As already pointed out in our Introduction, data describing the gravity field of the Earth are an essential source of information used in all geophysical interpretations. Seismological, magnetic, electrical, and heat flow data are the alternative sources. Each type of data has its advantages and disadvantages. One could argue that the chief advantage of gravity field related data is that they can be collected with almost any required sampling density over continental areas. However, the terrestrial data material needed for the determination of the gravitational potential via an oblique boundary value (problem) formulation is simply not available homogeneously on a global basis and will not be for the foreseeable future. There are large gaps over ocean areas, but also over land. Consequently, the oblique derivative problems discussed in Chapter 3 mainly are of limited importance. In practice, the problem can only be overcome by introducing satellite techniques. Only by using satellite measurements can we expect essential progress in the Earth’s gravity field determination for global modelling.
KeywordsPseudodifferential Operator Fundamental System Proof Mass Satellite Problem Oblique Derivative Problem
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