Estonian Geodetic and Gravimetric Networks and Geoid Undulation

The national triangulation and levelling networks were founded in 1920–1940. The gravity netwoiks have been measured for several times between 1957 and 1991 according to how the precision of the measuring technique increased. Gravity measurements (scale 1:200000) in Estonian territory, which underlie all the geoid undulation determinations, were carried out in 1949–1959. Reconstruction of geodetic networks with the GPS method began in 1991.