St. Andrew/St. Simons Sounds, GA (S160) Bathymetric DigitalElevation Model (30 meter resolution) Derived From SourceHydrographic Survey Soundings Collected by NOAA

Bathymetry for St. Andrew/St. Simons Sounds was derived from fifteen surveyscontaining 87,618 soundings. Two older, overlapping, less accurate surveys wereomitted before tinning the data. The average separation between soundingswas 44 meters. Fourteen of the surveys used dated from 1934 to 1937. Theremaining survey, located in the northeast, dated from 1954. The totalrange of sounding data was 1.5 meters to -22.9 meters at mean low water.Mean high water values between 2.0 and 2.4 meters were assigned to theshoreline. Fifteen points were found that were not consistent with thesurrounding data. These were removed prior to tinning. DEM grid valuesoutside the shoreline (on land) were assigned null values (-32676).St. Andrew/St. Simons Sounds have ten 7.5 minute DEMs and two onedegree DEMs. The 1 degree DEMs were generated from the higherresolution 7.5 minute DEMs which covered the estuary. A DigitalElevation Model (DEM) contains a series of elevations ordered fromsouth to north with the order of the columns from west to east. TheDEM is formatted as one ASCII header record (A- record), followed bya series of profile records (B- records) each of which include ashort B-record header followed by a series of ASCII integerelevations (typically in units of 1 centimeter) per each profile.The last physical 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.