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REPORT OF COMMISSION VII 41 
There is a need for more work in the field of photography, in order to produce 
higher quality photos for the interpreter's use. Tone control, for example, is a 
definite problem. Photo projects vary considerably in quality, as we all realize. 
If the prints from various projects could be made more uniform in tone, accord- 
ing to some standardized scale, it would be of great aid in the interpretation 
of vegetation, soils, and other features. Better quality prints, from the stand- 
point of resolution, details in shadows, elimination of hot spots, and other char- 
acteristics which hinder interpretation, are sorely needed. Some beautiful photog- 
raphy has been and is being produced, but unfortunately not all projects are of 
the highest quality. 
Color photography is being tried out at intervals for various resource in- 
ventory jobs. In many cases it provides badly needed detail, but the techniques 
and costs of its use deter its widespread adoption. Advances in color photography 
over the past several years have been rapid, and it does not seem unreasonable 
to expect that its further improvement and increased use will come in the years 
ahead. 
Photo-interpretation of resources does not call for elaborate and costly in- 
struments. A simple lens stereoscope is the interpreter's primary tool. The 
folding pocket type, and those mounted by jointed arms to a masonite board, 
are handy for field use. There is conceivably room for improvement of those 
used in offices, however, to make the interpreter's work more comfortable and 
more efficient. 
Training of students and employees in the interpretation aspects of resource 
inventories must be given more consideration. For technical work, such as that 
involved in forest inventories or soil and mineral inventories, one or two weeks 
of intensive training are required to present basic facts and preliminary instruc- 
tions. That period should be followed by weeks or months of close supervision 
and checking, depending upon the complexity of the job and the ability of the 
trainee. Instructors must meet the challenge of preparing aids for students, and 
devising teaching techniques which will increase the rapidity and thoroughness 
with which ideas can be grasped, and the accuracy of their application improved. 
'The preparation of comparative stereograms and vegetation keys, for example, 
has been recognized as a valuable aid in many of the fields of resource invento- 
ries. Their wider adoption is to be recommended. Practically all phases of inter- 
pretation work for inventory purposes call for some ground work. Ground ex- 
perience helps the interpreter to recognize the things he sees on the photos, and 
field training in the use and interpretation techniques is virtually a requirement 
for many inventory operations. 
Special equipment and techniques for specific problems need development 
in order to put photos to their fullest use. Snow surveys might be an example, 
where photos are used only to a limited extent, and much tedious and hazardous 
ground work is done to obtain measurements of snow depths and water content. 
It might be quite feasible to eliminate most or all of such ground work by using 
a combination of interpretation and photogrammetry on vertical photos to ob- 
tain snow depths, and obtaining estimates of water equivalents by statistical 
application of the mass of climatological and hydrological records now at hand. 
Current work in evaluating snow cover on photographs by means of photo- 
electric devices is encouraging, and may lead to the establishment of desirable 
techniques. 
In forest inventories, significant recent developments have been made in 
relating stand classifications and measurements made on photos to volumes of 
timber. Improved methods of combining interpretation data with grounds sam- 
pling data by statistical procedures have resulted in reductions in survey costs