NOAA Technical Memorandum NESDIS NGDC-9 DIGITAL ELEVATION MODEL OF BILOXI, MISSISSIPPI: PROCEDURES, DATA SOURCES AND ANALYSIS L.A. Taylor B.W. Eakins K.S. Carignan R.R. Warnken T. Sazonova D.C. Schoolcraft National Geophysical Data Center Marine Geology and Geophysics Division Boulder, Colorado January 2008 NOAA Technical Memorandum NESDIS NGDC-9 DIGITAL ELEVATION MODEL OF BILOXI, MISSISSIPPI: PROCEDURES, DATA SOURCES AND ANALYSIS Lisa A. Taylor¹ Barry W. Éakins² Kelly S. Carignan² Robin R. Warnken¹ Tatiana Sazonova² David C. Schoolcraft¹ ¹NOAA, National Geophysical Data Center, Boulder, Colorado ²Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder National Geophysical Data Center Marine Geology and Geophysics Division Boulder, Colorado January 2008 NOTICE Mention of a commercial company or product does not constitute an endorsement by the NOAA National Environmental Satellite, Data, and Information Service. Use of information from this publication concerning proprietary products or the test of such products for publicity or advertising purposes is not authorized. Corresponding author contact: Lisa A. Taylor NOAA, National Geophysical Data Center Marine Geology and Geophysics Division 325 Broadway, E/GC 3 Boulder, Colorado 80305 Phone: 303-497-6767 Fax: 303-497-6513 E-mail: Lisa.A.Taylor@noaa.gov http://www.ngdc.noaa.gov/mgg/inundation/ Also available from the National Technical Information Service (NTIS) (http://www.ntis.gov) CONTENTS 1. Introduction ..................................................................................................................................................1 2. Study Area..................................................................................................................................................2 3. Methodology .............................................................................................................................................2 3.1 Data Sources and Processing .............................................................................................................3 3.1.1 Shoreline....................................................................................................................................4 3.1.2 Bathymetry ...............................................................................................................................9 3.1.3 Topography.............................................................................................................................15 3.1.4 Topography–Bathymetry ......................................................................................................22 3.2 Establishing Common Datums .......................................................................................................24 3.2.1 Vertical datum transformations .............................................................................................24 3.2.2 Horizontal datum transformations.........................................................................................24 3.3 Digital Elevation Model Development ..........................................................................................25 3.3.1 Verifying consistency between datasets ...............................................................................25 3.3.2 Smoothing of bathymetric data ..........................................................................................25 3.3.3 Gridding the data with MB-System.....................................................................................26 3.4 Quality Assessment of the DEM.....................................................................................................27 3.4.1 Horizontal accuracy .............................................................................................................27 3.4.2 Vertical accuracy ................................................................................................................27 3.4.3 Slope maps and 3-D perspectives.......................................................................................27 3.4.4 Comparison with source data files.....................................................................................29 3.4.5 Comparison with NGS geodetic monuments ..................................................................30 4. Summary and Conclusions.....................................................................................................................31 5. Acknowledgments.................................................................................................................................31 6. References .............................................................................................................................................31 7. Data Processing Software .....................................................................................................................31 LIST OF FIGURES Figure 1. Color image of the Biloxi, Mississippi DEM .............................................................................1 Figure 2. Barrier islands in Mississippi Sound..........................................................................................2 Figure 3. Source and coverage of datasets used to compile the Biloxi DEM ........................................3 Figure 4. NOAA Electronic Navigational Charts available in the Biloxi region .....................................5 Figure 5. Detail of coastline datasets available for Biloxi DEM at Biloxi Bay .......................................6 Figure 6. Digital coastline segments used to create a ‘combined coastline’ for the Biloxi region ..........7 Figure 7. Chandeleur Island Chain morphology, pre-2005 and post-Katrina ........................................8 Figure 8. Digital NOS hydrographic survey coverage in the Biloxi region ...........................................11 Figure 9. Location of USACE survey data within dredged shipping channels in the Biloxi region ......12 Figure 10. ENC sounding data used in the Biloxi DEM .....................................................................13 Figure 11. Detailed view of RNC #11371 at Karako Bay.....................................................................14 Figure 12. Source and coverage of topographic datasets used in building the Biloxi DEM..................16 Figure 13. Color image of the NED DEM .............................................................................................17 Figure 14. Color image of Harrison County DEM................................................................................18 Figure 15. Spatial coverage of CSC topographic LiDAR datasets for the Biloxi DEM.......................19 Figure 16. CSC LiDAR merged post-Katrina dataset showing a “hill” at Bayou Casotte ..................20 Figure 17. Images of RNC #11373 and NED data at Bayou Casotte..................................................20 Figure 18. Chevron Refinery at Bayou Casotte..................................................................................21 Figure 19. Spatial coverage of topographic/ bathymetric datasets used in Biloxi DEM .....................22 Figure 20. Slope map of the Biloxi DEM .............................................................................................28 Figure 21. Histogram: post-Katrina JALBTCX LiDAR survey and the Biloxi DEM..........................29 Figure 22. Histogram: NOS hydrographic survey and the Biloxi DEM .............................................29 Figure 23. Histogram: NGS geodetic monument elevations and the Biloxi DEM .............................30 Figure 24. Location of NGS monuments and NOAA tide stations in the Biloxi region.....................30 LIST OF TABLES Table 1. PMEL specifications for the Biloxi, Mississippi DEM.................................................................2 Table 2. Shoreline datasets used in compiling the Biloxi DEM..................................................................4 Table 3. NOAA nautical charts in the Biloxi, Mississippi