Réseau Européen des Triangulations

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The Réseau Européen des Triangulations ( RETrig ) is a European network , the work of which began in the 1950s .

The aim of the RETrig was to make the surveying networks of as many European countries as possible comparable for international tasks and research purposes and to calculate their margins in a uniform reference system . As a result, responsibility and availability remained with the individual states, but overarching calculations became possible. The IAG had its own RETrig subcommittee for this purpose, which was decided in 1955 at the IUGG general assembly in Rome.

For political reasons, however, the RETrig was only implemented in Western Europe (see also ED50 and ED79 ) and could not be extended to the Eastern Bloc . With the political turn of 1989 /90, the project had so far is unnecessary, as the growing importance of GPS was foreseeable -Vermessungen. In order to meet the new challenges, the new IAG sub-commission EUREF ( European Reference Frame ) was founded instead of RETrig . It primarily deals with the question of the reference systems ( geodetic datum ) and makes suggestions for better international comparability of the geodetic basic data.

Project phases

The starting point of the RETrig was the Central European Network , which began in the Third Reich as an extensive framework network across Central and Central Eastern Europe and was completed under US leadership in 1948. In the following years it was newer delta measurements ( triangulation supplemented) and formed as a European date 1950 (ED50) for two decades a unified coordinate system for the participating 15 countries of Central and Western Europe.

With the founding of the RETrig Commission in 1955, an improvement of the initially only approximately balanced European network was designed in several steps:

  • Phase I: mathematically strict network balancing of an evenly condensed triangulation using the Helmert Blocking method , in which only the data from the TPs near the border is exchanged between the states . Failures by individual countries resulted in several delays. It was not until 1978 that the network relating to the central point in Munich was published as the European date 1977 .
  • Phase II: Inclusion of astro-geodetic measurements on all TPs in order to correct the influence of the vertical deviations , as well as numerous Laplace azimuths to stiffen the network. The result was called European Date 1979 and formed the most precise coordinate frame in Europe until the 1990s.
  • Phase III: Inclusion of satellite measurements on some fundamental stations and a further 120 points (eight Doppler and one GPS campaign, SLR laser measurements). After initial results in 1985, the combined network was presented at the RETrig symposium as the European date 1987 .
  • Further development to the ETRS reference system from around 1995.

See also

literature

  • Karl Ledersteger : Astronomical and Physical Geodesy (§28, The European Network ). Volume V of the series of reference books Jordan-Eggert-Kneissl, Handbuch der Vermessungskunde, Verlag JB Metzler, Stuttgart 1969
  • Wolfgang Torge : Geodesy (chapter earth measurement , p.163ff). De Gruyter, Berlin 1975
  • Walter Ehrnsperger: The ED87 Adjustment . Bulletin Géodésique 1991, Vol.65, p.28-43, Paris 1991, Online p.28 / 29