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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 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 ...
Other than SRTM30plus, Earth2014 provides information on ice-sheet heights and bedrock (that is, topography below the ice) over Antarctica and Greenland. Another global model is Global Multi-resolution Terrain Elevation Data 2010 (GMTED2010) with 7.5 arc second resolution. It is based on SRTM data and combines other data outside SRTM coverage.
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]
The first multi-sheet topographic map series of an entire country, the Carte géométrique de la France, was completed in 1789. [9] The Great Trigonometric Survey of India, started by the East India Company in 1802, then taken over by the British Raj after 1857 was notable as a successful effort on a larger scale and for accurately determining ...
The elevation of a geographic area may be stated in several ways. These include: The maximum elevation of the area (high point); [a] The minimum elevation of the area (low point); [b] The arithmetic mean elevation of the area (statistical mean elevation); [c] The median elevation of the area (statistical 50% elevation); [d] and; The elevation ...
Since NGVD 29 used a simple model of gravity based on latitude to calculate the geoid and did not take into account other variations, [citation needed] elevation difference between points in a local area in it and NAVD 88 will show negligible change from one datum to the other, even though the elevation of both does change between datums.
Heights for measured points are shown on National Geodetic Survey data sheets, [3] data that was gathered over many decades by precise spirit leveling over thousands of miles. Alternatives to orthometric height include dynamic height and normal height , and various countries may choose to operate with those definitions instead of orthometric.