Comparison of the Regional Geoid Undulations Determinated by Geopotential Models

The analysis of the degree variances of the geopotential models(EGM2008、EGM96、 GGM02 et al)were presented.In order to generating the accuracies of the long-medium and short medium components of the models,the geoid undulations computed by the models up to degree 120 and 360 were evaluated combing with the GPS leveling data in the research area.Considering the effect of the topography on the geoid and the deficiency of the observed gravity data,the research area was divided into the flat part and the mountainous part roughly,and then the model values on the reference points were compared in each part.Finally a least square fitting was used to correct and modify the model values.The results were showed as follows,EGM2008 was the most accurate model with respect to the potential coefficients.In the fist 120 degree the accuracy of the values from the model EGM2008 was quite identical with those from GGM02C_EGM96,as well as EGM2008 was the best in the degree of 360.The standard deviation in the mountainous areas was larger than that in the flat areas obviously and EGM2008 was also the best model in two topographic conditions.Compared to the model values the fitting values were improved,but the accuracy was not as good as that in flat part.