| NOAA’s National Geophysical Data Center (NGDC) builds and distributes high-resolution,
coastal digital elevation models (DEMs) that integrate ocean bathymetry and land topography
to support NOAA’s mission to understand and predict changes in Earth’s environment,
and conserve and manage coastal and marine resources to meet our Nation’s economic,
social, and environmental needs. Bathymetric, topographic, and shoreline data used
in DEM compilation are obtained from various sources, including NGDC, the U.S. National
Ocean Service (NOS), the U.S. Geological Survey (USGS), the U.S. Army Corps of Engineers
(USACE), the Federal Emergency Management Agency (FEMA), and other federal, state,
and local government agencies, academic institutions, and private companies. DEMs
are referenced to a variety of vertical tidal datums, generally Mean High Water, and
horizontal datum of World Geodetic System 1984 (WGS84). Cell size is based on user
requirements and generally range from 1/3 arc-second (~10 meters) to 1 arc-second.
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