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Mr. M. A. Mathieu of France: In addition to the applications of photogra 
phic interpretation to forestry which have already been discussed, has any use 
been made of photography in planning access roads to forested areas? 
Mr. Losee, Canada: We use aerial photography to a great extent in Canada 
for road location, for campsite location, and for assessing the capacity of rivers 
for transporting timber. This has been going on for many years and has reached 
a state of acceptance where the practical workers—road foremen and the like— 
will not begin a project without aerial photographs. 
Mr. Rogers, U. S.A.: In the U. S. photos are also used intensively in forest 
road planning, particularly in planning permanent road systems. I wonder if Mr. 
Massie would care to comment on the work of the U. S. Forest Service along 
these lines. 
Mr. E. Massie, U. S.A.: I have been very impressed with a lot of the papers 
and illustrations seen at this session. Many of the illustrations show forests 
which, by our standards, are substantially open stands. Much of our timber in 
the United States is in dense stands and under certain conditions road location 
by standard ground methods have required ground crews two field seasons. In 
one of these cases the entire centerline of the road had been surveyed but before 
letting a contract for construction we were asked to review the proposed route 
on aerial photographs. On studying the proposed route it was found that a bad 
slide area was crossed. This condition, of course, would result in expensive con 
struction and high maintenance costs. Hence we were requested to relocate this 
road using photogrammetric methods. This was accomplished over a six week 
period by comparison with two years employing standard ground methods. 
Our normal procedure in the execution of road work by photogrammetric 
methods is first to make a preliminary reconnaissance using a good topographic 
map, if available. In the event that such a map is not in existence small scale 
aerial photographs are employed in a stereoscopic plotter to determine various 
possible locations. These several possible locations are then reviewed by a road 
engineer who will select the most probable route or possibly the most probable 
route and one or two alternates. The route or alternate routes are then given 
further photogrammetric study by use of the Kelsh plotter and medium scale 
photography to be assured that grades and alignment required by the road 
specifications can be maintained. From this review the final proposed route is 
determined. 
The photogrammetric work is used as the base on which flight lines are 
planned for procuring large scale photography. The most acceptable photographic 
scale for our purposes appears to be 1:10 000 utilizing an 8 1/4" focal length 
camera. A longer focal length lens would be more desirable in order to avoid 
exaggerated displacement of images caused by tall timber on steep slopes. Also, 
because of the density of timber the longer focal length lens would make it 
possible to see through the timber to the ground more often than when a short 
focal length lens is employed. Because of the lack of satisfactory long focal 
length cameras it has been necessary to employ the 8 1/4" lens. 
Utilizing the 1: 10 000 scale photographs, which consist of one flight strip in 
width placed over the proposed road route, a narrow band of topography is pro 
duced in the Kelsh plotter. The result of this work is a strip of topography 
varying in width from approximately 300 ft. on tangents to 700 ft. in isolated 
areas as required by road curvature on a scale of 1: 1200 with 5 ft. contours. 
This topography is used as the base on which the road is designed and quanti 
ties computed. 
While this procedure has resulted in expediting road location and design and 
reduced the cost of this work, it is felt that the methods employed are subject 
Discussion