Study And Application Of The Local Geoid Refinement

Refinement of local geoid is one of the importing issue of the geodesy, and same time, it also is an import basic surveying project. Along with a large numbers of the earth gravity field model, gravity data in the earth surface, GPS/leveling data, digital terrain model and other related data, the refinement of centimeter order geoid has been provided with necessary conditions. The purpose of refining high accuracy local geoid, one is to develop physical geodesy, the other is to solve the problem that replace the low accuracy leveling by GPS surveying. Thus in using GPS determines the plane position while also determines normal height to cut the field work and the production cost and has important scientific significance and economic benefits.At first the article describes the national geodetic reference systems and the relationship of each other, researches principle of several kind methods of geoid refinement systematically, mainly include geometric leveling method, gravimetric method and combination method. Then in view of the precision demand of centimeter order quasi-geoid, the data assimilation and precision assess in quasi-geoid refinement were systematically analyzed. Analyze the influence from all kinds of error and the methods to control them. The error mainly includes GPS/leveling measurement and the gravity data such as potential coefficient error, terrain correction error and gravity anomaly error.Based on the above theory the article chooses combination method (Molodensky theory) using the remove-restore technique to compute remainder geoid. We supplied available data which come from the Whole World Gravity Field Model, the gravity data in Jiaozhou, the GPS/leveling data in Jiaozhou and the digital terrain model. We determined the local gravity geoid by fitting the remainder geoid with height anomaly which was computed by the Whole World Gravity Field Model. Then the local gravity geoid is combined with geometric geoid obtained from GPS leveling and systematically corrected by the least square collocation method. Then we gained the result of this regional geoid and the information about its precision.