources Associated with Doppler\nPositioning\". Preprint, August 1975.\nKouba, J., \"Reduction of Doppler Satellite Data Observed in Canada\". The\nCanadian Surveyor, Vol. 28, No. 5, 480-486, 1974.\nKouba, J., Peterson, A.E. and Boal, J.D., \"Recent Canadian Experience in\nDoppler Satellite Surveying\". Presented to 14th International Congress\nof Surveyors, Washington, September 1974.\nKouba, J., \"Doppler Satellite Control in Establishing Geodetic Control Network\".\nPresented to Canadian Geophysical Union Annual Meeting, Waterloo,\nMay 1975a.\nKouba, J. and Boal, J.D., \"Program GEODOP\". Geodetic Survey of Canada,\nOttawa, 1975a.","193\nKouba, J., , \"Some Doppler Satellite Receiver Comparisons\". A memo to C.D.\nMcLellan, dated Oct. 20, 1975b.\nKouba, J., \"Doppler Levelling\". The Canadian Surveyor, Vol. 30, No. 1, 21-32,\n1976a.\nKouba, J. and Wells, D.E., \"Semi-Dynamical Doppler Satellite Geodesy\". Bulletin\nGeodesique, Vol. 50, No. 1, 27-42, 1976.\nKouba, J., \"Proposed Geodetic Reference System for the 1977 Canadian Adjustment\".\nInternal report, Geodetic Survey of Canada, August 1976b.\nKrakiwsky, E.J., Wells, D.E. and Thomson, D.B., \"Geodetic Control from Doppler\nSatellite Observations for Lines Under 200 km\". The Canadian Surveyor,\nVol. 27, No. 2, 141-148, 1973.\nLawnikanis, P., \"Program PREDOP\", Geodetic Survey of Canada, 1975a.\nLawnikanis, P., \"GEODOP Utilities Programs\", Geodetic Survey of Canada, 1975b.\nLawnikanis, P., \"Program PREPAR\", Geodetic Survey of Canada, 1975c.\nMacQuarrie, D.L., GENERAL REPORT Doppler \"75\" Supplementary Control Section,\nField Report, Geodetic Survey of Canada, Ottawa, December 1975.\nStrange, W.E., Hothem, L.D., and White, M.B. (1975), \"The Satellite Doppler\nStation Network in the United States\". Presented to XVI General Assembly,\nInternational Association of Geodesy, Grenoble, August.\nSmith, R.W., Charles R. Schwarz, William D. Googe: \"DOPPLR - A Point Positioning\nProgram Using Integrated Doppler Satellite Observations\", Technical Report\nNo. DMATC 76-1, Defense Mapping Agency, Topog. Center, Washington, D.C.,\nApril 1976.\nWells, D.E. (1969), \"Experience with Satellite Navigation During the Summer of\n1968\". The Canadian Surveyor, Vol. 23, No. 4, 334-348.","194\nGEODOP Program constants:\nThe speed of light\nc=299 792.50 km / sec\nThe rotation rate of\nthe earth\nw=4.375 2691 X 10 3 rad/min.\nA priori var. factor\no2=1.00 count2\nA priori trop. refraction\nscaling bias o\no= +0.10\n(10%)\nHopfield\nhd = 40 136m\ntropospheric model height parameters\nhw = 11 000m\nEEODOP Program Options used for GSC processing\nPrint option:\nShort output\nTrop.Refr. Model:\nHopfield (Simplified) see [Kouba and Boal 1975]\nDoppler Cut off:\n7.5\nPlot Option:\nOne plot per station, i.e. frequency offset\nA priori var. factor:\n1.4 (corresponds to 30) used for statistical\ntesting only.\nPass Elev.Cut off:\n14.5\nRead Cont.file:\no when no continuation file is available.\nCorrelation:\no (uncorrelated Doppler counts)\nOrbital Biases (o) :\n26; 5; 10m for Broadcast, 2, 1, 2m for precise\nReference Ellipsoid:\nClarke 1866, i.e. a = 6378206.4m; b = 6356583.8m\nDatum Shift:\nAx=o;4y=o;Az=0.\nCo-ordinate card input:\nWeight constant per receiver and season;\ndelay=650usec for CMA722B; Tim.bias + 100usec;\nfrequency offset Af; drift determined from\npreprocessing (Step A, Figure 5) ; osf = 22HZ\nstation eccentricity input.\nDefault initial var. covariance matrix of (625m2) .\nProgram Constants and Options Used for GSC GEODOP Processing\nTABLE 1.","STANDARD DEVIATIONS (METRES)\n-.12036456E-01\n-.16675738E-01\n⑉.25262204E-01\n-.66612131E-01\n-.15909326E-01\n-.45367874E-01\n.14038054E-01\n-.11695744E-01\n.10840748E-01\n-.10838674E-01\n-32697141E-01\n-.57313611E-01\n-.46713936E-02\n⑉.32738408E-01\nHT\n,568\n,642\n.581\n.664\n.589\nLONG\n.648\n.772\n.646\n.786\n.663\n3-Dimensional Doppler Adjustment, Sample Co-ordinate Output\n.33818515E-01\n.45924381E-01\n.27552684E-01\n38399865E-01\n.20011452E-01\n.11905547E-01\n-.16402179-01\n.34914542E-01\n:.1144129E-01\n.29361723E-01\n.17145324E-02\n35073373E-01\n.30354590E-01\n.21184207E-01\n.18123132E-01\n.20957885E-01\nLAT\n.594\n.603\n.641\n.663\n.604\n.31616197E+00\n.31021698E+00\n.32260368E+00\n.30985105E+00\n.27882482E+00\n.26941531E+00\n.31174040E+00\n.31816508E+00\n.32296489E+00\n.32378921E+00\n.27488355E+00\n.28189069E+00\n.30881070E+00\n.32741105E+00\n.27421197E+00\n.31195577E+00\n.31341259E+00\n.27354195E+00\n249.988\n214,211\n20,130\n206,928\n-1.558\n(1975 Season)\nTable 2.\n55 44 8,85477 97 50 57.98809\n58 45 32.51994 93 59 22.84598\n52 59 13.76249 87 21 32.71954\n53 57 43,20054 90 22 55.17280\n52 55 24.31683 82 25 40.67832\n-.42923837E-01\n-.92255020E-02\n.90664706E-02\n-.11815994E-01\n-.33807040E-01\n-.27496603E-01\n-.35502897F-01\n-.16287838F-01\n-.10757952E-01\n.19435173F-01\n-.32866019E-01\n.14688796E-01\n-.33697591E-01\n-.14346406F-01\n-.29914690E-01\n-.32385956E-01\n-.11891797E-01\n-.17964100E-01\n-,23326215E-01\n-.19371704E-01\n-.12086021E-01\nLATITUDES, LONGITUDES AND HEIGHTS\nR= 6356583.800\n.15247646E-02\nT64420782E-01\n.30017340E-02\n.25220996E-01\n.46886942E-02\n.17311409E-01\n.52093614E-01\n.11330115E-01\n.14032991E-02\n.42502226E-02\n.92914114E-02\n.126996998-01\n-.26700799E-01\n.41512846E-03\n-.64992620E-02\n.59446601E-01\n.22228609E-01\n.46289726E-01\n.21328374E-01\n-.34727708E-02\n-.75453414E-02\n-.12398291E-01\n.15883326E-02\n-.14165469E-01\n6 6378206.400\nPHI-LAM-H VAR/COV. MATRIX\n714007\n673218\n664002\n723022\n673221\n.35282457E+00\n.31907511E+00\n.29948707E+00\n.41930245F+00\n34097464E+00\n.28788674E+00\n.32239571E+00\n.28178998E.00\n.25659494E.00\n.41124353F+00\n.30871,OHE+00\n.59547110E+00\n.31558440E+00\n.41168763E+00\n.27225728E.00\n.36338654E.00\n30287105E+00\n.41717935E.00\n.29798AB0E+00\n33759146E+00\n.26950102E+00\n.43989602E+00\n.61836545E+00\n.44133714E+00\n36466048E+00\n.43915339E.00\n.34693745E+00","1.92\n2.73\n1.86\n4.11\n4.48\n1.66\n1.43\n4.50\n1.64\n2.26\n26.58\n1.92\n1.43\n3.94\n2.52\n5.41\n2.73\n4.50\n3.94\n3.60\n4.59\n1,86\n1.64\n5.41\n3.60\n2.24\n4.11\n2.26\n2.52\n4.59\n2.24\n2.82\n2.29\n2.08\n1.18\n2.82\n2.56\n8.19\nR.A. = 2.45 x SEMI MAJOR AXIS/DISTANCE EXPRESSED IN PPM\nR.A\nPPM\n.78\n.99\n.76\n1.53\n1.52\n1.54\n.51\n.46\n.56\n.62\n9.78\n.78\n.46\n1.00\n2.21\n.97\n.99\n1.54\n1.00\n1.18\n1.63\n.76\n.56\n2.21\n1.18\n.89\n1.53\n.62\n.97\n1.63\n.89\n1.10\n.74\n.47\n.81\n1.10\n.75\n3.12\nPPM\nDIST\n,416\n.550\n.557\n.359\n.533\n,292\n.293\n,485\n.429\n.249\n.416\n.561\n.293\n.354\n.446\n.361\n.550\n.485\n,354\n.527\n.522\n.557\n.429\n.446\n.527\n.501\n,359\n.249\n.361\n.522\n.501\n.569\n.304\n.606\n,493\n.569\n.435\n.712\nM\n.11\n.17\n.26\n.38\n.11\n.13\n.11\n.30\n.12\n.19\n2.13\n.11\n.32\n.29\n.11\n.15\n.17\n.30\n.32\n.25\n.29\n.11\n.12\n.29\n.25\n.13\n.26\n.19\n.15\n.29\n.13\n.16\n.18\n.12\n.07\n.16\n.20\n.50\n2-Dimensional Doppler Adjustment, Sample Error Ellipse Output\nAZ\nAXIS (M) AXIS (M) MIN/MAJ SEC\nRATIO\n.67\n.60\n.69\n.63\n.83\n.70\n.70\n.56\n.68\n.67\n.85\n.67\n.70\n.58\n.64\n.65\n.60\n.56\n.58\n,59\n.58\n.69\n.68\n.64\n.59\n.66\n.63\n.67\n.65\n.58\n.66\n.60\n.71\n.65\n.65\n.60\n.64\n.63\nMIN\nSTANDARD ERROR ELLIPSES\n.280\n.372\n383\n.250\n.272\n.330\n,531\n.262\n.325\n.344\n.248\n.527\n.280\n.262\n,331\n,286\n.250\n.372\n.325\n.331\n.389\n.348\n.383\n.344\n,286\n.389\n.339\n,250\n.248\n.250\n.348\n.339\n.358\n.274\n.409\n.358\n.388\n.483\nSEMI\nMAJ\n.417\n.619\n,558\n.395\n,639\n,389\n.374\n.579\n,509\n.371\n.622\n.417\n.374\n,568\n.446\n.382\n,619\n.579\n.568\n,656\n.506\n.601\n,558\n,509\n.446\n,656\n.512\n,395\n.371\n,382\n.512\n.597\n.383\n.633\n.601\n,597\n.605\n.763\nSEMI\n(1975 Season)\nMAJ AXIS\nAPL AND NWL COMBINED\n92.57\n90.37\n93,06\n88.75\n89.81\n90.77\n92.60\n90.77\n93.49\n88.71\n90.76\n92.57\n92.60\n91.06\n93,45\n92,92\n90.37\n90.77\n91.06\n91.97\n90.59\n93,06\n93,49\n93.45\n91.97\n93.73\n89.81\n88.71\n92.92\n90.59\n93.73\n89.88\n95.07\n91.99\n90.29\n89.88\n92.20\n90.65\nOF\nTable 3\nAZ\nMEAN AZ\n88.28\n125.42\n90,18\n122.17\n7.36\n156.30\n31.79\n49,59\n46,45\n(DEG)\n176.71\n88.28\n31.79\n67.62\n145.61\n16.81\n95.22\n125.42\n49.59\n16.81\n44.24\n127,96\n90.18\n46.45\n95.22\n44.24\n77.38\n122.17\n176.71\n67.62\n127.96\n77.38\n112.35\n34.70\n114.10\n107.23\n112.35\n157.33\n118.39\n1.0000\n533.55\n555.36\n735.17\n235.22\n349.70\n575,22\n638.23\n315,37\n759.56\n402.32\n57,33\n533,55\n638.23\n353.52\n201.70\n370.77\n555.36\n315,37\n353.52\n446.37\n320.31\n735.17\n759.56\n201.70\n446.37\n561.14\n235.22\n402.32\n370.77\n320.31\n561,14\n518.40\n409.31\n746,47\n1048.44\n518.40\n578.62\n228.14\nDIST\n(KM)\nVARIANCE FACTOR =\nTEST GDLSAT CARD OUTPUT\nNAME\n593457A\n593457A\n593457A\n39 593457A\n39 593457A\n734020\n674100\n40 714007\n734011\n644000\n734020\n674100\n714007\n754010\n644000\n674104\n674100\n714007\n644000\n674104\n734020\n714007\n644000\n674106\n734020\n674100\n714007\n644000\n674104\n734020\n674100\n673218\n42 664002\n44 723022\n43 673211\n714007\n664002\n43 673211\nPRIORI\nSTATION\nTO\n37\n38\n39\n63\n35\n37\n38\n39\n40\n62\n35\n36\n38\n39\n40\n35\n36\n37\n40\n35\n36\n37\n38\n40\n35\n36\n37\n38\n41\n40\n42\nELLIPSES BASED ON THE A\nNAME\n39 593457A\nSTATION\n35 644000\n36 674104\n37 734020\n38 674100\n40 714007\n41 673218\nFROM","COMPARISON OF NGS (GEOCEIVER, DOPPLR) and GSC (CMA722, GEODOP)\nRESULTS ALONG U.S. - CANADIAN BORDER (SEE FIG. 1)\n3. Both CMA722B and Geoceiver elevated OIL 20 foot metal Lowers.\nNOTE: 1. Regular NGS (10° Doppler cut - off, no trop. refraction bias)\n+0.80\n+4.10\n1.62\n1.33\n0.81\n0.81\n0.27\n0.52\n1.28\n+1.22\nsh\nm.\nSimultaneous or near simultaneous observations\n-0.43\n-0.39\n+0.04\n-0.11\n-0.31\n-0.68\n-0.23\n-0.56\n-0.34\n+0.24\nAi\nn.\nTABLE 4.\nso\nm.\n+0.06\n-0.18\n+0.66\n-0.24\n-0.06\n-0.75\n+0.36\n+0.09\n-0.01\n10.42\nand GSC options were used.\nNGS\n46\n47\n50\n38\n49\n37\n35\n39\n#Passes\nGSC\n67\n69\n45\n72\n60\n160\n63\n67\nDIFFERENCE A\nSTATION NAME\n2,3\n2\n2\nGSC - NGS\nSATELLITE\n2\n2\nMcKENZIE\nFAIRHALL\n2.\nBONNERS\nSAGE 2\nSPEEDY\nHENRI\nMADOC\nmean\no","39.95 40.38 -.44\n39.93 39.82 0.09\n+0.70 +0.75 0.57\n0.70 +0.56 1.69\n0.7\n-0.3\n0.3\n-1.0\n39.7 40.5 -0.8\n39.6 39.9 -0.3\n40.0 40.7 -0.7\n39.1 40.5 -1.4\nAh\nm\nNSWC\n40.4\n41.2\n39.3\n40.5\nm\n41.1\n40.9\n39.6\n39.5\nGSC processing with 7.5 Doppler; 15° Pass cut - off criteria; 10% trop. refraction\nGSC\nsurveyed separation =0.130\"\nA1=0.078\"\nh\nAh=0.16m\nm\n(Dop.-Surv.)\n-0.46m\n0.15\n1.36\n1.62\n1.77\n0.96\n-0.71\n0.50\n+0.65\n+0.94\n0.45\n+0.91\nCOMPARISONS OF NSWC (GEOCEIVER) and GSC (CMA722 and GEODOP)\nAl\n(GSC-NSWC)\n22.703\n.689\n.649\n.578\n.603\n.670\n.722\n.754\n22.671\n+0.059\n22.683\n+0.058\nNSWC\n3. Solutions with at least 10 passes in both cases only.\n22.600\n.619\n.644\n.587\n.620\n.641\n.606\n.703\n22.628\n+0.036\n22.628\n+0.036\nGSC\ncut-off criteria\nResults at station CALGARY: o=50° 52' N\n1=242°42' E\nREMARKS: 1. Ellipsoid a = 6 378145;f =1/298.25; Ax=o;Ay=o;Az=0\n(Dop.-Surv.)\n-0.12m\n-0.78\n+0.30\n+1.20\n+0.60\n+0.54\n-0.18\n+0.60\n0.24\n+0.62\n0.43\n+0.80\nAO\nTABLE 5 :\nNSWC\n16.793\n.765\n.762\n.761\n.737\n.754\n.753\n.786\n16.764\n+0.018\n16.758\n+0.025\n\"\nWhen both stations processed by GEODOP\n1.0\n+0.025\n16.919\n.869\n.893\n931\n.887\n.902\n.877\n.936\n16.902\n16.902\n+0.025\nGSC\n\"\nNSWC\n14\n16\n15\n15\n11\n12\n10\n13\n13\n13\n\"\n*Passes\nNSWC\nGSC\n22\n13\n16\n18\n21\n19\n16\n10\n17\n17\n2.\n,\n3\nDAY SPAN\n180-184\n185-189\n230-234\n235-239\n240-244\n245-249\n250-254\n260-264\nmean\nmean\no\no","** Large but constant difference in in is due to expected (constant for all stations) bias in broadcast\nNot\n+24cm) for TRANET\n102/02 - 103/22.1976\ncm\n-124\n-137\n-123\n- 67\n-145\n-131\n-121\n+ 29\n-119\n+31\nGeoid Undulation difference used: (AN= +25cm) for D2\nSURVEYED - DOPPLER (GEODO? BROADCAST MULTISTATION) SOLUTION\nAt\ncm\n00\n01\n-22\n-65\n-21\n01\n-21\n27\n-27\n+28\nNo. of so\nPasses cm\n(AN=\n00\n44\n01\n-07\n14\n44\n19\n+24\n13\n+22\n27\n29\n30\n30\n31\n25\nmalfunctioning receiver\nAnd\n99/02 - 102/01,1976\nSHIRLEY BAY HEIGHT TEST RESULTS:\ncm\n70\n57\n54\n31\n32\n75\n46\n20\n53\n+14\nAt\ncm\n00\n27\n15\nSTATION SHIRLEY A & and l held fixed at surveyed values.\n04\n-12\n9\n9\n14\n+09\n+17\nAd\nPasses cm\n00\n12\n21\n40\n21\n-27\nTABLE 6\n+13\n25\n+23\n12\nNo. of\n57\n69\n65\n66\n62\n36\nAll\n96/02-99/02, 1976\ncm\n154\n141\n156\n151\n155\n110\n102\n139\n+22\n146\n+15\nOTTAWA 028\nAi\ncm\n00\n-44\n-08\n+04\n-11\n14\n-34\n-13\n+22\n9\n22\nsolutions with o = + 4m.\nso\ncin\n00\n15\n15\n-03\n18\n-03\n-54\n-2\n+27\n3\n10\nPasses\nexcluding TRANET station\nNo. of\n64\n53\n54\n58\n58\n44\n24\nPERIOD DAYS/HOURS\n(Antenna Support)\n(3m wood tower)\n(3m alum. tower)\n3m Alum. tower\nSTATION NAME\n*\nD2 (tripod)\nOTTAWA 028\nSHIRLEY A\nSHIRLEY B\nSHIRLEY C\nSHIRLEY 0\nSHIRLEY Z\n(tripod)\n(tripod)\nTRANET\nmean\nmean\no\no\n*","SATAHT\nBANK AZ.\nOGRAND\nSHEARWATER\nSATELLITE DOPPLER STATIONS\nNAROSARSSUAQ\nRED\nENERGY MINES AND RESOURCES\nCANCER\nCONSMERO\nSCALE 115840000 ONE INCH to MAS\nSMOKEY\nZAYAGE\nSURVEYS AND HAPPING BRANCH\nCANADA\nGEODETIC SURVEY\nROBINSONS\nDEPARTMENT OF\nSATELLITE\nTBIO\nHOFFMAN\n200K\nOBSERVED 1972 to 1975\nOGRANDE\nNATASHQUAN\nWHITE\nANSE\n0\nNBO\n30NDRESTROM\nMATANE\nPAUL\nOBSERVED 1976\nALDER\nCNB\nPLEASANT\nWHITE\nSQUAR\nBLUE\nBOULE\nBURWELL\nNAIN\nMARCON:\nSPLES\nPHONE 2\nPETITE\nLAUZON\nPTE.\nCATARAQUI\nROCK\nCHIMO\nEXPLORER\nDYER\nPAPA\nFROBISHER\nROOF TOPO\nMocARTHUR\ne\nCAPE CHRISTIAN\nGRIFFIN\nCARLING\nDEC\nSHORAN 03\nSHORAM\nDODIE\nACOSONEE\nBASIN\nCORSET AST.A\nMACE\nTIMKINS\nSUDJURY\nTRANET 018\nROOPER\nPOND INLET\nATTA\nDERVIC\nFIORD\nLOVER\nWHITE\nPIKE\nALERT\n.\nWINISK\nR.\nALEX\nMALLO\nREPULSE\nREPAIR\na\nGRISE FIORD\nLAST\nCARIBOU\nMCMENZIE E.D\nEUREXA\ndoral\n457A\nAFOTIC\nHOME\nBCARSKIN\nYORK ASTRO\nPAY\nCo\nCORNWALL\nBEARKIN\no\nWATER\nRESOLUTE\nSTOUY\nELLESMERE\nMAGNETIC\nSHORAN\nISLAND L.\nDAK\nHENR!\nISACHSEN\nTHOMPSON\nCAKER\nREINDEER\nSTONEY\nBLACK R.\nDUGHEED\nLYNN LAKE\nCULLEE\nLYE\nFIGURE 1: 1972-1976 DOPPLER SURVEYS\nEATONS\nPLUM\nVICTORIA\nWINTER\nSHOHAN\n#\n090\nCLOUDY\nBOUSKILL\nRUSSELL\nDUB\nMURPHY\nDRAW\nGILL\nFAIRWALL\n5\nBROCK\nWADEN\nBARINO\nRELIANCE\nWATROUS\nMOULD EAY\nYELLOPKY.FE\nRED CEES\nMADOC\n0\nHILL\nOZEBULON\nTURN\nSACHS\nECC.\nPEARCE\nKEELEY\nCOPPERMINE\nFORT\nDICDESLEIGH\nHOUSE\nLIND\nGREEN\na\nPRESERVO'R\nMAN.\nLAST\nSAGE\n*RIBLEY\nSIMPSON\nTANGENT\nASTRO'/\nTUK\nMARTIM\nE.S.\nRE/LEP\nWELLS\nBUE\nNORMAN\nTUNOSTEN\nNELSON\nROLLA\nBIOMA\nVAUX\nGALENA'M\nCANYON\nBOKMER3\nDEMPSTER\nN BASE\n@\nOLD FCRT\nROSS\nRIVER\nRAMPART\nIDA\nASTRO\nKOBAU\n4-HIRY\nBRASER\nBEAVER SR. AST\nOLDFIELD\nSATELLITE\n1334 126 0\nSPEEDY","201\nDAY NUMBERS - 1975\n135\n125\n15\n25\n453\n175\n285\n293\nFOR\n2\nO\nGROUP\nNUMBERS\n5\nI\n2\n3\n4\n5\n6\n7\n8\n9\n10\n11\n12\n10\n15\n20\n25\n30\nSTOLIFIES\n35\n40\nOF\nINVREE\n45\n50\nObservation period\n55\nDown time\n60\n65\nFIGURE 2 : TYPICAL OBSERVATION PATTERN\n70\n(1975 SEASON)","202\nRECEIVER FREQUENCY PLOT (1975 SEASON)\nRECEIVER\n30\n113\n113\n20\n110\n110\n10\n110\nRECEIVER\n110\n112\nREC.\n110\n0\n112\nlle\nRECEIVER\n116\n116\n113\n-10\n.20\n-30\n.40\nRECEIVER\n110\n-50\n102\n.60\n-90\n104\n.80\n-90\nRECEIVER\n102\nFOR\nRECEIVER\n103\n104\n.100\n.110\nRECEIVER\n103\n130\n140\n150\nIGO\n170\n180\n190\n200\n210\n220\n230\n240\n250\n260\n270\n280\n290\n500\n310\n1975 DAY NUMBERS\nFIGURE 3","203\nRECEIVER DOPPLER NOISE PLOTS (1975 SEASON)\n38\n37\n36\n35\n34\n33\n32\n31\n30\n29\n28\n27\n26\n25\nREGIENTE\n24\n23\n22\n21\n20\n19\n18\nRECEIVER 102\n17\nRECEIVER 103\n16\n15\nRECEIVER 104\n14\n13\nRECEIVER 110\n12\nRECEIVER 113\nRECEIVER 112\n11\n10\n230\n240\n250\n260\n270\n130\n140\n150\n160\n170\n180\n190\n200\n210\n220\n1975 DAY NUMBER\nFIGURE 4","204\nFIGURE 5\nDATA PROCESSING FLOW DIAGRAM FOR GEODOP\nProducing Fifted NWL Precise Ephemeris\nApproximate costs\nfor CDC 6400\nNWL\nNWL\n$ .02 pass\nSource\nNWLFIT\nFitted\nEphem\nEptein\nA. Single Station Broadcast Ephemeris\nMET. DATA\nPREDOP\nMJV\nPREDOP\nPREDOP\n07 20/ poss\nedited\nGECDOP\nData\n( PREPAR)\nOutput\noutput\nPREDOP\nPREDO!\nPREDOP\nPREDOP\noutput\noutput\noutput\noutput\n....\n(i)\n(ii)\n(iii)\n(ii)\nB. Multistation Broadcast\nMulti-\nEphemeris\nX,Y,2,\nMERGE\nstation\nGEODOP\n5\n3'm\n2 xyz\nInput\n$ 0.10 - 0.20. / pass\nC. Multistation Precise\nEphemeris\nHWL\nMerged\nx.y,2,\nFitted\nMERGE\nMulfi-\nGEODOP\n5\nEXYI\nEphem.\nStation\n$ 0.10 - 0.20/pass\nFormatted Data Files , the remaining files are binary. .\n*\nBroadcast : $ 0.30 - 0.40 /pass\nTOTAL COST :\n(for multistation GEODOP\n$ 0.32 - 0.42 /pass\nPrecise :\nprocessing of 2-15 stations)","205\nFIGURE 6\nRELATIVE ERROR ELLIPSES BETWEEN\nADJACENT DOPPLER POINTS (1975 SEASON )\nN\nDAK\n664002\nLYNN LAKE\n644000\nYORK ASTRO\n734020\n457A\n593457A\nTHOMPSON\n714007\nGROUP 4\nBEARSKIN\nISLAND LAKE\nREINDEER\n673218\nGROUP 5\n674100\n754010\nSTONEY\n674104\nLAST\nATTA AZ.\n673211\nGROUP 10\n723022\nSCALES\nELLIPSES\no\n2\nm.\nDISTANCES\no\n100\n200\n300 km.","02\ne\nG\nOTTAWA 028\n3 km\n1.00m\nTRANET\nDOPPLER ERROR ELLIPSE (16)\n10 F\nDOPPLER (GEODOP BROADCAST\n2km\nMULTISTATION) POSITION\n0.50m\nN\n5m\n1km\nPERIOD : DAY / HOURS : 96/02 - 103/22 , 1976\nSURVEY POSITION\n0\n1\n0\nO\nRIVER\nERROR VECTORS: :\nSHIRLEY BAY HEIGHT TEST POSITIONS\nDETAIL :\nMAP :\nOTTAWA\nLEGEND :\nSCALES:\nFIGURE 7\nSHIRLEY B\n0\nSKIRLEY C\n0\n&\nSHIRLEY o\n0\nA\nSHIRLEY is\n(See Detail Below)\nSHIRLEY A\n(hold fixed)\nSHIRLEY\nQ.","207\nTHE NATIONAL GEODETIC SURVEY DOPPLER SATELLITE\nPOSITIONING PROGRAM\nWilliam E. Strange\nLarry D. Hothem\nNGS/NOS/NOAA\nIntroduction\nThe Doppler satellite positioning method has supplanted all other satellite\nmethods as the primary means of establishing a world geodetic system, both\nbecause of the accuracy of the method and the rapidity, ease, and low cost\nwith which stations can be established. Using the Doppler positioning method,\nit is now feasible to consider relating all geodetic networks to a common\ngeocentric coordinate system with an accuracy of one to two meters. More-\nover, through placement of Doppler stations at locations where measurements\nby other techniques have been made, it is possible to relate local datums\nnot only to the Doppler coordinate system, but also to a desired geocentric\ncoordinate system defined by the CIO pole and the BIH zero meridian. By\nplacement of Doppler stations at VLBI and lunar and satellite laser ranging\nstations, it is possible to derive overall scale for networks accurate to\n1:5,000,000 or better. Also, Doppler stations can be used to contribute\nto the internal accuracy of networks by using the Doppler positions directly\nwith ground survey data in network adjustments.\nThe National Geodetic Survey (NGS) is using Doppler satellite positioning\nfor all of the above purposes in support of the new adjustment of the North\nAmerican Datum in the United States scheduled for completion in 1983. This\npaper will discuss the Doppler observation and reduction program, the accu-\nracy of the available Doppler data, and the use of Doppler positions to\nplace the new network in a desired geocentric coordinate system and scale\nit properly. The Doppler results are also used to define the distortions\nin the 1927 NAD. Other papers at this symposium (Dracup 1976, Moose and\nHenricksen, 1976, Meade, 1976) discuss studies underway at NGS aimed at\ndefining the best mode of using Doppler positions to support network ad-\njustment.\nThe Observational Program\nIn support of the new adjustment of the North American Datum (NAD), the\nNational Geodetic Survey has undertaken a program aimed at establishment of\napproximately 200 Doppler stations within the United States. Thus far,\n126 stations have been established in the conterminous 48 states with reduc-\ntions completed for 120 stations. Observations at four additional stations\nprior to the end of 1976 will complete this aspect of the observational\nprogram. Some 18 stations to be used in the new NAD adjustment have been\nestablished thus far in Alaska and Hawaii. Additional stations will be\nestablished in the states of Alaska and Hawaii as well as in Puerto Rico,\nthe Virgin Islands, and other U. S. territory during 1977 and 1978.","208\nThe observation program in the conterminous 48 states has been carried\nout by field teams of the NGS and of the Defense Mapping Agency Topographic\nCenter (DMATC). In Alaska, observations carried out by the Bureau of Land\nManagement (BLM) will be used to support the new adjustment of the NAD as\nwell as observations carried out by NGS. Observations taken by all agencies\ncontributing to the program were obtained using the AN PRR-14 receiver\n(i.e., the Geoceiver). The observation program was initiated in April\n1973.\nStandard field procedure has been to observe at least 40 passes from the\nsatellite(s) for which precise ephemerides would be available. During\nthose periods when precise ephemeris data were available for two satellites,\n5 to 6 days were normally required to obtain the 40 passes. When precise\nephemeris data was available for only one satellite, some 10 to 12 days\nwere required to obtain sufficient data. Only passes where the satellite\nrose more than 10° above the horizon were considered. At all stations,\nthe measurement point on the Geoceiver antenna was connected to a ground\nsurvey monument which is a part of the NAD network. Weather data were\nrecorded during each pass for use in making tropospheric refraction correc-\ntions.\nDuring the course of the observation program, it was necessary to carry\nout reobservations at a number of stations because of instability of the\noscillator in the receiving equipment. As explained in Hothem (1975), the\nmalfunctioning of the oscillator could be identified at the time of data\nreduction because of the effect on computed bias parameters.\nMethod of Computation and Presentation of Results\nAll data reduction has been carried out using the point positioning method\nin conjunction with the precise ephemeris, an ephemeris produced after the\nfact using tracking data from some twenty worldwide stations. Since January\n1973, the precise ephemeris have been produced using the same gravity field\n(NWL 10E) and the same set of coordinates (NWL 9D coordinates) for the\nstations providing data for the computations. Further details on the pre-\ncise ephemeris can be found in Anderle (1976). Prior to 1976, the precise\nephemeris data were provided to NGS by the Naval Weapons Laboratory;\nsince\nthat time, they have been provided by DMATC.\nData reduction was carried out using a computer program developed by DMATC\n(Smith, Schwarz, and Googe, 1976). This program has been converted, with\nminor modifications, to the NGS computer. In summary, the program holds\nfixed the input ephemeris data and solves for station position and several\nbias parameters in order to obtain a best fit between observed and computed\nintegrated Doppler counts. Bias parameters are also solved for in the\nprogram. These bias parameters are: (1) a receiver delay, assumed constant\nfor the period of occupation of the station, and (2) offset between satel-\nlite and receiver clock time and offset frequency between ground receiver\noscillator and satellite oscillator, both assumed to be pass specific biases.\nThe solution is iterative, beginning with initial estimates of station posi-\ntion and bias parameters. The unknowns are then differentially corrected\nthrough several cycles. Iteration continues until the sum of coordinate","209\nposition changes during an iteration is less than one meter. Iteration\nthen stops after one additional iteration. At each step of the iteration,\nthose integrated Doppler counts which have residuals greater than three\ntimes the standard deviation of the difference between observed and com-\nputed Doppler counts are eliminated from subsequent computations. Except\nfor the occasions when entire passes are rejected due to interference from\nanother Doppler satellite, the amount of data rejected is typically 2 to 3%\nand rarely exceeds 5%.\nTable 1 presents the Doppler derived station positions obtained for 126\nstations using the reduction procedure described above. The reductions\nfor the bulk of the stations were carried out by NGS. However, reductions\nfor 17 of the stations observed early in the program were carried out by\nDMATC. These stations are marked by an asterick in Table 1. Although\nthe same computer program was used, the solution methods of NGS and DMATC\ndiffered slightly. In the NGS solutions, the precise ephemeris during each\npass is represented by a polynomial fit to values of satellite X, Y, Z taken\nat one minute intervals. In the DMATC solutions, the polynomial fit is\nmade to values of satellite X,Y,Z taken at two minute intervals. Reprocessing\nby NGS of data for four of the stations originally processed by DMATC in-\ndicates that systematic differences between the two types of solutions may\nexist at about the half meter level and that the random error in the DMATC\nsolutions may be slightly larger.\nAccuracy of Doppler Results\nValues for accuracies and/or precisions of Doppler station positions have\nbeen presented by a number of investigators previously. However, it must\nbe recognized that accuracy and precision numbers derived by one investi-\ngator cannot automatically be applied to the results of another investigator.\nThis is true because each investigator's results depends upon a large number\nof factors including:\n1) The accuracy of the ephemeris data used.\n2) The capabilities of the data reduction program.\n3) The capabilities and operating condition of the receiving equipment.\n4) The number and distribution of satellite passes used.\n5) The geographic location of the stations.\nThis section gives estimates of the precision and accuracy of the station\npositions given in Table 1. Thus, these precisions and accuracies may be\nsaid to apply to station positions meeting the following conditions. The\nstations were located on the North American continent. Positions were\nderived using data from approximately 40 satellite passes. All observa-\ntions were made subsequent to January 1973. Thus, all precise ephemerides\nused were produced using the NWL 10E gravity field and the NWL 9D coordinate\nset for tracking stations providing data for orbit computation. Data reduc-\ntion was carried out using the computer program described in the previous","210\nsection. The following discussion deals only with results obtained by NGS.\nAs explained in the previous section, a few of the results presented in\nTable 1 were obtained by reductions carried out by DMATC. However, these\nare being re-reduced by NGS at the present time to obtain a uniform set\nof results obtained by a common reduction process.\nAn important test of the precision of Doppler derived positions is compari-\nson of repeat determinations. Some of the primary sources of error - orbit\nerror and ionospheric and tropospheric refraction - have potential long\nperiod effects. Therefore, it is necessary to have the repeat determinations\nwell separated in time to get realistic estimates of precision. To arrive\nat a precision estimate for the NGS derived Doppler positions, comparisons\nwere made of repeat position determinations at four stations - Kingman,\nArizona; McChord AFB, Washington, Calgary, Canada, and Beltsville, Maryland.\nThere were 10 repeat determinations at Kingman over a seven month period,\n12 repeat determinations at McChord over a thirteen month period, 13 repeat\ndeterminations at Calgary over a seven month period and 5 repeat determina-\ntions at Beltsville over a 30 month period. Table 2 indicates the standard\ndeviations at each station for a 30 to 40 pass solution. The results for\nthe four stations are reasonably consistent except for the LONG at Calgary\nwhich is at least twice as large as values for the other stations. There is\nsome indication of a time/frequency stability problem at Calgary which may\naccount for the poorer longitude precision. To remain conservative precision\nfigures of LAT = .5 m, LONG = 1.0 m, and HT = .5 m are considered to\napply to the positions given in Table 1.\nA number of investigators have demonstrated that the Doppler results as\npresented in Table 1 must be reduced in scale by about 1.0 ppm (Anderle, 1974,\n1975, Strange, et. al., 1975). Once such a scaling is applied, the question\narises as to whether the above mentioned precisions can be considered as\naccuracies of positions in the coordinate system defined by the precise\nephemerides. This question must be answered by comparison with external\nstandards.\nOne external standard with which Doppler derived station positions can be\ncompared is ground survey data. The most accurate horizontal position data\navailable from ground survey in the United States is the transcontinental\ngeodimeter traverse data. Even though only preliminary adjustments of por-\ntions of the traverse have been made thus far, it still serves as an excellent\nbasis for evaluation. Indeed, beginning with the initial evaluations of\nportable Doppler equipment and continuing through the comparisons of\nAnderle (1974), Meade (1974) and Strange, et. al. (1975), the preliminary\ngeodimeter traverse positions have been used as a basis for evaluating\nDoppler positioning in the United States.\nTo carry out a three-dimensional comparison, the latitudes and longitudes\nobtained from the geodimeter traverse must be combined with ellipsoid heights.\nTo obtain ellipsoid heights, elevations above sea level from leveling were\ncombined with astrogeodetic geoid heights derived by Carroll and Wessells\n(1975) from a recent simultaneous adjustment of all astrogeodetic deflection\ndata in the United States.","211\nTable 1\nDoppler Derived Coordinates\nSTATION\nX\nY\nZ\nNUMBER\nmeters\nmeters\nmeters\n53002\n1,130,769.75\n-4830830.14\n3994701.15\n51003\n1,097,028.79\n-4897252.77\n3923111.84\n51004*\n732,263.42\n-4953431.48\n3937856.75\n51005*\n523,305.69\n-5076315.23\n3813714.44\n51006*\n465,504.99\n-5200166.84\n3651815.98\n51007\n726,445.40\n-5206375.51\n3600228.70\n51008*\n1,085,993.59\n-5178330.33\n3549772.19\n51009*\n326,478.97\n-5337543.80\n3464992.73\n51010*\n660,605.37\n-5309973.17\n3459666.57\n51011*\n1,017,856.34\n-4975965.47\n3845273.02\n51012*\n401,614.56\n-5477079.93\n3232726.60\n51013*\n717,289.42\n-5594041.55\n2968690.23\n51014*\n924,916.88\n-5561535.20\n2972315.52\n51015*\n966,695.27\n-5659642.02\n2768155.17\n52016\n813,423.35\n-4692614.97\n4228853.07\n51017\n1,138,337.88\n-4683261.00\n4163941.43\n51018\n1,062,415.82\n-4450417.48\n4428816.58\n51019\n1,321,178.95\n-4540588.28\n4265743.21\n51020\n1,300,902.67\n-4333792.74\n4480147.76\n51021*\n1,631,121.89\n-4469385.11\n4233641.57\n51022*\n1,586,590.27\n-4263277.41\n4455807.10\n51023\n1,587,514.48\n-4041129.03\n4657017.32\n51024\n- 518,990.17\n-5556368.83\n3077968.50\n51025\n- 344,038.01\n-5466536.56\n3257067.56\n51026\n- 464,943.51\n-5295234.36\n3513312.70\n51027\n- 370,581.45\n-5141652.19\n3743945.09\n51028*\n- 145,598.36\n-5126254.61\n3779956.29\n52029\n- 411,073.94\n-4926738.64\n4016664.52\n52030\n- 719,197.66\n-5130171.36\n3708947.39\n51031*\n143,659.13\n-4986581.32\n3961023.14\n.\n51032*\n- 87,917.51\n-4918783.49\n4046085.67\n51033*\n- 469,094.59\n-4746142.64\n4221337.39\n51034\n- 741,622.03\n-5692259.24\n2770717.83\n51035\n- 769,561.71\n-5536270.61\n3062087.56\n51036\n-1,016,166.57\n-5505363.46\n3046258.29\n51037\n-1,121,478.38\n-5423223.96\n3154560.87\n51038\n- 945,782.79\n-5203893.75\n3553591.80\n-\n51039\n-1,133,183.27\n-5361657.59\n3254068.39\n51040\n-1,004,259.71\n-5036964.74\n3770525.72","Table 1 (Cont'd)\n212\nSTATION\nX\nY\nZ\nNUMBER\nmeters\nmeters\nmeters\n51041\n- 960,010.34\n-4676960.76\n4216638.32\n51043\n-1,427,089.14\n-4303659.35\n4472482.74\n51044\n-1,459,157.34\n-4548825.60\n4215240.08\n51048\n-1,483,440.82\n-5020819.14\n3633940.86\n51049\n-1,256,639.97\n-5179951.84\n3493397.69\n51050\n-1,752,943.40\n-4979907.37\n3570350.67\n51051\n-1,941,461.73\n-4785066.73\n3734765.25\n51052\n-1,969,990.83\n-4997204.26\n3428455.56\n51053\n-1,376,002.06\n-5374187.54\n3138585.25\n51054\n-1,661,777.05\n-4795420.33\n3852734.24\n51055\n-1,916,696.87\n-4598311.49\n3971949.84\n51056\n-1,813,679.79\n-4495449.79\n4133350.66\n51057\n-2,072,378.90\n-4402418.88\n4112669.96\n51058\n-2,377,392.26\n-4291496.97\n4064082.45\n51059\n-2,250,494.71\n-4387504.64\n4034603.90\n51060\n-2,096,032.14\n-4602059.49\n3876192.83\n53063\n-2,595,521.78\n-4396788.29\n3809778.53\n51064\n-2,495,084.95\n-3721003.80\n4524502.67\n52066\n-2,371,754.23\n-3901370.75\n4439929.42\n51067\n- 753,907.73\n-5303702.30\n3450649.92\n51068\n789,224.05\n-5432220.05\n3236970.56\n51069\n880,918.03\n-5296209.16\n3431476.64\n52074\n-2,499,048.58\n-4026269.64\n4256537.07\n52075\n-1,709,059.90\n-4016686.32\n4636571.04\n52076\n-1,027,545.50\n-4133961.15\n4732147.37\n52077\n733,110.59\n-4206233.13\n4722985.58\n-\n53078\n- 504,181.24\n-4401608.35\n4573265.08\n52079\n- 475,686.85\n-4580203.99\n4399142.25\n51081\n349,607.87\n-4399882.10\n4589158.19\n51082\n417,734.60\n-4597009.50\n4387146.99\n51089\n-2,641,085.09\n-4272274.07\n3917876.47\n52091\n83,163.28\n-4613707.35\n4388773.61\n52092\n- 124,726.07\n-4600837.02\n4401319.86\n52093\n-1,907,451.46\n-3857571.43\n4693740.50\n51094\n1,322,005.12\n-4612276.87\n4188821.37\n51095\n1,539,185.82\n-4393301.31\n4345745.53\n51096\n893,863.08\n-4583885.31\n4329568.48\n51097\n-1,602,839.35\n-4164871.01\n4543616.92\n51098\n-1,112,005.68\n-4059549.52\n4777133.89\n51099\n-1,872,327.15\n-3782452.86\n4766756.83\n51100\n-1,457,179.18\n-3917902.92\n4802527.38\n51101\n589,950.65\n-4687476.16\n4270717.81\n51102\n- 319,835.80\n-4203688.11\n4770521.86\n51103\n-1,535,168.36\n-5188528.79\n3367869.03\n51104\n-1,371,922.84\n-4069031.95\n4701610.70","Table 1 (Cont'd)\n213\nSTATION\nX\nY\nZ\nNUMBER\nmeters\nmeters\nmeters\n51106\n155,319.16\n-4404478.27\n4595737.25\n51114\n883,205.71\n- 492449.75\n3944063.62\n51118\n1,492,394.11\n-4457297.99\n4296815.08\n52119\n- 224,792.73\n-4412066.85\n4585420.46\n51121\n- 207,602.30\n-5488959.86\n3230851.15\n51122\n1,144,801.12\n-4967117.08\n3820914.99\n51123\n-1,330,900.03\n-5328746.25\n3235639.19\n51124\n- 957,586.11\n-5386102.43\n3269607.20\n51125\n290,740.94\n-5486903.19\n3227998.01\n51126\n594,707.80\n-5466582.57\n3220838.96\n51127\n-2,127,824.42\n-3785852.64\n4656032.36\n51135\n-2,330,239.83\n-3544013.64\n4747553.80\n51142\n- 699,287.47\n-4109484.56\n4811821.38\n51143\n86,012.77\n-4227653.63\n4759227.63\n51144\n- 734,991.40\n-4893187.55\n4011979.55\n51153\n- 695,702.53\n-5468226.58\n3198128.54\n51154\n339,280.90\n-5385761.22\n3388536.42\n51155\n-2,614,851.09\n-3857206.23\n4340743.10\n51158\n-1,121,108.12\n-4303993.44\n4557707.50\n51159\n-1,823,068.10\n-4120040.12\n4501241.45\n51160\n-2,028,546.56\n-3984179.54\n4535554.14\n51161\n-2,206,788.49\n-4803121.46\n3557907.69\n51166\n354,907.68\n-4863115.14\n4098110.36\n51167\n26,204.80\n-5459942.61\n3285917.11\n51168\n346,074.66\n-5051239.98\n3866276.55\n51169\n160,892.98\n-5241611.36\n3618673.43\n51170\n- 93,191.76\n-5324579.00\n3498355.71\n51171\n-2,274,513.12\n-4200276.64\n4214569.52\n51172\n-2,011,714.55\n-4294021.34\n4253950.39\n51174\n59,978.83\n-4833305.63\n4147653.09\n51175\n- 203,500.29\n-4757260.60\n4229715.90\n51176\n702,138.60\n-4836092.03\n4085530.60\n51177\n-1,760,665.02\n-4392392.69\n4264386.52\n51900\n-2,335,505.62\n-3667356.69\n4650987.58\n51920\n-2,126,096.30\n-4766080.14\n3656367.04","214\nTable 2\nStandard Deviations of Doppler Position Determinations\nNUMBER\no LONG\nLAT\nHT\nSTATION\nOF\n(meters)\n(meters)\nNAME\nSOLUTIONS\n(meters)\nKINGMAN\n10\n.51\n.74\n.35\nMcCHORD\n12\n.32\n.73\n.58\nCALGARY\n13\n.34\n1.43\n.36\nBELTSVILLE\n5\n.23\n.47\n.72\nBefore comparisons could be made between Doppler and traverse positions,\nit was necessary to place them in a common coordinate system. This was\ndone by deriving a set of six transformation parameters - three transla-\ntions and three rotations. In the solution, a scale parameter was also\nderived. The seven parameters were derived using data at 45 Doppler sta-\ntions located along the traverse. The Doppler positions were held fixed\nand a least squares solution carried out to derive the seven parameters\nwhich are presented in Table 3. These parameters are Bursa transformation\nparameters as defined in Leick and von Gelder (1975).\nAfter transformation, the standard deviation of the difference between\nDoppler and astrogeodetic geoid heights was 0.74 meters. Accepting the\nstandard deviation of the Doppler radial coordinate determination of 0.5\nmeters given above would imply a combined standard deviation for the error\nin elevation above sea level plus the error in astrogeodetic geoid height\nto be 0.54 meters. It seems unlikely that the combined random error from\nthese two sources would be much less than indicated by this standard devia-\ntion. Thus, this comparison is entirely compatible with considering 0.5\nmeters for the standard deviation of a Doppler height to be a measure of\naccuracy.\nAt the meter and submeter level, it is difficult to estimate the accuracy\nof the Doppler latitudes and longitudes by comparison with the adjusted\ntraverse data. Strange, et. al. (1975) noted that the differences between\nDoppler and traverse horizontal positions varied systematically with respect\nto position along the traverse indicating distortions in the traverse. With\nadditional Doppler stations reduced in a uniform manner located along the\ntraverse, the systematic nature of the differences is now even more pro-\nnounced. Recent work at NGS has indicated clearly that this systematic\ndifference will be largely eliminated once a final adjustment of the traverse\nis carried out. Results presented by Meade (1976) at this symposium have\novercome this difficulty by comparing Doppler derived interstation distances","215\nTable 3\nParameters to Transform Doppler Positions\nto\n1927 NAD Positions\nMR 72 Parameters\nRotations\nTranslations\nScale\n(seconds of arc)\n(meters)\nY to Z\nZ to X\nX to Y\nAX\nAY\nAZ\n.90\n+.09\n-.01\n-.167\nppm\n+22.6\n-156.9\n-175.8\n+.14\n+.06\n+.03\n+. 03\n+ 1.1\n1.3\n+\n+\n1.5\nModified Parameters\nRotations\nTranslations\nScale\n(seconds of arc)\n(meters)\nY to Z\nZ to X\nX to Y\nAX\nAY\nAZ\n.9 ppm\n+.09\n-.01\n-.167\n21.6\n-157.0\n-176.4","216\nalong the traverse with distances obtained from free adjustments of segments\nof the traverse. Meade obtains mean differences between Doppler and traverse\ninterstation distances of 0.50 meters for traverse segments running north-\nsouth and differences of 0.65 meters for traverse segments running east-west.\nThese results indicate that the standard deviations of .50 meters for latitude\nand 1.0 meters for longitude are reasonable conservative estimates of the\naccuracy of the properly scaled Doppler coordinates.\nEstimates of standard deviations in the 0.5 to 1 meter range are compatible\nwith comparisons between Doppler results and VLBI, lunar laser ranging, and\nDSN results as reported in Strange, et. al. (1975). As stated at the outset,\nthe precision and accuracy of Doppler position determinations are a function\nof the reduction method used. The precisions and accuracies reported above\nrefer to the results presented in Table 1. We are presently improving the\nexisting reduction program. Considerable improvements in the precisions\nreported in Table 2 have already been achieved through modifications in the\nprogram (Hothem, 1976). Work is continuing at developing and implementing\nadditional program improvements. Once the program has been optimized, it is\nanticipated that all stations will be reprocessed to obtain final values for\nuse in the 1983 NAD adjustment.\nDatum Transformations and Distortions in the 1927 NAD\nFrom the outset of satellite geodesy, one of its primary aims has been to\nprovide a means of accurately relating all geodetic positions to a common\ncoordinate system. Until recently, the number of satellite stations located\nat points whose geodetic positions were referenced to any given local geodetic\ndatum was small. Moreover, the accuracies of the satellite positions were\nin the +5 to 10 meter range. In this situation, distortions existing in local\ngeodetic networks could not be well defined. It was, therefore, natural to\nseek three parameter (three translations) to seven parameter (three transla-\ntions, three rotations, and a scale constant) sets of transformation constants\nwhich would best transform the local datum positions at the tracking stations\ninto the satellite positions and thus relate them to a geocentric coordinate\nsystem. The three translations and three rotations so derived were referred\nto as datum transformation parameters. These datum transformation parameters\nwere the best available estimates of the origin and orientation differences\nbetween the coordinate systems in which the local datum and satellite positions\nwere expressed.\nNumbers of sets of datum transformation parameters and scale differences have\nbeen derived by different investigators. For any given geodetic datum,\nthese have differed. The differences reflect a number of factors including\ndifferences in the coordinate systems to which the different satellite solu-\ntions were referenced, random errors in the satellite derived positions, and\ndistortions in the geodetic networks referenced to a local datum. Using the\nDoppler satellite method, we are now obtaining large numbers of satellite\npositions at stations referenced to individual local datums. Moreover, the\nrandom errors associated with these Doppler derived positions are at the\nsub meter level. Thus, it seems time to rethink the question of how we wish\nto derive the relation between local geodetic coordinates and satellite\ncoordinates.","217\nThe primary factor to take into account is that to make full use of the\nDoppler satellite results, no single set of seven parameters will be adequate\nto describe the relation between distorted local datum positions and undis-\ntorted positions expressed in either the satellite coordinate system or some\nother desired geocentric coordinate system. Instead, one must define, not\nonly a seven parameter set to describe coordinate transformation and scale\ndifferences, but also a set of parameters to define the distortions of the\nlocal geodetic network.\nThe following approach was taken with respect to the 1927 NAD. It was assumed\nthat the MR-1972 coordinates along the traverses represented nearly undis-\ntorted 1927 NAD coordinates. Thus, the parameters obtained for transforming\nthe MR 1972 coordinates to the Doppler coordinates were considered to be\nrepresentative of coordinate system differences between the 1927 NAD datum\nand the Doppler coordinate system. The remainder of the differences between\n1927 NAD network positions and Doppler positions were assigned primarily\nto distortions in the local geodetic networks. Using the MR 1972 derived\ntransformation parameters, the differences between the transformed 1927 NAD\nposition and the Doppler position at MEADES RANCH, the origin of the 1927\nNAD were AX = .99, AY = .11, and AZ = .64. The MR 1972 transformation para-\nmeters given in Table 3 were modified by these amounts to give the modified\nseven parameter set of Table 3. The modified set of parameters given in\nTable 3 is considered to be the set of parameters relating the coordinate\nsystem in which the 1927 NAD positions are expressed and that in which the\nDoppler positions are expressed. Several comments can be made concerning the\nchoice of the modified parameter set of Table 3 to use as the mean transforma-\ntion between 1927 NAD and the NGS Doppler coordinate and scale systems.\nFirst, the modification of the three MR 1972 translations to make the differ-\nences at MEADES RANCH equal zero may seem arbitrary. The justification\nbehind this is as follows. By definition, the position of the origin point\nof a local datum relative to the coordinate system of the datum is error\nfree. Thus, if differences exist after transformation between the geodetic\nand Doppler coordinates at MEADES RANCH, they must be caused by either (a) an\nerror in the Doppler derived position at MEADES RANCH or (b) errors in the\ntransformation parameters due to distortions in the MR 1972 and errors in\nDoppler positions or, as is more likely, a combination of (a) and (b). By\narbitrarily making the Doppler and geodetic positions agree after transforma-\ntion, we are assured that the given transformation brings the two coordinate\nsystems together to within the accuracy of the Doppler position at MEADES RANCH.\nSecond, it might be argued that it would be more logical to solve directly\nfor six transformation parameters and a scale parameter using the 1927 NAD\nand Doppler positions for stations. This seems reasonable since, regardless\nof what seven parameter set is used, additional parameters will be needed to\ndefine the 1927 NAD distortions. A justification for not taking this approach\nfollows. It must be kept in mind that the geoid heights used in defining\nthe 1927 NAD coordinates are, in fact, totally unrelated to the latitude and\nlongitude coordinates. As noted previously, the geoid heights used were\nthose derived by Carroll and Wessells (1975). In a previous section of this","218\npaper, the MR 1972 transformations were shown to give exceptionally close\nagreement between the Doppler and transformed MR 1972 height coordinates.\nIf one solves directly for a seven parameter set using 1927 NAD and Doppler\npositions to the Doppler system, the average height coordinate residuals\nare actually increased over those obtained using MR 1972 transformation\nparameters. This indicates that the distortions in the horizontal positions\n(i.e., latitudes and longitudes) in the 1927 NAD are partially absorbed\ninto the transformation parameters, thereby degrading the fit to the vertical\ncoordinate. This is clearly an undesirable situation. Also, the modified\nMR 1972 transformation parameter set gives a better fit to the horizontal\ncoordinates at Doppler stations in Alaska than does the seven parameter set\nobtained using the 1927 NAD positions in the conterminous 48 states.\nFigures 1 and 2 indicate the distortions in the 1927 NAD in the conterminous\n48 states of the United States. The distortions are in the form of latitude\nand longitude deviations in meters, obtained by differencing transformed\n1927 NAD positions (using the parameters of Table 3) and the Doppler posi-\ntions. The question arises as to the possible causes of the distortions\nillustrated in Figures 1 and 2. It is tempting to try to relate the bulk\nof the distortions to some systematic error, such as the suggestion by Leick\nand von Gelder (1976) that scale distortions might be, to a large extent,\ndue to the fact that geoid heights were not available to permit a reduction\nto the ellipsoid. However, it appears that the answer is quite simply that\nthe data available at the time of the initial 1927 NAD network adjustment\nin the 1920's was not sufficient in some parts of the country to support\na greater accuracy over long distances than 10 to 15 meters. In adjusting\nmore recent surveys to the network, positions obtained in the initial adjust-\nments were held fixed. In the course of adjusting recent, more accurate\nsurveys, it had become clear that errors existed in the initial adjustments.\nFor example, the existence of substantial distortions along the Canadian\nBorder from Lake Superior westward to Idaho has been well known for several\ndecades. The results shown in Figures 1 and 2 are useful in allowing defini-\ntion of distortions in the 1927 NAD. The parameters of Table 3, together with\nFigures 1 and 2, will permit the transformation of Doppler positions to 1927\nNAD coordinates.\nFor a somewhat different application, Vincenty (1976) has used the Doppler\ndata to predict approximate changes of coordinates of map corners from the\n1927 NAD to the 1983 NAD.","219\nScale, Reference Ellipsoid and Coordinate System\nThe Doppler satellite station positions will play an important part in\nestablishing the overall scale and defining the coordinate system for the\n1983 NAD as well as establishing the semimajor axis of the reference ellip-\nsoid to which 1983 NAD positions will be referenced.\nWith regard to scale, the Doppler positions, themselves, do not define scale.\nHowever, they serve as an intermediary to allow intercomparison of other\nmethods of establishing scale. Strange, et. al. (1975) found that geodimeter\nbaselines in the United States, VLBI baselines, and lunar laser ranging and\nDeep Space network spin axis distances were all reasonably consistent with\nregard to scale. All of these sources of scale information indicated that\nthe Doppler derived positions of Table 1 should be reduced by 1.0 +.2 ppm\nto be correctly scale. This is in agreement with the previous work of\nAnderle (1974) who found that his Doppler results should be reduced by 1.1 ppm\nto agree with a worldwide set of geodimeter baselines. Also, the World\nGeodetic System Committee of the Defense Mapping Agency had found that NWL 9D\nresults had to be reduced in scale by 0.83 ppm to agree with other results\n(Seppelin, 1974)\nActivities now underway should allow refinement of the scale somewhat more\nover the next two to three years so that the final overall scale of the\n1983 NAD is accurate to +0.1 ppm.\nObservational activities are presently underway which will result in a pre-\ncision of 0.2 m for Doppler positions at the Haystack, Massachusetts, Green-\nbank, West Virginia, Goldstone, California, and Ft. Davis, Texas VLBI sites.\nNASA programs over the next few years can be expected to establish intersta-\ntion baselines between these sites with an accuracy of better than 0.1 m.\nThe observations at Goldstone will also provide a high accuracy Doppler posi-\ntion for comparison with DSN spin axis distance. High accuracy Doppler posi-\ntions are also planned for the lunar laser ranging stations at McDonald\nObservatory and Haleakela, Maui, Hawaii. These measurements should permit\ndefinition of scale to the 0.1 ppm level, equivalent to about 0.5 m error\nin the scale of the earth's semimajor axis.