Combination of space geodetic techniques on the observation level with c5++: Common nuisance parameters and dataweighting

Abstract

The multi-technique space geodetic analysis software c5++ can be used to combine several techniques on the observation level. A variance component estimation (VCE) feature has been implemented recently and is now being tested concerning the impact on the combination of observational data fromdifferent space geodetic techniques. This goes along with studying which nuisance parameters can be estimated as common unknowns at colocated instruments and how offsets between the different techniques need to be considered in order to enable such an estimation strategy. It can be shown that the combination on the observation level is a sophisticated method to merge data from different space geodetic techniques with the goal of improving the quality of the target parameters. Moreover, it can be shown that formal errors of local ties between GPS and VLBI are at least 6 times too small on average.