stat paper which was then developed, rinsed, fixed, washed and dried. They also
found the baloptican to be useful for drawing a map to scale from an aerial
photograph. The image was focused on a sheet of paper on the wall of a dark
room and the desired features traced over with a pencil.
On "negative" prints, wooded areas and shadows are white, while open
fields are darker; but for their purposes, Trump and Hendrickson (1949) found
this to be an advantage. During his military photo interpretation experience,
the author used as base maps copies of original photographs dimly printed on
Fic. 4. Aerial photographs may be used
as checks on the hunting and fishing pressures
sustained by certain areas. This view of the Bear
River Migratory Bird Refuge, Utah, shows the
parked cars of hunters who have come to the
public shooting areas to engage in their favorite
sport.—Rex Gary Schmidt, Fish and Wildlife
Service.
Engineering Service, Production and Marketing Administration, showed ex-
cellent detail considering the extensive areas covered. Although the indexes
contained photograph designations, these did not seriously detract from their
use as maps.
DISCUSSION
For getting the most information from aerial photographs used in mapping
or in eväluating wildlife habitat, the author wishes to emphasize the value of
studying the photographs under a stereoscope. The unnatural, rounded, and
tightly hedged appearance of browse species indicative of heavy or overutiliza-
tion of big game range shows up much more clearly when photographs are ex-
amined in this manner. This is true also of such features as topography, drainage
patterns and vegetation types. Certain game species themselves can be identified
more readily and perhaps classified as to sex and age composition when viewed
on stereoscopic pairs of photos. Also, stereoscopic examinations are valuable in
counting such species as ducks or deer partially hidden by trees or other vegeta-
tion. Beaver pond counts made from aerial photographs are often not as ac-
curate as desirable because the smaller ponds may easily be confused with nat-
ural widenings in a stream bed or with spring holes at the feeder heads (Knud-
son, 1951). Beaver cuttings and other signs usually to be found at beaver ponds
would show up much better on good quality photographs viewed stereoscopically
than they would on single prints.
8 PHOTOGRAMMETRIC ENGINEERING
soft matte paper. These permitted
additions of desired details in ink or
pencil but were positive prints.
Schultz (1951), in attempting to
prepare land-use and cover maps of
extensive areas in Tennessee, con-
cluded that a desirable method of
mapping should ''(1) furnish detail
such as is available on aerial photo-
graphs, (2) be applicable to field use,
and (3) favor the economical repro-
duction of a final composite map."
Hefound film positivesof county aerial
photo-indexes used in conjunction
with the ''Ozalid Process" valuable
in making maps. This process is a
means of reproducing positive prints
of maps, photographs, or other items
on papers, cloths, films, and foils of
various types. Schultz found that
county photo-indexes, available
from the Aerial Photographic and
