Jalal Amini 
  
al image 
rphology Figure 4. Detected edges by canny operator, a) The edges of fig 3a, b) The edges of fig 3b, 
c) The edges of fig 3c 
b. Mathematical morphology provides a semi. automated techni 
que for extraction of linear objects such as roads 
S. This idea has been shown in figure 5. The linear 
objects are identified by applying the structure element I over the images of the figures 3a and 3c. 
  
  
and rivers. These objects can be vectorized and input to a GI 
y "local 
tigations 
  
Figure 5. Sequential thinning using element L, a) Original image 
b) Opened-Closed image 
In order to remove unwanted short skeleton legs from figure 5b, one or two end points of a longer line can be 
deleted by structure element E * Figure 6 represents the result of smoothing with the structuring element Ep * 
| image. over the thinned image of figure 5b. 
  
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B3. Amsterdam 2000. 41