An Approach for Determining the Earth's External Gravity Field by Using Satellite Gravity Data and the Simulation Experiment

Giving a large amount of satellite gravity data,based on spherical harmonic expansion and least-squares estimate principle,an earth's gravity field model EGM could be established,which might not be valid in the region near the earth's surface.Choosing a sphere K_S which includes the whole earth,under the assumption that EGM holds correct in the region outside the sphere K_S,and based on the "fictitious compress recovery" approach,it could be established a new gravity model,properly called NEGM,which is valid in the whole region outside Earth,solving the "downward continuation" problem.A preliminary simulation experiment supports the "fictitious compress recovery" approach and the "downward continuation" approach is given in this paper.