Mobile Bay, AL (G150) Bathymetric Digital Elevation Model (30 meter resolution) Derived
From Source Hydrographic Survey Soundings Collected by NOAA |
Bathymetry for Mobile Bay was derived from twenty-three surveys containing 173,661
soundings. Older, overlapping, less accurate surveys were deleted. The average separation
between surveys was 79 meters. The surveys used dated from 1960 to 1962. The range
of soundings for the surveys was 0.6 meters to -32.9 meters at mean low water. Mean
high water values between 0.3 and 0.5 meters were assigned to the shoreline. Nine
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). Mobile Bay has eighteen 7.5 minute DEMs and two one degree DEMs.
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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