Tartu Observatory - start the Struve Geodetic Arc

The Tartu Observatory is the largest astronomical observatory in Estonia. Tartu Old Observatory is known internationally for its connection to Friedrich Georg Wilhelm von Struve and the Struve Geodetic Arc, of which it is the first point.

The Struve Geodetic Arc is a chain of survey triangulations stretching from Hammerfest in Norway to the Black Sea, through ten countries and over 2,820 km. The chain was established and used by the German-born Russian scientist Friedrich Georg Wilhelm von Struve in the years 1816 to 1855 to establish the exact size and shape of the earth. At that time, the chain passed merely through two countries: Sweden-Norway and the Russian Empire. The Arc's first point is located in Tartu Observatory, where Struve conducted much of his research. In 2005, the chain was inscribed on the World Heritage List.

Measurement of the triangulation chain took place between 1816 and 1855. It comprises 258 main triangles and 265 geodetic vertices. The northernmost point is located near Hammerfest in Norway and the southernmost point near the Black Sea in Ukraine.