40 REPORT OF COMMISSION VII
and bare ground or rock. Difficulties of detecting snow cover beneath stands of
trees are satisfactorily overcome by the use of color film, and presumably an
experienced interpreter with good quality black and white photos could use it
about as well as color.
6. WILDLIFE AND RECREATION INVENTORIES
The inherent difficulties of making adequate inventories of wildlife by ground
survey methods has led to rather widespread adoption of aerial photographs
as aids. At present obliques are most commonly used, and they have been found
especially helpful in connection with census surveys of waterfowl and big game
such as deer and antelope.
Stereoscopes are used to some extent in making counts of flocks or herds
seen on the photos when overlap is provided; but counts on single obliques are
aided by enlarging the contacts, and using a magnifying glass. A special scanning
device for use in making estimates of numbers of waterfowl has been introduced
(Kalmbach 1949), but many techniques in both the procurement and the use
of photographs remain to be crystallized. Some work currently being done in
California has indicated correlations between vegetation classifications made on
aerial photographs, and deer populations. By close interpretation of kinds and
densities of vegetation, and topography (with the aid of a stereoscope), the
amount of ground work can be considerably reduced, and more accurate data
can be obtained. Even on 1:20,000 scale photographs, it was found that areas
of heavily browsed shrubs could be detected, leading to location of deer concen-
tration areas.
Recreation areas are not subject to inventories as are most other resources,
but aerial photos do play a part in special surveys made for their location and
development. With a minimum of ground work, recreation planners can. make
photo studies of vegetation types, locate areas topographically suited for camp
grounds, locate roads and trails, etc. Government agencies such as the National
Park Service and the Forest Service make use of low altitude oblique photographs
as well as verticals and mosaics.
There is a growing demand from private individuals for aerial photos of
areas they plan to visit for recreation purposes. The photos aid the selection of
routes of travel and camping sites, and add over-all interest to trips. Fishermen
use photos to find access to lakes and streams, and mountain climbers use them
to select routes up peaks. Colwell (1950) points out numerous other practical
uses of photos in the field of recreation.
FUTURE UsEs OF PHOTOS IN NATURAL RESOURCE INVENTORIES
All indications point to a continued and expanded use of aerial photographs
in inventory work. Part of the problem of putting them to increased use is one
of education. It is known that many users and potential users employ inadequate
or even erroneous techniques. They must learn the principles of photography
and photogrammetry, and they must learn the values and limitations of photos,
in order to put them to their fullest and best use. The increasing number of
courses in photogrammetry which are being offered to students by the univer-
sities today will do much to correct past weakness. As trained students enter
the fields of engineering, geology, forestry, biology, and the many other fields
which make use of photos, they will be bettér fitted to cope with the technical
problems of interpretation and photogrammetry peculiar to their work. Con-
tinued research by government agenciés, schools, and private companies and
individuals, will point the way to new and more efficient means of applying aerial
photos to inventory problems.