World Geodetic System
The World Geodetic System (abbreviated WGS ) is a global reference system for geodesy and navigation . Today, WGS is usually understood to be the so-called WGS 84 - currently the most common global reference system.
It represents the most far-reaching step to date in the standardization of dozens of national surveying systems into a common world system.
history
Central Bureau for International Earth Surveying (1880)
The efforts to build up geodetic world systems began at the end of the 19th century , especially with the work of the then most famous German geodesist Friedrich Robert Helmert and the establishment of the "Central Bureau for International Earth Measurement " around 1880 at the suggestion of Austria-Hungary . The rapid development of science and technology made, among other things, a computational merger of the national surveying systems appear useful, which then - and largely to this day - were based on reference ellipsoids regionally adapted to the geoid and their associated fundamental points .
Helmert Ellipsoid (1906)
Because of the irregularities of the gravity field - see vertical deviation and gravity anomalies - such a computational coordination turned out to be more difficult than initially assumed. Large-scale measurements were essentially limited to triangulation and its range of 50 to 100 km, which was only possible across the oceans using island chains . With the theoretical work of Helmert, Heinrich Bruns and others, an international cooperation began in practice , which was mainly promoted by Germany and Austria. From around 1910 the USA also took part more intensively.
Hayford Ellipsoid (1924)
John Fillmore Hayford calculated " absolute vertical deviations " of some continents on the basis of isostasy - the theory of a state of equilibrium in the subsurface of the continents - and derived the so-called Hayford ellipsoid from this. It was adopted by the IUGG in 1924 as the "international ellipsoid". Its equator axis a = 6378 388 m deviates from the modern value by only 250 m (0.004 percent), its polar (small) axis by 90 m ( flattening 1: 297). The earlier ellipsoid by Friedrich Robert Helmert (1906) is noticeably more precise in both values.
International Ellipsoid (1967)
The Hayford ellipsoid from 1924 and the associated gravity formula were replaced 43 years later at the IUGG general assembly in Lucerne with the "international ellipsoid 1967 ( a = 6378 160 m). This already contains the most important results of satellite geodesy , it had but not a long inventory: in 1979 - in coordination with the International Astronomical Union (IAU) - the new "Geodetic Reference System 1980" ( GRS 80 ) was decided, which is already accurate to 1 meter and will be maintained until about 2010 , although it is now Could improve data to within a few centimeters .
World Geodetic System (WGS)
In a narrower sense , WGS means a series of global reference systems , all of which go back to space travel and its impetus for increased international cooperation within the natural sciences .
WGS-60
These "world systems" began with the WGS-60 from the time when the first successes of geodetic satellites made it possible to survey the earth 10 times more precisely than before. Soon however, this frame of reference became
WHS-72
Replaced by WGS-72 , on which " Doppler navigation " with the transit satellite system NNSS is based. It worked with the Doppler effect and made it possible to improve the coordinate transformation across all oceans from about ± 50 m to meter accuracy . Its values for earth mass and earth rotation are already of very high quality.
WGS-84
In the WGS-84 system, the ellipsoid axis only had to be changed by 2 meters to a = 6378 137 m (see also GRS 80 ), but physical parameters were required for a more precise " earth model " - especially for a more detailed earth's gravity field and for GPS - Navigation - added.