St. Johns River, FL (S180) 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 the St. Johns River was derived from thirty-two surveyscontaining 158,931 soundings. No surveys were omitted. The averageseparation between soundings was 66 meters. Twenty-nine of the thirty-threesurveys dated from 1935 to 1939. The remaining surveys, located in the north,dated from 1958 or 1959. The total range of sounding data was 0.6 meters to - 24.7 meters atmean low water. Mean high water values between 0.0 and 1.4 meters were assigned to the shoreline. Seven points were found that were not consistent with the surrounding data.These were removed prior to tinning. DEM grid values outside the shoreline (on land) were assigned null values (-32676).The St. Johns River has twenty-nine 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.