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.
Cite this dataset when used as a source.
- ID not available.
gov.noaa.ngdc.mgg.dem:mississippi_sound_g170_30m
Search Data |
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Download Data |
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Distribution Formats |
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Distributor | DEM Information NOAA National Centers for Environmental Information dem.info@noaa.gov |
Dataset Point of Contact | DEM Information NOAA National Centers for Environmental Information dem.info@noaa.gov |
Time Period | 1960-01-01 to 1979-01-01 |
Spatial Reference System | urn:ogc:def:crs:EPSG::586626916 |
Spatial Bounding Box Coordinates |
West:-89.875066
East:-88.083033
South:29.858431
North:30.498833
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Spatial Coverage Map |
General Documentation |
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Associated Resources |
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Publication Dates |
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Edition | First |
Data Presentation Form | mapDigital |
Dataset Progress Status | Complete - production of the data has been completed |
Data Update Frequency | Irregular |
Supplemental Information |
The datum for these bathymetric DEMs is not the same as that used by the United States
Geological Survey (USGS) for land based DEMs which results in a discontinuity if the
two datasets are merged together. Moreover, the shoreline for the USGS DEMs is indeterminate
and not the same as that used for the Bathymetric DEMs. Because of these differences,
extreme care should be used in merging NOAA and USGS DEM data. 7.5-minute DEMs have
rows and columns which vary in length and are staggered. The UTM bounding coordinates
form a quadrilateral (no two sides are parallel to each other), rather than a rectangle.
The user will need to pad out the uneven rows and columns with blanks or flagged data
values, if a rectangle is required for the user's application. Some software vendors
have incorporated this function into their software for input of standard formatted
USGS DEMs. The data within the bathymetry file is floating point. When using the data
within a GIS care must be taken to ensure that the data are being read as floating
point and not integer data.
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Purpose | Bathymetric DEM's can be used as layers in Geographic Information Systems (GIS) for earth science analysis. DEM's can also serve as tools for volumetric analysis, for site location of structures, or for drainage basin delineation. The source soundings are collected by the NOS Office of Coast Survey (OCS). |
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Originators |
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Publishers |
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Theme keywords | Global Change Master Directory (GCMD) Science Keywords
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Place keywords | None
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Data Resolution keywords | Global Change Master Directory (GCMD) Horizontal Data Resolution Keywords
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Use Constraints | No constraint information available |
Access Constraints |
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Fees | Fee information not available. |
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Last Modified: 2018-06-08
For questions about the information on this page, please email:dem.info@noaa.gov