Research On Several Problems Of Refining The Local Geoid

Geiod or quasi-geoid is a height datum for acquiring geospatial information. If the geoid or quasi-geoid model is given, GPS can be used directly to determine orthometric height or normal height, which can take the place of the traditional geometric leveling and make the seperation mode of plane control network and elevation control network in traditional geodesy become a history. Therefore geoid refining is one of important missions for the establishment of the height datum in a country or a region.In this thesis, the basic theory and methods for the determination of geoid is introduced. Then the main error sources for the determination of geoid are analyzed and the error transmission formulas are given. Classifying topography into plain area, hill area, mountain area and high mountain area, contributions of terrain mass including direct effect and indirect effect to geoid refining in different areas are compared using some practical examples. Finally, taking a plain area and a hill area as examples, several geoid models are calculated using different data combinations. By comparing these models, the roles of distribution of GPS/leveling points, terrain data and gravity data in local geoid refining are investigated.