The term fundamental station is used for special observatories which combine several space positioning techniques like VLBI, satellite laser ranging,

GPS The Global Positioning System (GPS), originally Navstar GPS, is a Radionavigation-satellite service, satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of t ...

, Glonass, etc. They are the basis of

plate tectonic Plate tectonics (from the la, label=Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large te ...

analysis, allowing the monitoring of continental drift rates with millimetre accuracies. A fundamental point is the geometric origin of a geodetic network and defines the geodetic datum of a

national survey A national mapping agency is an organisation, usually publicly owned, that produces topographic maps and geographic data, geographic information of a country. Some national mapping agencies also deal with cadastre, cadastral matters. According to ...

. Some fundamental stations are an astronomical or satellite geodetic

observatory An observatory is a location used for observing terrestrial, marine, or celestial events. Astronomy, climatology/meteorology, geophysical, oceanography and volcanology are examples of disciplines for which observatories have been constructed. His ...

. In any case, the

geographic latitude In geography, latitude is a coordinate that specifies the north–south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north pole ...

and longitude of the station is precisely determined by methods of

astrogeodesy Geodetic astronomy or astronomical geodesy (astro-geodesy) is the application of astronomical methods into geodetic networks and other technical projects of geodesy. Applications The most important applications are: * Establishment of geodetic d ...

and is chosen as

ellipsoid An ellipsoid is a surface that may be obtained from a sphere by deforming it by means of directional scalings, or more generally, of an affine transformation. An ellipsoid is a quadric surface; that is, a surface that may be defined as the ...

al latitude and longitude at the Earth ellipsoid which is used to calculate the coordinates of the whole network. Also, precise azimuths to one or two network points are observed, and are taken over as orientated

directions Direction may refer to: *Relative direction, for instance left, right, forward, backwards, up, and down ** Anatomical terms of location for those used in anatomy ** List of ship directions *Cardinal direction Mathematics and science *Direction ...

of these network lines. By these procedure, the polar axis of the reference ellipsoid becomes parallel to the Earth rotation axis, and therefore the vertical deflection of the fundamental point is zero. Important fundamental stations in Europe are located in: * Grasse, central France *

Graz Graz (; sl, Gradec) is the capital city of the Austrian state of Styria and second-largest city in Austria after Vienna. As of 1 January 2021, it had a population of 331,562 (294,236 of whom had principal-residence status). In 2018, the popul ...

-Lustbühel, Austria *

Malvern Malvern or Malverne may refer to: Places Australia * Malvern, South Australia, a suburb of Adelaide * Malvern, Victoria, a suburb of Melbourne * City of Malvern, a former local government area near Melbourne * Electoral district of Malvern, an e ...

, England (?) *

Onsala Space Observatory Onsala Space Observatory (OSO), the Swedish National Facility for Radio Astronomy, provides scientists with equipment to study the Earth and the rest of the Universe. The observatory operates two radio telescopes in Onsala, 45 km south of Got ...

(large

radio telescope A radio telescope is a specialized antenna and radio receiver used to detect radio waves from astronomical radio sources in the sky. Radio telescopes are the main observing instrument used in radio astronomy, which studies the radio frequency ...

), Sweden * Wettzell (20m radio telescope) in the Bayerischer Wald, Germany *

Zimmerwald Zimmerwald was an independent municipality in the Canton of Bern, Switzerland until 31 December 2003. It is located on a hill in the proximity of the city of Bern in the Bernese Mittelland. On 1 January 2004 Zimmerwald united with the municipality ...

near Berne, Switzerland. Worldwide about 30 fundamental stations are in existence: about 5 in the United States and in Commonwealth of Independent States countries, and 2–3 in South America, Africa, Eastern Asia, Australia and Antarctica. The basic

coordinate system In geometry, a coordinate system is a system that uses one or more numbers, or coordinates, to uniquely determine the position of the points or other geometric elements on a manifold such as Euclidean space. The order of the coordinates is sig ...

is the ITRF reference frame, which is related to the ICRS celestial

inertial system In classical physics and special relativity, an inertial frame of reference (also called inertial reference frame, inertial frame, inertial space, or Galilean reference frame) is a frame of reference that is not undergoing any acceleration ...

by means of very precise

Earth Orientation Parameters In geodesy and astrometry, earth orientation parameters (EOP) describe irregularities in the rotation of planet Earth. EOP provide the rotational transform from the International Terrestrial Reference System (ITRS) to the International Celestia ...

(EOPs), containing polar coordinates, Earth rotation and nutation parameters. The ITRF data set is revised every 3–5 years, the actual accuracy is in the millimeter area. The ICRS is based on about 500

quasar A quasar is an extremely Luminosity, luminous active galactic nucleus (AGN). It is pronounced , and sometimes known as a quasi-stellar object, abbreviated QSO. This emission from a galaxy nucleus is powered by a supermassive black hole with a m ...

s in the far universe, and on some 3000

fundamental star Fundamental may refer to: * Foundation of reality * Fundamental frequency, as in music or phonetics, often referred to as simply a "fundamental" * Fundamentalism, the belief in, and usually the strict adherence to, the simple or "fundamental" idea ...

s of our

galaxy A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System. ...

. The actual coordinates of the latter (

FK6 The Catalogue of Fundamental Stars is a series of six astrometric catalogues of high precision positional data for a small selection of stars to define a celestial reference frame, which is a standard coordinate system for measuring positions of st ...

) were published in 2000 by the Astronomisches Rechen-Institut (ARI) in Heidelberg.

External links

Fundamentalstation Wettzell, Bavaria

* ttp://www.ari.uni-heidelberg.de/publikationen/vhd/vhd035/fulltext/gifframe.htm Fundamental system FK6, Astronomisches Rechen-Institut (ARI), 1999 Geodesy Astrometry {{geodesy-stub