St. Catherines/Sapelo Sounds, GA (S140) Bathymetric Digital Elevation Model (30 meter resolution) Derived From Source Hydrographic Survey Soundings Collected by NOAA
Bathymetry for St. Catherines/Sapelo Sounds was derived from eighteen surveys containing
70,555 soundings. No surveys were omitted. The average separation between soundings
was 52 meters. Fifteen of the eighteen surveys used dated from 1934. The remaining
three surveys located in the east and south dated from 1974 and 1977. The total range
of sounding data was 1.5 meters to -20.1 meters at mean low water. Mean high water
values between 2.0 and 2.4 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. Catherines/Sapelo Sounds have 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.
Cite this dataset when used as a source.
- ID not available.
gov.noaa.ngdc.mgg.dem:stcatherines_sapelo_sounds_s140_30m
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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 | 1934-01-01 to 1977-01-01 |
Spatial Reference System | urn:ogc:def:crs:EPSG::586626917 |
Spatial Bounding Box Coordinates |
West:-81.419179
East:-81.131249
South:31.346798
North:31.836511
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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: 2018-06-13
For questions about the information on this page, please email:dem.info@noaa.gov