region.............................................................4 Table 4. Bathymetric datasets used in compiling the Biloxi DEM............................................................9 Table 5. Digital NOS hydrographic surveys used in compiling the Biloxi DEM .................................9 Table 6. USACE bathymetric surveys used in compiling the Biloxi DEM.............................................12 Table 7. Topographic datasets used in compiling the Biloxi, Mississippi DEM.....................................15 Table 8. Combined topographic–bathymetric datasets used in compiling the Biloxi DEM.....................22 Table 9. Relationship between Mean High Water and other vertical datums in the Biloxi region..........24 Table 10. Data hierarchy used to assign gridding weight in MB-System..................................................26 Digital Elevation Model of Biloxi, Mississippi: Procedures, Data Sources and Analysis 1. INTRODUCTION In March 2007, the National Geophysical Data Center (NGDC), an office of the National Oceanic and Atmospheric Administration (NOAA), developed a bathymetric–topographic digital elevation model (DEM) centered on Biloxi, Mississippi (Fig. 1) for the Pacific Marine Environmental Laboratory (PMEL) NOAA Center for Tsunami Research (http://nctr.pmel.noaa.gov/). The 1/3 arc-second¹ coastal DEM will be used as input for the Method of Splitting Tsunami (MOST) model developed by PMEL to simulate tsunami generation, propagation and inundation. The DEM was generated from diverse digital datasets in the region (grid boundary and sources shown in Fig. 3) and will be used for tsunami inundation modeling, as part of the tsunami forecast system SIFT (Short-term Inundation Forecasting for Tsunamis) currently being developed by PMEL for the NOAA Tsunami Warning Centers. This report provides a summary of the data sources and methodology used in developing the Biloxi DEM. ![Color image of the Biloxi, Mississippi DEM.](page_354_682_1092_627.png) Figure 1. Color image of the Biloxi, Mississippi DEM. 1. The Biloxi DEM is built upon a grid of cells that are square in geographic coordinates (latitude and longitude), however, the cells are not square when converted to projected coordinate systems, such as UTM zones (in meters). At the latitude of Biloxi, Mississippi (30°24' N, 88°53.3' W) 1/3 arc-second of latitude is equivalent to 10.26 meters; 1/3 arc-second of longitude equals 8.90 meters. 2. Study Area The Biloxi DEM covers the coastal region surrounding Biloxi, Mississippi, including the communities of Gulfport and Pascagoula (Fig. 1), as well as the offshore areas of the Mississippi Sound, Chandeleur Sound, and the Gulf Islands. The Chandeleur Islands (e.g., Fig 2) have undergone coastal erosion and changes in sediment deposition that have modified the shoreline in the geologically short time span of 150 years. More recently, the 2005 hurricane season severely impacted the landscape and economy of the Mississippi Gulf Coast region. Hurricanes Arlene, Cindy, Dennis, and Katrina made landfall in the area between June and August 2005, dramatically changing the shape of the coastline. ![Barrier Islands in Mississippi Sound](page_374_682_1097_377.png) Figure 2. Barrier Islands in Mississippi Sound (http://pubs.usgs.gov/of/2005/1151/images/fig1LG.jpg). 3. Methodology The Biloxi DEM was developed to meet PMEL specifications (Table 1), based on input requirements for the MOST inundation model. The best available digital data were obtained by NGDC and shifted to common horizontal and vertical datums: World Geodetic System 1984 (WGS84) and Mean High Water (MHW), for modeling of “worst-case scenario” flooding, respectively. Data processing and evaluation, and DEM assembly and assessment are described in the following subsections.
Grid Area Biloxi, Mississippi
Coverage Area 88.3° to 89.3° W; 29.7° to 30.6° N
Coordinate System Geographic decimal degrees
Horizontal Datum World Geodetic System 1984 (WGS84)
Vertical Datum Mean High Water (MHW)
Vertical Units Meters
Grid Spacing 1/3 arc-second
Grid Format ESRI ASCII raster grid
Table 1: PMEL specifications for the Biloxi, Mississippi DEM. 3.1 Data Sources and Processing Shoreline, bathymetric, topographic and combined topographic–bathymetric digital datasets (Fig. 3) were obtained from several U.S. federal and state agencies, including: NOAA’s National Ocean Service (NOS) and Coastal Services Center (CSC); the U.S. Geological Survey (USGS); the U.S Army Corps of Engineers (USACE); the Mississippi Office of Geology (MOG), Coastal Geology and Energy Division; and the Mississippi Automated Resource Information System (MARIS). Safe Software’s (http://www.safe.com/) FME data translation tool package was used to shift datasets to WGS84 horizontal datum and to convert them into ESRI (http://www.esri.com/) ArcGIS shape files. The shape files were then displayed with ArcGIS to assess data quality and manually edit datasets; NGDC’s GEODAS software (http://www.ngdc.noaa.gov/mgg/geodas/) was used to manually edit large xyz datasets. Vertical datum transformations to MHW were also accomplished using FME, based upon data from local NOAA Biloxi tidal stations. VDatum model software (http://vdatum.noaa.gov/) was not available for this area. ![Map showing source and coverage of datasets used to compile the Biloxi DEM, with legend indicating ENC soundings, USACE surveys, SRTM, CSC LiDAR, NOS surveys, Jackson Co. DEM, Harrison Co. DEM, and JALBTCX LiDAR](page_256_670_1024_670.png) Figure 3. Source and coverage of datasets used to compile the Biloxi DEM. 3.1.1 Shoreline Two digital coastline datasets of the Biloxi region were analyzed for inclusion in the Biloxi DEM: OCS Electronic Navigational Charts and the Mississippi Office of Geology (MOG), Coastal Geology and Energy Division High Water shoreline (Table 2). Table 2: Shoreline datasets used in compiling the Biloxi DEM.
Source Year Data Type Spatial Resolution Original Horizontal Datum/Coordinate System Original Vertical Datum URL
OCS Electronic Navigation Charts (ENC) 2002 to 2004 extracted coastline Digitized from 1:250,000 to 1:456,394 scale charts WGS84 MHW http://www.nauticalcharts.noaa.gov/
Mississippi Office of Geology (MOG), Coastal Geology and Energy Division 1986 to 2002 MS High water shoreline ~ 5 meters WGS84 “High water shoreline” http://geology.deq.state.ms.us/coastal/Shorelines-GPS.htm
1) NOAA Office of Coast Survey electronic navigational charts Thirteen NOAA nautical charts within the Biloxi DEM region were downloaded from the NOAA OCS website (http://www.nauticalcharts.noaa.gov/). All of the nautical charts are available in raster nautical chart (RNC) format—georeferenced map imagery, which are frequently updated—with eight also available as Electronic Navigational Charts (ENCs)—digital GIS chart components (Table 3 and Fig. 4). The NOAA Coastal Services Center’s ‘Electronic Navigational Chart Data Handler for ArcView’ extension (http://www.csc.noaa.gov/products/enc/) was used to import the ENCs into ArcGIS. The ENCs include coastline data files (MHW), which were compared with the other coastline datasets, high-resolution coastal LiDAR data, topographic data, and NOS hydrographic soundings. The ENCs also include soundings (extracted from NOS hydrographic surveys) and land elevations. Two of the ENCs (#11360 and #11366) were used in conjunction with the MOG coastline dataset to build a ‘combined coastline’ (Fig. 6). Coastline files extracted from lower resolution ENCs #11360 and #11366 were used instead of the higher resolution ENC #11363 and #11371 through #11375, as the data more closely matched recent LiDAR data in areas with high rates of coastal change. Editing all of the ENC coastline data was necessary to capture detail in areas where recent bathymetric survey data existed. Nautical charts in RNC format were used to evaluate other coastline, bathymetric and topographic datasets and for digitization of coastal features not represented in any digital coastline dataset. Table 3: NOAA Electronic navigational charts in the Biloxi, Mississippi region.
