Distance races timed to the 1/100 sec

Clarify your issue - I don't get it. Tracks aren't 400 meters, timing systems aren't accurate, or what?

wjc wrote:

Clarify your issue - I don't get it. Tracks aren't 400 meters, timing systems aren't accurate, or what?

Reporting time to 0.01s is misleading because we don't have the accuracy in timing or tracks to truly compare performances to that level of precision.

Even two athletes in the same race do not run the same distance.

But you can visibly see the difference of one person finishing 0.01 seconds in front of another in a mad dash to the finish in a 5000m race.

So it is worthwhile to time a distance race on the track to the 1/100 sec, especially since the timing device is already in place for the shorter events.

So if you record it that way and ratify the time, you should list all-time performances in the manner in which they were timed.

Hence, Aouita gets listed 0.01 s faster than Moorcroft.

Sort of a foolish question to begin with. In the old days, times were rounded up to 1/5 second increments because of the variations that resulted in hand timing (and the 19th century tradition of using 1/5 second watches).

Finish clocks today are amazingly accurate--and timing to .01 second is actually quite meaningful. Whatever variations there may be in track lengths are beyond anyone's control and actually don't need to be considered.

Final times to .01 tell us alot about the relationship of one finisher to another. If .01 roughly equals 4 inches in a 100m sprint, it is worth about 2.5 inches in a 5 or 10,000. Thus, 1/10th second difference at the end = 25 inches or two feet. You wouldn't have any of this specificity with 1/10th second timing.

An Engineer wrote:

wjc wrote:

Clarify your issue - I don't get it. Tracks aren't 400 meters, timing systems aren't accurate, or what?

Reporting time to 0.01s is misleading because we don't have the accuracy in timing or tracks to truly compare performances to that level of precision.

much clearer

In picking places all the help is welcome same track same system same operator going to the 1/100th line on the photo is fine to sort out places. Everyone has the same conditions. But in ordering a list with entries from various tracks, systems,operators and readers I think that to the 1/10 is all we should report for distances over a mile. Unless they were in the same race and one was picked over the other times reported to the longer full tenth should be counted as equal performances.

Timing systems record down to 1/1000th of a second. Check out what happens when a sprinter record the same time as another.

Let's hope you aren't en engineer.

The timing technology is as accurate to as many significant figures as you want to have on your published results. So the timing precision isn't limited by the equipment, it is limited by the methods of finishline determination. The clock starts at exactly the same time that the gun is fired. The clock stops when the runners torso crosses the line, and that precise moment is determined by a examination of the finishline photos.

The conventions used for examining photo timing are accurate down to 3 significant figures, however, we only report two.

Tracks are either certified or they are not. The path that a runner takes during the course of competition, and the actual distance that he or she actually runs is irrelevant, and has nothing to do with the accuracy of the timing devices and the conventions for reporting the times.

With that said, reporting races down to two significant that are not photo-examined (Xc races) is stepping outside the boundaries of precision. In those instances, the precision is limited by the methods of time-determination, whether it be human, or chip. It should be obvious that a chip affixed to someone's shoes does not determine when their torso crosses the line.

Yes we can. Both performances were measured with technology as accurate to as many places as you want to be reported. The photos are examined with conventions that are accurate down to 3 significant figures, and are report to 2. Aouita ran faster than Moorcroft.

If you take a handheld stopwatch and time an event with it, even thogh your stopwatch is accurate to a bazillion significant figures it only reports times down to hundredths of a second. From the time that you start your watch to the time that you stop it, the time that appears on it (1:15:25.62) is accurate. The problem here is that when you start the watch and when you stop it has human fallibility in it at both ends, and there is an implied error in the process that you cannot possibly match the exact time when the event started and you cannot match the exact time when the person you timed actaully crossed the finishline.

START.

Eyeblink: The human eye blinks 100ms to a visual stimulus.

Reaction time: The average reaction time to a stimulus is about 250ms. You can take all sorts of reaction time tests online and see where you fall within the distribution.

Sprinters reaction times: generally a good sprinter can consistently get his reaction times down to 160ms. Tim Montgomery hit 110ms once (or was it 101ms?), but most people would agree that race was acatually a flyer in which he just happened to react slower than the allowable 100ms

With that said, legal reaction time in our sport is 100ms, which matches your eyeblink reaction time. Our sport has determined at hand-timed races be adjusted by 240ms which conveniently duplicates the reaction time of most people.

I bet racks can be 1/4 inch off per lap and still be certified accurate. At 5,000&10,000 that is about 3 and 6 inches if I did not fup the kiddy math.

I do not think you can be sure a 30;00.02 from Weldon in Abidjan is slower than a 30:00.01 from Robert in Yokohama.

Another engineer here. To give you a feel of the duration of .001s: it takes that long for Usain Bolt to cross about 1/4 of the width of the painted finish line.

Now for technology: If you wanted to, you could record the finish at 4000 frames per second in high def on a digital camera, and even faster at lower resolutions. At 4000 fps, if you play it back at a normal frame rate, it takes Bolt over a second and a half to cross the painted finish line. You'd have a frame for each millimeter of the width of the finish line, and this is for the fastest man ever to grace the planet. We're talking being able to measure the difference in time between when the seam of his uniform crosses the line (the theoretical finish line) and when his body does.

