National Elevation Dataset (NED) a raster product created by the U.S. Geological Survey (USGS). Drafted to provide National elevation data in a seamless form to allow projection, elevation unit and consistent datum.
Performing edge matching, artifact minimizing and fill silver areas of missing data were also designed in the National Elevation Dataset product. NED elevation values converted to decimal meters are recognized as a consistent unit of measure. The United States, Hawaii, Island Territories and Puerto Rico all have a one arc-second resolution (approx. 30 meters), while Alaska having a two arc-seconds resolution. Designing NED consisted of merging seamless dataset from multiple data sources, variety of production methods and multiple resolutions from over 50,000 different DEM data files. National Elevation Dataset raster data model is logically seamless but uses an internal tile structure initially selected as a 1- by 1-degree area and process identifies all existing DEM's available from data producers. NED system filters production artifacts, and performs coordinate transformations and any necessary datum conversions.
Processing Procedures:
(courtesy of the USGS)
NED Data Dictionary -------------------------------------------------------------
Entire National Elevation Compressed on 2 DVD-ROM's
Entire US Census Bureau Tiger 2004 Dataset on 1 DVD-ROM | 