Chart Number Title Edition Date Scale Available Format Used in Combined Coastline
11360 Cape St. George to Mississippi Passes 7th 2006 1:456,394 ENC yes
11363 Chandeleur and Breton Sounds 40th 2005 1:80,000 ENC
11366 Approaches to Mississippi River 7th 2007 1:250,000 ENC yes
11371 Lake Borgne and Approaches Cat Island to Point Aux Herbes 2nd 2007 1:80,000 ENC
11372 Dog Keys Pass to Waveland 21st 2006 1:40,000 ENC
11373 Mississippi Sound and Approaches Dauphin Island to Cat Island 8th 2007 1:80,000 ENC
11374 Dauphin Island Alabama to Horn Island Mississippi 12th 2006 1:40,000 ENC
11375 Pascagoula Harbor Mississippi 10th 2007 1:20,000 ENC
Figure 4. NOAA Electronic Navigational Charts available in the Biloxi region. ENCs #11360 and #11366 provide coverage for the majority of the DEM area. ![NOAA Electronic Navigational Charts available in the Biloxi region.](page_256_256_1024_768.png) 2) Mississippi Office of Geology, Mississippi High Water Shoreline The Mississippi Office of Geology (MOG), Coastal Geology and Energy Division has developed a High Water shoreline for use in coastal morphology studies and to provide a baseline dataset for monitoring yearly shoreline changes. The primary data were collected in the field using backpack GPS receivers while walking the high tide line. Orthophotos were also digitized and combined with the GPS data to form complete coastal coverage². The MOG shoreline was manually edited using ESRI ArcMap to eliminate features such as piers and docks. A comparison of the MOG shoreline with other coastline datasets available for the Mississippi mainland is illustrated in Figure 5. The NGA and NGS datasets show bridge features, which were not present in the MOG shoreline. ![Detail of coastline datasets available for Biloxi Bay.](page_312_646_1097_682.png) Figure 5. Detail of coastline datasets available for Biloxi Bay. ² GPS Data were collected in the field with backpack GPS receivers while walking the high tide line. GPS data post processed using base station data from MOG base stations in Biloxi and Jackson. Shoreline vectors were cleaned to remove hanging nodes and manually corrected to remove clusters and errant data points. Shoreline loops were also removed. Areas where survey parties met were joined by removing redundant sections or nodes. Jagged shorelines sections, a result of data errors, were simplified where possible. OrthoImagery was used to supplement the GPS data and complete the shoreline. This data is not as accurate as the GPS data. Ortho Image Data: shoreline digitized from aerial photo using ArcGIS. All data cleaned to insure topological correctness. Polylines were split in segments less than 100 m in length for attributing. Dangles and overshoots removed in process of line splitting. Shoreline is not continuous in all locations. Attribute data were conflated from previous sources and from data created by the Mississippi Office of Geology. Previous source data were used as is. Created data were visually checked using map analysis and orthoimagery. [Extracted from metadata] To obtain the best digital MHW coastline, NGDC combined the MOG High Waterline and ENC coastlines into a ‘combined coastline’ (Fig. 6). Where overlap occurred between coastline datasets, the dataset with the most detail and consistency with topographic, bathymetric and topographic–bathymetric datasets was used. This combined coastline was manually adjusted along the Gulf coast, using ESRI ArcMap to match the JALBTCX high-resolution coastal LiDAR data, particularly the late 2005 post-Hurricane Katrina survey. For areas where coastline data were unavailable or grossly inaccurate in the Katrina-impacted Chandeleur Island region (e.g., Fig 7), NGDC manually digitized a MHW coastline based on zero elevation data from both CSC topographic and JALBTCX bathymetric/topographic datasets. The combined coastline was converted to point data for use as a coastal buffer in the bathymetric pre-surfacing algorithm (see Section 3.3.2), to ensure that interpolated bathymetric values reached “zero” at the coast. It was also used to clip USGS NED topographic DEMs, which contain elevation values, typically zero, over the open ocean (Section 3.1.3). ![Digital coastline segments used to create a 'combined coastline' for the Biloxi region.](page_246_682_1097_627.png) Figure 6. Digital coastline segments used to create a 'combined coastline' for the Biloxi region. Figure 7. Changes in coastal morphology of the Chandeleur Island Chain pre- and post-Katrina (http://coastal.er.usgs.gov/hurricanes/katrina/photo-comparisons/chandeleur.html#set5). 3.1.2 Bathymetry Bathymetric datasets used in the compilation of the Biloxi DEM include 48 NOS hydrographic surveys, 25 USACE surveys of dredged shipping channels, and OCS ENC extracted soundings in the Chandeleur Sound region (Table 4). Table 4: Bathymetric datasets used in compiling the Biloxi DEM.
Source Year Data Type Spatial Resolution Original Horizontal Datum/Coordinate System Original Vertical Datum URL
USACE 2005 to 2007 Bathymetric surveys Profiles 75 to 300 m long, 5 to 150 m apart with < 1 m point spacing NAD83 State Plane Mississippi East (feet) MLLW (meters)
NOS 1917 to 1989 Hydrographic survey soundings Ranges from 10 m to 1 km (varies with scale of survey, depth, traffic, and probability of obstructions) NAD27, NAD83 geographic MLLW or MLW (meters) http://www.ngdc.noaa.gov/mgg/bathymetry/hydro.html
OCS 2006 extracted ENC soundings 200 to 2500 m point spacing WGS84 geographic MLLW (meters)
1) NOS hydrographic survey data A total of 48 NOS hydrographic surveys conducted between 1917 and 1989 were utilized in developing the Biloxi DEM (Table 5; Fig. 8). The hydrographic survey data were originally vertically referenced to Mean Lower Low Water (MLLW) or Mean Low Water (MLW) and horizontally referenced to either NAD27 or NAD83 geographic datums. All surveys were extracted from NGDC’s online NOS hydrographic database (http://www.ngdc.noaa.gov/mgg/bathymetry/hydro.html) in their original, digitized datums (Table 5). The data were then converted to WGS84 and MHW using FME software, an integrated collection of spatial extract, transform, and load tools for data transformation (http://www.safe.com). The surveys were subsequently clipped to a polygon 0.05 degree (~5%) larger than the Biloxi DEM area to support data interpolation along grid edges. After converting all NOS survey data to MHW (see Section 3.2.1), the data were displayed in ESRI ArcMap and reviewed for digitizing errors against scanned original survey smooth sheets and compared to the USACE multibeam and coastal LiDAR data, NED topographic data, the combined coastline, RNCs, and Google Earth satellite imagery. Data point spacing for the NOS surveys varied by collection date. In general, earlier surveys had greater point spacing than more recent surveys. Table 5: Digital NOS hydrographic surveys used in compiling the Biloxi DEM.
