ISPRS, Vol.34, Part 2W2, “Dynamic and Multi-Dimensional GIS”, Bangkok, May 23-25, 2001 
The main points of this proposal are, 
1) ,With the help of modem geodesy techniques, GPS, 
to determine the geoid of Yunnan province of China and 
analyze the accuracy of geoid achieved by this method. 
2) ,Based on the achievements, to establish model for 
the application of surveying and mapping in Yunnan province. 
With the development of satellite geodesy, esspecially 
the technique of GPS, it has been possible to determine the 
distance between two points with an accuracy of 
0.1-0.01 ppm,and the height with accuracy of 10cm up to now. 
We will deal with the vertical control system mainly and 
focused on the refining the geoidal undulation with GPS 
techniques combining the ranging trigonometric leveling with 
topographic data. This is because of the advantages of GPS 
techniques and the mountainousness of the valley area. 
There are some methods to determine the geoid 
undulation. For example, GPS leveling, use of potential 
coefficient models, astronometric leveling, etc. Gravity in a 
large area must be measured or long leveling road must be 
taken in this methods. These works are very expensive and 
time consuming. 
In view of mountainous of Yunnan province, in order to 
meet the need of refining the geoid in the area we must 
introduce a method which is realized quickly and economically 
based on the existed instruments, GPS receivers and 
theodolites and so on. 
The height anomaly determined by GPS and ranging 
Hag, - H, = (1) 
trigonometric leveling is 
here, £ is the height anomaly of a point on the ground, Hagi is 
the geodetic height determined by GPS and Hi is the 
normal-orthometric height determined by ranging trigonometric 
leveling thus, by surveying some of observations Hagi and Hi 
in the area, we can get the character value of the local geoid 
with a contour expressing. 
Considering the mountainous area of Yunnan 
province and the difference between N and H, ,the second 
order of perpendicular gradient of gravity anomaly in terms of 
4-N = ——.H + — .H 2 (2) 
r dh 
topographic data must be taken into account i.e., 
Traditionally the difference between £ and N is considered 
within the first order in topographic correction. But the second 
order of the £ -N must be considered in an area of 
mountainousness to make use of topographic correction. The 
(d delta G/dh) is the spatial perpendicular gradient of gravity 
anomaly which is the key factor to make the second order 
correction with topographic data. 
By applying these methods, we can obtain a better local 
geoid in Yunnan province of China and the refinement of the 
geoid can be realized quickly and economiclly. Of course, 
much work must be done before the realization of this 
proposal. 
4. Summary and suggestions 
With the exploration of western China, In order to 
quicken the speed of economic development of Yunnan 
province, Yunnan government has decided to develop the 
economic and trade communication and science and 
technology cooperation with Southeastern Asian countries. 
According to The Suggestion of the Plan and Social 
Development of Yunnan Province which was formulated by the 
Yunnan Government July 2000,the policy to open to the 
outside world is focused on the cooperation in science and 
technology with neighbor countries, and it has been 
determined that the exploitation and utilization of natural 
resources in Yunnan province will greatly depended on the 
realization of project of the Exploitation of River Lanchang. 
From the point of view, how to make full use of advanced 
technologies, GPS and GIS in the development of the 
economic and society in River Lanchang basin will be a 
beneficial target. We have discussed these two sides in this 
paper and we would like to accept helps and suggestions from 
scholars and experts from the entire world. 
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