MEERE 
28 
At this stage engineering geology, diamond drilling, and other field investiga- 
tions were being carried out to provide the engineer with the basic information for 
the design of his structures. 
For the design of a dam with its associated features, such as diversion tunnel, 
spillway, aggregate source, access roads, etc., plans at a scale of 1 inch — 25 feet 
or 50 feet with 5 ft. contours would be required. 
However, the mapping of steep river valleys at such large scales is beyond 
the limits of aerial photography. Appreciating the possibilities and capabilities of 
photogrammetric methods it was decided in these cases to replace the aerial camera 
by a terrestrial camera, which could take the photographs from a ground station. 
This development of ground examination from the whole to the part, 
proceeding parallel with the investigation closing in on a definite site, is the story 
he Snowy Mountains Scheme. (Fig. 1.) 
   
   
  
Fig. 1: The three main photo- 
grammetric mapping stages for 
the Snowy Scheme. 
A: For preliminary investigations. 
   
   
4 INCHES — 1 MILE 
    
    
Flying Height 25,000 ft. 
Multiplex Plot. 
TG t 
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N97 27 Ÿ > 
| / ZI m 
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7 
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B: For detail investigations. 
1 INCH — 200 FEET 
  
Flying Height 12,000 ft. 
Wild A7 Plot. 
7/ 5) A | / 
0/08) 
As) 
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2 ¢ 7, , 9 f { 
/ 
  
  
   
= 
     
  
  
  
C: For design. 
1 INCH = 50 FEET 
Ground Survey by Phototheodolite. 
Wild A7 Plot. 
50 FT 
ZLAILLL LEM LL 
  
  
HS 
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A 
N 
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