# 
+10 
d T Y T T tT T T 
50 
- 10-1 
  
Fig. 5. Lens distortion curve for an Aviogon lens. 
In this expression the positive sign indicates that the two vectors have 
opposite directions which is without interest in practice. 
'This residuum is the only effect due to the lens distortion that is 
observable by the operator. Schematically, this operation is illustrated 
in the figures 9—11. 
3.4 Model Deformation 
By means of the tilt e as an element of the relative orientation it has 
been possible to compensate the considerable vertical parallaxes caused 
by the lens distortion of the infra-filter and the camera as a unit and to 
get a stereoscopic model, roughly speaking, free from disturbing paral- 
laxes. Let us for a moment look at the formulas that convert a tilt 9 
into a vertical parallax as well as into a change of the altitude, 
Referring to [9], the definition of the vertical parallax is? 72 
— yy. If further the tilt ¢ is defined as positive in the anti-clockwise 
direction we get the following expression of p, and the altitude dh 
x y (x — b) *y 
p, = — nm Tode, + T Tig ET "deo ^96. (5) 
which eauation can be transformed into 
x’ y (x — b^) ; y! ; 
p. = — "de, + : des i. ; 44e (6) 
C C 
It is of interest to observe that p’ = f(¢1, ¢2) will be a rectilimear 
function for x' as a constant. From that it follows that the influence of 
small changes of ¢ results in a rectilinear change along any vertical of 
the stereo-area. Thus, in the vertical parallax nomograms we get a rec- 
tilinear superimposition. 
14