Long Island Sound, NY/CT (M040) Bathymetric Digital ElevationModel (30 meter resolution) Derived From Source Hydrographic SurveySoundings Collected by NOAA
Vydavatel National Oceanic and Atmospheric Administration, Department of Commerce
Datum vydání před téměř 10 roky
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Bathymetry for Long Island Sound was derived from fifty-five surveys containing562,596 soundings. Twenty-four older, less accurate, overlapping surveys wereentirely omitted, and the overlap from eight older, less accurate surveys wasomitted before tinning the data. The average separation between soundingswas 77 meters. The fifty-five surveys used dated from 1931 to 1990.Approximately 40 percent of the surveys were from 1931 to 1939. The total rangeof sounding data was 2.1 meters to - 113.4 meters at mean low water. Meanhigh water values between 0.6 and 2.3 meters were assigned to the shoreline.Eighty-eight points were found that were not consistent with the surrounding data. These wereremoved prior to tinning. DEM grid values outside theshoreline (on land) were assigned null values (-32676).Long Island Sound has fifty-one 7.5 minute DEMs and five 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.