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Mapping without the sun
Zhang, Jixian

most in comparison with other fusion method and its entropy is
less than fusion images based on PCA and wavelet. The
standard deviation of fusion image based on PCA is closer the
standard deviation of original multi-spectral image TM ,which
indicates this method has less distortion of spectral
characteristics .
In the view of entropy, the entropy of wavelet-based fusion
image is greater than these of other methods. So the information
contained in fusion image based on wavelet is greater, which is
to say, the quality is better than these of other three methods.
The fusion image based on Brovey is the least, and its mean is
small, so the image based on Brovey has less information and
the whole image is darker than images of other methods.
The correlation coefficient reflects the redundancy degree of
images. According the table 1,we know the original image
contains a plenty of redundant information and the correlation
coefficient of fused image based on wavelet integrated PC is the
least, which indicates that this method has less redundant
information than other method.
Figure3 original image: TM (right) and SAR (left)
Figure 4 the fused images based on (a) Brovey transform, (b)
PCA, (c) IHS and (d) wavelet integrated PC
According to previous statistics and analysis, we can draw a
conclusion that the fusion method based on wavelet integrated
PC is efficient for merging low resolution multi-spectral TM
image and high resolution SAR image. Though other fusion
methods have advantage in some ways, the fused image based
on wavelet integrated PC is optimal when considering all
aspects. This method integrates the advantages of wavelet and
PC and the method based on wavelet has been applied to fuse
SPOT panchromatic and multi-spectral images successfully.
In this paper, a new fusion method based on discrete 2-band
wavelet was presented and several fusion methods are used to
merge the multi-spectral TM and high resolution SAR image.
Several parameter including mean, standard deviation,
correlation coefficient and entropy were adopted to appraise the
fusion products. At last the result of experiment proves that the
fusion method based on wavelet integrated is more efficient for
fusing the TM and SAR data in comparison with other fusion
methods. First the redundancy is little and entropy is large.
Secondly the fusion image preserves better the original image
Though the fusion result is better, this method still has some
question due to the limitation of time and data, this paper did
not experimented, only to discuss from the theory. In general
biorthogonal (and symmetrical) wavelets are more appropriate
than orthogonal wavelets for image processing applications
(Strang et al, 1997). Biorthogonal wavelets are ideal for image
processing applications because of their symmetry and perfect
reconstruction properties. So the fusion based on biorthogonal
wavelet is better theoretically. The further study is need later.
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