St. Helena Sound, SC (S100) Bathymetric Digital Elevation Model (30 meter resolution)
Derived From Source Hydrographic Survey Soundings Collected by NOAA |
Bathymetry for St. Helena Sound was derived from nineteen surveys containing 83,246
soundings. No surveys were omitted. The average separation between soundings was 49
meters. Sixteen of the nineteen surveys used dated from 1934. The remaining surveys,
located in the southwest, dated from 1956 and 1973. The total range of sounding data
was 3.7 meters to -23.5 meters at mean low water. Mean high water values between 1.5
and 2.1 meters were assigned to the shoreline. Six 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). St. Helena
Sound has eleven 7.5 minute DEMs and a single one degree DEM. The 1 degree DEMs were
generated from the higher resolution 7.5 minute DEMs which covered the estuary. A
Digital Elevation Model (DEM) contains a series of elevations ordered from south to
north with the order of the columns from west to east. The DEM is formatted as one
ASCII header record (A- record), followed by a series of profile records (B- records)
each of which include a short B-record header followed by a series of ASCII integer
elevations (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 the Universal Transverse Mercator (UTM) projection. It provides
coverage in 7.5- by 7.5-minute blocks. Each product provides the same coverage as
a standard USGS 7.5-minute quadrangle but the DEM contains over edge data. Coverage
is available for many estuaries of the contiguous United States but is not complete. |
|