480 
SYMPOSIUM PHOTO INTERPRETATION, DELFT 1962 
stages. This project was a joint effort of Tippetts-Abbett-McCarthy-Stratton, 
Consulting Engineers of New York and Aero Service Corporation of Phila 
delphia. Mr Liang served as a consultant in this project. 
Table 1. Photo interpretation in the Quebec Cartier Mining Railway- 
Location Study 
Reconnaissance - First Phase 
Area about 60 miles wide between the coast and the mine 150 air miles inland was examined 
on 1 : 40,000 scale Royal Canadian Air Force photos for feasible routes. Five major alternate 
routes were selected. 
Reconnaissance - Second Phase 
Photos covering area along five major alternate routes were flown at 1 : 50,000 scale. Chain 
distance, sunshot azimuths and barometer readings on frozen lakes were taken in winter 
survey to provide photogrammetric data. Critical areas were mapped with 25-foot contours. 
This topographic information and photo interpretation data are the basis on which route “C” 
was chosen as the best location; the entire route was then contoured at 25-foot intervals. 
Preliminary location 
Photos covering area along route “C” were flown at larger scale for 5-foot contour mapping. 
Preliminary line was located on the map, avoiding insofar as practicable unsatisfactory soil, 
rock and drainage conditions revealed by photo interpretation supplemented by subsurface 
exploration in the field. 
Final location, design and construction 
Line was staked out in field. Geological conditions at tunnel, bridge, and port sites were 
assessed, borrow and aggregate sources investigated, access road located and special problem 
areas revealed during design and construction re-examined with the use of Photo Interpre 
tation. 
The diagram in 1 provides a flow chart of location procedures. Lig. 1 
shows a map of the alternate routes selected by photo interpretation during 
the first phase of reconnaissance. 
Specific conditions affecting route location evaluated 
by photo interpretation 
Illustrations of the various types of information yielded are presented and 
discussed below. These illustrations are selected from projects in which the 
authors have, jointly or singly, been engaged during recent years. 
Soils and geology information in the preliminary location stage frequently 
takes the form of a general assessment of surface materials in a selected corridor. 
This assessment concerns mainly bearing capacity and difficulty of excavation. 
Photo interpretation provides a general evaluation of drainage conditions 
which govern the number and length of bridges and other structures. It helps 
in selecting the most advantageous locations for each structure taking into 
consideration the structure length and its approaches. It also provides clues