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The NED dataset is a compilation of data from a variety of existing high-precision datasets such as LiDAR data (see also National LIDAR Dataset - USA), contour maps, USGS DEM collection, SRTM and other sources which were reorganized and combined into a seamless dataset, designed to cover all the United States territory in its continuity.
The data is free to download non-commercially and through the developer's website at a cost commercially. An alternative free global DEM is called GTOPO30 (30 arcsecond resolution , c. 1 km along the equator) is available, but its quality is variable and in some areas it is very poor.
The USGS DEM format is a self-contained (single file) set of ASCII-encoded (text) 1024-byte (1024 ASCII chars) blocks that fall into three record categories called A, B, and C. There is no cross-platform ambiguity since line ending control codes are not used, and all data including numbers is represented in readable text form.
National Geophysical Data Center: All free data from the NGSC. Includes elevation models, land cover, seismology, etc. The Geospatial Platform: Search for and download a wide variety of datasets from this portal developed by the member agencies of the Federal Geographic Data Committee through collaboration with partners and stakeholders.
DTED (or Digital Terrain Elevation Data) is a standard of digital datasets which consists of a matrix of terrain elevation values, i.e., a Digital Elevation Model.This standard was originally developed in the 1970s to support aircraft radar simulation and prediction.
Void filled SRTM data at CGIAR-CSI Archived 2013-02-07 at the Wayback Machine; USGS HydroSHEDS – Full resolution SRTM-based DEM for hydrological applications; Software that can read and process SRTM data: 3dem, GRASS GIS, SAGA GIS, MapWindow GIS, DG Terrain Viewer/Void Killer, Virtual Terrain Project
GTOPO30 is a digital elevation model for the world, developed by United States Geological Survey (USGS). It has a 30-arc second resolution (approximately 1 km), [1] and is split into 33 tiles stored in the USGS DEM file format.
Five million place names, political boundaries, latitude/longitude lines, and other data can be displayed. WorldWind.NET provided the ability to browse maps and geospatial data on the internet using the OGC's WMS servers (version 1.4 also uses WFS for downloading place names), import ESRI shapefiles and kml/kmz files. This is an example of how ...