it if due con- 
the second is 
rrespondence 
‘pass’ points 
| for 1/50000 
ey Establish- 
rrived at by 
eter readings 
rocedure has 
10ds, perhaps 
and greater 
e air camera 
t subject, an 
traverse and 
an be photo- 
hen demands 
as carried on 
rs and B. W. 
re study, and 
> use of the 
r the cameras, 
is resulted in 
1 experienced 
to 100 miles 
estimated at 
sq. km) over 
0,000 sq. km) 
m radial alti- 
| country like 
ble, the value 
re applied to 
| followed the 
ry Branch, of 
the beginning 
(15) 
In 1929 methods were devised for the satisfactory measurement of tree 
heights from vertical air photographs (Ref. 23). Other investigations for 
identifying species and classification and in the development of mapping methods 
for purely forestry applications have been carried on with success (Ref. 24). 
The Seelyscope, as originally devised for the transfer of forest types from photo- 
graph to map (Ref. 25) has recently come into more extensive use because of 
its application to linear detail of all kinds. 
NON-GOVERNMENTAL MAPPING 
While most of the early developments of photogrammetry in Canada took 
place in the central government offices at Ottawa, a certain amount occurred 
elsewhere. As the subject is becoming of greater economic importance this 
proportion is increasing. The Province of British Columbia has been outstand- 
ing in the amount of investigational work carried on, and amongst this may be 
mentioned the use of small size air cameras by Andrews (Ref. 26). 
Commercial organizations, notably the large paper companies, have deve- 
loped methods for application to forestry purposes, but few published data are 
available. Latterly there have been more activities on the part of air mapping 
companies, using, e.g., the radar altimeter, but little is known of the results. 
In the universities, it is to be regretted that, in general, very little attention 
has been devoted to photogrammetry, despite its great importance to Canada. 
A noteworthy exception is the University of Toronto where for several years 
Professor K. B. Jackson has been conducting a special course on the subject. 
ACKNOWLEDGEMENTS 
The information in this history has been obtained mainly through personal 
contact with men actively engaged in the development of photogrammetry in 
Canada — some of them since its very beginning. Special mention for assistance 
in supplying material is due to R. B. McKay, P.E. Palmer, W. H. Miller, R. D. 
Davidson, J. E. R. Ross, B. W. Waugh, W/C H. Pearce, and Maj. J.I. Thompson. 
R.H.F.