Taping a Track

Would the USATF accept a measurement based on an assumption that the curves are circular?

The length-width method of verifying the track length is admittedly imperfect. It does not meet any high standard of accuracy. What it does is to solve a problem for certain LDR races, some of which are held on tracks.

When a track is built, it is normal for a document attesting to its accuracy to be given to the track owner. Many of these documents have been lost.

So, the high school or college knows it has a 400 meter track and it knows that all the paintmarks are where they ought to be. They know it but cannot prove it to anybody. What the standards are for accuracy in high school and college athletics I don’t know.

So, the race director of an LDR run manages to obtain permission to use the track but can’t find proof that the track is what it is supposed to be. The length-width method came about to help solve the problem. Granted, a curb measurement is better, but most modern tracks don’t have permanent curbs. Rather they have sockets into which sections of curbing are installed on those days when a track meet is to be held.

I think that our solution to finding track length could be more accurate, but at a price in time and effort that might make few willing to pay.

I think you could add a relatively easy procedure to give some assurance the curve is circular. You could measure w/2 from the end of the turn (the point used when measuring L) to determine the center of the circle, and then measure from that point to several locations on the turn to make sure the radius is constant.

Also, if W1 and W2 are not equal, I believe the formula underestimates the true length of the track. For small differences of W's this probably results in a very small underestimate, but some limit should be set for the size of (W1-W2) if the formula is used to calculate the distance.

Nevermind that second part. Just realized an underestimate is OK.

First, I'll point out that the article Pete refers to is also available on the USATF site. You can start from www.rrtc.net and choose the Tools for Course Measurers link, then scroll down to More Publications from USATF Road Running Technical Council, then choose How to Tape a Track.

I was the author of the indicated article, but the technique was originally due to Bob Letson. In particular, while the basic idea of measuring a length and width and assuming ideal track geometry is fairly obvious, it was Letson who developed the technique of measuring two widths (W1 and W2) and averaging them. I think this improves the accuracy considerably.

I did a comparison of direct circumference measurement of a track and length-width measurement, described in Measurement News #17 (the June 1986 issue of MN) which is available in the Course Measurement archive Pete referenced. See the article "Measurement of Memorial High School Track, Tulsa, OK" on pages 12-20, describing measurements I did with the late Glen Lafarlette in March 1986. On that occasion, the discrepancy between length-width method and direct curb taping (when using the same tape) was only 8 millimeters. Some points to note:

As explained in my description of the length-width method, the two widths (W1 and W2) should be chosen near the ends of the straightaways, but within the straightaways, as you shouldn't waste time trying to locate exact junctions of straightaway and curve. In that 1986 measurement, we measured along 5-yard lines of the football field. Having a football grid marked in the infield is extremely useful to make sure you're measuring widths perpendicular to the straightaways. Without such a grid to guide you, you'd very likely overestimate the W1 and W2 distances, thereby overestimating the track length.

For marking intermediate tape lengths when measuring across the grass infield, we used a handy technique developed by Wayne Nicoll.

We attempted to locate one of the radius centers in order to check the geometry (to see if the radius was constant as Mark suggested above, and as Pete suggested many years ago). Locating the radius center was far more difficult than you might think. We kept encountering big discrepancies, which we realized were happening because we hadn't located the center correctly. After a number of attempts, we decided it was hopeless, and gave up.

Mark indicated above that the length-width method would underestimate the track length if W1 differs from W2. I think this is correct, but I estimate the amount of underestimate as about:
(W1-W2)^2 / (4*S)
where S is the estimated length of the straightaways, i.e.,
S = L - W
where W is the average of W1 and W2. In that measurement I did with Glen in 1986, the difference between W1 and W2 was about 2.7 cm, while the track straightaway length was about 96 m, so this formula suggests the amount of underestimate as about 0.002 mm (or 2 micrometers). If the W1-W2 difference were as high as 20 cm, the amount of underestimate would still be only about 0.1 mm.

Bob,

I was thinking more about my high school track, which was egg-shaped, when I was wondering about W1 and W2. If the track is a normal shape, and W1 and W2 are within even a couple meters, the track-length difference is going to be trivial and will be an underestimate anyway. For my high school track though, the difference between W1 and W2 was probably 15-20 meters.

