Altamaha River, GA (S150) Bathymetric Digital Elevation Model (30 meter resolution)
Derived From Source Hydrographic Survey Soundings Collected by NOAA |
Bathymetry for the Altamaha River was derived from three surveys containing 16,511
soundings. One less accurate, overlapping survey was deleted before tinning the data.
The average separation between soundings was 49 meters. The three surveys used all
dated from 1934. The total range of sounding data was 1.2 meters to -11.9 meters at
mean low water. A mean high water value of 2.1 meters was assigned to the shoreline.
One point was found that was not consistent with the surrounding data and was removed
prior to tinning. DEM grid values outside the shoreline (on land) were assigned null
values (-32676). The Altamaha River has five 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. |
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