The Status of the Hungarian Gravimetric Network - Absolute measurements until 2021

The Hungarian Gravimetric Network (MGH) has been existing since the early 1950s, it was created and maintained, developed by the Eötvös Lorand Geophysical Institute of the Hungarian State (MÁELGI) and its successors. Presently, as the actual successor of Mining and Geological Survey of Hungary, MGH is handled by the Supervisory Authority of Regulatory Affairs (SZTFH, Budapest, Hungary).

The network went through modernization; following the earlier ‘Vienna’ and ‘Potsdam’ reference systems it has been absolute-based, since the late 1980s.  The latest adjustment of the network was performed in 2013, where the mean error was ±0.01386 mGal.

The MGH recently contains 25 absolute (0th order) stations, as well as 435 1st and 2nd order base points. In order to improve the reliability and accuracy of the network, the absolute value of gravity acceleration is redetermined in every 7-10 years on ‘normal’ absolute stations, furthermore in every 2-7 years on the national gravimetric main base point (in the Budapest-Mátyáshegy Gravity and Geodynamical Observatory). The absolute (0^th order) stations of the network form the ‘national gravity etalon’ in Hungary, where the term is the actualization of absolute g values within 10 years on every station. In Hungary 82 absolute measurements have been carried out since 1978. Hungary doesn’t possess absolute gravimeter, the measurements are ordered (ab. 3 stations in every year). From 2007 until now, the absolute measurements in Hungary are carried out by the VÚGTK (Research Institute of Geodesy, Topography and Cartography, v.v.i.), Czech Republik.

Before (or within a short time interval around) the absolute measurements, vertical gravity gradient (VG) values are determined on the stations by LCR-G relative gravity meters, using a 3-level arrangement and at least 6 series of measurements of 2-3 instruments.

In 2 observatories operated by the SZTFH, in Budapest and Tihany, changes of gravity field are continuously monitored by relative LCR-G gravity meters.

In the 1990s a partial network of MGH consisting of 45 adequately selected 0^th, 1^st and some 2^nd order base points joined the Unified European Gravimetric Network (UEGN). This partial network was then connected to corresponding base points of Austrian and Slovakian networks, based on cooperation with BEV (Federal Office of Metrology and Surveying, Austria) and GKÚ (Geodetic and Cartographic Institute Bratislava, Slovakia).

Recent questions, open problems of the network maintenance will be also discussed.