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One of the fundamental problems of photogrammetry is the 
reconstruction of the pencils of rays from the photography, 
solve this problem it seems desirable to determine on one hand 
the systematic influences upon the ideal central projection at 
the moment of exposure and on the other the systematic errors 
which remain after the reconstruction of the pencils of rays ip 
the photogrammetric plotting instrument. 
For that reason it is required to know the systematic 
errors, which depend upon the instrument. 
strument it is possible to reduce these errors, 
cult to obtain a sufficiently good result within reasonable li. 
mits of the operation and if extreme accuracy is required, the 
systematic errors can be corrected numerically, 
These systematic errors depend upon errors in the inner an 
outer orientation of the projectors and upon other errors in the 
projection system, 
the systematic errors depend upon errors in the inner and outer 
orientation only. 
the treatment of problems belonging to this category, worked out 
by B. Hallert in [1 J, [2], and [5] 
Each projector of a stereophotogrammetric instrument is 
tested separately. 
jector in a vertical position (95 o su 
ry determined enlargement. 
grid are measured. 
coordinates cannot be directly measured, e.g. Multiplex, it is 
suitable to take a photograph of the grid with the projector a 
a camera, The coordinates of the photographed grid are measu- 
red. see [4.] 
By adjusting the in. 
For this investigation it is assumed that 
The procedure is based upon the methods for 
An accurate grid is projected with the pro- 
x) and at a prelinine- 
The coordinates of the projected 
In those instruments where the projected 
    
  
  
  
  
  
  
   
   
   
    
  
  
   
  
   
   
   
    
  
  
    
    
   
  
   
  
  
  
    
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To 
If it is diffi.