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SIMULATE APPROACH FOR SEVERAL REMOTE SENSING IMAGES’ POSITIONING 
WITH GPS DATA AND FEW GCPS * 
YAN Qin®, QIU Zhicheng*, CHENG Chunquan?, WANG Yali® 
* Chinese Academy of Surveying and Mapping - yangin@casm.ac.cn 
Liaoning University of Science and Technology- wang_violin@sohu.com 
KEY WORDS: Photogrammetry, Remote Sensing, GPS, Triangulation, Orientation, Accuracy 
ABSTRACT: 
With satellites’ position, the main factors affecting image's positioning accuracy are image's attitudes. Supposing that satellites' 
position can be determined by GPS, images' positioning without GCP can be implemented upon the characteristic of images overlap. 
The paper designs an approach for images’ positioning with GPS data and no GCP through combined adjustment and proves that the 
approach is correct with simulated data. Furthermore, the precision of computed attitudes and targets’ position is analysed. 
1. FOREWORD 
The orientation precision of the remote sensing image mainly 
depends on the exterior orientation parameters of the satellite 
with no GCP. In general the satellites’ position error usually 
leaded to the horizontal shifting effect, and the precision of the 
angular parameters are the crucial factors of the targets’ 
positioning. At present some satellites have loaded GPS system 
which can real-time records the satellite’s position. Furthermore 
the spatial position of the satellite can be measured and 
controlled more and more accurate because of the improvement 
of the GPS precision. As a result, how to eliminate the influence 
of the attitude error is the key question of the targets’ 
positioning. 
Supposing there is a film-recovery photographic satellite, and 
the photographic scale is 1:64000, the range of one scene image 
on ground is 10km X 10km. And the precision of the GPS is 
good enough, so the data GPS acquired can be regarded as the 
photographic station, i.e. the line exterior orientation parameters 
of the satellite. Under this condition, the tie points of two or 
more images were used to correct the attitude parameters of 
each image and the technology of image targets' positioning 
with few or even no GCP was brought forward. And the targets’ 
positioning error on conditions of varying topography and 
overlap measure was analysed with computer simulation 
technology. 
In this paper, the multi-image combined adjustment principle 
which based on GPS surveyed satellite position and the tie 
points was introduced. The error equation of combined 
adjustment was derived. And the satellite image targets’ 
positioning technology with few or even no GCP was set up. At 
the same time a series of experiments with simulated data were 
done to verify the exactness of this method. Further analysis 
was carried on the influence of targets’ positioning error caused 
by image’s measured error. 
  
2. PRINCIPLE 
According to the principle of photogrammetry, image's 
orientation needs six exterior orientation parameters, i.e. 3 
S, S2 
  
  
  
Figure 1. tie point 
spatial coordinate values (Xs,Ys,Zs ) and 3 attitude values 
(p,c,K). Firstly, supposing the satellite's position can be 
measured by GPS very accurately. So we will emphasis on how 
to measure the 3 attitude values precisely. 
See figure 1, P,, P, are two adjacent images, the shadow is the 
area where P, overlaps P», S; and S; are photographic stations. 
S,a and S,b intersect at one point P under the ideal situation. 
Due to the error of the attitude, a and b were projected at A and 
B separately. The algorithm we put forward is to project a and b 
at point P correctly through correcting the attitudes of the image 
while keeping S, and S; immovability. 
According to the principle of photogrammetry, some relative 
values (or absolute values) of the attitude of one stereopair can 
be calculated using the relative orientation algorithm. To do 
relative orientation of single stereopair, the relationship 
between photo base and tie points can be describe by the 
* Beijing remote sensing information research institute has researched a project named satellite ground application system image 
processing subsystem. Content of this paper is a part of this project.