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Farhad Samadzadegan 
  
measured manually are shown in Figure 12. This measurements have been carried out for other purposes but can be 
used in our experiments for visual comparison with the results of the automatic DTM generation. 
In addition, a very dense grid is measured manually with a 
?0m sampling interval. These measurements are taken as a 
ZZ 7 
ir 
  
Figure 13: Visualization of the automatically 
reconstructed DTM 
reliable reference for the automatically generated DTM 
based on the fuzzy reasoning concept presented in chapter 3. 
A shaded visualisation of the reconstructed DTM is plotted 
in Figure 13. Even though the scale of both figures does not 
allow for any detailed comparison the similarity of the 
morphologic structure of the terrain surface can be well recognised by comparing Figures 12 and 13. 
  
Figure 12: Manually measured contour lines 
Some statistical data about point extraction, matching and DTM reconstruction are collected in Table 1. In addition to 
the 20 pu pixel size (layer 0) five additional layers have been used within coarse-to-fine processing. The respective 
numbers of points detected by the fuzzy point extraction procedure if given for each layer together with the number of 
matched points. Typically about 50 to 70% of the points are eliminated by the fuzzy conditions applied in matching. 
An indicator for the accuracy of the automatically generated DTM is the rmse calculated by taking the check points into 
account. The rmse values of the differences of the height of the check points and the DTM heights are indicating an 
accuracy of 1:2 000 of the flying height which is considered to be a good results facing the low texture available in the 
images (Figure 11). 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
Image Space Object Space 
Detected Detected Match Number Mean RMSE 
Points Points Points of Check Deviation to Check 
(left) (right) Points to Check Pts(m) 
Points (m) 
Layer 5 489 422 226 11543 -5.916 12.558 
Layer 4 1927 1759 900 11543 -1.886 6.003 
Layer 3 8178 7250 3486 11543 -0.708 3.495 
Layer 2 33817 30025 13509 11543 -0.386 1.966 
Layer 1 134925 122252 51212 11543 -0.208 1.381 
Layer 0 533648 490245 170267 11543 -0.111 0.763 
  
  
Table 1: Statistics on point extraction , matching and DTM reconstruction in the test area 
  
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B3. Amsterdam 2000. 
805