Grossenhain-Kremsmünster-Pola meridian arc

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The Grossenhain-Kremsmünster-Pola meridian arch was a major project of Central European degree measurement carried out at the end of the 19th century under the auspices of Austria-Hungary . The approximately 700 km long triangulation chain from Saxony via Bohemia, Upper Austria and Styria to the Adriatic served the goal of determining the exact shape of the geoid in a north-south profile.

The geodetic measurements were carried out using the most modern methods and instruments at the time and were also integrated into the individual national surveys of the crown lands involved. In addition, a computational connection of the individual height systems was planned, but was only completed by later projects. The main active organizations were the Vienna Military Geographic Institute (for Bohemia, Austria and the Adriatic Coast) and the Royal Prussian Geodetic Institute (for Saxony) in Potsdam, which also contributed a small geoid study in the Harz region .

Saxon network and Großenhainer baseline

While the geometric determination of the triangular double chain was carried out by precision angle measurement with large triangulation theodolites , the network scale was determined by several long baselines , of which the northernmost as the Großenhainer baseline was also used as the basis for the Saxon land survey. The basic measurement (length measurement with true 6-digit accuracy) was carried out between its two endpoints using the Bessel measuring apparatus; her result was 8,908.648 meters. Starting from the base, this route was transferred to the Collm - Keulenberg triangle side, thus determining the scale of the entire triangular network.

Bohemian and Austrian network

The length of the double chain of points in Bohemia (now the Czech Republic) is about 2 × 250 km. The 15 network points of the first order were stiffened at Dablitz (north of Prague) and at Kameik by the additional point of a connecting chain and 2 × 3 visors.

The power supply unit in the south ( Upper Austria and Styria ) consists of 10 network points and runs as a stiffened double chain over about 2 × 200 km.

Network through Slovenia and the Adriatic coast

The southernmost part of the meridian arc runs from the Drava via Ljubljana (today Slovenia) to the Istrian peninsula and ends at the Pola marine observatory . It comprises 7 points (plus one near the Styrian border).

literature

  • Richard Schumann , Friedrich Hopfner : The meridian arc Grossenhain-Kremsmünster-Pola . Astronomical work of the Austrian measurement office , new series, volume I of the ÖKIE , pp. 4ff and 105ff, Federal Surveying Office, Vienna 1922
  • Karl Ledersteger: The approximation methods of astronomical leveling and the geoid in the northern part of the meridian arc Grossenhain-Kremsmünster-Pola . In: Austrian Journal for Surveying . tape 39 , no. 4 , 1951, pp. 37-45, 73-80, 108-112 .