construction and the cross sections of the ground at a particular stage of construction 
progress are compared and the differences computed. 
The final pay quantities program takes into account the design 
criteria and calculates only cut or fill which was done within the design specifications, 
Fig. 9. In addition to the quantities, the program provides a listing of: - 
(a) the profile grade deviation, i.e. difference in elevations between the final 
finished grade and the design profile grade. 
(b) the closure difference, i.e. the difference in elevations between the final and 
the original survey at the farthest x offset of either the original or final surveys. 
In addition, there is a complete tabulating system which allows for 
the individual calculation of rock and earth quantities, totals between different stations 
and totals on different sides of the center line. 
These computing programs are designed to use cross sections 
obtained either by photogrammetry or by ground survey methods. This feature is 
important because sometimes it may be impractical to obtain aerial photography, 
and the cross sections must be obtained by ground surveys. In the computations 
these data must be integrated with the cross sections obtained photogrammetrically. 
As a part of the overall quantities computation program, a sub- 
routine is introduced which in the same operation provides Dataplotter cards designed 
for the Electronic Associates lineplotter. From these punched cards the following 
information is plotted automatically: - 
(a) the cross section of the ground before construction 
(b) the cross section of the finished grade 
(c) the design cross sections modified for the maximum pay line allowance. This 
graphical presentation is valuable to the railway engineer as it enables him to review 
the constructed grade and embankments and compare them with the design. 
6. PRACTICAL RESULTS AND CONCLUSIONS 
Every method of performing measurements or any other engineer- 
ing operation must be evaluated from the point of view of accuracy and economy. 
These two factors cannot be divorced from each other in any critical evaluation. 
The use of numerical photogrammetry in highway and railway engineering must be 
considered also in the light of the overall design and construction program. There- 
fore, it is always advisable to discuss the uses of photogrammetry and electronic 
computations with the design engineer and the contractors so that a standardization 
of as many phases of the project as possible can be achieved in advance. This 
collaboration leads to using the most advantageous methods for the overall success 
of the undertaking. 
To determine the accuracy of the profiles obtained photogrammtri- 
cally, elevations of 211 points were surveyed an the ground over a seven-mile long 
section in Northern Quebec. About half of this was gently rolling terrain; the remain- 
der was rough country. The checks revealed that the mean square error of the 
elevations obtained photogrammetrically is - .12 ft. (* 0.04m). This is equivalent 
to 1/15,500 of the flying height. The maximum error in elevation was 0.3 ft. (0. 09m)