The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B7. Beijing 2008 
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and 3.d, respectively. It can be seen that all of the clustering 
results appear the same as that of the Ik-Orig. No colour 
appears anywhere in the overlaid clustering results (Figure 3.b, 
3.c and 3.d). This comparison proves that the images Ik-Orig, 
Ik-Shift, Ik-Str and Ik-Str-Shift have the same quality for image 
classification. 
The check of the statistic reports of the clustering results shows 
that the pixel number in each of the 16 clusters are exactly the 
same in the results of Ik-Orig and Ik-Shift. A few outlier pixels 
are identified when compare between the statistic results of Ik- 
Orig and Ik-Str. Out of the 16 clusters, 9 clusters are identical, 
and 7 clusters have a few pixels of difference. In total, 98 pixels 
are identified as outliers in the classification/clustering of an 
image with more than 1 million of pixels (1024x1024 pixels). 
(a) Clusters from Ik-Orig 
(c) Clusters from Ik-Orig (red) and Ik-Str (green and blue) 
The outliers may be caused by limited clustering iterations 
and/or other settings. Therefore, the statistic reports also 
demonstrate that the four testing images have the same quality. 
3. EVALUATION OF THE SEVEN QUANTITATIVE 
INDICATORS 
To evaluate the capability of the seven often used quantitative 
indicators (MB, VD, SDD, CC, SAM(°), ERGAS, and Q4) for 
the measurement of image similarity or difference, they are 
applied to the three testing images Ik-Shift, Ik-Str and Ik-Str- 
Shift with the image Ik-Orig as reference. The quality 
measurement values are shown in Table 2. 
(d) Clusters from Ik-Orig (red) and Ik-Str-Shift (green and blue) 
Figure 3. Comparison of the 16 clusters clustered from the four testing images using ISODATA method (in (b), (c) and (d) the 
clusters from Ik-Shift, Ik-Str and Ik-Str-Shift are displayed in green and blue and overlaid with that of Ik-Orig displayed in red) 
MB 
VD 
SDD 
CC 
SAM(°) 
ERGAS 
Q4 
Ik-Shift 
100 
0 
0 
1 
9.047 
6.159 
0.950 
Ik-Str 
129.076 
10582.9 
41.398 
1 
9.725 
8.584 
0.852 
Ik-Str-Shift 
229.076 
10582.9 
41.398 
1 
15.918 
6.793 
0.766 
MB - Mean Bias, VD - Variance Difference, SDD - Standard Deviation Difference, CC - Correlation Coefficient, SAM - 
Spectral Angle Mapper, ERGAS - Relative Dimensionless Global Error; Q4 - Q4 Quality Index 
(Ideal values: MB = 0; VD = 0; SDD = 0; CC = 1; SAM(°) = 0; ERGAS = 0; Q4 = 1) 
Table 2. Values of the seven image quality indicators for similarity measurements between the reference image Ik-Orig and the three 
testing images Ik-Shift, Ik-Str and Ik-Str-Shift