The regional geopotential model to degree and order 720 in China

Abstract

The spherical harmonic expansion is a powerful method to describe local and global gravity field in the frequency domain. In principle, the resolution and precision of gravity field expressed by the spherical harmonic model are proportional to the degree and order of model expressed, for example, to degree 720 that has a resolution about 28 km. For this reason a higher degree geopotential model is of the advantage for us. It is possible to develop the regional model to degree and order 720 although that seems more difficult for global model in terms of the resolution and precision of gravity data over global area. On the basis of the tailored method, we have developed the regional higher resolution geopotential model IGG97LB to degree and order 720 suitable to the mainland of China. The gravity anomalies computed from the new model can achieve the mean square error of +/-8.8 mGal. The geoid undulations from model have a mean square error +/-0.67 m compared with height anomalies derived from GPS and levelling in the research area. The mean square errors of gravity anomalies and geoid undulations are the same as that computed from reference model EGM96 in global area without China. A clear linear relation between gravity anomalies and geoid undulations on short wavelength parts both computed from the new model has been found in the research area.