LEAST-SQUARES COLLOCATION

Least-squares collocation is a mathematical technique for determining the earth's figure and gravitational field by a combination of heterogeneous data of different kinds. The same formulas may be interpreted in very different ways: as the solution of a geophysical inverse problem, as a statistical estimation method combining least-squares adjustment and least-squares prediction, and as an analytical approximation to the earth's potential by means of harmonic functions. The present review article attempts a unified presentation of the subject with emphasis on theory.