I am curious about finding the center of the turn. A lot of things that seem simple in theory and on paper turn out to be a disaster when you actually try to do them for real. Sounds like this might be one of those. I'm going to give it a try next spring.

I recall that in May 1954 when Roger Bannister ran the first under 4:00 minute mile, that surveyors were called in and measured the track. They found it 1/2 inch over the 440 yards thus requiring Roger to run an extra 2 inches! There was no mention of how the measurement was done.

Alan

When we measured the 1996 Olympic Marathon course in Atlanta the Olympic track was part of the course.

David Katz and I were walking around the about-to-be-finished track and wondering whether it would be a productive effort to measure it. I was against the idea because, in the event of an unfavorable measurement, what would we do? The Olympics were only weeks away, and the track was in its finishing stages. I did not welcome the brouhaha that would have resulted from our introduction of troublesome measurement results.

Instead, we settled on bike-measurement as well as acceptance of the official track certificate, which I found to be a somewhat disappointing document. See below.

Hi folks-

The local Air Force base (Goodfellow AFB) contacted me regarding their 1/4 mile (440 yard) track. It seems that the AF is starting to put more emphasis on fitness, and they want to be sure that their track is “accurate”. Since the results of annual PT tests do figure into promotions, they would like some type of certification certificate related to their track length. I would like your feedback on the following items to make sure I approach this issue properly.

1. The track in question does not have a curb (inside lane line only). That means that the best way to measure will be to use the L-W method as described at http://www.runscore.com/course.../Articles/Taping.pdf.

2. Temperature correction for the steel tape and allowable variance between measurements should be the same as noted in normal course measurement procedures (i.e., .08% max measurement difference, 68 degree F temp baseline for tape length, and 10 lbs. of pulling force on the tape).

3. The track should be “certified” for a single lap only, stating that the 1-lap distance is at least 1,320 feet.

4. For a 1.5 mile PT test, it would be appropriate to provide a data sheet that shows the actual start/finish points to equal exactly 1.5 miles on this specific track (i.e., if the measurements show that the track is marginally shorter or longer than exactly 1,320 feet).

Thanks in advance for your comments …

Bill Cullins

Somewhere in somebody’s files on the AFB, there is a piece of paper that got filed. That piece of paper says the track is 440 yards per lap. This paper would solve the problem. Nobody will be able to find the paper, so in order to give confidence that the track is indeed 4 laps to the mile, a measurement is needed.

Bill, when you have done all the things that are needed to do a length-width measurement, you will obtain a number that is close to ¼ mile. It may be a bit longer, or maybe shorter.

I’m not aware that anybody except RRTC uses the length-width method, nor what weight our certification has outside the arena of multilap races beyond 10 km. As far as a 1.5 mile time trial goes, it would seem to be appropriate to certify the length of the track at whatever measured length is obtained, and specify an offset between start and finish that would make the 1.5 miles be consistent with the track measurements.

I'd expect that should the length come out slightly short, the track could be taken as one reasonably accurate, especially for the 1.5 mile time trial, the measurement standards for which are unlikely to be as picky as ours.

I will be measuring a track this morning, and I'm having a crisis of confidence. My helper will be the race director, an inexperienced person.

For years I've been familiar with the "Taping a Track" sheet produced by Bob Baumel. It's a good solution to a tough problem. Note that it is not easy to obtain good taping results by sticking pins in grass. Stout stakes or other immovable benchmarks are needed if taping is to be accurate. In addition, the measured points need to be aligned properly. Misalignment will tend to produce results that are a bit over the real length. Also, the method assumes perfect semicircles at each end of the track, which we do not check.

As I see it, tracks are laid out by people who have better equipment and a more robust measurement method than we have. When we measure an accurate 400 meter track we are certain to obtain a length that is not exactly 400 meters.

At present I think we are supposed to take our measurement and treat it as official, in spite of the fact that our methodology is less accurate than that used to lay out the track originally.

I'm not sure how to resolve this. I wish people did not lose their paperwork.

Today I am going to bring along a Rolatape measuring wheel, which I can read to about 1/20 of a foot. I intend to tape 100 meters on the track to calibrate the wheel. Then I will roll the wheel along the outside edge of the inner line, and from this calculate the track length.

I will have a hammer and stakes as a backup in case what I plan is not possible and I have to do a length/width measurement.