357 
EN 
  
  
  
  
Photo 2. Case of in tight condition Photo 3. Case of in loosen condition 
Refrection level from the object Lighting source 
dark bright 
  
  
  
SPRING 
   
  
  
  
   
upper plate 
  
shadow 
  
  
  
+ 
M | shadow part | 
D Wo (1) I lower plate 
7 shadow part | | 
ht 
D : Distance form upper plate edge 
to lower plate edge 
If it is possible to knew the thickness of plate(T), 
width between two plates can discribe like this 
Width=D-T | 
  
  
    
Line Camera’ s scan 
  
  
    
  
   
  
  
  
  
heig Cut Image of Spring plate 
  
  
  
  
  
Figure 7. The relation between the distance of plates and the shadow 
On the other hand , the scale of image data is described by the following expression (Figure 8) . 
TAN(A) = H / X 
A: an incline angle of the line sensor camera 
H : a height of a subject 
X : the moving distance of the line sensor camera 
With this way ‚if it possible to record the movement peed or the movement distance per every line scan , 
it is able to calculate the width of the spring plate. The case of experiment on the field , the traveli 
ng speed is fixed as 30 kilometers per hour . And , that means one data line's length is 0.8 
millimeters . 
1995 IAPRS, Vol. 30, Part 5W1, ISPRS Intercommission Workshop "From Pixels to Sequences", Zurich, March 22-24 1995