Study On Elevation Fitting Method Based On Gravity Field Model-take Mingshang And Other Area For Example

Using GPS to surveying the space position of ground point Is the conventional means of current, the relative positioning precision of the static model can reach 0.1ppm(1 ×10-7) or even higher. But because the elevation it obtained is Geodetic height that base on the WGS-84 reference ellipsoid.It is a pure geometric quantity, cannot be used directly in the project.. How convert the geoid height surveying by GPS into normal high that can be directly applied to the practical engineering must be combined with ground point height anomaly value. This added the measurement cost and time cost. So obtain accuracy height anomaly value is the key to solve the problem EGM2008 is a new generation of gravity field model, using this model to calculate the model-height combined with a certain number of GPS leveling point For elevation fitting is a Hot Issues in Studies.This paper mainly on the aspects of research work:(1) First introduces the relevant knowledge about GPS surveying,significance of GPS height conversion and The current status. Describes the level plane, geoidal surface, reference ellipsoid. And the definition, connotation and relationship between these three vertical high system. Classification discusses several mainstream fitting methods in detail,selected the fitting methods.(2) Then discusses the knowledge of gravity field model and steps of calculating height anomaly by using gravity. Using C# language to compiled a calculator of anomaly height basis on those above.(3) Using GPS data surveying in the yaan mountains area use leveling with the values of abnormal height calculated. And choose three test data from plains, hills, mountains to test. First direct use two methods fitting, then combining gravity field respectively. The results showed the precision of the two methods have been improved after combining gravity field.The precision of the moving-curved surface is slightly higher than quadric surface method, but require more known points. The average error of two methods are in cm after combining gravity field.