The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Voi. XXXVII. Part B4. Beijing 2008 
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The wallis filtering result of images in figure 8 is showing in 
figure 10. Figure 11 is the mosaic orthophoto result after wallis 
filtering operation with the stand image in figure 10 left. 
Figure 10. Left is stand image, middle and right is the wallis 
filtering result of image in figure 8 
Figure 11. The result after wallis filtering, the blocks in figure 9 
is removed after wallis filtering 
2.3 Seam Lines Elimination 
Seam lines elimination is a necessary processing step after seam 
lines detection in orthophoto mosaic. Even though the hotspot 
removing and colour balance is very good effect, the contrast in 
seamline is also clear between two mosaic orthophotos (see 
figure 12). Feathering process is a useful method for seamline 
elimination when the seam line is simple, but its hard 
elimination for complex form of seamline. 
Figure 12. The seamline between mosaic orthophoto 
Template operation is suit for any form of seamline. The first 
step of template operation is determined mosaic areas which 
decided by seamline and create a template (figure 13, left top). 
Then median filter operation in template (figure 13, right top, 
filter size is 9 pixels). Finally mosaic two images with template 
operation. Figure 14 is the seamline elimination result with 
median filtered template operation. 
Figure 13. Left top image is oral template of mosaic area, right 
top is median filtering result of oral template, left bottom is the 
mosaic result with oral template, and right bottom is the mosaic 
result with right top template 
3. CONCLUSION 
This paper introduced the colour problems and their processing 
method in orthophoto mosaic, include hotspot removing with 
homomorphic filtering, colour balance with wallis filtering and 
seam lines elimination with median filtered template operation. 
Experiments proved the methods mentioned in this paper are 
useful and it has been used in DPGrid system (Digital 
Photogrammetry System Based on Grid Computation). 
Figure 14. Seam lines elimination result of figure 12