The Application Of Grey Theory On Geoid Refining

Geoid 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 separation 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. Whereas, the regional geoid refining or quasi-geoid refining requires a great deal of survey data. It is a great difficult problem to get the anticipative effection to boffin on how to do the science research with limited data.At first, this paper describes basic theory and principles of precise determination of local geoid, then discusses and makes a research about geometrical method and gravity method. and makes use of gravity model to get important gravity field parameters, such as height anomaly, gravity anomaly, deflection of the vertical, and realize 3D visualization of gravity model. When using of combination method to get Geoid, this paper adopts Grey model to simulate residual sequence of height anomaly. According to theory of grey system, the information of known system is called white boxes, unknown is called black box. The grey system is that some of the information is known but others is unknown. The grey system theory is based on limited data. It establishes model by modeling data which through accumulating generation. It gets the system operating behavior and developing disciplinary by generate part of known information in order to know the real world. In the past, the selection of the background value is by mean of generation to modeling, it is not sufficient to show the contribution of all kinds of modeling data. This paper exploits the range of the background value, propose a method by adding certain weight to get the background value under certain condition, use the combination of weighted model and the weighted residual model to simulate height anomaly in the gray modeling. It is substantiated by theoretic analyses and example test that the given solution to get normal height in this paper can meet the needs of the general surveying project, which can realize unification of GPS position technical on plane surveying and leveling surveying. It greatly improves labor productivity and efficiency, and it has a great practical significance on building geographical space frame of the Digital China or Digital City.