1, Formulas and illustrating examples for grid 
tests of projectors in photogrammetric 
instruments. 
1.1 The basic formulas of the grid method applied to projector tests. 
  
1.11 Correction equations. 
According to fig. 1 the connection between small changes in the exterior 
orientation and the corresponding translation of projected points is given 
by the following wellknown error equations 
2 
P x x xy 
(1) dx = dx vA de drum ) hd + £= dw 
2 
(2) dy =-dy, - # dz, + xdk - +” do + (1 + 2») hdw 
h 
After substituting image coordinates x,” y“ and assuming redundant obser- 
vations the working error equations are 
  
2 
(3) v,= 4x, - az, - y°£ de - (1 + X—) hdp + &L hdo - dx 
C c 
y h x y” v5 
(4) Vo = -dy, - cz, + x —dx - =r hdo + (1 Eo dy 
where dx and dy are defined as coordinate errors 
  
(5) dx z 
x -— . 
measured given 
(6) dy=y 
measured Ygiven 
If we want to obtain the corrections of the elements of orientation we 
change the signs of the right side of (1) and (2). From the working error 
equations normal equations are formed and solved in the usual way. See 
1.16. Summary of results!. .G .. p. 10. 
Below the computations primarily refer to the elements of the exterior 
orientation and coordinate errors in the projection plane. With help of 
the scale factors all data can be referred to the image plane for the actual