Jiang Zhiheng Research Institut of Surveying and Mapping
Based on the studies and experiments available on GPS levelling, the auther discussed various theories and methods, by which, the orthometric height can be determined by the combination of GPS technique and gravimetrie solution without using traditional precise levelling. This paper is divided into three parts: the first part is mainly about the idea of GPS levelling and its geometric method, the second part deals with gravimetric method, the third part introduces some results of GPS levelling experiments. It is concluded that 5～10ppm, the relative accuracy, can be reached in flat area by geometric means, the same accuracy can be got with gravity data in mountainous area, and by acombined adjustment, using the two parts of observations mentioned above a better result with the accuracy of 2～3ppm could be expected. It is possible that some jobs done by traditional precise levelling would be then taken over by GPS leveuing in the coming future in china.