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Mapping without the sun
Zhang, Jixian

possesses higher texture and special direction, then it benefits
the recognition of this kind of land type.
Figure 1 Contrast images through Gamma filter
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
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.
Whether of change information detection methods is selected,
and the purpose is to extract change information. It comprises