Survey ID Year Scale Original vertical datum Original horizontal datum
D00077 1988 20,000 Mean Lower Low water NAD83
D00078 1984/87 40,000 Mean Lower Low water NAD27
D00079 1988 20,000 Mean Lower Low water NAD83
F00077 1948/88 40,000 Mean Low Water NAD27
F00314 1988 20,000 Mean Lower Low water NAD83
F00315 1988 20,000 Mean Lower Low water NAD83
F00324 1989 20,000 Mean Lower Low water NAD83
F00329 1989 20,000 Mean Lower Low water NAD83
F00335 1989 20,000 Mean Lower Low water NAD83
H04000 1917 40,000 Mean Low Water undetermined
Station Year Area Mean Reference
H04021 1917 40,000 Mean Low Water undetermined
H04171 1920 80,000 Mean Low Water undetermined
H04212 1921/22 80,000 Mean Low Water undetermined
H04219 1922 80,000 Mean Low Water undetermined
H04223 1922 80,000 Mean Low Water undetermined
H06550 1940 80,000 Mean Low Water NAD27
H06552 1940 40,000 Mean Low Water NAD27
H06688 1941 40,000 Mean Low Water NAD27
H08643 1961/62 10,000 Mean Low Water NAD27
H08644 1961/64 10,000 Mean Low Water NAD27
H08645 1961/62 10,000 Mean Low Water NAD27
H08646 1961/62 10,000 Mean Low Water NAD27
H08647 1961/62 20,000 Mean Low Water NAD27
H08648 1961/62 20,000 Mean Low Water NAD27
H08649 1962 10,000 Mean Low Water NAD27
H08650 1962 10,000 Mean Low Water NAD27
H08651 1962 10,000 Mean Low Water NAD27
H08652 1962 10,000 Mean Low Water NAD27
H08922 1966/68 10,000 Mean Low Water NAD27
H08923 1966/68 10,000 Mean Low Water NAD27
H08924 1967/68 20,000 Mean Low Water NAD27
H08925 1967/68 10,000 Mean Low Water NAD27
H08970 1968 10,000 Mean Low Water NAD27
H08971 1968 20,000 Mean Low Water NAD27
H09004 1968/69 20,000 Mean Low Water NAD27
H09028 1970/71 20,000 Mean Low Water NAD27
H09103A 1970 20,000 Mean Low Water undetermined
H09103B 1970 20,000 Mean Low Water undetermined
H09118 1970/75 20,000 Mean Low Water NAD27
H09156 1970/71 10,000 Mean Low Water NAD27
H09177 1970/71 10,000 Mean Low Water NAD27
H09200 1971 20,000 Mean Low Water NAD27
H10113 1983 40,000 Mean Lower Low water NAD27
H10206 1985 40,000 Mean Lower Low water NAD27
H10208 1985 20,000 Mean Lower Low water NAD27
H10247 1987 20,000 Mean Lower Low water NAD83
H10261 1987 20,000 Mean Lower Low water NAD27
Figure 8. Digital NOS hydrographic survey coverage in the Biloxi region. DEM boundary shown in red, combined coastline shown in gray. 2) USACE surveys of dredged shipping channels Twenty five USACE bathymetric surveys of dredged shipping channels in the Mississippi Sound (Fig. 9) were provided to NGDC by Matt Tate, USACE Mobile District, Irvington Site Office. All data were originally in NAD83 Mississippi State Plane East coordinates, and MLLW vertical datum (Table 6). Surveys consist of parallel, across-channel profiles, spaced 5 to 125 meters apart, with point soundings less than 1 meter apart. Two surveys (GA121306HIGH and GA121306LOW) were edited in ArcMap to remove soundings inconsistent with neighboring soundings and nautical chart data. NGDC created soundings along the axis of the Gulf Port shipping channel to insure its representation in the DEM. ![Location of USACE survey data within dredged shipping channels in the Biloxi region.](page_347_624_1017_563.png) Figure 9. Location of USACE survey data within dredged shipping channels in the Biloxi region. Table 6: USACE bathymetric surveys used in compiling the Biloxi DEM.
Region Original horizontal datum Original vertical datum Spatial Resolution
Biloxi NAD83 State Plane Mississippi East (feet) MLLW Profiles ~100 m long, spaced 125 m apart, with <1 m point spacing
Gulfport NAD83 State Plane Mississippi East (feet) MLLW Profiles ~200 m long, spaced 150 m apart, with <1 m point spacing
Pascagoula NAD83 State Plane Mississippi East (feet) MLLW Profiles ~125 to 250 m long, spaced 25 to 125 m apart, with <1 m point spacing
Pass Christian NAD83 State Plane Mississippi East (feet) MLLW Profiles ~75 to 300 m long, spaced 5 to 25 m apart, with <1 m point spacing
3) Office of Coast Survey Electronic Nautical Chart extracted soundings Two of the available ENCs for the Biloxi DEM were used to provide bathymetric sounding coverage in the Chandeleur Sound region where NOS surveys were either non existent or provided sparse data coverage (Fig. 10). ENCs #11363 and #11371 were downloaded from the OCS website (http://www.nauticalcharts.noaa.gov/) in S-57 format and imported to a coverage using ArcCatalog. Elevations were converted from MLLW to MHW, and values greater than zero were deleted. The data were then clipped using ArcCatalog to remove points more than 2.5 minutes outside the DEM boundary. Figure 11 illustrates the unusual morphology of pitting on the seabed identified in ENC#11371. ![Soundings taken from ENCs #11363 and #11371 shown in green and blue, respectively. Biloxi DEM boundary shown in red, combined coastline shown in black. Arrow indicates Karako Bay shown in Figure 11.](page_246_682_1092_627.png) Figure 10. Soundings taken from ENCs #11363 and #11371 shown in green and blue, respectively. Biloxi DEM boundary shown in red, combined coastline shown in black. Arrow indicates Karako Bay shown in Figure 11. Figure 11. Small depressions on the sea bed of Karako Bay identified in ENC#1137. Numbers in red are elevation values transformed to MHW in meters. ![Map showing small depressions on the sea bed of Karako Bay, with numbers indicating elevation values in meters](page_246_180_1097_726.png) 3.1.3 Topography Topographic datasets in the Biloxi region were obtained from the U.S. Geological Survey, Mississippi Automated Resource Information System (MARIS), and NOAA Coastal Services Center (CSC) (Table 7; Fig.12). The U.S. Army Corps of Engineers provided NGDC with a coastal Mississippi DEM that was not processed to bare earth; it was not used in building the Biloxi DEM. Table 7: Topographic datasets used in compiling the Biloxi DEM.
