POSSIBILITIES OF AERIAL PHOTOGRAPHIC SURVEYS. 
The Possibilities of Aerial Photographic 
Surveys for Forest Purposes.” 
By OWEN JONES, Chairman Forestry Commission, Victoria. 
This matter is one which came under the notice of my Commission. 
through the Institute of Science and Industry, 4s the result_of certain 
suggestions by a Mr. H. E. S. Melbourne, of South Australia. As an 
ex-pilot myself, with some experience of aerial photography, and some 
knowledge of the enormous services rendered by it during the war, I was 
naturally attracted by the proposal, and on considering it more closely 
it seemed to me to be one that might well interest the present conference, 
and provide profitable matter for discussion. 
In putting this subject before you, I can, perhaps, scarcely do better 
than to state the case largely in Mr. Melbourne’s own words. 
Photography has been used for many years on topographical surveys 
and reconnaissance work in mountainous countries, and has proved very 
successful there; but extensive use has not been made of it in level 
country owing to the difficulty of obtaining suitable camera stations. 
This difficulty has now been overcome completely by the aeroplane, and 
owing to the great ease and accuracy with which vertical photos. can 
now be taken, a purely plane survey can be carried out without having 
known camera stations at all. Photos. can be taken from any height, 
giving negatives on scales varying from 200 to 5,000 feet to 1 inch, and 
from these enlargements or reductions can be made at will without affect- 
ing the accuracy. With the special cameras in use, a plane surface can 
be photographed with absolute accuracy, but ‘hill features are liable to be 
slightly distorted near the edges of the negative. This can be very largely 
overcome by selecting suitable view points, and by taking special photos. 
over particularly steep slopes. It is, therefore, possible to take a series 
of photographs from the same or different heights, and to join up the 
prints to form a complete photographie map to any desired scale. 
Almost any natural or artificial feature shows up on an aerial photo- 
graph, more or less distinctly, according to the light and shade effects, 
and very little practice is required to distinguish the different ‘features. 
An airman ean photograph country as quickly as he can fly over it, 
and as the speed of a plane, as a general rule, is anything over 60 miles 
an hour, it will be evident that a very wide extent of country can be 
covered in a very short time. The movement of the plane does not 
affect the photos., as during the slowest exposure (1/100 second) the 
plane only moves about 1 foot at the above speed. In Egypt and 
Palestine, complete maps were made during the war of hundreds of 
miles of country which was formerly quite unmapped, or nearly so, and 
on all the fighting fronts a great amount of detail, such as trench 
systems, fortifications, &c., was filled in on existing maps with an 
accuracy which the draughtsman cannot question. a 
* Read at the Hobart Forestry Conference. 
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