Refining Geoid And Its Application In Kunming City

GPS (Global Positioning System) has been widely adapted as the main positioning tool nowadays after development for more than 20 years with a new generation updating. The applications of areas and prospects dimension of GPS have exceeded its original purpose. It has become a very important technical method and solution way in almost every field of transportation, communication, metrology, aerologic and so on.Originally, GPS was used as a tool of establishing the precision class of geodetically networks and various of controlling networks .With the development of GPS techniques, great changes have taken in every fields of surveying and mapping. For example, GPS has substituted the traditional works in profile, surveying, deformation monitoring, aero surveying and so on. And a new national geodetic network with GPS technique has been set up in our country. A lot of city control networks also have been set up in many cities.As well known, the static phase relative positioning of GPS can achieve 3-dimension coordinator with centimeter accuracy within a length from kilometers to thousand kilometers. Utilization of GPS to replace the class leveling work will produce great economic and society benefits in Yunnan province in which mountains and undulations cover almost all area . According to the project of CORS of Kunming city, in order to realize GPS heighting an alternative to geometric leveling, we have constructed the platform of digital geoid contour system based on space position (x, y) to realize the translation between geodetic height and leveling height.In this paper, the basic knowledge of GPS, CORS have been introduced briefly, and the theory and methods of refining the local geoid based upon GPS or CORS have been discussed in detail. We use the surveying dataaccumulated for many years in Kunming city to determine the digital geoid contour within the area of over 1000 square kilometers. And it is proved that this contour map achieved application value after vast quantity of tests. With the accumulation of basic surveying data and the increase of scale and the accuracy improvement of geoid contour, the results of the research will play an important role in refining the local geoid and CORS of Kunming city.