0 
    
   
    
    
   
   
  
  
  
  
  
  
  
  
  
  
  
  
  
  
-0 „024 
N / \ 
-0 ,044 \ 
-0 06. \ 
Radial distortion according to the grid method 
— — " " n n n 
manufacturer 
Fig. 1. Radial distortion of the Stereoplanieraph at the projection distance of 300 
mm (above) and 200 mm respectively. c — 100 mm. The right projector. 
found to be around 20 microns in the image. Thus the standard error 
of the distortion 1s about 10 microns. This determination of the accu- 
racy, however, is doubtless influenced by systematic errors that cannot 
be compensated by the elements of orientation. 
The whole of the grid is not visible when using base out or base in. 
Thus the determination of the distortion has to be made in groups of 
points, where the points no longer are in symmetric positions. The nor- 
mal equations for solving corrections to the elements of orientation had 
to be set up and solved, [3]. The distortion curves are shown in figure 
2. The standard error of the measurements was also in this case around 
20 microns. The standard error of the distortion however, was a little 
larger, due to the asymmetry of the points and amounted to around 16 
microns.