FAQs
For additional "Elevation" related FAQs, please visit the Mapping, Remote Sensing, and Geospatial Data Questions page and choose "Elevation" from the linked headings at top.
Visit the Mapping, Remote Sensing, and Geospatial FAQs
Data Collaboration Announcement (DCA) Specific FAQs
What is a digital elevation model (DEM)?
A Digital Elevation Model (DEM) is a representation of the bare ground (bare earth) topographic surface of the Earth excluding trees, buildings, and any other surface objects. DEMs are created from a variety of sources. USGS DEMs used to be derived primarily from topographic maps . Those are being systematically replaced with DEMs derived from high-resolution lidar and IfSAR (Alaska only) data...
How accurate are elevations generated by the Elevation Point Query Service in The National Map?
The National Map’s Elevation Point Query Service (EPQS) returns elevations that are interpolated from the 3DEP dynamic elevation service. This is a web coverage service (WCS) that includes multiple resolutions of DEMs including 1 meter resolution lidar-based DEMs where available, and 1/3 arc-second seamless DEMs. The accuracy of the elevations returned by EPQS will vary according to the source...