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2009-12-08 – SEMINAR by Jonas Ågren: Absolute Gravimetry to determine the postglacial rebound in Fennoscandia

8 December, 2009 (16:00 GMT), 5 Merrion Square, Dublin 2.

Speaker: Jonas Ågren, Lantmäteriet, Geodetic Research Division, Sweden.
Title: Absolute Gravimetry to determine the postglacial rebound in Fennoscandia.

Abstract:

It is the responsibility of the geodetic resarch division at Lantmäteriet to develop and maintain the Swedish geodetic reference systems, which are used for surveying and mapping. Recently Sweden introduced the new modern three-dimensional system SWEREF 99 and the new height system RH 2000. It is estimated that the total cost for the practical users to change to these systems is around 25 million Euro. It is consequently important that the accuracy of the new systems does not degrade over time. Intraplate deformations like the postglacial rebound therefore need to be modelled with as high accuracy as possible. As a part of the efforts to improve the quality of future land uplift models (GIAmodels) Lantmäteriet collects different types of observations, usually in collaboration with the other Nordic countries. One important type is repeated absolute gravity measurements. It is the main purpose of this talk to present the Nordic Absolute Gravity Project, especially the Swedish contribution to
this project. Another aim is to investigate numerically the effects of non tidal sea level variations in the Baltic Sea on gravity. It is shown that the total non tidal gravity effect is significant, easily reaching values of 2-3 microGal for stations with high elevation close to the coast. It is therefore important that the absolute gravity observations are corrected for these effects in the future.