Manfred Wiggenhagen 
  
Figure 8 USGS Mt. St. Helens (9,8 x 14 km) USGS Seattle (72 x 108 km) 
For software testing several USGS elevation data sets have been downloaded via the Internet and displayed in 
various representations ( see figure 8). 
The graphic libraries include a lot of functions for the generation of realistic visualizations of elevation data sets. 
One of these powerful functions is the fog rendering function CoglFog which is shown in figure 9. 
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E 
Se 
SEE 
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Figure 9 Simulating fog, USGS Seattle 
  
992 International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B3. Amsterdam 2000.