Source Year Data Type Spatial Resolution Original Horizontal Datum/Coordinate System Original Vertical Datum URL
USGS/NED 1998 to 2000 DEM 1/3 arc second NAD83 NAVD88 (meters) http://seamless.usgs.gov/
USGS/SRTM 2004 DEM ~ 30 meters WGS84 assumed Mean Sea Level http://seamless.usgs.gov/
Mississippi Automated Resource Information System (MARIS) 1964 to 1996 county DEM 10 meters NAD83 NGVD29 (feet) http://www.maris.state.ms.us/Htm/DownloadData/DEM.html
CSC/Mississippi LiDAR for Harrison County 2004 coastal LiDAR 5 meters NAD83 NAVD88 (meters) http://www.csc.noaa.gov/lidar
CSC/Mississippi LiDAR post-Katrina merged flood 2005 bare earth coastal LiDAR 5 meters NAD83 NAVD88 (meters) http://www.csc.noaa.gov/lidar
CSC/Mississippi LiDAR for Jackson and Hancock Counties 2005 coastal LiDAR 5 meters NAD83 NAVD88 (meters) http://www.csc.noaa.gov/lidar
Figure 12. Source and coverage of topographic datasets used in building the Biloxi DEM. ![Source and coverage of topographic datasets used in building the Biloxi DEM.](page_184_186_1207_900.png) 1) USGS NED topography The U.S. Geological Survey (USGS) National Elevation Dataset (NED; http://ned.usgs.gov/) provided complete 1/3 arc-second coverage of the Biloxi region3. Data are in NAD83 geographic coordinates and NGVD88 vertical datum (meters), and are available for download as raster DEMs. The extracted bare-earth elevations have a vertical accuracy of +/- 7 to 15 meters depending on source data resolution. See the USGS Seamless web site for specific source information (http://seamless.usgs.gov/). The dataset was derived from USGS quadrangle maps and aerial photographs based on topographic surveys; it has been revised using data collected in 1998 and 2000. The DEMs include zero values over the ocean, which were clipped to the combined coastline. ![NED topographic data for the northeastern section of the DEM showing lineations in data. The lineated section was clipped from the final DEM.](page_420_613_708_377.png) Figure 13. NED topographic data for the northeastern section of the DEM showing lineations in data. The lineated section was clipped from the final DEM. The NED data for the northeastern section of the Biloxi DEM includes anomalous lineations that were clipped from the dataset using ArcCatalog. The NED data were used exclusively in the eastern section of the DEM located in Alabama and for the western Chandeleur Sound region as no LiDAR data were available in those regions. 3. The USGS National Elevation Dataset (NED) has been developed by merging the highest-resolution, best quality elevation data available across the United States into a seamless raster format. NED is the result of the maturation of the USGS effort to provide 1:24,000-scale Digital Elevation Model (DEM) data for the conterminous U.S. and 1:63,360-scale DEM data for Georgia. The dataset provides seamless coverage of the United States, HI, AK, and the island territories. NED has a consistent projection (Geographic), resolution (1 arc second), and elevation units (meters). The horizontal datum is NAD83, except for AK, which is NAD27. The vertical datum is NGVD88, except for AK, which is NGVD29. NED is a living dataset that is updated bimonthly to incorporate the “best available” DEM data. As more 1/3 arc second (10 m) data covers the U.S., then this will also be a seamless dataset. [Extracted from USGS NED website] 2) Mississippi Automated Resource Information System DEMs The MARIS data consist of two 10-meter resolution DEMs within Harrison and Jackson counties. These DEMs were generated from 1:24,000 USGS topographic maps and are available on the MARIS website (http://www.maris.state.ms.us/Htm/DownloadData/DEM.html). NGDC clipped the MARIS DEMs to the combined coastline and converted the resulting DEM to points, using ArcCatalog tools. Elevation values in the area of the barrier islands were anomalous; they were removed using ArcMap (Fig. 14). The remaining data were included in the final DEM where NED data were eliminated and where LiDAR data were unavailable. ![Color image of the MARIS Harrison County DEM in the north eastern part of the Biloxi region. Note the detail view of Cat Island showing an example of the poor data quality around the barrier islands.](page_328_670_1092_563.png) Figure 14. Color image of the MARIS Harrison County DEM in the north eastern part of the Biloxi region. Note the detail view of Cat Island showing an example of the poor data quality around the barrier islands. 3) CSC Coastal LiDAR NOAA’s Coastal Services Center provided coastal LiDAR datasets that were 95% processed to bare-earth for Harrison, and Jackson and Hancock counties, as well as a post-Katrina Merged Flood4 dataset that covered all three counties. Anomalous elevations below zero, located on land, were eliminated by filtering the data using FME. The post-Katrina Merged Flood dataset is processed to bare-earth; however Figures 16, 17, and 18 illustrate discrepancies between the LiDAR data and other topographic datasets that could not be rectified by NGDC. ![Spatial coverage of the CSC topographic LiDAR datasets for the Biloxi DEM.](page_256_613_1024_682.png) Figure 15. Spatial coverage of the CSC topographic LiDAR datasets for the Biloxi DEM. 4. Pre- and post-hurricane Katrina LiDAR datasets of Hancock, Harrison, and Jackson Counties, MS, were merged into a seamless coverage by URS. The pre-Katrina LiDAR data was collected by EarthData International at a 5-meter posting density during the period of February 25 to March 30, 2005. Woolpert and USACE collected the post-Katrina LiDAR data. Woolpert acquired 1-meter posting density data of Coastal Mississippi between the dates of September 19 and October 9, 2005. USACE collected 1-meter posting density LiDAR of the Mississippi barrier islands over the same time period. Each dataset was clipped at the approximate location of the debris line. Data south of the debris line was removed from the Mississippi LiDAR dataset. Data north of the debris line was removed from the post-Katrina LiDAR dataset. The post-Katrina LiDAR dataset was then imported into the seamless Mississippi LiDAR dataset creating a merged seamless coverage. [Extracted form metadata.] Figure 16. CSC LiDAR merged post-Katrina dataset showing a ~40 meter “hill” at Bayou Casotte. It is an actual feature that was retained in the Biloxi DEM.. Figure 17. A. Image of RNC #11373 at Bayou Casotte. B. Image of NED data at Bayou Casotte, showing no expression of large hill in LiDAR data. ![Chevron Refinery at Bayou Casotte. Image from USGS (http://coastal.er.usgs.gov/hurricanes/katrina/quickphotos/pascagoula/).](page_312_186_1047_495.png) Figure 18. Chevron Refinery at Bayou Casotte. Image from USGS (http://coastal.er.usgs.gov/hurricanes/katrina/quickphotos/pascagoula/). 