\nMeasurements already made and those additional measurements described above\nwill clearly provide quite adequate scale for the 1983 NAD adjustment. However,\nit would be highly desirable if high accuracy Doppler results could be estab-\nlished at VLBI, lunar laser ranging and DSN sites on a worldwide basis. This\nwould permit worldwide integration of VLBI, lunar laser ranging, DSN and\nDoppler coordinate systems at about the 20 centimeter level.\nOnce Doppler derived positions have been properly scaled, they can be used\ntogether with gravimetric geoid information and heights to derive the semi-\nmajor axis of the best fitting reference ellipsoid to which the 1983 NAD\ncoordinates can be referenced. Through comparison of geoid heights computed\nusing the scaled Doppler positions with the gravimetric geoid heights of\nMarsh and Vincent (1974), Strange, et. al. (1975) derived an ellipsoid","220\nsemimajor axis of 6378.131 kms. More recently, the Doppler stations have\nbeen compared with other geoid computations. Rapp and Rummel (1976), taking\ninto account atmospheric corrections in computing geoid heights, have derived\na semimajor axis of 6378.135 +.002 kms. Lachapelle (1976) has derived a\nsemimajor axis using GEM 8 geoid heights and Canadian and U. S. Doppler\nstations of 6378.130 kms with values between 6378.130 and 6378.133 when\nsurface gravity data was combined with the GEM 8 gravity field in computing\ngravimetric geoid heights. It seems clear that the comparison of scaled\nDoppler positions and gravimetric geoid heights gives best fitting ellipsoid\nsemimajor axis values in the range 6378.130 and 6378.135 kms.\nAn alternate method of computing the semimajor axis of the best fitting\nellipsoid is through the use of GMe (Me = mass of the earth) and mean equa-\ntorial gravity, Ye. Values of GMe+a (Me+a = mass of the earth plus atmosphere)\nhave been derived by Williams (1975) who obtained 398,600.49 km3/sec based\n2\non lunar ranging data and Esposito and Ng (1975) who obtained values of\n398,600.65 +.4 km³/sec2 from analysis of Mariner 9 data and 398,600.45\n+.4 km³/sec2 from Mariner 10 data. All of these estimates are based on\na speed of light of 299,792.458 km/sec. From the above three determinations,\na reasonable of GM would be:\nGMe+a = 398,600.5 km3/sec2\nUsing the results of Verniani (1966) for the mass of the atmosphere gives\nGM, = .34 km3/sec2\nand thus,\nGMe = 398,600.16 km3/sec 2\nStrange and Richardson (1972) obtained as an estimate of mean equatorial\ngravity\nYe = 978.033 gals\nUsing the above values of GM and Ye with the approach described in Strange\ne\nand Richardson (1972), gives a semimajor axis of 6378.133 kms.\nBased on the information given above, it would seem that the present best\nestimate for the semimajor axis, ae, of the best fitting ellipsoid is\nae = 6378.133 +.003 kms\nAs a practical matter, it seems probable that the semimajor axis of the\nreference ellipsoid to which the 1983 NAD will be referenced will be rounded\nto either 6378.135 kms or 6378.1 130 kms. Several factors argue for 6378.135 kms\nas the best value for reference ellipsoid semimajor axis. For example, posi-\ntions as defined by the Global Positioning System (GPS) which can be expected","221\nto be one of the primary positioning systems of the future will\nbe value for the semimajor axis of the ellipsoid to which its positions use this\nreferenced. In any case, it seems clear that the value of 6378.140 will kms\nrecommended at the 1975 International Association of Geodesy meeting in\nGrenoble, France, is too large.\nTwo components must be considered - rotation axis orientation and longitude\norigin - in defining a coordinate system. With respect to rotation axis\norientation, the Doppler positions seem referenced to the CIO pole with satis-\nbetween factory accuracy. Mueller (1974) and Anderle (1975) show that the difference\n0.1 to 0.2 the Doppler and optical satellite pole positions is generally in the\nrange. Also, Anderle (1976) has demonstrated that the\nmean tions Doppler derived pole positions and yearly mean ILS and IPMS pole yearly\nduring the years 1965 to 1975 do not deviate by more than 0.05. posi- Also,\nby Strange, et. al. (1975) have found that spin axis orientation, as defined\n0.05. VLBI determinations, differs from Doppler spin axis orientation by\nto Until more definitive information is available, it seems only\nwill assume that the Doppler pole and the CIO pole are coincident. acceptable An\nof be made to test this hypothesis during the next two years by comparisons attempt\nthe gravimetric and astro-Doppler deflections at the Doppler stations. Given\nprobable standard deviations of the quantities involved, it should be\nthe possible to define the relation between the Doppler and CIO pole to about\n+0.1 level.\nThe that Doppler the system has no intrensic longitude origin. It is generally stated\ndefined origin of the terrestrial system should be the zero meridian as\nby the BIH (see for example the results of Colloquium No. 26 On\nReference Coordinate Systems for Earth Dynamics held in Torum in 1974).\nIt is generally presumed that because optical satellite observations\nBIH to time and stars referred to the FK4 system, they should be referenced use\nthe BIH zero meridian. Thus, rotating Doppler results at co-located\nstations to bring optical and Doppler longitudes into agreement should\nproperly place the Doppler zero meridian. A problem with this approach\nlies in the fact that the optical satellite solutions do not agree with\none another as to the location of the zero meridian. Moreover, different\ninvestigators do not even agree on the amount by which two optical satellite\nsolutions differ from one another.\nSome degree of consistency as to differences in location of longitude origin\ncan be obtained by intercomparing data from the SAO Standard Earth III\nsolution (Gaposhkin, et. al., 1974), the JPL DSN position solution, a determina-\ntion of McDonald lunar laser ranging longitude (Williams,\n) and the NGS\npositions presented in Table 1. Strange, et. al. (1975) found the longitude\nrotation between the Goldstone DSN results and the Doppler results to be 0.864\nwhile the longitude rotation between the McDonald Observatory and Doppler\nresults was 0.792. This gives a mean longitude origin difference of 0.83\nbetween Doppler positions and positions whose longitude origin is defined\nby the intersection of the equator and the ecliptic. Duncombe, et. al. (1974)\nhave indicated that this longitude origin differed by about 0.85 from the FK4\nlongitude origin in 1970. This would imply that the Doppler positions did\nnot need rotating.","222\nComparison of longitude origin between SAO results and JPL results indicate\nthat SAO results would require only about 0.71 rotation to agree with the\nDSN results. Given that the SAO observations were obtained primarily in\nthe early and mid 1960's, this is about the predicted difference predicted\nby Duncombe, et. al. (1974). A correlary of these two comparisons with DSN\nand lunar laser results is that SAO optical and NGS Doppler results are\nessentially in agreement with regard to longitude origin. This is in satis-\nfactory agreement with the rotation of 0.26 derived by the Defense Mapping\nAgency to bring astro-Doppler deflections in agreement with gravimetric\ndeflections (Seppelin, 1974). The type of comparison described by Seppelin\n(1974) assumes that the astronomic positions used are referenced to the BIH\nzero meridian. This may or may not be the case. A study is now underway\nat NGS to assure that all astronomic longitudes utilized by NGS are properly\nreferenced to a common longitude origin. Whether or not the longitudes will\nbe referenced to the zero meridian (mean observatory) of the BIH is difficult\nto say. Using BIH time and FK4 stars, longitude determinations carried out\nby NGS give nearly the same longitude for the U. S. Naval Observatory PZT\nat Washington as derived by the observatory. However, this differs from the\nlongitude assigned to the USNO PZT by BIH. The longitude of the Richmond,\nFlorida PZT obtained by NGS also differs from the BIH value. Because of the\nfact that the USNO results obtained using a PZT and the NGS results using\na T-4 are in very close agreement, it seems reasonably clear that the pub-\nlished BIH longitudes for its stations are not the longitudes which will\nbe obtained by observation at the stations. This makes it difficult to say\nhow well one is referenced to the BIH zero meridian.\nFor practical purposes, it is satisfactory that gravimetric deflections and\nastrogeodetic deflections agree and that an observer using the FK4 star\nsystem and BIH time can repeat given astronomic positions. Therefore, it\nis planned to fix the geodetic longitude origin of the 1983 NAD by computing\ngravimetric deflections at about 50 Doppler stations and rotating the Doppler\npositions to make the mean difference between gravimetric and astro-Doppler\ndeflections be zero.","223\nReferences\nAnderle, R. J., 1976, Comparison of Doppler and Optical Pole Position Over\nTwelve Years, NSWS/DL TR-3464, Naval Surface Weapons Center, Dahlgren,\nVirginia, 10 pp.\nAnderle, R. J., 1975, Error Model for Geodetic Positions Derived from Doppler\nSatellite Observations, NSWS/DL TR-3368, Naval Surface Weapons Center,\nDahlgren, Virginia.\nAnderle, R. J., 1974, Transformation of Terrestrial Survey Data to Doppler\nSatellite Datum, Jour. Geophy. Res. Vol. 79, No. 35, pp. 5319-5331.\nCarroll, D. G., and Wessells, C. W., 1975, A 1975 Astrogeodetic Geoid for\nthe United States, paper presented, IUGG, International Association\nof Geodesy, XVI General Assembly, Grenoble, France, August, 1975.\nDracup, J. F., 1976, Updating Survey Networks - A Practical Application of\nSatellite Doppler Positioning, paper presented, International Geodetic\nSymposium Satellite Doppler Positioning, Las Cruces, New Mexico,\nOctober, 1976.\nDuncombe, R. L., Seidelmann, P. K., and Van Flandern, T. C., 1974, Celestial\nReference Systems Derivable from Solar System Dynamics, in Colloquium\nNo. 26: On Reference Coordinate Systems for Earth Dynamics, Kolaczek, B.\nand Weiffenbach, G. ed., International Astron. Union, Warsaw, Poland,\npp. 223-234.\nEsposito, P. B., and Ng, A. T., 1975, Experimental Determination and Critical\nReview of the Status of the Geocentric Gravitational Constant (abstract),\nEOS, Trans. AGU, Vol. 56, No. 4, p 236.\nGaposchkin, E. M., 1974, Earth's Gravity Field to the Eighteenth Degree and\nGeocentric Coordinates for 104 Stations from Satellite and Terrestrial\nData, Jour. Geophys. Res., Vol. 79, No. 35, pp. 5377-5411.\nHothem, L. D., 1975, Evaluation of Precision and Error Sources Associated\nwith Doppler Positioning, preprint, paper presented 56th annual meeting\nAGU, Washington, D. C.\nLaChapelle, G., 1976, Physical Geodesy at the Geodetic Survey, paper presented,\nPan American Institute of Geography and History, Symposium on Solid\nEarth Geophysics in the Americas, Ottawa, Canada, September, 1975.\nLeick, A., and van Gelder, B. H. W., 1975, On Similarity Transformations\nand Geodetic Network Distortions Based on Doppler Satellite Observa-\ntions, Report No. 235, Dept. of Geodetic Sciences, The Ohio State\nUniversity, Columbus, Ohio, 145 pp.","224\nMarsh, J. G., and Vincent, S. F., 1974, \"A Detailed Gravimetric Geoid of\nNorth America,\" Unpublished map.\nMeade, B. K., 1976, Errors of Doppler Positions Obtained from Results of\nTranscontinental Traverse Surveys, paper distributed, International\nGeodetic Symposium Satellite Doppler Positioning, Las Cruces, New\nMexico, October, 1976.\nMeade, B. K., 1974, Doppler Data Versus Results from High Precision Traverse,\nThe Canadian Surveyor, Vol. 28, No. 5, pp. 462-466.\nMoose, R. E., and Henriksen, S. W., 1976, Effect of Geoceiver Observations\nUpon The Classical Triangulation Network, NOAA Technical Memorandum\nNOS-66-NGS-2, National Ocean Survey, NOAA, U. S. Dept. of Commerce,\nWashington, D. C., 65 pp.\nMueller, I. I., 1974, Global Satellite Triangulation and Trilateration\nResults, Jour. Geophys. Res., Vol. 79, No. 35, pp. 5333-5348.\nRapp, R. H., and Rummel, R., 1976, Comparison of Doppler Derived Undulations\nwith Gravimetric Undulations Considering the Zero-Order Undulation of\nthe Geoid, paper presented, International Geodetic Symposium Satellite\nDoppler Positioning, Las Cruces, New Mexico, October, 1976.\nSeppelin, T. 0., 1974, The Department of Defense World Geodetic System 1972,\npaper presented, International Symposium on Problems Related to the\nRedefinition of North American Geodetic Networks, Fredericton, Canada,\nMay, 1974.\nSmith, D. E., Lerch, F. J., Marsh, J. G., Wagner, C. A., Kolenkiewicz, R.,\nand Khan, M. A., 1976, Contributions to the National Geodetic Satellite\nProgram by Goddard Space Flight Center, Jour. Geophys . Res., Vol. 81,\nNo. 5, pp. 1006-1026.\nSmith, R. W., Schwarz, C. R., and Googe, W. D., 1976, DOPPLR - A Point\nPositioning Program Using Integrated Doppler Satellite Observations,\nTechnical Report No. DMATC 76-1, Defense Mapping Agency Topographic\nCenter, Washington, D. C., 56 pp.\nStrange, W. E., Hothem, L. D., and White, M. B., 1975, The Satellite Doppler\nStation Network in the United States, paper presented, IUGG, Interna-\ntional Association of Geodesy, XVI General Assembly, Grenoble, France,\nAugust 1975.\nStrange, W. E. and Richardson, J. A., 1972, A New Determination of Ye' ae\nand W Using Surface Gravity Data, preprint, paper presented at\n53rd Annual Meeting, AGU, Washington, D. C.\nVerniani, F., 1966, The Total Mass of the Earth's Atmosphere, Jour. Geophys.\nRes., Vol. 71, No. 2, pp. 385-391.","225\nVincenty, T., 1976, Determination of NAD 1983 Coordinates of Map Corners,\nNOAA Technical Memorandum NOS-NGS-6, National Ocean Survey, NOAA,\nU. S. Department of Commerce, Washington, D. C. , 8 pp.\nWilliams, J. G., 1975, Geodetic Results from Lunar Laser Ranging (abstract),\nEOS, Trans. AGU, Vol. 56, No. 4, p. 236.\n,","1\nFIG.\n+5\nContour Interval: 2.5 meters\n(NAD 1927 - Doppler)","- ------------------\n227\nFIG. 2\n5\n-10\nContour Interval: 2.5 meters\nLATITUDE DIFFERENCE\n(NAD 1927-Doppler)","228","229\nAPPLICATIONS OF DOPPLER SATELLITE SYSTEMS IN\nREMOTE REGIONS IN AND NEAR AUSTRALIA\nD. McLuskey\nThe Royal Australian Survey Corps\nDepartment of Defence\nCanberra Act Australia\nAbstract\nExtensive survey operations have been undertaken in inaccessible terrain\nin developing countries using Geoceivers. A new satellite based datum has\nbeen established in Indonesia. A summary of the operational and computational\ntechniques is given, together with a brief appreciation of the associated\nlogistical overheads. Problems arise when Doppler satellite systems are\nbeing used to provide vertical control.\nIntroduction\nAustralia finds itself in much the same position as many developing\nnations in the aspect of mapping on a national scale. The common problems\nrelate to large inaccessible areas, often sparsely inhabited, limited trained\nmanpower and, most of all, limited funds which can be allocated to a national\nmapping programme. One way of overcoming these problems is the employment\nof the latest technology available to increase per capita productivity and\nto reduce logistical overheads. With the present context this has prompted\nthe acquisition of Doppler satellite positioning systems by both civil and\nmilitary mapping organizations in Australia.\nIn addition, the Australian Government has accepted certain responsibili-\nties under its defence cooperation agreements with the governments of Indonesia\nand Papua New Guinea. A major element of these agreements involve comprehen-\nsive mapping programmes in both countries. Consequently the Royal Australian\nSurvey Corps (RA Svy) is responsible for provision of geodetic and mapping\ncontrol for the area of Australia generally north of 20° South latitude,\nincluding PNG and parts of Indonesia.\nDeployment\nThe Australian Army acquired 6 Geoceiver systems in 1975. Of these, one\nis held permanently at a central workshop in Australia for training and quality\ncontrol purposes. The remaining systems are deployed as a group: four are\nused to occupy stations and the fifth is held at the field base camp as a\nbackup in the event of failure of the operational systems. The systems are\nrepaired at the field base camp. Availability of the order of 98.5% is being\nachieved in this way. The total cost of the Geoceivers, including a compre-\nhensive spare parts inventory, was of the order of half a million dollars.\nWe believe that they have paid for themselves within a year.\nThe US Government, through DMATC, has provided considerable assistance\nthroughout the introduction of the Geoceiver system, including an initial\nloan of two Geoceivers, technical support and advice, maintenance support and","230\ncomprehensive software packages. In addition, precise ephemeris for NAVSATS\nis being provided under terms of intergovernmental agreements at no cost.\nThe Geoceivers are being used almost exclusively for production purposes.\nThey are deployed in two roles:\na. acquisition of mapping control; and\nb. geodetic purposes.\nThe differentiation between the two lies in the number of passes tracked on\neach station. Geodetic stations have a minimum of 25 well balanced good\npasses and mapping control stations have a minimum of 12 good passes.\nComputations\nAll computations are based on point positioning technique using precise\nephemeris. Twenty-five pass stations exhibit standard errors of the order\nof 0.3 m in each coordinate and in 12 pass stations this figure increases to\nabout 0.7 m in each coordinate. Stations with few passes often exhibit non-\nsymmetrical pass geometry and in these cases correlations as high as 0.6\nappear between pairs of coordinates. However, their standard is still well\nwithin the error budget assigned for mapping at scales 1:50,000 and smaller.\nNo effects are evident which are attributable to the paucity of tracking\nstations in the Southern Hemisphere.\nPreliminary examinations were made to determine the possibility of\nincreasing production by employing translocation techniques, however these\nwere discontinued. The reason for this was that stations are completely\nself supporting: when precise ephemeris is available for two satellites,\nas at present, a 25 pass solution requires four days on station, and\noperator fatigue involved in frequent movement between stations imposes a\nlower limit on the duration of station occupation.\nOperations in Indonesia\nThe Indonesian Government has decided to adopt a satellite based datum\nfor mapping and geodetic purposes. The current origin for this datum is\nthe station PADANG BP A 1884 in Sumatra, however the origin may be changed\nto a more central location in the future. The adopted ellipsoid of reference\nhas the dimensions of the GRS-67 figure. At the origin the geodetic coordinates\nin the national system are defined as being identical to those computed in the\nNWL-9D system and the axes of the two systems are defined as being parallel.\nConsequently, transformations between systems require translations only.\nScale in the national system is defined by the Doppler satellite network.\nThis definition was tested using the Sumatra geodetic triangulation\nnetwork observed in 1883-1916. The network was readjusted to a framework\nof Doppler stations: residuals on angles average 0.39 arc sec with a maxi-\nmum of 2.39 arc sec. Average azimuth change was 1.21 arc sec with a maximum\nof 1.62 arc sec. Geoceiver stations established for this purpose are shown\nin Fig. 1.","231\nThe simple method of definition enables the new datum to be extended\nthroughout the Indonesian island arc with ease. A comprehensive programme in\nIrian Jaya involving about 130 stations will be computed on the new datum.\n(It is expected that this operation will be completed within two field\nseasons each of four months: all stations are geodetic). .\nOperations in Papua New Guinea\nDoppler satellite systems have been found to be ideal for the coordina-\ntion of stations on islands where intervisibility is not possible. Within\nthe last year about 80 island stations have been occupied by Geoceivers in\nthe Bismarck and Louisade archipelagos to provide mapping control and to\nassist in determination of inter island distances to establish sovereignty.\nIn addition a number of existing geodetic stations were occupied to\nexamine the local geodetic net in PNG. The net consists essentially of\ntraverse, connected to the Australian Geodetic Datum (AGD) by Hiran distance\nobservations from a number of Australian stations. Preliminary examinations\nat five stations indicated that serious distortions exist within the net\nand that the AGD had not been effectively tranferred by the Hiran net. The\ninvestigation has been extended by occupying an additional five geodetic\nstations in PNG and four Hiran stations in Australia.\nAnalysis of this total net will enable realistic recommendations to be\nmade concerning the future of the PNG geodetic net. It appears at present\nthat one of the three possible courses which follow will have to be chosen:\na. The PNG net be recomputed on the AGD using NWL-9D to AGD\ntransformation parameters currently being determined in\nAustralia by the Division of National Mapping.\nb. Adopt a satellite based system and recompute the total net on\nthis system.\nAdopt a local internal system defined by conventional techni-\nC.\nques.\nThe final decision will probably have to be made by the PNG government\nwithin the next two years.\nUse of Doppler Satellite Stations for Vertical Control\nIn inaccessible areas the provision of vertical control for mapping is\nas much a problem as horizontal control. The problem has been partly\nalleviated in RA Svy by use of an airborne laser terrain profiler. Because\nthe profiler uses an isobaric surface as datum, each profile must be con-\ntrolled, either individually or as part of a network. Geoceivers are being\nused to provide vertical control for the profiles. For this purpose,\ngeoidal undulation must be known. No problem exists in Australia where the\ngeoid is defined at about the 1 metre level. The geoid is known in PNG to\nabout 5 metre accuracy; this is at about the acceptable level for vertical\ncontrol for mapping at scales 1:50,000 and smaller. In Irian Jaya the only","232\ngeoid available has been determined by satellite methods; it is intended that\nthis be used in lieu of any other data until a full gravimetric survey is\ncompleted. One advantage of Doppler satellite systems is that they enable\ngeodetic height to be determined directly, consequently if the height above\nmean sea level is known, then geoidal undulation can be determined. This is\nbeing done in Irian Jaya at all coastal stations in conjunction with tide\ngauges. In addition, the PNG/Irian Jaya border was fixed by precise astro-\nnomical methods: it is hoped that all of the border stations can be re-\noccupied with Geoceivers to enable a profile to be determined from deflections\nof the vertical. Consequently complete peripheral control for the geoid will\nbe available in the region. It is not known at this point what the eventual\naccuracy of the controlled geoid will be, but it is expected to enable mapping\naccuracy standards to be attained.\nLogistics\nThe logistic support needed for a four month operation to maintain and\nmove four Geoceivers on station in a developing country such as Indonesia\nand PNG is considerable. A Geoceiver station requires a team of two or\nthree operators, tentage, power, food, etc, whose all up weight is about\n800 to 1000 kg. For transportation we would deploy two medium lift heli-\ncopters (UH-1B), one medium left transport aircraft (Caribou), one light\nfixed wing STOL aircraft and perhaps some boats for coastal work.\nPersonnel support runs to about 100 persons, including: surveyors,\ntechnicians in support of aircraft, vehicles and electronic equipment, radio\noperators, cooks, drivers, storemen and so on. The total lift to insert the\nunit runs to about 150 tonnes plus about 3.5 tonnes per week of food and\nstores to maintain it. The total fuel bill is about 2 millian litres for\na four month operation. For this cost, productivity averages 1.5 days per\nstation.\nConclusion\nIt has been intended in this paper to describe the way in which Doppler\nsatellite systems are used by RA Svy. Doppler satellite methods are per-\nmitting geodetic and mapping control to be established in areas where\nconventional survey techniques cannot be used and, in particular, the cost\nof establishing this control is being kept comparatively low because of\nreduced overheads in logistics and manpower. With the assurances which\nhave been given by the U.S. Government concerning availability of precise\nephemeris, it appears that no practical advantage can be gained by employing\ntranslocation or short arc techniques over point positioning.","233\nBANDA ATIEH\nst\nWESTERN HILL\nHALA L SING\nP118\n104°\n4°N\n50\nAP62\nPulau PISANG\n8\n96°\n0°\nas\nPADANG\n(1884)BP A\nBANARA\n4°S\n96°\nP71\nB\nSCALE: 1: 7,500,000\nFIG. 1 Geoceiver Operations by RA SVY\nin Sumatera and Malaysia, 1974","------------\nESTABLISHED STATIONS\nPROPOPOSED STATIONS\ns\no\nFIG. 2 Geoceiver Stations RA SVY, 1974-76\n00\nB\nSCALE: APPROX. 1:22,000,000\n03","235\nPOSITION PAPER SHOWING COMPARISONS\nWITH THE AUSTRALIAN GEODETIC SURVEY\nAS AT SEPTEMBER 1976\nJohn McK.Luck\nDivision of National Mapping\nAustralia\nIn 1966 the Australian Geodetic Survey had reached the stage at which a\nnational adjustment was undertaken and the resultant coordinates were adopted\nby the National Mapping Council for topographic mapping purposes. Since then,\nthese coordinates have been widely adopted for many other purposes and have\nbeen accorded legal status under various Federal and State Acts of Parliament.\nThe survey was based almost entirely on electronically measured distances\nand included a considerable number of Laplace azimuths, but in order that an\nearly survey framework might be available for practical use, the 1966 adjust-\nment ignored the geoid-spheroid separation and used trigonometrically deter-\nmined elevations for reduction to sea level.\nBy 1971 an Australian Levelling Survey and a very dense astro geodetic\nsurvey were completed and these in conjunction with a nation wide gravimetric\nsurvey, provided the basic data from which geoid-spheroid contours were\ndetermined.\nDuring the period 1975-76 doppler satellite observations have been made\nat 96 major junction points of the original survey for the purpose of testing\nthe accuracy of that survey and for the purpose of providing a ready means for\nthe conversion of future doppler satellite observations into Australian Geodetic\nSurvey coordinates.\nThe positions derived from the observations have been calculated in terms\nof precise ephemeris data supplied to the Royal Australian Army Survey Corps\nby the U.S. Defense Mapping Agency.\nThe observations were carried out by personnel of the Division of National\nMapping, the Royal Australian Survey Corps and the staff of the Surveyors\nGeneral of Western Australia, South Australia, Queensland and Tasmania. The\noverall organization of the operation and the comparison of data were under-\ntaken by the Division of National Mapping.\nTo date 54 positions have been computed and a best fit derived between\nthe doppler data and the AGD. The following transformation factors are applied\nto NWL 9D at this point of time:\nScale\nNWL 9D reduced by 1ppm\nRotation\nNWL 9D East longitudes increased numerically by\n0. .53\" and South latitudes decreased numerically\nby 0.05\".","236\nCoordinates\n- X coordinates decreased numerically by 120m\n- Y coordinates increased numerically by 50m\n- Z coordinates increased numerically by 151m\nThe differences between the latitudes and longitudes derived from NWL 9D\ncoordinates and those of the AGD together with respective differences in geoid/\nspheroid separations are listed in Annex A and illustrated in Annex B.\nThe average differences without regard to sign are:\ndo 0.05\"\n(1.5m)\nd 0.06\"\n(1.5m)\nd\n(N+H)\n1.3m\nAnnex A\nSTATION COORDINATES\nAGD - Converted\nNWL9D\nS LATITUDE\nE LONGITUDE\nN + H\n40\"\nAX\"\n(N + H) m\no\no\nm\n20\n21\n139\n12\n525\n-0.06\n+0.09\n+0.56\n28\n02\n120\n32\n571\n+0.02\n+0.08\n+0.54\n43\n25\n146\n10\n31\n+0.05\n+0.09\n+2.27\n37\n51\n144\n58\n42\n+0,01\n+0.05\n-0.20\n18\n26\n127\n25\n466\n-0.07\n+0.06\n+0.03\n33\n06\n147\n18\n245\n+0.01\n-0.03\n-3.80\n30\n50\n121\n06\n567\n+0.09\n-0.15\n-0.07\n40\n52\n144\n42\n188\n+0.02\n-0.02\n+3.26\n21\n47\n131\n52\n623\n-0.08\n+0.04\n+1.70\n25\n07\n113\n44\n32\n-0.06\n+0.16\n+2.88\n31\n50\n115\n58\n43\n-0.13\n-0.10\n-2.64\n40\n45\n147\n58\n68\n+0.08\n+0.04\n-1.05\n34\n15\n115\n01\n64\n-0.11\n-0.10\n-1.54\n30\n19\n149\n34\n222\n+0.04\n+0.03\n-1.79\n31\n35\n117\n51\n346\n-0.05\n-0.09\n-0.18\n29\n59\n146\n34\n173\n-0.06\n-0.03\n-1.41","237\nAnnex A (Cont'd)\nS LATITUDE\nE LONGITUDE\nN+H\nAO\nAl\n1(N+H)m\n1\n1\no\no\nm\n37\n28\n141\n55\n484\n+0.08\n+0.02\n-0.88\n12\n27\n130\n49\n30\n-0.08\n+0.12\n-0.23\n31\n06\n141\n44\n294\n0.02\n-0.06\n-0.17\n28\n49\n121\n18\n470\n+0.05\n-0.09\n+1.00\n26\n38\n145\n08\n339\n-0.03\n+0.03\n+0.02\n38\n14\n146\n56\n235\n+0.02\n+0.08\n+0.76\n26\n32\n142\n23\n210\n-0.05\n-0.08\n+0.44\n25\n57\n133\n13\n571\n+0.06\n-0.06\n+1.05\n35\n15\n142\n54\n108\n+0.07\n0.00\n+1.80\n33\n06\n138\n35\n760\n+0.03\n-0.03\n-1.22\n23\n56\n151\n14\n236\n+0.06\n+0.04\n-2.76\n32\n27\n123\n48\n179\n+0.02\n-0.19\n+1.99\n31\n34\n132\n05\n89\n+0.05\n-0.06\n-3.98\n30\n38\n130\n21\n128\n+0.09\n-0.11\n+0.03\n34\n12\n142\n01\n78\n+0.10\n+0.02\n+0.72\n14\n26\n132\n20\n183\n-0.09\n+0.09\n+0.03\n21\n44\n115\n41\n127\n+0.03\n+0.11\n+1.14\n15\n36\n128\n17\n64\n-0.17\n+0.05\n-3.85\n20\n30\n130\n14\n401\n-0.05\n+0.08\n+1.53\n18\n09\n124\n18\n107\n-0.08\n+0.06\n+1.06\n14\n51\n135\n04\n107\n-0.10\n+0.02\n+2.59\n32\n41\n151\n47\n189\n+0.05\n+0.09\n-2.15\n19\n37\n134\n11\n449\n-0.04\n+0.01\n+1.01\n34\n41\n138\n39\n42\n+0.09\n-0.06\n+0.01\n22\n11\n133\n39\n689\n-0.04\n+0.02\n-0.36\n29\n14\n115\n12\n220\n-0.08\n-0.07\n-0.05\n35\n19\n149\n00\n789\n0.00\n+0.03\n+2.31\n36\n05\n147\n06\n662\n+0.07\n+0.08\n+0.58\n23\n09\n128\n54\n553\n-0.02\n+0.01\n+3.02\n35\n05\n117\n37\n291\n+0.02\n-0.04\n+0.76","238\nAnnex A (Cont'd)\nS LATITUDE\nE LONGITUDE\nN + H\nDO\nAl\nA (N+H) m\n1\no\no\nm\n19\n16\n146\n43\n20\n+0.01\n+0.01\n-0.09\n28\n02\n117\n49\n558\n-0.04\n+0.03\n-2.42\n30\n32\n133\n10\n241\n+0.01\n-0.07\n-0.43\n33\n53\n121\n53\n103\n-0.09\n+0.02\n+1.46\n32\n16\n121\n47\n498\n-0.01\n-0.07\n+0.20\n31\n24\n136\n53\n147\n+0.04\n-0.15\n-0.67\n32\n59\n135\n33\n267\n+0.04\n+0.01\n-3.52\n27\n03\n151\n44\n761\n+0.01\n+0.06\n+0.52\nAverage of 54 stations without\nregard to sign\n0.05\n0.06\n1.31","","240","241\nWORKSHOP ON RECEIVER HARDWARE,\nFORMATTING AND HANDLING DATA\nReport of the Chairman\nP. E. P. White\nThe Johns Hopkins University-\nApplied Physics Laboratory\nLaurel, Maryland 20810\nIn the Workshop's first session on Tuesday afternoon, four papers were\npresented by their authors. The entire symposium was in attendance. Three\npapers dealt with receiver hardware; the fourth with documentation of\nlocation of antenna sites. In the Workshop's second session, Thursday,\nthe attendance comprised only those people whose interest in this Workshop\nwas greater than their interest in the other Workshops which proceeded\nconcurrently. Two more papers were presented on Thursday, but most of the\nfive hours available were used for informal discussion and comment by\nattendees, on topics of concern to them individually.\nBy its title, this Workshop invited attention from everyone interested\nin the mechanics of data acquisition. It is a clear principle that obser-\nvational data must be obtained before any point can be positioned or any\nthesis tested. Too, the quality of the observational data limits finally\nthe quality of the position fix, and the cost of the data limits the quantity\nof the work that can be done. Consequently, the appeal of the Workshop was\nbroad. More than one quarter of the attendees at the Tuesday symposium\nsigned their intention of participating in the Workshop's Thursday session.\nThese included representatives of government from 15 foreign countries,\nand 8 USA-based commercial enterprises.\nThe four formal papers (Tuesday) are now available in full in the\npresent document. The reader can find the message of each in its author's\nown words. It is unfortunately not possible here to do equal justice to\nthe informal contributions of the participants in the Thursday session.\nBefore the symposium began, and again during its Tuesday and Wednesday\ngeneral sessions, people were invited to name subjects suitable for discussion\non Thursday. The list that resulted is seen here. In the event, not all\nthese subjects received satisfactory treatment, and several were not even\nraised. But a broad perspective obtained and no one subject claimed the\nWorkshop's full attention for over long. Main areas of discussion of that\nday, and some of the thoughts expressed, appear below:\nA. RECEIVER HARDWARE\n1. Time and frequency control: oscillators, time delays, accuracy\n2. Antennas: location of \"effective point\" of data acquisition\n3. Recording medium: punched paper, printed paper, magnetic tape\n(reel-to-reel, cassette), disk, none\n4.\nData evaluation in field: real-time navigation, time points, return\ndata for central control","242\n5. Design constraints for equipment: size, weight, power source,\nenvironmental\n6. Automaticity: programmed acquisition, satellite identification,\nduration of unattended periods\n7. Repair: field/depot, module/component, diagnostic method\n8. Additional data products: single frequency doppler, time points,\nionospheric error, signal strength\nB. DATA FORMAT\n1. Time-fixed/cycle-count-fixed\n2. Epoch statements: standardization, completeness, accuracy\n3. Headers and data, flags: standardization, frequency of appearance,\nplacement, redundancy, content\n4. Satellite numbers, site numbers: what system, how controlled\nC. DATA HANDLING\n1. Station site numbering: system, catalogs, accessibility\n2. Communications: postal, electrical-message, data message\n3. Data archives: importance, where located, format, accessibility of\ndata\n4. Satellite numbering: system, catalogs, availability\n5. Knowledge of satellite status: oscillator frequency, signals off,\nsignal strength\nOscillators\nRubidium oscillators were favorably described as candidates for the\nfunction of frequency reference source in all types of doppler receivers.\nLow frequency drift over the critical pass time interval (1000 seconds), and\nshort warm up time, were cited as advantages. In field use, it was said,\nrubidiums have made it possible to get better positioning accuracy from a\ngiven number of passes observed; alternatively, to achieve a specified\naccuracy using fewer passes than before.\nClock Time Control\nA general feeling that TRANET stations are keeping accurate time (< 50\nmicroseconds error) was challenged by the implications of a paper presented\nto the Workshop by Dr. Paul Paquet. In two of the three TRANET stations he\nhad studied, clock errors greater than 100 microseconds were implied by the\nresults of his data processing. TRANET engineers present at the meeting\nfound such errors hard to accept in view of the apparently trustworthy\noperation of the \"beep word\" (\"time burst\") detector circuitry now in use\nthroughout TRANET. However, no fault was found with the Paquet method\n(Usandivaras/Paquet) for deducing station clock error.\nIt was suggested that the TRANET doctrine for measurement of delay\n(fiducial time point delay) may need review. Tracking filter type receivers\nmay need special procedures to obtain accurate results. The delay in such\nreceivers is believed to be quite sensitive to variations in amplitude and\nfrequency of the received signal.","243\nAntennas\nMeasurements of the apparent electrical center of some types of antennas\nwere reported to the Workshop by Mr. Franz Blaha. These supported the results\nobtained in 1972 at PSL/NMSU, showing the location of the apparent center to\ndepend upon the antenna design, notably any ground plane used, and upon the\ngeometry of the satellite pass. The variability in the location was found to\namount to several centimeters in some cases.\nMr. Robert Hill stated that some users of TRANET data would be affected\nby an error or uncertainty in antenna \"center\" of as little as 5 centimeters.\nThe cause of the anomalies in apparant center was attributed by some\nengineers at the Workshop to multipath reflections. It was suggested that\nthese reflections could be minimized by the proper design of ground plane\nstructures.\nIt was agreed that more work is needed on this problem. First a study\nof antennas now in TRANET service should aim to provide data users with\nquantitative information about the existing conditions. Then if these\nconditions are judged to be undesirable, improved antenna design specifications\nshould be developed.\nAntenna gain characteristics were discussed also. Crossed dipoles\n(PSL/NMSU) and shaped-edge ground planes (Uppsala University) were advocated\nas designs useful in reducing overhead nulls and in minimizing secondary\nlobes, respectively.\nMedia for Data Recording\nPunched paper tape received support as a medium for initial (field)\nrecording of doppler data. In its favor were cited:\n- tolerance of environmental conditions\n- ability to be comprehended by human eye\n- compatability with many makes of tape handlers and readers\n- ease of editing and of annotation\n- availability of facilities permitting electrical transmission\n(teletype) and also translation to other media (magnetic tape,\ndisk, printed page),\nHowever, the comparatively great bulk of paper tape and its clumsiness\nled some equipment designers to advocate other media. The distinction was\nmade between data recorded for possible consumption by more than one\nprocessing center, exemplified by TRANET, and data intended for sole use of\nthe owner of the receiving equipment. In the latter case, a recording\nmedium need only be adapted to a single objective. A magnetic tape cassette\nmight be the best way of meeting certain users' requirements. The reliability\nof cassettes has been demonstrated by extensive use in the field, it was\nsaid. A cassette recorded on one type of equipment may be incapable of\nplayback on another type, but this problem need not arise when the data\nacquisition and data reduction operations are tightly contained within the\nsame agency.","244\nData Formats\nThe proliferation of types of format for both doppler data and data\nidentification statements (\"headers\") was deplored by Mrs. Caroline Leroy.\nShe asked that the designers of new receiving equipment should shape their\ndata product to fit one of the existing, widely-used patterns. In some cases\ndata of potential significance have had to be discarded because certain\nessential information could not be found in the record. Standardized formats\ncould avoid this, and serve the needs of all likely users.\nThese views were endorsed by Mr. Leo Lopez. He said that even when the\ndata content is complete, translation costs for non-standard format data\ncan sometimes be so high as to preclude use of these data.\nThe new TRANET equipment has been designed by PSL to have programmable\noutput format. Commercially built portables, however, are unlikely to\nprovide such flexibility. Discussion indicated that people at the Workshop\nsaw the standardization of format, like the standardization of a recording\nmedium, to be a possibly desirable but probably unattainable goal.\nOther Topics\nThe satisfactory operation of a receiver in the field, notably a receiver\nin portable service, can be made known to the operator by a number of signs\nand in particular by a visually intelligible data product such as punched\npaper tape. Better, as pointed out by Mr. Thomas Stansell, Mr. Paul Rodgers\nand others, some level of built in data reduction capability can provide\nstrong reassurance. The on-site calculation of effective oscillator\nfrequency, and actual position fix computation, were given as examples.\nAn advantage of programmable automatic control of receiving equipment\nwas stated to be its ability to reduce the accumulation of data from\nredundant satellite passes and thus the effort of culling the data to find\nthe passes actually required. Dr. Luigi Ciraolo and others made this\nobservation.\nA standardized site location report was advocated by Mr. John Love for\nDMA. As with the questions of standardized recording medium and data format,\nthe concept of standardized site description seemed to have few detractors,\nbut its supporters were unable to show how standardization would be brought\nabout.","245\nA PORTABLE GEODETIC POSITIONING SYSTEM\nWITH REAL-TIME COMPUTATION\nWalter J. Piurek, Manager, Operations\nJames E. Johnson, Systems Engineer\nJohn Vivian, Engineering Supervisor\nSatellite Positioning Corporation\nHouston, Texas 77074\nIntroduction\nEver since satellite positioning techniques were proven to be useful on\nland as well as at sea, positioning companies throughout the world have\nconfigured all sorts of satellite receivers, computers, recorders, and\nprinters in an effort to come up with a satellite positioning system that\ncould be taken to the field and successfully do the job for which it was\nintended. I am sure that any one who has been there and seen it will smile\nwhen he remembers an ITT receiver, a PDP 8 computer and a Teletype operating\nin the wilds of some jungle with a Christmas tree antenna perched on a\nnearby tree and in the background a chugging generator that was synchronized\nto the operator's heart beat.\nYes, we can smile now and say \"We've come a long way since then.\" But\nhave we? How many protable satellite positioning systems can offer machine\nreadable data recording; how many have a hard copy print out; how many can\ncompute a fix in the field; and how many can do a recompute in the field?\nFinally, how many have all the above features? The old ITT system did. You\ncan believe it from a positioning company whose name is the game; all those\nfeatures are wanted and required in the field. The following paragraphs\nwill attempt to point out why. There will also be a dissertation on some\nadditional requirements that Satellite Positioning Corporation (SPC) has\ndiscovered are necessary in a Portable Geodetic Positioning System With\nReal-Time Fix Computation.\nGeodetic Positioning in the Field\nThe operations problems with geodetic positioning in the field generally\ndeal with transportation, power and equipment reliability. Equipment\nfailure can be attributed to damage in shipment, unstable power and environ-\nmental extremes. Failures in the field will never be eliminated but their\neffects can be minimized if the equipment is properly configured and has\nsufficient back-up modes of operation.\nSatellite Receiver\nThe heart of a satellite positioning system is, of course, the satellite\nreceiver. Fortunately experience has shown that it is usually one of the\nmost reliable components of the system; however, if it does fail, it must\nbe field repairable. This requires that it be of modular construction and\naccompanied with a comprehensive set of replacement modules or, if the\nreceiver is sufficiently small and light, the entire receiver should be\nspared.","246\nComputer\nOnce establishing a reliable receiver configuration, serious considera-\ntion must be given to the purpose of a field positioning assignment. Basically\nthe purpose is to establish the position of a remote site. Because of the\ncost of mobilizing, logistics and equipment, satellite positioning require-\nments are leaning more and more towards real-time fix computations. In short,\nthe position of the site must be known before leaving. Returning home for\npost mission fix computations and finding out that the satellite data brought\nback is bad, or destroyed or even lost is not a pleasant surprise.\nReal-time fix computations require a computer. Historically one of the\nmost unreliable components of a portable positioning system has been the\ncomputer. Computer failures can be attributed mainly to bad power, extremely\nhigh temperatures and damage in shipment. Bad or unstable power is usually\nsupplied by a portable gasoline or diesel generator which although is quite\ngood, because of its size, it cannot take the continuous duty required.\nConsidering the power problem in the field, the most practical solution\nis expendable batteries, batteries that can be purchased locally and\nabandoned when the job is completed. There really is no choice of battery\nfor field operations. It must be universally and readily obtainable. It\nmust be the common 12-volt car battery.\nIt is common knowledge that 12-volt computers are not exactly an off-\nthe-shelf item, and if they were, they probably wouldn't be compatible with\nexisting software. There is, however, two very practical ways of getting\na 12-volt, software compatible computer. First, convert an existing com-\npatible minicomputer to operate on 12 volts and second, build a computer\nusing microprocessor techniques. Both methods have their advantages. A\nfull minicomputer can be programmed in the field to perform a variety of\nother functions besides making simple satellite fix computations, these\ninclude coordinate transformations, datum shifts, and translocation calcu-\nlations.\nA microcomputer on the other hand is more singular in its purpose due\nto its program being stored in a Read Only Memory (ROM); however, it is\ndefinitely smaller, lighter and consumes less power. The microcomputer,\nbecause of its size and weight, is less susceptible to transportation\ndamage and its low power consumption make it more immune to high ambient\ntemperatures. It is in fact the perfect mate for the minicomputer as the\nremote computing element of a translocation pair.\nTransportation damage to a minicomputer can be minimized by the addition\nof various braces and brackets to the computer chassis at vulnerable points.\nUnfortunately, locating the vulnerable points ofttimes occurs in the field\nafter the damage has been done. But after several damaging experiences all\nthe weak points can be found and the minicomputer can be ruggedized to with-\nstand most shipping shocks and vibrations. In fact, ruggedizing a mini-\ncomputer can be done very economically once the dues have been paid through\nfield experience.","247\nTemperature, on the other hand, is a different problem for the\nminicomputer. It still is a power user and does get hot and is very\nsusceptible to high ambient temperatures. But here again experience shows\nthat only turning the computer on when it's needed, decreases power\nconsumption considerably and allows the computer to stay cooler, making it\nmore reliable in high ambient temperatures. Bear in mind that powering the\ncomputer up and down requires special software especially when accumulating\nsufficient data for a simultaneous 3-D fix calculation.\nBoth the mini and microcomputer should be of modular construction to\nfacilitate field repairs and both should be accompanied with a comprehensive\nset of spare modules.\nData Recording\nWhat happens when the computer (s) fails beyond field repair capabilities?\nThe only alternative is to record the satellite data reliably and accurately\nand post compute the site fix when a working computer is available. The key\nto recording satellite data reliably and accurately is to have the capability\nof not only to store the data on some machine readable device but also have\nthe capability to determine that the stored data is correct before the site\nis left.\nRecalling the old ITT system, the machine readable storage medium was\npunched paper tape and the punched data could be verified with the Teletype.\nWhen that capability was lost, the ability to reliably bring back data from\nthe field was seriously hampered. The solution of course is to reinstitute\na similar technique with modern-day technology. The industry accepted method\nof recording machine readable data in the field is magnetic tape. There are\npros and cons as to which type should be used (cassette, 3-M cartridge, link\ntape, 9-track). Again, experience has shown that any of the first three\nmentioned can be used provided that they are packaged properly and that they\ncan be powered from a 12-volt battery.\nTo verify the tapes in the field a printer must be supplied which is\ncapable of directly reading the tape without the use of any other component\nof the system. The process of verification produces a hard copy which is\nin effect a redundant record that can be used to recompute in the event the\ntapes get damaged or lost. The printer should also have the capability of\nrecording data as the primary recording device in case the mag tape unit fails.\nConclusions\nSatellite Positioning Corporation through its field operation experience\nhas developed A Portable Geodetic Positioning System With Real-Time Fix\nComputation which can reliably perform its functions in remote areas of\nthe world in hostile environments. That system is configured as two portable\npositioning systems, one employing a minicomputer and one employing a micro-\ncomputer. Each system can be totally powered from a locally obtainable 12-\nvolt battery. Both are comprehensively spared and both offer operating\nmodes with sufficient flexibility to reliably and accurately record satellite\nand fix data on mag tape backed up with a hard copy printout. Both are","248\ncomprised of components all of which may or may not be sent to the field\ndepending on the degree of complexity of the job which may vary from a\nsimple 2-D fix to a series of full real-time translocation assignments\nextending survey control points.\nThe development of these systems evolved from the experiences gained\nfrom hundreds of positioning jobs performed by SPC throughout the world.