Data Downloads The bathymetry grid (DEM) is presented in GeoTiff format and can be opened directly in Esri ArcGIS 10.0 or higher. The map documents and shapefiles provided in this report were created in Esri ArcGIS 10.0.5 and can be found in the GIS Project folder. To open this folder in Esri ArcGIS, right-click and choose "Save As". The folder contains the .mxd file and all associated vector and raster data. The data layers provided may also be viewed using the free GIS viewer ArcGIS Explorer (http://www.esri.com/software/arcgis/explorer). All data files presented in this report use the projected coordinate system North American Datum of 1983 (NAD83), Universal Transverse Mercator (UTM) Zone 16 North (16N), and all elevations are North American Vertical Datum of 1988 (NAVD88) orthometric heights, derived from the GEOID09 geoid model unless otherwise indicated. Do not use these data for navigational purposes. Preview File Description File Format Download File Metadata Esri ArcGIS project Esri files Chan12-GIS.zip (50 MB) Included with download Bathymetry DEM 50-m cell size GeoTIFF 32-bit floating point Chan12_DEM.zip (0.154 MB) Included with download Backscatter Mosaic 1-m resolution GeoTIFF 32-bit floating point 12BIM03_IFS_Mosaic.zip (51 MB) Included with download Swath samples 5-m BASE resolution ASCII Chan12_IFB_xyz.zip (14 MB) Included with download Swath tracklines Esri shapefile 12BIM03_IFB_tracklines.zip (1.60 MB) Included with download Singlebeam soundings ASCII Chan12_SBB_xyz.zip (51 MB) Included with download Singlebeam tracklines Esri shapefile 12BIM04_SBB_tracklines.zip (1.89 MB) Included with download

A Note on Coordinate Systems

WGS84 and NAD83 have been revised several times resulting in coordinate shifts of as much as several meters in x, y, and z. The revision is indicated by the designator following the name (G1150 following WGS84, for example). Care should be taken using software that does not distinguish between the different datum versions; lack of designator is a warning sign that software does not support three-dimensional (3D) datum shifts properly. Users should pay particular attention to the accompanying metadata files to ensure that the data are properly georeferenced. In particular, note that most current GIS software (including ArcGIS 9.3) cannot properly transform high-resolution elevation data from one 3D datum to another (such as WGS84 G1150 to NAD83 CORS96) without introducing errors on the order of 1 m to 2 m in x,y, and z.

The data in this report are provided with a UTM zone 16 horizontal datum of WGS84 G1150 (equivalent to ITRF2000) and converted to NAD83 with vertical datum of NAVD88.  The vertical component was transformed using NOAA's VDatum tool (http://vdatum.noaa.gov/), by applying GEOID09 to obtain orthometric elevation.

 

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