Full text: Mapping without the sun

234 
A NEW PAN-SHARPENING ALGORITHM AND ITS APPLICATION 
IN GEOGRAPHIC FEATURES INFORMATION EXTRACTION 
ZHU Lijiang 3 
a Beijing Research Institute of Uranium Geology, RO.Box 9818,Beijing 100029,China 
E-mail: zljrenwen@hotmail.com 
KEY WORDS: Pan-sharpening, PSF, Fusion, Quickbird 
ABSTRACT: 
Many different fusion techniques were developed for fusing multi-spectral low-resolution remotely sensed images with a more highly 
resolved panchromatic image, the goal is to obtain a high-resolution multi-spectral image which combines the spectral characteristic 
of the low-resolution data with spatial resolution of the panchromatic image. Almost all these fusion methods are not satisfactory in 
tiny geographic features (road, building, etc) information extraction for some very highly resolution satellite imagery collected from 
the sensor such as Quickbird, Ikonos and so on. In this paper, we analyzed the process of image data collection and found that two 
factors caused by the sensor’s orientation to the scene is the main factor that cause a misregistration between the pan and MS bands 
and result in a blurry that is apparent around bright objects in fusion process. One is parallax (different look angles) between the 
bands causes misregistration before the fusion. Another is the diffraction of the different MS bands cannot be neglected because of 
the image have so high resolution and different wavelength among the bands. Through constructing a PSF model between different 
pixel and bands in same satellite scene, the new fusion method solves these problems according to the geometry relation between the 
scene and the sensor. As an example, the new pan-sharpening algorithm and other data fusion methods like HIS, PCA and UNB 
(Digital Globe’s default pan sharpening algorithm) were applied to four related multi-spectral images of a Quickbird satellite scene to 
extract geographic features information. The comparison between these pan-sharpening algorithms shows that the new 
pan-sharpening algorithm is perfect in the test scene. 
1. INTRODUCTION 
Pan sharpening is a type of RS image fusion. The goal is to 
obtain a high-resolution multi-spectral image, which combines 
the spectral characteristic of the low-resolution data with the 
spatial resolution of the panchromatic image. As a result of the 
demand for higher classification accuracy of groundcover and 
extraction of tiny geographic features (road, building, 
vegetation, etc) information from some very highly resolution 
satellite imagery collected from the sensor such as quickbird, 
ikonos,and so on, many pan-sharpening algorithms were 
developed. DigitalGlobe has evaluated a number of pan 
sharpening algorithms in detail, UNB (stands for University of 
New Brunswick) Algorithm is DigitalGlobe’s default pan 
sharpening algorithm. 
The objectives of this study are the new algorithm 
development for fusing multi-spectral low-resolution remote 
sensing image with a more highly resolved panchromatic 
image collected by Quickbird sensor (see Table 1). PSF was 
considered in this process of building new pan-sharpening 
algorithm model. 
Pan 
725nm(450-900nm) 
Blue 
479.5nm(450-520nm) 
Image Bands 
Green 
546.5nm(520-600nm) 
Red 
654nm(630-690nm) 
Near IR 
814.5nm(760-900) 
Spatial 
Pan 
61 cm (nadir) to 72 cm (25 
off-nadir) 
Resolution 
MS 
2.44 m (nadir) to 2.88 m (25 
off-nadir) 
Table 1. Characteristics of the Quickbird data 
A multispectral Quickbird scene consists of four bands called 
Blue, Green, Red, and NIR. The first three bands characterize 
the ground cover in the visible wavelength range and the four 
band the near infrared wavelength range. Figure 1 depicts the 
spectral characteristic of all Quickbird bands. 
Figure 1. Spectral characteristic of Quickbird (C. Padwick, 
2004) 
2. RESEARCH DATA 
The main research data is a standard bundle of pan and ms 
image scene data, which is downloaded form the 
DigitalGlobe’s website. The website also provide bundles of 
pan-sharpening scene data of same data, it is convenient to 
compare the new pan-sharpening algorithm to other
	        
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