increased cost of image acquisition, it becomes mandatory that inter-
preter training include the application of the major film and film/
filter combinations and not remain, as at present, centered on pan-
chromatic photography.
The image characteristics of most terrain features or patterns
will vary greatly from one film type to another. If not familiar with
the particular film type available, the interpreter is often required
to proceed through a series of thought processes that translate the
image pattern characteristics of the terrain feature detected on the
unfamiliar film type to the response characteristics of the film type
used in training.
It would seem plausible then, that an inventory of aerial photo-
graphs would be beneficial to the training of image interpreters.
Most training courses begin with a need for examples of cartographic
photography in order that the student gains competency in the rudiments
of photogrammetry, e.g., scale determination, vertical and horizontal
measurements, etc. Later in the training course, when instruction is
provided in the detection and identification of such terrain features
as soil type, species of vegetation, and drainage channels, the inven-
tory will again be called upon to provide aerial photographic examples
of these terrain features. Historically, these examples have always
been provided on panchromatic film because of the low cost and avail-
ability. Ideally, however, these examples should include the four
major film, film/filter combinations employed today, i.e., color, color
infrared, panchromatic, and black and white infrared. To be effective
as training aids, these examples should have been acquired within the
same period of time. Variations in soil moisture, biomass water con-
tent, and sun angle are only a few of the many variables that can
effect the image characteristics, if there is a time lapse between
photographs.
Equipment
The equipment required to obtain and utilize multispectral aerial
photography consists of (1) a camera, and (2) an additive color
viewer. Both aerial cameras and viewers can be acquired on the com-
mercial market and are also available through lease or contract with
a number of aerial photo corporations. 3
Aerial Cameras: In general, multiband aerial gamera systems are
either built-up of four or more single cameras" or consist of a
2 T. Marlar, and J. Rinker, "A Small Four-Camera System for Multi-
Emulsion Studies," Photogrammetric Engineering, Vol. 33, No. 11,
November 1967, pp 1252-1257.
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