Xu Hou-ze

Earth gravity field recovered from CHAMP science orbit and accelerometer data

The earth gravity field model CDS01S of degree and order 36 has been recovered from the post processed Science Orbits and on-board accelerometer data of GFZs CHAMP satellite. The model resolves the geoid with an accuracy of better than 4 cm at a resolution of 700 km half-wavelength. By using the degree difference variances of geopotential coefficients to compare the model CDS01S with EIGEN3P, EIGEN1S and EGM96, the result indicates that the coefficients of CDS01S are most close to those of EIGEN3P. The result of the comparison between the accuracies of geopotential coefficients in the above models, indicates that the accuracy of coefficients in CDS01S is higher than that in EGM96. The geoid undulations of CDS01S and GGM01C up to 30 degrees are calculated and the standard deviation is 4. 7 cm between them.

Quasi-Geoid Near Xisha Islands by the Geo-Potential Propagating Technique

Height datum is an important part of national geodetic network. Establishment of a unified national land and sea elevation benchmarks and implementation of height datum connection between the Chinese mainland and offshore islands are issues that need to be resolved in geomatics and marine sciences. Derived from basic definition of elevation datum and relationship between geo-potential and normal height, the scientific theory and algorithm for transferring height datum from mainland to islands with geo-potential are elaborated. The accuracy of geo-potential difference is discussed using a numerical analysis method. We also give criteria to choose virtual leveling routines and algorithm to give optimized results. One experiment in the China seas, among 26 tidal gauge stations in the sea coast of the mainland with known normal height, has confirmed the reliability and accuracy of the method developed in this paper. Further optimizations for improving accuracy of island elevation are also introduced. Distribution of quasi-geoid near Xisha Islands is also given with this method.