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The interpretation of vegetation is another case in which procedures may
vary from area to area. Colwell (5) points out that the use of special film/filter
combinations is particularly applicable to interpretation of vegetation, since the
identification of a particular vegetative type may depend on a predictable dif-
ference in reflectance characteristics of the vegetation. Specific film/filter com-
binations may be selected to translate these differences in reflectance into detec-
table tone changes on the black and white print.
Therefore, it is quite likely that an interpreter working in the South Pacific
might be using one specific film/filter combination, and following a prescribed
procedure in analyzing the tone of the vegetation in the coastal zone, while
another interpreter in the sub-Arctic might be using an entirely different tech-
nique to identify vegetation in his area.
V. Equipment used in Amphibious Photographic Interpretation.
Equipment used by the amphibious photographic interpreter varies little
from that used by his brothers in other fields of photographic interpretation.
For depth and height determination by parallax methods various types of pho-
togrammetric stereoscopic viewing equipment using the “floating dot” principle
are employed. For more general visual and metrical analysis of coasts and
beaches the interpreters’ basic equipment consists of:
1. A pocket stereoscope.
One or more simple monocular magnifiers
A measuring scale.
A pair of dividers.
A slide rule.
One or more wax pencils for marking photos.
A pair of scissors.
Various expendable supplies, as cellulose tape, etc.
9. Basic PI reference manuals.
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Additional equipment of one kind or another is considered desirable by
certain photographic interpreters, or is required for various special conditions.
Such items may include among others.
l. Proportional dividers for transferring distances from photo to
map.
2. A parallax ladder for height determinations.
3. A “road runner" for measuring distances along winding roads or
curved beach lines.
4. Drafting equipment for making beach maps.
5. Various plotting devices for making measurements on oblique
photography.
Many military photographic interpreters, at least in the United States,
prefer a scale graduated in thousandths of a foot rather than in the millimeter
graduations used by many photogrammetrists; and the amphibious photo-
graphic interpreter is no exception. Use of 0.001-ft. units enables a simple
ratio to be established between the measurement as read and the distance on
the ground, once the representative fraction indicating the scale is known.
Thus, for an RF of 1/8.000, each 0.001-ft. increment on the scale equals 8 feet
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