Quasi-geoid

Fig. 2.10. Telluroid, quasi-geoid, and reference ellipsoid (after Grushinsky).

Later we will assume that the difference Wq— Uq is equal to zero. In this equation N is the height of the quasi-geoid, BiB. It also defines an excess of the level surface of the potential W, passing through the point A of the physical surface of the earth over corresponding level surface of the normal potential passing through the point Ai. Let us represent Equation (2.293) in the form... 

The importance of Equation (2.294) is that it establishes a relationship between the height anomaly, N, and the disturbing potential T at the same point of the earth. By definition, we have for the normal height h of the point A over a quasi-geoid... 

Thus, the determination of heights of the quasi-geoid N requires knowledge of the disturbing potential T on the physical surface of the earth. As in the case of the Stokes problem, in order to calculate N we have to determine the disturbing potential, which obeys some boundary condition on the physical surface of the earth instead of the surface of a geoid. This is the main advantage of a new approach. 

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