\nItemizing these conclusions:\n1. It is now possible to conduct geodetic positioning with real-time fix\ncalculations without the need of a cumbersome gasoline or diesel generator.\n2. Most system component failures can be repaired through modular replacement\ntechniques.\n3. Irrepairable failure in most cases will still allow raw data to be\nreliably recorded for post fix computations.\n4. Both a minicomputer system and a microcomputer system can operate as a\nmatched translocation pair.\n5. The minicomputer system because of its flexibility also allows for in\nfield datum shifts and coordinate transformation calculations.\n6. Power for the systems is easily obtained locally in the form of expendable\n12-volt car batteries.","249\nDOPPLER SURVEY EQUIPMENT:\nBACKGROUND, REQUIREMENTS, AND TRENDS\nThomas A. Stansell, Jr.\nMagnovox Government and Industrial Electronics Company\nAdvanced Products Division\n2829 Maricopa Street\nTorrance, California 90503\nAbstract\nThe earliest satellite Doppler tracking equipment was used by Guier and Weiffenbach\nat the Johns Hopkins Applied Physics Laboratory in late 1967 to monitor the first\nRussian Sputnik. Development of Transit, the Navy Navigation Satellite System, was\nbased on success in determining the Sputnik orbit from observations by a single earth\nstation. The key ingredients contributing to success of the Transit System have been\nthe concept of dynamic geodesy and the ease with which precise Doppler frequency\nmeasurements can be made.\nIn developing the Transit System, a global network of Doppler tracking stations was\nestablished, employing nearly the same Doppler measurement scheme used by Guier\nand Weiffenbach. Although the concept was simple, implementation required a small\nroom full of equipment. In 1964, this author proposed development of a portable\ngeodetic survey instrument which would record the integral of the Doppler frequency\nover contiguous 30-second intervals. The eventual result was the AN/PRR-14\nGeoceiver, of which 55 have been deployed for land geodetic survey.\nThis paper first traces the evolution of satellite Doppler receiving equipment, with\nparticular emphasis on the Geoceiver. Using the Geoceiver as a starting point, the\npaper then relates the effect on accuracy of specific Doppler receiver design charac-\nteristics. The parameters to be discussed include: oscillator stability, receiver\ntime delay, Doppler count precision, time recovery jitter, and local clock resolution.\nThe final section of this paper describes modern trends in development of geodetic\nsurvey instruments. These trends include simplification of receiver electronics,\nalternative data logging techniques, and use of microcomputers for field data verifi-\ncation and preliminary results.\nThe overall intent of this paper is to give a historic perspective to the development of\ntypical satellite Doppler receiving equipment, to provide a definitive statement of\nreceiver specifications and their impact on measurement precision, and to identify\ntrends in the development of modern equipment for geodetic survey applications.","250\nSurvey by Satellite\nDefinitions\nFigure 1 dramatically illustrates the fundamental concept of survey by satellite. The\nsatellite receiving antenna can be placed at any location with a reasonably unobstructed\nview of the sky, and the absolute latitude, longitude, and altitude of that position can\nle determined accurately. The equipment can be transported by helicopter, jeep,\npack animal, etc., because a land traverse is not required as with conventional sur-\nvey techniques in which distance and angle measurements must be made from one\npoint to the next, regardless of the intervening terrain.\nSatellite data can be acquired for processing in either of two ways. One is illustrated\nby Figure 2 which shows a Magnavox Land Survey System, consisting of the antenna/\npreamplifier unit, the Geoceiver II Satellite Receiver, and a paper-tape recorder.\nWith this equipment, satellite data can be acquired at any remote location, after which\nthe recorded data are returned for computer processing. The second method is\nillustrated by Figure 3, in which the receiver is connected directly to a digital com-\nputer. (A typical shipboard system is shown.) During each satellite pass, the com-\nputer obtains the raw data immediately. After the pass, the new information is\ncombined with all satellite data previously acquired at that location, and a three-\ndimensional position fix result is computed. This mode of operation is frequently\nemployed by survey vessels to determine local coordinates when at dockside. For\ninland surveys, the satellite receiver can be removed from the ship and combined\nwith the portable antenna/preamplifier unit and the tape recorder to form the land\nsurvey system of Figure 2.\nThere are two methods for processing the data. In \"point positioning\", data from a\nsingle receiver is used to obtain the latitude, longitude, and altitude of its antenna.\nThe only datum or reference for this process is the satellite system itself. From 10\nto 50 satellite passes normally are employed when operating in the point positioning\nmode, and Figure 4 gives the average interval between satellite fixes as a function of\nlatitude. (This curve is approximately correct for passes between 15 and 90 degrees\nmaximum elevation, although it was derived for passes between 10 and 70 degrees.)\nThe extreme limits of the curve indicate that 10 passes can be obtained in as little as\n6.3 hours at high latitudes or they could take 15. 8 hours at the equator. Equivalent\ntimes for 50 passes would be 31. hours at high latitudes and 79. 2 hours at the\nequator. Accuracy of the final point positioning result is dependent on the number of\nsatellite passes.\nThe second method of processing is called \"translocation\", in which one survey\nantenna is located with respect to another. The advantage of translocation is that\nrelative position can be established accurately with very few satellite passes.\nFigure 5 is an error budget published recently by the Applied Physics Laboratory,\n(Reference 1). The error caused by instrumentation (the satellite receiver) is quite\nsmall compared with other error sources. Therefore, if two receivers are near each\nother and track the same satellite pass, the fix error at each location will be strongly\ncorrelated. As a result, relative position can be determined with very high accuracy,\neven if the individual fix results have large error. Figure 6 illustrates the principle\nand shows that \"being near each other\" is relative to the distance of satellite travel\nduring the pass. Because satellite travel is about 000 kilometers, two receivers are\nnear enough for translocation even at distances of a few hundred kilometers.","251\nNC.","","-------------------\nPREAMPLIFIER\nANTENNA/\nFIG. 3 Typical Magnavox Dual-Channel Satellite Navigation Equipment\nE\nSATELLITE RECEIVER\nDIGITAL COMPUTER\nDUAL CHANNEL\nPHOTOREADER\n-\nREMOTE VIDEO DISPLAY\nKEYBOARD/PRINTER","254\n100\nNO COMPUTER CONTROL\n80\nWITH COMPUTER CONTROL\n60\n40\n20\n0\n10\n20\n30\n40\n50\n60\n70\n80\n90\nLATITUDE (DEGREES)\nFIG.\n4 Average Interval Between Satellite Fixes (6 Satellites)\nMETERS\n1.\nUNCORRECTED PROPAGATION EFFECTS (3RD ORDER\n1-5\nIONOSPHERIC AND NEGLECTED TROPOSPHERIC\nEFFECTS)\n2.\nINSTRUMENTATION (NAVIGATOR-SATELLITE\n1-6\nOSCILLATOR PHASE JITTER)\n3.\nGEODESY (UNCERTAINTY IN THE GEOPOTENTIAL\n15-20 (APL 4.5)\n5-10 (WGS-72)\nMODEL)\n4.\nINCORRECTLY MODELED SURFACE FORCES\n10-25\n(SECULAR ERROR GROWTH DUE TO INCORRECT\nPERIOD, DRAG, AND RADIATION PRESSURE)\n5.\nUNMODELED UT1-UTC EFFECTS AND INCORRECT\n1\nCOORDINATES OF THE POLE\n6.\nEPHEMERIS ROUNDING ERROR (LAST DIGIT OF\n5\nEPHEMERIS IS ROUNDED)\nRSS 19-33 M\n12-28 M\n(APL 4.5)\n(WGS-72)\nFROM: NAVIGATION, VOL, 22, NO. 4,\n1975-1976, PP. 352-360\nFIG. 5 Transit System Surveyors Error Budget (Single Pass)","255\n'P'\n(I)\n(A)\nT\nA\n(B)\nB\nEFFECT OF ORBIT ERROR IS COMMON\nTO EACH OBSERVER. DIFFERENTIAL\nPOSITION IS ACCURATELY DETERMINED\nFIG. 6 Principle of Translocation\nrecorded Translocation data. can be implemented either in \"real time\" or by post-processing\nThus, The only difference is how fast the remote data reaches the of\nwhere a communications link permits \"real time\" translocation, including applications computer.\nother. each site has its own computer, and the computers communicate with each\nApplications\nAs you would expect, surveys are conducted with satellite equipment only when this\nhave approach learned is cost effective. As the price of equipment has dropped and as more\nover the of its advantages, the number of applications has increased dramatically people\npast few years.\nAn For early application was to establish bench marks for remote sensing (aerial) surveys.\ntied to example, aerial mapping of the Amazon basin with side-looking radar has been\nfew geographical coordinates by means of corner reflectors on towers placed every\nkilometers. Magnavox satellite survey equipment was used to establish the\nposition of each tower.\nventional In general, satellite survey is used in places that are difficult to reach, where\nbeen survey techniques are too slow and too costly, or where local control con- has not\ndrill well established. For example, it is common practice today to position offshore\nland rigs by satellite survey. Finding or verifying the position of drilling sites on\nis another frequent use.","256\nFor large areas without adequate control, survey by satellite is ideal. National\ngovernments such as Australia and Canada are actively involved in establishing control\nmarkers by means of satellite survey equipment.\nPoint Positioning Accuracy\nSystem accuracy can be defined only with respect to an absolute reference.\nUnfortunately, no such thing exists. It might be possible to define the satellite system\nitself as the absolute reference, in which case repeatability would be the same thing\nas accuracy. The Navy took a major step in this direction by adopting the WGS-72\ngeopotential model for prediction of satellite orbits by the Naval Astronautics Group,\nwhich is the same model used for calculation of \"precise ephemeris\" orbits by the\nDefense Mapping Agency (DMA). Prior to December 1975, a different geopotential\nmodel (APL-4. was being used for each purpose. Results obtained with transmitted\norbit parameters always were offset from results computed with the precise ephemeris.\nIt is unfortunate, I believe, that in implementing WGS-72 at the Naval Astronautics\nGroup, a longitude rotation was applied in order to preserve the old longitude reference.\nAs it turned out, the effort was in vain. Position shifts on the order of 10 meters\noccurred across North America and in Europe upon conversion from APL-4. 5 to\nWGS-72 geodesy, and the old longitude reference was lost due to these unexpectedly\nlarge changes.\nPerhaps it is not too late. I feel it would be better for all doppler survey work to be\nbased on identically the same geodesy. Thus, even if not correct in an \"absolute\"\nsense, Doppler survey results would mean the same thing whether computed by DMA\nor by an individual using the broadcast ephemeris.\nThe position shifts which occurred upon changing to WGS-72 geodesy were greater\nthan expected and confirm that the satellite system is not an absolute reference.\nFuture \"improvements\" will cause other position shifts. However, the satellite system\nis the best worldwide reference we have today, and in some situations it can be accepted\nas an absolute standard.\nThe subject of datum shift is too extensive for this paper (References 2, 3, and 4).\nHowever, it must be stated that the latitude and longitude from a satellite survey\nsurely will differ with that from a terrestrial survey based on the local datum, e.g.,\nNorth American datum, European datum, Tokyo datum, etc. It is possible to convert\nfrom one datum to another, but the conversions are never exact for a host of reasons.\nThis subject is too little understood, but it is extremely important in properly applying\nthe results of surveys with satellite equipment.\nAs reported in Reference 5, Magnavox was first to develop a three-dimensional, multi-\npass, point positioning program which operated in a minicomputer. This program\nhas provided uncounted hundreds of reference positions since its introduction in 1971.\nThe convergence of latitude, longitude, and altitude as more passes enter the solution\nis shown by Figure 7. Figure 8 summarizes the rms repeatability of the final results\nwith 10, 25, or 50 pass solutions. Five meter repeatability with transmitted orbit\nparameters has been available for some time.\nMagnavox has introduced a new survey program this year, as described by References\n6 and 7. The new program is written in FORTRAN so it can run on a variety of com-\nputers. At this conference the program is operating in a Hewlett-Packard minicomputer\ndemonstrating real time point positioning and translocation.","257\n32\n28\n24\nLATITUDE\n20\n16\n12\n8\nDEVIATION FROM\n4\nFINAL RESULT\n(METERS)\nLONGITUDE\n0\n-4\nHEIGHT\n-8\n-12\n13-14 FEB 71\n-16\nTORRANCE, CA\n-20\n-24\n-26\n10\n20\n30\nPASSES\nFIG. 7 Convergence of Three - Dimensional Fix Solution\nFigure 9 is a plot of 3-D point positioning results obtained with the new program. The\nnumber beside each dot indicates how many passes were used for that position fix.\nThe origin of the coordinate system was established by the previous generation\nprogram, showing about three meters of bias between the two types of solution. There\nis some improvement in horizontal point positioning repeatability with the new program,\nbeing 7 meters versus 8. 9 meters with the old program. For 25 passes the numbers\nare 5 and 5. 6 meters, respectively. Thus, there is only a little to be gained from the\nnew program for point positioning, unless a precise ephemeris is available. Its real\nadvantage is for translocation, which will be discussed below.\nFigure 9 clearly shows the effect of converting from the APL-4. 5 to the WGS-72\ngeodesy. Two points (with 22 and 27 passes) have been circled. These were computed\nfrom satellite data taken after conversion to WGS-72 geodesy. The offset from old to\nnew is northeasterly by about 11 meters at Torrance, California. The direction and\nmagnitude will be different in other parts of the world.\nLATITUDE\nLONGITUDE\nALTITUDE\nRADIAL\n10 PASS SOLUTIONS\n6.63\n6.0\n3.2\n9.3\n25 PASS SOLUTIONS\n4.1\n3.8\n2.7\n6.3\n50 PASS SOLUTIONS\n2.6\n3.6\n2.0\n4.9\nFIG. 8 3-D Solution Repeatability (Meters)","258\nMETERS\n-12\n11\n-10\n-9\n-8\n-7\n-6\n-5\n-4\n-3\n-2\n-1\n0\n1\n2\n3\n4\n5\n6\n7\n8\n9\n10\n11\n12\n9\n9\n10\nO 22\n10\n8\n8\n27\n7\n7\n25\n6\n10\n6\n5\n5\nTHREE DIMENSIONAL\n4\nFIX RESULTS (4/76)\n4\nNOTES:\n3\n3\n1) THE NUMBER OF PASSES\n50\n2\nIS INDICATED BESIDE\n51\n2\nEACH RESULT\n77\n1\n10\n2) = WGS-72 GEODESY\n1\n93\n= APL-4.5 GEODESY\nMETERS 0\n0 METERS\n3) APPROXIMATE\n.1\nHORIZONTAL\n1\n@\n26\n25\nACCURACY:\n10\n2\n2\nNO. PASSES METERS RSS\n3\n-3\n10\n7\n4\n25\n5\n-4\n10\n5\n-5\n10\n6\n-6\n7\n-7\n-8\n-8\n-9\n-9\nFIG. 9\n3-D Point Positioning Results\nAll of the results described so far were obtained with orbit parameters directly\nreceived from Transit satellites. By definition, these orbits were predicted from\nground tracking data one to two days old by the time of the satellite pass. By deter-\nmining the orbits with tracking data taken near the time of the satellite pass, greater\naccuracy can be achieved. This is the technique used by DMA, and the improved\norbit definition is called a \"precise ephemeris\". Precise ephemeris tapes are pro-\nvided only on a government-to-government basis and are not available for commercial\nuse. With them, however, point positioning with one meter repeatability is possible\nafter about 40 satellite passes.\nTranslocation Accuracy\nFigures 10 and 11 show translocation results between two antennas which were very\nclose to each other so relative position could be determined with great accuracy.\nEach dot shows the difference between the translocation result and the survey\nreference. All satellite passes above 15 degrees maximum elevation were used.\n(The Magnavox programs make good use of passes all the way to 90 degrees of elevation.)\nFor this test, manual editing forced a balance of east and west passes for the four-\npass solutions. For the eight-pass solutions, an imbalance of five versus three was\nallowed. Otherwise, all other editing was performed automatically. The horizontal\nrms accuracy was 1. 09 meters for the four-pass solutions and 76 centimeters for the\neight-pass solutions. As we will discuss later, this is a measure of quality both of\nthe computer program and of the receivers being used for the test. In fact, it should\nbe noted that the Geoceiver II receivers were operated independently and with their","259\nMETERS\n-2.0\n-1.5\n-1.0\n-.5\n0\n.5\n1.0\n1.5\n2.0\nI\nTRANSLOCATION BETWEEN\n2.0\nBUILDINGS\n(4-PASS SOLUTIONS)\nSTATISTICS\n1.5\nMETERS RSS\nLAT.\n.44\n=\n1.0\nLON.\n1.00\n=\nHORIZ\n1.09\nALT\n.76\n=\n.5\nD= 53-PASS SOLUTION\n. = 16-PASS SOLUTION\n0\nMETERS\n-.5\n1.0\n-1.5\n-2.0\nFIG. 10 4-Pass 3-D Translocation Results\nMETERS\n.5\n1.0\n1.5\n2.0\n-2.0\n-1.5\n-1.0\n-.5\n0\nTRANSLOCATION BETWEEN\n2.0\nBUILDINGS\n(8-PASS SOLUTIONS)\nSTATISTICS\n1.5\nMETERS RSS\nLAT. =\n.21\n1.0\nLON. =\n.73\nHORIZ =\n.76\nALT =\n.47\n.5\nA = 53-PASS SOLUTION\n= 16-PASS SOLUTION\n0\nMETERS\n-.5\n1.0\n1.5\n-2.0\nFIG. 11 8 - Pass 3-D Translocation Results","260\nown crystal reference oscillators. It is possible that better results could be obtained\nwith a common antenna and/or a common oscillator or through use of rubidium or\ncesium frequency standards. Some of these conditions are interesting, but they do\nnot represent the normal mode of operation which these tests were intended to\nmeasure.\nFigure 12 plots the results from nine translocation trials. In each case, the satellite\nantenna was positioned over a first order survey marker. The plot shows the difference\nbetween the satellite survey and the terrestrial survey results. Because neither type\nof survey is perfect, the curve represents an upper bound on probable translocation\nerror as a function of distance between antenna sites. It is useful to note that accuracy\nas a percentage of distance improves as the distance increases.\nEvolution of Equipment\nThe Beginning\nIn the April 1960 Proceedings of the IRE (Reference 8) George Weiffenbach described\nthe Doppler measurement techniques which had been developed to monitor the early\nTransit satellites. The equipment was assembled from commercially available\nreceivers, tracking filters, etc. Only in this way could the global tracking network\nwe call TRANET be developed and deployed rapidly. Figure 13 is a photograph of\none such station.\n1.8\nDATA POINTS\nSYMBOL\n1.6\nO\nO\nHORIZONTAL CONTROL\n3-D RADIAL CONTROL\n1.4\nTHREE DIMENSIONAL RADIAL CONTROL, E\n1\n1.2\n1\n500,000\n1\n100,000\n50,000\n10,000\n1.0\n1\nA\n500,000\nHORIZONTAL CONTROL, E H\n.8\n1\n100,000\n1\n50,000\n.6\nOTHER DATA POINTS\n1\n10,000\nR\nE\nH\nCURVE FITS BY LOGRITHMIC\n.4\n.147\n.33\nREGRESSION\n.03\n.19\nE = Ao + A1 In(R)\n1\n10\n100\n1000\nDISTANCE BETWEEN STATIONS, R - KILOMETERS\nFIG. 12 Translocation Results Versus Range","FIG. 13 TRANET Station","262\nThe Doppler measurements made by TRANET and by the AN/BRN-3 which was\ndesigned to navigate Polaris submarines are interpreted as frequency measurements.\nThe received satellite signal is compared to a local reference frequency standard.\nThe resulting difference frequency is counted, and the time interval required to count\nN cycles is measured. Thus, the number of cycles divided by the measured period\nis interpreted as frequency. Each measurement lasts about one second, and a few\nhundred are taken during a typical satellite pass. The difficulties inherent in this\nprocess are: (1) determining when during the one-second interval the measured fre-\nquency actually occurred, (2) maintaining precise calibration of the digital clock which\nrelates Doppler measurement to time, and (3) recording and forwarding several hundred\nmeasurements per satellite pass.\nIn 1960, a different type of Doppler measurement was suggested which would eliminate\nthe three difficulties. The suggestion was to count the Doppler difference frequency\nover a relatively long time interval, with the counts beginning and ending upon receipt\nof time marks from the satellite. This approach eliminates the requirement for an\naccurate digital clock, and only a few Doppler measurements must be stored and\nprocessed. Furthermore, the counts can be interpreted as a measure of the change in\nrange between satellite and receiver. This technique is known as the integrated Doppler\nmeasurement because each Doppler count is an integration of the receiver Doppler\nfrequency.\nThe first equipment to use the integrated Doppler technique was the AN/SRN-9 (XN-5)\nshown in Figure 14. At least two dozen of these sets were built by the Applied Physics\nLaboratory to provide the Navy with an interim surface ship satellite navigation\ncapability. More important was that the simplicity and the accuracy of the integrated\nDoppler technique had been proved, and with one exception every Transit receiver\ndevelopment since then has employed this technique.\nMagnavox began its involvement with satellite navigation through the AN/SRN-9 (XN-5).\nWe designed and built all of the antenna/preamplifier units, and we manufactured to\nAPL drawings most of the phase-locked receivers.\nMagnavox Evolution\nIn the mid-1960's, point positioning by satellite had begun. A \"portable\" survey station\nconsisted of equipment like that shown in Figure 13 mounted in a trailer. Regardless\nof the transportation difficulties, the advantages of satellite survey had been recognized\nand a vigorous field program had begun.\nIn 1965 (Reference 9) this author formally proposed development of a truly portable\ninstrument for land survey. The instrument was called Geoceiver. The initial phases\nof development were conducted at APL, but the development was completed by Magnavox\nunder contract to APL. Figure 15 shows the AN/PRR-14 Geoceiver, 55 of which have\nbeen built by Magnavox and deployed for land survey work around the globe. The\nGeoceiver has earned an enviable reputation for accuracy and for reliability.\nFigure 16 shows the evolution of Magnavox Satellite Doppler receivers from the original\nGeoceiver. In 1968, the first Magnavox dual-channel satellite receiver became avail-\nable. Fifty of these MX 702CA units were built and are in operation today. Their\nprimary application has been for shipboard satellite navigation. A derivative of the\nMX 702CA receiver was the AN/WRN-4, 37 of which were built and deployed. This","263\nprescription\nFTC.","264","-------------------\nMX-1102\nGEOCEIVER II\nMX-902A/B\nAN/WRN-5\nFIG. 16 Magnavox SatNav Receiver Genealogy\nMX-902\nMX-702A\nAN/WRN-4\nMX-702CA\nGEOCEIVER\nAN/PRR-14\niiiii","266\nwas the first satellite navigator with the computer, receiver, display, keyboard, and\npower supply packaged in a single integrated unit. Most of these systems were obtained\nby the Office of Naval Research and are being used for navigation of oceanographic\nresearch vessels.\nIn 1971, Magnavox introduced the MX 702A receiver and its less expensive brother,\nthe MX 902 single-channel receiver. The new design allowed us to hold down costs\nand to improve maintainability by taking maximum advantage of the latest integrated\ncircuits. The number of electronic modules was reduced dramatically, permitting\nfield repair by replacement of a functional module. Built-in self-test permits\nverification of proper receiver operation and aids in troubleshooting. The single-\nchannel MX 902 receiver was intended for navigation of commercial ships such as\ntankers, freighters, fishing vessels, etc. The dual-channel MX 702A has been used\nfor oceanographic surveys and offshore oil exploration. In addition, it has been used\nwidely for precise positioning of offshore drill rigs and land survey sites when con-\nfigured as shown in Figure 2. As of this date, a total of 415 MX 702A and MX 902\nreceivers has been delivered. Because of module commonality we have been able to\nestablish a worldwide network of service centers which care for both types of\nreceiver.\nThe AN/WRN-5 system was developed by Magnavox for the U.S. Navy. The AN/WRN-5\nis a more modern and more flexible version of the AN/WRN-4. The diagram shows that\nin this instance the MX 702A commercial receiver technology was used as the basis for\nthe military AN/WRN-5, 44 of which have been delivered and 33 more are in production\nat this date.\nBecause of increasing interest in land survey applications and in order to take maximum\nadvantage of the new translocation software, Magnavox introduced the Geoceiver II in\n1975. Most Geoceiver II components are directly interchangeable with the MX 702A\nreceiver. Thus, spare parts and service support are readily available around the\nworld. The differences between the Geoceiver II and the MX 702A are the addition of\ntwo new modules which provide a Doppler clock capability and use of a reference\noscillator selected for optimum stability. We believe no other commercial satellite\nreceiver can provide better measurement precision.\nFigure 16 also shows the exciting evolution in single-channel navigation equipment.\nIn 1975 the need for a separate receiver unit was eliminated by the MX 902A. The\nreceiver was implemented with two electronic modules plus an oscillator which plug\ninside the digital computer. Thus, many electronic modules and the need for a separate\nchassis and power supply were eliminated. The result was a substantial improvement\nin reliability with no sacrifice in performance. The MX 902A was followed in early\n1976 with the MX 902B, in which we began to use the new Hewlett-Packard 2105 Com-\nputer. Again, the result was a smaller package, fewer components, and better\nreliability.\nThe most exciting step occurred in July of 1976 with the introduction of the MX 1102.\nAs described by Reference 10, the MX 1102 combines the satellite receiver, computer,\nkeyboard, display function, and power supply in a single attractive enclosure. The\nkey to this breakthrough was in fully harnessing the power of the microcomputer. The\nnew system anticipates each satellite pass and preferentially tracks those which are\nmost likely to give an acceptable position fix. In addition to satellite position fixing,\nthe unit automatically dead reckons with speed and heading inputs, computes the great\ncircle or rhumb line distance and bearing to any selected waypoint, and provides auto-\nmatic compensation of set and drift errors. Perhaps most dramatic are its self-test","267\nand diagnostic capabilities. Periodic tests of every electronic module are conducted.\nIf a failure is detected, the most likely module to replace is indicated on the display.\nField maintenance by people with minimum training is now entirely feasible.\nWe at Magnavox are proud of the record these satellite navigation and survey products\nhave made for accuracy, reliability, and functional capability. Figure 16 illustrates\nthat at Magnavox the development of new products is a continuing commitment.\nReceiver Design Parameters\nQuality Standard\nThe new few sections of this paper will discuss the receiver design parameters and\nhow they influence accuracy performance. Such details are critical to the designer,\nand they are important to sophisticated users in the purchase of equipment or in pre-\nparing their own computer programs. However, there is a test for quality which is\neasy to do and which is very meaningful. This is the comparison of position fix\nresults obtained from two systems using either a common antenna or having antennas\nat precisely known relative positions. We call this colocation even though with two\nantennas it is a form of nearby translocation.\nFigure 10 shows 16 individual 4-pass translocation results. The overall horizontal\nerror was 1. .09 meters rms. Figure 11 shows nine 8-pass translocation results with\na horizontal error of 0. 76 meter rms. The error contribution per satellite pass can\nbe obtained by multiplying by the square root of the number of passes involved,\nyielding 18 and 2. 15 meters rms respectively. Dividing by the square root of 2\ngives the error per pass from an individual receiver. These tests indicate that the\nGeoceiver II is responsible for less than 1. 5 meters of fix error. Another more limited\ntest gave a result of 2. 5 meters. Thus, a good Doppler receiver should introduce less\nthan 3 meters rms of position fix error on a single-pass basis.\nThis type of test is very sensitive to any problem in the receivers. A poor oscillator\nor other defect will cause immediate growth in colocation error. Another factor\nwhich will degrade performance is presence of jamming signals. We pride ourselves\non building receivers which are the least sensitive to being jammed. However, many\nof our trials are made in the laboratory where satellite receivers are being tested, and\nthese tests require just the signals to jam satellite passes. Such problems are quickly\ndetected by colocation trials.\nAnother good measure of receiver performance can be obtained by observing individual\npass residuals. We have found that satellite passes should be rejected if pseudorange\nDoppler residuals exceed 20 or 25 centimeters rms. Typically, they lie in the range\nof 5-10 centimeters. This type of test does not require a second receiver, and it\nseems to be equally sensitive to detecting poor performance. The only limitation is\nthat the actual impact on fix error is not readily apparent.","268\nThe Integrated Doppler Measurement\nThe following equations define the integrated Doppler measurements:\ntj\n(1)\nwhere:\nthe Doppler count\nNj\n=\nexact time at which the first cycle began\nj-1\n=\ntj\nexact time at which the last cycle ended\n=\nEG\nground reference frequency (often 400 MHz)\n=\nfR\ninstantaneous frequency being received\n=\n(2)\nwhere:\ntj\nthe time recorded by the receiver's digital clock\n=\nAt\nthe clock epoch error at time tj\n=\nAti\nthe clock reading error due to quantization\n=\n(3)\nwhere:\nthe time at which the j'th timing signal was\n=\ntransmitted from the satellite\nstap\nthe propagation time delay from satellite to\n=\nreceiving antenna\nAt r =\ntime delay through the receiver\n=\nAti\nrandom time recovery jitter\n=\nAtja\nrandom delay from recognition of time mark to\n=\ncompletion of the last Doppler cycle.","269\nEquation 1 defines the integrated Doppler measurement. The satellite receiver forms\nthe difference frequency (f G - fR), where fG is the internal or ground reference fre-\nquency and f. R is the frequency being received from the satellite. If fG is 400 MHz,\nthe difference frequency varies from about 24 kHz to 40 kllz. A hardware counter\nintegrates this frequency by counting the number of cycles between times '--1\nand\n1j.\nThese limits represent the precise times at which the first cycle of the count began\nand when the last count ended. Receivers such as the AN/PRR-14 Geoceiver and the\nGeoceiver II have digital clocks to record these time marks for each Doppler count.\nEquation 2 shows that the value of time recorded differs from the true time by the\nclock epoch error at that instant plus a small error due to clock quantization. For\nexample, the original Geoceiver clock quantized time to within +2 microseconds,\nwhereas the Geoceiver II quantizes time to within +0. 5 microsecond.\nEquation 3 shows that the actual start and stop time of each Doppler count is a function\nof many variables. Those which influence the receiver design characteristics will\nbe discussed in more detail later.\nEach Doppler cycle count is scaled by the wavelength at 400 MHz, which is approximately\n75 centimeters. Thus, a one cycle error in the count would cause 75 centimeters of\nmeasurement noise. Because this gives an excellent physical meaning to the Doppler\nmeasurement process, all sources of Doppler count error to be discussed will be\nmeasured in centimeters.\nOscillator Stability\nMost point positioning and translocation computer programs assume that the ground\nreference frequency fG and the frequency transmitted by the satellite remain constant\nduring the satellite pass. Some programs introduce another variable to solve for\nlinear drift in the difference between these frequencies. However, it is clear that\nstability of the reference frequency is an important design parameter.\nAn example will be helpful in understanding the effects of oscillator stability on Doppler\ncount accuracy. Austron, Inc., advertises its Sulzer Model 1150 Crystal Oscillator\nas \"specifically developed for use in satellite navigation systems\". Although these\nspecifications are not adequate for precise translocation, they serve as a good\nexample:\nAUSTRON MODEL 1150 SPECIFICATIONS\n-10\nAging rate:\n10\nper day after 24 hours\n1 x 10 -\nper day after 30 days operating\n5 x 10 - 11\nper day typical after 90 days\nStability (1)\nless than +2 x 10 - 11\nrms for 120 second\naveraging time\nx 10 - 11\nless\nthan\n+1\nrms for 1 second averaging\ntime.","270\nAUSTRON MODEL 1150 SPECIFICATIONS (Continued)\n(1)\nStability\n(cont.)\n-10\nless\nthan\n10 for 10% change from 27 VDC\n+5\n-9\ntotal change from -55°C to\nless\nthan\n10\n+60°C\nIt is extremely clear that a very stable power supply voltage must be maintained and\nthat sharp temperature changes must be avoided in order to achieve proper per-\nformance. For example, a 1 percent change in power supply voltage can cause a\n-11\n10\nchange in frequency.\nX\nA changing oscillator frequency causes an apparent change in distance between the\nreceiver and the satellite. It is useful to convert the various stability parameters\ninto their effect on apparent distance to the satellite over a typical 15-minute pass.\nIf aging rate were constant throughout the day, the effect would be:\nEFFECT OF CONSTANT FREQUENCY DRIFT ON APPARENT RANGE\nCHANGE IN 15 MINUTES\nAging Rate\nApparent Range Change\n9\n1 x 10\nper day\n140 cm\n10\n5 x 10\nper day\n70 cm\n10\nper day\n14 cm\n-11\n10\nper day\nX\n7 cm\nUnfortunately, aging rate is not constant, so that frequency drift will vary during the\nday above and below the average 24-hour rate. Testing of the oscillator must take\nthese variations into account, because the accuracy of a satellite fix is dependent on\nthe drift rate during that specific 15-minute interval.\nSlow oscillator drift is insidious in that it may have little effect on the Doppler residuals\nin a satellite fix. Instead, the drift may map directly into latitude, longitude, or\naltitude offsets, SO the Doppler fit appears to be excellent. On the other hand, short,\nrandom variations of oscillator frequency about a constant mean value tend to increase\nthe Doppler residuals but have less effect on the position fix result.\nThe stability specification defines frequency variation about a mean value over a\nlimited period of time or variation about a simple curve fit to the individual frequency\nmeasurements. For example, stability could be defined as the rms deviation from a\n(1) An rms value can only be positive, so it is incorrect to precede the rms stability\nvalues with +, as is done in most oscillator data sheets.","271\nstraight line fit over a specified time interval. Unfortunately, these details are not\nprovided by the data sheet. However, having defined the effect of a constant drift rate,\nwe may examine the effect of \"stability\" as if the drift rate were zero.\nIf 1-second frequency samples were statistically independent, then 100-second frequency\nsamples would have a standard deviation one-tenth as large. The specifications show\nthat this is not the case. Instead, the stability is about the same at 1 second as at\n100 seconds. This simply means that frequency variations are quite slow so that short,\nadjacent samples are highly correlated. If we could assume that 100-second samples\nwere independent, then the effect of frequency variation on apparent range change in\n15 minutes would be:\nEFFECT OF RANDOM FREQUENCY VARIATIONS ON APPARENT\nRANGE CHANGE IN 15 MINUTES\nFrequency Stability\n(100 second average)\nApparent Range Change\n-11\n10\n90 cm\nrms\n12\n5\n10\n45 cm\nrms\n-12\n10\n9 cm\nrms\nIf our assumption of statistical independence of the 100-second samples is not valid,\nthen the apparent range change effect is less than indicated.\nIt seems that a clearer definition of oscillator stability is needed for satellite survey\nwork. I would like to propose integration of frequency error over perhaps 50 or 100\nconsecutive 15-minute intervals. For each interval, we could determine the peak-\nto-peak change in apparent range due to frequency variation, regardless of the nature\nof that variation. By forming the root sum square (rss) of these individual samples,\nwe would have a very meaningful indication of oscillator stability in terms of its true\neffect on Doppler count accuracy. Also, a cumulative probability curve of apparent\nrange change magnitude would help spot intermittently large fluctuations.\nDoppler Count Precision\nAlthough a stable reference oscillator is extremely important to Doppler measurement\naccuracy, a precise Doppler measurement technique is equally important. The hard-\nware counter accumulates the number of Doppler cycles between receipt of timing\nmarks from the satellite. In Equation 3, there are two random error terms which affect\nthe actual start and stop times of each Doppler count. One, stj. is time error due to\nnoise-induced jitter in the time recovery circuits. The other, At, is the delay between\nrecognition of the time mark and completion of the last cycle to be counted. These two\neffects, which are illustrated by Figure 17, cause from 150 to 225 centimeters of noise\nin each Doppler count. For normal navigational purposes, this level of Doppler count\nnoise is entirely negligible. However, for precise translocation where Doppler\nresiduals should be in the 5 to 10 centimeter region, such jitter is enormous.","272\nOFFSET\nDOPPLER\nFREQUENCY\nTIME RECOVERY JITTER\nFIG. 17 Reason for the Clock Option\nTo eliminate the problem, both the original Geoceiver and the Geoceiver II have digital\nclocks which measure the precise time interval of each Doppler count. Thus, by\nmodifying the position fix equations to take advantage of the clock readings, a far more\nprecise Doppler measurement can be made. In fact, the only error which remains is\nshown in Equation 2 by the term st,9, which is the clock readout quantization. The\noriginal Geoceiver has a quantization of +2 microseconds, and the Geoceiver II has a\nquantization of +0. 5 microsecond, The worst error occurs when counting the highest\nfrequency, which for the original Geoceiver was about 40 kHz. Because of a different\nfrequency synthesis, the highest Geoceiver II frequency is about 28 kHz. With a\nuniform probability of +X microseconds of error on either end of a count, the timing\nerror distribution for each count is a triangular function. For the original Geoceiver,\nthe rms timing error over each count is 1. 63 microseconds and for the Geoceiver II\nthe error is 0.41 microsecond, In proportion to the period of the maximum frequency\nbeing counted and scaled by the 75 centimeter wavelength, the rms noise due to clock\nquantization is 4. 9 centimeters for the original Geoceiver and 0.86 centimeter for the\nGeoceiver II. We believe the Geoceiver II has the smallest Doppler quantization noise\nof any receiver available today.\nRefraction Correction Measurement\nA. first order ionospheric refraction correction can be made by comparing the 150 MHz\nand 400 MHz signals received from the satellite. In the original Geoceiver, the\n150 MHz receiver is slaved to the 400 MHz receiver. A phase-locked tracking circuit\nrecovers and multiplies the refraction error frequency, which is counted over the\nsame intervals as the 400 MHz Doppler frequency. In applying the refraction correction,\nthe refraction cycle count is divided by 9-1/6, so that count truncation of +1 cycle\n(0. 41 cycle rms) results in 3. 3 centimeters of noise added to the Doppler count.","273\nThe Geoceiver II employs two independent phase-locked receivers to track the 150 MHz\nand 400 MHz signals. Also, independent Doppler counts are made for the two channels.\nThe 150 MHz Doppler frequency is scaled to be the same as the 400 MHz channel, and\nclock readings to the nearest microsecond also are made. The result is that a\nfractional count can be derived which precisely matches the integer 400 MHz count,\nwith an equivalent resolution of 0.86 centimeter. To apply a refraction correction,\nhowever, the difference between the two counts is scaled by 9/55, so the additional\nnoise from refraction correction is 14 centimeter rms. The overall refraction\ncorrected Doppler count thus has an error of only 0.87 centimeter rms attributable to\nclock quantization on both channels.\nAt Magnavox we believe the magnitude of the refraction error should be preserved in\nthe raw data. This permits study of the ionosphere, higher order modeling if desired,\nand a measure of reasonableness which can be helpful in data editing or in detecting\nif one receiver channel locks briefly to a spurious signal or to another satellite,\nTime Delay\nEquation 3 contains a term At which represents the delay through the receiver in\nrecognizing a satellite time mark. Depending on the type of receiver, this delay can\nrange from 50 to perhaps 700 microseconds. Because it can be measured with an\nexternal test set or calibrated as part of the point positioning solution with multiple\nsatellite passes, the absolute magnitude of this delay is of little importance. The most\nimportant characteristic is its stability. Therefore, a good receiver design will seek\nto maintain a constant delay over a wide temperature range and for long time periods.\nThe major factors in causing time delay are the phase slope characteristics of the\nnarrowband filters and offset voltages in the time recovery loop.\nWith a digital clock, the magnitude of time recovery jitter is of little importance\nexcept in making the apparent time delay more noisy. Therefore, another receiver\ndesign objective is to minimize time recovery jitter with narrowband, phase-locked\ntracking of the timing signal.\nSignal-to-Noise Ratio\nNarrowband phase-locked loops are used to track the incoming satellite signals to\nderive a clean measure of Doppler frequency. Even though these are very narrow\nfilters, they are affected by the incoming signal-to-noise ratio. At threshold signal\nlevels, where the loop is about to break lock, the noise amounts to about 5.5\ncentimeters rms of jitter. With a 10 dB stronger signal, the noise jitter is reduced\nto 1.9 centimeters rms, which produces 2. 65 centimeters of noise per Doppler\ncount.\nTherefore, obtaining strong, noise-free signals is very important when trying to\nachieve 5 centimeter Doppler residuals.\nAntenna sensitivity and receiver noise figure are the two most prominent factors in\nachieving clean signals. Competing with noise figure, however, is the need for narrow-\nband filters in the RF amplifiers to exclude adjacent channel jamming signals. A care-\nful trade-off between noise figure and jamming immunity must be made in any receiver\ndesign. Good filtering does worsen receiver noise figure somewhat, but preventing\ntotal receiver jamming is even more important in many instances.","274\nAntenna Pattern\nUse of a good antenna is often vital to best system accuracy. It is important that the\nantenna phase center at both frequencies be coincident. In the Magnavox antenna\nshown in Figure 2 (manufactured by Chu Associates of San Diego) the phase center is\nlocated at the intersection of the vertical centerline and the plane formed by the lower\nground radials. (Because the original Geoceiver antenna, shown in Figure 15, had to\noperate at four frequencies rather than two, it is considerably more complex. Dis-\nplacement of phase centers has been suspected in the original Geoceiver antenna, a\nproblem which does not exist in the Geoceiver II antenna.)\nOther important antenna characteristics are sensitivity and pattern. To be sensitive\nit must be large enough physically to gather the incident energy. This characteristic\nis called capture area. Too large a structure, however, leads to multiple lobes in\nthe antenna pattern. For example, the \"ears\" on the Geoceiver II antenna limit the\nelectrical height of the antenna above the ground plane at 400 MHz while allowing a\nfull half-wavelength height at 150 MHz. This approach assures smooth antenna patterns\nas shown in Figure 18. Note that the main lobes are tilted well above the horizon,\nminimizing multipath signals from below the horizon. The overhead null is a necessary\nevil, but it should be made as small as possible.\nIn addition to a good pattern, common phase centers, and adequate sensitivity, we\nbelieve a survey antenna must be rugged, easy to assemble, and capable of withstanding\na wide range of temperatures and a heavy wind load. Furthermore, all Magnavox\nantennas employ an integral preamplifier with filters. This assures a good noise\nfigure and adequate interference rejection for all installations. Thirty meters of light-\nweight antenna cable are always provided, and 60 meters of heavier cable can be used.\nFuture Trends\nMagnavox Doppler satellite receivers have always featured automatic operation,\nruggedness, reliability, built-in self-test capability, and modular field repairability.\nAs a result, they have been used widely for navigation and position determination of\nships, drill rigs, and for land survey. However, looking to the future we see that the\nlatest microcomputer technology can be made available for survey applications. We\nwould welcome your comments and suggestions.\nThe MX 1102 shown in Figure 16 provides a view of what can be done with a micro-\ncomputer. It actually forms part of the receiver, controlling such functions as the\ntime recovery loop and tuning. Computer-controlled tuning permits rapid signal\nacquisition at the beginning of the pass and after any dropout. Perhaps more\nimportant, the computer preferentially tunes to those satellite passes which will give\na good fix result and ignores any interfering passes which would not. Diagnostic\ncapabilities under computer control are included on every module. Thus, either\nautomatically or as requested by the operator, a complete self-test may be performed.\nAny failure is flagged, and the most likely module causing the failure is indicated.\nWith this type of assistance, anyone with a minimum of training can repair the\nMX 1102. We believe that these characteristics may be of interest for land survey\nwork.","275\nRELATIVE AZIMUTH\nDIPOLE\nREF\nELEVATION\nMHz\nMHz\nE\n0\n400\nAZIMUTH PLANE AT\nZENITH PLANE AT\nPOLARIZATION: E\nSCALE FREQUENCY\nPATTERN CUT IN:\nFREQUENCY\ndb\nWITH PREAMPLIFIER\nPOWER\nANTENNA DFMA\nMagnavox Antenna Patterns\nDATE. 11-20-67\nLOCATION CHU\nPLOTTED IN:\nVOLTAGE\nFILE NO:\nPREAMPLIFIER\nRELATIVE AZIMUTH\nDFMA\nDIPOLE\nREF\nELEVATION\nMHz\nMHz\nFIG. 18\nE\n0\nAZIMUTH PLANE AT\n150\nZENITH PLANE AT\nSCALE FREQUENCY\nPOLARIZATION: E.\nPATTERN CUT IN:\nFREQUENCY:\ndb\nWITH PREAMPLIFIER\nPOWER\nDFMA\nDATE: 11-20-67\nLOCATION: CHU\nPLOTTED IN:\nVOLTAGE\nANTENNA:\nFILE NO:","276\nThe primary function of the MX 1102 microcomputer is to perform the satellite\nposition fix. It seems reasonable that fix results in the field would be a useful survey\ncapability. Not only would preliminary position information be obtained, but only\nt'rrough position fixes can the true performance be judged. For example, a bad\nscillator can be detected only by comparison with another oscillator or by evaluating\nposition fixes and the residuals which result. Thus, field calculations should be of\ninterest to the land surveyor, not only to obtain initial results but also to verify proper\nsystem operation.\nMagnavox has always favored the use of paper tape recorders for land survey. The\nprincipal reason for this preference has been the instant verification that data is being\nrecorded. We acknowledge the compact convenience of cassette tape recording and\nwe will provide that option when requested. However, there have been too many\ninstances of lost data with cassette recorders, so we are cautious. We see the micro-\ncomputer as a means of overcoming this limitation. Instant verification of a proper\nrecording can be achieved without requiring manual intervention. This we feel is\nanother opportunity for land survey use of the microcomputer.\nFinally, we acknowledge a trend toward more portable equipment. This we feel is\ndesirable for certain applications. However, we do not feel that field repairability,\nd-ta reliability, or system accuracy should be sacrificed purely for the sake of\nportability. Indeed, the massive logistic support required for people and for other\nequipment on most missions reduces the need for extreme portability. We will continue\nto evaluate this trade-off, but our primary concern will continue to be dependability\nand functional performance.\nA Magnavox, development of the MX 1102 points the way toward the future in land\nsurvey equipment. We are evaluating how best to use the power of the microcomputer\nas an aid to land survey. Such concepts as automatic and total data verification, on-\nsite fix results, and simple field repairability appear to be desirable and achievable\nobjectives. For best results the microcomputer should become an integral part of\nthe instrument, rather than an external box or a tack-on. Wewelcome your\nsuggestions.\nReferences\n1.\nStaff of the Space Analysis and Computation Group, Johns Hopkins University/\nApplied Physics Laboratory, \"Planned Improvements in The Transit System\n(1975)\", Navigation, Vol. 22, No. 4, Winter 1975-76.