3) NASA Shuttle Radar Topography Mission The NASA Shuttle Radar Topography Mission (SRTM) obtained elevation data on a near-global scale to generate the most complete high-resolution digital topographic database of Earth\(^5\). The SRTM consisted of a specially modified radar system that flew onboard the Space Shuttle Endeavour during an 11-day mission in February of 2000. Data from this mission have been processed into 1 degree \( \times \) 1 degree tiles that have been edited to define the coastline, and are available from the USGS Seamless web site (http://seamless.usgs.gov/) as raster DEMs. The data have not been processed to bare earth, but meet absolute horizontal and vertical accuracies of 20 and 16 meters, respectively. The SRTM data were used for a small area in the southern most section of the Chandeleur Island chain (Fig 3). No other topographic data were available for this area. 5. The SRTM data sets result from a collaborative effort by the National Aeronautics and Space Administration (NASA) and the National Geospatial-Intelligence Agency (NGA – previously known as the National Imagery and Mapping Agency, or NIMA), as well as the participation of the German and Italian space agencies, to generate a near-global digital elevation model (DEM) of the Earth using radar interferometry. The SRTM instrument consisted of the Spaceborne Imaging Radar-C (SIR-C) hardware set modified with a Space Station-derived mast and additional antennae to form an interferometer with a 60 meter long baseline. A description of the SRTM mission can be found in Farr and Kobrick (2000). Synthetic aperture radars are side-looking instruments and acquire data along continuous swaths. The SRTM swaths extended from about 30 degrees off-nadir to about 58 degrees off-nadir from an altitude of 233 km, and thus were about 225 km wide. During the data flight the instrument was operated at all times the orbiter was over land and about 1000 individual swaths were acquired over the ten days of mapping operations. Length of the acquired swaths range from a few hundred to several thousand km. Each individual data acquisition is referred to as a “data take.” SRTM was the primary (and pretty much only) payload on the STS-99 mission of the Space Shuttle Endeavour, which launched February 11, 2000 and flew for 11 days. Following several hours for instrument deployment, activation and checkout, systematic interferometric data were collected for 222.4 consecutive hours. The instrument operated almost flawlessly and imaged 99.96% of the targeted landmass at least one time, 94.59% at least twice and about 50% at least three or more times. The goal was to image each terrain segment at least twice from different angles (on ascending, or north-going, and descending orbit passes) to fill in areas shadowed from the radar beam by terrain. This ‘targeted landmass’ consisted of all land between 56 degrees south and 60 degrees north latitude, which comprises almost exactly 80% of Earth’s total landmass. [Extracted from SRTM online documentation] 3.1.4 Topography–Bathymetry Combined topographic–bathymetric surveys of coastal Mississippi were performed in 2004 and 2005—post-Hurricanes Dennis and Katrina—by the Joint Airborne LiDAR Bathymetry Technical Center of Expertise (JALBTCX) (Table 8; Fig. 19). The data were collected using the CHARTS (Compact Hydrographic Airborne Rapid Total Survey) system to depict elevations above and below water along the immediate coastal zone6. The surveys generally extend from 200 to 2500 meters inland and up to 150 meters over the water. Data points are spaced approximately every 5 meters, and have an accuracy better than 3.0 meters horizontally and 0.3 meters vertically. The dataset covers much of the barrier island chain with the exception of the islands to the west of Chandeleur Sound; it covers the mainland excluding Harrison County. Table 8. Combined topographic–bathymetric datasets used in compiling the Biloxi DEM.
Source Year Data Type Spatial Resolution Original Horizontal Datum/Coordinate System Original Vertical Datum
JALBTCX USACE 2004 Topo/Bathy project 2004 LiDAR 5 meters NAD83 geographic NAVD88 (meters)
JALBTCX USACE 2005 post-Katrina Topo/Bathy project 2005 LiDAR 5 meters NAD83 geographic NAVD88 (meters)
![Spatial coverage of topographic-bathymetric datasets utilized in Biloxi DEM development.](page_370_670_1047_627.png) Figure 19. Spatial coverage of topographic- bathymetric datasets utilized in Biloxi DEM development. 6. These data were collected using a SHOALS-1000T system. It is owned and operated by Fugro Pelagos performing contract survey services for the US Army Corps of Engineers. The system collects topographic lidar data at 10 kHz and hydrographic data at 1 kHz. The system also collects RGB imagery at 1Hz. Aircraft position, velocity and acceleration information are collected through a combination of Novatel and POS A/V equipment. Raw data are collected and transferred to the office for downloading and processing in SHOALS GCS software. GPS data are processed using POSPac software and the results are combined with the lidar data to produce 3-D positions for each lidar shot. These data are edited using Fledermaus software to remove anomalous data from the dataset. The edited data are unloaded from SHOALS GCS, converted from ellipsoid to orthometric heights, based on the GEOID03 model, and split into geographic tiles covering approximately 5km each. [Extracted from metadata] 1) Post-Katrina 2005 JALBTCX LiDAR survey This dataset consists of a bathymetric–topographic LiDAR survey covering 70 kilometers of the coastal region from the eastern DEM boundary at San Souci Beach, Alabama to Deer Island at Biloxi, Mississippi; the Gulf Islands National Seashore’s barrier islands; and the central section of the Chandeleur Island chain. Post-Hurricane Katrina elevations were collected above and below water along the immediate coastal zone. The survey has a spatial resolution of 5 meters and covers the shoreline with an approximate width of 2,000 meters. Very little bathymetric information exists in the data, and the shoreline can not be easily extracted from this dataset due to the near shore noise. 2) 2004 JALBTCX LiDAR survey This dataset consists of a bathymetric–topographic coastal LiDAR survey covering Ship Island, Horn Island, Petit Bois Island, Dauphin Island, and Deer Island. The survey has a spatial resolution of 5 meters and consists primarily of topographic data. NGDC used this dataset for the areas not covered by the post-Hurricane Katrina dataset. 3.2 Establishing Common Datums 3.2.1 Vertical datum transformations Datasets used in the compilation and evaluation of the Biloxi DEM were originally referenced to a number of vertical datums including Mean Lower Low Water (MLLW), Mean Low Water (MLW), Mean Sea Level, National Geodetic Vertical Datum of 1929 (NGVD29), and North American Vertical Datum of 1988 (NAVD88). All datasets were transformed to MHW to provide the worst-case scenario for inundation modeling. Units were converted from feet to meters. 1) Bathymetric data The NOS hydrographic surveys, the extracted ENC soundings, and the USACE surveys were transformed from MLLW or MLW to MHW, using FME software, by adding a constant offset determined by averaging two Biloxi NOAA tidal stations (Table 9; Fig. 26). 2) Topographic data The USGS NED 1/3 arc-second DEM and the CSC LiDAR data were originally referenced to NAVD88. The SRTM data were assumed to be referenced to MSL. The DEMs provided by MARIS were referenced to NGVD29. Conversion to MHW, using FME software, was accomplished by adding tide-station derived constant offsets (Table 9). 3) Topographic–bathymetric data Combined topographic–bathymetric coastal LiDAR survey data were transformed from NAVD88 to MHW using FME software (Table 9).
