Estuarine Bathymetric Digital Elevation Models (30 meter resolution) Derived From Source Hydrographic Survey Soundings Collected by NOAA
These Bathymetric Digital Elevation Models (DEM) were generated from original point soundings collected during hydrographic surveys conducted by the National Ocean Service and its predecessors. Mean High Water shoreline as defined by NOAA nautical charts was used as a constraining boundary and assigned its local elevation relative to the local datum (typically Mean Low Water). In the event of multiple surveys in a region, the most recent survey soundings were retained. 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 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.
|Time Period||1839-01-01 to 1989-01-01|
|Spatial Reference System|
|Spatial Bounding Box Coordinates||
|Spatial Coverage Map|
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|Dataset Progress Status||Status not available|
|Data Update Frequency||Not planned|
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.
|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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|Use Constraints||No constraint information available|
Last Modified: 2017-04-14
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