International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B5. Istanbul 2004 
  
3.1 Initial Value 
3.1.1 Initial Values of Camera Position 
Initial values for the temporal GCPs are required as same as 
orientation parameters in calibration procedures. Figure 4 
shows the concept of computation of initial values for the 
temporal GCPs, and initial values for the temporal GCPs are 
computed as follows. 
In Figure 4, Dj, D; and D; are space distances, angle ¢ is 
computed with respect to focal length ( / ) and image 
coordinate using following equation (1). 
2 
Xpl'Xp2 + Ypl Ya + Sf} 
cosa uc m Ip P (1) 
Op, - Op, 
  
Op, and Op, are length from the camera position to image 
points, and the lengths are computed following as equation (2). 
  
Op, =x," +r 
Therefore, initial X, value of the point P, for the origin 
coordinate (0, 0, 0) is computed as D,, from equation (3). 
  
Dok BAD eB 2 D D. scotca (3) 
    
Q (X5, Yo Zu) 
  
N (us Yo HX. 
  
On the contrary, relationship between focal length and flying 
height (distance from exposure position to the object field) is 
simply expressed as follows using image distance d to the 
corresponding ground distance D; under the assumption that 
vertical photo was taken over flat terrain. 
From the following relation, initial Z coordinate for exposure 
position is estimated as 77 . 
f/HzdiD (4) 
Furthermore, let make ground coordinate for the camera 
position O (Xo, Yo, Z9), P, (Xj, Yy, Zi) and P» (X5, Y; Z), 
space distance Dj, D» is expressed as follows, 
2 
Di sixo x r- N) +(Zo- zy (5) 
Dj z (X - X3 * (Yo - Y «(Zo - Z3) (6) 
where: (X92) (0.000) , (3 3,$5,2; )- (X, 0,0) 
By equations (5) and (6), initial value for camera position is 
obtained as follows. 
Xp «ip? -Df «xy)2x, 
2er 2 
E D ED- 
E On 
"A 41 
p^: 
0 (X, Yon Zu) UT x 
   
  
  
P(X, Yo, Zu) 
Figure 4. Computation of initial value for temporal GCPs 
P; (X, Ys Za) 
     
    
   
      
      
   
    
    
    
   
     
  
  
   
   
    
  
   
     
    
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