y this 
etrical 
points 
Joints, 
n will 
ithout 
—M——À 
- dy 
da 
dn 
Hx 
lation 
  
    
   
   
   
    
  
  
  
  
   
  
   
  
  
  
  
  
   
  
Ng — — dyun — dyis t dyg + dyss — dxyy + dxig — dx, 4- dX 
Ng = —dyn A: dyas — dygy d dyss + dur + dX15 — dxg, — dXs5 
Nas = dur — dis — dys; + dyss + dx, 4. dxyg dxs, d- dxgg 
Nu = di + dis + dygy 4 dyss -- dxyy — dxyg — dxg, + Xs; 
10 -6 4 
In a similar way also the other point combinations can be treated. 
Also the distortion curve can be determined from the variation of dz, 
from group to group. 
If a grid on the ground is photographed with a nearly vertical camera, the 
distortion of the camera lens can be easily determined by a similar procedure. 
In this case the image co-ordinates are measured in a comparator and are 
compared with the given co-ordinates on the ground. From the adjustments, 
the variations of dz, will give the distortion curve. Also the standard error of 
the observations will, of course, be determined. 
The accuracy and error propagation within single pictures after a re- 
section in space can also easily be determined. 
If the same area is photographed under different atmospheric conditions 
it might be possible to determine the distortion effect of the refraction from 
day to day. 
Finally: 
352 53