Global Geoid Determination

This chapter discusses the methods used to determine a global representation of the Earth’s gravitational potential from a combination of satellite and terrestrial data. Knowledge of the gravity field is important for many different applications including the following: the calibration of inertial navigation equipment; the computation of geoid undulations (or height anomalies) or deflections of the vertical; and the determination of geophysical phenomena. Recognizing that the orbits of satellites depend, in part, on the Earth’s gravitational field, it is possible to analyze the motion of satellites about the Earth to infer information on the Earth’s gravitational potential. A global geoid undulation map based on the OSU91A model, taken only to degree 50. Although there is significant information above degree 50 in this model, the resultant geoid undulation changes would be difficult to see on a map of this scale. The weighting of the various data types in the development of the potential coefficient models is a delicate task.