35 
it unsuitable for mapping purposes, was restricted in its application to 
(i) aerial mosaics from verticals (occasionally with enlarged prints), 
(ii) geological interpretation from stereo pairs, 
(iii) special investigations (e.g. river channels at various flood levels, etc.), 
(iv) high oblique photography for records of certain construction stages, 
using F24 as a hand camera, 
(v) training of personnel in aerial camera operation and navigation for survey 
flights. 
Fig. 7: The SMA Beaver 
aircraft at one of the 
regional bases. 
  
Special field investigations connected with high river flows and the fact that 
the complexity of the Scheme presents many variations and alternatives, on. which 
very often a quick decision must be sought, made it highly desirable to have an 
aerial survey camera available at any time. Such a camera, the Wild RC8 which 
is designed for use in small aircraft and which is equipped with.both wide and 
normal angle lenses and capable of high performance was purchased in January, 
1959. During the first two weeks with highest sun altitude normal angle photography 
was secured for plotting purposes. This was followed by wide angle photography 
designed to spread control over the required areas by aero triangulation with the 
Autograph Wild A7. 
Whilst the plotting runs followed the main features of the proposed scheme 
(e.g. tunnel line, roads, and aqueducts) at an average flying height of 4,000 feet 
above ground, the outlay of control strips was governed by existing triangulation 
and possible access for additional field control. Although due consideration was 
given to the general topography of the terrain differences in ground elevation amount 
up to 50% of the flying height for several flight strips. 
Whenever feasible flight lines were directed to visible targets (e.g. prominent 
mountain peaks 20 to 30 miles ahead) to assist in the pilot's navigation. 
Since the photographic season for the mountainous region is very short the 
flight design must be planned to meet possible future extensions and minor 
alterations in the proposed scheme which may be requested within the following 
winter months. This too has been considered by the interlocking system of control 
strips. 
Prior to aerial photography, prefixed signals of various sizes, painted yellow, 
had been laid out close to trigonometrical stations and benchmarks to provide the 
initial ground control. 
Until May, 1959, six films, each containing approximately 200 to 250 exposures 
have been processed in the Authority's Photographic Laboratory. 
(b) Aerial Triangulation 
Before the purchase of the RC8 camera plotting of major reservoirs only had 
lent itself to the application of aerial triangulation.