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92 REPORT OF COMMISSION VII
vators, dredges, storehouses, and open air storages areas usually will require the
use of large scale photography (1/10.000 to 1/5.000), whereas most other port
and harbor photo interpretation can be done adequately at scales of approxi-
mately 1/20.000.
Amphibious Photo Interpretation. This type of interpretation becomes of
the greatest importance when information is needed for landing and embarking
purposes and for the defense of coastal areas either from the sea or from the air.
For these purposes the following elements should be pointed out on the photo-
graphs:
1. elements relating to hydrographic conditions along the coastal area under
consideration; 2. elements relating to the coast line itself; and 3. elements relat-
ing to the immediate hinterland. Considerable information can be obtained di-
rectly from the photographs relative to elements 2 and 3 above such as orien-
tation and line of the coast, nature of the beach, sinuosity, suitable landing
beaches, nature and configuration of the nearshore hinterland, communications,
etc. However, insofar as element 1 is concerned, definite data may be supplied
only for such features as reefs, submerged cliffs, sandbars, submarine vegetation
and artificial obstacles. Usually only rough approximations can be made of
water depths. In cases where the water is sufficiently transparent the parallax
method of water depth determination is considered preferable and more con-
venient to use than wave methods or transparency methods.
Airfield Interpretation. In the identification of aircraft from aerial photo-
graphs the use of tables, graphs and other documents is very helpful. Identifi-
cation usually is based upon such factors as dimension, position of wings, num-
ber of engines, structure of tail, dimension of the nacelles, form of the nose, and
nature of gun turrets. In some cases it is very difficult to measure the fuselage
length because of transparancy of the plane’s nose or adverse position of the
plane’s tail. It also is important in aircraft identification to examine shadow
characteristics and to take into consideration light conditions which may alter
the appearance of certain structural details.
Airfield interpretation performed on aerial photographs usually yields all
necessary information as regards: 1. overall shape of the airfield, whether trian-
gular, rectangular or elliptical; 2. ground conditions, whether grassy, arid or
poorly drained; 3. dimensions, orientation and surfacing of the runways; 4.
nature, number and location of airfield installations, such as hangars, revet-
ments, aprons, communication facilities, and navigational aids; 5. antiaircraft
defences, including gun batteries, and radar equipment; and 6. ground defences,
such as trenches, ditches, obstacles, etc.
Tactical Photo Intelligence. The following types of information usually
are needed to meet a tactical military situation; 1. the movement of the enemy:
that is the complex of activities that take place on the fields of operation,
through which men and material are transported from one place to another; 2.
offensive and defensive arrangements: that is all the reinforcing works or in-
stallations in the battlefield which increase the operative capacity of one’s own
troops and at the same time hinder or reduce those of the enemy; 3. logistic ar-
rangements: that is all those installations and plants which supply various ser-
vices, such as ammunition warehouses, gasoline supply dumps, field laboratories,
workshops, sanitary installations, etc. or lodging accomodations for troops such
as encampments, tents, billeting areas, etc.
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