New techniques for the combination of heterogenous data when determining the Earth's gravity field

A concept for the solution of data combination is developed in which the idea of robust collocation, based on a random effects model, is generalized. With the multi-hom BLUP (Best homogeneously Linear Unbiased Prediction) and mixed BLUP predictors, two approaches are presented where the influence of possible systematic errors in the data set, being interpreted as stochastic prior information, can be reduced. In order to estimate the different combination solutions a statistical test strategy was developed, which involved identity and compatibility tests. These techniques were numerically tested by means of an expansion of the Earth's gravitational potential in spherical harmonics based on terrestrial gravity data and satellite orbit information. Due to the robustification very homogenous combination solutions could be obtained using the predictors; they turn out to be superior when compared with the traditional approaches.