Measurement of the Olympic marathon course, Montreal
1976
by R.R. Wallingford
The following article was originally published by the Canadian Track
& Field Association (CTFA) which is now
Athletics Canada (copied with
permission of Athletics Canada). It was written by Ron Wallingford who was
Race Director of the Montreal Olympic marathon and later served as CTFA
Technical Coordinator. This article is of considerable interest in the
history of course measurement as it describes the first measurement of an
Olympic marathon course performed using the calibrated bicycle method.
This was not, however, the fully modern calibrated bicycle method that we
use now. Differences are explained below in commentary following the Wallingford
article.
Note: Norm Patenaude, who rode the bicycle during the 1976
Olympic measurement, died in 1996 when he was struck by a car while
cycling. Norm, who had pioneered ultra distance running in Canada in
addition to organizing numerous road and trail races, was on that occasion
cycling to his home in Orillia Ontario after observing a road race in
Lindsay Ontario.
Due to the very late completion of the ramps leading down to the
stadium (June 26th, 1976), the final measurements of the Montreal Olympic
marathon course were only taken after this date. However, the course had
been measured by a professional survey crew in March 1976, using
blueprints for calculating the connecting ramp distances with the main
road course measurements. Since the telephone company needed to know the
location of the 5 km points in order to plan installation of
telephones used to relay en route information back to the stadium, a
survey crew was hired by COJO (the Olympic organizing committee) to do
this job.
The survey crew followed the basic international (IAAF) rules of
staying one metre from the curb in the running direction and taking the
shortest distance between two points on curved roads. A steel tape was
used for all curved areas and a distomat measuring instrument was used to
record the straight lines. The distomat measures the time taken for a beam
of light to be reflected from the measuring point to its source and thus
measures "air" distance and not the undulations of the pavement. In
several instances, snow had to be shovelled out of the way to accomplish
this feat. It took the survey crew three weeks to complete the task.
The crew inserted nails in the asphalt as bench marks along the course
in several places and appropriately identified these points for us in
drawings for future reference. Unfortunately, one-third of these nails
were occluded by the fresh paving of a third of the course in preparation
for the race before we could use them. The few points we did locate served
as a double check for us when carrying out the actual measures.
The writer as Marathon Race Director, along with Norm Patenaude, an
experienced marathon runner, and Canadian distance runner Peter Quance
formed the nucleus of a team which set up the official measurement.
Cursory exploratory measurements took place using the calibrated
bicycle method, verifying the basic surveyed course except for the stadium
ramp. These preliminary experiences convinced us of the importance of
having an experienced rider (Norm Patenaude) and a first rate bike after
out initial bad experiences. We found that we had to do all our
measurements at night and under police protection. The reasons were that
the air in the tires expanded if we started in the morning and proceeded
during the heat of the day, thus causing the bicycle to lose its original
calibration. In addition, the traffic was too formidable to attempt to go
against it during the day, especially while charting the shortest distance
across curved roads.
Our first task was to get the surveyors to measure the standard
kilometre on a flat straight section of the course. This was measured with
a distomat and then three times by steel tape under the supervision of a
land surveyor. The steel tape measures were 5-13/16"
(14.8 cm), 2-1/8" (5.4 cm), and
2-1/2" (6.35 cm) short of the distomat measures
in a kilometre. The distomat evidently loses this much in the undulations
of the pavement and so is not too reliable for standardizing a kilometre
or measuring a course.
Using the mean of the steel tape measures, we proceeded to calibrate
the bicycle late in the evening and continued through to daylight the next
morning. A Jones Counter, which records 20 counts per revolution of the
bicycle wheel, was employed. Norm Patenaude rode over the kilometre course
three times to calibrate, recording 9359, 9358 and 9357 counts. We then
pegged 9358 counts as being the equivalent of 1 kilometre. We
started in the stadium at the point the surveyors calculated to be the
start and proceeded with the measurement. Each kilometre was duly marked
on the pavement with a spray can, and notes taken as to its location.
After measuring the course, we rode over the kilometre distance twice more
to check the calibration of our bicycle. Our recalibration on the
kilometre course was dead on, being 9358.5 and 9357.5 counts.
