Color Shaded Relief Map of the Conterminous United States

The data set traces its origins back to the early 1960's when .01 inch scans of 1:250,000 USGS topographic sheets were produced by the Defense Mapping Agency and converted to 3 second data by the USGS National Cartographic Information Center. The 15 second grid cell data (Michael Webring, written communication) used in this report dates from the mid-1980's with occasional local and regional updates.

The 3 second grid nodes were averaged with a 6x6 operator and decimated to 15 second grid cells which is about the resolution of the original .01 inch data set. The 3 second data is available as 950 separate 1x1 degree quadrangles from the USGS EROS Data Center. Additional information available at "pubs.usgs.gov/of/of99-011/1readme.html" [Summary provided by the USGS.] .