Foot Locker admits to adding 70 meters to South Regional course

Track Coach-

I agree that what you are using could be considered accurate enough, especially for a sport like cross country. You have a few flaws in your post, and your equipment would be considered inferior to what true course certifiers would use, but you might be surprisingly close, or "substantially" off...without verifying on a calibration course no one will ever know for sure.

Getting back to my initial inquiry - what method did you use to measure McAlpine?

Survey Solutions, LLC wrote:

based on what you just posted and your ".008" figure, even the furthest off measurement in the Illinois State Meet measurement would be "good enough for world records"...are you sure about this figure?

Actually I'm wrong, again my mistake for going off the top of my head instead of my spreadsheet; it's .0008. This is the value you'll see in the procedures guide.

The Jones counter used by the USATF guy was purely mechanical and engaged each spoke as it went by.

I have no doubt that with experience you have become efficient at laying out courses, but I question the accuracy of your methods. What kind of accuracy do you think you are getting with your bike and pedometers? More importantly, how do you know what kind of accuracy you are getting?

DiscoGary wrote:

Survey Solutions, LLC wrote:

Thanks for the response - but how about: How many stakes are used to create a smooth line to measure curves with a tensioned "cable"?? Maybe DiscoGary could pipe in on this as well?

The On Course Ratings Systems guys did not tension the tape around turns. They put some stakes in the ground about 1 foot out from the inside of the turn and laid the tape on the ground in a radius around the turn. I can't find the difference in length between the tape under tension versus slack. It will be small.

You are correct, especially since I read you did the measuring test in the summer when I'm guessing it would be fairly warm in Illinois?

The major flaw in your/their methodology is "They put some stakes in the ground about 1 foot out from the inside of the turn and laid the tape on the ground in a radius around the turn."

The words "some" and "about" are what creates doubt in the accuracy of a measured cross country course, and why measuring errors can easily happen.

Now, I'm totally impressed that there was as much time and effort put into that project as there was, but the differences between your measuring devises could easily be because there was "some" user error or the devices were "about" right, calibration wise.

[quote]DiscoGary wrote:

The Jones counter used by the USATF guy was purely mechanical and engaged each spoke as it went by.

quote]

Are you are about this?

Survey Solutions, LLC wrote:

You are correct, especially since I read you did the measuring test in the summer when I'm guessing it would be fairly warm in Illinois?

The major flaw in your/their methodology is "They put some stakes in the ground about 1 foot out from the inside of the turn and laid the tape on the ground in a radius around the turn."

The words "some" and "about" are what creates doubt in the accuracy of a measured cross country course, and why measuring errors can easily happen.

Now, I'm totally impressed that there was as much time and effort put into that project as there was, but the differences between your measuring devises could easily be because there was "some" user error or the devices were "about" right, calibration wise.

I think you are overestimating the error in measuring the turns without tension. I would be surprised if it was even 3 inches per turn. Just because you can identify an area where the tape measurement wasn't perfect doesn't mean the method is flawed. Every other method has been shown to be inaccurate to a much greater degree. I would be interested to hear what the On Course guys would say about the turns.

We had a USATF certifier there and he went away agreeing that the only way to get an accurate measurement on grass was with a steel tape. He was very dissapointed when he saw how his calibrated Jones counter did on grass. In fact we measure a couple of grass courses together with a tape after measuring the State course, and he never brought out his bike.

It's the best way by far, and I understand that sucks because it takes two people, but I can't help that.

Definitely not overestimating when people on here can be within "two clicks" on a 5k.

Any thoughts on staking down a steel tape over undulating terrain and applying tension? Any thoughts on tensioning a steel tape in segments shorter than the tape length as you should do on twisting trails?

Survey Solutions, LLC wrote:

[quote]DiscoGary wrote:

The Jones counter used by the USATF guy was purely mechanical and engaged each spoke as it went by.

quote]

Are you are about this?

Not 100% sure. It was close to the axle and I'm pretty sure it was mechanical. My data does not show the type of Jones counter used. I remember him telling me that it was the best one made, and it had lots of digits.

It's possible that it only clicked once per revolution. I could find out if it matters that much. This is a guy who certified the Chicago Marathon among other big local races, so he was on his game.

Survey Solutions, LLC wrote:

Thanks for the response - but how about: How many stakes are used to create a smooth line to measure curves with a tensioned "cable"?? Maybe DiscoGary could pipe in on this as well?

Each segment had a stake at the beginning, but the number of stakes on the corners was variable. I'd say 2-6 feet apart based on the turn. Technically you'd call it maybe an octagon instead of a curve. The other place where stakes are necessary were elevation changes, because a drop, dip, or climb. Since we used cut rebar you can use the caps you see at construction site to create a "clip" you slip the cable into.

This is one disadvantage over tape, since tape is marked every inch or centimeter you just measure to the terrain change and call it a segment. The cable only had marks every 10 meters, so if you had a segment that went down, around a turn, and up the other side you go through a lot of rebar. I presume the chain method would face a similar issue. In any case when you're doing 100 meters at a time it's faster than you think.

Since you'd have this quantity of rebar stuck out there running around the second time to double check was no big deal, although if you discover you screwed up you end up moving all the start stakes after your mistake (but the curve and terrain ones are fine). Don't ask me how I know about that.

