RAE 
— 
  
ta 
pacs 
  
  
8 
picture moves in the vertical direction, the focussing of its parts is actuated automatically. 
In this case the number of working movements in the instrument, when setting orientation 
elements, would be the same as in the Zeiss Stereoplanigraph. The realization of one of the 
schemes described here has brought to light some difficulties caused by the heavy weight 
of the carriages and the complicated linkages of the correction mechanism. Therefore the 
  
  
  
  
  
  
  
  
  
Fig. 10. 
theory of the stereograph, although it had been originally elaborated for the inclined ar- 
rangement of photographs, was later adapted to plotting from horizontally arranged 
photographs. 
Let us assume, that the photograph is set in an inclined position; then, between the 
angles A having their apexes in the plumb point A on the photograph, and the corresponding 
angles A, on a horizontally placed photograph there exists the following relation: 
tg A — tg A, cosa, ( 
3 
where a = the inclination angle of the photograph. 
  
For angles A = 45°, the difference A, — A is 
: . 2a, a” 
Ay — A = i= sin. 1 (8) 
As, on the scheme, the photograph and the surveyed area have a common line of horizon,