\n2.\nT.A. Stansell, \"Accuracy of Geophysical Offshore Navigation Systems\",\nOffshore Technology Conference Preprints, OTC 1789, April-May 1973.\n3.\nSimo H. Laurila, \"Electronic Surveying and Navigation, Chapter 28\", John\nWiley & Sons, 1976, ISBN 0-471-51865-4.\n4.\nT.O. Seppelin, \"The Department of Defense World Geodetic System 1972\",\nDefense Mapping Agency, Washington, D.C., May 1974.\n5.\nT.A. Stansell, \"Extended Applications of the Transit Navigation Satellite System\",\nOffshore Technology Conference Preprints, OTC 1397, April 1971.","277\n6. R.R. Hatch, \"New Positioning Software from Magnavox\", International Geodetic\nSymposium on Satellite Doppler Positioning, Las Cruces, New Mexico,\nOctober, 1976.\nR.R. Hatch, \"Point Positioning and Translocation Via the Transit Satellite\n7.\nSystem\", 46th Annual SEG Conference, Houston, Texas, October 1976.\nG.C. Weiffenbach, \"Measurement of the Doppler Shift of Radio Transmissions\n8.\nfrom Satellites\", Proceedings of the IRE, Vol. 48, No. 4, April 1960.\n9. T.A. Stansell, et al. \"GEOCEIVER: An Integrated Doppler Geodetic Receiver\",\nThe Johns Hopkins University Applied Physics Laboratory, TG-710, July 1965\n(Rev. November 1968).\nT.A. Stansell, \"Achieving Reliability in Automatic Navigation Equipment\", Second\n10.\nInternational Symposium on Ship Operation Automation, Washington, D.C.,\nAugust 1976.","278","279\nA CRITICAL ANALYSIS OF FIELD OPERATIONS USING\nPORTABLE, UNATTENDED DOPPLER SATELLITE INSTRUMENTATION\nPaul D. Rodgers\nJMR Instruments, Inc.\n20621 Plummer St.\nChatsworth, California 91311\nIntroduction\nThe work of the world community of surveyors and geodesists has now\nmade a giant leap forward through application of the satellite-doppler\npositioning technique, both in research and in daily survey tasks. No\nlonger is the question \"Can I use the technique? 11 but rather \"How can\nI more effectively apply it?\" Adjustment of primary geodetic reference\nsystems is now under way on most of the continents of the World using\nthe NNSS satellites. At the other end of the spectrum, one-man survey\ncompanies are now able to compete with the giants in daily point posi-\ntioning and control applications. A new era of speed and accuracy in\ngeodetic positioning has arrived.\nOver two years ago JMR introduced a survey instrument which has con-\ntributed to the rapid acceptance of the satellite-doppler technique. JMR\ncontinues to respond to the demands of the industry through its on-going\ndevelopment activity. Recent accomplishments include the SP-7T, a\nsurveyor-oriented field operable translocation program; an all-environ-\nment cassette reader with multiple function capabilities such as data tape\nduplication in the field; and a miniature, low-power, battery operated\nfield processor which adds position computation capability to the JMR-1.\nIt is the purpose of this paper to analyze the effectiveness of the new\nequipment capabilities which have been made available and to present an\ninsight into the potential for further improvement.\nBasic System Application Requirements\nThe planning of geodesists and surveyors has been projected to new\nlevels of imagination now that they have realized the application poten-\ntial of satellite doppler positioning. The JMR-1 System is finding new\nusers and new applications every day. Through a review of today's\nusers and their application requirements further insight may be gained\ninto the possibilities for the future.\nEarly non-military applications of the NNSS to positioning were in off-\nshore seismic surveys for determination of lane-count for shore-based\nhyperbolic positioning systems and as a gross check for operator error\nor equipment malfunction. The early users were primarily oil compa-\nnies and companies who provided navigation and positioning services for\noil companies.","280\nThe JMR-1 Doppler Survey Set, though applicable to both, was speci-\nfically designed for static positioning as opposed to offshore survey\nand navigation. Hence, the user community is different but still is\ndominated by applications rélated to oil exploration. Well over 100\nJMR-1 units are now in operation world-wide providing a sufficient\nsample of users to give some meaning to a percentage breakdown into\nuser categories, as follows:\n38%\nSurvey Service Organizations\n34%\nForeign Government Agencies\n11%\nU.S. Government Organizations\n15%\nOil Companies\n2%\nUniversities\nIt is not possible to indicate a positive statistical trend in the type of\nuser on the basis of the short two-year elapsed time since JMR-1\ndeliveries effectively started. However, it is interesting to note the\nrelative change in user percentages for the first and second years.\nFirst Year\nSecond Year\n33%\n47%\nSurvey Service Organizations\n17%\n44%\nForeign Government Agencies\n25%\n9%\nOil Companies\n11%\n11%\nU.S. Government Organizations\n3%\n0\nUniversities\nA significant increase in foreign government usage is apparent from\nthis comparison. These users are primarily government mapping\nagencies. The countries known to the writer in which the JMR system\nis being used for governmental agency purposes are as follows:\nEngland\nPeru\nAlgeria\nPhilippines\nFrance\nAustralia\nS. Africa\nIndia\nBolivia\nSpain\nJapan\nCanada\nUSA\nNigeria\nDenmark\nThe diversity in application of the JMR System is indicated by the fol-\nlowing listing of currently known uses.\nGeodetic Datum Adjustment\nEstablishing or Adjusting Mapping Control Points","281\nOffshore Drill Rig Positioning\nPositioning Shore Stations for use in Offshore Survey\nPositioning Shore-Based Navigation Transmitters\nSeismic Line Control\nMonitoring Ice Flow Movements\nOceanographic Research\nResolving boundary disputes\nTying Island Positions to Mainland Datum\nNavigation\nAiming Troposcatter Antennas\nRefining origin offsets for specific datum transformations\nThese applications have required that the equipment operate in nearly\nthe total range of environments existing on Earth, from the tropical\njungles to the deserts to the frigid climates of both the Arctic and the\nAntarctic.\nAlthough a wide range of applications has developed, a priority listing\nof basic user requirements can be established which is for the most\npart, at least, common to all users.\n(1) Accuracy of position determination\n(2) Reliable performance in the field environment\n(3) Speed in achieving the desired end result\n(4) Operational efficiency, in terms of simplicity of use and minimi-\nzation of logistic support\n(5) Equipment and software cost\nThe order of priority may appear to be incorrect in specific instances,\nhowever it is believed that the above order will prevail on the long term\nfor most users and for most applications. A brief justification of the\norder of priority follows\nAccuracy of Position Determination\nThis requirement is obviously paramount in the geodetic positioning and\nsurvey industry. When more accurate systems are developed, they\nwill prevail regardless of most other factors.\nReliable Performance in the Field Environment\nNNSS satellites can be viewed equally well from any point on the Earth,\nthus opening new frontiers for the surveyor. No area is now too remote\nto be considered practical for survey and control operations. This\nfact alone requires that the field equipment be reliable in its operation\nThe cost of an operation in remote areas, including the cost in time\n.\nand transportation to get in and out of the area make cost allowances","282\nfor equipment failure prohibitive to competetive bidding.\nFurther, due to the cost of transporting shelter and fuel it is essential\nthat the field instrument operate reliably when exposed to all types of\nweather environment. And because the nature of the technique makes\npossible fully-automatic unattended operation of the field instrument,\nthe operational environment is no longer limited to that which a human\ncan withstand. Since position results are often a component part of the\ncritical path involved in large construction project schedules, huge cost\nincreases can be incurred by equipment malfunction and subsequent\ndelay in results.\nSpeed in Achieving the Desired End Result\nThe cost of an operation increases in almost direct proportion to the\ntime required to complete it. A competetive job often goes to the lowest\nbidder. A research project budget allows greater productivity if less\ntime is spent in collecting the data, making more time available for\nanalysis of the data. Given that the previously discussed reliable and\naccurate performance of the field instrumentation is achieved, then\nthe time to obtain the specified positioning results becomes a major\nfunction of the associated data processing requirements. If the desired\naccuracy can be achieved with less data, both the field time and the\nprocessing time are reduced. The time required for the computation\nprocess itself is insignificant using today's high-powered computers.\nHowever the method used for handling the data in preparing it and in\nentering it into the computer can be extremely costly in time and labor.\nOperational Efficiency\nThe major factor here is the cost of transporting material and per-\nsonnel to the site and of maintaining them while there. If the equipment\nis complex to set up and operate, more personnel are required. If\nit is large and bulky, larger transport vehicles are necessary. And,\nmost important of all is the problem of transporting energy sources to\nmaintain power-hungry electronic equipment and for life support of\nmultiple resident personnel.\nEquipment and Software Cost\nThe cost of the field equipment, the computer equipment, and the soft-\nware is normally a small part of the total project cost for all but a\nsmall, one-time job. Todays well-constructed transistorized equip-\nment does not \"wear out\" for many years. However, obsolence of high-\ntechnology equipment is a factor to be considered in choosing the","283\ninstruments to be used and in long-term cost analysis. The purchase\nof state-of-the-ar equipment usually proves to be the most cost-\neffective approach.\nSome Typical Experiences\nCase histories of typical user operations will serve to emphasize the\nsignificance of the priority order of user requirements. Such case\nhistory details are difficult to obtain as it is very unusual for a manu-\nfacturer of electronic equipment to receive detailed feedback from\nusers on the performance of their equipment. \"No news\" is usually\n\"good news. 11 However, even feedback on user's failures and diffi-\nculties is welcomed by most manufacturers as it allows them to more\ncompletely adapt their product to their ers'applications. Field\nfeedback is extremely important as it is very difficult to accurately\nsimulate the real field environment at the factory, even when the\nfactory engineer has actually experienced the field environment him-\nself.\nJMR has been fortunate in having several users take the time and\neffort to provide excellent written reports. In addition the writer has\nhad the opportunity to experience the field environment on several\noccasions. By drawing on these experiences an attempt will be made\nto relate the effectiveness of some of the equipment features and to\nindicate some possibly desirable features not currently available.\nJungle Operation\nA user's report of the type which a supplier particularly cherishes is\nquoted almost verbatim in the following.\n\"Though not intended, I have travelled through primitive and rugged\njungles, rivers with rapids, intense heat and torrential downpours of\nrain with the JMR unit. The Receiver has survived and operated 100%\nan enviable performance. The Receiver in it's shipping case, has been\nthrown in the water, (boat overturned), bounced on rocks (trying to\nget it out of the water). struck by tree limbs, (shooting rapids in the\nrivers and travels through the jungle), functioned normally in massive\ntorrents of driving rain and intense suffocating heat (literally, you\ncould slowly fry an egg on the area next to the control panel) and\nsurvived the general rough handling of transport via the shoulders and\nbacks of native people who are not used to the idea of something being\nmore delicate than a 30 foot log. The Receiver operated consistently\nand is still functioning admirably over in the jungles now. Without the\ndependability and environmental acceptability of this unit, I would\nnot have been able to complete 20 survey sites in 90 days. It was a","284\nfast-paced operation and the Receiver was in use at all times excluding\ntransportation time.\nThe Receiver, on occasions, was more than 30 hours without an ex-\nternal battery and I never lost accurate time or oscillator stability. The\ncontract in Borneo was not intended to be a field survival equipment\ntest but your Receiver functioned perfectly under those conditions. The\ncompactness, easy handling and lightweight of the land antenna was\nespecially appreciated when forced to climb trees over a hundred feet\nhigh to gain horizontal control in the dense jungle. The pass selector\noption is extremely valuable in lessening power consumption when you\nhave to carry or float everything through the jungle. Not one hour of\ndowntime due to the failure of the receiver itself to function properly.\nAs for the processing system, again there was no downtime due to\nfailures. \"\nIf one looks beyond the complimentary nature of this quotation, a very\nspecific jungle application specification is presented. The basics of\nthis specification can be summarized as follows:\n(a)\nShall float in the water without seepage.\n(b)\nShall withstand dropping on hard surface.\n(c)\nShall perform to specification in high ambient temperatures, at\nleast +55°C\n(d)\nMust be of sealed construction such that extended operation in\nhigh humidity and in driving rain will not deteriorate performance.\n(e)\nInternal batteries must maintain the oscillator and clock for\nperiods of 30 hours or more.\n(f)\nThe antenna shall be compact, easily handled, and light in weight.\n(g)\nPower consumption must be an absolute minimum.\n(h)\nThe antenna-to-receiver cable shall be longer than 100 ft.\nFlorida Field Test\nAn early field experience by the writer was, in part, responsible for\nsome of the features which proved so valuable to the user in the above-\nquoted experience. This experience involved the field evaluation of\nfour JMR-1 units in August of 1974 and was performed in the Melbourne,\nFlorida area in conjunction with DBA Systems, Inc. The evaluation has\nbeen previously reported by both DBA and JMR. During the period of\nthis test there was at least one rainstorm each day and on some days\nthere were several. Between rains during daylight hours the sun shone\nwith intense brilliance. One of the four JMR-1 units proved to be not\nrainproof and failed to perform after the first few days. Following\nthis experience, improved sealants were found and greater amounts of\ndessicant were installed inside the sealed case to absorb any seepage\nwhich might occur.","285\nAlso during the Florida field evaluation the value of protective moun-\nting for the reference oscillator was proven. The JMR-1 units were\ntransported from site-to-site in the rear of a pickup truck on the\nsteel bed without padding or transit case protection. And the roads\nand fields were not exactly smooth. Even though this test was passed\nwithout failure, it is now recommended that a padded transit case be\nused in such instances.\nAt the time of the Florida operation the JMR- receiver was being\noperated with a 25-foot coaxial cable between the antenna and the re-\nceiver. This did not allow adequate separation between the antenna and\nthe metallic supporting structure of the tents that were sometimes used,\nthus causing gaps in the data record due to signal reflections. The\nrequirement for a longer cable has been borne out in a number of sub-\nsequent application requirements, including the tree-top scene pre-\nviously quoted. A source of repeated misunderstandings is associated\nwith positions given offset from the desired point. In most cases a\n200-foot coaxial cable length will eliminate the need for offset.\nHence, the standard length now used is 200 feet, with the attendant\nproblem of coiling the cable for transporting. Even though using small\nRG-223/U coax, a 200-foot length creates a storage and weight pro-\nblem which was completely avoided with the 25 foot length. Further,\nexperiences by Shell Canada during operation in -40° C weather have\nshown that the RG-223/U outer covering cannot withstand normally-\nencountered field handling and bending at these low temperatures.\nMore acceptable performance has been achieved using a wrapped,\nteflon fiberglass covered coaxial cable.\nAutomatic Unattended Operation - Project POGO\nAnother very important feature of this type of field equipment is the\ncapability of unattended operation. If an operator is required on-site\nthen at least two people for each survey crew must be logistically\nsupported full time in the field. Considering the attitude of today's\nlabor market, it might be necessary to continuously support 3 or 4\noperators per crew, or at least to transport a relief crew every few\ndays. When one considers the simultaneous operation at multiple\nsites for accomplishing high-precision network ties in translocation\noperation, the cost of personnel and their support logistics multiplies\nto an intolerable level.\nThe ideal answer, of course, is a low power, highly portable, fully\nautomatic field unit. Preferrably one which can be set up in a very\nshort time after arrival on site. With such equipment characteristics,\none could ideally load the instruments and batteries necessary for 4","286\nor 5 sites into one small helicopter, together with the pilot and one\noperator, and thusly set up all sites within 1/2 days time. Considering\nthat 25 to 30 simultaneous passes should provide adequate data,\nthe routine could be repeated after about 48 hours of data-gathering\ntime, only on this second trip the equipments are picked up and drop-\nped off at new sites. Or, if more data is desired, the second trip in-\nvolves checking the equipment and picking up the first two days'\nrecorded data. In some such operations it may not even be necessary\nto retain the services of the one helicopter on a full-time basis.\nSuch a mode of operation has proven to be feasible when using the JMR\nSystem. Its Pass Selector can be pre-programmed for up to 48 pass\nturn-on-times before leaving for the site. Its seven-watt average power\nconsumption requires only one 23 pound, 30 A-H gel-cell battery per\nsite (over 50 hours and over 30 passes). One cassette will record the\ndata from about 40 passes without operator attention. Details of these\nand other features are presented in a later section of this paper.\nJMR's Project POGO, the results of which are presented in a paper by\nRon Brunell of JMR, is an example of unattended operation and field\nset-up by unskilled operators. Several weeks of operation on-site were\ninvolved to gather sufficient data for full evaluation of \"Precise Ephe-\nmeris\" results against \"Broadcast Ephemeris\" translocation. The\nfield work for this highly successful project was performed primarily\nby a completely non-technical female administrative assistant after a\nfew hours instruction, including programming of the Pass Selector,\nand after one trip to the field accompanied by a skilled operator.\nProcessing in the Field - An Urban Operation\nA computer system for processing of the field data is an important\nconsideration in planning and performing a survey operation. Another\nuser case history illustrates one particular mode of processing the\ndata in the field. The purpose of this operation, carried out in and near\na large metropolitan area by one operator, was to establish control\nfor a series of SHORAN, HI-FIX and ACCUFIX stations. In spite of\ncustomer suggestions to the contrary, the operator processed the\ndata at his field base camp as it became available. Due to the location\nof the survey, his field base camp was in a hotel or motel room. The\nrequirements which he placed on the equipment for this operation can\nbe summarized as follows:\n(a)\nThe total equipment complement must be capable of being trans-\nported in one taxi or hire car.\n(b)\nBoth the field and the processing equipment must be easily and\nquickly set up to facilitate the many moves required.","287\n(c)\nThe processing equipment should be quiet in operation in order\nto not disturb the sleep of the operator and the other guests\n(in this case through rice paper walls).\n(d)\nBoth the field equipment and the processing equipment must be\nautomatic to allow one operator to perform all functions and\nstill obtain adequate sleep.\n(e)\nThe equipment must be waterproof to allow transporting and\nset-up in the rain and mud.\n(f)\nThe final answer for each site must be automatically provided\nas a processor output to avoid human computation error which\nmight occur under the stress of such a one-man operation.\nThe equipment which was used to meet the requirements of this opera-\ntion was as follows.\n(1)\nA JMR-1 Doppler Survey Set for field data gathering\n(2)\nA JMR-1CR Cassette Reader for transferring the data from the\ncassettes to the computer and for computer program loading.\n(3)\nA Hewlett -Packard 2105 computer for processing the data\n(4)\nA Texas Instruments Silent 700 as an I/O device for the computer.\nBase camp set-up met the \"quick and easy\" requirement (b), consisting\nof connecting one cable between the Reader and the computer and one\ncable between the computer and the Silent 700. In regard to field\nequipment set-up, he relates one instance in which he saved a full\nhalf day of operating time by setting up on site using a flashlight after\nlate arrival. No oscillator warm-up time was required because of\nthe JMR-1 internal standby battery. In compliance with requirement\n(c) operation of the base camp equipment is essentially silent with\nthe Silent 700 completely eliminating the noise of the traditional tele-\ntypewriter. The waterproof nature of the equipment, requirement (e)\nwas graphically demonstrated in at least one instance when it arrived\nduring a rainstorm in an open truck. The JMR-1 was later dashed\nwith a pail of water to remove the mud which accumulated from the\nfield operation.\nBy the end of the operation the customer was fully convinced of both\nthe feasibility and the advantages of processing the data in the field.\nSeveral days of data processing time at the end of the field operation\nwould have otherwise been required. Instead, the processing was\naccomplished during time periods when the operator was waiting for\nfield data to be recorded or when he was sleeping. And for meeting\nrequirement (f) the printout available to the customer was the cumu-\nlative mean of latitude, longitude and height of each site together with","288\na scatter plot and a listing of the exact latitude and longitude for each\npass plotted.\nLate last year the writer assisted in the start-up of an operation in\nthe Chapare Area of Bolivia. The data was processed in a hotel room\nin Cochabamba using a set-up similar to the previous example. How-\never, a teletypewriter was used as the I/O for the computer, requiring\nthe processing to be accomplished in a room isolated from other guests.\nA hi-speed tape reader was available for program loading but was not\nrequired as the program was loaded via the Cassette Reader. A ROM\ncassette loader program is used in the HP-2105, requiring entry of\nonly one instruction with the computer panel switch register to accom-\nplish program loading.\nArctic Operation\nJMR equipment has been successfully operated in both the Arctic and\nthe Antarctic areas. Some excerpts from a user's report on an opera-\ntion in Northern Canada provide an insight into some cold weather\nproblems, particularly reduction in battery capacity. The quoted\nexcerpts follow.\n\"Since the project was to be done in the coldest part of winter and in\na climate with abundant snowfalls, several factors had to be considered\nbefore entering the field. The doppler receivers to be used for this\njob had been tested at -40°C temperatures and were considered to be\nweather-proof, however, the power supply required for the receivers\n(a 12 volt d. C. lead acid battery system) was no way adequate to pro-\nduce the required power at sub-zero temperatures. Most of the sites,\nwould be moved and set up using a Bell 206B helicopter, thus placing\nsome restrictions on space and weight.\nBearing all this in mind, it was decided that each site would consist\nof a small propane heater with a 20 lb. bottle for heat, as well as the\nJMR doppler satellite receiver. The tents had to be easily assembled,\nlight, compact and fairly weather resistant while the heaters had to\nhave no fire danger, yet provide adequate heat, as well as being small\nand simple to operate. After much searching these requirements were\nsatisfied with the purchase of 6' Thermos Pop tents and variable\nBTU Flameless propane heaters.\nThe tents proved to be extremely portable and quick to assemble in\nthe cold weather while the propane heaters provided sufficient heat to\nkeep the temperature inside the tents well above freezing. Even the\nflameless aspect of the heater provided very positive results as on\nthree occasions flammable materials were inadvertently knocked\nagainst the heater for periods of up to 24 hours. The heater scorched","289\nthe materials to the point of destruction but no flames occurred.\nConsidering the above facts it becomes obvious that doppler satellite\nsystems can be a most efficient method of survey, not only in the\nsummer, but year around. It was also demonstrated that one heli-\ncopter can service as many as seven sites with the potential to do\nseveral more if the conditions are favorable. 11\nDetails of JMR Hardware Features\nThe foregoing discussion has established basic requirements of users\nin some specific applications of the system. A more detailed presen-\ntation of JMR equipment features may suggest additional applications\nand alternate operating procedures.\nHardware features will be discussed in several categories, as follows:\n(1) The data which is recorded\n(2) The data recording medium\n(3) The Reference Oscillator\n(4) Automatic Operation\n(5) Redundancy and Operator Corrective Action Features\n(6) On-site data checking\n(7) Logistics requirements\nThe Data Which is Recorded\nIt can be said that the only data which need be recorded on site is the\nposition of the point being measured. In a small number of applica-\ntions this is feasible and practical. However, computation of the\nposition on site is not possible when using the precise ephemeris.\nAnd when data is received at two or more sites simultaneously for\ntranslocation processing it is not practical to process on-site. Further,\nprocessing a final position on-site eliminates all options for re-pro-\ncessing to allow cross-checks and adjustments. Such an approach in\nfact defeats the major purpose which it can serve; that of testing the\nadequacy of the data which is available. If the computation proves to\nbe unacceptable, there is no recourse except to repeat the survey.\nFor any critical operation where results must be traceable and sub-\nject to analysis a record of the raw data is required as a backup if not\nfor use in final processing.\nFor these reasons the JMR-1 instrument was designed to record the\nsatellite signal data as received, prior to any processing whatsoever.\nRecognizing that many projects may require re-processing of the\ndata in a follow-on or expansion phase of the project. and that improved\nprocessing techniques are continually being developed, a means was","290\ndeveloped by which intricate details relating to the data could be\nconveniently recorded along with the basically required information.\nFigure 1, Item 3, shows the information which is recorded with each\n4. 6 second (approx.) doppler count. The first nine digits constitute\nthe broadcast ephemeris message word. The next 6 digits define, to\nthe nearest microsecond, the time of occurrence of the received satel-\nlite data bit prior to the start of the doppler interval. Then two digits\nare recorded which define, to the nearest microsecond, the start of\nthe doppler count. The six-digit refraction corrected doppler count is\nthen recorded, followed by two digits which are a measure of the\nminimum received signal strength during the doppler interval for the\n150MHz and the 400MHz carriers, respectively. Additionally, as shown\nin Item 2, the real-time clock (day, hour, minute, second and micro-\nsecond) is recorded at the occurrence of the received satellite time\nmark designating each two-minute interval of the pass. The operator\nmay enter as many digits as desired onto the tape at any time that\nsatellite data is not being recorded. These entries may serve as tape\nheaders, trailers or interpass data identifying the site, the receiver,\nmeteorological data, or any other information desired. A typical tape\nheader entry is presented by Item 1 Figure 1.\nThe doppler data may be processed using the basic 4.6 second inter-\nvals or combined into multiples of 4. 6 seconds, making it compatible\nwith most software systems in use today. Also compatibility is en-\nhanced by terminating the last interval of each two-minute period at\nthe two-minute mark. Measurement of each doppler interval period to\nthe nearest micro-second allows a high degree of resolution in the\ntiming of the doppler interval and in determining its average frequency.\nThe analog refraction correction minimizes quantization error. The\nsignal strength tags on each doppler count have proven to be very\nvaluable in data editing and weighting.\nThe Data Recording Medium\nPractical considerations dictate the use of either paper tape or magnetic\ntape for recording the data in the field. Paper tape has long been used\nin the laboratory as a standard medium for digital data storage and\nfor entry of data into minicomputers. However, current technology\nis moving rapidly toward replacement of paper tape peripheral equip-\nment with cassette equivalents. Magnetic tape cassettes offer distinct\nadvantages of compact data storage, low power operation, and auto-\nmatic data handling. The JMR-1 unit utilizes a built-in, fully auto-\nmatic cassette transport for recording the satellite data. Special\ndesign techniques allow highly reliable operation of cassette recording\nat temperatures ranging from -40°C to +55°C and in all-weather envi-\nronments. The data from about 40 satellite passes is recorded on one\ncassette requiring about 0. 25w recording power on the average. The","291\nJMR - DATA CHARACTERISTICS\nRECORDED DATA (shown as a teletypewriter printout)\n1. Tape Header (entered by operator at beginning and end of tape.\n(4) Site number\nOperator estimates\n(3) Receiver delay\n(5) Last digit\n(6) Lat. (deg.) EE\nin 10's of usec.\nof year\n(7) Long. (deg. )\n(2) Set serial no.\n(8) Elev. (m X 10-2)\n(1) Leading zeros\n2. Pass Header (recorded automatically at beginning of each pass; items (2),\n(3), (4) & (5) are operator entries)\n(5) Rel. humidity, %\n(6) Day\n(7) GMT, hr & min\n(4) Pressure, mb\n(8) Clock seconds\n(3) Temp., oc\n(9) Clock usec.\n+=0; -=1\n(10)Fract. count, usec.\n(2) Comment\n(11)Initial dopp. xfer.\n(1) Leading zeros\n(12)Signal status\n00000000000123456789;007092663;1 167153559; 995082; 29; 000001;33;;\n3. Line 1 Data (recorded during Line 3)\n(2) Clock usec.\n(3) Fractional\n(4) Doppler count\ncount, usec.\n(234 bits)\n(1) Message word\n(5) Signal status\n013680275;601020;36;141864;33;\nFIGURE 1","292\ndata is simultaneously recorded on both tracks of the tape to provide\nrecording redundancy.\nThe cassette-recorded data may be read back and/or duplicated on a\nblank cassette using a battery-operated cassette unit which is also\ndesigned for operation in the full range of field environments. This\nsame cassette unit is used under program control to automatically\nread the data into the computer at a rate of 2500 bits per second\nfor processing. Processing in a large computer may require data\nentry from 9-track magnetic tape. Equipment is available to allow\nrapid transfer of the data from cassette to 9-track tape.\nThe Reference Oscillator\nOne of the highest precision components of the field unit is the re-\nference oscillator. Early satellite receiving equipment utilized bulky\nand power-hungry crystal-referenced frequency standards. Current\ntechnology has allowed the development of a 5MHz frequency standard\nfor the JMR-1 which requires only about 1 watt of power and operates\ndirectly from a 12-volt battery. Its short-term stability is better\n2 10 -12 for 1 second sampling periods. The oscillator is\nthan\nmaintained by the internal JMR- 1 rechargeable battery for over 30\nhours while being transported. Thus no time need be allotted for\noscillator stabilization and the receiver clock need never be reset\nduring an operation.\nA unique feature of the JMR-1 data record is that it allows a field\ncheck on the reference oscillator stability to about 2 X 10-11 using\nthe 4. 6 second sampling periods. This same technique is mechanized\nin the JMR minicomputer program. The minicomputer fix computa-\ntion printout also provides an estimate of local oscillator frequency\nfor each fix solution using the broadcast satellite oscillator offset\nfrequency. A plot of local oscillator long-term frequency drift using\nthese estimates can be further refined by using the frequency offsets\nwhich are published weekly by the U. S. Naval Observatory. Figure\n2 shows plots of local oscillator long term drift.\nBased on the best curve drawn through the data points, the oscillator\nin S/N 76112 appears to exhibit extremely good long-term stability\nwithin a short time after a cold start. The scatter of the data points\nis at least partly due to the uncertainty which is present in the solu-\ntion for frequency difference as one of the unknowns in the computa-\ntion. The initial portion of the warm-up curve would indicate that,\nfor high precision results, this oscillator should be allowed to warm\nup for about 12 hours. However, the overall change in oscillator\nfrequency during the time from 2 hours after start-up to 12 hours","E62","294\nafter start up is only one part in 109\nThe lower set of curves, for S/N 76118 after long warm-up, is a\ncomparison of use of broadcast predictions of satellite oscillator\noffset and use of offsets reported by the U. S. Naval Observatory.\nThe striking similarity of the curves can be noted except for the\njump between days 245 and 247, apparently due to the 1 X 10-9\nresolution in the prediction value.\nAutomatic Operation\nThere are a number of operations which must occur in obtaining\na record of satellite passes after setting up the field equipment on\nsite. A typical list is as follows:\nSet the correct time into the local clock (or record it on the tape).\n(a)\nSelect the next pass to be tracked.\n(b)\nApply power to the recording systems.\n(c)\nTune to the satellite signal rise frequency and effect signal\n(e)\nacquisition and track for both the 150 & 400 MHz receiver\nchannels.\nIn case of signal loss on either channel, switch to slave tracking\n(f)\nagainst the other channel until it is possible to reacquire.\nMaintain the frequency tuning control in the vicinity of the signal\n(g)\nfrequency. For signal loss on both channels, re-initiate the\nsearch and acquisition routine.\nObserve that end of pass has occurred, remove power from the\n(h)\nrecording system, and switch the receiver to standby.\nRepeat the entire sequence for each succeeding pass.\n(i)\nThese operations have all been automated in the JMR-1. The clock\nis automatically set by the satellite signal time mark and recorded\non the tape. The JMR-1 pass selector memory allows pre-programmed\nturn-on of up to 48 passes. All search, acquisition, track, and cross-\nchannel slaving are fully automatic. In fact, the system is so auto-\nmatic that two operators for National Mapping in Australia, suffering\nfrom extreme boredom while operating in the \"outback\", suggested we\nincorporate electronic games into the unit. It has become standard\noperating procedure to program the pass selector at base and send\na driver out to set up the units rather than a trained operator or\nsurveyor.","295\nOn the other hand, the design allows a trained operator to override\nthe automatic functions almost completely and take control if he so\ndesires. He can set the clock, switch the power, tune either channel,\nreset the progressive sweep circuit, disable the pass selector, enter\ndata on the tape between passes, and monitor 24 different data and\noperating status functions.\nOn-Site Data Checking\nIt is generally accepted that it is desirable to occasionally check the\nperformance of electronic equipment during field operations. To be of\nvalue such checks must be both qualitative and quantitative. There is\nalmost no function of the JMR-1 which cannot be quantitavely checked\nin the field. Whenever desired, the operator can utilize the panel-\nmounted digital display to monitor any portion of the data which is\nbeing recorded. For example, he can display each message word, one\neach 4. 6 seconds, and can freeze any desired word on the display for\nmore lengthy analysis. From these words he can completely verify\nthe correctness of local clock time, identify the satellite being tracked,\nand observe the time of last injection as well as verifying correct\ndecoding of the message bits. In the same manner he can monitor the\n4. 6 second doppler counts and signal strength digits or the micro-\nseconds readings. He can observe the day, hour, minute and second\nreading of the internal clock and can freeze the display to time an\nobserved event. He can also monitor the tuned offset frequency of\neither channel.\nThe operator has the option of observing any or all of the cassette-\nrecorded data using a battery-operated field-worthy cassette reader\nand can perform quantitative, controlled tests on receiver sensitivity\nmessage detection threshold, cross-slaving doppler count accuracy,\nsignal strength digit calibration, and even oscillator short-term sta-\nbility using a battery-operated, field-worthy satellite signal simulator\nand a second JMR-1. Ofcourse the ultimate aid to on-site data check-\ning, particularly for the inexperienced operator, is computation of a\nposition fix for each satellite pass. This ultimate aid has now been\nmade feasible and practical by the JMR-1MP field microprocessor,\ndescribed in Section 5. 1.\nLogistic Requirements\nOne of the major deterrents to widespread application of the satellite-\ndoppler technique to geodesy and surveying has been the high logistics\ncosts. Until recently, most available field units had been designed\nfor shipboard use and later adapted to geodesy and survey. Thus the\nequipment has been heavy and power hungry, resulting in extreme","296\nlogistics costs, particularly where helicopter transportation is\nrequired. Reduction in power requirement was high on the priority\nlist in the design of the JMR-1. The result is a field unit which is\nlightweight enough for a one-man backpack and which can provide\na precision survey of a site on the power from one small 12 volt\nbattery. The average power consumption of the unit is about 7 watts\nwhile recording 15 passes per day.\nFigure 3 presents the voltage rundown curve for a 30 A-H gel-cell\nbattery operating a JMR- for 60 hours during which the data from 31\npasses was recorded. The ambient.temperature during this test was\nabout +22°C. This low power drain is achieved by use of a programmed\npass selector which holds the receiver in standby except when a pre-\nselected satellite pass is to be tracked, by turning recorder power on\nonly when data is to be recorded (duty cycle of about 0. 04), and through\nuse of low power CMOS integrated circuits.","70\nA D A A A A D A A ADDAD DADAA A AAA\n60\nEAGLE-PICTHER BATTERY NO. CF12V30\nOPERATING JMR-1 ON PASS SELECTOR\nFOR 30 A-H SEALED BATTERY\nBATTERY TERMINAL VOLTAGE\n50\nFIGURE 3\nTime of occurrence of each pass\n40\nOPERATING TIME, hours\n30\n20\nD D D ADDA\n10\nD\n0\n9\n13\n12\n10\n11\nd-p","298\nNew Products\nSeveral recently-developed items by JMR have expanded the applica-\ntion and effectiveness of the JMR System. Developments such as\nthese will continue to respond to the greatest possible extent to\nrequirements feed-back from the user community. The characteristics\nof three of these new products are briefly discussed in the following.\nA Field-Worthy Processor\nMicroprocessor technology has now advanced to a point which permits\nthe design and production of a highly reliable, low power, all envi-\nronment field processor. Thus it is now possible to satisfy the demand\nfor processing fixes on-site in addition to recording the raw data. A\nfield-worthy processor for this purpose is now available from JMR.\nThis new unit, the JMR-1MP Microprocessor, operates as an\naccessory to the standard JMR-1 Doppler Survey Set. It is an all-\nenvironment battery-operated, fixed program data processor. Figure\n4 is a picture of the JMR-1 and the Microprocessor, shown set up\nfor field operation. The entire system can operate automatically for\nmore than 48 hours, tracking 25 passes, on the energy from the one\nautomobile battery shown in the picture (about 65 A-H). The Micro-\nprocessor unit is designed to withstand the rigors of on-site operation\nwith the JMR-1. Flexibility in application is provided through the use\nof interchangeable module-pod peripheral units which mount on top\nof the basic processor.\nJMR views its microprocessor as an extremely valuable and cost\neffective addition to the field equipment for use (1) as a check on the\nquality of the data being recorded, (2) as an indicator of when a\nsufficient number of \"acceptable\" passes have been recorded for\npost-processing to the desired accuracy, and (3) in applications\nrequiring a quick answer on a few passes.\nIt has been demonstrated that the JMR microprocessor solutions com-\npare directly in accuracy with the JMR SP-7 Hewlett Packard 2100\nsolutions on a pass-for-pass basis.\nAn All-Environment Cassette Reader\nThe JMR-1CRR is a ruggedized cassette tape reader which is designed\nto read JMR-1 Receiver data tapes. This new design encompass all\nof the operational features of the previously offered readers from\nJMR. These include:\nDisplay: Ten-digit numeric readout for instant inspection of data\nrecords.","299\nJMR-1MP\nFIGURE 4. JMR-1 with Microprocessor in Field Set-up.","300\nPrinter Output: Built-in teletype data formatter and clock and\n20 ma. current-loop driver for hard-copy printout, external display\nor line driving. Optional RS-232 output available.\nAutomatic Data Transfer: With the appropriate interface, cassette\ndata can be transferred to any one of several minicomputers for\ndirect processing or to multi-track tape for later processing on\nlarge computers. Interfaces currently available include HP, Data\nGeneral, and Digital Equipment Corp. mini computers, and Pertec\n9 -track machines.\nAdditionally the JMR-1CRR offers new features not found on previous\nreaders. These include:\n1. Environmental Ruggedness - Sealed construction and high\nreliability components allow the reader to be used in harsh\nenvironments. Inclement weather and temperature extremes\nof -25°C to +55°C will not degrade performance.\n2. Physical Ruggedness - All internal modules and cards are\nrigidly secured, (pressure loaded when necessary) to the unit\nhousing. The unit will not be damaged by normal transportation\nbumps and shocks. Units are supplied in a padded transit case\naffording additional protection.\n3. Portability - The JMR-1CRR weighs only 15 lbs. (6. 8kg).\nIt operates from a 12 volt battery or supply. Easily handled,\nit is about the size of a small tool box.\n4. Flexibility - The JMR- - 1 CRR is ideal for use in the field,\nfor making instant spot checks of data being gathered at remote\nsites, or for processing data at a remote base camp. It is\neasily interfaced to computers or peripherals in either the field\nor at home base. It can be used in conjunction with any other\nJMR-1 CRR to duplicate data tapes for insurance against acci-\ndental data loss. The Ruggedized Reader comes as a table top\nunit with integral carrying handle. A rack-mounting bracket\nkit is available if permanent placement is desired. There are\nno \"custom\" JMR-1CRR's. All Ruggedized Readers are iden-\ntical and can be field-configured for any reader use presently\nspecified.\nTranslocation Solutions in the Field\nThe JMR SP-7 Program is a very powerful and versatile tool for the\nsurveyor. The program is written for the Hewlett Packard 2100 or\n21) MX computer with 16K of memory. This program offers tremedous","301\nflexibility while maintaining a simplicity in operation. This is\naccomplished by an extensive command structure, which may be\nentered through a keyboard device or the JMR-1 panel, with standard\ndefaults enabling the user to involve himself to any desired degree\nwith the data processing function. The operator involvement in the\nprocessing can be limited to choice of mode and normally required\ninitial data, or the operator may intervene with choices to change\nthe editing criteria and type of output.\nBecause of the small size of the Hewlett Packard 2105 computer\n(5 inch panel) and the simplicity of the required accessories its user\ncan easily visualize the ease and effectiveness of taking it along on a\nsurvey mission. The input device for loading programs and for satel-\nlite data entry is the small cassette reader described in Section 5. 2.\nThe output device is the \"attache case\" Silent 700 (734KSR). That's\nall that is required for 3-dimensional translocation. Two-station\ntranslocation accuracies of the order of 2 meters in each coordinate\nhave been demonstrated by direct comparison with precise ephemeris\nsolutions and with JMR-developed FORTRAN translocation programs\noperating in medium-scale laboratory computers.\nConclusion & Summary\nSatellite Doppler Positioning has now become an indispensible tool\nfor the geodesist and the surveyor, The accuracy and consistency of\nsolutions utilizing the predicted satellite ephemeris information has\nimproved dramatically over the past few years. Field instrumentation\nhas kept pace with satellite system improvements and is now capable\nof supporting major control densification projects at realistic logistic\nand manpower costs. This advanced instrumentation has incited a\ntrend toward multiple simultaneous site instrumentation, further\nreducing the cost and compressing the time required for such major\nprojects.\nPresent-day field instrumentation and data processing equipment\noperation is automatic and easy to use. The small surveyor no longer\nneeds to be apprehensive about his ability to achieve competetive\nresults from the system. He does not need an electronics degree or\na supporting staff of multi-disciplined technicians. A few days of\napplication training and field experience and he is ready for productive\nand profitable operation.\nRecent advances in microprocessor technology have heralded the\ndevelopment of an all-environment, battery-operated, fixed program\ndata processor which has introduced a new dimension into the applica-\ntion potential of the system. Todays development of application-\noriented instrumentation, promoting an ever-broadening user commu-\nnity, is setting the pattern for the future of Satellite Doppler Positioning.","302","303\nSTANDARDIZATION OF DOPPLER POINT POSITIONING RESULTS\nJohn D. Love\nDefense Mapping Agency Topographic Center\n6500 Brookes Lane\nWashington, D.C. 20315\nDepartment of Geodesy and Surveys\nAbstract\nThe relative ease of data acquisition made possible with the portable\nsatellite equipment used for Doppler point positioning, has resulted in\nthe establishment of over 1,000 control points and related data by U.S.\nGovernment agencies. The continued increase in the use of portable tracking\nequipment by both government and the private sector is anticipated. This\npaper is concerned with the standardization of the results of Doppler point\npositioning in order that interchange of data among various data acquisition\nelements may be more easily facilitated where specific exchange agreements\nare made.","304\nIntroduction\nThe standardization of field specifications for data acquisition does not\nautomatically carry over into the documentation of the results obtained\nfrom field surveys--surveys which are so meticulously observed and computed.\nAll too often, the effort of a conscientious field party and the reduced\nresults so laboriously \"cranked-out\" in the office are misinterpreted by a\nuser because of poor documentation. Worse yet, and not infrequently, the\nresults may be lost to all but the originator of the survey. These general-\nizations on the haphazardness of maintaining survey results could possibly\nbe applied to the whole of surveying, but even more so, to Doppler Geodetic\nPoint Positioning (DGPP).\nThe relative ease for extending geodetic control made possible by DGPP\nmay be responsible for the omission of uniform documentation or the some-\ntimes total lack of documentation. Compared to the older established\nconventional methods of extending geodetic control, the Doppler satellite\nsurveys are usually accomplished with less expense and much less logistic\nsupport requirements. Obviously, the greater the expenditures of resources\nrequired to maintain large surveying operations in the field for long periods\nof time, automatically increases the concern that the results be made avail-\nable in a rigidly prescribed manner for all posterity. Also, the non-\nclassical geodetic oriented technicians and managers who are primarily\nresponsible for the recent advancements made in geodesy may not be versed\nin the methodology of geodesy, especially in the tedious procedure of docu-\nmenting survey results; henceforth, that less glamorous phase of geodesy\nis often times slighted.