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BOUSKY 
It is considered as self-evident that the aspect of real importance 
in the interpretation of recorded detail lies with the characteristics of 
the ground detail itself. It will be useful, therefore, to examine some 
basic characteristics of the ground image from this standpoint. The 
three to be considered here are: 
(1) The size of detail and detail patterns on the ground 
(2) The contrast of this detail 
(3) The illumination range 
DETAIL SIZE 
The photo-interpreter often uses the criterion of SCALE as indica- 
his ability to identify certain detail types, keys, patterns, Or 
is actually a term that repre- 
It is defined as the ratio of 
tive of 
configuration sizes on the ground. Scale 
sents the photographic magnification. 
distance on the photograph to the actual distance on the ground. But 
to many photo-interpreters who have been in the practice of evaluating 
photographs of a standardized format size with an unintentionally 
¢¢standardized’’ poor quality, scale has gained a significance in terms 
of interpretability never anticipated by its definition. Even though the 
present photographic quality may be vastly improved over that of his 
past experience, and even though this improvement will provide him 
with more recorded information and better interpretability, the photo- 
oneously specify what he thinks he wants in 
interpreter may still err 
ize on 
terms of scale rather than in terms of what he has to recogn 
the ground. 
A more fundamental parameter influencing the recognition of ground 
detail is the actual size of the detail on the ground, since this is not 
affected by variable standards of photographic quality. The sizes of 
detail involved in interpretation of aerial photography may be con- 
veniently categorized into six basic groups in terms of detail size. 
These are indicated in Figure 1. The class divisions are made on the 
basis of lineal detail dimensions in feet, and are based upon minimum, 
or threshold, recognizable detail sizes on the ground. Such class 
groups are both useful and significant in appraising photographic sys- 
tems and missions. The nominal object sizes are convenient for group 
range identification whether recorded at an altitude of 1,000 feet or 
1,000 miles. 
Generally, the 500 and 200 foot classes are primarily useful for 
while the smaller sizes are most significant for 
cartographic purposes, 
e is appreciable over- 
detail reconnaissance, although, of course, ther 
lapping. For military use, other class names are used and other kinds 
of detail may be important, Those listed in Figure 1 are primarily to 
present the pattern of class distinction and are to be considered only 
AT 
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