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The WGS 84 datum surface is an oblate spheroid with equatorial radius a = 6 378 137 m at the equator and flattening f = 1 ⁄ 298.257 223 563. The refined value of the WGS 84 gravitational constant (mass of Earth's atmosphere included) is GM = 3.986 004 418 × 10 14 m 3 /s 2. The angular velocity of the Earth is defined to be ω = 72.921 15 × ...
The ellipsoid WGS-84, widely used for mapping and satellite navigation has f close to 1/300 (more precisely, 1/298.257223563, by definition), corresponding to a difference of the major and minor semi-axes of approximately 21 km (13 miles) (more precisely, 21.3846857548205 km).
The reference ellipsoid of WGS 84 now differs slightly due to later refinements. [citation needed] The numerous other systems which have been used by diverse countries for their maps and charts are gradually dropping out of use as more and more countries move to global, geocentric reference systems using the GRS80 reference ellipsoid.
An approximate definition of sea level is the datum WGS 84, an ellipsoid, whereas a more accurate definition is Earth Gravitational Model 2008 (EGM2008), using at least 2,159 spherical harmonics. Other datums are defined for other areas or at other times; ED50 was defined in 1950 over Europe and differs from WGS 84 by a few hundred meters ...
The first EGM, EGM84, was defined as a part of WGS84 along with its reference ellipsoid. WGS84 combines the old GRS 80 with the then-latest data, namely available Doppler, satellite laser ranging, and Very Long Baseline Interferometry ( VLBI ) observations, and a new least squares method called collocation. [ 3 ]
WGS 84: World Geodetic System 1984 ... the flattening and provide an accuracy of about 0.1 mm for the WGS84 ellipsoid; ... the same ellipsoid parameters and the same ...
EPSG Geodetic Parameter Dataset (also EPSG registry) is a public registry of geodetic datums, spatial reference systems, Earth ellipsoids, coordinate transformations and related units of measurement, originated by a member of the European Petroleum Survey Group (EPSG) in 1985.
The ECEF coordinate system has the following parameters: The origin at the center of the chosen ellipsoid. In WGS 84, this is center of mass of the Earth. The Z axis is the line between the North and South Poles, with positive values increasing northward.