\nBackground\nThe Defense Mapping Agency Topographic Center (DMATC), then the Army Map\nService, was instrumental in preparing standards for the documentation\nof the results of ground surveys which were accomplished in support of\nthe earlier National Geodetic Satellite Program for the Department of\nDefense (DoD). The documentation now required by DMATC for Doppler satel-\nlite surveys is suggested for universal adoption by other organizations.\nThe same results should be documented in such a manner that results are\nmeaningful and that users do not apply the results improperly.\nDMATC is the DoD central point of contact within the Defense Mapping Agency\n(DMA) for all geodetic satellite results. DMATC carries out a continuing\ndata collection effort in order to provide current ground survey data and\nsatellite derived positions from DGPP programs accomplished by U.S. Agencies\n(both DoD and non-DoD) and foreign agencies. To help fulfill this obliga-\ntion, a listing of holdings which are available from DMATC is disseminated\nquarterly within DoD and to cooperating organizations. A sample of the\nlisting is illustrated in Figure 1, and Figure 2 is an explanation of this\nlisting. Please note that data are furnished only to authorized recipients.\nRestrictions imposed on the distribution of data by the host country or\nby other sources are carefully honored.","305\n(0ICDKEPLTSAHIO\nDATA AVAILABLE\nPAGE NO. 12\nOICOKEPL S H\nOICOKE L S H\nOICDKEPL S H\nOICO EPL S H\n0 CD PL S H\n0 C KEPL S H\n0 COK PL S H\nOICO EPL S H\n0 COKEPL S H\n0 CD EPL S H\n0 COKEPL S H\nOICOKEPL S H\nOICOKE L S H\n01CDKEPL S H\nOICOKEPL S H\n15 JUL 76\n0\nCOUNTRY OR STATE\nWI-DOMINICAN R.\nWI-LEEWARD IS.\nWI-LEEWARD IS.\nWI-VIRGIN IS.\nWI-VIRGIN IS.\nWI-TURKS IS.\nDENMARK\nENGLAND\nENGLAND\nENGLAND\nGERMANY\nGERMANY\nGERMANY\nGERMANY\nSample Page of DMATC List of Holdings for Surveys\nGERMANY\nGERMANY\nCYPRUS\nCYPRUS\nCYPRUS\nCYPRUS\nMade with Portable Doppler Tracking Equipment\nSURVEYS WITH PORTABLE DOPPLER TRACKING EQUIPMENT\nCONTINENT OR OCEAN\nDATA AVAILABLE AT SATELLITE RECORDS DESK\nATLANTIC OCEAN\nATLANTIC OCEAN\nATLANTIC OCEAN\nATLANTIC OCEAN\nATLANTIC OCEAN\nATLANTIC OCEAN\nEUROPE\nEUROPE\nEUROPE\nEUROPE\nEUROPE\nEUROPE\nEUROPE\nEUROPE\nEUROPE\nEUROPE\nEUROPE\nEUROPE\nEUROPE\nEUROPE\n*SEE THE FOREWORD OF THIS LISTING FOR EXPLANATION OF CODE.\nFIG. 1\nLOCATION\nDHEKELIA (SBA)\nEPISKOPI (SBA)\nHANDGATE FARM\nHERSTMONCEUX\nANTIGUA IS.\nANEGADA IS.\nN 53 35 E 8 33 BREMERHAVEN\nGRAND TURK\nCOPENHAGEN\nFYLINGDALE\nSAN PEDRO\nN 49 40 E 11 57 GRAFENWOHR\nST. CROIX\nYIALOUSSA\nANGUILLA\nDUELMEN\nN 48 23 E 10 1 NEU-ELM\n30144 N 34 43 E 32 28 PAPHOS\nBERLIN\nBERLIN\n4\n48\nN 21 26 W 71 9\nN 35 0 E 33 44\nN 34 41 E 32 51\n33 48\n30\n40\n58\n0 21\nLONG.\n7 18\n63\n61\n12\n0\n1\nW\nW\nE\nE\nw\nW\nE\nE\n13\n9\n8\n44\nN 54 21\n9\nN 50 52\nLAT.\nN 51 49\n18\n17\n35\n55\nN 52\nN\nN\nN\nN\nSTATION\nNUMBER\n20393\n10007\n10005\n10199\n20485\n20484\n30130\n30142\n30143\n30036\n30438\n30230\n30231\n30670\n30645\n10183\n10186\n10193\n10196","306\nA service of the Satellite Records Desk is the maintenance and the\ndissemination to appropriate DoD users and authorized non-DoD organiza-\ntions of a periodic listing of these data as they become available. Data\nare obtained from all Components of the Defense Mapping Agency as well as\nother government agencies-beth United States and foreign.\nThe stations are grouped alphabetically according to continent or\nocean and then further arranged by political subdivision. In the column\nfor data available, the letter codes indicate availability as follows:\nReports:\no Satellite Systems Occupation Report\nI Geodetic Information Report\nC Geodetic Summary Card\nDescriptive Material:\nD Description\nK\nSurvey Sketch\nE Station Site Sketch\nP Photoidentified or Photoidentifiable\nCoordinate Data:\nL Position surveyed to local datum\nT Position transformed to local datum from satellite\nderived position; MSL elevation is satellite derived\nunless denoted by \"H\".\nS Satellite derived position and ellipsoid height\nA Astronomic position\nH Elevation surveyed to sea level.\nFIG. 2\nExplanation of Letter Codes, which indicate availability of\nDoppler Satellite Station Data, for DMATC list of holdings\nof Surveys made with portable doppler tracking equipment","307\nInquiries concerning Doppler survey results may be directed to:\nDirector\nDMA Topographic Center\nATTN: DMATC-GS (52300)\n6500 Brookes Lane\nWashington, D.C. 20315\nUniform documentation of DGPP results and related ground surveys allows\nfor more timely dissemination of data, and the recipients of the data\nare assured of its reliability if there are no doubts pertaining to\ndatums, point of reference, survey mark recovery, etc. Guidance for\nthe uniform documentation of the results from DGPP surveys performed by\nDMA Centers and associated organizations is presented in the DMA Tech-\nnical Manual T-3-52320, Doppler Geodetic Point Positioning, Data Docu-\nmentation and Applications. The recording procedures for field observa-\ntions and related field documentation is contained in the DMA Technical\nManual T-2-52220, Field Operations Manual, Doppler Geodetic Point Posi-\ntioning. This paper supplements and emphasizes particular aspects of\nthe two DMA Technical Manuals.\nWithin DoD the Manuals are available from:\nDirector\nDMA Topographic Center\nATTN: DMATC-TS (50260)\n6500 Brookes Lane\nWashington, D. C. 20315\nFor public sales:\nNational Technical Information Service\nDepartment of Commerce\n5285 Point Royal Road\nSpringfield, Virginia 22151\nUsers familiar with the older manuals entitled \"Guidelines for Geodetic\nSatellite Program,\" Editions 1 through 4, which were published by the\npredecessor organizations of DMATC, should note that the two new DMA\nTechnical Manuals replace the \"Guidelines.\" The Guidelines were succes-\nsful in establishing uniformity in the execution of conventional geodetic\nsurveys and the reporting and documentation of occupation information\nfor the earlier National Geodetic Satellite Program--SECOR, BC-4, PC-1000,\nBaker Nunn, and TRANET and VAN (Doppler).\nRequired Documentation\nIn general, documentation material which are required for a single Doppler\nstation established by DMATC include:","308\n- Summary of Satellite-Observed Station card (DMA Form 8290-1-R)\n- Geodetic Information Report\n- Station Occupation Report with photographs of all station markers,\nthe horizon, and the satellite station from the cardinal points about\n50 meters distant.\n- Descriptions of the Doppler station and other survey marks\n- Survey diagrams\n- Photoidentification material\nAn example of the above listed documentation material is presented in\nthe Appendix.\nOf course, the field observations are always part of the permanent records\nfor any survey. The Doppler observations are stored on cataloged magnetic\ntape; the field books and all other field acquired data related to the\nground survey are manually filed and microfilmed. The user is not generally\ninterested in the field records and no attempt is made to standardize note\nkeeping between organizations. The impracticability of standardized note\nkeeping is recognized.\nIn the not too distant future, the documentation material available from\nDMATC will be maintained and serviced from a Data Base Management System\nwith an on-line query and response. In the interim, DMATC is currently\nusing the operating system of the UNIVAC 1108 computer to store and re-\ntrieve positional data from DGPP surveys--both the ground surveyed coor-\ndinates and the Doppler derived coordinates with related data. Narrative\nmaterial such as reports and descriptive material including diagrams are\nmanually maintained. However, station location overlays are now computer\ngenerated at any scale.\nA uniform documentation system now will contribute to a more efficient\nand universally useful data base in the future.\nComments on Documentation\nThe documentation manual, T-3-52320, explains in a step by step process\nthe manner in which DMATC records and documents a station determined by\nsatellite methods as well as ties to local control. The following com-\nments concerning specific items are noted for emphasis. They may be\nelementary or redundant to many, but the omission of any of the data may\ncause the otherwise valid results of the Doppler derived coordinates to\nbe of little practical use.","309\nSummary of Satellite-Observed Station Card\nThe Summary of Satellite-Observed Station card contains the \"end-product\"\nof a DGPP survey. The Summary Card is designed to offer a concise and\ncomprehensive presentation of data for a satellite observed station. Its\nuse reduces the number of data sheets formerly required to document the\nresults for a satellite observed station.\nPresently, the entries on the card are manually (typewriter) inserted.\nUltimately, at DMATC, the card will be computer generated, but in the\ninterim, plans are for the card to be partially computer generated and\nthe remainder typewritten and/or manually inserted. Presently, specific\ndata are key punched directly from the front of the typewritten Summary\nCard.\nAdoption of the identical format of the Summary Card by all organizations\nis certainly desirable so that the data may be efficiently incorporated\ninto DMATC holdings. It is stressed that all organizations which furnish\ntheir results to DMATC thoroughly document them by including all of the\ninformation which appears on the Summary Card. The following details\nconcerning specific entries on the Summary Card are emphasized:\n- DMA and cooperating agencies assign a unique number to Doppler\nstations as they are established. The numbers are assigned by block to\neach organization and are as follows:\nDMA Aerospace Center - 10001 to 19999\nNaval Oceanographic Office - 20001 to 29999\nDMA Topographic Center - 30001 to 39999\n512 Specialist Team Royal Engineers, Great Britain - 30001 to 39999\nDirectorate of Overseas Surveys, Great Britain - 38001 to 38999\nInter American Geodetic Survey - 40000 to 49999 and 70000 to 79999\nNational Geodetic Survey - 50000 to 59999\nBureau of Land Management - 60000 to 69999\nThis numbering system has prevented ambigious station identification. It\nis recommended that all organizations performing DGPP serially assign numbers\nto their Doppler stations.\n- When the Doppler equipment occupies an existing geodetic control\nmark, the name or number of the existing station must be recorded, in\naddition to any new number assigned the station. Abbreviations should","310\nnot be used. The exact stamping that appears on the mark is recorded.\n- The height of the tracking equipment reference point above the\nstation mark is a critical measurement but is often not included with\nthe final station coordinates. Worse yet, the point to which the station\ncoordinates refer is not always noted, whether it be the antenna collec-\ntion point, the survey station mark, or the ground. DMA now references\nall satellite station coordinates to the survey mark which is in keeping\nwith good surveying practice. Results previously furnished by DMATC\nmay be referred to either the survey mark or to the antenna collection\npoint. Hopefully, because of proper documentation, it has been clear\nto all users to which point the coordinates refer.\n- The number of passes used in the data solution is desired to enable\nthe user to estimate the accuracy of the satellite coordinates, especially\nin the instances where accuracy figures are not furnished, or furnished\nbut unclear as to what confidence level they refer.\n- Satellite derived coordinates transformed to local datums should\nalways be identified by the parameter datum transformations (AX, AY, AZ)\nand the date the parameters were derived.\n- Geodetic horizontal control networks will be readjusted as results\nfrom Doppler satellite surveys are incorporated in to them. Therefore,\nthe date of horizontal adjustment to which the ground coordinates are\nreferenced can be critical information.\n- The availability of back-up and additional data related to a satel-\nlite station can be extremely useful. The value of this type of informa-\ntion, such as survey diagrams, station photographs, astronomic coordinates,\netc., may not be apparent at the time the coordinates of a station are\ncomputed, but after the passage of time, this type of knowledge can be\nextremely useful.\nStation Occupation Report\nIn addition to furnishing details of the present station site occupation,\nthe Station Occupation Report provides uniformity in field reporting\ninformation for effective recovery and reoccupation of the station site\nby other survey teams. The availability of a previously completed Station\nOccupation Report to a survey field party operating in the same geographic\narea is invaluable.\nThe following details concerning the Station Occupation Report are noted\nfor emphasis:\n- If photographs of the station marks cannot be obtained, rubbings\nof the station marks should be made.","311\n- The information concerning local geodetic control ties is extremely\nuseful in the office for preparing the documentation for the station.\nIf a geodetic tie to local control was not required at the time of the\nDoppler satellite survey, then a statement to that effect should be noted.\nIt should, however, be mandatory that a tie to geodetic control be made,\nif feasible, in all DGPP projects. The omission of picture point surveys\nshould also be explained in the report.\n- The measurement of the height of the antenna data collection point\nabove the station mark is sometimes omitted or unclear. An annotated\nsketch of the antenna relative to the ground surface and the survey mark\nis extremely useful.\nPhotoidentification Material\nDMATC requires, unless otherwise directed, that all satellite stations\nbe photoidentified or be tied to picture points regardless of the primary\nreason for the Doppler satellite survey. If photography is not available\nto the field parties, picture points will be established and detailed\nvicinity sketches made so that the station may be identified later on\nphotography.\nObjects and features which normally produce good photographic images are\nlisted in the Field Operations Manual, T-2-52220. Application of this\nmaterial by DMATC suggests that the order of preference in the field\nselection of objects, as listed in the manual, be changed to the following:\na. Intersection of centerlines of airfield runways and/or taxiways.\nb. Intersection of centerlines of crossroads.\nC. Centers of dams with approximate distance between abutments.\nd. Centers of bridges with distance from end to end.\ne. Corners of jetties and piers with approximate distance to shoreline.\nf. Intersecting centerlines of streams crossing roads at right angles.\ng. Corners of large isolated buildings.\nh. Isolated trees or large bushes.\ni. Sharp rocky points of land jutting into the water where tides\nwill not effect the position.\nj. Tops of well-defined sharp peaks.\nk. Stream and river junctions.","312\nObject letters j. and k. should not be used except as a last resort or\nthe total lack of items a. through i.\nWhen man-made features are identified, measurements of the objects them-\nselves must be recorded because of the possibility of future construction--\nairfields and piers are continually modified.\nA Station Photoidentification Card, DMATC Form 8350-2, is prepared for\nevery established picture point regardless if the picture point is photo-\nidentified.\nGeodetic Information Report and Descriptions of Survey Marks\nA Geodetic Information Report is prepared for each station or sometimes\ncombined for the project covering the establishment of several similar\nstations. The purpose of the Geodetic Information Report is to list\nbackground factual data not included in other documentation and to de-\nscribe ground survey techniques and instrumentation used to position\nthe station marks or antennas. Station marks should be described ac-\ncording to standard geodetic surveying procedures. Reference marks and\nazimuth marks should be properly established.\nConclusion\nThe importance of concisely recording the details of a geodetic survey\nare obvious, but frequently omitted once the coordinate data from a DGPP\nsurvey are available.\nTo emphasize the amount of Doppler data generated, 283 Doppler stations\nwere made available to DMA during the past 6 months by U.S. Government\nAgencies and the Inter American Geodetic Survey and collaborating coun-\ntries in South America. DMA now holds information for 1,164 Doppler\nPoint Position Stations.\nThe anticipated further widespread use of portable Doppler equipment\nfor all types of surveying and its relative ease of operation almost\nguarantees that the non-geodetic trained technician will be mass producing\npositions of geodetic quality. To enable that these positions be of use\nto the geodetic community, proper documentation is mandatory.","313\nAnnex\nRequired Documentation Material\nFor a Single Doppler Station\nA-1\nSummary of Satellite-Observed Station\nA-2\nStation Description\nA-3\nStation Photoidentification\nA-4\nGeodetic Information Report\nA-5\nStation Occupation Report with attachments\nA-6\nAttachment 1 - Survey diagram\nA-7\nAttachment 2 - Field description (recovery note)\nA-8\nAttachment 3 - Vicinity sketch\nA-9\nAttachment 4 - Photos of station marks\nA-10\nAttachment 5 - Horizon profile photographs\nA-11\nAttachment 6 - Photos of station from cardinal points\nA-12\nAttachment 7 - Additional station recovery information","314\nSUMMARY OF SATELLITE - OBSERVED STATION\nSTATION NAME/LOCAL NUMBER\nLOCATION\nDOPPLER NO.\nANGUILLA RM 3 1975\nANGUILLA, WEST INDIES\n10007\nSTAMPING ON MARK\nANGUILLA RM 3 1975\nAGENCY (CAST IN MARK)\nTYPE OF STATION MARK\nDEFENSE MAPPING AGENCY\nBRONZE DISK\nDOPPLER OBSERVATIONS\nEQUIPMENT/SERIAL NO.\nHEIGHT OF TRACKING EQUIPMENT REFERENCE\nTRACKING EQUIPMENT REFERENCE POINT\nPOINT ABOVE STATION MARK:\nGEOCEIVER DHQ-010\n1.873\nRED BAND ON ANTENNA\nPERIOD OF OCCUPATION\nOBSERVED BY (AGENCY)\nSATELLITE(S) OBSERVED\nDMATC (512 STRE)\n30190 and 30200\n25 OCT - 5 NOV 1975\nSATELLITE-DERIVED COORDINATES\nELLIPSOID\nMINIMUM ELEV.\nPASSES ACCEPTED\nDEGREES OF\nRESIDUAL RMS\nSTATION SET\nGRAVITY MODEL\nANGLE:\nFREEDOM:\n46\n598\n0.19m\nNWL 9D\nNWL 10E\nNWL 8E\n10°\n(Satellite-derived coordinates referred to station mark)\nl\nACCURACY\nh\nN 18° 13' 04.990\nW 63° 03' 54.937\n15.94m\n1. 5m in each\naxis (90%\nX\nY\nZ\n2 745 225.23m\n-5 403 012.75m\n1 981 330.60m\nlinear error)\n(Satellite-derived coordinates of station mark transformed to local datum)\nA\nDATUM\nh\nELLIPSOID\nX\nY\nZ\nAX\nAY\nAZ\nDATE OF TRANSFORMATION\nGROUND SURVEY COORDINATES OF STATION MARK\nA\nDATUM (HORIZONTAL)\nELLIPSOID\nN 18° 13' 02.433\nW 63° 03' 56.401\n1927 NAD\nCLARKE 1866\nSURVEY BY (AGENCY)\nLOCATION OF SURVEY DATA\nDATE OF ADJUSTMENT\nORDER\nDATE\nUNK.\nUNK.\nDMATC (512 STRE)\nNOV 1975\nDMATC\nELLIPSOID HEIGHT (h)\nELEVATION (H)\nDATUM (VERTICAL)\nGEOID HEIGHT (N)\n66.86m\nMSL\n+5m\n72m\nSOURCE OF (N)\nORDER (ELEV.)\nESTABLISHED BY (AGENCY)\nDATE\nVA\nDMATC (512 STRE)\nNOV 1976\nAMS GEOID CHART 1967\nCONNECTION TO LOCAL CONTROL\nGEODETIC ) AZ FROM NORTH\nDISTANCE\nFROM\nTO\n10007\nA 2 EAST BASE\n84° 38' 54.21\n1544.377m\n10007\nA 1 WEST BASE\n125° 15' 21.09\n1405.944m\nOTHER RELATED DATA FOR THIS STATION\nREMARKS\nDATA\nAVAIL.\nLOCATION/REMARKS\nX\nDMATC\nSTATION OCCUPATION REPORT\nX\nGEODETIC INFORMATION REPORT\nDMATC\nSTATION DESCRIPTION\nX\nDMATC\nSURVEY DIAGRAM\nX\nDMATC\nSTATION SITE SKETCH\nX\nDMATC\nPHOTOIDENTIFICATION\nX\nDMATC\nASTRONOMIC COORDINATES\nSTATION PHOTOS\nX\nDMATC\nCHECKED BY/DATE\nCHECKED BY/DATE\nREVISED BY/DATE\nPREPARED BY/DATE\nDMATC/RW/DEC 75\nDMATC/JDL/SEP 76\nDMA FORM 8290-1-R\nA-1 Example of a Summary of Satellite-Observed Station Card (Letter code \"C\"\non \"Availability of Data\" listing).","DESCRIPTION (WITH BRIEF - TO REACH\")\n315\nFrom the crossroads in the arca known as The Quarter, proceed northwesterly\nalong the asphalt road for 1.8 kms to the Cottage Hospital. Turn left onto a\ndirt road and follow this road for 0.25 kms to the top of Crocus Hill, passing\nLloyds Hotel on the left.\nThe station is situated on top of a seven foot high concrete cistern in the\nsouthwest corner of the ruined courthouse building. A roof has been placed\nover the main part of the building, formerly used as a. jail. This building\nis suitable for use only in the dry season, as the roof leaks very badly.\nJAIL (Not Used)\nCISTERN\nA\n2 EAST BASE\nSTA 10007\nTO\nSTATE\nCISTERN\nJAIL\n(Ruin)\nSTA 10007\nSTEEL WATER-TANK\nA\n1 WEST BASE\nA-2 Example of station description--back of Summary of Satellite-Observed\nStation Card (Letter code \"D\" on \"Availability of Data\" listing).","316\nSTATION PHOTO-IDENTIFICATION\nGEOCEIVER\nPROGRAM\nLOCATION\nCITY\nCOUNTRY\nIN VICINITY OF STATION\nPOINT DESIGNATION\nANGUILLA, WEST INDIES\n10007\nPP 1\nPHOTO NO.\nFLIGHT HEIGHT\nFLIGHT DATE\nIDENTIFIED BY\nSTRIP\nMISSION\nLATITUDE\nLONGITUDE\nDATUM\nELEVATION\nN 18° 13' 01.22\nW 63° 03' 55.05\n1927 MSL\n62.8 m\nNORTHING (METERS)\nEASTING (METERS)\nGRID\nZONE\nDATE ESTABLISHED\n2 014 074.3\n493 096.5\nUTM\n20\nNOV 1975\nNORTHING (METERS)\nEASTING (METERS)\nGRID\nZONE\nDATUM\nMSL\nSURVEYED BY (AGENCY)\nDATE\nDMATC (512 STRE)\nNOVEMBER 1975\nFROM PHOTO POINT TO STATION (S)\nAZIMUTH (North)\nDISTANCE\n10007\n313° 14' 44.\n54.6 m\nDESCRIPTION\nSKETCH\nPP 1 is the south most southwest\ncorner of the house.\nJAIL\nI\n(not used)\nSTA. 10007\nBush\nN\nSTEEL\nWATER\nTANK\nCONCRETE\nWATER TANK\nHOUSE\nPP 1\nDISTANCE\nDIRECTION\nDIFF. IN ELEV\nDISTANCE\nDIRECTION\nDIFF. IN ELEV\nM.\nNORTH\n(METERS)\nM.\nEAST\n(METERS)\nM.\nSOUTH\n(METERS)\nM\nWEST\n(METERS)\nSTEREOGRAM\nPREPARED BY (AGENCY)\nDATE\nREVISED\nDATE\nDMATC\nDEC 75\nDMATC FORM 8350-2\nA-3 Example of picture point data card (Letter code \"P\" on \"Availability of\nData\" listing).","317\nSTATION PHOTO-IDENTIFICATION\nGEOCEIVER\nPROGRAM\nLOCATION\nCITY\nCOUNTRY\nIN VICINITY OF STATION\nPOINT DESIGNATION\nANGUILLA, WEST INDIES\n10007\nPP 2\nPHOTO NO.\nSTRIP\nMISSION\nFLIGHT HEIGHT\nFLIGHT DATE\nIDENTIFIED BY\nLATITUDE\nLONGITUDE\nDATUM\nELEVATION\nN 18° 13' 01.85\nW 63° 03' 57.22\n1927 NAD\n65.6 m\nNORTHING (METERS)\nEASTING (METERS)\nGRID\nZONE\nDATE ESTABLISHED\n2 014 093.9\n493 032.7\nUTM\n20\nNOV 1975\nNORIHING (METERS)\nEASTING (METERS)\nGRID\nZONE\nDATUM\nMSL\nSURVEYED BY (AGENCY)\nDATE\nDMATC (512 STRE.)\nNOVEMBER 1975\nFROM PHOTO POINT TO STATION(S)\nAZIMUTH (North)\nDISTANCE\n10007\n53° 34' 49.\n30.0 La\nDESCRIPTION\nSKETCH\nPP 2 is the northeast corner of a steel\nwater tank.\nJAIL\n(not used)\nSTA 10007\nSTEEL\nN\nPP 2\nWATER\nTANK\nCONCRETE\nWATER TANK\nHOUSE\nDISTANCE\nDIRECTION\nDIFF IN ELEV\nDISTANCE\nDIRECTION\nDIFF IN ELEV\nM.\nNORTH\n(METERS)\nM\nEAST\n(METERS)\nM\nSOUTH\n(METERS)\nM\nWEST\n(METERS)\nSTEREOGRAM\nPREPARED ar (AGENCY)\nDATE\nREVISED\nDATE\nDMATC\nDEC 75","318\nSTATION PHOTO-IDENTIFICATION\nGEOCEIVER\nPROGRAM\nPOINT DESIGNATION\nLOCATION\nCITY\nCOUNTRY\nIN VICINITY OF STATION\nANGUILLA, WEST INDIES\n10007\nPP 3\nIDENTIFIED BY\nPHOTO NO.\nSTRiP\nMISSION\nFLIGHT HEIGHT\nFLIGHT DATE\nLATITUDE\nLONGITUDE\nDATUM\nELEVATION\nN 18° 13' 02.79\nW 63° 03' 55.91\n66.5 in\n1927 NAD\nNORTHING (METERS)\nEASTING (METERS)\nGRID\nZONE\nDATE ESTABLISHED\n2 014 122.6\n493 071.3\nUTM\n20\nNOV 1975\nNORTHING (METERS)\nCATUM\nEASTING (METERS)\nZONE\nGRID\nMSL\nSURVEYED 31 (AGENCY)\nDATE\nDMATC (512 STRE)\nNOVEMBER 1975\nAZIMUTH (North)\nFROM PHOTO POINT TO STATION (S)\nDISTANCE\n10007\n232° 58' 16.\n18.140 m\nDESCRIPTION\nSKETCH\nPP 3 is the northeast corner of the\njail ruin.\nPP 3\nJAIL\n(notused)\nSTA 10007\nBush\nN\nSTEEL\nWATER\nTANK\nCONCRETE\nWATER TANK\nHOUSE\nDIFF IN ELEV.\nDIRECTION\nDISTANCE\nDIRECTION\nDISTANCE\nDIFF. IN ELEV.\nEAST\nM.\nNORTH\n(METERS)\nM\n(METERS)\nWEST\nM\nSOUTH\n(METERS)\nM\n(METERS)\nSTEREOGRAM\nDATE\nDATE\nREVISED\nPREPARED BY (AGENCY)\nDMATC\nDEC 75","319\nDEFENSE MAPPING AGENCY\nTOPOGRAPHIC CENTER\nDEPARTMENT OF GEODESY AND SURVEYS\nSATELLITE GEOPHYSICS DIVISION\nDMATC-GS(52321)\n13 February 1976\nGEODETIC INFORMATION REPORT\n1. Station Name and Location\nGeoceiver Station 10007, Anguilla, West Indies\n2. Geodetic Survey\na. Horizontal\n(1) DMATC (512 STRE) conducted the survey to tie Geoceiver Station\n10007 (ANGUILLA RM 3 1975) to existing control in November 1975. The\nstarting stations were:\nDATUM: 1927 NORTH AMERICAN\nSPHEROID: CLARKE 1866\nNAME Al WEST BASE (DOS) 1958\nLATITUDE N 18° 12' 36..034\nLONGITUDE W 63° 03' 17\".329\nNAME A2 EAST BASE (DOS) 1958\nLATITUDE N 18° 13' 07.116\nLONGITUDE W 63° 03' 04\".068\nValues were taken from Anguilla, B.W.I. trig list, dated September 1958.\nThe order of the positions was not given.\n(2) Geoceiver Station 10007 was tied into the local survey control\nnetwork by triangulation. Stations Al West Base, A2 East Base, and\nGeoceiver Station 10007 were occupied and eight rounds of horizontal\ndirections were observed at each station with a Wild T-3 theodolite.\nNo distances were measured between these stations.\n(3) The station to be occupied was Anguilla RM 3, a point included\nin the adjusted network on the island. The original disk was gone. DMATC\n(512 STRE) replaced the disk with a DMA disk and reobserved angles in the\ntriangle. The resulting recomputation of the position on the Geoceiver\nstation compared with the published position of Anguilla RM 3:00 = +0..006\nand Al = -0.034. This translates to a 1.02 meters shift in position.","320\nDMATC-GS (52321)\n13 February 1976\nb. Vertical\n(1) The vertical survey was conducted by DMATC (512 STRE) and was\nbased upon the following elevations obtained from the Cadastral Survey\nDepartment on Anguilla.\nSTATION NAME\nELEVATION\nDATUM\nORDER\nAl WEST BASE (DOS) 1958\n27.737 m\nMSL\nUNKNOWN\nA2 EAST BASE (DOS) 1958\n13.198 m\nMSL\nUNKNOWN\n(2) The elevation of Geoceiver Station 10007 was determined by\nDouble Zenith Distances (4 rounds each) and adjusted by least squares.\n(3) Geoidal Heights were scaled from AMS 1967 GEOID CHART.\n3. Other Data Acquisition System in the Vicinity\nNone known\n4. Accuracy of Results\na. Survey tie to satellite system site. Errors from survey adjustment\nstatistics are:\n= 0.00022 = 0.007 meter (one sigma)\n00\nor = 0.00031 = 0.009 meter (one sigma)\noh = 0.029 meter (one sigma)\nb. Local Geodetic Control\nThe Directorate of Overseas Surveys (DOS) established control on\nAnguilla for the purpose of large scale mapping. The DOS control was\nconverted to 1927 NAD using USHO station CROWN which had been tied to\nUSAF HIRAN station ANGUILLA.\n5. Index and Reference to Related Records\na. The geodetic survey was performed by DMATC (512 STRE) in November\n1975.\nb. Data pertaining to this job are on file at the Satellite Records\nDesk at DMATC.\n2","321\nSATELLITE OBSERVATION TEAM\nSTATION OCCUPATION REPORT\nThis report will provide information for recovery and occupation\nof each Satellite Doppler Station. It shall be completed and submitted\nas soon as all observations are finished. (When additional space is\nrequired, use reverse side of page).\n1. Station Report\nDate 06 NOV 1975\nSystem reporting (circle one) ITT 5500 (GEOCE IVER) (SN 0010\nSTATION NAME ANGUILLA RM 3\nSTA NO 10007\nLOCATION ANGUILLA ISLAND, BRITISH WEST INDIES\n2. Geodetic Position\nLat N 18 13' 02-22\" Long W 63° 03' 56 35\nSource USC + GS\n3. Name and address of owner of site.\nH.M. COMMISSIONER,\nANGUILLA, BRITISH WEST INDIES\nName and mailing address of Chief of party at station.\nCAPTAIN ARM WILSON EE\nLLOYDS HOTEL, THE VALLEY\nANGUILLA\n4. Site Occupation\nArrival Date 24 OCT 1975\nDeparture Date 10 NOV 1975\nDate 1st Obsn 25 OCT 1975\nDate last Obsn 05 Nov 1975\nOrbit or Event No UT 298/2142\nOrbit or Event No UT 309/ 1918\n77\n68\nSatellite Ident No\nSatellite Ident No\n1\nA-5 Example of Station Occupation Report with 7 attachments (Letter code\n\"0\" on \"Availability of Data\" listing).","322\nOccupation Report contd.\n5. Height of Data Point (Antenna Electrical Center) above station mark.\n1.873\nm. (See C7 & C8)\n6. Was the equipment moved from original location during period of\noccupation? Yes\nNo\nx . If yes, explain and give dates and\napplicable orbit or event number.\nEquipment down time experienced this occupation. List time and\nperiod of each failure.\n25 OCT GELL CELLS AND CHARGER UNSERVICEABLE\n26 OCT 78 KHZ PHASE COMPARATOR UNSERVICEABLE\n7. Collocation (Have any other satellite observation teams had equipment\nin vicinity? Yes No X . If yes, give details.\n8. Local Geodetic Ties\na. Include a sketch showing (proposed) (completed) site survey of\nmonuments, antenna, photo points, and their relation to local\ncontrol. Attachment No.\n/\nb.\nWhat agency (will perform) (performed) survey?\n512 STRE\nC. Check with survey organization of host country to determine if the\nstarting data is the latest accepted values for the areas. (to be\naccomplished by party members only as directed.)\nDATA CHECKED WITH LOCAL SURVEY DEPARTMENT\n2","323\nOccupation Report contd.\n9. The following descriptive data is attached:\na. Station (description) (recovery note) Attachment No 2\nb. Vicinity sketch (showing location of all monuments and photo points)\nAttachment No. 3\nC. Polaroid photos of all station markers. Attachment No.\n4\nd. Polaroid photos of horizon from station marker. Attachment No. 5\ne. Polaroid photos of station from cardinal points from points about\n50 meters distant. Attachment No. 6\nf. Report of any circumstances that may prevent reoccupation. (If\nantenna occupies a non-monumented point such as roof of building,\nprovide a detailed sketch including distances from edges or cone\nof roof so antennas could be replaced in exact location).\nSee Attachment No. 247\ng. Report circumstances that prevented acquisition of any of the above\nitems if not attached.\nALL ITEMS ATTACHED\n10. Communication and Postal Services at site.\na. Local\n(1) Type of communications\nLOCAL ISLAND TELEPHONE SYSTEM\n(2) Quality and cost\nEC $ 0.10\nGOOD QUALITY\nPER CALL\nb. Overseas\n(1) Telephone, radio telephone, or radio\nRADIO TELEPHONE CABLE AND WIRELESS (WEST INDIES) LTD,\nTHE VALLEY, ANGUILLA\n(a) To where\nINTERNATIONAL\n(b) Operating hours\n0800-1800\nMON- FRI\n0800 1600\nSAT\nSUN\nCLOSED\n3 .","324\nOccupation Report contd.\n(1) Telephone, Radio Telephone, or Radio contd.\n(c) Cost\nus # 9.25 per 3 MINITES\nTO WASHINGTON DC\n(d) Discuss local regulations governing use of above that\ncould effect our operations.\n(2) Teletype $ SEE OVER\n(a) To where\nINTERNATIONAL. . TLX SENT TO ANTIGIA AIR STATION\nFOR RETRANSMITTAL ON AUTODIN\n(b) Operating hours\nAIR STATION CLOSED CN\n0800-1800\nMON FRI\n0800 1600\nSAT\nSAT + SUN\nSUN\nCLOSED\n(c) Cost\n$\nPER WORD NORMAL\nTo ANTIGUA\nus\n0.07\n$\nPER WORD\nURGENT\nus\n0.14\n(3) Mail\n(a) Frequency of delivery\nDAILY FROM ST MARTIN OR ST KITTS\nBY AIR\n(b) Type service\nRELIABLE. AIRMAIL TO us OR UK 5 DAYS\n(c) Weight/dimension limits on packages\nMAX PARCEL WT 22LBS\n(d) Costs\nFARCAS 22LBS $ 5.00\nLETTERS EC$ 0.25/102\n11. Transportation (Type of service available with any special addresses\nif required)\na. Air\n4","325\nOccupation Report contd.\n11. Transportation contd.\n(1) Government\nNONE\n(2) Civil\nVALLEY AIR SERVICE.\nCHARTER ANY TIME TO ANYWHERE.\nb. Surface\n(1) Government\nNONE. PWD AND DIPLOMATIC SERVICE HAVE\nLANDROVERS ON ISLAND\n(2) Civil\nFERRY TO ST MARTIN 0830 DAILY EXCEPT THURSDAY AND\nSUNDAY RETURN 1230. us$ 2.00 ONE WAY\nC. Discuss briefly all transportation used during occupations and its\nacceptability.\n(1) MAC FLORIDA TO ANTIGUA\n(2) VALLEY AIR SERVICE CHARTER ANTIGUA/ ANGUILLA\n2x ISLANDERS FOR FREIGHT. 1x AZTEC FOR TEAM\n(3) IX 3/4 TON SAFARI LANDROVER FROM DIPLOMATIC\nSERVICE\n12. Local contracts (name, title, address of individual(s) providing\nexceptional help, list type of assistance provided)\na. HER MAJESTY'S COMMISSIONER AND HIS ADMINISTRATIVE OFFICER\nMR LE BRETON AND MR MARSHALL RESPECTIVELY\nb. MANAGER CABLE AND WIRELESS\nMR WOLFENDEN\n13. Power\na. Type power (determine voltage variance and frequency stability)\nGENERATORS USED\n110 V\n2x MITELITE 3.5 H.P.\nb. Distance from power source to site\nNEAREST MAINS POWER 400M AT LLOYD'S HOTEL\n5","326\nOccupation Report contd.\n13. Power contd.\nC. Connection, service requirements, and costs\nNOT NECESSARY FOR SHORT OCCUPATION\nd. Special equipment (to be provided by installing firm)\nNOT ESTIMATED\ne. Installing firm\nPWD IF NECESSARY\n14. How was tracking equipment protected from weather on site?\n(Tent, Building, Truck, Trailer, etc)\nIN REMAINS OF OLD JAIL. CGI ROOF WATERPROOF\nEXCEPT DURING HEAVY SHOWERS\n15. Repair, maintenance and services available at site (i.e. construction\nmaterials, POL, electronic, rentals, etc.)\n4. CONSTRN MATLS, POL. ALBERT LAKE LTD REASONABLE SUFPL-\nh. ELECTRONIC . BY ARRANCEMENT WITH Ct w. LTD\n16. Housing and subsistence facilities. Discuss prices and\nacceptability.\na. LLOUD'S HOTEL USED. ROOM EACH WITH SHOWER (COLD WATER\nONLY ) AND BASIN (COLD WATER ONLY) AND we us$ 12.00\nPER DAY. FULL BOARD INCLUDED.\nb. OTHER HOTELS WILL COST up TO us$40.00 PER DAY\n17. Office and storage space available at site.\n4. INSIDE RUINED JAIL BUT NOT 100% WATER TIGHT.\nb. OFFICE SPACE AT HOTEL.\n18. Describe medical facilities including emergency evacuation\nprocedures.\n7 BED HOSPITAL, ONE DOCTOR.\nAIR CHARTER VALLEY AIR SERVICE\n6","327\nOccupation Report contd.\n19. Military installations that can be of assistance; if not already\nspecified.\nNONE\n20. Ground environment - Discuss seasonal variations in climate and\nsuggested clothing.\nTROPICAL WET / DRY SEASONS\nLIGHT SUMMER CLOTHING\n21. Entry Requirements\na. Immigration (visa information)\n(1) Military personnel\nDIPLOMATIC CLEARANCE REQUIRED. PASSPORT INSPECTED\nON ARRIVAL\n(2) American civilians\nDIPLOMATIC CLERRANCE REQUIRED PASSPORT INSPETED\nON ARRIVAL. VISA REQUIREMENT UNKNOWN.\nb. Customs duty and exemptions\n(1) Observational equipment\nNo D4 TM\n(2) Personal effects (clothing, radios, cameras, guns, unusual\npractices, etc.)\nNO DUTY ON ITEMS NOT STAYING IN COUNTRY. NC\nGUNS ALLOWED\nC. Taxes applicable to station personnel\n22. Other pertinent and useful information\na. Monetary\n(1) Currency used\nEAST CARIB BEAN DOLLAR AND BUT us DOLLAR\nGENERALLY ACCEPTABLE FOR LARGE PAYMENTS\nE.G. AIR CHARTER AND HOTEL\n7","328\nOccupation Report contd.\n22. Other pertinent and useful information contd.\n(2) Exchange rate(s)\n$\n14 $ $ V\n2.27\nEC\nCHANGES DAILEY\nH\nL I\n4.80 EC\n2\n(3) Location of bank\nTHE VALLEY.\nBARCLAYS BANK INTERNATIONAL. BANK AMERICA\n(4) Check cashing capability (personal/government)\nBARCLAUS WILL CASH BRITISH CHEQUES WITH BANKERS CARD\nBOTH WILL CASH GOVERNMENT CHEQUES\nb. Community\n(1) Description (general information on churches, stores,\nrecreation facilities, etc.)\n(a) CHURCHES- -- MANY CHRISTIAN CHURCHIS\n(h) STORES - SEVERAL, HIG-H PRICED, VERY LIMITED IN\nMEATS FRESH VEG. AND CLOTHING\n(c) RECREATION FACILITIES: EXCELLOUT SEA BATHING. WATER WARM\nAND CLEAR FOR SNCPKELLING BUT FEW FISH. BUATING AND\nWATER SKING. A FEW POOR QUALITY BARS AND CAFE'S\n(2) Local customs (identify political and ethnic groups with\nrecommendations for the safe conduct of station personnel).\nPEOPLE MOSTLY OF AFRICAN ORIGIN AND BRITISH\nCULTURE.\n8","329\nOccupation Report contd.\n22. Other pertinent and useful information contd.\nC. Discuss regulations, conditions, practices, customs, etc., that\ncould adversely effect operations and suggested procedures for\nreducing or eliminating their impact.\nNONE\nd. Discuss precautions required by station personnel for local\nsanitation, drinking water, diseases, wild animals, etc.\n(1) ONLY BOILED RAIN WATER SHOULD BE DRUNIC\nTAP WATER IS BRACKISH FROM UNDERGROUND\nWELLS\n(2) MOSQUITOES ARE ACTIVE AFTER RAIN No DANGER OF\nMALARIA\ne. Other information of an unusual nature which would assist in\nthe efficient operation of the station.\n(1) VISIT H.M.C. ON ARRIVAL\n(2) PAY COURTESY VISIT TO CHIEF OF POLICE\n9","330\nGEOCEIVER\nELECTRICAL CENTER\n0.483 meters\nA = 1.390 metres\nFIELD PARTY SHALL MEASURE DISTANCE (A) FROM TOP OF STATION MARK TO\nTHE BOTTOM SURFACE OF THE PREAMPLIFIER NOT INCLUDING ADAPTOR\nPLATE.\n0.483 meters\nA\nB\nPIER\nFIELD PARTY SHALL MEASURE HEIGHT OF PIER (B) WHEN APPLICABLE IN ADDITION\nTO DISTANCE (A).","331\nANGUILLA SURVEY DIAGRAM\n1975 SURVEY\nNOT TO SCALE\nPP-3\nA2 EAST BASE\nSTA. 10007\nANGUILLA RM3 1975\nPP-2\nPP-1\nA1 WEST BASE\nTO: ANTENNA\nAIRSTRIP\nTO: ANGUILLA 372\nDistances to Picture Points were\nMeasured with Subtense Bar\nA-6\nAtch 1","332\nDESCRIPTION OF TRIANGULATION STATION\ncountry:\nSTATE:\nCOUNTY\nNAME OF STATION:\nAnguilla RM 3\nAnguilla Island\nBritish West Indies\nCHIEF OF PARTY\nYEAR:\nDESCRIBED BY:\nMSgt Green\n1955\nMSgt Green\nNOTE.\nHEIGHT OF TELESCOPE ABOVE STATION MARK\nMETERS, HEIGHT OF LIGHT AHOVE STATION MARK\nMISTI RS.\nDISTANCES AND DIRECTIONS TO AZIMUTH MARK, REFERENCE MARKS AND PROMINENT\nSURFACE-STATION MARK.\nOBJECTS WHICH CAN BE SEEN FROM THE GROUND AT THE STATION\nUNDERGROUND-STATION MARK\nDISTANCE\nDIRECTION\nOBJECT\nBEARING\nFEET\nMETERS\no\nCROWN\nSE\n2017.8\n00\n00\n00\nANGUILLA (Not Found)\nS\n14.924\n67\n39\n25\nANGUILLA RM 1\nW\n18.072\n137\n54\n55\nStation ANGUILLA RM 3 is located atop the southeast end of an 8 foot\nhigh concrete cistern which is situated at the southwest corner foundation\nof the former Crocus Hill court house which was demolished by a hurricane\nin January 1954. At present, a roof has been placed over the northeast\nsection of the foundation to provide a jail. The station mark, a disk shaft,\nis located in the concrete surface of the cistern.\nTo reach station from Wallblake airfield, follow the main road (asphalt)\nnortheasterly for 0.9 km to the crossroads, Turn left and proceed north-\nwesterly on asphalt road through the vallev for 1.8 km to a dirt road on\nthe left. Turn left just before the hospital and proceed southwesterly for\n0.25 km, passing Loyd's Hotel on the left, to the site directly above\nCrocus Bay.\nStation recovered by Sgt. S. Brown, STRE, November 1975. Station mark\nwas replaced with DMA bronze disk stamped \"ANGUILLA RM 3 1975. \"\n&\nRefers to notes in manuals of triangulation and state publications of triangulation. Direction-angle measured clockwise, referred to initial station\n1 To nearest meter only. when no trigonometric leveline is being done.\nA-7\nAtch :","333\nVICINITY SKETCH\nANGUILLA ISLAND\nGEOCEIVER STATION 10007\nN\nHospital\nESSO\nStorage\nTanks\nPolice\nStation\nCrocus Bay\nANGUILLA\nRM 3\nWarden\nGEOCEIVER\nHouse\nSTATION\nCenter\nof Town\n10007\nRoad\nto Island\nFactory\nHarter\nA\nCROWN\nAirstrip\nCustoms\nHouse\nPier\nForest\nPoint\nA-8\nAtch 3","334\nANGUILLA SITE SKETCH\nN\nGEOCEIVER STA 10007\nRoad\nPolice\nStation\nRuins\nOpen\nArea\nJail\n(Not Used)\nFoundation of Ruined\nCourthouse\nCistern\nRM 3 (USNHO)\nGEOCEIVER STA\n10007\n1\nAtch 3","335\nANGUILLA\nGeoceiver Station 10007\nPhoto of Station Marker\nStamping on Station Marker\nStation known as ANGUILLA RM 3.\nNo stamping on mark. Disk was\nremoved and only the shaft remains. .\nA-9\nAtch 4","336\nGeocavor Station 10007\nMarkings on disk, Anguilla Rm3, Year 1975\nGeo Sta 10007 By 512 STRE\n(DSR replaced by 52 STRE November 1975)\nAttachment 4'","Reference Marks,\nRemains of Rm I for\n337\nStation Angulla. reference mark\nfor Geoceiver Stativ 10007\n10007\nRm2 for Station Anyvilla\nReference mark for Geocuiver\nStation 10007\nUSAF Geachitic Syn Disk,\nof\nDE\nAnywher 372\nLail Cadastral Sirvey point\nReference mark for Georeiver\nStation 10007\nAttachment 42","338\nANGUILLA\nGeoceiver Station 10007\nNorth\nHorizon Profile Photographs\nEast\nA-10\nAtch 5","339\nANGUILLA\nGeoceiver Station 10007\nHorizon Profile Photographs\nSouth\nWest\n1\nAtch 5","340\nANGUILLA\nGeoceiver Station 10007\nHorizon Profile Photographs\n,\n+\n+\n2\nAtch 5","341\nANGUILLA\nGeoceiver Station 10007\nCardinal Point Photograph\nLooking North\nLooking East\nLooking South\nLooking West\nA-11\nArch 6","342\nN\nANGUILLA ROOF SKETCH\nGEOCEIVER STA 10007\nFoundation of Ruined Customs and Courthouse\nJail (Not Used)\n3.19\nCistern\n6.98\n1.63\n2.21\n2.63\nANGUILLA RM 3\n5.22\nGEOCEIVER STA 10007\n6.98\nNote: All measurements in meters.\nA-12\nAtch 7","343\nATMOSPHERIC DRAG ANALYSES OF LOW-ALTITUDE\nDOPPLER BEACON SATELLITES\nK. S. W. Champion\nAeronomy Division, Air Force Geophysics Laboratory (AGSC)\nL. G. Hanscom AFB, MA 01731\nand\nJ. M. Forbes\nSpace Data Analysis Laboratory, Boston College\nChestnut Hill, MA 02159\nAbstract\nSatellite orbital studies at the Aeronomy Division, Air Force Geophysics\nLaboratory, are primarily aimed at deriving atmospheric densities from orbital\ndecay, and developing and evaluating density models for use in predicting\nsatellite ephemerides. In this paper we present drag analyses using Doppler\nbeacon data from three low-altitude satellites (DB-7, DB-8, and DB-9), and\nmake comparisons with results obtained from ADCOM radar skintrack and SCF\nSGLS (Space-Ground Link Subsystems) observations for the same satellites.\nOur major results are: (1) Predicted positions computed solely from skin-\ntrack or SCF data contain a relatively large error component due to inaccur-\nacy in initial orbital elements. This error component is minimal for the\nDoppler beacon data, thus allowing a much improved estimate of the error\ncomponent due to atmospheric drag; (2) The high degree of accuracy of the\nDoppler beacon data permits shorter-term fit spans over which the drag can\nbe determined, allowing study of higher-frequency density fluctuations;\n(3) Skintrack data yield equally good accuracy for longer-term density vari-\nations; (4) It is estimated that ephemeris prediction errors for low-perigee\nsatellites can increase by a factor of three or more over the next six years\ndue to the increase in solar and magnetic activity.\nIntroduction\nDuring the past decade, satellite orbital studies at the Aeronomy Divi-\nsion, Air Force Geophysics Laboratory, have concentrated on deriving atmos-\npheric densities from orbital decay, and developing and evaluating density\nmodels for predicting satellite ephemerides. Most of this work involves\nuse of ADCOM radar skintrack and SCF SGLS (Space-Ground Link Subsystem)\nobservations, and computer programs developed by IBM Corporation (Bramson and\nSlowey, 1974) under contract with the U.S. Air Force. Recommendations are\noften made to various agencies regarding the density and geopotential models\nutilized in their operational software systems for orbital calculations\n(e. g. , Forbes and Bramson, 1971; Forbes, 1972; Garret et al, 1975). Recently,\nhigh-accuracy Doppler beacon analysis of several low-perigee satellites\nhave been performed (Champion et al, 1975; Bass et al, 1975). Both the raw\nDoppler data and the CELEST orbital program were provided by the Naval Surface\nWeapons Center, Dahlgren, Va. This opportunity has enabled intercomparisons\nbetween the high-accuracy Doppler beacon data, and the less accurate skin-\ntrack and SCF data which we have utilized for many years.","344\nWe should point out that the extremely high accuracy provided by the\nDoppler beacon system is not fully utilized in most of the drag analyses which\nwe perform. That is, the degree of refinement in current atmospheric density\nmodels is so poor (approximately 10% accuracy during quiet times; up to 100%\nduring geomagnetically active periods) that density accuracies much better\nthan 1% (or perigee height determinations to better than a few hundred meters)\nare of little additional value. The usefulness of the Doppler beacon data\nprimarily lies in its availability as a standard to compare our skintrack\nand SCF results, and its ability (due to the high accuracy) to determine\napproximately 4-6 drag values per day, as opposed to the 1 drag value per\nday permitted by skintrack observations. Thus shorter-term fluctuations in\ndensity, which strongly influence the accuracies of predicted ephemerides\nfor low-perigee satellites, can be resolved and modelled.\nAn example of density variability during a period of magnetic activity,\nand\nthe degree of performance of two atmospheric density models for predict-\ning satellite ephemerides, is presented in Fig. 1. Figure la shows the\nactual density variation as determined from orbital decay analysis of a\nlow-perigee satellite using SCF observations, the density variation from a\npurely static model, and the density variation predicted by the Jacchia (1971)\nmodel where the geomagnetic variation is parameterized through the planetary\nmagnetic indes, Kp. Figure 1b shows the predicted positional errors (actual\nposition minus predicted position) for the two models during the same time\ninterval as Fig. 1a. The scenario illustrated by these figures goes\nsomething as follows. After a quiet period, the atmosphere responds to an\nincrease in magnetic activity with a delay of about 9 hours (Kp index not\nshown). The static model, since it predicts no time variation in density at\nall, results in a positive in-track error, since the satellite is further\nahead in position than predicted. On the other hand, the Jacchia model\npredicts a premature density increase, resulting in a negative in-track error\nwhich grows quadratically during the ramainder of the prediction interval\n(i.e., the fact that the atmospheric density actually increases several\nhours later provides little compensation). The net result is that the pre-\ndicted positional error is equally large for the more sophisticated Jacchia\nmodel, simply because it is just as disastrous to predict an out-of-phase\nvariation as no variation at all. It is this type of short-term density\nfluctuation which is revealed by the short drag segments permitted by the\nDoppler beacon data, and which we are attempting to model.\nOrbital Fits and Ephemeris Predictions\nThree satellites are chosen for analysis in this paper. These are\ndesignated DB-7, DB-8, and DB-9, which were launched in March, June, and\nNovember, respectively, in 1973. These satellites possessed similar orbits\nwith inclinations 2 96°, eccentricities 2 .01, perigee heights near 160 Km,\nand perigee local times near noon. Density determinations for the three\nsatellites were performed for a total of 130 days utilizing both Doppler\nbeacon and skintrack data. In this section we concentrate on 12 particular\ntest cases (4 for each satellite) which were also analyzed with SCF data,\nand for which ephemeris predictions were additionally performed.","345\nThe CADNIP and BADMEP programs (Bramson and Slowey, 1974) were utilized\nto determine the initial orbital elements (including drag factor) and predicted\nephemerides, respectively, for the SCF and skintrack observations. The CELEST\nprogram was utilized to analyze the Doppler beacon data. Modifications to\nthese programs to ensure consistency, and comparisons between orbit determina-\ntions have been reported elsewhere (Bass et al, 1975). Data fit spans for\norbit determinations were approximately 27 hours for all three types of\nobservational data analyzed; however, whereas the skintrack and SCF data\nyielded 1 density determination per fit span, the Doppler beacon data yielded\na drag value every 4 to 6 hours.\nPerigee heights from the initial orbit determinations, and the vector\nmagnitude errors in predicted position after 12 hours, are listed in Tables I\nand II, respectively, for the three types of observational data. All of\nthese computations were performed using the Jacchia (1964) atmospheric density\nmodel, and the Standard Earth III geopotential model (Gaposchkin, 1973).\nDifferences between skintrack and SCF perigee heights, and the Doppler beacon\nperigee heights, are on the order of 300-800 meters. Residuals from the best\nfit ephemeris averaged about 10-40 meters for Doppler beacon and 300-1000\nmeters for the SCF and skintrack fits. Since identical drag and geopotential\nmodels are utilized in the ephemeris computations, we conclude that these\nerrors in initial position (which can also be interpreted as errors in the\ndrag correction factors) account for the general trend of large prediction\nerrors for the skintrack and SCF data as opposed to the Doppler beacon\nresults.\nIt has been our experience that the accuracy of SCF data is considerably\nbetter than the skintrack observations. Several reasons why this accuracy is\nnot realized in the data presented here are as follows:\n(a) Optimum SCF data coverage was not available, probably because the\nSCF tracking stations gave priority to their own satellites. For\ninstance, it was noted that there were relatively few range\nmeasurements in the SCF observational data, whereas this is rare\nfor SCF satellites which we have analyzed.\n(b) Combined with (a), the limited geographical distribution of SCF\ntracking stations might introduce biases into the observational\ndata, or into the atmospheric drag encountered by the satellites.\n(c) The SCF radar biases utilized in our programs might require\nupdating.\nOur remaining comparisons and conclusions will, therefore, be restricted\nto skintrack and Doppler beacon results.\nThe Doppler beacon prediction errors (Table II) as compared to the skin-\ntrack data show about a factor two improvement (an average of 2.42 Km after\n12 hours, as opposed to 5.56 Km). Considering the relatively higher accuracy\nafforded by the Doppler beacon data, one would expect the improvement in\nprediction error to be considerably better. By analyzing the atmospheric\ndrag in 4-6 hour segments as determined from the CELEST program, we have","346\nTable I\nPERIGEE HEIGHTS FROM INITIAL ORBIT DETERMINATION\n(Kilometers)\nSatellite\nDoppler Beacon\nSkintrack\nSCF\nDB-7-a\n158.597\n158.81\n159.01\n-b\n160.783\n161.38\n160.96\n158.118\n-C\n158.19\n158.38\n-d\n160.792\n161.69\n161.33\nDB-8-a\n162.703\n163.66\n163.28\n-b\n163.152\n163.51\n163.67\n-C\n163.103\n163.48\n163.74\n-d\n163.310\n163.95\n164.09\nDB-8-a\n164.623\n165.28\n165.31\n-b\n167.615\n168.22\n168.46\n167.458\n-C\n167.73\n167.76\n-d\n167.035\n167.15\n167.95","347\nTable II\n12-HOUR PREDICTION ERRORS FOR SKINTRACK, SCF, AND DOPPLER BEACON DATA\nPrediction Origin\nDay No.