The National Elevation Dataset (NED) is a new raster product assembled by the U.S. Geological Survey. NED is designed to provide National elevation data in a seamless form with a consistent datum, elevation unit, and projection. Data corrections were made in the NED assembly process to minimize artifacts, perform edge matching, and fill sliver areas of missing data. NED has a resolution of 10 and 30 meters for the continuous United States, Hawaii, Puerto Rico and Virgin Islands and a resolution of 60 Meters for Alaska.
NED data sources have a variety of elevation units, horizontal datums, and map projections. In the NED assembly process the elevation values are converted to decimal meters as a consistent unit of measure, NAD83 is consistently used as horizontal datum, and all the data are recast in a geographic projection. Older DEM's produced by methods that are now obsolete have been filtered during the NED assembly process to minimize artifacts that are commonly found in data produced by these methods. Artifact removal greatly improves the quality of the slope, shaded-relief, and synthetic drainage information that can be derived from the elevation data. The figure below illustrates the results of this artifact removal filtering. NED processing also includes steps to adjust values where adjacent DEM's do not match well, and to fill sliver areas of missing data between DEM's. These processing steps ensure that NED has no void areas and artificial discontinuities have been minimized.
Shaded-relief representation of the Rockypoint, Wyoming 7.5-minute DEM is shown above on the left. The same area is shown on the right after NED artifact filtering has been performed. The super-imposed red lines are synthetic drainage networks derived from each elevation dataset.
- Horizontal Resolution
- 10 Meter resolution for Continental US - Also known as 1/3 Arc Second Resolution
- Vertical Resolution - 1 DeciMeter or 10 CM or approximately 4 Inches.
- Vertical Datum - NAVD88
RMM CADD Service also offers the following DEM's in Shaded Relief: