Title:
National Elevation Dataset
Originator: U.S. Geological Survey (USGS), EROS Data Center
Abstract:
The U.S. Geological Survey has developed a National Elevation Database (NED).The NED is a seamless mosaic of best-available elevation data. The 7.5-minute elevation data for the conterminous United States are the primary initial source data. In addition to the availability of complete 7.5-minute data, efficient processing methods were developed to filter production artifacts in the existing data, convert to a consistent datum, edge-match, fill slivers of missing data at quadrangle seams, recast the data to a consistent geographic projection and convert all elevation values to decimal meters as a consistent unit of measure.
NED has a resolution of one-third arc-second (approximately 10 meters) for much of the conterminous United States, Hawaii and Puerto Rico in a NAD83 datum. There is a resolution of two arc-seconds (approximately 60 meters) for Alaska and the datum is NAD27. The vertical datum for all areas, except Alaska, is NAVD88. Alaska is NAVD29.
NED at 10 meters is created using the same methods outlined above with the source data being mostly the 10m DEMs. DEMs at 5 meters, 1/3 arc-second, and 1/9 arc-second maps are also used where available. In some cases, the 10m NED is resampled from LIDAR or created using aerial photography.
One of the effects of the NED processing steps is a much-improved base of elevation data for calculating slope and hydrologic derivatives. Artifact removal greatly improves the quality of the slope, shaded-relief, and synthetic drainage information that can be derived from the elevation data. Geospatial elevation data are used by the scientific and resource management communities for global change research, hydrologic modeling, resource monitoring, mapping, and visualization applications.
The 30 meter NED is ~1 arc-second data that is updated over large areas by integrating the 10 meter or better source data(where available), re-sampled to 1 arc-second. Where 10 meter or better is not available, 30 meter is used.
NRCS has elected to ONLY serve NED 30 (NED 60 in Alaska) maps in a UTM projection and in one degree quadrangles. These two facts differentiate the maps from those served at http://seamless.usgs.gov/.
NRCS has also elected to ONLY serve NED 10 which is 10 meter or better and not NED 10 which was resampled from 30 meter. NRCS also serves the maps in a UTM projection in seven and one-half minute quadrangles. These two facts differentiate the maps from those served at http://seamless.usgs.gov/.
In addition NRCS has elected to ONLY serve NED one-ninth (approximately 3 meters) maps in a UTM projection and in seven and one-half minute quadrangles. These facts differentiate the maps from those served at http://seamless.usgs.gov/.
Format:
GeoTIFF
Spatial Reference Information: Universal Transverse Mercator, North
American Datum 1983 (1927 for AK)