Vertical datum Difference to MHW
NAVD88 -0.380
NGVD29 -0.4175
MSL -0.230
MLW -0.470
MLLW -0.502
* Datum relationships determined by averaging values from tide stations #8743735, Biloxi Bay and #8775557, Gulfport. 3.2.2 Horizontal datum transformations Datasets used to compile the Biloxi DEM were originally referenced to State Plane Mississippi North, NAD27, NAD83 geographic, or WGS84 geographic horizontal datums. The relationships and transformational equations between these horizontal datums are well established. All data were converted to a horizontal datum of WGS84 using FME software. 3.3 Digital Elevation Model Development 3.3.1 Verifying consistency between datasets After horizontal and vertical transformations were applied, the resulting ESRI shape files were checked in ESRI ArcMap for inter-dataset consistency. Problems and errors were identified and resolved before proceeding with subsequent gridding steps. The evaluated and edited ESRI shape files were then converted to xyz files in preparation for gridding. Problems included: • Presence of man-made structures and river banks in most coastline datasets, which had to be removed. • Inconsistencies between various coastline datasets and bathymetric, topographic and bathymetric–topographic datasets. These inconsistencies are partly the result of differing resolution between datasets and of morphologic change in the highly dynamic coastal zone such as the barrier islands area. • Data values over the open ocean and rivers in the NED DEMs and LiDAR data. Each dataset required automated clipping to the combined coastline. • Digital, measured bathymetric values from NOS surveys date back over 70 years. More recent data, such as USACE surveys in dredged shipping channels, differed from older, pre-dredging NOS data by as much as 10 meters. The older NOS survey data were excised where more recent bathymetric data exists. 3.3.2 Smoothing of bathymetric data The NOS hydrographic surveys are generally sparse at the resolution of the 1/3 arc-second Biloxi DEM; in deep water, the NOS survey data have point spacings up to 2 km apart. In order to reduce the effect of artifacts in the form of lines of “pimples” in the DEM due to this low resolution dataset, and to provide effective interpolation into the coastal zone, a 1 arc-second-spacing ‘pre-surface’ or grid was generated using GMT, an NSF-funded share-ware software application designed to manipulate data for mapping purposes (http://gmt.soest.hawaii.edu/). The NOS hydrographic point data, in xyz format, were combined with the USACE soundings and JALBTCX bathymetric–topographic survey data into a single file, along with points extracted from the combined coastline—to provide a “zero” buffer along the entire coastline. These point data were then median-averaged using the GMT tool ‘blockmedian’ to create a 1 arc-second grid, 0.05 degrees (~5%) larger than the Biloxi DEM gridding region. The GMT tool ‘surface’ then applied a tight spline tension to interpolate cells without data values. The GMT grid created by ‘surface’ was converted into an ESRI Arc ASCII grid file, and clipped to the combined coastline (to eliminate data interpolation into land areas). The resulting surface was compared with the original soundings to ensure grid accuracy, converted to a shape file, and then exported as a xyz file for use in the final gridding process. 3.3.3 Gridding the data with MB-System MB-System (http://www.ldeo.columbia.edu/res/pi/MB-System/) was used to create the 1/3 arc-second Biloxi DEM. MB-System is an NSF-funded share-ware software application specifically designed to manipulate submarine multibeam sonar data, though it can utilize a wide variety of data types, including generic xyz data. The MB-System tool ‘mbgrid’ applied a tight spline tension to the xyz data, and interpolated values for cells without data. The data hierarchy used in the ‘mbgrid’ gridding algorithm, as relative gridding weights, is listed in Table 10. Greatest weight was given to the high-resolution NOS multibeam and coastal LiDAR survey data. Least weight was given to the pre-surfaced 1 arc-second NOS bathymetric grid. Gridding was performed in quadrants, each with a 5% data overlap buffer. The resulting Arc ASCII grids were seamlessly merged in ArcCatalog to create the final 1/3 arc-second Biloxi DEM. Table 10. Data hierarchy used to assign gridding weight in MB-System.
Dataset Relative Gridding Weight
JALBTCX coastal lidar bathymetry–topography: post-Katrina 1
JALBTCX coastal lidar topography: merged flood 1000
Maris DEMs 1000
SRTM 1000
ENC soundings 100
USGS NED topographic DEM 10000
NOS hydrographic surveys: bathymetric soundings 100
Pre-surfaced bathymetric grid 10
3.4 Quality Assessment of the DEM 3.4.1. Horizontal accuracy The horizontal accuracy of topographic and bathymetric features in the Biloxi DEM is dependent upon the datasets used to determine corresponding DEM cell values. Topographic features have an estimated accuracy of 10 to 15 meters; JALBTCX coastal LiDAR data have an accuracy of between 1 and 3 meters, NED topography is accurate to within about 15 meters. Bathymetric features are resolved only to within a few hundred meters in deep-water areas (i.e., the southeast corner of the DEM). Shallow, near-coastal regions, rivers, and dredged shipping channels have an accuracy approaching that of subaerial topographic features. Positional accuracy is limited by the sparseness of deep-water soundings, potentially large positional uncertainty of pre-satellite navigated (e.g., GPS) NOS hydrographic surveys, and by the rapid morphologic change that occurs in this dynamic region. 3.4.2 Vertical accuracy Vertical accuracy of elevation values for the Biloxi DEM is also highly dependent upon the source datasets contributing to DEM cell values. Topographic areas have an estimated vertical accuracy between 0.15 for JALBTCX coastal LiDAR data and up to 7 meters for NED topography. Bathymetric areas have an estimated accuracy of between 0.1 meters and 5% of water depth (~1-2 meters in the southeast corner of the DEM). These values were derived from the wide range of input data sounding measurements from the early 20th century to recent, GPS-navigated sonar surveys. Gridding interpolation to determine values between sparse, poorly-located NOS soundings degrades the vertical accuracy of elevations in deep water. 