Installation of absolute gravimetric stations
In the German Alps, four absolute gravity stations were established by IfE in 2004. The objectives were:
- Installation of a relative gravimetry calibration line with large gravity differences and short transportation ways between the stations; thus a basis is created, in order to be able to use modern field gravimeters for most precise monitoring tasks in seismic and geodynamically active areas;
- Establishment of a long-term reference to monitor gravity changes due to melting of the alpine glaciers and due to geodynamic changes of the Alps.
The heights of the four absolute points were determined by using GPS in combination with geometrical and trigonometric levelling. The long GPS ties between the stations were measured over three days continuously. With the large number of gravity measurements at each station (2000 to 3000 free fall experiments along a laser beam in high vacuum) the obtained accuracy is ±10 to 40 nm/s² for the station results.