Our first result had a discrepancy of 81.8 m with the
surveyors' result. The surveying crew on rechecking their figures found a
discrepancy of approximately 50 m due to a blueprint change
from the original design, leaving their measure and ours about
30 m different. I would suspect a distomat distance to be
approximately 30 m too long if used exclusively due to the
lack of "credit" for undulations of the pavement.
Using our earlier measure as a basis for starting, we carried out the
second official verification measure. Calibration of the bicycle before
course measurement gave readings of 9334, 9334.5, and 9335 counts. We
considered 9335 to be the official kilometre count. Our verification
measure was never more than 3 metres different from the first
one at any of the 5 km points and in fact ended up with an
incredible 8 count difference in 393 890 total counts for the
course. The 8 counts verified the earlier measure by within
0.86 m. Our recalibration was again dead on, being 9335, 9334
and 9335 for three rides taken over the earlier calibrated kilometre.
We were in touch with Ted Corbitt of New York who graciously advised us
as we proceeded with our measurements, and thus ensured more reliability.
We feel that since the bicycle did not lose its calibration and that all
the intermediate check points were consistent, we had an extremely
accurate course.
Other sidelights on the race organization
Because of the numerous intersections (more then 400 on the course), we
insisted on the painting of a 4" (10 cm) blue line. This was
very difficult as the blue was distinct for only so long when painted on
busy city streets. With several patch-up jobs and good cooperation from
the five municipalities through which the race passed, the lines were
ready by race day.
Although the course had several turns it was as flat as was practical
for a race being held in a congested city. The relatively cool day with
comforting rain allowed the quality field to perform up to expectations.
The electrical vehicles used by TV personnel also allowed closer proximity
to athletes without affecting the runners. We had a TV dress rehearsal one
week before with several athletes who had a tour of the course. This
helped us get a preliminary feel for the actual event. As a result, TV
coverage of the actual race was excellent.
Our major problem was relaying times from the early kilometre points.
Even our well-trained specialized time-place recorders had trouble at the
5 km point where the first 34 runners went by in three
seconds. Unfortunately the runners rounded a bend just before this point
which added to the difficulty. Other minor problems were also encountered.
Due to internal problems in COJO, black on red numbers were substituted
for the black on light blue originally ordered. These were not as distinct
on an overcast day as they should have been. Also, the overhead
helicopters involved with the live TV coverage unfortunately drowned out
the voices of the officials at the checkpoints who were reading athletes'
numbers into tape recorders for use in monitoring places.
One electric vehicle had a person to identify numbers on the run and
call them to a recorder. This would have proven satisfactory if the
electric vehicle doing this task had not mechanical trouble.
By having triple checks in most instances the few unexpected problems
did not appreciably affect the total result. The lay-out for refreshments
seemed quite good although not having the expected heat we could not test
the system accordingly. Essentially, every athlete had a potential drink
opposite his number at each refreshment station, with ten numbers per
table.
As a final point, I would suggest that the bell be rung (at least for
the leaders) when they have one lap to go in the stadium. I believe this
would tend to dramatize the last lap, and reinforce earlier instructions
on distance remaining in the stadium.
The techniques described in the above article by Ron Wallingford
differed in various ways from the modern calibrated bicycle method as
used now for measuring road courses. The major differences can be
summarized as follows:
- The 1976 measurement used a multiple sets of marks methodology,
which means that every measurement of both the calibration course and race
course was a "layout" measurement that attempted to produce a course of
desired distance; thus, every measurement generated new marks on the road.
Nowadays, we always use one set of marks, which means that only the
first measurement of a course is a "layout" measurement that
generates a tentative course and produces marks on the road. Every
subsequent measurement generates only numbers depicting estimated
values for the length of the tentative course. (Then, after all measurements
have been performed, a single adjustment is made to correct the course to
the desired distance.) An advantage of one set of marks, aside from less
painting of the road, is that differences between measurements are readily
apparent from the numerical results of those measurements. When using
multiple sets of marks, differences between measurements aren't known until
you go back and measure the distances between paint marks on the road.
Unfortunately, terms such as "shorter" and "longer" may have opposite
meanings when using one-set-of-marks or multiple-sets-of-marks
terminology.
