REPORT OF COMMISSION VII 
GVII-17 
killed, volume of timber, location and concentration of infested timber with 
comparative photography to study changes. 
Aerial photographic tests are made for detecting damage by the white pine 
weevil (Pissodes strobi (Peck), the spruce budworm (Cacaecia fumiferana Clem.), 
and the southern pine beetle (Dendroctonus frontalis Zimm). Also large aerial 
color photos were taken in 1951 of a number of blighted areas to establish a 
visual record for studying the intensification and spread of the disease. 
Photo mensuration studies in second-growth Douglas-fir forests are designed 
to meet forest management surveys. Species identification and volume estimates 
on aerial photos are the objectives. Study is made on 1:10,000 or 1:12,000 
scale photos. The photo interpretation techniques used include light tables, 
Walthen lens stereoscope, ¿-acre plot overlays, crown diameter scales and 
Abrams height finder. 
In the northernmost part of Sweden, certain jobs have been executed con 
cerning the parcellation of forest land where photo interpretation has been used 
for the photogrammetric mapping, and for the assessment and classification of 
the forest soil. It has proved advantageous to use a helicopter for checking the 
photo interpretation. The experience of this work is favorable. It will probably 
be possible to report the results at the beginning of 1956. 
The Swedish Committee on Forest Photogrammetry, appointed in 1948, 
has a considerable sum of money set aside from the Fund of Forest Research, 
for research work in 1955 to 1960. The purpose is to study the possibilities for 
rationally exploiting aerial photographs in Swedish forestry. Thanks to this 
committee much research, training and service in the field of photo-interpreta 
tion has been achieved. In 1953 a bulletin from the committee was published, 
“Mapping of Forest Stands from Aerial Photographs,” by Nils Hagberg. 
Recently a book on photo-interpretation (Tolkning av flygbilder, 157 pages) ap 
peared. For the present there is a study into the most satisfactory photographic 
scale. 
No organized research works are carried out in Norway, but a few sparse 
investigations are made. The first trial of classify ing forest stands is now under 
way. A committee is at work studying these questions, taking into consideration 
a special research institution and a more organized activity in this field. 
In Canada studies are in process on large-scale photos for the purpose of 
examining the accuracy of measuring average heights of dominant and co 
dominant trees, to study crown cover, preparation of photo volume tables, and 
the accuracy of estimating photo volumes. Tree species, tree heights and stand 
densities are determined from photos. The equipment used includes parallax 
bar, modified Zeiss binocular stereoscope and density scales. Accuracy standards 
are set at 10 per cent at .95 probability. 
The National Research Council of Canada has cooperated in a program con 
ducted by Purdue University of Lafayette, Indiana for the Corps of Engineers, 
United States Army. The purposes are: to extend the range of arctic and sub 
arctic airphotosoil patterns to include terrain conditions found in Northwest 
Canada, to obtain field data on some of the soils and permafrost in northwestern 
Canada (the patterns that these soils present on aerial photographs are being 
studied and analyzed with respect to the field data), and to further develop 
methods of using airphotos to identify and evaluate significant characteristics 
of terrain conditions that influence engineering operations in the arctic and 
subarctic. 
In Britain, in collaboration with the forestry commission, Hunting Aero- 
surveys has been conducting experiments to investigate the possibility of differ