The USGS 3D Elevation Program (3DEP) Datasets from The National Map are the primary elevation data product produced and distributed by the USGS. The 3DEP program provides a variety of resolution raster elevation data of the conterminous United States, Alaska, Hawaii, and the island territories. Some of the data sets, such as the 1/3rd arc-second dataset, are derived from diverse source data sets that are processed to a specification with a consistent resolution, coordinate system, elevation units, and horizontal and vertical datums. These seamless DEMs were referred to as the National Elevation Dataset (NED) from about 2000 through 2015 at which time they became the seamless DEM layers under the 3DEP program and the NED name and system were retired.
USGS Standard DEMs represent the topographic surface of the earth and contain flattened water surfaces. Each DEM dataset is identified by its horizontal resolution and is produced to a consistent set of specifications. The elevations in these DEMs represent the topographic bare-earth surface. Standard DEMs are characterized either as project-based or seamless. Seamless DEMs (e.g. 1/3 arc-second) are produced by blending only the highest quality project data into a continuous terrain surface for the U.S., and are updated continuously to integrate newly available, improved elevation source data. The 1/3 arc-second (~10 meter) DEM is the highest resolution seamless DEM dataset for the U.S. with full coverage of the 48 conterminous states, Hawaii, and U.S. territories. Alaska coverage is partially available and is being expanded to statewide coverage as part of the Alaska Mapping Initiative.Note: Metadata for the different USGS raster products can be found here. All 3DEP products are public domain. For more details about the USGS 3DEP DEMs visit this USGS page.