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Grid-based transformations directly convert map coordinates from one (map-projection, geodetic datum) pair to map coordinates of another (map-projection, geodetic datum) pair. An example is the NADCON method for transforming from the North American Datum (NAD) 1927 to the NAD 1983 datum. [ 26 ]
Geodetic latitude and geocentric latitude have different definitions. Geodetic latitude is defined as the angle between the equatorial plane and the surface normal at a point on the ellipsoid, whereas geocentric latitude is defined as the angle between the equatorial plane and a radial line connecting the centre of the ellipsoid to a point on the surface (see figure).
A WKT format is defined to describe the operation methods and parameters used to convert or transform coordinates between two different coordinate reference systems. The WKT 1 and WKT 2 formats are incompatible regarding coordinate operations, because of differences in the modelling. [13]
The list below is a collection of available official national projected Coordinate Reference Systems. Links to the relevant unique identification codes of the EPSG Geodetic Parameter Dataset, the most comprehensive collection Coordinate Reference Systems, are provided in the table.
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]
Convert from geodetic coordinates to geocentric coordinates: Calculation of x, y and z relative to the reference ellipsoid of surveying; 7-parameter transformation (where x, y and z almost always change by a few hundred metres at most, and distances by a few mm per km).
The QRA locator system was limited to describing European coordinates, and by the mid-1970s there was growing need for a global locator system. [ 3 ] By the time of their April 1980 meeting, in Maidenhead , England, the VHF Working Group had received twenty different proposals to replace the QRA locator grid.
A location can be indicated to varying resolutions numerically, usually from two digits in each coordinate (for a 1 km (0.62 mi) square) through to five (for a 1 m (3 ft 3 in)) square; the most common usage is the six figure grid reference, employing three digits in each coordinate to determine a 100 m (330 ft) square.