DISTINGUISHABLE DETAILS IN AIR PHOTOS 
Werner Schubert 
Fils AS No!fen 
F'uschkinplatz 1 
The content of inforsat ion of air photos suet be very high to obtain a possibility of multiple interpretation. 
One of the most important desands is to distinguish Details on a very high level. In general the property 
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u* is composed of several single parameters, 
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transfer f 
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Decisive paraоe ters: шоD ui 
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global parameter 
^production of details" depends on 
•ne »ait: parameter limiting frequency 
f objective and film. Another important parameter is 
siting frequency, focal length and altitude. 
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moduiation 
c ru e spcLidi frequency given о y the 
knowledge about the con 
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ditiens of exposure 
1owe to determine t- 
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details is 
camera 
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Details, 
hts one nac 
:onsiDer a 
rue spatial freouency 
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ces. 
a question 
¡cos but also a question of reaching results. We Here ;■ 
Л.г.Ь.г 
want to get 'a lot of Information f'oi 
for different fields, e.g, phi 
interpretation of ecological problems. 
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Li earl у distinguishable details are necessary for ail 
kinds of interpretation as for mapping as for agri 
culture, geology or hydrology. Therefore we must kno# 
which factors of influence are objective for gcoD c> 
oao distinguishing of details. 
Basis for the foi lowing Descnptio 
ipliOn i! 
i m a n eye. 
isyecidii• 
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г. - Г 1 •- r. p •. •. ¡0 K n -, r, i •. n *• "h . 1 rt *. r + t Г/ rv. v n Г f*. *. n r-. 
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and reproduction of detail 
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15. in a practical way we 
chose parameters which influence the 
transfer of information of the system; target - human 
eye; 
1 true spatial frequency of the target according to 
its real geometrical structures and its spectral 
absorption in relation to the surround 
2 modulation transfer of the used lens depending on 
the spatial frequency 
3 modulation transfer of the used film depending on 
the spatial frequency 
4 effective Un film reproduced/ spatial frequency 
5 conditions for viewing the film depending on the 
frequency character of the human eye 
Now we should answer the question how is the inter 
action between the described parameters. 
224 
possible to approximate rather simple 
geometric shapes, we can say that real targets have 
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buuj Si «pit yase ы." yclui • 
as a special shape o? rectangle, In this case we get 
the true spatial frequency 
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:-pt 
target m mm) A special kind are targets with frame- 
shaped structure, m mis case 
the frame, For ellipse and circle the above equation 
is changed to 
R"=!/d 
Id - diameter of circle or shorter axis of ellipse) 
Circles with frame-shaped structure have a true spa 
tial frequency calculated after eq.l. 
2. nodulation transfer of lens 
To characterize an objective it is not possible to 
take only one modulation transfer function, Therefore 
we make a compromise and use the modulation transfer 
function which describes a beam in a distance of 33mm