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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