\nVector Magnitude Errors (Km)\nSatellite\nM. .J.D.\n(1973)\nSkintrack\nDoppler Beacon\nSCF\nDB-7-a\n41758.00\n76\n11.7\n2.7\n6.8\n-b*\n41760.00\n78\n10.5\n12.5\n5.0\n-C\n41756.00\n74\n21.0\n2.5\n6.9\n-d\n41765.00\n83\n.60\n.84\n1.1\nDB-8-a\n41903.00\n221\n3.1\n.36\n4.8\n-b\n41890.00\n208\n1.1\n.86\n6.9\n-C\n41905.00\n223\n2.9\n.90\n5.8\n-d*\n41898.00\n216\n4.6\n2.9\n7.4\nDB-9-a\n42001.00\n319\n4.0\n.32\n4.3\n-b*\n42040.00\n357\n3.3\n2.3\n2.5\n-C\n42016.00\n334\n1.7\n0.0\n2.8\n-d*\n42023.00\n341\n2.2\n2.8\n4.6\nAverage Prediction Errors\n5.56\n2.42\n4.91\n*\ndenotes cases where variability of atmospheric density exceeds +10% during\nprediction interval","348\nconcluded that much of this disparity can be explained by the variability of\natmospheric density during the prediction interval. Specifically, the four\nDoppler beacon predictions in Table II which do not show considerable improve-\nment over the skintrack results are the only cases where the variability of\natmospheric density exceeds +10% during the prediction interval. When the\nasterisked cases are deleted from Table II, the prediction errors after 12\nhours become 5.76 Km for skintrack, and 1.06 Km for Doppler beacon, more in\naccord with the relative accuracies afforded by these data.\nAll of the density variations discussed above are associated with\nvariable magnetic activity, as indicated by the planetary magnetic index,\nKp, or the auroral electrojet index, AE. Some examples of the correlation\nbetween atmospheric drag, magnetic activity, and ephemeris prediction errors\nare discussed in the following section.\nVariations in Atmospheric Drag\nTo begin with, let us examine the variability of atmospheric drag for\ncase DB-7-b in Table II where the predicted positions for skintrack and\nDoppler beacon data are 10.5 Km and 12.5 Km, respectively. Figure 2\ndemonstrates a high correlation between the variability in atmospheric drag\nand the auroral electrojet index during the prediction interval. This\nrelationship has been previously noted in other low-perigee satellite data\n(Forbes and Marcos, 1973), and the density increases interpreted as the\nresponses to joule heating surges in the auroral electrojet. Figure 1 and\nthe discussion in Section 1 demonstrate how such drag variations can account\nfor the relatively large prediction errors for the astrisked cases in\nTable II.\nIn Figs. 3 and 4 are plotted density variations during selected time\nintervals for DB-7 and DB-9 which illustrate the type of geomagnetically-\nrelated density variation which contributes to the loss of accuracy in\npredicted ephemerides of low-perigee satellites, and which we are attempting\nto model. The density ratio plotted in these figures is defined as the\ncomputed density divided by the Jacchia (1971) model density with Kp arbit-\nrarily set equal to 2. This ratio is therefore expected to represent\nvariations related solely to magnetic activity, since other variations\n(i.e., altitude, semiannual, etc.) have (presumably) been removed from the\ndata. Even in these short segments of data, the density response is seen to\nvary in amplitude and phase from case to case. To complicate matters, we\nknow from previous density measurements that the amplitude of the response\nand its time delay vary with latitude, reflecting the time necessary for the\ndisturbance to propogate from the auroral region to lower altitudes. On\nthe other hand, the existence of such a time delay lends hope to the possible\nprediction of this phenomenon. Density data derived from high-accuracy\nanalysis of Doppler beacon satellites, and in-site accelerometer density\nmeasurements, are being actively analyzed at AFGL to empirically model this\nphenomenon, and to develop an improved density model for predicting satellite\nephemerides.\nThe ramifications of the results presented in this and the previous\nsections are as follows. During periods where the density fluctuations during","349\nthe prediction span exceed 10%, usually due to variations in geomagnetic\nactivity (joule heating), predictions based on Doppler beacon data are\nnearly degraded to skintrack accuracies. Based upon the analysis of predicted\nephemerides of low-perigee SCF satellites, Forbes (1972) has estimated that\nprediction errors increase on the average by a factor of two from quiet to\nactive geomagnetic conditions. This is a conservative estimate since observed\nrather than predicted magnetic indices were utilized in the prediction phase\natmospheric density model. Furthermore, since the degradation of the Doppler\nbeacon predictions appears to be more sensitive to this effect, it would not\nbe surprising to see the average 12-hour prediction errors for Doppler beacon\nsatellites to increase by a factor of 3 or more over the next six years,\ndue to the expected solar cycle rise in the intensity and frequency of\nmagnetic activity variations.\nFinally, by taking 27-hour running means of the Doppler beacon data\npresented here, much better agreement with densities derived from skintrack\ndata was obtained (Bass et al, 1975). Thus, skintrack-derived models of\nlonger-term density variations (27-day, semiannual, etc.) would not be\nsignificantly improved using Doppler beacon data.\nConclusions\nThe major conclusions to emerge from this study are as follows:\n(1) Predicted positions computed solely from skintrack or SCF data\ncontain a relatively large error component due to inaccuracy in\ninitial orbital elements. This error component is minimal for the\nDoppler beacon data, thus allowing a much improved estimate of the\nerror component due to atmospheric drag.\n(2) The high degree of accuracy of the Doppler beacon data permits\nshorter-term fit spans over which the drag can be determined,\nallowing study of higher-frequency density fluctuations.\n(3) Skintrack data yield equally good accuracy for longer-term density\nvariations.\n(4) It is estimated that ephemeris prediction errors for low-perigee\nsatellites can increase by a factor of three or more over the next\nsix years due to the increase in solar and magnetic activity.\nAcknowledgements\nWe gratefully acknowledge the efforts of Dr. J. Bass, Logicon Corp.,\nwho performed the Doppler beacon ephemeris computations, and Ms. D. Gillette,\nAFGL, who analyzed the skintrack and SCF data.","350\nReferences\nBass, J. N. , Bhavnani, K. H., and Hussey, I. M. (1975), Atmospheric Density\nDetermination from Analysis of Doppler Beacon Satellite Data, AFCRL\nRept. No. AFCRL-TR-75-0176.\nBramson, A. S., and Slowey, J. W. (1974), Some Recent Innovations in Atmospher-\nic Density Programs, AFCRL Rept. No. AFCRL-TR-74-0370.\nChampion, K. S. W., Forbes, J. M., Bhavnani, K. H., Slowey, J. W., Gillette,\nD. F., and Hussey, I. (1975), Densities Near 160 Km Obtained from\nOrbital Analysis of Satellite 1973-14A, AFCRL Rept. No. AFCRL-TR-75-0253.\nGaposchkin, E. M. (1973), 1973 Smithsonian Standard Earth III, Smithsonian\nAstrophysical Observatory Spec. Rept. 353.\nGarrett, H. B., , Forbes, J. M., and Champion, K. S. W. (1976), Geopotential\nModel Effects on Low-Altitude Satellite Ephemeris Prediction, AFGL\nRept. No. AFGL-TR-76-0014.\nForbes, J. M. (1972), Low-Altitude Satellite Ephemeris Prediction, AFCRL\nRept. No. AFCRL-72-0428.\nForbes, J. M., and Bramson, A. S. (1971), Evaluation of Upper-Atmosphere\nDensity Models for Predicting Satellite Ephemerides, AFCRL Rept. No.\nAFCRL-71-0515.\nForbes, J. M., and Marcos, F. A. (1973), Thermospheric Density Variations\nAssociated with Auroral Electrojet Activity, J. Geophys. Res., 78,\n3841.\nJacchia, L. G. (1974), Static Diffusion Models of the Upper Atmosphere with\nEmpirical Temperature Profiles, SAO Special Rept. No. 170.\nJacchia, L. G. (1971), Revised Static Models of the Thermosphere and\nExosphere, Smithsonian Astrophysical Observatory Spec. Rept. 332.","351\nFigure Captions\nFigure\nla\nActual Density Variation as Determined from Orbital Decay\nAnalysis of a Low-perigee SCF Satellite, The Density Variation\nfrom the Purely Static SCF Model, and the Density Variation\nPredicted by the Jacchia (1970) Model where the Geomagnetic\nVariation is Parameterized through the Planetary Magnetic\nIndex, Kp.\n1b\nPredicted Positional Errors (Actual Position Minus Predicted\nPosition) for the Two Models During the Same Time Interval\nas (a) .\n2\nDensity Ratio from DB-7 and Auroral Electrojet Index for\nDay 78, 1973.\n3\nDensity Ratio (Defined in Text) from DB-7 and Kp for Days\n100-104, 1973.\n4\nDensity Ratio (Defined in Text) from DB-9 and Kp for Days\n337-341, 1973.","-\nt+1.0\nMODEL\n1971\nTIME ( DAYS)\nMODEL\nSCF\n++0.5 o\nto\n+20\n10\n-20\n10\nO\n+\nFIG. la & b\nMODEL\nMODEL\nSCF\nX\n1971\nATMOSPHERE\nX-\nX--X--X\n-\n1.0\n1.2\n1.1\np(t)\np(t)","353\n1.20\n1.15\n1.10\np(t)\nP (to)\n1.05\n1.00\n95\n1200\n1000\n800\nAE\nINDEX\n600\n(GAMMAS)\n400\n200\nO\n0.25 0.50 0.75\n1.0\nTIME ( DAYS )\nMARCH 19, 1976\nFIG. 2\nAFGL PHOTO 16-413 -","---------\n105\nx\nFIG. 3\nx\n104\n103\nDAY IN 1973\n*\n102\nx\n101\nAFGI.PHOTO 16 6 9\n*\n1.4 DB-7\n100\n1.3\n1.2\n1.0\n1.1\n0.9\n0.8\n9\n6\n3\n0\n\"x\n#0110","342\nFIG. 4\nX\n341\n340\nX\nDAY IN 1973\nx\n339\n338\n16-468\n1.4 DB-9\nAFGL PHOTO\n337\n0 h\n1.3\n1.2\n1.0\n1.1\n0.9\n0.8\n9\n6\n3\ndy","356","357\nMODELING OF RESIDUAL RANGE ERROR IN\nTWO FREQUENCY CORRECTED DOPPLER DATA\nDr. Arnold J. Tucker\nDr. James R. Clynch\nMr. H. Lyle Supp\nRadio Sciences Division\nApplied Research Laboratories\nThe University of Texas at Austin\nAustin, Texas 78712\nIntroduction\nIn the use of NAVSAT's to obtain an accurate location, signals are\nreceived at two frequencies (150 MHz and 400 MHz) and the Doppler at these\nfrequencies combined to eliminate the first order effects of the ionosphere.\nThis technique is based on a power series expansion of the refractive index\nof the ionsophere where only the first correction term is kept. Two frequency\ncorrected Doppler data remove almost all of the ionsopheric error in NAVSAT\npositioning. However, there remains residual errors due to:\n1) Higher order terms in the refractive index, and\n2) Bending of the optical path.\nThese two factors will cause the range between an observer and a NAVSAT\nbased on two frequency data to be long. The measured range, referenced to\nthe 400 MHz signal, minus the true range will be denoted in the residual\nrange error (RRE). The magnitude of the RRE and its major functional depen-\ndences on ionspheric and geometric parameters have been determined by perform-\ning a computer experiment. In this experiment, the difference between the\ntrue vacuum phase and the measured phase along the refracted path for each\nfrequency has been computed using a sophisticated model of the ionosphere.\nThe optical path used in this calculation was obtained by tracing the ray\nbetween satellite and observer. These calculations were made for simulated\npasses at eight locations distributed over the earth at four universal times.\nIonospheric parameters characteristic of the last solar maximum (1968) were\nused.\nThe simulated passes form a data base which was analyzed to determine\nthe dependence of the RRE on various parameters. It was found that a very\ngood fit was obtained to all the data by a power series in the zenith angle\ntimes the cosecant of the elevation angle (to represent the variation of the\nslant range and times the fourth power of the critical frequency at the\nlocation where the ray passes an altitude of 500 km.\nThe computer model used to simulate the ionosphere is described in\nSection II. In Section III, the procedure used in this analysis is presented\nin detail along with the experimental results.","358\nA Numerical Model for a Global Ionosphere\nA world wide ionospheric model has been developed and implemented on the\nARL/UT 3200 computer system. This model is based principally on the work of\nR. B. Bent, et al, 1 with additions and modifications derived from the work\ndone at the Institute of Telecommunications. The model consists of E, F1,\nand F2 regions, and the dependence of the electron-density profile on geo-\ngraphic location, time of day, season, and solar activity is included. In\nthe following sections, the modeling of each ionospheric region will be\ndiscussed. A schematic diagram of a profile is shown in Fig. 1, and a list\nof parameters is given in Table I. In this model, the total contribution\nto the electron density at any given height is the sum of the contributions\nfrom each region at that height.\nThe E Region\nIn the altitude range from 95 km to 145 km, the electron density is\nrepresented in the functional form:\n2\nh\nHE\n-\nm\n(1)\nNE(h) = Noe\n1\n=\nYE\nfor 95 km < h < 145 km\nwhere\nNE(h) = The contribution to the electron density at a height,\nh, due to the E region (electrons/m3),\n= Peak electron density (electrons/m3\nN oE\n= K 1 (F E) 2, K 1 = 1.24 X 1010 el/m³ MHz2,\nFE\n= Critical frequency of the ordinary component of\no\nthe E region (MHz), ,\nHeight of maximum ionization of E region (km),\nH\nE\n=\nm\nSemithickness of the layer (km).\nY\nE\n=\nm\nFor this model, H E as given by G. W. Haydon 2 is taken to be 120 km, and\nm\nY E to be 25 km. The expression for F E contains the dependence on solar\nactivity m and position. The functional form as given by Van Zandt, et al³\nis:\nx]1/4\n[\n(180 + 1.44 . R) . cos\n(2)\nFE=0.9 .\nwhere\nR = 12-month smoothed mean Zurich sunspot number,\nX = Solar zenith angle.\nThe nighttime value of F E as given by J. M. Watts4 is taken to be 0.5 MHz;\no\ntherefore, to make a smooth transition, Eq. 2 is used until a critical","359\nH3\nH3,\nm\nH2\nH2m\nHI\nHIm\nHorit\nHmF2\nYmF2\nHmF\nYm1 F1\nHmE\nYm\nE\nFOE\nFOF1\nF0F2\nPlasma Frequency\nFigure 1\nVertical Electron-Density Profile\nAE-76-4","360\nzenith angle is obtained from:\n180 180 + 1.44 - R ] - 1 + 1.44 R -1\ncos\n.\nBeyond this value of X 'crit' 0.5 MHz is\nused.\nTable I\nList of Parameters for Ionospheric Electron-Density Profile\nF E: Critical Frequency of E Region\no\nE: Height of Maximum Ionization of E Region\nH\nm\nY E: Semithickness of E Region\nm\nF F1: Critical Frequency of F1 Region\no\nH F1: Height of Maximum Ionization of F1 Region\nm\nY F1: Semithickness of F1 Region\nm\nF F2: Critical Frequency of F2 Region\nO\nH F2: Height of Maximum Ionization of F2 Region\nm\nF2: Semithickness of Lower and Middle F2 Region\nY\nm\nK1,K2,K3 : Decay Constants for Upper F2 Region (Topside)\nHeight at which Middle and Upper F2 Regions match Gradients\ncrit:\nCenter of Lower Topside\nH1m:\nH2\nCenter of Middle Topside\nH3\nCenter of Upper Topside\nThe F1 Region\nThe F1 region has no definite range in altitude since the height of\nmaximum ionization and thickness vary with time of day. The electron\ndensity is represented in the functional form\n(3)\nfor\nm\nwhere\nNF1 (h) = Contribution to the electron density at a height h due to the\nF1 region (electrons/m3), ,\nNof1 = K-1 F F12, Peak electron density of layer el/m³), ,","361\nF F1 = Critical frequency of the ordinary component of the F1 region\nO\n(MHz), ,\nH F1 = Height of maximum ionization of the F1 region (km), ,\nm\nY F1 = Semithickness of layer (km) .\nm\nExpressions for H F1 and Y F1, and a computer program for evaluation of F_F1\nwere taken from am report by R. K. Rosich and W. B. Jones 5 as\nm\nm\no\nH Fl = 165 + 0.6428 . X,\nY F1 = H_F1/4.0,\n=\nwith H F1 and Y F1 in km and X in degrees.\nm\nThe computer program algorithm to evaluate F F1 is\nF F2 = a (M,R) + b (M,R) cos X + C (M,R) cos2x,\na )=A(M)+U(M). = R,\nb (M,R)=B(M)+V(M) = R,\nc(M,R)=C(M)+W(M) R,\nwhere\nM is the month number (e.g. , January = 1).\nThe coefficients A, B, C, U, V, and W are then expanded in a Fourier\nseries in M:\n(30\n(M-1))\ncos\ncos\n}\nBij\nsin\n(30\n(M-1))\n,\nfor D Dj = A, B, or C, N = 2, and\nDj = U, V, or W, N = 3.\nThe coefficients aij and Bij were determined from a least squares analysis\nof F F1 data from 1954 to 1966, by the Institute of Telecommunication Science.\nC. The F2 Region\nThe F2 region is that portion of the ionosphere above the E and F1\nregions. The electron-density profile used for the F2 region is that proposed\nby R. B. Bent, et al. 1 The F2 region is divided into three sections -- lower\nF2, , middle F2, and upper F2 or topside. Each section has its own functional\nform and will be described separately.","362\n1. Lower F2 Region. This region extends from the lowest level of the\nF2 region up to the height of maximum ionization and has the following func-\ntional form:\n(4)\nwhere\n= Contribution to the electron density at a height h due to the\nNF2 (h)\nF2 region (el/m3),\n= Height of maximum ionization (km)\nH F2\n= 1346.92 - 526.40 M (3000) F2 + 59.825 M (3000)F2\n= Semithickness of layer which is a function of F F2 and local\nY F2\no\nand is obtained from graphs in Bent's paper.\nFOF2 and M (3000) F2, which depend upon local time, geographic position, and\nthe modified Rawer magnetic dip angle, are obtained from a computer program\ndeveloped by the Institute of Telecommunications which will be described in\nitem 4.\n2. Middle F2 Region. This region extends from the height of maximum\nionization up to a critical height at which the gradient of the middle F2\nregion F2 region equals the gradient of the electron density of the upper\nF2 region. The functional form for the electron density of the middle F2\nregion is:\n(5)\nwhere\ncrit1/ =\n(6)\nK1 = Attenuation coefficient of lower topside (see next section). .\n3. Upper F2 Region. This region extends from the critical height\nupward, and is divided into three equal height levels -- lower, middle, and\nupper topside. The functional form for the electron density is:\nH2\n(7)","363\nwhere\nK1'\nK2'\nK3\n= Attenuation coefficients which depend upon geomagnetic\nlatitude and are taken from graphs in Bent's paper,\nN1,\nN2\nN3 = Electron-density coefficients which are chosen so that the\nelectron-density profile is continuous at the boundaries\n(H crit' H1 and H2),\nAH =\nH1 = Hcrit + H,\nH2 = H1 + H,\n=\nm\n4. F -O F2 and M(3000)F2. F F2 is the critical frequency of the ordinary\nand MC\ncomponent of the F2 region, (3000)F2 is a factor which, when multiplied\nby FOF2, gives the maximum usable frequency for a direct transmission of\n3000 km, [MUF (3000) = M(3000) . F F2]. F F2 and M(3000)F2 are obtained\nfrom a set of numerical mapping coefficients and a computer algorithm given\nin a report by W. B. Jones, et al. 6\nEach function depends on local time, geographic position, and the modified\nRawer magnetic dip angle. The algorithm is the same for obtaining either\nM (3000)F1 or F F2; only the set of numerical coefficients differ. The\nO\nfollowing equations are used to find either M(3000)F2 or F_F2:\nH\n].\n(8)\n0)\n(1,\njT\n0)\n+\nbj\nsin jT\ncos\n,\nL\n(9)\n0),\n(10)\nGK(1,\nbj\nU\n0).\n2j-1,K\n.\nwhere\nl = Geographic Latitude,\n0 = Geographic Longitude,\nT = Local Time,\nUs,\n= Numerical mapping coefficients (one set for each F F2\nt\nand (3000)F2)\nGK(2, 0) = Geographic coordinate functions, a typical term is\nX n sin n n 0","364\nTan-1\nmodified Rawer magnetic dip angle,\nX\n=\n,\ncos\nI = Magnetic dip angle at 300 km and is a function of l and 0.\nSo(A, 0, T) = Either F F2 or M(3000)F2, depending upon the coefficient\nset Us,ti\nResidual Range Error\nIn a plasma such as the ionosphere, the refractive index can be approxi-\nmated by\n(11)\nfor frequencies above 50 MHz. For the purpose of this discussion, the 1/f\nterm involving the earth's magnetic field will be ignored. The Doppler cycle\ncount in this approximation becomes\n(12)\n,\nwhere all integrals are approximated by the integral along the geometric path,\nand the conversion factor, K, between the electron density N and squared plasma\nfrequency fp2 is 8.1 x 107 Hz2 / (electron/cm3). As can be seen in the third\nline of Eq. 12, the Doppler cycle count consists of a vacuum term proportional\nto f, a first order ionospheric correction term proportional to 1/f, and higher\norder terms.\nIf data are acquired at two different frequencies and the terms of higher\norder than 1/f were not present, then by algebraically combining the two signals\nappropriately the quantity ao, needed for navigation, can be obtained as is\nthe procedure in the NAVSAT navigation system. That is if\n(13)\n,\nrepresents single frequency Doppler data, then the combination of two equations\nfor the vacuum Doppler term yields\n(14)\naof2\n=","365\nThis is the two-frequency corrected count at frequency f2 and isolates the a\nO\nterm needed for navigation.\nIf the a3 term is retained, the two-frequency corrected Doppler count and\nionospheric correction count become\nf22\n(15)\n3\nThe residual range error will be the difference between the two-frequency\ncorrected count and the true vacuum count multiplied by the wavelength. This\nwill be defined as\nRRE\n12 (a O f2 - CTFC2'\n(16)\nC\n=\na3\n.\nf22f12\nThis is the amount that two-frequency Doppler data would overestimate the\nrange to the satellite.\nModel for the Residual Range Error at Ground Stations\nIn Section II, a numerical model for a global ionosphere was given. This\nmodel and the ARL/UT ray tracing program have been used to study the RRE at\nseveral real and fictitious station locations (Table II). . A generalized\nfunction for the RRE depending upon the local peak plasma frequency and the\nelevation angle of the satellite has been developed.\nTable II\nLocation of Real and Fictitious Stations\nLAT (°N)\nSTA\nLON (E)\n018\n76.5\n291.2\nW\n50.0\n0.0\n111\n39.2\n283.1\nX\n20.0\n180.0\nY\n-20.0\n180.0\n008\n-23.2\n314.1\nZ\n-25.0\n0.0\n019\n-77.8\n166.6\nThe ARL/UT ray tracing program gives data from which the value of RRE can\nbe obtained. A plot of the RRE vs Elevation Angle for one of the test stations\nis shown in Fig. 2. One sees a difference between that portion of the pass","366\n160\n140\n120\n100\n20173\nSetting\n80\n60\n40\nRising\n20\n0\n70\n0\n10\n30\n50\n90\nElevation Angle - Degrees\nFigure 2\nResidual Range Error (RRE) During Pass over\nStation Y at 0000 UT (Local Noon)\nAE-76-268\nJRC\nA109","367\n10\n0\n-10\n-20\n12\n13\n8\n9\n10\n-30\nF F\n(MHz)\nO 2\n-40\n-50\n(a)\nF F2\nas a Function of Latitude\nO\n10\n30\n50\n70\n90\n8\n9\n10\n11\n13\n70\nF F\n(MHz)\nO 2\nNote: F o F 2 is measured at\n50\nLocation of 500 km height\nof station-to-satellite line\n30\nof sight.\n10\n(b)\nF F2 as a Function of Elevation Angle at Station Y\nFigure 3\nFoF as a Function of Latitude (a)\nO\nand Elevation Angle at Station Y (b) at 0000 UT\nAE -76-269\nJRC\nA109","368\nduring which the satellite is rising and that portion during which the satellite\nis setting. A plot of latitude vs FOF2 near the station is given in Fig. 3a,\nand a plot of elevation angle vs FOF2 (over a point along the line of sight at\nan altitude of 500 km) is given in Fig. 3b. These graphs show a large variation\nof FOF2 during the pass; therefore, a normalization of the RRE with respect to\nFoF2 is suggested. As seen above, the RRE is to be proportional to SN2ds,\nand since N is proportional to (FoF2)2, we have\nRRE a (F F2*)4 (Slant Range)\n(17)\nThe data were normalized to an FOF2* equal to 10 MHz, and reanalyzed. The data\nfrom Fig. 2 are replotted in Fig. 7 using this normalization. Since the geo-\ngraphic and time variations are contained in the FOF2 a normalization with\nrespect to FOF2 should remove these effects and Figs. 4 through 8 show this\nto be true. These graphs show the residual range error at the same time\n(0000 UT) at various stations. A contour map of the FOF2 for the time used\nin Figs. 4-8 is shown in Fig. 9. The erratic behavior of the normalized RRE\nin Fig. 8 (Station Z) is due to the small values of the FOF2 and raw RRE at\nthis time which is local midnight at this location.\nFrom these graphs, a polynomial in the elevation angle appears to repre-\nsent the data to a very good approximation. The final form for the fitting\nfunction is\nRRE (cm) = (\n4\n4\na1x1\nCSC (E)\n(18)\ni=0\nwhere\nE = Elevation Angle,\nis the peak plasma frequency of the ionosphere at the latitude\nF F2*\nand longitude where the line of sight between the ground station\nand satellite cross the 500 km altitude.\nX = 1.0 - E/90.0,\na1 = a3 = 0.0,\nao = 6.863 cm,\na2 = -0.078 cm,\na4 = 35.127 cm.\nThe CSC (E) comes from the slant range in Eq. 17.\nA graph of this function with a plasma frequency equal to 10 MHz is shown\nin Fig. 10. The coefficients were evaluated using a least squares curve\nfitting program using the data from several stations.\nEquation 18 is strongly dependent on FOF2; therefore, as good a value as\npossible of FOF2 must be obtained. The numerical model proposed in Section II\ncan be used to calculate FOF2 values if other methods are not available. The","369\n160\n140\n120\n100\n80\n60\n40\n20\n0\n10\n30\n0\n5.0\n70\n90\nElevation Angle - Degrees\nNormalized Residual Range Error for a Pass over\nFigure 4\nStation 008 at 0000 UT\nAE - -76-270\nJRC\nA109","370\n160\n140\n120\n100\n80\n60\n40\n20\n0\nT\n90\n0\n10\n30\n50\n70\nElevation Angle - Degrees\nFigure 5\nNormalized Residual Range Error for a\nPass over Station 111 at 0000 UT\nAE -76-271 -\nJRC\nA109","371\n160\n140\n120\n100\n80\n60\n40\n20\n0\nT\n10\n30\n50\n0\n90\n70\nElevation Angle - Degrees\nFigure 6\nNormalized Residual Range Error for a\nPass over Station X at 0000 UT\nAE -76-272 -\nJRC\nA109","372\n160\n140\n120\n100\nRazaro\n80\n60\n40\n2.0\n0\n0\n10\n30\n50\n70\n90\nElevation Angle - Degrees\nFigure 7\nNormalized Residual Range Error for a\nPass over Station Y at 0000 UT\nAE-76-273\nJRC\nA109","373\n160\n140\n120\n100\n80\n60\n40\n20\n0\n0 10\n30\n50\n70\nElevation Angle - Degrees\n90\nNormalized Pass Residual Range Error for\nFigure 8\nover Station Z at 0000 UT\na\nAE-76-274\nJRC\nA109","60\n4\nUT\n4\n0\nContours of 2 in Units of MHz for September 1969 at 0000\n9\n5\n12\n9\n300\nLongitude East - Degrees\n13\n130\nFigure 9\n240\n12\n11\n5\n10\n7\n8\n12\n180\n6\n11\n120\n5\n6\n.\n5\n4\n4\n6\n60\n30\n90\n60\n0\n-30\n-60\n-90","375\n180\n160\nNRRE = } i=0 Iajxi 4 /sin (elv.\n140\nang.)\n= 1 - elv ang = zen ang\nX\n90°\n120\n90°\nao = 6.862\na = 0.0\n100\na2 = -0.0779\na3 = 0.0\n80\na4 = 35.127\n60\n40\n20\nI\nI\nH\n0\n0\n10\n30\n50\n70\n90\nElevation Angle - Degrees\nFigure 10\nModel Function of Normalized Residual Range Error\n(Scaled to a F OF2 * of 10 MHz) as a Function of Elevation Angle\nAE-76-276\nJRC\nA109","376\nglobal contour graph of FOF2 in Fig. 9 shows that away from the magnetic\nequator, FOF2 varies slowly with position and local time.\nThis function can be used to correct positions obtained from two-frequency\nDoppler data. A possible procedure is as follows:\n1. Determining the approximate position and the satellite trajectory\nas would usually be done.\n2. Find elevation angles at timing points.\n3. Find latitude and longitude at 500 km point.\n4. Fine FOF2 at that point.\n5. Evaluate the RRE at each point.\nThe value of RRE thus obtained is the amount that the range would be overestimated\nmated based on two-frequency corrected Doppler at that instant. The value of\nRRE at the timing points could then be used to plot a graph which could then\nbe used to adjust the pass data.\nReferences\n1. Bent, R. B., and P. E. Schmid, \"The Development of a Highly Successful\nWorldwide Empirical Ionospheric Model and Its Use in Certain Aspects of\nSpace Communications and Worldwide Total Electron Content Investigations\",\n1975 Symposium on the Effect of the Ionosphere on Space Systems and\nCommunications.\n2. Haydon, G. W., and D. L. Lucas, \"Predicting Ionospheric Electron Density\nProfiles\", Radio Science, 3, No. 1, pp. 111-119, 1968.\n3. Van Zandt, T. E., and R. W. Knecht, \"The Structure and Physics of the\nUpper Atmosphere\", Space Physics, ed. D. LeGalley and A. Rosen, (John\nWiley and Sons, Inc. N.Y., N.Y.) 1964.\n4. Watts, J. M., and J. N. Brown, \"Some Results of Sweep-Frequency Investiga-\ntions in the Lower Frequency Band\", J. Geophys. Research, 59, No. 1,\npp. 71-86, 1959.\n5. Rosich, R. K., and Wm. B. Jones, \"The Numerical Representation of the\nCritical Frequency of the F1 Region of the Ionosphere\", Office of\nTelecommunications Tech. Rep. 73-22, Oct. 1973, (U.S. Government Printing\nOffice, Washington, D. C. 20402).\n6. Jones, Wm. B., R. P. Graham, and M. Leftin, \"Advances in Ionospheric\nMapping by Numerical Methods\", N.B.S. Tech. Rep. No. 337, May 1966, (U.S.\nGovernment Printing Office, Washington, D. C. 20402).","377\nDEVELOPMENT OF DOPPLER ACTIVITY AT I.R.O.E.\nL. Ciraolo\nL. Mezzani\nIstituto di Ricerca sulle Onde Elettromagnetiche\nFirenze, Italia\nAbstract\nSince 1973 a Doppler tracking station for observation of NNSS satellites\nhas been set up at I.R.O.E., Florence. The station operation gave fairly\ngood results during the experimental Doppler campaign 1974 in Italy, and the\nfirst European Doppler Observation Campaign (EDOC) in May 1975 and since\nFebruary 1975 as TRANET cooperating station.\nSome experience of data reduction carried out during the Italian Doppler\nCampaign gave also promising results.\nCurrent developments of the station include reception of GEOS satellites\nand fully automatic operation of the station by computer control.\nIntroduction\nDuring the International Symposium on the Use of Artificial Satellites\nfor Geodesy and Geodynamics, Athens, 1973, we communicated that a Doppler\ntracking station had been set up at I.R.O.E., Firenze, and that we would\nhave welcome proposals of collaboration from the international scientific\ncommunity.\nSeveral collaborations, in which we took part enthusiastically, were\noffered to us together with technical suggestions and scientific advises\nthat were precious in improving our instrumentation and in obtaining some\ninteresting scientific results.\nIn the following we will review such activity trying to emphasize the\nvarious related aspects concerning the instrumentation, the station opera-\ntion, the scientific cooperations and the future developments.\nGeographical Location\nBoth antennas for 150-440 and 162-324 MHz of our Doppler station are\nlocated upon the tower of the Institute, as shown in Fig. 1, at a height\nof approximately 47 m upon the ground and 101 m upon the sea level. Each\none of these two antennas is mounted on its own mast fixed to the roof of\nthe tower itself.\nReferring to Fig. 1, point A2 is 3.010 m far from A1 at 91°32'10\" from\nNorth towards East i.e. about in direction East. The coordinates of point\nA1 and those of a point B on the same vertical of A1 but 2.8 m higher (and\nso about corresponding to the electrical center of the antenna) have been\ndetermined by Istituto Geografico Militare Italiano (I.G.M.I.) in the\nEuropean Datum (ED50 reference frame) by means of a proper set of","378\n162-324 MHz\n150-400 MHz\nANTENNA\nANTENNA\nB\n-\nIA?\nScale 1/50\n(All lenghts in mm)\nAll\n3010\n1A2\nFIG. 1","379\ntriangulations connected to bases of our national geodetic network. These\ncoordinates are indicated in the Table 1.\nTable 1\nPoint A1\nPoint B\nX = 4 522 483\n4 522 485 m\nY =\n898\n097\n898 097 m\nZ = 4 392 603\n4 392 605 m\nThe horizon viewed from the antennas is substantially free from\nobstacles able to shield radio signals from satellites, apart from Monte\nMorello that occupies a part of the horizon itself which is limited, in\nelevation, to a maximum of 6.5 degrees, as shown in Fig. 2. So only parts\nof satellite trajectories can be shielded which are lying within elevation\nvalues lower than 10 degrees, normally considered to be not of interest for\nreasons of tropospheric propagation.\nThe Institute is just in the middle of the Industrial Area of Florence.\nThis caused some doubt during the installation of the station, due to the\npossibility to have too much radio noise or disturbances that could affect\nthe quality of the data. The following operative experience has shown that\nas concerns the quality of the data, the location is satisfactory, and that\nsome trouble may occasionally occur in the satellite acquisition due to\nstrong disturbances that cause a wrong locking of the receiver channels.\nInstrumentation\nIn this paragraph, we will describe the instrumentation, for precise\nDoppler tracking, now available at I.R.O.E. Part of this instrumentation\nhas been or is actually operating, namely the system for 150-400 MHz opera-\ntion; the rest is of new acquisition and is being assembled, in order to\nimprove the performance of the station, allowing the reception of GEOS\nsatellites and a more complete automatization of the required operations.\nIt follows a list of the basic blocks of the instrumentation.\na) Receiving system for 150-400 MHz operation\nTwo identical systems are available, manufactured by ELECTRAC and\nincluding antenna with preamplifier and receiver.\nThe receiver is designed for the reception of signals at 150 and\n400 MHz with an offset of -80 ppm (Zo mode) and therefore is able to receive\nonly Navy Navigation satellites. Operation at different offsets is on\nprinciple possible changing properly the 5 MHz reference frequency fed to\nthe receiver, but likely not practical as concerns data processing.\nThe operation of the receiver can be either manual or automatic.\nIn the automatic mode it sweeps continuously a frequency range in which the\nsignals of rising satellites are expected (sweep mode) and locks on them if","NORTH\n3 PO\nAzimuth (Degrees)\nCareline\n330\n300\nWEST\n270\n240\nHORIZON\n210\nELEVATION PROFILE\nFROM THE ANTENNAS\nFIG. 2\nSOUTH\n180\nrediccalls\n80*52'18\"\n150\n29.09'46\"\nDUORO\n120\nEAST\n86°54'36\"\nmater\nJ.Francesco\nFIESOLE\n90\nAntenna RAI\nSO\n30\nM. Marcise\nNORTH\n0\n11\n10\n9\n8\n7\n6\n5\n4\n3\n2\n1\n0\n-1","381\nthey have a sufficient strength (around -150 dBm nominal) in case of\n\"drop lock\", the frequency of the receiver is swept at the average Doppler\nrate so to coast the lost signals (coast mode). If acquisition does not\noccur, the receiver reverts to the sweep mode.\nThe occurrence of such modes is monitored by status outputs and\nlamps that are very useful in the control of the operation of the Doppler\ndigitizer. The external control of the receiver is limited to few opera-\ntions: acquisition reject and control enable, for which two control inputs\nare provided.\nb) Receiving system for 162-324 MHz operation\nThis system, including antenna, preamplifier and receiver, has\nbeen manufactured by ELECTRAC too.\nThe circularly polarized antenna allows hemispherical coverage for\nreception of both channels, avoiding the dip otherwise occurring when the\nsatellite has an elevation near 90° The received frequencies range from\n161.950 to 162.000 MHz (low channel) and 323.900 to 324.000 MHz (high\nchannel), providing a range of offsets not limited to the Y O mode (-50 ppm). .\nThe receiver is designed to be computer controlled and a variety of\ndigital data, status and control inputs and outputs are provided that allow\noperations as setting or monitoring the center frequency of the VCO,\nenabling or disabling the search and lock-on capability, and so on.\nc) Doppler digitizers and station clock\nTwo types of Doppler digitizers and station clocks are available,\ndiffering in the operation and in the format of the output data, although\nboth perform an integrated Doppler measurement. The first type, of which\ntwo models are available, provides two modes of operation, the data acqui-\nsition mode and the manual mode. In the data acquisition mode it records\nthe number of Doppler cycles occurring in a time interval, whose nominal\nduration is 20 seconds, and the final epoch of the interval itself in\nseconds and microseconds of the day. These data are punched on a 7-level\npaper tape. In the manual mode, digits entered by a keyboard can be punched.\nThe operation of this digitizer had to be attended, and only recently it\nhas been modified in order to provide automatic acquisition of the data\nduring a satellite pass and physical separation of the passes on the paper\ntape. The circuitry to perform these operations is driven by the status\noutputs of the 150-400 MHz receiver.\nThe second type of digitizer has been designed to meet the specifi-\ncations of the TRANET activity. So we will refer to it as the TRANET digi-\nzer. It is a homemade device recording on a 5-level paper tape, standard\nteletype code, the epoch (in seconds and microseconds of the day) at which\na preselected integer number of Doppler cycles is counted. The number of\nDoppler cycles to be counted, can be selected among 217, 218, 219, 220.\nThe digitizer provides automatic acquisition of the data during a pass and\nphysical separation between contiguous passes under the control of the status","382\noutputs of the receiver. A fiducial time mark input is also provided, that\ncauses the print-out of the epoch at which a pulse is fed to it, but substi-\ntuting the most significant digit of the seconds with the digit \"9\".\nd) Time code generator\nThe time code generator is able to program the switching of a relay\nat a predetermined time (hours, minutes, seconds) of a day of the week. The\nprogrammable events are ten.\ne) Beep word detector\nThe beep word detector, designed and built at I.R.O.E., is able to\noutput a pulse related to the time of arrival of the fiducial time mark from\nthe Navy Navigation satellites. Its basic operation is the following: a\nsquare wave, synchronized by the doublet rate, is generated by an integrated\nphase-lock loop; this drives a circuitry that detects the occurrence of the\nfirst doublet of the message immediately following the beep word, enabling\nthe front of the square wave itself to output a pulse.\nThe performance of this beep word detector is not satisfactory, as\nthe reconstructed doublet rate presents jittering fronts producing a standard\ndeviation of the individual time points of about 100 usec. Therefore, it is\nplanned to modify or to substitute the device as soon as possible.\nf) Computer\nThe computer is a NOVA 3/12 model manufactured by DATA GENERAL. The\nsystem provides a 16 K memory, I/O interface, teletype and real time clock.\nAs concerns the operation of the station, the most interesting feature is\nthe real time clock, that allows to program events or to execute specified\nroutines at a preselected epoch.\ng) Time and frequency standards\nA time and frequency standard laboratory is installed at I.R.O.E.\nIt is equipped with two Cesium clocks, compared to Loran-C transmission of\nthe Mediterranean chain, providing all the needed frequency and time signals\nwith accuracy required by the Doppler station.\nTwo good performance quartz clocks are also available for campaign\noperation: their control can be carried out by VLF comparison or similar\nmethods.\nh) Other facilities\nMost of the electronic instrumentation for troubleshooting and\nrepair of the Doppler station is available at I.R.O.E., together with the\nassistance of skilled personnel. Among the available facilities it is worth\nmentioning a little computing center equipped with an ECLIPSE S200 computer,\ndisks, magnetic tapes.","383\nOperation\nAvailing of the described instrumentation, various configurations of\nDoppler tracking systems can be set up, differing about the details of opera-\ntion and the format of output data. It will follow a description of the\nconfigurations that have been or are in operation and of the new ones that\nare being set up by the lately acquired instrumentation.\nThe first experiments were carried out assembling two identical systems,\neach one composed by a 150-400 MHz receiver and a \"first type\" digitizer as\ndescribed in paragraph 3 point c). The described configuration required\nattended operation, as the operator had to print manually an identification\nmessage for the observed pass and to switch the digitizer on the data\nacquisition mode during the pass itself, as monitored by the \"locked channel\"\nlamps of the receiver.\nThe two systems were tested in June 1973 obtaining a set of data of\nsatisfactory quality from the observation of the satellite 30140, and after\nthey were used in an experimental Doppler campaign from May to early August\n1974. One system was operated at I.R.O.E., the other in four sites of the\nItalian geodetic network, arranging to obtain as more as possible simultaneous\nobservations.\nIn spite of the logistical difficulties connected to the attended opera-\ntion, good results were obtained also from these observations.\nThe second configuration was set up assembling one of the two 150-400\nMHz receivers and the TRANET digitizer described at paragraph 3 point c).\nApart from successive improvements, it has been continuously operating since\nAutumn 1974.\nA substantial improvement was obtained due to the possibility of semi-\nautomatic operation, as the passes were automatically recorded and separated\nby a tail of blanks on the output tape under the control of the status outputs\nof the receiver. The tapes must be prepared for the following use: first to\npick up the required passes, second to provide them with an identification\nmessage (i.e. a TRANET header) this job is carried out by the operator,\nthat obtains a teletype printout of the tape in order to select a pass\naccording to its rise time, then punches manually the identification message.\nA disadvantage of this configuration was that, in case of conflicting\nsatellite rising before the requested one, this was missed as the receiver\nlocked on the first one. To avoid this or, better, to reduce the occurrence\nof missed passes because of conflicts, the time code generator was added to\nthe configuration with the task of enabling the acquisition reject input of\nthe receiver at the expected rise time of the requested pass. This causes\nthe rejection of any acquisition and reverting the receiver to the search\nmode: in this way about 80% of passes that would be missed for conflicts\ncan be normally observed.\nIt was planned to add to this configuration the receiver for 162-324\nMHz and a logical control unit so to be able to observe also the GEOS","384\nsatellites, limiting the operation to the semiautomatic mode. The availability\nof a computer suggested the possibility to provide fully automatic operation,\nso to set up a new versatile configuration. This configuration will be com-\nposed by one receiver for 150-400 MHz, the receiver for 162-324, the TRANET\ndigitizer, the computer and other auxiliary circuitry in development (inter-\nface between computer and digitizer).\nIt is planned that the station operator will have only to provide instruc-\ntions (as data for the computer programs) and to take away the tapes ready\nfor use (transmission or analysis) The attainment of this requires a series\nof programs able to perform a lot of operations, as:\n-- control and monitoring of the receivers;\nswitching the Doppler signal from the 150-400 MHz receiver, or from\nthe 162-324 MHz one, to the Doppler digitizer;\n--- selecting the proper count number on the digitizer according to the\nswitched receiver;\n-- automatic print out of identification messages, recording count\nnumber, day of the year and any required item;\nreduction of missed passes for conflicts (the described simple\n--\ntechnique for the 150-400 MHz receiver and a more sophisticated one\nfor the 162-324 MHz receiver);\nrecording of all the operations performed in order to provide a log\n--\nprinted on the teletype.\nIt is planned to set up the hardware of this configuration within 1976;\nas concerns that software, a longer time will be needed in order to be able\nto run the station without interruptions during the check of the programs,\nthat will be written gradually and modified in order to obtain the best\nperformance.\nIt is worth mentioning that the \"first type\" digitizers have been\nmodified in order to provide semiautomatic operation. One of them and the\nsecond 150-400 MHz receiver will be assembled to realize a Doppler system\nwhose operation, apart the format of the output data, will be identical to\nthe second configuration described in this paragraph.\nAs concerns the station of Firenze, its operation is attended by four\npersons, two scientists and two technicians (one technician at 50%). This\ngroup provides operation, data transmission, maintenance, and scientific\nutilization of the data.\nAt present, the job requiring most time is the cooperation to the\nTRANET activity, due to the semiautomatic operation of the station. As\noutlined in this paragraph, this activity requires planning of the observa-\ntions according to the OBSINST, inspection of the tapes to select the\nrequested passes, manual printing of header and terminator, data transmission\nvia commercial telex to Capodichino (Napoli) (that operates as a link sending\nthe data to SCC via Autodine), log and report preparation. Wishing to\nspend more time in scientific investigations, it seemed that the only way to\nfollow was a fully automatization of most of the needed operations.","385\nData processing and analysis\nThe first computations on Doppler data were carried out at I.R.O.E. in\n1973 with the two main purposes of testing the performance of the equipment\nand of exercising in the techniques of handling and processing the Doppler\ndata themselves. Very simple programs were written for this task, similar\nto the programs used in navigation to make a fix. The main difference was\nthat to compute the satellite positions, the NSWC precise ephemeris was\nused instead of the broadcast one. For each pass, the station longitude\nand latitude and the satellite frequency were estimated according to the\nmethod of least squares. No tropospheric correction was taken into account.\nThese programs were effective in detecting an equipment improper func-\ntioning (jittering of the edges of the 20 sec gate) and solved satisfactorily\nthe intended purposes.\nThe following purpose was to improve the programs in order to provide\na satisfactory method of data filtering and to obtain the first geodetic\nresults processing the data obtained in the Italian campaign of Spring-Summer\n1974.\nThe preliminary results of the campaign were reported at the 16th\nGeneral Assembly of the International Association of Geodesy, and looked\nexcellent from a geodetic point of view.\nSome problems connected to the processing has been left open: first,\nif the adopted method of data filtering is more or less effective of the\nGuier's one; second that the filtered noise resulted one order of magnitude\nabout larger than the noise reported by SAR of NSWC. The investigations\nconcerning these points have been delayed by the substitution of the computer\nat I.R.O.E., but they will be begun again as soon as the programs will run\non the new system.\nAs concerns the future, it is planned to write more sophisticated pro-\ngrams for geodetic investigations, and to develop a series of facilities\nallowing a versatile way of format conversion in view of other collaborations\nCooperative activities and results\nJust after the Symposium of Athens, we performed a check of the station\ndescribed in that Symposium, as said in paragraph 5. This check was made\nby observing several passes of 30140 satellite in the period June-July 1973\nand processing the data obtained by means of those observations. The check\nitself has been made possible by the kind collaboration of the U.S. Naval\nSurface Weapons Center which provided us alerts of the satellite to be\nobserved and its ephemeris for the observed passes. Processing of the\ncollected data gave rather good results and allowed us to perform the\ndigitizer improvement mentioned in paragraph 5 (above).\nAn experimental Doppler campaign was carried out in Italy, in the\nperiod May-August 1974, in cooperation with the Istituto Geografico Militare\nItaliano, by using both stations with the improved digitizers. The observed","386\nsatellite was 30190. One station remained fixed in Firenze and the other\none occupied four sites of the Italian geodetic network (Trieste/Opicina,\nOria, Catania/Etna, Cagliari) successively. Alerts and ephemeris, for\nprocessing of the collected data, have been provided by U.S. Defence Mapping\nAgency. That processing has been performed by us in 1975 and has given\nquite good results.\nIn the same period the digitizer for TRANET operation was completed and\nits check was carried out by the Applied Physics Lab., , to which data collected,\nby observing 30190 satellite at Florence station, had been passed. This\ncheck gave good results and so allowed us to begin our TRANET activity in\n1975 as Doppler Station 641.\nAs cooperating TRANET Station, we have had the chance to compare the\n94 pass solution for the point positioning of Firenze, found by processing\nthe data collected during the campaign of 1974, and a 64 pass solution\nfound by NSWC in 1975 by processing data collected during the TRANET activity.\nThis comparison showed a very good agreement between the two solutions, as\nconcerns either the sets of determined coordinates or the standard deviation\nof the residuals.\nIn 1974, a collaboration began between us and the Working Party on\nGeodynamics of the Council of Europe and so, in 1975, we participated in the\n1st EDOC Doppler campaign with our TRANET instrumentation together with the\nother five European Stations: Barton Stacey (U.K.), Uccle (Belgium),\nGrasse (France), Wettzel (German Federal Republic), Uppsala (Sweden). As\nknown the processing of the data collected during this campaign was carried\nout by the Group de Recherches de Geodesie Spatiale by using ephemeris of\nNSWC.\nThe EDOC solution for the point positioning of Firenze is shown in the\nTable 2 together with the coordinates of our antenna (point B of Fig. 1)\ndetermined by I.G.M.I. in the ED50, the solution obtained by Italian campaign\nof 1974, the solution obtained by NSWC in 1975 and the DARCUS solutions of\nNSWC itself, for the normal TRANET activity, for the days 150-179 of 1976.