Potsdam gravity system

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The Potsdam Gravity System (ger .: Potsdam system) was from 1909 to 1971 an international significance as a reference with high accuracy for gravimetric gravity values .

Friedrich Robert Helmert shaped the work of the Royal Prussian Geodetic Institute in Potsdam from 1886 to 1917. One focus of his work was the research and description of the earth figure as an equipotential surface of gravity at sea level ( geoid ). The most diverse gravimetric work was therefore of great importance. According to the statute of the Geodetic Institute from 1887 this u. a. assigned the task of "determining the intensity of severity at as many points as possible".

In the new building of the Geodetic Institute on the Telegrafenberg in Potsdam, a temperature-stabilized room, the pendulum room, was set up inside the building with a double pillar for reversing pendulum measurements and three further pillars for measurements with relative pendulum devices. In 1898 Helmert commissioned Friedrich Kühnen and Philipp Furtwängler to carry out reversion pendulum measurements; a total of five high-precision pendulums were used. From the measurements carried out between 1898 and 1904, Kühnen and Furtwängler derived the known value as the final result

g = 981.274 ± 0.003 cm / s² (Potsdam fundamental constant)

based on the height "87 m above sea level".

In 1909 Helmert - according to a report by Professor Emil Borraß - introduced the Potsdam gravity system with the absolute value determined by Kühnen and Furtwängler, based on the location of these measurements, as an international reference value at the conference of international earth measurements in Cambridge (Great Britain). This value, approved by the conference, was the first internationally used gravity reference system and established an absolute gravity level with reference to the Potsdam reference point in the pendulum hall. Until then - since 1892 - a Viennese gravity system had initially been used as an absolute reference with the absolute values ​​of gravity for Vienna determined by Robert von Sterneck , Theodor von Oppolzer and von Orff.

Reversion pendulum measurements by Paul R. Heyl and Guy S. Cook from 1934 to 1935 at the National Bureau of Standards in Washington, DC (USA) and JS Clark from 1936 to 1938 at the National Physical Laboratory in Teddington (Great Britain) already indicated differences of −0.020 cm / s² or −0.0138 cm / s² indicates a larger systematic error in the Potsdam reference value.

The following international activities to correct the Potsdam gravity system dragged on until the early 1970s. By recommendation of the 15th General Assembly of the International Union for Geodesy and Geophysics (IUGG) in Moscow, the Potsdam system was replaced by an International Gravity Standardization Net (IGSN 71); Potsdam was included in this as one of a total of 1854 stations. The gravity values ​​of the Potsdam gravity system are according to recent measurements and thus also compared to z. B. the IGSN71 by approx. 140 to 150 μm / s² too large. The ultimate cause of this discrepancy has not yet been fully clarified without any doubt.

See also

literature

  • Emil Borraß : Report on the relative measurements of gravity with pendulum apparatus in the period from 1808 to 1909 and on their representation in the Potsdam gravity system. Negotiations of the Sixteenth General Conference on International Geometric Surveying, held in London and Cambridge in 1909. III. Part: Special report on the relative gravity measurements. Reimer, Berlin 1911
  • Friedrich Kühnen and Philipp Furtwängler : "Determination of the absolute magnitude of gravity in Potsdam with reversion pendulums", Königl. prussia. Geodesic. Institute, New Series No. 27, Berlin, 1906
  • Joachim Höpfner : Absolute determination of gravity with reversion pendulums in Potsdam / 1898 - 1904 and 1968 - 1969, annual publication 2012 of the German Society for Chronometrie, vol. 51, pp. 101–114
  • E. Rieckmann and Sigmar German : "The Potsdam heavy system, its complete definition and its correct transfer", German Geodetic Commission at the Bavarian Academy of Sciences: Series B, Applied Geodesy; No. 50
  • H. Schmehl: The Potsdam gravity system. In memory of Friedrich J. Kühnen and Philipp FP Furtwängler. Research and progress 16 (1940) 19/20, p. 220
  • Wolfgang Torge : History of geodesy in Germany , Walter de Gruyter, Berlin 2007, ISBN 978-3-11-019056-4

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