| Mississippi Sound, MS/LA/AL (G170) Bathymetric Digital Elevation Model (30 meter resolution)
Derived From Source Hydrographic Survey Soundings Collected by NOAA |
| Bathymetry for Mississippi Sound was derived from thirty-three surveys containing
371,210 soundings. Five overlapping, older, less accurate surveys were omitted before
tinning. The average distance between soundings was 89 meters. The thirty-three surveys
used dated from 1960 to 1979. The range of soundings for the surveys used was 0.8
meters to -17.6 meters at mean low water. A mean high water value of 0.5 meters was
assigned to the shoreline. Twenty-five points were found that were not consistent
with the surrounding points. These were removed prior to tinning. DEM grid values
outside the shoreline (on land) were assigned null values (-32676). Mississippi Sound
has forty-four 7.5 minute DEMs and three 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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