\nTable 2\nCoordinates\nof\nFlorence Station\nED50\nITALIAN\nNSWC\n1st EDOC\nDARCUS\nCAMPAIGN\nSOLUTION\nCAMPAIGN\nSOLUTION\n1974\n1975\n1975\n1976\nX = 4 522 485.0\n4 522 410.4\n4 522 410.1\n4 522 411.2\n4\n522\n410.8\nm\nY =\n898\n097.0\n897 984.2\n897 984.6\n897 985.8\n897\n985.9\nm\nZ = 4 392 605.0\n4\n392\n484.0\n4\n392\n484.6\n4 392 481.7\n4\n392\n484.5\nm","387\nOne can see that, apart from ED50 determination, the other four solutions\ndiffer each other only for 2.9 m maximum, that seems to show a good agreement\nbetween these solutions themselves, notwithstanding the fact that the data,\nfrom which they have been derived, had been collected on different times and,\nas concerns the campaign of 1974, by means of different instrumentation. The\n\"ED50 solution\" shows with evidence the difference between ED50 and NSWC\nreference frame.\nFinally, a Convention has been performed in the last weeks between our\nInstitute and the International Astronomical Station for Latitudes of\nCagliari (Italy), to which I.R.O.E. will lend one of its two Doppler stations\nwith a digitizer of the first type in order to initiate a cooperation with\ngeodynamical purposes. People of Cagliari will operate our Doppler station.\nI.R.O.E. will be allowed to utilize the Doppler data collected at Cagliari.","388","389\nCOMPARISON OF DOPPLER DERIVED UNDULATIONS\nWITH GRAVIMETRIC UNDULATIONS CONSIDERING\nTHE ZERO-ORDER UNDULATIONS OF THE GEOID\nRichard H. Rapp\nReiner Rummel\nDepartment of Geodetic Science\nThe Ohio State University\nColumbus, Ohio 43210\nAbstract\nGravimetric geoid undulations and geoid undulations determined from\nDoppler derived station coordinates are compared using a new zero-order undu-\nlation of the geoid expression. Two sets of stations are used: The first\nconsisting of 72 Geoceiver stations in the United States; the second consisting\nof the 40 stations located at the globally distributed BC-4 camera sites. For\nthe U.S. stations gravimetric undulations were computed using the GEM 8\npotential coefficients and 1° X 1° mean free-air anomalies (which incorporated\nan atmospheric correction), in a spherical cap of 20° in radius about the\nstation. For the global station net, the undulations were computed from the\nGEM 8 coefficients alone. A comparison of these gravimetric undulations with\nthe undulations implied by the Doppler derived station coordinates (after\napplying a 1 ppm scale reduction) can reveal origin shifts of the Doppler\ncoordinate system with respect to the center of mass of the earth, and a\ncorrection to the adopted equatorial radius. The origin shifts are not well\ndetermined from the U.S. stations because of their limited distribution.\nHowever the global station net comparison indicated origin shifts at the\n1 + 2 m level indicating the Doppler origin is close to the center of mass of\nthe earth. The equatorial radius implied by each set of stations if 6378135\n+ 2 m.\nIntroduction\nGiven the rectangular coordinates of a point in some defined system, it\nis possible to compute the geometric geoid height of this point with respect\nto a defined reference ellipsoid if we know the orthometric height of the\nstation. This goemetric undulation may be compared to a gravimetric geoid\nheight which may have been computed from potential coefficients, or potential\ncoefficients combined with terrestrial gravity material. Such comparisons\nmade over a wide distribution of stations can be used to infer information\nconcerning the equatorial radius of the earth, and the location of the origin\nof the rectangular coordinate system with respect to the center of mass of\nthe earth. This type of comparison is not new having been recently used,\nat least in part, by Rapp (1974), Gaposchkin (1974), Smith et al. (1976),\nStrange et al. (1975), and Vincent and Marsh (1975).\nThe primary purpose of this paper is to investigate the case when the\ngravimetric undulations have been computed from a combination of terrestrial\ngravity data and potential coefficient information. We specifically are\nintroducing into the computations a new zero order undulation term, and\nincluding the atmospheric effect in the computations of the undulations.","390\nDoppler Undulations\nThe term Doppler undulations is used to describe those undulations\nderived from station coordinates determined through the Doppler satellite\npositioning system described by Anderle (1974), and Strange et al. (1975).\nLet the rectangular coordinates of a point in the Doppler system be XD,\nYD, and ZD. Let the height of this point above a defined ellipsoid be hp,\nand let the height of this point above mean sea level be H. Then the Doppler\nundulations are:\n(1)\nND = hD - H\nGravimetric Undulations\nUsing potential coefficients and terrestrial gravity anomalies, the\ngravimetric geoid undulations can be computed from (Rapp and Rummel, 1975,\np. 5)\nl\nSS\nmax\nR\nR\n(2)\nAg°\nS(4)do\nOL(40)A8l\n=\n+\n2Y\nOc\nl=2\nwhere:\nR\nmean radius of the earth;\nY\naverage value of gravity over the earth;\nOc\ncap surrounding the computation point at\nwhich N is to be computed and with in\nwhich gravity anomaly data is known;\nAg°\napproximately the free-air anomaly;\nS (4)\nStokes' function;\ndo\nelemental area in which Ag° is given;\nae(40)\nMolodenskii's truncation function (Heiskanen\nand Moritz, 1967, p. 260) which is a function\nof the degree l and angular cap radius, 40,\nof Oc\nThe quantity Age is the l'th degree component of the anomaly field and can\nbe written as:\nl\nGM\nF\n(3)\nAge=\n(l-1)\n(C* lm cos ml + S lm sin m ) Plm (sin (p)\nwhere:\nG\ngravitational constant;\nM\nmass of the earth;\ngeocentric radius to the elevation\nr\npoint;","391\n-\n4, l\ngeocentric latitude, and longitude at the\nevaluation point;\nPlm\nfully normalized associated Legendre\npolynomials;\nlem - cref lm\nC*\n=\nlm\nCref\npotential coefficients for the reference\nlm\nellipsoid of degree l=2, , 4, and m=0;\nClm' S lm\nfully normalized potential coefficients;\nl\nmaximum degree of given potential\nmax\ncoefficients.\nNO is the zero-order undulation of the geoid and is given as (Rummel and Rapp,\n1976)\nNo = 8a(1++2() ) - CM &(YO) G M\n(4)\nwhere:\nda = a - a, where a is defined to be the equatorial\nradius of the mean earth ellipsoid and a is\nthe equatorial radius of the adopted reference\nellipsoid;\nSM = M - M, where M is the mass of the earth\n(excluding the atmosphere) and M is the\nmass (excluding the atmosphere) of the\nadopted reference ellipsoid.\nThe quantity (40) is defined to be:\nyo\n(5)\nS(4) siny dy\nNumerical values for this quantity are given by Lambert and Darling (1963,\np. 115). .\nThe gravity anomaly term Ag° is given by (Moritz, 1974, p.3) :\n48° = 48 - E C\n(6)\n-\ni=1\nwhere:\nAg\nsurface free-air anomaly;\nG1\natmosphere correction term;\nG2\ntopographic correction term;\nG3\nellipticity correction term.","392\nIn the computations carried out for this study only the G1 term has been\nincluded. The effect of neglecting the G2 term is near zero in flat areas\nbut may reach about 1 m in mountainous areas. The effect of neglecting the\nG3 term causes errors on the order of 0.3 m.\nThe geoid undulations computed from (2) will refer to an ellipsoid whose\ncenter is at the center of mass of the earth. The flattening of the ellipsoid\nwill be that used in determining the gravity formula used for the computation\nof the gravity anomalies, and the reference potential coefficients. The size,\nor equatorial radius of the reference ellipsoid will be known but the N term\nO\nwill not be known unless the equatorial radius of the mean earth ellipsoid\nis known as well as the true GM value.\nTheoretical Comparison of Doppler and Gravimetric Undulations\nLet XG, YG, ZG be the rectangular coordinates of a point with respect to\nthe center of mass of the earth. Let XD, YD, ZD be the corresponding coor-\ndinates in the Doppler system (to be defined more precisely later). Assuming\nthe two coordinate systems are parallel we can write:\nAx\nXG\nXD\n(7)\n+\nAy\nYG\n=\nYD\nAz\nZG\nZD\nwhere Ax, Ay, Dz are the coordinates of the Doppler origin with respect to\nthe center of mass of the earth. To refer the Doppler undulations to a center\nof mass system we write:\n(8)\nND (G) = + AN (Ax, Ay, Az)\nwhere (Heiskanen and Moritz, 1967, p. 213)\n(9)\nAN = COSY cosh Ax + COSY sin Ay + sinpAz\nwith Q being the geodetic latitude. Under ideal circumstances we would have\nNG = ND (G) provided all needed quantities are known and there are no observa-\ntional errors. We express this equality by writing:\n(10)\nNg = No + N = Ng (G) = ND + AN(Ax, Ay, Az)\nwhere N is the sum of the 2nd and 3rd terms on the right side of (2) Using\n(9) we can write:\n(11)\n-No + cost cosi Ax + cosp sinAAy + sin6 Az = N - ND\nThe quantities considered unknown in this equation are No, Ax, Ay, and Dz.\nThe known quantities are N (computed from potential coefficients and gravity\nanomalies) and ND computed from (1) on the basis of rectangular coordinates\nand a defined reference ellipsoid.","393\nGiven a set of stations, equation (11) can be solved in an adjustment to\ndetermine the unknowns. Once No is determined the equatorial radius of the\nmean earth ellipsoid can be determined from (4) provided G S M is known.\nComputations and Results\nComputations were carried out with two sets of stations for which the\ncoordinates in the Doppler system have been derived. The first set consists\nof approximately 70 stations in the United States (Strange et al., 1975) while\nthe second set is the 40 Doppler stations located at the BC-4 camera sites\n(Anderle, 1974) which are globally distributed.\nThe data in the Strange et al. paper of use here consisted primarily of\nthe latitude, longitude and height of 74 stations given with respect to an\nellipsoid having a = 6378145 m and f = 1/298.25. These coordinates are given\nin the NWL 9D coordinate system. The mean sea level heights for 69 of the\nstation marks were provided by Strange (1975, personal communication). Mean\nsea level heights for three other stations were found from other sources so\nthat a total of 72 stations were available for this computation. No H values\nwere found for stations 51081 and 51082. For nine stations (53002, 51039,\n51048, 51052, 51103, 51123, 51124, 55126, and 51127) the ellipsoid height\ngiven in the Strange et al. paper needed to be reduced to the level of the\nstation marker by subtracting the elevation of the tracking equipment refer-\nence point above the station marker.\nGiven this information the rectangular coordinates in the NWL 9D system\ncan be computed. However, for consistency with length measurements by other\ntechniques (ground measurements, VLBI techniques, and lunar laser data) it is\nnecessary to scale down the NWL 9D coordinates. This scale reduction has been\ndiscussed by several authors including Strange et al. (1975) and Anderle (1974).\nFor the purposes of this paper we adopt the results given by Strange et al.\nwhereby the NWL 9D coordinates were reduced by a factor of 1.0 (+ 0.2) ppm.\nThe original 6, 1, h given by Strange et al., were converted to X, y, Z\ncoordinates using the given reference ellipsoid. These coordinates were then\nmultiplied by (1- 1x10-8). The resulting coordinates were then converted\nback to 4, 1, h with respect to an ellipsoid whose a = 6378142 m and f = 1/298.255.\nThese parameters are the same as adopted for use in the computation of the\ngravimetric undulations. Subtracting the given mean sea level height from\nthis ellipsoid height yields the ND values.\nNext the gravimetric undulations (or N) were computed using equation (2).\nThe GEM 8 potential coefficients (Wagner et al., 1976) taken to degree 30 and\n1° X 1° mean anomalies within a cap radius of 20° about the station were used.\nIn addition to a = 6378142 m, and f = 1/298.255, a GM of 3.986009 X 10 m 3\n/\nsec was used.\nThese values of N and ND were used in an adjustment with equation (11).\nTwo solutions were made: one where all 4 unknowns were solved for; and a\nsecond solution where Ax, Ay, Az were constrained to be zero. The results\nare given in Table 1.","394\nRMS\nNO\nAz\nResidual\nAx\nAy\n- -9.4 + 8.7\n-9.9 + 8.4\n-13.6 + 11.6\n+ 1.7\nSolution One\n-4.8\n+\n1.3\n+ 2.4\n0\n-11.9 + 0.3\nSolution Two\n0\n0\nTable 1\nParameter Estimation Using 72 Geoceiver\nStations in the United States\n(meters)\nBecause of the limited region in which the Doppler stations are given the\norigin shifts are not well determined. In fact the correlation coefficients\nbetween certain of the parameters reaches 0.99 and thus the first solution\nshould be regarded as unsatisfactory. The value will be discussed later.\nThe analysis of the second data set was carried out in a similar fashion\nas above. The data for the 40 stations from Anderle (1974) was used with the\n1 ppm scale reduction applied. The gravimetric undulations (N) were computed\nsolely with the GEM 8 potential coefficients. Again two solutions were\nobtained with the results given in Table 2.\nRMS\nN O\nAz\nResidual\nAx\nAy\nSolution One\n-1.1\n+\n1.6\n1.6\n+\n1.6\n0.6\n+\n1.8\n-6.9 + 1.0\n+ 6.1\n-6.8 + 1.0\n+ 6.3\nSolution Two\n0\n0\n0\nTable 2\nParameter Estimation Using 40 Doppler Stations\nLocated at the Globally Distributed BC-4 Stations\n(meters)\nThe small values of Ax, Ay, Az found in solution one indicates that (at least\nwith this data) the origin of the NWL 9D coordinate system is essentially at\nthe center of mass of the earth. The same conclusion was reached by Anderle\n(1974) when similar computations were performed with the SAO Standard Earth II\npotential coefficients.\nThe Implied Equatorial Radius\nWe now can use the NO values given in Tables 1 and 2 to solve (4) for da\nand thus find an estimated equatorial radius for the mean earth ellipsoid.\nFor the case of 4 unequal to 0° (i.e. for the computations made with the\nU.S. stations) we used G M = -4 X 8 m 3 /s 2 which follows from considering the\nbest GM to be 3.986005 X 101 3 /s 2 (Moritz, 1975) The results are given\nin\nTable 3.","395\nG&M= -4x1083/s 2\nStations\nG&M=0\n72 in the U.S.\n6378135.4m\n6378134.0m\n40 globally\n6378135.2m\n6378135.2m\nTable 3\nEquatorial Radii Implied By the Doppler Stations\nThe agreement between the radius implied by the U.S. stations and the\nglobal stations is quite good. If the atmospheric correction had not been\nconsidered in the computations of the gravimetric geoid undulations, and if\nthe NO term had incorrectly been taken to be 8a, an equatorial radius approx-\nimately 7.6m smaller than that implied from the U.S. stations would have been\nfound. These are some of the reasons that earlier computations with data of\nthis type found equatorial radii that are too small.\nThe accuracy of these equatorial radii determinations is computationally\ndifficult because of the error correlations between the Doppler stations and\nbetween the gravimetric undulations at the stations in the United States.\nHowever, an approximate estimate can be obtained for the equatorial radius\nestimated on the basis of the U.S. stations using the following error\nestimates: scale accuracy (+ 0.2 ppm); gravimetric geoid undulation accuracy\n(+ 1.5 m); GM accuracy (+ 3.10 m3/s2 and Doppler height accuracy (+ 1.5 m)\nUsing this data with equation (4) the accuracy of the estimated equatorial\nradius from the U.S. Doppler stations is + 1.7 m.\nSummary and Conclusions\nThis paper has shown the procedure for the comparison of Doppler undula-\ntions and the undulations implied from potential coefficients, or a combina-\ntion of potential coefficients and 1° X 1° mean gravity anomalies. This\ncomparison depends on the evaluation of a zero-order undulation term that is\ndependent on the size of the cap within which terrestrial gravity material is\nused.\nComputations were made with 72 stations in the United States where undu-\nlations were computed with the GEM 8 potential coefficients and 1° X 1°\nterrestrial gravity data, and with 40 stations having a global distribution\nwhere undulations were computed only with the GEM 8 coefficients. Solutions\nwere made to determine an origin shift of the Doppler station origin with\nrespect to the center of mass. However, the stations in the United States\nwere too close to provide a reliable determination of these shifts, while\nthe global networks implied small shifts on the 1 meter level which were not\nsignificantly different from zero.\nThe equatorial radius implied by the 72 stations in the U.S. (with respect\nto a best GM) was 6378134.0 m (+ 1.7 m) while the radius implied by the global\nnetwork of stations was 6378135.2 m, both cases assuming the Doppler origin\nis at the center of mass of the earth.","396\nWe finally note that Lachapelle (1976) reported an equatorial radius of\n6378129.9 m implied by a set of 140 Doppler stations in Canada when the gravi-\nmetric undulations were determined from the GEM 8 potential coefficients alone.\nA similar computation was performed by us with the U.S. Doppler stations and\nan equatorial radius identical to that found by Lachapelle was found. This\nradius differs by 5 meters from the results described earlier in this paper.\nThe reason for this discrepancy is not known. Alternate forms of the No\nexpression may be used to determine alternate equatorial radii depending on\nadopted mean earth ellipsoid parameters. However such parameters (such as\nequatorial gravity) may not be sufficiently known to justify their adoption.\nIn addition there may be a systematic error in the geoid undulations from\nGEM 8 alone, for the limited geographic areas of the United States and Canada,\ncaused by the neglect of high degree information. Such error would be expected\nto average out when a global set of stations is analyzed.\nThe main thrust of this paper has not been to develop new estimates of\nellipsoid parameters. We have attempted to show the proper way to incorporate\nthe N term in equatorial radius determinations. Discrepancies that exist in\ncertain computations must be resolved by further study.\nAcknowledgement\nThis study was supported, in part, through Air Force Contract No. F19628-\n76-c-0010, The Ohio State University Research Foundation Project 4214B1. The\ncontract covering this research is administered by the Air Force Geophysics\nLaboratory, L.G. Hanscom AFB, Mass., Mr. Bela Szabo, Contract Monitor.\nReferences\nAnderle, R., Transformation of Terrestrial Survey Data to Doppler Satellite\nDatum, J. Geophysical Research, Vol. 79, No. 35, pp. 5319-5332, 1974.\nGaposchkin, E.M., Earth's Gravity Field to the Eighteenth Degree and Geocentric\nCoordinates for 104 Stations From Satellite and Terrestrial Data, J.\nGeophysical Research, Vol. 79, No. 35, pp. 5377-5411, 1974.\nHeiskanen, W., and H. Moritz, Physical Geodesy, W.H. Freeman and Co., San\nFrancisco, 1967.\nLachapelle, G., Research in Physical Geodesy at Geodetic Survey of Canada,\npaper presented at the 69th Annual Meeting of The Canadian Institute\nof Surveying, Winnipeg, 1976.\nLambert, W., and W.F. Darling, Tables for Determining the Form of the Geoid\nand Its Indirect Effect on Gravity, U.S. Coast and Geodetic Survey,\nSpec. Publ. No. 199, U.S. Superintendent of Documents, Washington,\nD.C., 1936.\nMoritz, H., Precise Gravimetric Geodesy, Department of Geodetic Science,\nReport No. 219, 75 P., The Ohio State University, Columbus, Ohio, 1974.","397\nMoritz, H., Report of Special Study Group No. 5.39 of IAG, Fundamental Geodetic\nConstants, Bulletin Geodesique, No. 118, p. 398-408, December, 1975.\nRapp, R.H., Current Estimates of Mean Earth Ellipsoid Parameters, Geophysical\nResearch Letters, Vol. 1, No. 1, pp. 35-38, 1974.\nRapp, R.H., and R. Rummel, Methods for the Computation of Detailed Geoids and\nTheir Accuracy, Department of Geodetic Science, Report No. 233, 40 p.,\nThe Ohio State University, Columbus, 1975.\nRummel, R., and R.H. Rapp, The Influence of the Atmosphere on Geoid and\nPotential Coefficient Determinations from Gravity Data, J. Geophysical\nResearch (in press), 1976.\nSmith, D.E., , et al., Contributions to the National Geodetic Satellite Program\nby Goddard Space Flight Center, J. Geophysical Research, Vol. 81, No. 6,\npp. 1006-1026, 1976.\nStrange, W., L.D. Hothem, and M.B. White, The Satellite Doppler Station\nNetwork in the United States, (National Ocean Survey, Rockville, Md. 20771),\npaper presented to the IUGG, International Association of Geodesy, XVI\nGeneral Assembly, Grenoble, France, August, 1975.\nVincent, S., and J. Marsh, Goddard Space Flight Center Global Detailed Gravi-\nmetric Geoid 1975, (NASA/Goddard Space Flight Center, Greenbelt, Md. 20771),\npaper presented to the IUGG, International Association of Geodesy, XVI\nGeneral Assembly, Grenoble, France, August, 1975.\nWagner, C.A., F.J. Lerch, J.E. Brownd, and J.A. Richardson, Improvement in the\nGeopotential Derived from Satellite and Surface Data, NASA preprint\nX-921-76-20, 11 P., Goddard Space Flight Center, Greenbelt, Md., 1976.","398","399\nRESULTS FROM PORTABLE DOPPLER RECEIVERS\nUSING BROADCAST AND PRECISE EPHEMERIDES\nCaroline F. Leroy\nDefense Mapping Agency Topographic Center\n6500 Brookes Lane\nWashington, D. C. 20315\nDepartment of Geodesy and Surveys\nAbstract\nDoppler data from an ITT 5500, JMR, MX GEO II, and Geoceiver were observed\nat stations in Herndon, Virginia. All data were reduced to point positions\nusing first, the precise ephemeris and second, the satellite broadcast ephem-\neris. Comparisons of results to the known receiver position showed that data\nfrom the ITT 5500, JMR, and MX GEO II receivers produced a position of\naccuracy comparable to a Geoceiver derived position when using the precise\nephemeris for reduction of all data.\nThe positions of the four receivers, determined using the satellite\nbroadcast ephemeris on the APL 4.5 system, are in error by as much as 12\nmeters. A 136 pass solution with MX GEO II data from April 1975 is in error\nby over 7 meters. Point positions computed using an increasingly larger\nnumber of passes of MX GEO II data from April 1975 stabilized in all three\ncomponents at 75 passes.\nMX GEO II data from July 1976 was reduced using the broadcast ephemeris\non the WGS 72 system. A total of 98 passes were used. The point position\nis in error by over 16 meters, indicating that the change of Datum of the\nbroadcast ephemeris system did not improve the point position determination.\nAlthough the paper was originally intended to analyze the accuracy of a\npoint position using the broadcast ephemeris, the reduction of data from\ndifferent types of receivers did emphasize the variation in recording mediums,\ncode, format, and content of the various receivers leading to a recommendation\nthat manufacturers consider the data user when designing equipment and take\nsteps leading to standardization. It is also highly recommended that a\nstandard format be adopted by agencies exchanging data to avoid unnecessary\ndelays in reducing data caused by problems that can be easily avoided.\nIntroduction\nThe Defense Mapping Agency Topographic Center (DMATC) currently computes\nprecise positions for Doppler receivers using the point positioning concept\nrequiring a precise satellite ephemeris. To insure the maximum accuracy of\na point position, a minimum of 35 good passes are required which, in turn,\nrequires a station occupation of from 3 to 12 days. The length of the occu-\npation period depends on the latitude of the station and the number of\nsatellites, normally one or two, for which the precise ephemeris is available.\nThis long occupation period is costly in both time and money. It is also\ncostly to operate the DMATC permanent worldwide tracking network, the TRANET,\nwhose tracking data is used to compute the precise ephemeris at DMATC. The","400\noccupation time and tracking costs could be considerably reduced if the\nbroadcast ephemeris, computed by the Navy Astronautics Group for six U.S.\nNavy navigation satellites, could be used to obtain point positions of geodetic\naccuracy. This analysis was initiated to determine whether point positions\ncomputed using the satellite broadcast ephemeris would be accurate enough for\ngeodetic purposes.\nPoint positions were computed for Herndon, Virginia, with both the sate-\nllite broadcast and precise ephemerides using data from the Geoceiver, ITT 5500,\nJMR, and MX GEO II receivers. Results from the various receivers, using\nvarious amounts of data and ephemerides, are compared to the previously\nestablished Geoceiver potition at Herndon, Virginia.\nThe various procedures required to reduce data from four types of\nreceivers leads naturally to a discussion of the need for standardization of\nrecording media and format. Although the Herndon data included data from only\nthe Geoceiver, ITT 5500, JMR, and MX GEO II receivers, a description of the\nMarconi and MX 702A receivers is included to emphasize the need for standard-\nization.\nBackground\nThe satellites used for Doppler geodetic point positioning are the U.S.\nNavy Navigation Satellites (NNS). The Navy Navigation Satellite System employs\nsix satellites in circular polar orbits at an altitude of approximately 600\nnautical miles. Each broadcasts two ultrastable frequencies, one at slightly\nless than 400 MHz and one at 150 MHz. The dual frequencies allow the computa-\ntion of the first order ionospheric refraction correction. A data stream is\nphase modulated on the 400 MHz carrier to provide both time and satellite\nephemeris information. The six satellites are spaced so that one satellite\nis visible to any point of the Earth at least once every 2 hours. The six\nsatellites and their associated parameters are listed in Table 1.\nThe six NNS's are tracked by four stations in Maine, Minnesota, Hawaii,\nand California. The tracking data are used to determine an orbit for the\npast 36 hours and to predict the orbit for approximately the next 12 hours.\nEach satellite has a memory which can hold 16 hours of orbit prediction data.\nThis predicted ephemeris is injected into the satellite for transmission on\nthe phase modulated 400 MHz frequency. In a single pass navigation solution,\nthe position of a receiver can be determined to within 30 meters in latitude\nand longitude using this predicted or broadcast ephemeris. It is the broad-\ncast ephemeris which is used by ships for navigation purposes. For\ngeodetic\npurposes, it is desirable to determine latitude, longitude, and height of a\nreceiver to within 1 or 2 meters.\nPoint positioning, illustrated in Fig. 1, is the method used to solve\nfor the unknown receiver position by assuming the satellite's orbit is known.\nIf a Doppler receiver, such as the Geoceiver, observes 35 or more well balanced\npasses, a position accurate to + 1.5 meters in latitude, longitude, and height\ncan be determined at the 90% confidence level if the ephemeris is accurate\nto 2 or 3 meters. This accurate satellite orbit, or precise ephemeris is\ncomputed for one or more navigation satellites from worldwide Doppler tracking\nnetwork called the TRANET. The permanent TRANET stations are shown in Fig. 2.","401\nNORAD\na\nCATALOG\nINTERNATIONAL\nAPL\nNSWC\n(km)\ni\n50*\ne\nLAUNCH DATE\n2754\n1967-34A\n30120\n58\n7442\n.002\n90.2\n18.1\n14 Apr 67\n2807\n1967-48A\n30130\n59\n7465\n.002\n90.6\n322.3\n18 May 67\n2965\n1967-92A\n30140\n60\n7455\n.005\n89.3\n342.5\n25 Sep 67\n3133\n1968-12A\n30180\n64\n7463\n.008\n91.0\n276.5\n1 Mar 68\n4507\n1970-67A\n30190\n68\n7465\n.018\n90.1\n249.2\n27 Aug 70\n6909\n1973-81A\n30200\n77\n7400\n.017\n90.2\n118.1\n29 Oct 73\n*Epoch: Day 131, 1975\nTable 1. Navy Navigation Satellite numbers and defining parameters.\nDOPPLR Computer Program Used For Point Positioning\nThe Doppler program, DOPPLR, written at DMATC is a FORTRAN program\ndeveloped for use on the UNIVAC 1108 electronic computer to derive the position\nof a receiver observing integrated Doppler shifts in transmission of an\nelectronic signal from an artificial Earth satellite. The solution is made\nin a multi-pass mode involving the simultaneous adjustment of data from many\npasses of one or more satellites over a single receiver.\nThe point positioning method uses the Doppler shift of stable signals\nbroadcast from satellites to determine the precise geodetic coordinates of\nthe receiving antenna. The coordinates are the principle unknowns and all\nknown error sources are included in the mathematical model in order to obtain\nthe greatest accuracy possible. The satellite ephemeris computed from the\nTRANET data is assumed to be known in the solution and the resulting coor-\ndinates are in the reference system of the ephemeris.\nThe program operates on integrated range rate data such as produced by\nGeoceiver, ITT 5500, MX GEO II, and JMR observing equipment. Each data point\nconsists of observed Doppler counts of 400 MHz and 150 MHz channels, the epoch\nat the beginning of the count, and the time interval over which the count was\naccumulated.\nAfter the data have been edited for blunders, corrections are applied to\nthe Doppler count for the effects of ionospheric and tropospheric refraction.\nThe ionospheric refraction, which is inversely proportional to the frequency,\nis computed from a comparison of the 150 MHz and 400 MHz data. The tropospheric\ncorrection is computed using the Hopfield model for refractivity. A third\ncorrection, called the partial cycle correction, is also applied if the\nreceiver has an internal clock to record time at the beginning and the end of\nthe Doppler count. The partial clock correction to the Doppler count compen-\nsates for the difference in the equipment delay between the beginning and end\nof a measured count. It is the use of this internal clock data which results\nin the + 1.5 meter accuracy of the Geoceiver in comparison to the + 3.0 meter\naccuracy for the ITT 5500 which does not use an internal clock.","402\nGEOCEIVER\nDOPPLER SINGLE POINT POSITIONING\nOBSERVED\nDATA\nPOSITION\nDMATC\nPOINT\nORBIT 1\nFIG. 1\nORBIT 2\nEPHEMERIS\nPRECISE\nDMATC\nUSERS\nORBIT N\nOBSERVED\nDATA\nSTATION\nTRANET","60'\n20\n20\n40\nSeychelles\nCONTRIBUTING STA.\nso\n1\nFOREIGN TRANET\nA S\nDMATC TRANET\n60\nS. Africa\nPSL TRANET\nARL TRANET\n40\nOPNET\nItaly\nBelgium\nC A\n10\nEngland\nR\nTRANET and OPNET Tracking Network. October 1976\n20\n20\nS. Jone\nVirginia (DMATC)\nis\n40\n2\nVis\n40\nThule\nMAMERICA\nMaine\nOttnwa\n60\n00\n5\nTexas (ARL)\nH\nC\n80\n00\nGOOD\nMexico\nT\nMinn\nv;\n100\n100\nNew\nAnchorage\n120\n120°\nCalif\nHawaii\n140\n110\nSemoa\n160\n160\nMcMurdo\nFIG. 2\n100\n100°\nAustralia\n160°4\n160\nJapan\nGuain\nSan Miguel\n2\n140\nNo\nC\n120\n120\nA\nI\n100\n100\n$\nA\n40\n20.\n40°\n80\n60\n20\n60\n0","404\nIn addition to solving for the coordinates of the receiver, the DOPPLR\nprogram computes a clock epoch error per pass and solves for frequency offset\nper pass. As a diagnostic tool, there is also an optional single pass navi-\ngation solution. A single pass navigation is one in which data from only\none pass are fit to the known orbit and the station is allowed to adjust in\ntwo dimensions. The single pass navigation results are frequently used to\ndetermine passes of poor quality data.\nThe mathematical formulation for DOPPLR is well documented in DMATC\nTechnical Report No. DMATC 76-1, dated April 1976.\nEquipment Description*\nUntil recently, only the Geoceiver recorded accurate time with each\nDoppler count and could, therefore, produce results accurate enough for\ngeodetic purposes. In 1974, the JMR Company introduced the JMR receiver\nwhich also has accurate timing data. Recently, Magnavox added a clock to\nits land surveyor MX 702A to produce the MX GEO II.\nAlthough the International Telephone and Telegraph ITT 5500 does not\nrecord time for each data point, it does record the broadcast ephemeris and\nwas included in DMATC tests for that reason. All four receivers are\nminaturized, portable receivers which are weather independent. The receivers\ndiffer in data rate, type of data, and medium on which data is recorded. The\ncharacteristics of two other receivers, the Marconi and MX 702A, as well as\nthe characteristics of each of the above receivers, are listed in Table 2\nin preparation for a later discussion on standardization of data format.\nSince Table 2 summarizes the equipment description, only a few differences\nin equipment, particularly those causing problems, will be mentioned here.\nThe method of recording clock time varies from receiver to receiver. The\nGeoceiver, ITT 5500, and JMR receivers record day, hour, and minute. The\nMX 702A, MX GEO II, and Marconi receivers record only 2-minute time marks\nwhether or not the receiver is locked on a satellite signal. To have the\ncorrect time associated with a Doppler count for the MX 702A, MX GEO II,\nand Marconi receivers, it is necessary to manually log the time the equipment\nis turned on and count all 2-minute time marks on the punched paper tape,\ndisregarding mispunches which resemble 2-minute time marks. The association\nof the correct time with the observations did cause problems for data from\nthose receivers recording only 2-minute time marks.\nThe MX GEO II also differs from the other three receivers in three\naspects. First, the 400 MHz and 150 MHz counts are recorded at slightly\ndifferent times. Thus, the 150 MHz Doppler count must be corrected to\ncorrespond to the time of the 400 MHz count. Secondly, the Doppler counters\nare never set to zero and only record six octal digits. Computations must,\ntherefore, be made to add the proper number of overflows to adjust the Doppler\ncount to compensate for the \"zero\" reading. Third, the clock records only\n*Any mention, herein of a commercial product, does not constitute endorsement\nby the United Stated Government.","Paper Tape\nMARCONI\n(ASC II)\n8 Level\nN/A\n4.6\nYes\nNo\nNo\nNo\nNo\nNo\n8 Level Paper\nMX 702A\nTape (Non-\nstandard)\nTable 2. A summary of portable Doppler receiver characteristics\n4.6\nYes\nN/A\nYes\nNo\nNo\nNo\nNo\n8 Level Paper\nMX GEO II\nTape (Non-\nstandard)\n23, 27\nYes\nYes\nYes\nYes\nNo\nNo\nNo\nDigi-Printer Tape Cassette\nPaper Tape\n8 Level\nEach Pass\n(ASC II)\nJMR\nOR\n4.6\nYes\nYes\nYes\nYes\nYes\nNo\n(Teletype C)\nPaper Tape\nITT 5500\nFirst Pass\n5 Level\nOR\n4.6\nYes\nYes\nYes\nYes\nNo\nNo\nTape (Teletype\n5 Level Paper\nGEOCEIVER\nFirst Pass\n27, 32\nYes\nYes\nYes\nYes\nNo\nNo\nC)\nTime Interval\nSignal Status\nWeather Data\nEQUIPMENT\nLocal Clock\nClock Reset\n(Seconds)\nRecording\nBroadcast\nEphemeris\nTiming\n(Format)\nTrailer\nMedium\nHeader","406\nfour octal digits for time in microseconds. The overflows must, therefore,\nbe determined and applied to the clock reading. No problems were encountered\nin any of the three computations.\nThe recording medium for the six receivers varies between 5-level and\n8-level punched paper tape and magnetic tape cassette. The various media\npresented a problem compounded by the nonstandard format used by the MX GEO II\nand MX 702A. These problems will be addressed in the section on format\nstandardization.\nReceiver Accuracies\nThe purpose of determining a position for each receiver, using the precise\nephemeris, was to establish that the data from each receiver could produce a\nposition of sufficient accuracy for use in tests with the broadcast ephemeris.\nThe accuracy of the Geoceiver at the 90% confidence level is + 1.5 meters in\neach axis for 35 or more passes, + 2.0 meters for 20 to 34 passes, and + 2.5\nmeters for 12 to 19 passes. The data from another receiver will be acceptable\nfor further testing if the position determined with another receiver agrees\nwithin 1.5, 2.0, or 2.5 meters in each coordinate of the Geoceiver position\nfor 35 or more, 20 to 34, or 12 to 19 passes respectively. The JMR, ITT 5500,\nGeoceiver, and MX GEO II test data were all observed at Herndon, Virginia,\nsince August 1974. The position for station 30039, which will be used for\ncomparisons for ITT 5500 and MX GEO II results, is a mean of five positions\ndetermined by Geoceiver with the precise ephemeris after 1 January 1973. The\nposition for Herndon station 30071, used for comparison of JMR results, is\nthe position determined by Geoceiver with the precise ephemeris as part of\nDMATC tests in April 1975. The positions used to compute the mean position\nof 30039 as well as the position for 30071 are all referenced to the NWL 9D\nsystem of the precise ephemeris.\nGeoceiver\nDoppler data were observed with a Geoceiver from 10-21 April 1975 to\ndetermine a point position for Herndon, Virginia, station 30071. Fifty-nine\npasses were used with the precise ephemeris for satellites 30190 and 30200\nto determine the position. A minimum elevation angle of 10 degrees was used\nfor editing. The accuracy of this position, which is used for comparison of\nJMR results, is + 1.5 meters in each coordinate as defined in the DoD Geo-\nceiver tests.\nJMR\nDuring the period 6-10 September 1974, observations were taken with a\nJMR receiver at Herndon. The 4.6 second Doppler counts were accumulated into\n27 and 32 seconds intervals to resemble Geoceiver data. Editing was done on\na minimum elevation angle of 10 degrees and a minimum signal strength of 3\n(above 140 dbm). Fourteen passes were included in the solution using the\nprecise ephemeris for satellites 30190 and 30200. The results listed in\nTable 3 indicate that the JMR position is within the 2.5 meters of the\nGeoceiver position.","407\nITT 5500\nThe ITT 5500 observed data from 20-28 March 1975 on station 30039 at\nHerndon, Virginia. Data with an elevation angle less than 5 degrees were\ndeleted from the solution leaving 40 passes in the solution. The 4.6 second\nDoppler counts were accumulated into 2-minute intervals and the precise\nephemerides for satellites 30190 and 30200 were used. The solution results\nare listed in Table 3. The position using the precise ephemeris is within\n1.5 meters in each coordinate of the Geoceiver position.\nMX GEO II\nData were observed with the MX GEO II receiver on station 30039 in\nHerndon during the period 20-31 July 1976. Forty-two passes with a minimum\nelevation angle of 10 degrees were used in the position determination with\nthe precise ephemeris for satellites 30120 and 30190 assumed known. The\ndifferences from the comparison Geoceiver position, listed in Table 3, are\nwithin 1.5 meters in each coordinate of the known position.\nComparison of Broadcast Ephemeris Results\nThe Doppler data used from the four receivers for the determination of a\npoint position with the precise ephemeris were next reduced using the satellite\nbroadcast ephemeris. An additional data set of MX GEO II data observed\n10-21 April 1975 were included in the broadcast ephemeris tests because the\nGeoceiver was observing simultaneously and the 136 passes available with the\nbroadcast ephemeris allowed more extensive testing. The JMR, ITT 5500, and\nMX GEO II receivers all record the satellite broadcast ephemeris and thus\nthe broadcast ephemeris was directly available. The Geoceiver, which does\nnot record the broadcast ephemeris, was observing data on station 30071 in\nHerndon at the same time in April 1975 that the MX GEO II was observing data\non station 30039, approximately 15 meters away. The broadcast ephemeris\nrecorded by the MX GEO II was consequently used to reduce the Geoceiver data.\nResults from the four receivers using the satellite broadcast ephemeris\nin the APL 4.5 system are compared in Table 4 to the Geoceiver position,\ndetermined using the precise ephemeris which is in the NWL 9D system. The\nMX GEO II data from July 1976 is not included in Table 4 since the satellite\nbroadcast system was changed from the APL 4.5 system to WGS 72 in December 1975.\nTwo satellites were used in the determination of the JMR, ITT 5500, and\nGeoceiver broadcast positions, whereas six satellites were used for the MX\nGEO II broadcast positions.\nThe large differences in positions of 12 meters or more certainly do not\ncorrespond to the geodetic accuracies that are required. However, the relation-\nship between the APL 4.5 system and NWL 9D system was never well established,\nand differences in positions in the tables reflect both the effect of using\na less accurate ephemeris (the broadcast ephemeris) and the effect of a\ndifference in datums. In addition, the wide spread of the results certainly\ndoes not conform to the 1 meter repeatability available through use of the\nGeoceiver with the precise ephemeris.","408\nGEOCEIVER-OTHER RECEIVER\nRMS\nDO\n41\nAh\nRECEIVER\nPASSES\n(m)\n(m)\n(m)\n(m)\nJMR\n14\n.21\n-2.00\n.60\n.07\nITT 5500\n40\n1.10\n1.39\n.43\n-0.63\nMX GEO II\n(July 1976)\n42\n.18\n.18\n.87\n-1.18\nTable 3. Comparison of JMR, ITT 5500, and MX GEO II results with the Geoceiver\nposition at Herndon, Virginia. Precise ephemerides for two NNS satellites were\nused.\nBROADCAST-PRECISE\nRMS\nso\nAl\nAh\nRECEIVER\nPASSES\n(m)\n(m)\n(m)\n(m)\nITT 5500\n35\n4.01\n-7.31\n5.56\n4.48\nJMR\n38\n.86\n-0.10\n12.06\n-3.12\nGEOCEIVER\n35\n1.30\n+2.15\n8.59\n1.77\nMX GEO II\n(April 1975)\n136\n1.25\n-1.79\n6.64\n- .94\nTable 4. Differences of point positions at Herndon, Virginia determined by\nvarious receivers using the satellite broadcast ephemeris (maximum six sate-\nllites) versus the precise ephemeris (two satellites). The broadcast ephemeris\nis on the APL 4.5 system and the precise ephemeris is on the NWL 9D system.\nThe datum of the broadcast ephemeris was changed from the APL 4.5 system\nto the WGS 72 system in December 1975. A point position for the MX GEO II was\ndetermined in July 1976 to evaluate the new broadcast data. A total of 98\npasses of six satellites were used with the broadcast ephemeris, and the result\nwas compared with an NWL 9D position determined with the precise ephemeris\nusing 42 passes of the July 1976 data. The NWL 9D position was converted to\na WGS 72 position based on the transformation in the DoD WGS 72 publication.\nThe differences in position in meters are:\nWGS 72 Transformed- WGS 72 Broadcast\nAO = -12.21\nAl =\n8.64\nAh\n6.52\nThese differences are not within geodetic accuracies and are larger than\nexpected since the conversion of the broadcast ephemeris to the WGS 72 system\nalso incorporated changes to increase the accuracy of the broadcast ephemeris.","409\nSince a total of 136 passes of MX GEO II, April 1975 data, were available\nwith satellite broadcast ephemeris data in the APL 4.5 system, further tests\nwere run. First, to determine the point at which the addition of a pass is\ninsignificant, solutions were run with the broadcast ephemeris beginning with\n2 passes, increasing up to 25 passes. This was done with four sets of data\nusing all six satellites. Figures 3 and 4 show the plots of the solutions by\nnumber of passes for latitude, longitude, and height. Since the large varia-\ntions had disappeared at approximately the 15 pass solution, a 5-pass increment\nwas used from 25 passes to 135 passes. To show the convergence to the 135-pass\nsolution, the 5-pass increment solutions are plotted in Fig. 5 for latitude,\nlongitude, and height. Analysis of the plots indicates that the latitude is\nthe least stable of the three. With 15 passes, the longitude is within a\nrange of 4 meters, and the height is with a range of 5 meters. It is not\nuntil the 75-pass solution that the latitude is within a range of 3 meters of\nthe final position. The mean and standard deviation of the differences for\nfour sets of 15-pass and 24-pass solutions are listed in Table 5. Since there\nwas only one solution for 75 passes, it is not included in Table 5.\nPASSES\nso(m)\nAl (m)\nAh (m)\n15\nMean\n-4.34\n- .05\n-1.58\n15\nSt. Dev.\n+8.56\n+1.34\n+3.35\n24\nMean\n-1.58\n- .31\n0.93\n24\nSt. Dev.\n+4.79\n+1.68\n+3.13\nTable 5. Mean and standard deviation of differences in MX GEO II point position\nresults determined using four sets of 15 passes and four sets of 24 passes.\nThe satellite broadcast ephemerides on the APL 4.5 System were used for six\nsatellites.\nBROADCAST\n6 SAT SOL'N-1 SAT SOL' N\nAO (m)\nSATELLITE\nPASSES\nRMS\nAl (m)\nAh (m)\n30120\n27\n1.24\n+2.93\n+ 4.00\n-7.88\n30130\n17\n0.99\n-2.44\n+ 2.84\n+3.58\n30140\n22\n1.22\n-6.04\n- 2.91\n+6.36\n30180\n13\n1.27\n+3.51\n+11.75\n+7.22\n30190\n34\n1.33\n-4.84\n- 3.73\n-2.02\n30200\n23\n1.06\n+9.53\n+ 3.35\n+0.81\nTable 6. Comparison of MX GEO II point positions determined using one satellite\nbroadcast ephemeris versus six. The broadcast ephemerides are on the APL 4.5\ndatum.","410\n62.0\nDATA SUBSET 1\n49.6\nDATA SUBSET 2\nDATA SUBSET 3\nDATA SUBSET 4\n37.2\n24.8\n12.4\nITERIES\nFINAL\nPRECISE\n0\nBROADCAST\nof\n-12.4\n-24.8\n-37.2\n-49.6\n-62.0\n0\n4\n8\n12\n16\n20\n24\n28\nPASSES\nFigure 3. Comparison of point positions determined from the broadcast ephemeris on the APL 4.5\nSystem. The difference in latitude between the positions and the precise NWL 9D position. obtained\nfrom a 64-pass solution, is shown as a function of the number of passes for 4 different data subsets of MX\nGEO II data. Also shown is the final broadcast position obtained from a solution of 136 passes.","411\nDATA SUBSET 1\n12.0\nA\nDATA SUBSET 2\nDATA SUBSET 3\n9.6\nDATA SUBSET 4\n7.2\nFINAL\nBROADCAST\n4.8\nFINAL\n0\nPRECISE\n-2.4\n8\n4\nFINAL\nPRECISE\n0\nBROADCAST\n-8\n16\n20\n24\n0\n4\n8\n12\nPASSES\nFigure 4. Comparison of point positions determined from the broadcast ephemeris on the APL 4.5\nSystem. The differences in longitude and height between the positions and the precise NWL 9D position.\nobtained from a 64-pass solution. are shown as a function of the number of passes for 4 different data\nsubsets of MX GEO II data. Also shown is the final broadcast position obtained from a solution of 136\npasses.","412\n12.4\nFINAL\nPRECISE\n0\nBROADCAST\n-12.4\n19.2\n14.4\n9.6\nFINAL\nBROADCAST\n4.8\nFINAL\n0\nPRECIS\n4.0\nFINAL\nPRECISE\n0\nBROADCAS\n80\n100\n120\n140\n0\n20\n40\n60\nPASSES\nFigure 5. Comparison of point positions determined from MX GEO II data using the broadcast ephemeris\non the APL 4.5 System. The differences in latitude. longitude. and height between the positions and the\nNWL 9D precise position. obtained from a 64-pass solution. are shown as a function of the number of\npasses.","413\nPlots similar to Figs. 3 and 4 were completed for the precise ephemeris.\nSolutions using 2 through 16 passes with the precise ephemeris for two sate-\nllites are plotted in latitude, longitude, and height in Fig. 6. Using 9\npasses, the latitude, longitude, and height are all within 3 meters of the\nfinal precise position. Results using 20, 25, 30, 35, and 40 passes are also\nindicated to show the stability of the position using the precise ephemeris.\nThe results using the precise ephemeris are in agreement with the DoD Geo-\nceiver Test results of 1971.\nThe next test was to reduce the data for each of the six satellites sep-\narately to determine the effect of using only selected satellites for\nposition determination when using the broadcast ephemeris as was done with\nthe ITT 5500, JMR, and Geoceiver data. Table 6 includes the differences in\nposition using one satellite broadcast ephemeris versus using six. The wide\nspread of the solutions using individual satellites indicates that caution\nmust be exercised when using only one satellite broadcast ephemeris, particu-\nlarly if less than 75 passes are used since the position is well determined\nusing less than 75 passes even with six satellites.\nStandardization of Data Format\nThe capability to compute a point position using data recorded by all six\ntypes of Doppler receivers described in Table 2 requires a tremendous amount\nof hardware and software. At DMATC, the capability exists to take data from\nany one of the receivers, on punched paper tape, and convert it to a medium\nand format acceptable to the point positioning program. The UNIVAC 1108\ncomputer with the peripheral paper tape reader, the UNIVAC 9300, plus four\npre-preprocessors and six preprocessors are necessary to reformat the punched\npaper tape data to determine a point position. If JMR data is received on\nmagnetic tape cassette as the receiver records it, a JMR cassette reader plus\na teletype or minicomputer is necessary to convert the observation data to a\nusable medium, such as punched paper tape or magnetic tape.\nThe four pre-preprocessors are necessary because not only do the receivers\nrecord data on different level punch paper tape, but they use different codes.\nThe Geoceiver and ITT 5500 record data in Teletype C code on 5-level punch\npaper tape. The JMR and Marconi receivers record data in ASC II code on\n8-level punch paper tape. The MX 702A and MX GEO II each record data on 8-\nlevel punch paper tape in different non-standard formats.\nThe six preprocessors are necessary because the contents and format of\nthe recorded data differ. The Geoceiver, ITT 5500, and JMR receivers record\nlocal time including day, hour and minute. The MX 702A, MX GEO II, and\nMarconi receivers record only 2-minute time marks which must be counted to\nestablish local clock time. The JMR records only one Doppler count whereas\nthe other five receivers record two. The JMR, MX 702A, and MX GEO II record\na signal status word, and the other three receivers do not. All receivers\nexcept the Geoceiver, record the satellite broadcast ephemeris. Doppler\ncounts are recorded in intervals from 4.6 seconds to 32 seconds.\nFinally, in the point positioning program, a modification is required for\neach data type for input format and the ionospheric refraction computation.\nThese are minor but essential modifications.","414\nDATA SUBSET 1\nDATA SUBSET 2\n6.2\nDATA SUBSET 3\nDATA SUBSET 4\n0\nFINAL PRECISE\n-6.2\n9.6\n4.8\nFINAL PRECISE\n0\n4.0\n0\nFINAL PRECISE\n-4.0\n16 20\n30\n40\n0\n4\n8\n12\nPASSES\nFigure 6. Comparison of point positions determined from MX GEO II data using the precise ephemeris on\nthe NWL 9D System. The differences in latitude. longitude. and height between the positions and the\nprecise position. obtained from a 64-pass solution. are shown as a function of the number of passes.","415\nThe software and hardware mentioned above does not even consider data sent\nin from other agencies in packed, blocked, ASC II, EBCDIC, or other format\nwhere Doppler data may be in octal or decimal and the broadcast message may\nbe in decimal or BCDXS3. A simple but troublesome problem arises when paper\ntapes are sent in on reels greater in diameter than 5 inches; the UNIVAC 9300\ncannot handle paper tape reels of that size. As a result, paper tapes are cut\nand in the case of MX 702A, MX GEO II, and Marconi data, the 2-minute time\nmark system of computing time falls apart.