232 
3.3.2 Bias Index: Bias index is the ratio between the gray 
12 
0.064929 
0.958670 
difference which is between the gray value of the fused image 
13 
0.064795 
0.961822 
and the gray value of the high resolution image and the gray 
14 
0.065087 
0.948486 
value of the fused image. It describes deflection degree between 
15 
0.065073 
0.950037 
two images. Function (2) is about it. 
16 
0.064782 
0.967982 
17 
0.064744 
0.969986 
D i ^|/,(U)-AM 
MN^h f B (i,j) 
18 
19 
0.064893 
0.065109 
0.961347 
0.947314 
20 
0.064905 
0.964362 
Table 2. Results of PC A transformation 
where 
D = bias index 
M = total number of the image row 
N = total number of the image column 
- number of the row and column 
f A = gray value of the different resolution 
image 
f B ^ ’ = gray value of the fused image 
Bias indexes between different resolution images and fused 
image can be computed by Function (2). The smaller the bias 
index, the closer the resolution of the fused image and the 
resolution of the high resolution. 
4.3 Multiplicative Transformation 
Resolution 
Criterions 
m 
bias index 
correlation coefficient 
10 
0.166083 
0.670760 
11 
0.166104 
0.670031 
12 
0.166192 
0.665437 
13 
0.166057 
0.670076 
14 
0.166323 
0.660959 
15 
0.166315 
0.662954 
16 
0.166057 
0.670664 
17 
0.166030 
0.670942 
18 
0.166165 
0.667535 
19 
0.166367 
0.659890 
20 
0.166935 
0.650448 
4. EXPERIMENT RESULTS 
Correlation coefficient and bias index between fused image and 
image aggregation of different spatial resolution was acquired 
and evaluated, and then spatial resolution of remote sensing 
fused image was determined quantitatively. 
4.1 IHS Transformation 
Resolution 
Criterions 
m 
bias index 
correlation coefficient 
10 
0.019391 
0.780013 
11 
0.019501 
0.783598 
12 
0.019666 
0.770825 
13 
0.019786 
0.782763 
14 
0.019941 
0.760863 
15 
0.019889 
0.763048 
16 
0.019345 
0.781943 
17 
0.019302 
0.783749 
18 
0.019543 
0.775115 
19 
0.019974 
0.759841 
20 
0.019518 
0.776331 
Table 1. Results of IHS transformation 
4.2 PCA Transformation 
Resolution 
Criterions 
m 
bias index 
correlation coefficient 
10 
0.064791 
0.967980 
11 
0.064767 
0.960864 
Table 3. Results of Multiplicative transformation 
4.4 Brovey Transformation 
Resolution 
Criterions 
m 
bias index 
correlation coefficient 
10 
0.108042 
0.945704 
11 
0.108078 
0.945791 
12 
0.108242 
0.933972 
13 
0.108052 
0.945702 
14 
0.108413 
0.922659 
15 
0.108398 
0.924924 
16 
0.108076 
0.944646 
17 
0.108038 
0.946523 
18 
0.108204 
0.937007 
19 
0.108443 
0.921004 
20 
0.108334 
0.932918 
Table 4. Results of Brovey transformation 
From table 1 to table 4, we can see that the biggest correlation 
coefficients and the smallest bias indexes from different fusion 
methods of HIS, PCA, and Brovey are 17m resolution of the 
image aggregation. So the real spatial resolution of the fused 
images are closer to 17m. 
5. CONCLUSIONS 
In this paper, firstly, the image aggregation which resolution is 
11m, 12m, till 20m is obtained by the resample of SPOT pan 
image which resolution is 10m. Secondly, the fused images are 
obtained by different fusion methods. Thirdly, the correlation 
coefficients and bias indexes are computed between the image