3D Elevation Program Standards and Specifications

Data on America’s elevation have typically been represented as contour lines and bare earth digital elevation models (DEMs) in The National Map. Light detection and ranging (lidar) and interferometric synthetic aperture radar (ifsar) data (in Alaska) are now the primary sources of elevation data for 3DEP, and provide opportunities for measuring, mapping and monitoring not only the bare earth surface, but above ground features as well. As a result, in addition to the traditional bare earth DEMs, USGS now provides the source lidar point clouds, ifsar digital surface models (DSMs) and orthorectified radar intensity images (ORIs) over every area where data have been acquired for 3DEP and The National Map. Contours derived from these elevation data are used in the US Topo digital topographic maps. 

Three bare earth DEM layers in 3DEP are nationally seamless and are distributed in geographic coordinates at 1/3, 1, and 2 arc-seconds. Two high resolution layers over the conterminous U.S., 1/9 arc-second and 1-meter, are seamless within projects but not across projects. The 1-meter bare earth DEM dataset will be populated as new data are acquired. The quality and accuracy of these datasets are governed by standards and specifications.