Fundamentalstation

A fundamental station serves to anchor a high-precision geodetic coordinate frame on the earth's surface and is mostly a particularly well-equipped satellite station. It establishes the relationship from terrestrial to zälestischen ( astronomical ) fundamental system, which is defined by certain celestial bodies and their measurement in the night sky.

Such a station is an observatory comparable, which specializes in artificial earth satellites and quasars as well as other methods of astrometry. She works with different measurement systems - mainly radio and laser measurements to satellite, GPS, GLONASS and VLBI - the market on a larger number of geologically most stable measurement points refer. Also, a high-precision time system with maser atomic clocks or part of the equipment.

Continental drift millimeter

At the global level today accuracies of 1 cm and more easily accessible, which is both for astronomy and geodesy and geodynamics of great importance. So you can now demonstrate the movements of plate tectonics and directly model the velocities of the individual continental plates in the order of millimeters per year. Also, other movements of the earth ( earth tides, nutation, polar motion, etc.) and the calculation of its elasticity, are made possible by such fundamental stations.

The most important fundamental station in Europe is located in the Bavarian Forest in Wettzell, a remote district of Bad Kötzting near the German -Czech border. It is operated by the Federal Agency for Cartography and Geodesy ( BKG, Frankfurt am Main ) and the Research Satellite Geodesy ( FESG ) at the TU Munich as part of the nationwide research group Satellite Geodesy ( FGS ).

Worldwide network

Other fundamental stations are located in southern Italy, on the Black Sea, in East Asia, USA, Chile and South Africa. Other observatories have largely this status, including in Graz- Lustbühel ( Austria ), in room near Bern, as well as in France, Sweden and North America. Larger gaps in the global network - especially in laser and radio telescopes - still exist in Africa, South Asia and Australia.

Underlies all these precision methods, the fundamental astronomical system that is based on 500 quasars at the edge of the visible universe and about 4000 precisely measured fundamental stars of our galaxy. Your currently current coordinates were published as FK6 ( Astronomical Computing Institute (ARI ) in Heidelberg) in 2000.

Terrestrial fundamental system

The terrestrial equivalent of this celestial system - " brought down " on the rotating therein " centrifugal Earth" - called ITRS (International Terrestrial Reference System), and the associated global survey network ITRF ( ... frame for coordinate frame ). To him bear - in addition to the continental fundamental stations - also numerous permanent GPS stations at, as well as some observatories with CCD and other measurement methods. From each station involved in the ITRS not only the coordinates for position and height, but also the components of the velocity can be determined. However, they are only about one to ten centimeters a year. All stations along with their six vectors form a kind of terrestrial coordinates directory that is called (F -frame ) ITRF.

The relation of the global reference system to the measurement points of the respective State Survey is prepared by coordinate transformations. It can be carried out either 3D (see Figure 7 - transformation parameters ) and separated by layer ( 2D) and height (see geoid and height measurement).