Kremsmünster meridian arc
The Kremsmünster meridional arc was observed in the second half of the 19th century as the central part of a Central European meridional arc from Prussia to the Adriatic Sea or was compiled from older measurements. Such elongated surveying networks have been used by astronomers and geodesists to determine the exact shape of the earth since around 1800 .
The Kremsmünsterer Bogen was a double chain of triangulation points (TP) from the Upper Austrian land survey, the fundamental point of which was on the Gusterberg not far from the Kremsmünster Benedictine Abbey, and continued as an approximate north-south profile to the borders of the neighboring crown lands of Austria-Hungary . The triangulation points were selected and recognized in such a way that the triangulation chain formed from them ran as precisely as possible in the meridian of Kremsmünster (31 ° 48 'east of Ferro or 14 ° 08' from Greenwich).
Later the chain was extended beyond Upper Austria for another 250 kilometers to the north ( Bohemia ) and to the south ( Styria and Carniola ) and thus formed an arc of around 660 km on what was then Austria. With this to date longest meridian arc Grossenhain-Kremsmünster-Pola , the Vienna Military Geographic Institute and the Central European Degree Measurement Commission planned to calculate the exact course of the earth's curvature and an astro-geodetic geoid profile . For this purpose, the exact astronomical latitude from star passages was measured at some triangulation points (see Sterneck method ) as well as the azimuths of some network pages. The astronomical central point was the Kremsmünster observatory ("Mathematical Tower" of the monastery), where particularly precise astronomical coordinates were determined and a length determination - which was still very complicated at the time - was carried out. A geophysical observatory and a weather station were already connected to the observatory , which today has the longest climatic measurement series in the world.
In the north, the meridian arc was continued for about 70 km by the Saxon-Prussian land survey ( Royal Prussian Geodetic Institute ) and was sometimes referred to as the Berlin meridian . It ran from the Bohemian border via Dresden to Grossenhain (Saxony), where the astronomical end point was set up. The southern end point was the Austrian naval observatory Pola on the coast of Istria , which later became internationally known through the asteroid discoveries by Johann Palisa .