A Testbed for Airborne Inertial Geodesy: Terrestrial Gravimetry Experiment by INS/GPS

Gravimetry from a combination of INS and GPS measurements is well known and investigated since several years. The main application is in the field of airborne gravimetry, where the results can be used to fill the spectral gap between spaceborne gravity field data (from satellite missions such as CHAMP, GRACE or GOCE) and terrestrial data available from regional or continental gravity networks. Our intention is to study in detail the behaviour of such an INS/GPS instrumentation, the applied signal processing techniques and the derived signal. As a first step, a ground based INS/GPS survey was carried out, where the results can directly be compared to terrestrial data without any need of downward continuation. Also the spatial resolution of such a terrestrial experiment is higher, than for airborne gravimetry, due to a much smaller vehicle velocity. The experiment was carried out by car in a test area in the Bavarian Alps. This area was set up several years ago in order to investigate in detail the gravity field in mountainous regions. Since about 10 years a huge number of gravity values was determined, leading to a point density of about 2.5 points/km. Therefore the region was chosen as testbed for our inertial measurement campaign. The first results presented in this paper show, that our navigation grade inertial measurement unit is well suited to derive gravity values with an accuracy of a few mGal. Still, problems with the GPS visibility and the accuracy of the kinematic accelerations are an obstacle for precise determination of gravity disturbances along the trajectory.