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The 3rd ISPRS Workshop on Dynamic and Multi-Dimensional GIS & the 10th Annual Conference of CPGIS on Geoinformatics
Chen, Jun

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
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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