Joint gravimetric and geometric survey of geophysical signals - Feasibility study for the TERENO alpine and prealpine Ammer observatory

Kurzfassung

This master’s thesis deals with a feasibility study for a joint gravimetric and geometric survey of geophysical signals. As test area the TERENO alpine and prealpine Ammer observatory is chosen since this initiative is associated with the installation of instruments for measuring meteorological and hydrological quantities. Gravimetric and geometric signals, which occur in the TERENO area, are estimated from available measured data. At the beginning the theory of signals from solid Earth tide, ocean loading, pole tides, atmosphere and hydrology is outlined. The magnitudes of the expected signals are compared. It is distinguished between direct effects due to Newtonian attraction and indirect effects due to mass loading variations. Therefore the basics of mass loading calculations using Green’s functions are described. Hydrologic and atmospheric signals shall be measured with different measurement techniques; the other mentioned effects can be reduced by models. As gravimetric measurement techniques different gravimeter types and the GRACE mission are introduced. For measuring geometric signals spaceborne SAR (TerraSAR-X and TanDEM-X) and GNSS are presented. The Scintrex CG-3M gravimeter, owned by the IAPG, was used for test measurements. First it was utilized as stationary instrument to investigate the influence of air pressure and drift. A field campaign was performed as a second experiment.. It was measured above a storm water basin to simulate a groundwater change. A further test measurement was performed to validate ranges and azimuths measured in SAR-images against ranges and azimuths derived from corner reflector coordinates, determined by GPS measurements. This method is used to evaluate the accuracy level of absolute SAR measurements. Starting from the estimated signals and the experiences from the test measurements, different approaches are introduced for measuring atmospheric and hydrological signals using gravimetric and geometric techniques. For every approach the measurement configuration and the required instrumentation is described.