Open-File Report 2011–1226
Bathymetry and Acoustic Backscatter—Elwha River Delta, Washington
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 versions of these datum; lack of the 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. For this reason, data are provided in both WGS84 G1150 (equivalent to ITRF2000) and NAD83 CORS96 (equivalent to NSRS2007).
If you have trouble reading these tables, please contact the WCMG team.
The bathymetry dataset is provided in ESRI ASCII GRID format (see appendix) in WGS84 (G1150) and NAD83 (CORS96)/NAVD88, both projected in UTM Zone 10 North.
The standard deviation of the raw bathymetry grid is provided in ESRI ASCII GRID format (see appendix) in WGS84 (G1150), UTM Zone 10 North. This represents the standard deviation for all of the soundings used to compute the elevation of the grid cell.
The amplitude dataset is provided in ESRI ASCII GRID format (see appendix) in WGS84 (G1150), UTM Zone 10 North.
Data are provided in WGS84 G1150 and NAD83 CORS96. Please note the coordinate system for the files you download.
For more information, contact the PCMSC team.