NUMERICAL PHOTOGRAMMETRY IN 
RAILWAY DESIGN AND CONSTRUCTION * 
Dr. J.M. Zarzycki, P.Eng., 
Chief Engineer, Engineering Services Division 
Canadian Aero Service Ltd. 
Ottawa 4, Canada. 
INTRODUCTION 
In Canada, photogrammetry finds extensive application in the loca- 
tion, design and construction of railways. Rapid development of natural resources 
has demanded that railways to new mining sites be engineered and built economically 
against urgent schedules. These projects offer a particularly broad field for the 
application of photogrammetry because the construction of new mine sites and new 
railways takes place, in most instances, in unsurveyed and difficult areas. There- 
fore,photogrammetry can be used in all phases of railway engineering from prelimi- 
nary reconnaissance surveys to construction surveys and preparation of as-built plans. 
This paper will deal only with the application of numerical photo- 
grammetry to railway engineering. It will discuss methods developed at Canadian 
Aero Service Limited which bring together ground surveys, photogrammetry and 
electronic computations in a single, integrated operational system. 
The first step toward the use of numerical photogrammetry in a 
variety of engineering problems was the construction of precise stereoplotting instru- 
ments which made possible accurate measurements of x, y, and z co-ordinates in a 
stereo-model. This method, however, did not find much practical application because 
of the time required to read and write down the co-ordinates and because the numeri- 
cal data had to be handled manually. 
The practical application of numerical photogrammetry became 
economically feasible with the development of the electronic co-ordinate printers 
which automatically punch co-ordinates on tapes or cards and with the wide use of 
high speed electronic computers for data processing. The combination of photogram- 
metry and electronics has made it possible to carry out precise measurements and 
perform computations much more economically than by ground survey and conventional 
computation methods. 
1. MAJOR APPLICATIONS 
  
Numerical photogrammetry, combined with electronic computations, 
is applied in the following stages of railway engineering: - 
(2) In the location stage, to determine position of a number of points close to the 
probable location of the proposed alignment. These points are determined to minimize 
the field survey work. They replace conventional traversing between the basic control 
  
points established by Tellurometer surveys.