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The USGS provides the mapping and digital geospatial foundation for the Nation.

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AK Mount McKinley A-3 US Topo (Browse Image for Story Map)
The Quick Start Guide for The National Map viewer can be found here. More Info:  Tutorial videos
Image: Terrestrial Lidar to Map Flooding from Hurricane Isaac
3DEP DEMs can be ingested by many commercial GIS software.  The user will need to review specific software for compatibility.
Image: Percy Quin Dam LiDAR Scan
There are two types of metadata available for 3DEP products:  (1) spatial metadata, and (2) FGDC metadata.  Spatial metadata in the form of a shapefile is supplied as a part of each product download, or may be obtained at the Metadata  page. Polygonal footprints of the area of each source dataset contributing to the standard DEM layers provides...
Lidar data of the Gulf Islands, Florida
The most recently published figure of absolute vertical accuracy of the seamless DEMs within the conterminous United States, in terms of the National Standard for Spatial Data Accuracy (NSSDA) at 95% confidence level, is 3.04 meters. It is important to note, however, that the vertical accuracy actually varies significantly across the U.S. because...
Lidar image showing the upper parts of the landslide that occurred in northwest Washington on March 22, 2014.
The laser pulses emitted from airborne lidar systems may be reflected from man-made structures, vegetation, or the earthen surface. A single pulse may reflect from upper, middle, and lower tree canopy as well as the ground beneath, resulting in multiple measurable returns from that pulse. The elevation of the reflected surface(s) is derived based...
A multicolored lidar image of the Great Sand Dunes
The 5-meter DEMs in Alaska contain ‘DTM’ in the file names. The term digital terrain model, or DTM, is often used as a synonym for a digital elevation model for these products and should not be confused with  a triangulated irregular network which is a vector form of DTM. The USGS distributes Alaska elevation datasets that are labeled as DTM in...
Fairweather fault lidar
A digital elevation model, or DEM, is a representation of the terrain (bare-earth) with elevations at regularly spaced intervals. A digital surface model (DSM) also contains elevations at regularly spaced intervals; however, the elevations represent the first reflected surface detected by the sensor. These first returns may be reflected by bare...
excerpt of lidar imagery in Columbia Gorge
The area of coverage of any particular standard 3DEP DEM product is generally determined by the availability of source elevation data of similar or higher resolution. For example, the 1/3 arc-second layer is available for only portions of Alaska where higher resolution lidar or ifsar elevation sources exist. The 1/9 arc-second layer is available...
denuded slopes
(Public domain.) *Contact tnm_help@usgs.gov for current product volume.
Image of North Shore of Lake Tahoe from point could LiDAR data showing elevation intensity
NED data are still available and being updated continually, but the ‘NED’ terminology has been retired. The national DEM layers previously referred to as the ‘NED’ are now branded as 3DEP seamless DEMs. These seamless national DEM layers are just a few of the datasets offered in the broader suite of 3DEP elevation products. For a description of...
Lidar image of Pittsburgh
Seamless DEMs (2-, 1-, and 1/3-arc-second) are available in ArcGrid, GridFloat and IMG formats. Both of the 1/9 arc-second and 1 meter data are available in IMG format. Original product resolution DEMs are available in ArcGrid format. Accompanying metadata are available in TXT, XML and HTML with each download.
Alaska IfSAR Elevation Image
All 3DEP seamless DEMs are provided in geographic coordinates (longitude and latitude) in units of decimal degrees, horizontally referenced on the North American Datum of 1983 (NAD83). All elevation values are in units of meters, typically referenced to the North American Vertical Datum of 1988 (NAVD88), although the National Geodetic Vertical...