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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. According to DTED and USGS DEM the absolute vertical accuracy of GTOP30 varies from ±30 meters. [2]
Derivative files of lower quality such as bitmap, or modest quality / simplified SVG can be published and share under the CC-by-sa-3.0 license. »For location maps, large and local, and complex maps (political, military, history). Countries: Naturalearthdata.com: Admin level 0 : Countries polygons (10m-admin-0-countries) (2009, Public domain).
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.
This is a list of free and open-source software for geological data handling and interpretation. The list is split into broad categories, depending on the intended use of the software and its scope of functionality. Notice that 'free and open-source' requires that the source code is available and users are given a free software license.
The National Elevation Dataset (NED) consists of high precision topography or ground surface elevation data (digital elevation model) for the United States. It was maintained by the USGS and all the data is in the public domain. Since the 3D Elevation Program came online, the NED was subsumed [1] into The National Map as one of its layers of ...
USGS DEM – The USGS' Digital Elevation Model GTOPO30 – Large complete Earth elevation model at 30 arc seconds, delivered in the USGS DEM format; DTED – National Geospatial-Intelligence Agency (NGA)'s Digital Terrain Elevation Data, the military standard for elevation data; World file – Georeferencing a raster image file (e.g. JPEG, BMP)
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.
The elevation models are arranged into tiles, each covering one degree of latitude and one degree of longitude, named according to their south western corners. For example, "n45e006" stretches from 45°N 6°E to 46°N 7°E and "s45w006" from 45°S 6°W to 44°S 5°W .