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.