However, you could also take that same camera, point it at the starting pistol, and notice that it takes quite a few frames just for the pistol to fire completely. To get to the ridiculous levels of precision, I think the rulebook would have to get longer to more adequately define the start of the race (such as the moment the pistol hammer strikes) and to further regulate the type of equipment used.

Also keep in mind that the pistol report takes almost .03s to cross the width of 8 lanes of track at sea level, so the difference in time between when the sound wave reaches lane 1 and lane 8 is on the order of 1-2 hundredths of a second, depending on where the starter is positioned. Electronic starting signals from speakers would be a must (not sure if they do this already at the big meets).

To conclude my post in the context of the thread, measuring races to 1/100s and marking tracks accurately to within a centimeter has been well within the limits of technology for decades now. After that it's just proper application of the rulebook.

pjb wrote:

To conclude my post in the context of the thread, measuring races to 1/100s and marking tracks accurately to within a centimeter has been well within the limits of technology for decades now. After that it's just proper application of the rulebook.

Does this allow for thermal expansion of the track on hot days?

ttdotnetty wrote:

Are we deluding ourselves that the 13:00.40 by Aouita bettered the 13:00.41 by Moorcroft? Can we accurately say a 12:59.9 is really different from a 13:00.1.

They are measurably different by the standards of the sport and one time goes in front of the other in the record books. But you seem to want to compare performances, which is more subjective...in this case one can consider pacing, actual distance run (often ignored, but running in lane 2 adds up over a long race), weather conditions, so on and so forth.

T-man wrote:

Does this allow for thermal expansion of the track on hot days?

Rubber tracks are laid down on a paved surface with adhesive, so the entire unit would have to expand and contract on top of whatever base it's sitting on. I'm not an expert on the subject, but I'm fairly confident that if thermal expansion were a problem, you'd see bubbling and buckling instead. This happens on roads too and is a consideration in their design. Think of it like a giant heavy carpet.

Good question, though.

I guess the question is what is the tolerance of certification for a track.

From the 2008 iaaf track and field facilities manual:http://www.iaaf.org/mm/Document/Competitions/TechnicalArea/04/63/93/20080802085950_httppostedfile_IAAF_TF_Manual2008_web-1_4481.pdf

The Competition area for Track Events includes:

- Oval track with at least 4 lanes (400m + 0.04m x 1.22m ± 0.01m) and safety

zones measuring not less than 1.00m on the inside and preferably 1.00m on the

outside

emphasis mine.

The distance around lane 1 measured 30cm from the rail must be greater than 400m and less than 400.04m

Furthermore:

All lanes and start lines shall be measured as indicated in 2.2.1.4. The deviation

from the running length of all start lines must not exceed +0.0001xL nor be less than

0.000m where L is the length of the race in metres.

The previously quoted 400m + .04m requirement for lane one takes care of the lapped races, this one specifies races run in lanes. Taking the 100m as an example, the starting line must be no less than 100m and no greater than 100.01m away from the finish line. For the 200, each lane must be greater than 200m, but no greater than 200.02m from start to finish, with the theoretical running lines measured 30cm from the rail in lane 1, and 20cm from the outside edge of the inside lane line in lanes 2 and up

malmo wrote:

The conventions used for examining photo timing are accurate down to 3 significant figures, however, we only report two.

The 5k times are accurate to three decimal places, with two reported, and contain 5 reported significant figures (13 min 40 sec=780.40 sec). Significant figures are not the same as decimal places. For the purposes of calculating the difference in the 5k times we do subtract, and thus use decimal points, not significant digits, but that doesn't mean significant digits and decimal places are the same thing. Sorry for the pedantry, too many years of chemistry behind me.

Other than the decimal place issue, I agree with everything you wrote.

Does the gravitational pull of the sun and moon also play a role in the accuracy of a 100 meter race?

Wind plays a much bigger role than .001 or whatever. a +2.0 is legal just as a +0.1. That plays a much bigger role than the accuracy down to .001.

pjb wrote:

Also keep in mind that the pistol report takes almost .03s to cross the width of 8 lanes of track at sea level, so the difference in time between when the sound wave reaches lane 1 and lane 8 is on the order of 1-2 hundredths of a second, depending on where the starter is positioned. Electronic starting signals from speakers would be a must (not sure if they do this already at the big meets).

This would be even more for a 4x4 relay...where lane 1 and lane 8 start nearly 70m away from eachother....

good thing on the professional level there are speakers behind each runner which guarantee the gun is heard by all runners at exactly the same time....

I almost always agree with you, Malmo. However, I take a few issues with your post.

I am.

Yes. The accuracy of the equipment is not in question here; the question is, what is the accuracy (and precision) of us determining when the start and finish happened. I am not confident that these are accurate to 0.005 seconds, but I would love to see data showing otherwise.

Second, when we talk about world records, then you bring differences in track length, etc into play, which is part of the original question.

There is no such thing as "exact." The clock starts when the gun is fired within some error margin. Now, the margin is small (very small). Anybody know how close it is? 0.1s? 0.01s? 0.001s?

Presumably you mean 3 decimal places (0.001s), not three significant figures?

I'd love to see an example of how photo timing is measured to 0.001 seconds, this is truly fascinating stuff. If we can, in reality, determine that the time of the gun and the finish within 0.001s, then reporting times to 0.01s is reasonable.

I don't wholly agree with this. Within any race, I agree that the real length is of little consequence. In the case of a world record, though, it seems a bit silly to be paying attention to changes small enough that they could be the result of the length of the track. No good solution here though.