3.4.3 Slope maps and 3-D perspectives ESRI ArcCatalog was used to generate a slope map from the Biloxi DEM to allow for visual inspection and identification of artificial slopes along boundaries between datasets (e.g., Fig. 20). The DEM was transformed to UTM Zone 16 coordinates (horizontal units in meters) in ArcCatalog for derivation of the slope grid; equivalent horizontal and vertical units are required for effective slope analysis. Three-dimensional viewing of the UTM-transformed DEM was accomplished using ESRI ArcScene. Analysis of preliminary grids revealed suspect data points, which were corrected before recompiling the DEM. Figure 1 shows a color image of the final version of the 1/3 arc-second Biloxi DEM. Figure 20. Slope map of the Biloxi DEM. Flat-lying slopes are white. Dark shading denotes steep slopes; combined coastline in red. ![Slope map of the Biloxi DEM. Flat-lying slopes are white. Dark shading denotes steep slopes; combined coastline in red.](page_184_186_1207_900.png) 3.4.4 Comparison with source data files To ensure grid accuracy, the Biloxi DEM was compared to select source data files. Files were chosen on the basis of their contribution to the grid-cell values in their coverage areas (i.e., had the greatest weight and did not significantly overlap other data files with comparable weight). A histogram of the difference between a post-Hurricane Katrina JALBTCX coastal bathymetric–topographic LiDAR survey file and the Biloxi DEM is shown in Figure 21. A histogram of the difference between a NOS hydrographic survey file and the Biloxi DEM is shown in Figure 22. ![Histogram of the difference between one post-Katrina JALBTCX coastal bathymetric–topographic LiDAR survey (438,007 points) and the Biloxi DEM.](page_156_370_1207_393.png) Figure 21. Histogram of the difference between one post-Katrina JALBTCX coastal bathymetric–topographic LiDAR survey (438,007 points) and the Biloxi DEM. ![Histogram of the difference between NOS hydrographic survey H010206 and the Biloxi DEM.](page_156_820_1207_393.png) Figure 22. Histogram of the difference between NOS hydrographic survey H010206 and the Biloxi DEM. 3.4.5 Comparison with NGS geodetic monuments The elevations of 63 NOAA NGS geodetic monuments were extracted from online shape files of monument datasheets (http://www.ngs.noaa.gov/cgi-bin/datasheet.prl), which give monument positions in NAD83 (sub-mm accuracy) and elevations in NAVD88 (in meters). Elevations were shifted to MHW vertical datum (see Table 9) for comparison with the Biloxi DEM (see Fig. 24 for monument locations). Differences between the Biloxi DEM and the NGS geodetic monument elevations range from -12.3 to 27.9 meters, with a negative value indicating that the monument elevation is less than the DEM (Fig. 23). Examination of the monuments with the largest positive offsets from the DEM revealed that they lie within the East River Island region, alongside a highway, or atop a small hill that is poorly resolved within the NED topographic DEM.
Count 63 Skewness 3.0589
Min -12.273 Kurtosis 20.841
Max 27.9 1-st Quartile -2.2565
Mean -1.0513 Median 0.506
Std. Dev. 4.9471 3-rd Quartile 8.039
Figure 23. Histogram of the differences between NGS geodetic monument elevations and the Biloxi DEM. ![Histogram of the differences between NGS geodetic monument elevations and the Biloxi DEM.](page_184_370_1207_312.png) Figure 24. Location of NGS monuments and NOAA tide stations in the Biloxi region. Tide stations used to convert between vertical datums; NGS monument elevations used to evaluate the DEM. ![Location of NGS monuments and NOAA tide stations in the Biloxi region.](page_184_728_1207_496.png) 4. SUMMARY AND CONCLUSIONS A topographic–bathymetric digital elevation model of the Biloxi, Mississippi region, with cell spacing of 1/3 arc-second, was developed for the Pacific Marine Environmental Laboratory (PMEL) NOAA Center for Tsunami Research. The best available digital data from U.S. federal and state agencies were obtained by NGDC, shifted to common horizontal and vertical datums, and evaluated and edited before DEM generation. The data were quality checked, processed and gridded using ESRI ArcGIS, FME, GMT, and MB-System software. Recommendations to improve the Biloxi DEM, based on NGDC’s research and analysis, are listed below: • Process coastal LiDAR data to bare earth. • Obtain digital versions of several NOAA nautical charts that have not yet been digitized. • Resurvey coastal areas impacted by Hurricane Katrina. 5. ACKNOWLEDGMENTS The creation of the Biloxi DEM was funded by the NOAA, Pacific Marine Environmental Laboratory. The authors thank Chris Chamberlin and Vasily Titov (PMEL), Jeff Lillycrop (USACE), Matt Tate (USACE Irvington Site Office), and Cheryl Bosley (USACE Mobile District Office). 6. REFERENCES Nautical Chart #11360, 7th Edition, 2006. Cape St. George to Mississippi Passes. Scale 1:456,394. U.S. Department of Commerce, NOAA, National Ocean Service, Coast Survey. Nautical Chart #11363, 40th Edition, 2005. Chandeleur and Breton Sounds. Scale 1:80,000. U.S. Department of Commerce, NOAA, National Ocean Service, Coast Survey. Nautical Chart #11366, 7th Edition, 2007. Approaches to Mississippi River. Scale 1:250,000. U.S. Department of Commerce, NOAA, National Ocean Service, Coast Survey. Nautical Chart #11371, 2nd Edition, 2006. Lake Borgne and Approaches Cat Island to Point Aux Herbes. Scale 1:80,000. U.S. Department of Commerce, NOAA, National Ocean Service, Coast Survey. Nautical Chart #11372, 21st Edition, 2006. Dog Keys Pass to Waveland. Scale 1:40,000. U.S. Department of Commerce, NOAA, National Ocean Service, Coast Survey. Nautical Chart #11373, 8th Edition, 2007. Mississippi Sound and Approaches Dauphin Island to Cat Island. Scale 1:80,000. U.S. Department of Commerce, NOAA, National Ocean Service, Coast Survey. Nautical Chart #11374, 12th Edition, 2006. Dauphin Island Ala. To Horn Island Miss.. Scale 1:40,000. U.S. Department of Commerce, NOAA, National Ocean Service, Coast Survey. Nautical Chart #11375, 10th Edition, 2007. Pascagoula Harbor Mississippi. Scale 1:20,000. U.S. Department of Commerce, NOAA, National Ocean Service, Coast Survey. 7. DATA PROCESSING SOFTWARE ArcGIS v. 9.2, developed and licensed by ESRI, Redlands, California, http://www.esri.com/ Electronic Navigational Chart Data Handler for ArcView, developed by NOAA Coastal Services Center, http://www.csc.noaa.gov/products/enc/ FME 2006 GB – Feature Manipulation Engine, developed and licensed by Safe Software, Vancouver, BC, Canada, http://www.safe.com/ GEODAS v. 5 – Geophysical Data System, shareware developed and maintained by Dan Metzger, NOAA National Geophysical Data Center, http://www.ngdc.noaa.gov/mgg/geodas/ GMT v. 4.1.4 – Generic Mapping Tools, shareware developed and maintained by Paul Wessel and Walter Smith, funded by the National Science Foundation, http://gmt.soest.hawaii.edu/ MB-System v. 5.1.0, shareware developed and maintained by David W. Caress and Dale N. Chayes, funded by the National Science Foundation, http://www.ldeo.columbia.edu/res/pi/MB-System/