Validation of Satellite Gravity Field Models by Regional Terrestrial Data Sets

Within the next few years, improved high-resolution global gravity field models are anticipated from the GOCE mission. The expected accuracies are about 1–2 cm in terms of geoid undulations and 1 mGal for gravity, both at a resolution of about 100 km. Then, from a combination of the GOCE based global gravity field models (expected to be available up to spherical harmonic degree and order 250) with regional terrestrial data sets, an accuracy of about 1 cm is expected for the complete geoid spectrum. In this context, accurate and independent terrestrial data sets are essential for the combination process as well as for the validation of the results. Therefore, a regional validation and combination experiment was carried out in Germany as a work package within the framework of the GOCE-GRAND II project. The main goals of this undertaking were the preparation of high-quality validated terrestrial data sets, which can be used for a future external validation of the GOCE products as well as for the combination with the GOCE data. Within extensive measurement campaigns, significant efforts were put into absolute gravity observations with an A-10 instrument at field stations as spot-checks of the existing data base, and into astronomically determined vertical deflections using the digital transportable zenith camera system TZK2-D. In this contribution, gravity data, GPS and levelling control points, astrogeodetic vertical deflections and gravimetric quasigeoid models are utilized as terrestrial data sets for internal cross-validations as well as for the external validation of global satellite gravity field models.