The Use of the A10-020 Gravimeter for the Modernization of the Finnish First Order Gravity Network

The A10 is the fi rst absolute gravimeter that allows the rapid determination of gravity with high accuracy in fi eld conditions. In many applications, an absolute gravity survey with the A10 thus becomes highly competitive with traditional relative gravity surveys, in terms of both effi ciency and accuracy. In particular, it is very effi cient in the modernization of gravity control and high precision gravity survey required in modern gravity networks.In 2008 the Institute of Geodesy and Cartography received the outdoor free-fall gravimeter A10 No 020. Time series of gravity taken with it since September 2008 at the Borowa Gora Geodetic-Geophysical Observatory in Poland show that the A10-020 provides high quality measurements in laboratory as well as in fi eld conditions. In 2009–2010 the A10-020 gravimeter was used for the re-measurement of the Finnish First Order Gravity Network. Altogether 51 fi eld sites were occupied, with a repeatability better than 4 μGal. For control, 9 Finnish absolute gravity stations were occupied with the A10-020 altogether 25 times. From preliminary computations, the offset of the A10-020 to the FG5-221 of the Finnish Geodetic Institute was negligible and the RMS difference was 3 μGal. The polarization–stabilized laser and the rubidium frequency standard of the A10-020 were calibrated before and after the surveys at the Finnish National Metrology Institute MIKES to ensure the metrological quality of the measurements.The results obtained confi rm the applicability of the A10 absolute gravimeter to the modernization of gravity control networks.