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 might not be fixed until new LIDAR or IFSAR is collected over the area.
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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...
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 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 products...
How do I download The National Map data products?
Download or access The National Map data products via several applications and websites: The National Map Download Client – The primary site for data downloads. See the training videos (lessons 4a-4d) or click the Help link at the top of the Downloader for detailed instructions. LidarExplorer – Lidar Point Cloud data only. See where lidar is available, get a list of downloadable products, and...
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- FAQ
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...
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 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 products...
How do I download The National Map data products?
Download or access The National Map data products via several applications and websites: The National Map Download Client – The primary site for data downloads. See the training videos (lessons 4a-4d) or click the Help link at the top of the Downloader for detailed instructions. LidarExplorer – Lidar Point Cloud data only. See where lidar is available, get a list of downloadable products, and...
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