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NEW METHODS OF TILT DETERMINATION IN VERTICAL AIR 
PHOTOGRAPHS 
by 
Dr. Ing. Josef Sutor, München, Germany. 
In this report new methods of tilt determination are shown which are so 
simple that no considerable work is caused. Different ways are existing for the 
solution of this problem: Tilt determination by use of 
1) maps 
2). fixed points on the ground 
3). neighbouring photographs overlapping more than 50%. 
In all these cases angles or distances may form the base for tilt determina- 
tion. 
Tilt determination by use of maps. 
The square limitation of air photograph (size d' xd") has to be drawn accord- 
ing to the situation in the map. The opposite sides of the quadrilateral figure in 
the map are no longer parallel, but they form the small angles 2; and 911. 
The inquired elements of tilt result from: 
ge = ol ym V 0g? 4- 97r 
Hereby 7 determines the nadir distance and a’ the 
principal line relating to the direction of the sides of 
the angle 71. 
Tilt determination by use of fixed points 
on the ground. 
  
  
  
For rectifying fixed points are necessary. Four of Fig. 1 
these points are sufficient. By connecting two fixed 
points in the way that the lines intersect, four distances are formed in photo- 
graph and map. For two distances lying in 
  
  
  
  
f a straight line gr results: 
p' 
2 
, 52 NL 
*, m 
4 
   
"V 
N 
If these terms c' are measured in direc- 
tion of this straight line to which they 
belong, the point of intersection of the 
perpendiculars is the plumb point N'. In 
such a manner the nadir distance and the 
principal line are known.