Boundary condition on the geoid surface

In order to determine the function T we focus on the space, bounded by the geoid and infinity and formulate the boundary value problem with respect to 

making use of Bruns theorem we have at points of the geoid 

The latter represents the boundary condition for the function T at the geoid since it is assumed that the anomaly of the gravitational field, Agf is known at each point. 

In order to determine the function T, and, correspondingly, the height N, we have to solve the boundary value problem, that is, to find the function T, which satisfies the following conditions  

At an infinite distance the disturbing potential tends to zero 

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