Elaboration of equipotential surfaces of planets using biorthogonal expansions
Purpose. Using known and fixed Earth potential, presented asthe biorthogonal expansion, to culculate the geoid surface, which describes the actual shape of the planet. The external gravitational field is generally described by the series of spherical functions. Since the geoid is determined with the help of such functions, a question arises converning the identity to define the shape, moreover its several points does not belong to the region of convergence. Methodology and results.