GENERAL SUMMARY REPORT OF COMMISSION VII 
TABLE A 
PHOTOGRAPHY USED FOR INTERPRETATION 
Type of Interpretation 
Photography used 
Surface configuration, Drainage, The widest variation occurs in this field. In general, preferences seem 
Soils, Geology to be: 
1/40,000—1 /60,000 for broad area classifications 
1/20,000 for more detailed study 
1/10,000 and larger—spot supplemental coverage in black and white 
or color. 
Vegetation Various scales, mostly falling between: 
1/20,000-1/40,000 for general study. Pan film usually specified. 
Special films and filters sometimse used. 
1/10,000 for detailed study, tree crown measurement, etc. Spot color 
photography at larger scales also used. 
Urban, Rural and Industrial 
1/5,000-1/10,000 for detailed analysis; usually black and white. 
Structures 1/10,000-1/40,000 has been used for general classification work on 
large urban areas and regional transportation studies. 
Ice Limited information available. 
1/20,000—1 /40,000 
conditions. 
recommended for general assessment sea ice 
1/1,500-1/4,000 for detailed study of ice forms. Supplementary color 
photos at larger scales desirable. 
(Note: Obliques have not been listed above. Workers in most fields state that supplementary obliques 
and ground shots are most helpful. No oblique specifications are available in most cases.) 
Note that in table A no attempt is made to 
express regional differences, nor does it list 
the special types of photography which have 
been used in specific projects. For these rea- 
sons it must stand as a general guide only. 
[n addition to his concern with the avail- 
ability of usable photography, the photo- 
graphic interpreter has shown increasing in- 
terest in ways and means of improving the 
information content of photography. Both 
the photogrammetrist and the photographic 
interpreter are, of course, interested in im- 
proving photographic image quality. How- 
ever the interpreter, who wishes to use every 
element of tone, texture and shadow in the ob- 
jects he studies in order to develop the maxi- 
mum amount of qualitative information, 
finds himself particularly interested in the 
characteristic which Macdonald (5) has de- 
fined as *'Interpretability" of a photograph. 
[t is generally agreed that more study of 
interpretability, and methods of improving it, 
is needed. Some of the factors bearing on this 
problem seem to be as follows: 
1. Most interpreters agree that continuing 
effort to provide a greater information con- 
tent in photographs is needed. Yet no satis- 
factory system of measuring and expressing 
the interpretability of a photograph exists. 
The use of resolution in lines per millimeter, 
while reliable and easily understood, is not a 
true expression of information content. Yet 
no fully acceptable substitute has been found. 
2. The interpreter is acutely aware that 
lens and film combinations are normally de- 
signed around the specification of high-con- 
trast resolution targets. However the great 
majority of the photographic image informa- 
tion he interprets exists at low contrast differ- 
entials. He wonders whether a more optimum 
design for his purposes might be achieved 
under revised design specifications. 
The current level of interest in this subject 
is reflected in the fact that two of the Com- 
mission VII papers to be presented at the 
1960 Congress deal with phases of the inter- 
pretability problem. 
EQUIPMENT AND TECHNIQUES 
Photographic Interpretation instruments 
may be divided into three broad categories: 
viewing equipment, measuring equipment, 
and equipment devoted to transfer and re- 
cording of detail. Many instruments have 
more than one of these capabilities. Interpre- 
tation techniques are closely related to the 
use of equipment, and can be considered at 
the same time. 
A trend toward greater use of photogram- 
metric viewing and measuring equipment by 
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