WORKING GROUP 9 
MOLLARD 
515 
in volume from a few hundred cubic yards to several hundreds of millions of 
cubic yards. Granular deposits were mapped mainly in connection with the con 
struction or rehabilitation of earthfill dams, highways, airports, and railways, 
and for aggregate in ready- mix concrete fabrication. Sand and gravel searches 
described in this paper are confined largely to the three prairie provinces in 
Western Canada. 
In aerial photographs the surface expression of mapped deposits ranges from 
conspicuous to vague and indefinite. We think it is fair to state that on the 
photos of these glaciofluvial deposits well over half the prospects would be 
overlooked by people with little or no airphoto mapping experience. 
Photo interpretation: an effective inexpensive prospecting tool 
To the investigator in search of sand and gravel sources for some construction 
project, the competently interpreted airphoto is perhaps the best means avail 
able for systematically reconnoitering an area and discovering unknown sour 
ces of sand and gravel. The prospecting phase of a sand and gravel investiga 
tion represents the first in a series of studies that includes searching land owner 
ship, subsurface exploration, systematic testing of the prospect, purchase or 
option of properties, preparation of plans for processing and developing a 
source of supply etc. 
The airphoto tool has many virtues: it is both systematic and economical. 
Large areas can be searched just as easily as small ones. Remote and in 
accessible areas on the ground can be covered in the photos just as quickly 
as the nearby and accessible areas. Trespassing of private property is kept to a 
minimum. Generalized notions of expected quality and quantity can be reli 
ably predicted in most instances. The airphoto tool may indeed be the only 
way of finding small granular deposits that in the field have no conspicuous 
topographic expression, no subsoil exposures and no existing pits. In remote 
areas the task facing the ground investigator without recourse to aerial photos 
is time-consuming and costly. Experience demonstrates that without airphotos 
the field investigator can very easily overlook usable sources of granular- 
construction deposits. 
Procedures followed in mapping granular deposits from airphotos 
Two procedures are commonly followed: one where the photo interpreter 
does not carry out follow-up field work and the second where he does. These 
two procedures will be considered separately. 
Where Photo Interpreter Does Not Field Check His Interpretive Work 
After the boundaries of a search area are determined and the requirements 
of the materials search are known (quantity and quality requirements, intended 
use of the granular materials, governing specifications, and the like) we obtain