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 NED serves as the elevation layer of The National Map, and provides elevation information for earth science studies and mapping applications in the United States.
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.
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.
The NED data are not projected, but are provided in geographic coordinates (latitude and longitude) in units of decimal degrees, horizontally referenced on the North American Datum of 1983.
NED source data are selected from an inventory of standard production USGS digital elevation models (DEMs), and from an increasing number of datasets that are project- or agency-specific.
NED data (either 2-, 1-, or 1/3-arc-second resolutions) are available in ArcGrid, GridFloat, and IMG formats. NED 1/9 arc-second data are available in IMG format only. Accompanying metadata are available in TXT, XML, and HTML with each download.
Creating shaded relief directly from NED data can be problematic, because the horizontal units are in decimal degrees but vertical units are in meters.