The method of free-positioned point masses — geoid studies on the Gulf of Bothnia

Gravity data inversion methods using spatial source distributions are frequently investigated and applied in Geodesy. Nearly all of them construct a fixed geometry for the sources. It was shown that this is not at all necessary. We give an approach to the problem of geoid determination based on free-positioned point masses. The algorithm available is extended and refined in order to make it applicable to more ill-designed and complex problems than addressed so far. We introduce concepts to handle different data accuracies, non-uniform data coverages, and different data types. The Gulf of Bothnia serves as an area of investigation. We determine a pure gravimetric geoid solution as well as a combined solution based on gravimetric and altimetric data. The problem of gross error detection in the altimetry is treated. The prediction accuracies obtained prove the method to be suitable for such a problem.