Central European Arc Measurement
The Central European Arc Measurement (German: Mitteleuropäische Gradmessung) was established in Berlin in October 1864, after the creation of the Swiss Geodetic Commission in 1861 and following a preliminary consultation between representatives of Prussia, Austria, and Saxony in April 1862. It became the European Arc Measurement (Europäische Gradmessung) in 1867 and the International Geodetic Association (German: Internationale Erdmessung) in 1886.
Source: Wikipedia — Central European Arc Measurement (CC BY-SA 4.0)