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
Where can I find 3D Elevation Program (3DEP) product updates and status maps?
3D Elevation Program (3DEP) product updates and status maps are available at these sites: Updates The National Map Data Delivery News Subscribe to Simple Notification Services to receive emails regarding changes to the status of The National Map Services Status Maps The National Map Download Client – Click “Show” below each elevation product LidarExplorer – Lidar point cloud only DEM Availability...
Where can I find a list of URLs for The National Map services?
See The National Map Services for a complete list of map service URLs. That includes available REST, WMS, WMTS (cached base maps only), WFS, WCS, and other service links. Learn more: Training videos for The National Map Products and Services The National Map Applications
What is the vertical accuracy of the 3D Elevation Program (3DEP) DEMs?
As of 2022, the absolute vertical accuracy of the 3D Elevation Program (3DEP) 1/3 arc-second seamless DEM product within the conterminous United States is approximately 0.82 meters root mean square error (RMSE), based on a comparison to almost 25,000 NOAA National Geodetic Survey OPUS points . Accuracy has improved from a RMSE of 1.55 meters tested in 2013, due to the addition of lidar projects...
How should I cite datasets and services from The National Map?
The USGS does not require a specific format when citing data obtained through The National Map . You should follow the citation guidelines provided by instructors or publication editors as appropriate. The following should help you find the information that you need: Citation for Datasets Author: U.S. Geological Survey Release date: the first four numbers of <pubdate> from dataset metadata for the...
What types of elevation datasets are available, what formats do they come in, and where can I download them?
Digital elevation data for the United States and its territories are available through The National Map Downloader . Click the “Help” link at the top of the page for detailed instructions on how to find and download data. There is a separate site for The National Map Services . The 3D Elevation Program (3DEP) products and services available through The National Map consist of standard digital...
What is Lidar data and where can I download it?
Light Detection and Ranging ( lidar ) is a technology used to create high-resolution models of ground elevation with a vertical accuracy of 10 centimeters (4 inches). Lidar equipment, which includes a laser scanner, a Global Positioning System (GPS), and an Inertial Navigation System (INS), is typically mounted on a small aircraft. The laser scanner transmits brief pulses of light to the ground...
Why are two different file naming conventions used in distribution of 3D Elevation Program (3DEP) DEM products?
Updated digital elevation model (DEM) dataset files are now given a name that includes information about the resolution and format of the data. This prevents users from accidentally overwriting existing data that might have different resolutions and formats. For example: an older file: n44w071.zip would now have the name: USGS_13_n44w071.tif indicating 1/3 arc-second elevation data in geotiff...
What data sources are used to produce the 3D Elevation Program (3DEP) DEMs?
The USGS 3D Elevation Program (3DEP) is in the process of collecting high-quality lidar and IfSAR (for Alaska) coverage for all of the United States and its territories. As this new data becomes available, legacy Digital Elevation Models (DEMs) are being systematically replaced with high-resolution DEMs produced almost entirely from the lidar and ifsar data. Legacy DEMs were produced from...
What is the coverage of 3D Elevation Program (3DEP) DEMs?
Elevation products are summarized on our 3-D Elevation (3DEP) Products and Services website . View detailed availability maps (status graphics) through several sites: The National Map Download Client – Click “Show” below each elevation product Lidar Availability Viewer - Lidar point cloud only LidarExplorer – Lidar point cloud only DEM Availability Viewer - 1 meter DEMs only Learn more: What is...
What is the projection, horizontal datum, vertical datum, and resolution for a USGS digital elevation model (DEM)?
Projection : 3DEP DEMS have different projections/coordinate systems depending on the product: 1/3-, 1-, and 2-arc-second (also the discontinued 1/9-arc-second) DEMs are not projected. They are all in geographic coordinates (latitude/longitude). 5-meter DEMs (Alaska only) are Alaska Albers Equal Area. 1-meter DEMs are in Universal Transverse Mercator (UTM). Original Product Resolution (OPR) DEMs...
What is the difference between lidar data and a digital elevation model (DEM)?
Light detection and ranging (lidar ) data are collected from aircraft using sensors that detect the reflections of a pulsed laser beam. The reflections are recorded as millions of individual points, collectively called a “point cloud,” that represent the 3D positions of objects on the surface including buildings, vegetation, and the ground. Digital elevation models ( DEMs ) are one of many...
How do I report errors in 3D Elevation Program (3DEP) elevation data?
If you think you’ve found an error in USGS elevation data, please send an email to tnm_help@usgs.gov . We will add the reported information to our "Digital Elevation Model Issues" data log for further analysis and possible correction. Spikes, pits, seam-line anomalies, and other data errors are of concern to us. We are working to correct or minimize known issues, but it will take some time. Errors...