36 
SYMPOSIUM PHOTO INTERPRETATION, DELFT 1962 
of the image motion function will be published as a separate investigation by 
Hendeberg and the author [12]. The haze may be investigated in the same 
manner. 
According to the validity controls carried out, it seems probable that the 
test method used here gives satisfactory results. It has to be remembered, how 
ever, that only about ten aerial photographs are analysed. Although negatives 
were employed here, the method is applicable for diapositives as well as paper 
prints. 
Transfer 
% 
• • * •Theoretical function, shutter included 
o o o o 
Fig. 8. Transfer function for image motion 
obtained from the air. Velocity 536 km/h 
and 249 km/h, 1/280 sec. 
Transfer 
% 
Low contrast test line A D=0,4 
• • • Natural test object 
Fig. 9. Transfer functions obtained from 
the air 
Analysing natural test patterns in the terrain 
In pracdcal work, an essential drawback burdening the method above is the 
test pattern which must be laid out in the terrain before photography. Con 
sequently, the use of any natural test pattern in the terrain should simplify the 
procedure substantially. 
The detection of a narrow straight line in the aerial photograph, a fence 
or a railway, for example, ought to be possible, but unfortunately the shadow 
effect will commonly deteriorate the symmetry of the slit image. However, a 
sharp edge frequently appears on the photograph as the limit between shadow 
and a sunlit area. 
It is a well known fact that the micro-photometer trace of a knife-edge may 
be transformed to the corresponding slit image trace [13]. In fact the slit image 
consists of the derivative of the knife-edge. Consequently, it seems possible to 
determine a T-function from an aerial photograph containing such a sharp 
edge. 
The principle outlined here by the author is now realized. One of the aerial