1129 
AN AUTO-ADAPTIVE INFORMATION PRESERVATION FUSION 
METHOD FOR SAR AND MULTISPECRAL IMAGES 
H. Sun 3 , B. Pan b , Y. Chen 3 ’*, J. Li 3 , L. Deng 3 
d College of Resources Science & Technology, Beijing Normal University 
b School of Remote Sensing and Information Engineering, Wuhan University 
KEY WORDS: Fusion; SAR; Multispectral; Wavelet; Auto-adaptive 
ABSTRACT: 
Due to the special imaging model of SAR, its image includes certain special information that unavailable in multispectral image, 
however, the interpretation of SAR image becomes more difficult than visible image. Therefore, the fusion of SAR image and 
multispectral image is primarily for the purpose of making better use of SAR image information. For this application, the auto- 
adaptive information preservation fusion method based on wavelet transform was proposed. It automatically adjusts weight 
coefficient according to the information capacity of SAR image and multispectral image, and then auto-adaptively adjusts fusion 
result, avoiding a single and ponderous fusion strategy for the whole image. Experiment results show that the novel method can 
better preserve SAR image texture and structure information, especially the unique information in SAR image, meanwhile, the novel 
method as well as better preserved spectral information with good results. 
1. INTRODUCTION 
The remote sensing images acquired by various single sensors 
have some limitation and differences in the respect of geometry, 
spectrum and spatial resolution. Therefore, it is necessary to 
fuse or synthesize the information contained in the images of 
multiple sensors, in order to enhance the distinguishing 
reliability and interpreting ability of the images (Li,2003), and 
prepare for the classification, target recognition and other more 
latter applications. 
The traditional processing method is that fusing multispectral 
image of low spatial resolution and panchromatic image of high 
spatial resolution and gaining result image which not only 
owing higher spatial resolution in panchromatic image but also 
obtaining spectral information in multispectral image. As 
respect to application, the processing method might enhance the 
interpreting ability of original images. Nevertheless, different 
applications require the fused images not just eclectically 
contain the detail information in panchromatic image and 
spectral information in multispectral image. As for the 
application of feature extraction, mapping, the detail 
information of image is normally more important; while as for 
the application of classification, it is normally more important 
to focusing on the accuracy and integration of the spectral 
information (Deng,2005). 
For the fusion of synthesize aperture radar (SAR) image and 
multispectral image, SAR image is regarded as main body to 
contain the detail information better, and the multispectral 
image is used to supply additional spectral information. As the 
imaging mode of SAR is active in microwave band, SAR can 
penetrate clouds, rain and snow, and bear the ability of round- 
the-clock working and in some sense penetrating earth’s surface 
(Woodhouse, 2004). Therefore, SAR sensor might acquire 
information that unavailable for visible or infrared sensor. 
However, as the special imaging way SAR has, the 
interpretation of SAR images is more difficult than that of the 
visible ones, it is necessary to fuse SAR image and 
multispectral image, in order to better utilize the special 
information SAR image contained. 
The traditional fusion methods including Intensity-Hue- 
Saturation (IHS) transform, Principle Component Analysis 
(PCA), Wavelet Transform and High Pass Filter (HPF), etc. 
And more and more advanced methods based on the traditional 
fusion methods have proposed (Li, 1994). Most of these 
methods focus on preserving spectral information or eclectically 
preserving information between spatial detail one and spectral 
one, which resulting the fused image usually only advance the 
visible effect. But scarce methods regard panchromatic image 
as main body, aiming to maintaining as much as detail 
information. 
In this paper, from the aspect of application-oriented, we 
proposed a novel fusion method to synthesize SAR image and 
multispectral image. This novel method is based on wavelet 
transform, which we called auto-adaptive information 
preservation fusion method. It not only better preserves spectral 
information in multispectral image, but also, more importantly, 
preserves special detail information in SAR image. 
2. THE TRADITIONAL FUSION METHODS BASED ON 
WAVELET TRANSFORM 
An image can gain (37+1) components by 7-level two- 
dimension discrete wavelet transform, one of which is low- 
frequent approximate component, noted as Id , owing major 
energy of original image, the other 37 ones, noted as 
H[ , H' 2 and H[ respectively, are high-frequent detail 
Corresponding author. 
Email address: cyh@ires.cn