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Colorado geoid computation experiment: overview and summary
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2021
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Source: Journal of Geodesy, 95(12)
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Journal Title:Journal of Geodesy
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Description:The primary objective of the 1-cm geoid experiment in Colorado (USA) is to compare the numerous geoid computationmethods used by different groups around the world. This is intended to lay the foundations for tuning computation methodsto achieve the sought after 1-cm accuracy, and also evaluate how this accuracy may be robustly assessed. In this experiment,(quasi)geoid models were computed using the same input data provided by the US National Geodetic Survey (NGS), but usingdifferent methodologies. The rugged mountainous study area (730 km×560 km) in Colorado was chosen so as to accentuateany differences between the methodologies, and to take advantage of newly collected GPS/leveling data of the Geoid SlopeValidation Survey 2017 (GSVS17) which are now available to be used as an accurate and independent test dataset. Fourteengroups from fourteen countries submitted a gravimetric geoid and a quasigeoid model in a 1′×1′grid for the study area, aswell as geoid heights, height anomalies, and geopotential values at the 223 GSVS17 marks. This paper concentrates on thequasigeoid model comparison and evaluation, while the geopotential value investigations are presented as a separate paper(Sánchez et al. in J Geodesy 95(3):1.https://doi.org/10.1007/s00190-021-01481-0, 2021). Three comparisons are performed:the area comparison to show the model precision, the comparison with the GSVS17 data to estimate the relative accuracyof the models, and the differential quasigeoid (slope) comparison with GSVS17 to assess the relative accuracy of the heightanomalies at different baseline lengths. The results show that the precision of the 1′×1′models over the complete area is about2 cm, while the accuracy estimates along the GSVS17 profile range from 1.2 cm to 3.4 cm. Considering that the GSVS17does not pass the roughest terrain, we estimate that the quasigeoid can be computed with an accuracy of~2 cm in Colorado.The slope comparisons show that RMS values of the differences vary from 2 to 8 cm in all baseline lengths. Although the2-cm precision and 2-cm relative accuracy have been estimated in such a rugged region, the experiment has not reached the1-cm accuracy goal. At this point, the different accuracy estimates are not a proof of the superiority of one methodologyover another because the model precision and accuracy of the GSVS17-derived height anomalies are at a similar level. Itappears that the differences are not primarily caused by differences in theory, but that they originate mostly from numericalcomputations and/or data processing techniques. Consequently, recommendations to improve the model precision toward the1-cm accuracy are also given in this paper.
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Source:Journal of Geodesy, 95(12)
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Rights Information:Public Domain
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Compliance:Submitted
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