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pan-sharpening algorithms like UNB etc. Other standard 
quickbird imagery products are used to research and develop 
the new pan-sharpening algorithm too. 
3. METHODOLOGY 
This can be explained and described by the point-spread 
function (PSF). Under a slant viewing angle, the cross 
radiation of the adjacent pixels side to the spacecraft are more 
obvious than the other side (XU, 2005). On the other side, the 
more short of the wavelength, the more apparent is the cross 
radiation. 
3.1 Atmospheric effect and Quickbird sensor ’ s System 
MTF 
Vegetation has the strongest reflection at the near-infrared 
range and considerable absorption at the visible bands. On the 
contrary, water, roads and other objects like house roof etc 
absorbs the near-infrared radiation, and reflects most of the 
visible radiation. The great differences in the near infrared and 
visible reflection properties of geographic features make the 
coupling between the features and other object around the 
destination. In this process, atmosphere plays a critical role. 
Atmospheric cross radiation effect can be described by the 
point spread function (PSF), whereas by the MTF in the 
frequency domain. The Quickbird sensor’s System MTF 
includes atmosphere, telescope, detector, and data 
compression/expansion (Paul W.Scott, 2004). The Diffraction 
from optics also has contribution to MTF. Thereupon, the GSD 
of the sensor at nadir in fact is smaller than the nominal 
resolution. 
3.2 PSF and Misregistration between pan and ms bands 
Through constructing a new PSF according to the geometry 
relation between the image scene and the sensor, we can solve 
this problem. The analytic expression of the PSF is very 
complex and not convenient to use in fact. We constructed the 
new PSF with a form 
of 5* 
5 matrix 
shown as follows. 
0 
0 
0.05 
0 
0 
0 
0.12 
0.47 
0.30 
0 
PSF = 
0.02 
0.42 
7.00 
0.60 
0.08 
0 
0.12 
0.47 
0.30 
0 
0 
0 
0.05 
0 
0 
Where sensor’s azimuth angle = 90 
The new PSF is convenient to use in computing with some RS 
software like EADARS etc. The matrix can be rotated with the 
sensor’s azimuth angle. 
Misregistration between pan and ms bands results in a blurry 
pan sharpened image. There are many factors can cause 
misregistration. These factors include random spacecraft 
motion between collects, parallax between the bands and 
pan-sharpening Algorithm like PCA (Figure 2) and Wavelet 
sharpening. 
3.3 The establishment of the new pan-sharpening 
algorithm 
A. Pre-processing of Quickbird data 
All pan and ms bands of the image scene will be used in this 
study. The DNs have been converted into radiance value. The 
conversion equation (Kei Krause, 2003) is as follows. 
L = absCalFactor □Q (2) 
pixel .band band ^pixel .band v ' 
Where w =top-of-atmosphere spectral band 
-integrated radiance image pixels 
absCalFactor■ =absolute radiometric calibration 
factor for a given band and is listed in the .IMD file 
Q w =radiometrically corrected image pixels 
(DNs) 
Figure 2. Pan-sharpened image with PCA algorithm 
(misregistration is apparent around bright objects) 
(satAz = 298.4;satEl =69.6;crossTrackView Angle = 
-18.1;inTrackViewAngle = 5.9;) 
In many pan-sharpened image (Figure 4) with PCA algorithm, 
the blurriness around bright objects always orientates to the 
sensor’s observation angle , so we can simply get the sensor’s 
(not satellite’s) azimuth angle with respect to the scene from 
the pan-sharpened image. Thereupon, the sensor’s orientation 
to the scene is the main factor that causes a misregistration 
between the pan and MS bands and result in a blurry that is 
apparent around bright objects in fusion process. 
There are many resampling method to upsample the MS bands 
GSD to the PAN bands. Cubic Convolution can slightly 
increase or decrease MTF of the image data (Paul W.Scoott, 
2004). So in the new pan-sharpening algorithm, we select the 
Cubic Convolution as the main resampling method. 
B. Building of the new pan-sharpening algorithm 
Since the panchromatic band covers all ms bands, we can get a 
approximated panchromatic band from the all four ms bands 
based on the QB spectral band responses (Figure 1) and the 
Top-of-atmosphere sun radiance in the QB spectral range. This 
can be shown as an equation as follows.