Choctawhatchee Bay, FL (G120) Bathymetric Digital ElevationModel (30 meter resolution) Derived From Source Hydrographic SurveySoundings Collected by NOAA

Bathymetry for Choctawhatchee Bay was derived from ten surveys containing112,398 soundings. Two older, less accurate, overlapping surveys wereomitted prior to tinning. The average separation between soundings was 55meters. The ten surveys used dated from 1935 to 1992. Surveys from 1935 to1941 covered the eastern half of the bay, and surveys from 1986 to 1992 coveredthe western half of the bay. The range of soundings for the ten surveys used was0.3 meters to -16.4 meters at mean low water. Mean high water values between0.2 and 0.4 meters were assigned to the shoreline. Eight points were found thatwere not consistent with the surrounding points. These were removed prior totinning. DEM grid values outside the shoreline (on land) were assigned nullvalues (-32676).Choctawhatchee Bay has eight 7.5 minute DEMs and a single one degreeDEM. The 1 degree DEMs were generated from the higher resolution 7.5minute DEMs which covered the estuary. A Digital Elevation Model(DEM) contains a series of elevations ordered from south to northwith the order of the columns from west to east. The DEM isformatted as one ASCII header record (A- record), followed by aseries of profile records (B- records) each of which include a shortB-record header followed by a series of ASCII integer elevations(typically in units of 1 centimeter) per each profile. The lastphysical record of the DEM is an accuracy record (C-record).The 7.5-minute DEM (30- by 30-m data spacing) is cast on theUniversal Transverse Mercator (UTM) projection. It provides coveragein 7.5- by 7.5-minute blocks. Each product provides the samecoverage as a standard USGS 7.5-minute quadrangle but the DEMcontains over edge data. Coverage is available for many estuaries ofthe contiguous United States but is not complete.