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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B4. Istanbul 2004 
  
surface is converted to 250.000 sampling points and 
grid/lattice (see Figure 5). 
  
  
    
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Figure 5. Lattice of the surface 
42 Editing The Vertical Differences of The Buildings and 
Solid Modeling the Buildings 
Like the z errors in the point clouds, the buildings have 
height errors in it as well. The reason of these errors is again 
arises during stereo compilation like other z errors. Operators 
sometimes see different points other then the roof corners of 
the building (Figure 6). Even if they compile it with true z 
value, it appears as an error when seen from the perspective. 
For instance he/she can set the floating mark on the surface 
instead of roof. They can not be realized from the top view 
(see Figure 6). So that errors can not be edited during 2D 
editing phase. This kind of errors is very rare, but can be 
encountered and needs high attention (Emem, 2002a). 
  
  
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Figure 6. Wrong point compilation error 
  
The other error arises because of the roof corner height 
differences. Despite the operator compiles the building 
correctly, this error comes from the nature of the view and it 
433 
is inevitable. Normally the height of the building corners 
should have the same height value. But some buildings which 
have triangle roof types are compiled with different height 
values (see Figure 7). 
  
  
  
  
Figure 7. Triangle roof 
This kind of buildings can not be realized like the preceding 
error during the 2D editing phase (Figure 8). 
  
  
  
  
  
  
Figure 8. Height difference of the roof 
Even if both errors are not critical for conventional usage of 
maps, they are important errors for 3D city modeling. 
Therefore these errors should be corrected before solid 
modeling the buildings. 
If we consider the compilation process of buildings, the 
operator starts from a corner of the upper point of the 
building. Therefore, there are 2 ways to correct height 
differences on the buildings. First, accepting the arithmetical 
average value of the building data points. But this assumption 
causes changes on the values from the real values. Other way 
is to assume the correct value as the first compilation data 
point the building. Because, operators generally fix the 
parallax on the first data point correctly and more carefully in 
addition the most of them start to compilation from upper 
point of the building instead of the roof corner (Emem, 
2002a). In this study, the first data point of the building is 
assumed as the correct value. Therefore all the buildings on 
the project area were edited with the accepted height values 
(see Figure 9, 10). Some buildings on the project area such as 
stadium and complex shaped hotel were edited separately 
from others. 
  
   
  
  
  
Figure 9. Correcting values according to accepted value