- The 1976 measurers did not share the concern for short course
avoidance which has now become part of course measuring philosophy. In
several instances, they made choices (e.g., steel tape instead of EDM
["distomat"] for the calibration course, bike measurement instead of
survey team measurement for the race course) which had the effect
of producing a shorter course for the runners. Now, the rules require us
to produce courses which are at least as long as the nominal race
distance. Therefore, we always resolve uncertainties by choosing the
option that produces the longer final race course.
- The 1976 measurement didn't utilize any Short Course Prevention
Factor (SCPF). Nowadays, to help ensure that courses are at least the
nominal distance, an SCPF of 1.001 is built into every race course
measurement. Thus, although the marathon distance is nominally
42.195 km, we intentionally apply a 1.001 factor which, in
effect, lays out the course at 42.237 km; i.e., 42 meters
longer than the marathon distance. This isn't really intended to produce
long courses. Considering that some error is unavoidable in any
measurement, the SCPF helps to avoid short courses in spite of the
inevitable errors that always occur when measuring.
- The 1976 course was measured along a path which maintained a clearance
of one metre from curbs. Now we measure a tighter path ("Shortest Possible
Route") with clearance of only 30 cm from curbs. For more
details, see discussion below on Evolution of the
SPR Concept.
- The effect of pavement undulations is probably nowhere near as great
as assumed by Wallingford in the above article. In laying out their
1 km calibration course, the 1976 measurers obtained a
discrepancy of about 9 cm between their average steel tape
measurement and their EDM ("distomat") measurement. Our data suggest
that pavement undulations probably didn't account for more than 1 or
2 cm of that discrepancy. The remainder of the 9 cm
may have been due to random taping errors, calibration error of tape and/or
EDM, improper temperature correction, or incorrect tensioning of the tape.
Even if the entire 9 cm discrepancy in their 1 km
calibration course was due to pavement undulations (which is extremely
unlikely), that would extrapolate to only about 4 metres when
extended to the full 42.195 km marathon distance. There's
no way that pavement undulations could have accounted for the entire
30 m difference between their bike measurement and survey team
measurement
- Although the 30 m difference between bike measurement and
survey team measurement cannot be explained by pavement undulations, it
was nevertheless quite good agreement (Anything within our
one-part-per-thousand SCPF is pretty good). To our knowledge, the 1976
Olympic marathon measurement was the only documented example of a marathon
course measured by both calibrated bike and the older, far more laborious
methods previously used by professional survey teams. This was the first
Olympic marathon course measured by calibrated bicycle and, in this
case, the course was measured both ways. We don't have details for the
1980 Moscow Olympic course, but assume that it was measured using only the
older survey team method. Starting with the 1984 Los Angeles Olympics,
road courses have been measured using only the bicycle method.
The choice of path to measure along a road running course has evolved
over the years. At the primeval dawn of course measurement, the rule was to
measure "one metre from the curb in the running direction" which simply meant
to measure parallel to one edge of the road, on the side of the road where
runners are intended to run (usually the right side in countries where cars
drive on the right; left side in other countries), at clearance of about
1 m from the curb or road edge. There was no measuring of
tangent lines. This path is illustrated in the following diagram:
![[Measuring parallel to one edge, one metre clearance]](images/montreal-spr1.gif)
By the time of the 1976 Montreal measurement, this had evolved so
measurers were following a path closer to the actual path taken by
runners, using tangent lines when measuring between alternating right and
left turns. However, a clearance of 1 m was still maintained
from curbs and road edges, as illustrated in the following diagram:
![[Measuring tangent lines, one metre clearance from curbs]](images/montreal-spr2.gif)
Now, we measure the shortest possible route (SPR) that a runner
can run. We follow all tangent lines and come to within 0.3 m
(i.e., 30 cm or about one foot) of curbs and road edges, as
shown in the following diagram:
![[Measuring tangent lines, 30 cm clearance from curbs]](images/montreal-spr3.gif)
The 30 cm offset from curbs that we use now for measuring
road courses is exactly the same offset as specified in rules for track
measurement. Calculations show that for every 90° turn, measurement at
30 cm from the curb (instead of the 1 m
clearance used previously) alters the path length by about 1.1 m.
The first Olympic marathon course to be measured using a fully modern SPR
was the 1984 Los Angeles course, which was measured by a team of 13
cyclists.
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