311 
possesses higher texture and special direction, then it benefits 
the recognition of this kind of land type. 
Figure 1 Contrast images through Gamma filter 
4. CHANGE INFORMATION DETECTION 
Automatic recognition and change information extraction are 
the hot topic on the research of remote sensing. In the related 
literature, there are many kinds of research methods such as 
image interpolation, ratio method, PCA, spectrum feature 
variance, K-T etc. 161 . Different monitoring contents possess 
different methods. For example, according to urban extended 
area, fusion technology, difference value method, false color 
composite etc. are adopted 171 . The key contents of land use 
dynamic monitoring is to find the boundary, contour and 
attribution of land use types change in the new and old times. 
The methods on change information recognition depart into 
computer automatically recognition and artificial interpretation 
on the processing pattern. As the domain of research, it’s 
independent between automatically recognition and artificial 
interpretation. But in practice, the relation between them is very 
close. Automatically recognition method could improve the 
efficient of searching change polygon, and artificial 
interpretation method could guarantee the accuracy of searching 
change and improve the accuracy ratio. 
4.1 Change Information Detection Based on Fusion 
Technology 
Change information detection based on fusion technology is to 
find spectral feature variance through merged image in different 
times. Change area on spectral feature of merged image could 
detect change. In the test, firstly, SAR data and multispectral 
image are merged into new fusion image. And then inconsistent 
area of spectral feature is searched in the fusion image. Finally, 
whether change or not is confirmed through comparing images 
of two dates. In figure 2, a is the multispectral image in 2002, b 
is the SAR data in 2004, and c is the fusion image in which 
bright green color denotes that image spectrum changed, 
namely new-added construction. 
Figure 2 construction land change detection 
image based on fusion technology 
4.2 False Color Composite Based on PCA 
False color composite is to put the same band from different (2 
or 3) times into red, green and blue image processing panel 
separately. And the composite image could denote high bright 
change information. In the test, PCA and false color composite 
are integrated into use. Firstly, multispectral image carries on 
PCA,. the first principal component extracted and SAR image 
are composited. SAR image is put into red band.Images through 
PCA are put into green and blue band separately. At last, it 
produced a new color image. 
In figure 3, a is the multispectral image in 2002, b is the SAR 
data in 2004, and c is the composite image in which red color 
area is construction change information. 
Figure 3 construction land change detection 
image based on PCA and false color composite 
4.3 Difference value method 
Difference value operation is applied in the two registrated 
images in different times. So the new difference value image 
denotes the spectral change between two images. Difference 
value image focuses on mostly change information and removes 
the same parts 181 . 
In the practical application, change detection method is selected 
according to the type of data source. The different change 
information stands out according to the characteristic of each 
method; moreover special change may be unfit for this kind of 
arithmetic. So if only one method is selected as the detection 
basis, it maybe results in omitting the change information. In 
order to reduce the omitting of change information, more than 
two kinds of methods selected may be better. And it’s 
supplement each other to composite different change detection 
methods. Fig d and e in fig 3 is the different change results with 
different change detection methods. Fig d denotes the 
consistency between the tone of new-added residential area and 
the tone of surrounding residential area, but if only this change 
detection map would omit this type of change polygon. 
However, fig e denotes the change of the polygon. So two kinds 
of methods are integrated into use, and then reduce the omitting. 
5. CHANGE INFORMATION EXTRACTION 
ANALYSIS 
Whether of change information detection methods is selected, 
and the purpose is to extract change information. It comprises