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.
