The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008 
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Where, ^ max is the maximum in all the ranked correlation 
coefficients and ^ min is the minimum, and k is a constant, in 
this paper, k=0.2. When the correlation coefficient is less than 
threshold, give up the detected matching points, otherwise keep 
these two points. 
4. RESULTS AND ANALYSIS 
Airborne SAR images acquired with different geometric 
parameters have been taken to experimentation. In order to 
examine the stability of different sales of this matching 
algorithm in the article, lots of image pairs covering different 
physiognomy areas have been experimented with SIFT 
matching algorithm. 
In this experimentation, the SIFT algorithm has been used 
directly for image pairs with resemble gray contrast between 
the target image and the reference iamge. But for the SAR 
image pairs acquired at different times and different orbit, 
Canny algorithm has been used to extract edge features before 
the SIFT key points were extracted to match. 
4.1 Results of experimentation: 
a The key points of the target SAR image. 
2007101500442866_FullPaper 
c The result of matching points connected lines(The up-half image is the 
target SAR image, and the down-half image is the DOM SAR image. 
Both sides of lines represent corresponding match points). 
Figure 4 The result of SAR images matching. 
4.2 Results analysis 
The flat land, the terraced field, the mountainous region and the 
residents, each of which include ten groups, have been taken to 
experiment in the article, with different SIFT threshold. If the 
matching error of corresponding feature points is less than 3 
pixels, we consider the matching result right. Matching 
probability can be defined with expressions: 
p = N / M 
where: N-number of right matching points 
M-number of all corresponding points. 
M 
N 
threshold 
p (%) 
flat 
85 
82 
0.77 
96 
terr 
112 
112 
0.6 
100 
moun 
56 
54 
0.82 
96 
resi 
130 
123 
0.6 
94 
All 
383 
371 
97 
b The key points of the DOM reference SAR image. 
Table 1 The results of different physiognomy matching 
From the experimental results we can see that the matching 
probability of terraced field is highest. And the matching