World network of satellite triangulation

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The world network of satellite triangulation is the first global surveying network to be observed and calculated using satellite geodesy methods .

It was created in 1969–1974 in international cooperation between a few dozen states, from which only the Soviet Union and the People's Republic of China excluded each other , which is why the network of 46 satellite stations in north and east Asia has a larger gap. This made the mesh geometry less favorable, but thanks to increased measurements at the corresponding seams, it could still be designed almost ideally.

The network is based on several thousand photographically observed directions to the balloon satellite PAGEOS (initial diameter approx. 35 m), which was launched in 1966 especially for this purpose. Its originally about 4,500 km high circular orbit - its unusual flight altitude guaranteed the large-scale simultaneous observation possibility from the 3,000–6,000 km distant ground stations - fell by several hundred kilometers over the years due to the resistance of the high atmosphere , which finally ended in the mid-1970s Destruction ( re-entry ) of the satellite resulted.

The network and its political and technical planning were initiated and accompanied by the US-Swiss professor Hellmut Schmid (Institute for Geodesy and Photogrammetry at ETH Zurich ) and his results were finally published in a worldwide geophysics journal in 1974 .

For this hitherto amounting new international cooperation thousands of photographic shots with were 20 teams under Schmid's coordination BC-4 - satellite cameras made, of which, however, about half come not expected to be two to four stations, but only from one station. Such recordings can only be evaluated in terms of stellar triangulation if they are obtained from at least 2 appropriately equipped stations and are not impaired by cloud cover .

The photo plates (or plate pairs) were evaluated on stereo comparators from several participating universities and ultimately resulted in an average point accuracy of ± 4 to 5 m for the 45, later 46, ground stations involved. The last-mentioned station is located in Germany - where most of the technical and personal support after the USA came from: at a conveniently located TP of the DHDN in Bavaria, the Hohenpeissenberg . It later also became a crossing point with a base line of the European network , which runs from the fundamental station Lustbühel near Graz across Austria, southern Germany and France to the southern English station Malvern .

A combination solution with the Doppler satellite network from Ivan I. Mueller (USA) enabled the world network

  1. increased to an accuracy of 3 m and
  2. centered on the geocenter so it is too
  3. was usable for subsequent investigations to determine geoid ,
  4. for the calculation of an improved mean earth ellipsoid ,
  5. and as an early contribution to the world system of the International Terrestrial Reference Frame .

Sources and web links

  • HH Schmid 1974 (Journal of Geophysical Research)
  • IfAG and TU Wien (research reports and LVA on satellite geodesy)
  • Satellite triangulation , etc. a. using the example of the PAGEOS global network ( PDF , p. 5; 1.96 MB)