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The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008 
homogenous area with high reflectance for absolute radiometric 
calibration. 
Figure 4: Getis statistics of MODIS (July, 2007), Band 2 
Since water coverage of the lake changes along the year, we 
also performed some analysis to have an idea on how these 
changes affect the homogeneity of the area. If there is a relation 
between duration that the region is covered with water along the 
year and its homogeneity index, this may give us information 
about site homogeneity for the coming years. Therefore; firstly 
the regions that was covered with water with a duration ranging 
from 2 months to 8 months (Figure 5), was obtained using 
MODIS images (LPDAAC, 2007). Then for each region we 
calculated mean values attained to that area obtained from Getis 
statistics for July, 2007. Lastly, we looked at the correlation 
between the homogeneity index and the duration that region 
covered with water. Pearson’s linear correlation coefficient, the 
measure of correlation valued between -1 and 1, was calculated 
as 0.9733 which means that there is a positive linear relation 
between two variables. Figure 6 shows the linear relationship 
given as follows: 
y = 0.013.x + 0.087 (3) 5 
Figure 5: Seasonal water coverage in the year 2007 
Figure 6: Homogeneity index relation with month duration 
covered by water 
5. CONCLUSIONS 
In this study, the suitability of Tuz Golii as an absolute 
calibration/validation site for optical imagers of satellites has 
been evaluated. The results obtained are very promising.