Premises for Lithuanian gravity and height systems adoption

Abstract

The gravity height systems adoption is crucial in development of national geodetic reference. Successful solution of this questions guarantees the reliable determination of geopotential heights, usage of modern geodetic space techniques, maintenance of the navigation, geodetic and cartographic works, solution of geodynamic tasks, support the relations between the similar systems of other countries, participation in the international projects. The gravity and height systems should be related with the geocentric geodetic coordinate system. In Lithuania such a system was adopted in 1994 as a Lithuanian Coordinate System (LKS 94). It is consist with European Terrestrial Reference System 1989 (ETRS 89). In 1994 with adoption of LKS 94 the normal gravity field GRS 80 was introduced. It was recommend by the International Association of Geodesy (IAG). To introduce the new gravity system instead of Potsdam system the absolute gravity measurements were carried out in 1994. Such measurements were carried out by Jaakko Makinen (Finish Geodetic Institute). Measurements were performed by ballistic gravimeter JILAg-5 in the points VILNIUS, KLAIPEDA and PANEVEZYS. Absolute gravity measurements were repeated in 2002. The 5 µGal precision of the gravity acceleration was derived. From 1998 to 2001 the National first order gravimetric network was observed. There are 51 gravimetric points in the National first order gravimetric network, evenly distributed in the territory of country. The new investigations of quasigeoid of Lithuanian territory were began in 1994 under collaboration with Working group for geoid determination of Geodetic Commission of Nordic countries. The quasigeoid calculations were performed in 1994, 1996, 1998 and 2004. Accuracy of the quasigeoid of 2-3 cm was achieved. The Baltic Sea height system defined by Kronstadt datum is still in use in Lithuania [...].