The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008 
In order to satisfying adjustment condition of ortho-rectification 
coefficients’ calculation, the total number of GCPs and Pass 
Points is more than 6 in each image. In order to satisfying 
multi-photo combined adjustment condition, n is bigger than 
t. 
3.1 Experiment Data 
Experiment One: Two flight strips, four images, the numbers 
of strips are 1321, 1309. nine GCPs and ten Pass Points are 
used. The number of redundant observation is two. 
2.3 Solution Process 
2.3.1 Initial Value Solution: Initial value is divided into two 
parts as follows. One is ground coordinates of pass point 
(X 0 , Y 0 , Z 0 ) , the other is ortho-rectification coefficients of 
each image a Qi >V 
(l)Initial value of ground coordinates of pass points 
Experiment Two: three flight strips, eleven images, the 
numbers of strips are 0629, 0707, 0831. nine GCPs and thirty 
Pass Points are used. The number of redundant observation is 
six. 
Fig.l is the distribution of images, GCPs( A ) and Pass 
Points( • ) in Experiment One. Fig.2 is the distribution of 
images, GCPs and Pass Points in Experiment Two. 
Selecting appropriate corresponding image points as tie points 
in overlap section of adjoining images. Simple or quadric 
polynomial transform models are built between image 
coordinates of corresponding image points, then transform 
coefficients are gotten from top to bottom, from left to right, 
based on the image of the top left comer, and then all image 
coordinates are unified as the same coordinates system of the 
image of the top left comer. According to horizontal 
coordinates of GCPs (X, Y) and corresponding image 
coordinates (x, jf) , quadric polynomial transform model is 
built, and then transform coefficients are worked out by only 6 
GCPs or more. We can get initial value of horizontal 
coordinates of pass points (X 0 , Yq ) through transform 
coefficients. 
According to initial value of horizontal coordinates of pass 
points (X q ,Yq) , we can get initial value of pass point 
elevation Z Q . 
(2)Initial value of ortho-rectification coefficient of each 
image 
Put initial value of ground coordinates of pass points 
(X 0 ,Y 0 ,Z 0 ) and ground coordinates of GCPs (X,Y,Z) 
into multi-photo combined adjustment model, initial value of 
ortho-rectification coefficients of each image ( a 0i , b Qi ) is 
obtained. 
2.3.2 Solution of Ground Coordinates of Pass Points and 
Ortho-rectification Coefficients of Each Image: According to 
adjustment model, corrected value of ortho-rectification 
coefficients of each image dci i ,db j and corrected value of 
ground coordinates of pass points (dX ,dY) are gotten. The 
two kinds of corrected values are computed alternately and 
iteratively, until (dX ,dY) is less than the setting threshold 
value. 3 
1321— 
1309- 
-1321 -1309 
^L01 
^02 
^01 
Fig.l Distribution of GCPs and Pass Points 
3.2 Results and Analysis 
3.2.1 Experiment One: Table 1 is the combined adjustment 
accuracy of the four images. The Pass Points are same in Image 
1321-01 and 1309-40, Image 1321-08 and 1309-33. So the 
accuracy of Pass Points is same. 
3.2.2 Experiment Two: Table 2 is the combined adjustment 
accuracy of the eleven images. 
3. EXPERIMENT RESULTS 
According to this model, program has been designed. Two 
experiments have been done on lm resolution airborne SAR 
images of study site in Chengdu. 
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