Aransas Bay, TX (G300) Bathymetric Digital Elevation Model (30 meter resolution) Derived From Source Hydrographic Survey Soundings Collected by NOAA
Bathymetry for Aransas Bay was derived from fourteen surveys containing 123,235 soundings.
The average separation between soundings was 65 meters. Two entire overlapping, older,
less accurate surveys were deleted before tinning. The overlap from two older, less
accurate surveys was also deleted before tinning. The surveys used dated from 1935
to 1991. Surveys from 1989 to 1991 cover the majority of the bay. The range of soundings
for the surveys used was 2.0 to -16.1 meters. A mean high water value of 0.3 meters
was assigned to the shoreline. Ten 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). Aransas Bay has twelve
7.5 minute DEMs and four 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:aransas_bay_g300_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 1991-01-01 |
Spatial Reference System | urn:ogc:def:crs:EPSG::586626914 |
Spatial Bounding Box Coordinates |
West:-97.253154
East:-96.872037
South:27.841586
North:28.274228
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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: 2018-06-11
For questions about the information on this page, please email:dem.info@noaa.gov