International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B4. Istanbul 2004 
After editing, the entire buildings are solid modeled by 
extruding them down to the DTM (see Figure 11, 12-13). 
  
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Figure 13. Pine tree symbol 
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Figure 14. Symbol for other tree species 
  
   
The trees on the existing map, which is used for this study 
contains two species of tree. These are pine trees and other 
species. Therefore, two types of tree symbols are used in this 
study. One symbol is designed for street lamps (Figure 15). 
This height correction process provides buildings to be better 
shaped for the 3D city models. Since it is hard and expensive 
process to extract roofs from the existing maps, the roofs of 
the buildings are neglected. Editing of the height differences 
on the buildings are done automatically. 
  
  
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Figure 15. Street lamp symbol 
  
  
  
  
Figure 12. Solid models of buildings 
However, the trees and the lamps are displayed as planar 
objects in the digital maps, they contain height values. They 
are compiled from the intersection point with the surface if 
possible. In the 3D city model, those 3D cells are placed 
instead of the planar objects on the map. 
4.3 Preparation of the 3D cell libraries and locating them 
on DTM 
In this study, a symbology library is prepared for two kinds 
of trees and street lamps. Those symbologies are converted to 4.4 Visualization 
the cells to use them in the 3D city model. The heights of the 
trees and lamps are assumed as same values (see Figure 13, 
14, 15). Therefore, these 3D cells are placed just for 
visualization of the 3D city model. 
In this study, two different visualized city models are 
generated. First, the orthophotos of the project area are used. 
Orthophotos are draped on the DTM, thus photo-realistic 
view of the surface is generated (see Figure 16). 
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