The seamless elevation layers are derived from diverse source data that are processed to a common coordinate system and unit of vertical measure. All seamless elevation values are in meters.
The Shuttle Radar Topography Mission (SRTM) digital elevation dataset was collected by a modified radar system that flew on board the Space Shuttle Endeavor in February 2000, using a technique known as Interferometric Synthetic Aperture Radar (IfSAR) t
The data serves as the elevation theme of The National Map, and provides elevation information for earth science studies and mapping applications in the United States.
Elevation data are updated continually as new data become available.
To cite the NED in a publication, please use the following literature references:
Yes, lidar data are highly dense point data representing an x, y, z location, along with other attributes, of any terrestrial target reflecting the laser pulse.
Specific data for average (or mean) county elevations for the United States do not exist at USGS nor is it easily extracted from The National Map. You can extract an elevation for the centroid of each county polygo
Specific data for current mountain peak elevations do not exist at USGS other than what was previously published in an Elevations and Distances in the United States booklet.
NED Release Notes were previously produced to provide details about the current and previous releases of the NED, its source data, and noteworthy characteristics of the dataset including accuracy, data distribution statistics, and processing notes.
All NED layers, except the 1-meter layer are provided in geographic coordinates (latitude and longitude) in units of decimal degrees, horizontally referenced on the North American Datum of 1983.