:d the degree
y large-scale
he most pre-
ct advantage
ective. Large
metrics, may
same camera as
nportant en-
the objective
esires small-
at any scale
rain and for
'oughout the
necessary for
dmitted that
[here are al-
| if the scale
1eld area the
ited and the
verage.
19 detail dif-
cing relative
n of water-
| finding the
id. tilt angles
nes offshore.
al films and
he difficulty
is somewhat
xposure and
Others have
id rigid spe-
(693)
cifications. Low-level, continuous-strip, image-motion compensation, vertical
photography is used for parallax methods. Smaller scale verticals, precisely
timed, are used for wave methods. Repetitive timed coverage at various tide
heights is flown for water level methods. Other methods in experimental stages
will require still other specifications.
VIII. Advantages and Limitations of Aerial Photography.
The vertical aerial photograph provides a complete, up-to-date near-plan
view of the amphibious objective area. Every visible feature of the area is
recorded on this view, and is thus available for intelligence use, provided the
image can be correctly interpreted. This characteristic of the aerial photograph
is one of its great advantages.
A second advantage is that the entire related area can be examined at once
by means of small coverage. It is possible, therefore, to determine on the pho-
tograph the physical relationship of
natural and cultural features to one
another, even though those features
may be separated by a considerable
distance on the ground. Frequently the
photograph will reveal the “why” of
the conditions that exist. For example,
a ground observer may note that there
is a great deal of suspended silt in the
water immediately offshore of a beach.
The aerial photo interpreter will not à ing
only be equally able to identify this Fig. 10. Vertical aerial photo of a river
silt, but will be able to measure its ex- Miodeh.
tent offshore and along the beach, and
probably to trace it to its source in a river mouth several miles up the coast.
In addition, the photographic interpreter can determine what the direction of
the current must be in order to carry the silt from the river mouth to the
beach, a fact which the ground observer may not as easily discover.
Another advantage possessed by the aerial photograph, is that it makes
possible repeated observation over enemy-held or otherwise inaccessible areas.
Furthermore, these coverages can be planned to occur at a desired stage of
tide, or time of day. During the weeks preceding the Normandy Operations,
the landing beaches were photographed an average of three times each day.
Other types of observation of enemy-held areas usually require occupation of
the area by an observer, and can be made only once or twice during a normal
planning period.
Finally, the photography “freezes” a scene - something which other means
of observation normally cannot do - and brings it back to the expert who is
most qualified to interpret it. The photograph thus obtained can be used over
again, for comparison with earlier and later views and with other sources of
intelligence. And each time the camera’s original, unbiased impression is avail-
able.
Aerial photography has also very definite limitations as compared with
ground observation. The photographic interpreter can never provide as much