ing the road 
also the DTM 
1 detected and 
RASS, we can 
s classified as 
isily classified 
. Istanbul 2004 
  
   
    
  
  
   
   
    
   
   
   
     
    
     
   
     
    
    
   
    
  
  
     
     
   
   
   
  
  
  
  
  
  
  
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B3. Istanbul 2004 
  
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Results of the Final classification obtaine 
GRASS program site No. 1. 
  
The results obtain by GRASS shown in figure 4.7 include 
4.3 The Final DTM many misclassification points specially near the tunnel (A,B), 
Combination between the robust and the roads methods also areas E and F are roads but they have the same 
misclassification. 
Disadvantages of the robust method: The results obtain by the roads method are shown in figure 
By using orthogonal polynomials we can overcome labelling 4.8, areas 1 are bridges that have been classefied as DTM 
buildings as a DTM, but we still have misclassification in where all roads have been extracted. 
points near tunnels which have been classified as objects 
although they belong to the DTM. 
  
Disadvantages of the roads method: 
|. We can't always generate the DTM in areas that do 
not contain road network. 
2. Elevated bridges will be classified as DTM 
For better results we combine the tow methods as follow: 
1. The DTM generated by roads method is taken as a 
basic DTM. 
2. In areas where DTM could not be generated because 
lack of road network, we use DTM generated by the 
robust method. 
3. To remove bridges we applied the robust method 
another iteration on the DTM. 
The results shown in figure 4.5 are more reliable 
comparing to the results obtained by GRASS figure 4.4. 
  
  
Figure 4.7-Results of the final classification obtained by the 
GRASS program, site No. 2. 
Good results are also obtained by the roubust method using 
the orthogonal  polynominal, but still there are 
misclasification specially near the tunnel (see A & B figure 
4.9) that classified as objects althoug these areas belong to 
the DTM, but the results are better than those obtained by 
GRASS. 
Figure 4.5- Results of the final classification of combining the 
road method with the robust method - site No. 2. 
Site 2 
Another site but more complex than the first one which 
contain: l.bridges, 2.Tunnel , 3.comblex building. See figure 
4.6 
  
method, site No. 2.