St. Johns River, FL (S180) Bathymetric Digital Elevation Model (30 meter resolution) Derived From Source Hydrographic Survey Soundings Collected by NOAA
Bathymetry for the St. Johns River was derived from thirty-two surveys containing
158,931 soundings. No surveys were omitted. The average separation between soundings
was 66 meters. Twenty-nine of the thirty-three surveys dated from 1935 to 1939. The
remaining surveys, located in the north, dated from 1958 or 1959. The total range
of sounding data was 0.6 meters to - 24.7 meters at mean low water. Mean high water
values between 0.0 and 1.4 meters were assigned to the shoreline. Seven 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). The St. Johns River has twenty-nine 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.
Cite this dataset when used as a source.
- ID not available.
gov.noaa.ngdc.mgg.dem:stjohns_river_s180_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 | 1935-01-01 to 1959-01-01 |
Spatial Reference System | urn:ogc:def:crs:EPSG::586626917 |
Spatial Bounding Box Coordinates |
West:-81.768907
East:-81.386884
South:29.078468
North:30.438366
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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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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: 2018-06-14
For questions about the information on this page, please email:dem.info@noaa.gov