Why absolute gravity data is of interest

The information provided by absolute gravimetry is particularly interesting for monitoring the vertical movements of tide gauges. First, the accuracy of the results obtained for land movement is similar to that of the best spatial positioning techniques (Williams et al. 2001, Zerbini et al. 2001). Secondly, it provides information that is complementary, derived from physics, whereas the GPS information is geometric. This synergy is useful for performing comparative studies and provides a better understanding of the nature of the movements observed, particularly the separation of the effects of mass redistribution from the effects of changes in elevation. This is all the more interesting since the correction of the vertical movement of tide gauges poses a problem that has still not been resolved satisfactorily; the GPS calculations are complex and the solutions are not immune to bias due to calculation artefacts.