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The 1980 Geodetic Reference System (GRS 80) posited a 6 378 137 m semi-major axis and a 1 ⁄ 298.257222101 flattening. This system was adopted at the XVII General Assembly of the International Union of Geodesy and Geophysics in Canberra, Australia, 1979. The GRS 80 reference system was originally used by the World Geodetic System 1984 (WGS 84 ...
For example, gravity is 0.1% stronger in the northern United States than in the southern, so a level surface that has an orthometric height of 1000 meters in one place will be 1001 meters high in other places. In fact, dynamic height is the most appropriate height measure when working with the level of water over a large geographic area. [4]
This sort of seasonal variation has an amplitude of around 1 cm and is attributed to non-tidal loading effects (e.g. the shifting weight of water). ITRF2008 2005.0 5332 7911 8999 Includes tropospheric modeling and improved solution methods. [6] ITRF2014 2010.0 7789 7912 9000 Generated with an enhanced modeling of nonlinear station motions. [7]
A topographic survey is typically based upon a systematic observation and published as a map series, made up of two or more map sheets that combine to form the whole map. A topographic map series uses a common specification that includes the range of cartographic symbols employed, as well as a standard geodetic framework that defines the map ...
A topographical map is the main type of map used to depict elevation, often through contour lines. In a Geographic Information System (GIS), digital elevation models (DEM) are commonly used to represent the surface (topography) of a place, through a raster (grid) dataset of elevations. Digital terrain models are another way to represent terrain ...
It traces its history to the Survey of the Coast, which was formed in 1807 as the first scientific agency of the U.S. federal government. It became the United States Coast Survey in 1836 and the United States Coast and Geodetic Survey in 1878, the latter name change reflecting the increasing role of geodesy in its work. Upon the creation of ...
The current geodetic model of the Earth used in the US is the North American Datum 1983, often called NAD83. The system is used to define horizontal co-ordinates of reference markers all over the US. Although created as a geocentric datum which originates at the center of the Earth, more recent models of the Earth have shown the origin to be 2. ...
A geodetic datum or geodetic system (also: geodetic reference datum, geodetic reference system, or geodetic reference frame, or terrestrial reference frame) is a global datum reference or reference frame for unambiguously representing the position of locations on Earth by means of either geodetic coordinates (and related vertical coordinates) or geocentric coordinates. [1]