Great South Bay, NY (M050) Bathymetric Digital Elevation Model(30 meter resolution) Derived From Source Hydrographic SurveySoundings Collected by NOAA
Vydavatel National Oceanic and Atmospheric Administration, Department of Commerce
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Bathymetry for Great South Bay was derived from thirteen surveys containing124,314 soundings. Nineteen older, less accurate, overlapping surveys wereomitted, and the overlap from three older, less accurate surveys wasomitted before tinning the data. The average separation between soundingswas 53 meters. Three surveys in the east and two in the southwest datedfrom 1933 or 1934. The remaining eight surveys dated from 1949 to 1951. Thetotal range of sounding data was 0.9 to - 22.6 meters at mean low water. Mean highwater values between 0.2 and 1.2 meters were assigned to the shoreline. Six points werefound that were not consistent with the surrounding data. These were removed prior to tinning. DEM gridvalues outside the shoreline (on land) were assigned null values (-32676).Great South Bay has sixteen 7.5 minute DEMs and two one degreeDEMs. 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.