Aransas Bay, TX (G300) Bathymetric Digital Elevation Model (30meter resolution) Derived From Source Hydrographic Survey SoundingsCollected by NOAA

Bathymetry for Aransas Bay was derived from fourteen surveys containing123,235 soundings. The average separation between soundings was 65meters. Two entire overlapping, older, less accurate surveys were deletedbefore tinning. The overlap from two older, less accurate surveys was alsodeleted before tinning. The surveys used dated from 1935 to 1991. Surveysfrom 1989 to 1991 cover the majority of the bay. The range of soundingsfor the surveys used was 2.0 to -16.1 meters. A mean high water value of0.3 meters was assigned to the shoreline. Ten points were found that were notconsistent with the surrounding points. These were removed prior to tinning.DEM grid values outside the shoreline (on land) were assigned null values(-32676).Aransas Bay has twelve 7.5 minute DEMs and four one degree DEMs. The1 degree DEMs were generated from the higher resolution 7.5 minuteDEMs which covered the estuary. A Digital Elevation Model (DEM)contains a series of elevations ordered from south to north with theorder of the columns from west to east. The DEM is formatted as oneASCII header record (A- record), followed by a series of profilerecords (B- records) each of which include a short B-record headerfollowed by a series of ASCII integer elevations (typically in unitsof 1 centimeter) per each profile. The last physical record of theDEM 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.