\nIt is not likely that the manufacturers will modify existing equipment to\nstandardize formats. Before any new equipment is designed, it is hoped that\nthe manufacturers will consider the data user and establish a means of standard-\nizing beginning at the point of, for example, recording data in ASC II on\n8-level punch paper tape.\nThe second area where standardization could more easily occur is in the\nexchange of data between agencies. A simple means of standardization would\nbe to record data on magnetic tape consisting of a header record, a broadcast\nmessage record, and data records for each pass. The header record would\ncontain the station number, approximate coordinates, the satellite number,\nyear, day, hour, and minute of the first point of the pass and any weather\ndata. The broadcast message record would contain all the fixed and variable\nmessage words applicable to the pass. For each data point, a record would\ncontain start time and duration of the Doppler count, the Doppler count or\ncounts, and a status code if applicable. This information is required for all\npoint positioning computer programs and a standardized format such as this\nwould save the approximately 40 hours of computer programming time spend at\nDMATC to read data from another agency. It is highly recommended that\nconsideration be given by manufacturers and data users alike to standardize\nas much as possible.\nConclusion\nResults of point positioning computations using the precise ephemeris\nindicate the JMR, ITT 5500, and MX GEO II receivers determined the position\nof Herndon with the 1.5 meters of the Geoceiver position for a 35-pass solution\nand 2.5 meters for the 14-pass solution. The results of determining the\npoint position using the broadcast ephemeris on the APL 4.5 System indicates\nthat 75 passes are necessary to determine a position which will not vary more\nthan a meter or two with additional data. The use of the broadcast ephemeris\non the APL 4.5 System for one or six satellites with any of the observation\ndata did not produce a position for Herndon which could be used for geodetic\npurposes. The MX GEO II data using the updated satellite broadcast ephemeris\non WGS 72 differed from the NWL 9D position transformed to WGS 72 by -12.21,\n8.64, and -6.52 meters in latitude, longitude, and height respectively and\nis thus not of geodetic accuracy.\nThe reduction of data from different types of receivers did emphasize\nthe variation in recording mediums, code, format, and content of the various\nreceivers leading to a recommendation that manufacturers consider the data\nuser when designing equipment and take steps leading to standardization. It\nis also highly recommended that a standard format be adopted by agencies","416\nexchanging data to avoid unnecessary delays in reducing data caused by\nproblems that can be easily avoided.\nAcknowledgements\nThe author wishes to thank Mr. Jesse K. Murphy and Mr. Charles P. Slavin\nfor their assistance in data reduction and Mr. Bruce R. Bowman for his\ntechnical contributions.\nReferences\n1. Smith, R. W. , C. R. Schwarz, and W. D. Googe; \"DOPPLR-A Point Positioning\nProgram Using Integrated Doppler Satellite Observations\"; Technical Report\nNo. DMATC 76-1; April 1976.\n2. \"The Department of Defense World Geodetic System 1972\"; Defense Mapping\nAgency, Washington, D.C. ; May 1974. (Prepared by the World Geodetic System\nCommittee and presented by Thomas 0. Seppelin.)\n3. \"Results of the ITT 5001 Doppler Receiver Tests\"; Geodetic Memorandum\nNo. 1651 U.S. Army Topographic Command Washington, D. C.; September 1970.\n4. \"Report of the DoD Geoceiver Test Program\"; DMA Report 0001; July 1972.\n(Prepared by Applied Physics Laboratory, The Johns Hopkins University,\nSilver Spring, Maryland.)","417\nMETHODOLOGY AND FIELD TESTS OF GDOP, A\nGEODETIC COMPUTATION PACKAGE FOR THE\nSHORT ARC ADJUSTMENT OF SATELLITE\nDOPPLER OBSERVATIONS\nC. Boucher\nInstitut Géographique National\nFrance\nAbstract\nThe French Insitut Géographique National (I.G.N.) has set up a computation\nchain for processing Doppler data obtained with JMR-1 geodetic receivers using\nthe NNS System. The basic use of the GDOP package is the short arc adjustment\nof simultaneous observations. Using a stepwise motion of several receivers,\nthis process enables one to position several tens of stations. Field tests\nusing the French terrestrial geodetic network showed an external consistency\nof about 1.0 meter in three-dimensional relative position.\nAmong the various factors which enable the considerable development of\nsatellite Doppler techniques, the apparition of portable geodetic receivers\nprovided an actual achievement. Accordingly, those high-quality instruments\npermitted to set up operational methods for the establishment of terrestrial\ngeodetic points in any area or in any weather condition. For those reasons,\nthe French Institut Géographique National (I.G.N.) has begun in the end of\n1974 an extensive research program on satellite Doppler methods, both in a\ntheoretical and practical scope. It must be noticed that this has been much\nhelped by preliminary works performed via the Groupe de Recherches de Géodésie\nSpatiale (G.R.G.S.) by A. FONTAINE (1973) and later by C. BOUCHER (1974-1975).\nIn fact, this paper is devoted to the description of an operational method of\nDoppler geodetic positioning using JMR-1 receivers and NNS System.\nModelling of Satellite Doppler Measurements\nA preliminary mathematical model has been developed [1]. We shall not\ndiscuss further this point, which is the object of various communications\nor discussions during this Symposium. Nevertheless, we shall give the basic\nobservation equation, mainly in order to point out the various unknowns or\nparameters which appear in the model.\nActually, this relation is:\n(1) = (f, - At R R + f S (P2-P1) + AN + AN r - N o\nC\nwhere:\nis the (fictious) mean value of the frequency of the receiver,\nfR\nduring the time of observation\nis the same item for the frequency of the satellite\nf\nS","418\nAt is the duration of counting, in some uniform time scale\nR\nis the velocity of light in vacuo\nC\nis the observed count\nN\nAN is a tropospheric propagation correction\nis a relativistic correction\nAN\n(i = 1 or 2) is the slant range between the station and the\nPi\nsatellite position at the epoch ti\nis the epoch of emission of the wave front corresponding to the\nti\nreceipt at Ti T epoch:\n(2)\nwhere:\nAt i is the propagation delay in the atmosphere\nT1 is the epoch of the beginning of count\n2 is the epoch of the end of count\nMoreover, if we consider a geocentric reference frame R corresponding\nT\nto some average terrestrial frame, and if XS,k (t) are ephemeral coordinates\nof the satellite at time t (k = 1, 2, 3) , and XR,K coordinates of the station--\nprecisely the center of phase of the antenna--, then:\n(3)\nPi =\nOne must notice that the JMR-1 receiver performs the first order ionospheric\npropagation correction by an analogic electronic circuit. For further investi-\ngations, we refer, in addition to [1], to the classical literature, particularly\nthe extensive study of D.E. WELLS [2].\nMethods of Adjustment\nSeveral methods are possible for the geodetic adjustment of Doppler data,\neither geometric or orbital. Among orbital methods, semi-dynamical ones (in\nthe sense of E.M. GAPOSCHKIN [3] cf. [4]) are now widely used because of their\ngood value and the current availability of two kinds of ephemeris:\n-- Broadcast Ephemeris, given in real time by each Transit satellite\nPrecise Ephemeris, computed by DMA-NSWC.\nConsequently, several semi-dynamical methods are possible, according to\nthe following options:\n-- choice of unknowns","419\nUnknowns are dispatched into 3 sets:\nA) station position unknowns\nB) orbital parameters\nC) other external parameters (e.g. , frequency parameters, clock para-\nmeters, tropospheric parameters).\n.\nAt the view of B, one can divide methods into two major types:\npoint positioning (B is empty)\n--\nshort arc method (B is not empty)\ntype of chosen ephemeris:\n-- broadcast ephemeris\n-- precise ephemeris\nchoice of simultaneous observations:\n-- no systematic choice\nsystematic choice between 2 stations (translocation)\n--\nother possibilities (e.g., multilocation). .\nIn addition to that, other problems must be solved:\n-- possible modelization of bias (collocation)\nchoice of criteria of rejection\n-- choice of a-priori weight matrix\n(in particular, question of correlations) .\nThus, a number of computation methods have yet carried out interesting\nresults (e.g., [4], [5], , [6] et [7]) .\nError Budget\nWe summarize here various error sources perturbing the Doppler measure:\n1. Errors due to satellite orbit, depending upon chosen ephemeris and\norbital model\n2. Propagation error\nA. Error of the tropospheric correction model\nB. Remaining error of the ionsopheric correction process (second\nand higher order)\n3. Reception error\nA. Instrumental errors\n1) Instrumental noise (clock)\n2) Various errors (frequency, oscillator, electronic delay, etc.)","420\nB. Local effects\n1) Motion of the center of phase\n2) Local radioelectric effects.\nMethod Developed by I.G.N.\nThe positioning method primary developed by I.G.N. is a short arc adjust-\nment of simultaneous observations from several portable receivers, using\nbroadcast ephemeris.\nField Works\nField operations are performed using several portable geodetic receivers\nof JMR-1 type. The current number of correct satellite passes necessary to\nobtain the satisfactory accuracy is about 25 per station.\nThis is obtained by an occupation of 1-3 days, depending upon the location,\nand particularly upon the latitude.\nThe strategy of stationing the network needs about 4 receivers which are\nmoved sequentially each 1 or 2 days, depending upon the travel delay between\ntwo successive stations of a receiver.\nBy this method, at least 3 receivers are permanently providing simultaneous\nobservations of satellite passes. When various field constraints (e.g.,\ndifficulty of travels or communication) perturb this strategy, 1 or 2 extra\nreceivers perform observations at fixed stations, providing links with each\nmobile receiver.\nAt each station, operations are very easy. Doppler observations are\nautomatically recorded on magnetic cassettes. The only works are the regis-\ntration of meteorological conditions and the linking of antenna with station\nmonument, and every ancient horizontal control or levelling point.\nThe determination of antenna's mean sea level height is very important\nwhen geoidal information is lacking.\nData Processing\nThe major steps of the processing of Doppler data are given in Fig. 2.\nPreliminary handling of data. Cassette data are literally transcribed\non a magnetic tape with a mini-computer. Other data are punched on cards\n(meteorological elements, approximate coordinates of stations, etc.).\nThe following phases are executed by a chain of programs running on an\nIBM 370-135 computer:\nIncorporation of data. A11 the Doppler data and NNSS message values\nare stored in a general disk file.","421\nPreliminary orbit computation. This phase performs the majority voting\nof message, its decoding and the computation of ephemeris in a cartesian\nterrestrial system for each UT integer minute.\nPreprocessing. This program determines the wrong data and the wrong\npasses, using an iterative adjustment of each couple of station and satellite\nshort arc, letting orbits fixed at their preliminary value. Thus, there are\n4 unknowns: , AY, AZ and Af (frequency offset). One obtains good approx-\nimate values of station coordinates (+ 10m).\nGlobal adjustment. Two successive versions of this phase have been\nestablished up to now. The first one (I) was written by A. FONTAINE, using\ncentral conditions (position and velocity) as orbital unknowns. The second\n(II) was established by G. DE MASSON D'AUTUME (ref. [8]).\nSome Results\nSeveral Doppler observation campaigns have yet been done in I.G.N.,\neither in France or in oversea countries.\nIn particular, a test has been carried out during August 1975 in France.\nSix stations were chosen in a region of 200 X 200 km around Paris (Fig. 1).\nTheir terrestrial positions were determined by first order standards.\nSimultaneous Doppler observations with 6 JMR receivers were performed during\n8 days. This provided 225 possible passes.\nSome preliminary results from this test can be summarized in the following\nway: (a) results with GDOP II seem to be significantly better than those with\nGDOP I; (b) internal consistency of GDOP II results are presented in Table 1\nand Table 2. Let D be the solution for a global adjustment of 100 passes,\nand D1, D2, D3 and D4 four solutions of 25 passes, obtained by a partition\nof the 100 passes set.\nWe have done a 3D comparison of Di solution with D solution (i=1, 2, 3,\n4). Table 1 shows this comparison for D1. We can see that the absolute\nresult is not very satisfactory (up to 4 meters), but the standard error of\nthe fluctuations around a mean translation is ox=0.27 m, oy=0.39 m and oz=0.14 m.\nThose RMS values are presented in Table 2. The upper bound is 0.46 m.\nExternal consistency of GDOP II. The D solution is compared with 3D\nterrestrial coordinates, respectively ED 50 (Table 3) and F3 (Table 4). One\nmust precise that ED 50 horizontal coordinates are the standard values fur-\nnished by I.G.N., and F3 coordinates are issued from a global readjustment\n(1974) of the first order French horizontal network, including angular\nobservations, bases and astronomical azimuths. The same geoidal map was used\n(I.G.N. astrogeodetic geoid 1970).\nAs previously, DX, DY and DZ are the translations at each station, TX\nthe mean translation, and DDX, DDY, DDZ the remaining fluctuations. We can\nsee that the comparison with F3 is a major improvement with regard to ED 50.\nRMS values are ox=0.49 m, oy=0.84 m, and oz=0.28 m.","422\nThe Y value which is significantly less good corresponds to longitude,\nstations being close to the Greenwich meridian.\nPossible Geodetic Applications\nWe mention here major uses of such a method, taking advantage of its\ngood accuracy (<1 meter) in relative positioning:\n-- establishment of a geodetic terrestrial network (GN),\n-- linking of two GN,\n-- link of an isolated point (island, drilling platform, etc.) to a GN,\nextension of a GN,\ncontrol and strengthening of a GN, and\ngeoidal determination.\n--\nConclusions and Further Developments\nThe previous results show the really interesting value of Doppler methods\nwhich can already be used for geodetic positioning and aerotriangulation\nIt is our opinion that further developments could lead to an accuracy of 0.1\nmeter level, and in this purpose, new improved softwares are now being\ndeveloped at I.G.N. Anyway, the possible uses of this method are widely\nincreasing, especially in the scope of combinations with other types of\nmeasurements such as terrestrial ones or inertial surveying.\nReferences\n[1] C. BOUCHER (1976) : Modélisation des mesures Doppler effectuées par le\nrécepteur JMR-1 sur le système Transit - I.G.N. 26.748 S.G.N.\n[2] D.E. WELLS (1974) Doppler satellite control (PhD thesis), University\nof New Brunswick, Surveying Engineering Department - TR 29.\n[3] E.M. GAPOSCHKIN (1973): 1973 Smithsonian Standard Earth III, S.A.0.\nSpec. Report 353.\n[4] J. KOUBA, D.E. WELLS (1976) : Semi-dynamical Doppler satellite positioning,\nBull. Géod. 50, (1976), 27-42.\n[5] D.C. BROWN (1976) Doppler surveying with the JMR-1 receiver, Bull. Géod.\n50, (1976), 9-25.\n[6] R.J. ANDERLE (1976) : Error model for geodetic positions derived from\nsatellite observations, Bull. Géod. 50, (1976), 43-77.\n[7] L.D. HOTHEM (1975) Evaluation of precision and error sources associated\nwith Doppler positioning, NOAA/NOS/NGS, Presented at the XVIth General\nAssembly of the I.A.G. (Grenoble, August 1975). .\n[8] G. DE MASSON D'AUTUME (1976) Efficient methods for Doppler multi-station\ndata reduction, I.G.N. Internal Report (September 1976).","423\nDX\nDY\nDZ\nDDX\nDDY\nDDZ\n1\n- 2.979\n0.918\n-0.703\n-0.237\n0.470\n0.050\n-0.070\n2\n- 2.966\n0.295\n-0.823\n-0.224\n--0.154\n3\n2.168\n0.455\n-0.766\n0.574\n0.007\n-0.013\n4\n-2.727\n0.979\n-0.746\n0.015\n-0.530\n0.007\n5\n-2.826\n-0.016\n-0.500\n-0.084\n-0.465\n0.253\n6\n-2.788\n0.060\n-0.980\n-0.046\n--0.389\n-0.227\nTX\n- -2.742\n0.448\n-0.753\n0.272\n0.386\n0.143\no\nTable 1\nComparison (D1 - D)\no x\no y\no Z\nD1\n0.272\n0.386\n0.143\nD2\n0.211\n0.338\n0.319\nD3\n0.445\n0.456\n0.387\nD4\n0.249\n0.391\n0.229\nTable 2\nO values resulting from the comparition with D of 4 samples of 25 arcs","424\nDX\nDY\nDZ\nDDX\nDDY\nDDZ\n1\n-82.247\n- 116.616\n-117.425\n0.231\n-0.366\n0.456\n2\n-82.601\n- -114.783\n-117.561\n-0.123\n1.467\n0.320\n3\n-83.430\n- -116.116\n-117.666\n-0.952\n0.134\n0.215\n4\n-82.076\n- 118.327\n-118.272\n0.402\n-2.077\n-0.391\n5\n-82.493\n- 115.905\n-118.061\n-0.015\n0.345\n0.180\n6\n-82.023\n- 115.752\n-118.299\n0.455\n0.498\n0.418\nTX\n-82.478\n- 116.250\n- -117.881\no\n0.473\n1.079\n0.346\nTable 3\nComparison (Doppler - ED50)\nDX\nDY\nDZ\nDDX\nDDY\nDDZ\n1\n-80.136\n-117.418\n-119.239\n0.350\n0.008\n0.352\n2\n-80.417\n- -116.388\n-119.378\n0.069\n1.038\n0.213\n3\n-81.449\n- -117.601\n-119.417\n-0.964\n-0.175\n0.174\n4\n-80.391\n- -118.896\n-119.815\n0.094\n-1.470\n-0.224\n5\n-80.617\n-116.502\n-119.623\n-0.132\n0.924\n-0.032\n6\n-79.903\n- 117.750\n- -120.073\n0.583\n-0.324\n-0.482\nTX\n-80.485\n- -117.426\n- 119.591\no\n0.487\n0.839\n0.284\nTable 4\nComparison (Doppler - F3)","425\n2800\n+ 9050\n2500\n+ 9020\n9010 Q4\n9060\n+ 9030\n+ 9040\n2200\nBORDEAUX\n1900\nGRASSE\nO TOULOUSE\n1600\n300\n600\n900\n1200\n+\nJMR.F Campaign\nFIG. 1 Doppler Stations\nB\nOther stations (EDOC I, ...)\nScheduled stations","426\nInput :\n1/\nData\nhandling\n2/\nPreliminary\norbit computation\nFile\n3/\nPreprocessing\n4/\nGlobal\nadjustment\nOutput\nFIG. 2 Schematic phases of the adjustment","427\nGEOMETRIC POSITIONING VIA SATELLITE OF A\nDRILLING PLATFORM IN THE NORTH SEA\nA. R. Dennis\nAnalytical Technology Laboratories, Inc.\n13120 Brandon Way Road\nGaithersburg, Maryland 20760\nAbstract\nA new satellite doppler positioning technique, called Geometric Positioning\n(GP), has been applied to the problem of precisely locating a drilling platform\nin the North Sea, approximately 160 km offshore Norway. GP is a variant of\nthe short-arc method wherein a new satellite reference orbit is determined for\neach pass, based on control from fixed, known tracking sites. Unlike the\nformal short-arc technique, however, GP can be implemented in a minicomputer\nfor operation in the field, with no compromise in accuracy. This paper\ndescribed GP and compares it with the short-arc and translocation methods of\npositioning. Some results based on the use of the North Sea data are also\npresented, showing that with real data GP very nearly attains the theoretical\n(ideal) accuracy predicted by simulation, and that fractional meter positioning\naccuracies can be routinely possible based on the processing of data from\nonly a few passes.\nIntroduction\nDuring September and October of 1975 seven commercial Navy Navigation\nSatellite System (NNSS) receivers were stationed in the area of the North Sea,\nand during an interval of about four weeks received and recorded data from\nover 6,000 satellite passes. The main objective of this project was the\nprecise determination of a geodetic marker on a production drilling platform\nlocated over the Frigg Gas Field (approx. 59 deg 50 min N, 2 deg 36 min E).\nAnalytical Technology Laboratories, Inc. (ATL) was chosen as the prime con-\ntractor to a group including French, Norwegian, and United Kingdom Participants.\nSix receivers were located onshore close to first-order geodetic markers:\nthree in Norway and three in the UK. The plan was to gather a substantial\nnumber of simultaneously-recorded passes so that a fixed-control method such\nas Translocation (TL) or Short-Arc (SA) could be employed to provide several\nindependent estimates of the position of the platform marker in the European\nDatum, 1950 Adjustment (ED50) . This position could then be compared with the\nposition derived from the NNSS broadcast ephemeris (at the time the APL Mk.\n4.5) to aid in the calibration of a seismic survey held over the field in 1973.\nATL's responsibility was to furnish \"quick look\" results having uncertainties\nin the order of 3 meters, and this was successfully achieved. Analysis of the\ndata by UK and Norwegian agencies is continuing, however, with an ultimate\ngoal being the re-validation of the ED50 tie between the UK and Norway. These\nresults will hopefully be published by the appropriate parties some time in\nthe future. A brief discussion of ATL's results is contained later in this\npaper.","428\nSummary and Objectives of this Paper\nFor its part of the project, ATL applied a new technique for controlled\nsatellite positioning, developed by the author, which is designated as \"Geo-\nmetric Positioning\", or GP. As described in more detail in the sequel, GP is\na version of the short-arc (SA) method wherein a new reference satellite orbit\nis determined against which the unknown sites are positioned. As other workers\nhave described, SA tends to substantially reduce errors due to reference\norbit errors, including both prediction and datum shift errors.\nThe main purpose of this paper is to introduce the GP method and to show\nsome results of its application using the North Sea data. As will be shown,\nthe principal advantages of GP are its high accuracy, high data utilization\nefficiency, and ease of implementation and operation.\nBackground\nThe Translocation (TL) and Short-Arc (SA) positioning methods are designed\nto reduce unknown site positioning errors resulting from unknown errors in the\nreference orbit positions and other highly correlated errors. The principal\ndifference between the two methods results from the fact that SA attempts to\nactually adjust the reference orbit while simultaneously conducting site\npositioning, while TL does not, depending instead on the assumption that orbit\nerrors affect point positioning of all local sites in the same way.\nThe major advantage to the use of TL is its simple concept and ease of\nimplementation (point position solutions determined from the same satellite\npasses are simply differenced), thus leading to fast results (via a small\ncomputer perhaps). This is an important consideration for field operations\nsince it allows \"on-site\" monitoring of the data gathering phase.\nHowever, TL suffers from the disadvantage that data preprocessing (i.e.,\nselection of which passes to include in the simultaneous solutions) is an\nad-hoc procedure which can lead to deletion of more than 50% of the passes\nrecorded. Furthermore, it is difficult to guarantee that in any given appli-\ncation the point position differences will be free of systematic error. Also,\nthe TL solution is still referenced to the satellite datum, which although\nperhaps representing a second-order error, is still not completely desirable\nfor precise positioning in the local datum.\nThe SA technique, on the other hand, is not only much more efficient in\nterms of data handling, but also is potentially much more accurate than TL\nsince it reduces the major systematic errors (due to orbit prediction and datum\nshift) to insignificance during the unknown site positioning adjustment, not\nafter. In SA, all available measurements are used to control the effects of\nsystematic errors, which is not possible with TL. Also, due to its efficient\nuse of data, SA can yield comparable or higher accuracies using a fraction of\nthe passes required by TL. Indeed, as we will demonstrate in this paper, the\nSA concept can potentially yield accuracies far higher than any other technique,\nincluding point positioning using a Precise Ephemeris.\nFull descriptions are contained in other papers of this Symposium.","429\nSA does suffer from a serious disadvantage as far as field operations is\nconcerned: in its usual formulation it requires substantially more computing\npower than TL, and more than can easily be implemented in the field. This is\ndue to the requirement for adjusting and integrating the orbital dynamics\n(equations of motion) while simultaneously performing the unknown site position\ndetermination. A related disadvantage for SA is its sophisticated nature,\nrequiring operation by persons skilled in orbital mechanics and orbit deter-\nmination philosophy. This also precludes its use in the field on a routine\nbasis throughout the world.\nGeometric Positioning\nGeometric Positioning (GP) is a technique developed at ATL which combines\nthe high accuracy and efficiency of SA with the operating simplicity of TL.\nLike SA, GP finds a new reference orbit against which unknown site positions\nare determined. However, through the use of advanced and unique nonlinear\nestimation theory concepts as well as by exploiting some given information,\nGP can retain the accuracy of SA with modest computing requirements.\nThe \"given information\" mentioned above is the broadcast ephemeris, which\ncan be constructed from information received from each data pass using commer-\ncially available receiving equipment. These reference positions represent\nthe starting point for GP, so that rather than attempting to find an entirely\nnew orbit \"from scratch\", GP determines corrections to the broadcast ephemeris,\nwhich is a much simpler procedure.\nThe effectiveness of this idea can be demonstrated by simulation. For\nexample, Fig. 1 shows unknown site positioning uncertainty as a function of\nsatellite pass number for a two site GP solution using up to twenty passes\n(the solution is shown in sequential form). The unknown quantities consist of\nthree components of unknown site position, three components of satellite refer-\nence position (ephemeris) adjustments per pass (a total of 60 unknowns), plus\n40 measurement biases (2 per pass). In this simulation, it was assumed that\nthe orbit adjustments and measurement biases were independent from pass to pass\nas well as independent from a priori knowledge (i.e., the solution was fully\nunconstrained) Range difference doppler measurements were assumed, with a\nnoise standard deviation of 70 cm. and a sample interval of 25 seconds. For\nthis case, the site geometry was appreciably East-West, with a separation of\nabout 160 km. The twenty passes range in elevation from 27 degrees to 90\ndegrees. A total of 1,542 simulated observations was generated.\nShown in Fig. 2 are the solution uncertainties (in radial position) for\nthe per-pass reference orbit adjustments for the Fig. 1 simulation. The larger\nvalues (up to 180 meters) are for the higher elevation passes as one would expect.*\n* As mentioned above the GP solution shown is fully unconstrained, thus ex-\nplaining the large variations in orbit adjustment. The author is a strong\nbeliever in unconstrained solutions when processing real data. Possible\nreduction in accuracy is more than offset by higher reliability, particularly\nfor remote area operations where ephemeris prediction errors plus local\ndatum shift errors may be very uncertain.","430\nThe interesting feature of these results is that high orbit (reference\nposition) absolute accuracy in three dimensions is not required in order to\nachieve high unknown site positioning accuracy. The only requirement is that\nthe modeling of the deviations from the broadcast ephemeris be accurate for\neach pass. As it turns out, satisfactory modeling can easily be achieved\nthrough the use of advanced estimation theory concepts. This fact will be\ndemonstrated in the results shown in the next sections of this paper.\nIt should be mentioned that the simulation discussed above did not take\ninto account the presence of measurement systematic errors other than simple\nbiases (timing errors) This was done purposely since the real data GP\nprocessing system developed at ATL does respond to the additional errors (such\nas unmodeled refraction errors), and it was of interest to see if the real\ndata GP solution precision can approach that suggested by the \"ideal\" simulation.\nGP Implementation Considerations\nAlthough implementation of the GP concept is basically quite simple\n(compared to SA, for example), a number of practical problems had to be\novercome. The most important of these were:\nProblem 1) Effective data editing;\nProblem 2) Parameterization of all significant measurement system-\natic errors, including residual tropospheric and\nionospheric refraction errors and ephemeris correction\nfunctions;\nProblem 3) Implementation via a small (mini) computer suitable for\nfield use;\nProblem 4) Ease of operation by unskilled personnel.\nProblem 1) is one of the most important (if not the most important) con-\nsideration in any real data processing system of this type. Deciding what\nconstitutes a \"bad\" data point while retaining all \"good\" points in order to\nmaintain highest possible efficiency is not a trivial exercise. Furthermore,\na positive method was required for determining whether an entire set of\nmeasurements from a given pass is \"bad\", since deletion of passes represents\nincreased on-site time and investment. In the ATL GP system, two levels of\nediting are employed: a \"Fine Edit\" for point by point editing and a \"Macroedit\"\nfor pass editing. The Fine Edit system is self-adaptive, fully automatic and\nnot requiring operator intervention. At the present time Macroedit can be\ncontrolled by the operator so that highest on-site data utilization efficiency\ncan be maintained. However, based on many months of testing, it appears that\nthe Macroedit decision levels can be effectively automated in the near future.\nProblem 2) would normally require a large computational capability to\nsolve in a formal way. However, for the past decade or so the author has\nspecialized in investigating means for reducing computational requirements in\nnon-linear optimum estimation applications such as this. Some of the techni-\nques discovered and perfected during this time have been implemented in the","431\nATL GP system. As a result, the estimator will respond to and remove all\nobservable systematic errors, irrespective of their source. This can be\nproved by simulation, but is better proved by comparing the real data processing\nresults with expected precision given by simulation based on simplified models.\nThis will be presented in later sections of this paper.\nThe solution to Problem 4) also follows logically from the above discussions.\nThe basic concept of the GP technique does not require knowledge in orbital\nmechanics or estimation, and the design of the ATL GP algorithm is such that\noperations of editing and error modeling are performed automatically. In fact,\nsince the GP system can accept all passes without pre-editing, it is far\nsimpler to use than translocation (TL). The self-adaptive and unconstrained\nfeatures of the system also simplify operation by avoiding the need for statis-\ntical inputs by the operator.\nDemonstration of the ATL GP System\nBy way of preliminaries, the author would like to propose a new evaluation\ncriteria to the satellite positioning user: the presentation of results based\nupon the processing of consecutive received passes (CRP), or, in the case of\nTL, SA, and GP the processing of consecutive received simultaneous passes (CSRP).\nThe proliferation of accuracy quotations, bullseye plots, etc., without quali-\nfication in the past has led to considerable user uncertainty as to just how\nmany passes actually received by a given receiver are necessary in order to\nrealize a target accuracy. \"40 or 50 good passes\" is meaningless to a user if\nsubstantial pass editing is necessary to get the results quoted. On the other\nhand, performance figures based on the acquisition and processing of consecutive\nreceived passes will give the user a better idea of how to plan his budget for\npositioning work. Any pass editing that is required can be noted separately\nto relate the results to actual passes processed.\nSince the ATL COMPUNAV/GP* system is unconstrained statistically, an\neffective way to demonstrate its performance is to compare solutions based on\nthe processing of consecutive batches of data gathered during the same field\noperation. The North Sea project gave an excellent opportunity to carry out\nsuch a demonstration because of the great quantity of simultaneous passes\nrecorded.\nAs mentioned earlier, seven receivers were mobilized for the project.\nThree of the receivers were the Magnovox 702A navigation receiver, while the\nother four were the JMR-1 land survey set. Three JMR receivers was located\non the platform and the other two in Norway. In this paper, the GP solutions\nbased on the use of simultaneous measurements from the platform receiver and\nthe Magnavox receiver located at Hellisoy Fyr, near Bergen, Norway, will be\nshown.\nTen batches of observations were processed as indicated in Table I. All\npasses input to the GP system are consecutive simultaneous received passes as\ndiscussed above, with no pre-editing, and only Macroediting as noted in Table 1.\n* Registered trademark of ATL, Inc.","432\nThe Appendix contains the actual COMPUNAV/GP Data Summaries for each run,\nshowing, among other things, each pass lock-on time and maximum elevation\nangles to both the unknown and control sites. Each batch solution was obtained\nusing field-operational procedures.\nFigure 3 shows UTM grid coordinates of each Set 1 solution with respect\nto the overall best estimate of unknown site position. These deltas are also\nlisted in Table I for reference. Figure 4 shows the elevation deltas plotted\nas a function of run index.\nAN (m)\nAE(m)\nAU(m)\nTOTAL OBS.\nNO. PASSES\nCSRP\nRUN.\n(BOTH SITES)\nEDITED\nNO.\n4.2\n1.7\n-8.4\n774\n5.013\n16\n3\n483\n9.5\n-4.5\n-6.9\n5.186\n11\n3\n-1.5\n3.5\n-1.5\n874\n5.240\n16\n2\n-1.2\n0.4\n7.8\n735\n16\n3\n5.340\n2.8\n1.7\n-0.7\n670\n5.395\n15\n4\n-10.6\n719\n-1.8\n-0.5\n16\n3\n5.450\n-0.1\n-3.1\n-9.7\n781\n0\n5.460\n16\n1.7\n445\n2.2\n13.4\n2\n5.514\n10\n-3.4\n847\n-2.8\n3.1\n2\n5.611\n17\n-1.5\n851\n4.0\n1.5\n2\n5.769\n18\n6.3\n5.1\nRMS\n3.8\nTable I\nSet 1 GP Solutions\nThe rms of the deltas in Table I is not indicative of true rms since it\nincludes solutions involving different batch sizes (and hence uncertainties) .\nBetter consistency can be obtained by optimally combining the results of two\nconsecutive batches giving more or less equal processed total passes. Performing\nthis operation on the solutions shown in Table I leads to five solutions shown\nin Table II and plotted in Figs. 5 and 6. *\nDiscussion\nThe ultimate precision that can be expected from any two-site unconstrained\nshort-arc class of processing technique (based on the use of range difference\nmeasurements) is given by the simulation mentioned earlier and whose results\nThere was some suspicion that the control site receiver may still have been\nin the warm-up mode when data recording began, thus causing extraordinary\nerrors in the first GP solutions. However, this could not be verified, so\nthat in the spirit of unbridled honesty these results are included.","433\nare plotted in Figs. 1 and 2. Comparison of the final results in Table II\nwith the expected final values shown in Fig. 1 shows a gratifying similarity.\nRemoving the first (questionable) run from Table II leads to rms values of\n1.5, 2.9, and 2.9m. in North, East and Up directions, respectively. These\nvalues are about twice as large as the theoretical values from the simulation\n(based on the processing of twenty \"ideal\" passes), and this difference can\nlargely be attributed to the larger measurement (white) noise levels encouraged\nin the real world.\nAU(m)\nAN(m)\nAE(m)\nCSRP\nNET\nRUN\nPASSES\nCOMBINATION\n4.4\n-6.3\n0.6\n21\n5.013+5.186\n27\n-1.4\n2.3\n3.4\n27\n32\n5.240+5.340\n2.3\n-2.5\n31\n24\n0.3\n5.395+5.450\n-2.1\n-2.7\n0.9\n26\n24\n5.460+5.514\n2.8\n-2.4\n31\n-0.3\n5.611+5.769\n35\n3.6\n2.5\nRMS\n2.5\nTable II\nSet 2 GP Solutions\nIn the North Sea project data, the measurement noise levels fluctuated\nconsiderably, from the theoretical minimum of about 70 cm (one count) to\nseveral meters (particularly in the higher elevation passes) Thus it would\nappear that environmental effects play a large part, not just the receiving\nhardware, so that an across-the-board reduction of noise level may not be\npossible. Even so, reduction of the random measurement noise levels is an\narea of investigation that should definitely be pursued to try and improve\nthe positioning accuracy realizable from a given number of simultaneous\npasses. This topic is discussed further in the last section of this paper.\nThe Table II results imply that the COMPUNAV/GP system has effectively\nremoved substantially all of the significant systematic error, both in the\nmeasurements as well as in the reference orbit adjustments. This means that\nthe ultimate precision of the system is virtually unlimited as more and\nmore passes are processed, a characteristic which cannot be claimed by any\ntype of point positioning method since residual systematic errors in the\npredicted ephemeris always remain. As a result, the GP technique (or in\nfact any type of SA method) of satellite positioning offers by far the\ngreatest potential accuracy of all other techniques.\nIn terms of data utilization, Table II shows that the GP system required\ndeletion of 24 passes out of a total CSRP of 150, representing a data loss\nrate of 16%. In comparison, commonly used point positioning methods generally\nexhibit a pass loss rate of up to 50%, and TL usually exhibits an even higher\nrate due to the need for pre-editing of passes to process. Thus the GP approach\ndoes indeed make more efficient use of recorded data as claimed at the beginning\nof this paper.","434\nComparisons with First-Order Geodetic Control\nThe author believes that dispersion studies as described in this paper\nare the most important means for validating the actual precision of any\nunconstrained statistical data processing technique. However, many workers\nand users in the geodetic community believe that comparisons with independently-\nderived results are equally if not more important. This is certainly true if\nit can be guaranteed that the accuracy of the independent determinations\nexceeds the accuracy of the satellite technique.\nFor the North Sea project, measurements were made simultaneously from\nfive first-order geodetic control points (one of the on-shore receivers failed\nto provide usable data). Thus, five (pairwise) solutions for the platform\nposition were produced at ATL, and dispersion of the five solutions would\nbe caused by the combined effects of processing error plus geodetic control\nerrors.\nThe ATL results which were produced shortly after the data were gathered\nindicated the presence of a possibly significant longitude difference of\nseveral meters between the ED50 control in the UK and Norway. Since this type\nof investigation was not part of ATL's contractual responsibilities, the\nauthor feels that it would not be prudent to present these results at this\ntime. As mentioned earlier in the paper, a detailed investigation of this\naspect of the project is continuing by the responsible Government agencies,\nand it is expected that a joint report will be prepared some time in the\nfuture.\nWithin both the UK and Norway, the ATL results agreed to within the\nexpected uncertainties. In the UK, the two determinations differed by 1.5 m\nin longitude and 5 m in latitude. In Norway, the Eigeberg station and\nSkibmannshei station determinations differed by 1.2 m in longitude and 1.6 m\nin latitude. The Hellisoy Fyr determination differed from the other two\nNorwegian points by less than 1 m in longitude, but by about 5 m in latitude.\nThe author was informed by Norwegian Participants that the latitude offset\nfor Hellisoy could be explained by a newly-discovered discrepancy in the\ncomputations of the ED50 locations for the marker location there.\nAreas for Further Investigation\nATL is continuing to investigate the characteristics of doppler measure-\nment errors to try and further improve overall satellite positioning accuracy.\nFor example, for the receivers used for the North Sea project, high elevation\npasses (i.e., above 70 degrees) consistently produced much higher levels of\nrandom measurement noise combined with higher data drop-out rates. Since the\nhigher passes are essential for precise determination of antenna elevation,\nit is important to try and reduce these types of errors.\nWe have also begun implementation of processing based on the use of\npseudo-range measurements to see what practical advantage, if any, their use\nmight provide. Theoretically, the purely random (white) noise in pseudo-range\nis reduced through the integration, which is definitely a plus. However, low\nfrequency error observability is reduced, and low frequency errors become more","435\ncomplex (spikes go to step functions, step functions to ramps, etc.) which\nmakes effective editing more difficult. At the present time, the author\nbelieves that potential accuracy gain through the use of pseudo-range due to\nreduced white noise level is more than offset by the effects of the more\ncomplex low frequency errors, particularly for field minicomputer implementation.\nHowever, if the user has enough time and available measurements for careful\nmassaging, the use of pseudo-range might yield significantly higher precision.\nFinally, consideration has been given to the use of more than one\ncontrol site in a given network. In fact, the \"home office\" version of the\nATL COMPUNAV/GP system can accept up to three control sites, and although no\nrigorous study using more than one control site has yet been undertaken, the\nstatistics indicate that about 30% improvement in overall unknown site position-\ning precision can be expected with each additional control site (assuming\nuniform receiver noise and no control location error). This would imply that\nunknown site positioning accuracies of a few tenths of a meter should be\nroutinely possible for a (up to 800 km network) adjustment based on the\nprocessing of only a few passes.","436\n20-00\nAMERICAN\n00.02\n00.0\n00 001\n00.08\n00.09\n00.01\n00.021\n( ) TOTAL","437\n32.00\n28.00\nCP SIMULATION RESULTS: PER-PASS ORBIT ADJUST UNCERTAINTIES\n24.00\n20.00\nPASS NUMBER\n0\n16.00\nFIGURE 2\n()\n0\n12.00\n8.00\n4.00\n0.00\n00\n0\n202-00\n80.00\n100.00\n210-00\n200-00","438\n00\nSET 1 UTM GRID DELTAS(METERS)\n10:00\n*\n*\nX\n*\n*\nEAST\n00.\n00.01-\n00.5-\n00.01\n00\n00.51\nS\n-\n*\nx\n*\nx\n*\n00\nFIGURE 3","439\nSET 1 ELEVATION DELTAS\n10.00\n8.00\n6.00\n4.00\n2.00\n00\n0\n*\n*\nFIGURE 4","440\n15:00\nSET 2 UTM GRID DELTAS (METERS)\n10:00\n*\nEAST\n*\n*\n00-si-\n00.01-\n00.-\n00\n00.01\n00.51\nS\nx\n*\nFIGURE 5","441\n00\nSET 2 ELEVATION DELTAS\n*\n*\n5.00\n2.00\n3.00\n4.00\n1.00\n0\n00\nOCTIP\n*\nFIGURE 6","442\nAPPENDIX\nCOMPUNAV/GP PROCESSING SUMMARIES\nIntroduction\nIncluded in this Appendix are the Processing Summaries for the GP runs\nsummarized in Table I of this paper. The heading identifiers in each summary\nare defined as follows:\nREF: Pass number in batch;\nPass lock-on day;\nLD:\nLM:\nPass lock-on minute;\nMaximum elevation angle (deg) to unknown site;\nEU:\nNumber of doppler observations from unknown site\nNU:\n(24 second interval);\nFEU: Number of Fine Edits in unknown site measurements;\nMaximum elevation angle (deg) to control site;\nEC:\nNumber of doppler observations from control site;\nNC:\nFEC: Number of Fine Edits in control site measurements.","443\nRUN 5.013\nPROCESSING SUMMARY\nREF\nLD\nLM\nEU\nNU\nFEU\nEC\nHC\nFEC\n1\n270\n1336\n18.\n30\n0\n21.\n32\n2\n2\n32\n270\n1408\n25.\n32\n0\n23.\n0\n3\n271\n65.\n34\n0\n57.\n34\n6\n1\n5\n271\n144\n33.\n38\n1\n38.\n39\n1\n6\n271\n216\n13.\n20\n0\n12.\n21\n0\n8\n271\n332\n23.\n29\n0\n27.\n30\n0\n9\n271\n350\n17.\n30\n0\n20.\n32\n0\n10\n271\n412\n17.\n30\n0\n20.\n32\n0\n11\n271\n436\n83.\n13\n0\n83.\n14\n2\n13\n271\n518\n57.\n33\n5\n64.\n34\n3\n14\n271\n542\n25.\n30\n0\n22.\n31\n0\n15\n271\n564\n46.\n33\n2\n42.\n33\n0\n18\n271\n764\n86.\n29\n6\n81.\n29\n4","444\nRUN\n5.186\nPROCESSING SUMMARY\nEU\nNU\nFEU\nEC\nHC\nFEC\nREF\nLD\nLM\n33\n2\n26.\n33\n0\n271\n870\n27.\n1\n20.\n1146\n17.\n28\n1\n29\n1\n4\n271\n0\n0\n67.\n0\n0\n5\n271\n1192\n59.\n6\n271\n1250\n57.\n32\n4\n65.\n32\n2\n37\n10\n271\n1386\n32.\n36\n4\n37.\n4\n11\n271\n1426\n6.\n16\n0\n8.\n20\n0\n12\n272\n26\n13.\n24\n0\n12.\n25\n0\n13\n272\n52\n79.\n0\n0\n70.\n0\n0\n14\n272\n96\n21.\n0\n0\n25.\n0\n0\n15\n272\n160\n24.\n32\n0\n22.\n32\n0\n17\n272\n310\n44.\n3.7\n3\n41.\n37\n1","445\nRUN\n5.240\nPROCESSING SUMMARY\nREF\nLD\nLM\nEU\nNU\nFEU\nEC\nNC\nFEC\n19\n272\n1436\n59.\n32\n6\n68.\n32\n4\n18\n272\n1416\n22.\n27\n0\n20.\n27\n0\n17\n272\n1356\n21.\n31\nC\n20.\n32\nC\n16\n272\n1332\n20.\n0\n0\n22.\n0\n0\n15\n272\n1304\n73.\n31\n2\n65.\n33\n2\n14\n272\n1230\n36.\n33\n4\n33.\n33\n0\n3\n272\n1020\n18.\n29\n0\n21.\n30\n0\n8\n272\n708\n50.\n37\n4\n58.\n38\n1\n7\n272\n680\n23.\n30\n0\n21.\n30\n0\n6\n272\n622\n23.\n29\n2\n22.\n29\n1\n5\n272\n602\n15.\n29\nC\n18.\n31\n0\n4\n272\n574\n75.\n30\n4\n67.\n33\n4\n3\n272\n516\n76.\n24\n4\n69.\n26\n4\n2\n272\n468\n33.\n34\n0\n38.\n34\n0\n1\n272\n408\n33.\n35\n1\n38.\n35\n2","446\nRUN 5.340\nPROCESSING SUMMARY\nREF\nLD\nLM\nEU\nNU\nFEU\nEC\nNC\nFEC\n20\n273\n886\n45.\n38\n0\n51.\n39\n2\n19\n273\n866\n26.\n33\n0\n25.\n33\n0\n17\n273\n760\n86.\n11\n4\n78.\n12\n1\n16\n273\n680\n5.\n0\n0\n6.\n0\n0\n15\n273\n654\n28.\n34\n0\n32.\n34\n4\n13\n273\n576\n38.\n29\n1\n35.\n29\n1\n12\n273\n516\n32.\n27\n0\n29.\n28\n0\n11\n273\n466\n66.\n23\n2\n75.\n23\n1\n10\n273\n408\n67.\n29\n3\n76.\n29\n2\na\n273\n360\n20.\n33\n0\n23.\n34\n0\n8\n273\n304\n18.\n27\n0\n21.\n29\n3\n5\n273\n204\n5.\n0\n0\n6.\na\n0\n3\n273\n104\n42.\n36\n0\n38.\n37\n0\n2\n273\n86\n6.\n12\n0\n6.\n13\n0\n1\n273\n46\n13.\n26\n0\n16.\n28\n0","447\nRUN 5.335\nPROCESSING SUMMARY\nREF\nLD\nLM\nEU\nHU\nFEU\nEC\nNC\nFEC\n19\n274\n470\n38.\n36\n0\n44.\n37\n0\n18\n274\n446\n72.\n30\n3\n63.\n32\n2\n16\n274\n344\n30.\n0\n0\n35.\n0\n0\n14\n274\n214\n76.\n28\n2\n84.\n29\n0\n13\n274\n156\n23.\n32\n0\n21.\n33\n1\n10\n273\n1382\n33.\n35\n0\n38.\n37\n2\n9\n273\n1360\n37.\n36\n0\n33.\n36\n0\n8\n273\n1308\n37.\n4\n0\n33.\n18\n0\n6\n273\n1252\n66.\n28\n4\n75.\n28\n2\n5\n273\n1198\n72.\n31\n3\n81.\n31\n3\n4\n273\n1148\n20.\n31\n0\n23.\n33\n0\n3\n273\n1094\n22.\n32\n0\n26.\n33\n4","448\nRUN\n5.450\nPROCESSING SUMMARY\nREF\nLD\nLM\nEU\nNU\nFEU\nEC\nNC\nFEC\n20\n275\n38\n4.\n0\n0\n5.\n3\n0\n19\n274\n1416\n19.\n30\n0\n18.\n31\n0\n18\n274\n1366\n18.\n27\n0\n16.\n28\n0\n16\n274\n1256\n57.\n29\n1\n51.\n29\n0\n15\n274\n1228\n5.\n9\n0\n7.\n16\n0\n12\n274\n994\n14.\n21\n0\n17.\n22\n0\n10\n274\n918\n15.\n26\n0\n14.\n26\n0\n9\n274\n840\n28.\n32\n2\n33.\n32\n3\n8\n274\n810\n46.\n28\n3\n42.\n28\n4\n7\n274\n708\n53.\n29\n2\n60.\n29\n2\n4\n274\n632\n20.\n29\n0\n18.\n30\n4\n3\n274\n578\n65.\n34\nS\n59.\n38\n2\n2\n274\n556\n19.\n24\n0\n17.\n24\n0\n1\n274\n524\n83.\n31\nI\n57.\n34\n2","449\nRUN 5.460\nPROCESSING SUMMARY\nFEC\nEC\nNC\nREF\nLD\nLM\nEU\nNU\nFEU\n19\n2\n20\n275\n1000\n30.\n9\n0\n33.\n0\n54.\n26\n0\n62.\n26\n19\n275\n898\n32\n0\n24.\n33\n2\n18\n275\n862\n25.\n17\n275\n790\n18.\n32\n3\n21.\n34\n2\n16\n275\n756\n82.\n27\n4\n74.\n28\n5\n15\n275\n740\n10.\n13\n0\n10.\n13\n0\n14\n275\n688\n6.\n12\n0\n8.\n18\n0\n13\n275\n632\n33.\n28\n0\n31.\n28\n0\n12\n275\n582\n31.\n34\n0\n29.\n35\n0\n83.\n11\n275\n526\n75.\n31\n5\n33\n4\n10\n275\n476\n79.\n32\n7\n89.\n32\n7\n7\n275\n312\n8.\n20\n0\n6.\n14\n0\nI.\n21\n0\n6\n275\n262\n7.\n16\n2\n28\n1\n3\n275\n104\n40.\n27\n0\n36.\n0\n5.\n6\n0\n5.\n8\n2\n275\n90\n32\n0\n19.\n34\n0\n1\n275\n56\n16.","450\nRUN\n5.514\nPROCESSING SUMMARY\nEC\nNC\nFEC\nREF\nLD\nLM\nEU\nNU\nFEU\n0\n1\n275\n1426\n8.\n18\n0\n8.\n19\n3\n276\n34\n10.\n20\n0\n9.\n21\n0\n0\n1\n20.\n33\n4\n276\n152\n22.\n32\n29\n1\n8\n276\n368\n14.\n27\n1\n16.\n9\n276\n418\n85.\n28\n4\n81.\n29\n2\n10\n276\n476\n44.\n34\n1\n50.\n34\n0\n28\n0\n11\n276\n524\n24.\n27\n0\n22.\n20\n276\n1158\n53.\n33\n3\n60.\n33\n0","451\nRUN 5.611\nPROCESSING SUMMARY\nREF\nLD\nLM\nEU\nNU\nFEU\nEC\nNC\nFEC\n1\n276\n1178\n60.\n20\n5\n54.\n21\n0\n2\n276\n1208\n44.\n29\n1\n50.\n30\n1\n3\n276\n1268\n47.\n30\n5\n42.\n33\n1\n1314\n4\n276\n55.\n32\n1\n50.\n32\n1\n5\n276\n1420\n17.\n28\n0\n16.\n29\n0\n9\n277\n206\n63.\n23\n0\n64.\n24\n0\n10\n277\n250\n11.\n21\n0\n14.\n22\n0\n11\n277\n270\n9.\n20\n0\n11.\n25\n0\n12\n277\n316\n8.\n18\n0\n10.\n22\n1\n13\n277\n352\n39.\n26\n0\n46.\n27\n0\n14\n277\n378\n29.\n36\n1\n34.\n36\n1\n15\n277\n422\n26.\n35\n0\n30.\n37\n1\n16\n277\n484\n84.\n0\n0\n76.\n13\n12\n17\n277\n530\n85.\n31\n5\n84.\n32\n3\n18\n277\n564\n14.\n23\n0\n13.\n24\n0\n20\n277\n636\n29.\n34\n1\n27.\n34\n0","452\nRUN 5.769\nPROCESSING SUMMARY\nREF\nLD\nLM\nEU\nNU\nFEU\nEC\nNC\nFEC\n20\n278\n328\n18.\n25\n0\n21.\n26\n0\n19\n278\n222\n5.\n3\n0\n6.\n11\n0\n18\n278\n186\n4.\n0\n0\n6.\n11\n0\n17\n278\n148\n21.\n31\n0\n19.\n32\n0\n16\n278\n124\n36.\n0\n0\n41.\n0\n0\n15\n278\n40\n8.\n18\n0\n8.\n19\n0\n14\n278\n18\n12.\n27\n0\n15.\n29\n0\n12\n277\n1368\n28.\n31\n0\n26.\n31\n0\n11\n277\n1318\n12.\n20\n0\n13.\n21\n0\n10\n277\n1260\n84.\n32\n4\n84.\n32\n2\n9\n277\n1212\n36.\n33\n2\n33.\n34\n0\n8\n277\n1154\n26.\n33\n0\n30.\n35\n0\n7\n277\n1106\n65.\n30\n4\n73.\n30\n3\n6\n277\n1002\n19.\n30\n6\n22.\n31\n0\n5\n277\n964\ni.\n14\n0\n7.\n15\n0\n4\n277\n858\n24.\n32\n0\n23.\n32\n1\n3\n277\n800\n22.\n35\n3\n25.\n35\n2\n1\n277\n700\n7.\n16\n0\n9.\n17\n0"]}