50 
3. The surveys of steep rock faces and vertical cliffs, impracticable by manual 
methods, are most suitable projects for the phototheodolite, 
4. The photographs serve as a permanent record for progress stages of 
construction works and have been accepted as a basis for contract pay- 
ments for excavations. 
5. The study of the terrain under a stereoscope is often of great assistance 
for the designing engineer, 
6. Under ideal conditions phototheodolite surveys have resulted in savings 
of up to 80% when compared with the cost for conventional methods— 
notwithstanding the higher accuracy of photogrammetric plans. 
7. Every point of a contour line is actually observed. The shape of the 
ground thus represented is true. 
8. Spot heights, water levels, etc., can be obtained in the plotting machine 
at any desired position within an accuracy of + one or two inches under 
normal conditions. 
Projects surveyed to date by phototheodolite for the Snowy Mountains Authority 
include: 
Power station sites and excavations, both surface and underground, 
Damsites and excavations, 
Shaft and tunnel portal sites, 
Construction camp sites, 
Road locations, 
Land slides, 
River crossing for pressure tunnel, 
Storage areas, 
Quarry sites for earth dam materials. 
Some 50 projects comprising a total of 5 square miles of the most rugged 
areas in the Snowy Mountains have been covered by phototheodolite surveys. Most 
common plotting scales are 25 or 50 feet to one inch, the largest scale being 4 feet 
to one inch with 1 foot contour intervals. A total of approximately 1,000 stereo 
models have been plotted. 
Special Applications of Phototheodolite Survey 
In addition to the above plans prepared for the various construction sites 
particular advantages of the phototheodolite were utilised in a few special applica- 
tions. Some of these are perhaps described for the first time. 
  
Fig. 2:Part of the road after construction, demonstrating type of terrain. 
l. Roads 
An experiment was made for road location along a steep slope partly consisting 
of vertical rock faces. The surveyor, assisted by one chainman, took the photo- 
graphs within 2 hours fieldwork and returned with detailed survey information 
covering 33 acres of extremely rough country. 
During plotting at a scale of 50 ft. — 1 inch with 5 feet contours a number 
of natural features which could be seen on the photographs in the approximate 
i vicinity of the proposed road were incorporated in the plan and marked on the 
photographs with corresponding numbers. 
After the road had been designed on this plan, the engineer took the plan and 
the photographs and positioned himself on the base from which the photographs 
had been taken. On the other side of the river where the designed road had to be