This process has one big advantage but a similar disadvantage. After you're done you go around and put a cap on the turn and terrain stakes and pound them in. That has the advantage of making it easy to find them the next year. The problem is you pound them in and you can't use them as terrain or curve stakes anymore because the cable/tape/chain isn't going to press against something underground. That said, what you really want is to be able to consistently lay out of course as measured, not necessarily create a course that's easy to remeasure, so rebar in the ground fits the bill.

One last thing, using this process will create a course that's "long" in USATF terms. For example turns on a road course are measured 1 foot off the curb, and a bike or wheel could follow a line similar to that on an XC course. Cable or tape pulled tight to stakes on the inside line do not do that. You could either put the stakes on the line and pull them out so they weren't a hazard, or rig up some 1 foot stand-offs to guide the cable out from the edge. Since leaving the stakes is part of the documentation process removing them makes that harder. Since a standard calibrated ride for a road course would include a short course prevention factor to guarantee the course was at least the advertised length I don't consider this "lengthing" a problem.

Survey Solutions, LLC wrote:

Track Coach-

I agree that what you are using could be considered accurate enough, especially for a sport like cross country. You have a few flaws in your post, and your equipment would be considered inferior to what true course certifiers would use, but you might be surprisingly close, or "substantially" off...without verifying on a calibration course no one will ever know for sure.

Getting back to my initial inquiry - what method did you use to measure McAlpine?

A pedometer and a mountain bike; the course was short, but not by an amount worth discussing. I used to live near the course and know it fairly well. Several years ago, a VA girl ran a really fast time and everyone said the course was short. What she did was lead the whole race, she got the angles perfect and set out to run a fast time. I was photographing the event and have pictures of how she ran it. Kids come to McAlpine expecting to run fast, that mindset is one the keys. At most of the FL regionals, once a kid gets a sizable lead, they back off, but at McAlpine, they want to run a fast time.

Survey Solutions, LLC wrote:

Definitely not overestimating when people on here can be within "two clicks" on a 5k.

Any thoughts on staking down a steel tape over undulating terrain and applying tension? Any thoughts on tensioning a steel tape in segments shorter than the tape length as you should do on twisting trails?

I don't think you can get within two clicks over 5k on grass. That's what we found out.

You can't tension the tape over undulating ground or twisty turns. The modulus of elasticity for steel is 29,000,000 lb/in2 . I don't yet know how to convert that into a delta between a steel tape under tension versus one left slack, but it's likely to be in tiny fractions of an inch.

I understand that we have a lot of people here who have spent a lot of time measuring courses, that you have a lot invested in your methods, and that you can't do what I'm recommending on your own, so the push back is going to be hard.

BUT... the clincher for everyone at the Illinois Measuring Marathon was when the steel tape guys put down the first 600 meters of flags on the starting straight and we could see how straight they were, and I mean you could put your head to the ground and look down the line and see all the flags disappear behind the first one all the way to the first turn, and we knew no one else had a good way of doing that with our methods, and then we asked them to measure back from the 600 meter point and it came to within an inch of the first flag, and then we took our bikes and wheels and GPSs and tried to calibrate them over this 600 meter course which we considered to be the golden standard, and we found out that not only were these methods inaccurate, they were imprecise as well, to a degree that made it clear that all of our other efforts that day would be wasted time and that the tape would give us the best measurement would could ever hope to get... by far.

We wondered about slack on turns, etc, but we also knew that any errors caused by that were negligible compared the errors for the other measurements. We could tell the errors would be in inches instead of tens of yards which is what we were getting with everything else.

Everyone there was a Stat Geek. Believe me, the USATF Jones counter guy went down hard. He did NOT want this to be the conclusion. But the conclusion was unanimous and without qualification or doubt. I guess you had to be there to fully appreciate how convincing it was.

I asked the On Course guys why they chose a steel tape because I knew it had a greater coefficient of expansion than nylon tapes. They said it was for two reasons:

1. The coefficient of expansion for steel is well known so they know how to compensate for it. Data on composite tapes is not as easy to come by.

2. But especially since a steel tape is stiffer and likes to stay straight compared to other tapes. This makes it easier to create smooth curves around turns or over swells when the tape isn't under tension, reducing the error that a more flexible tape would have under the same conditions.

Based on the numbers you posted in your comparisons, it looks like the cheap wheel was off by about 3.822 metres over 600m. Using that as your calibrated working value. Your cheap wheel and gold standard are the same, you just failed to calibrate the wheel.

However, there does appear to be additional under variance with the wheel, because a properly calibrated wheel should show a value longer than the tensioned steel tape if truly stretched in a 600m straight line. There is zero measuring error associated with a properly stretched steel tape, whereas much measuring errors may occur by the user picking up slight ground imperfections (bumps) and the nearly impossible task of roiling a truly "straight" line.

Anyone ever measure the Foot Locker course in SD?

Great Thread! Makes me think that most courses - road and cross country are probably "off" by some amount. I have also heard of tracks being measured incorrectly, especially the steeple distances.

Survey Solutions, LLC wrote:

Definitely not overestimating when people on here can be within "two clicks" on a 5k.

Any thoughts on staking down a steel tape over undulating terrain and applying tension? Any thoughts on tensioning a steel tape in segments shorter than the tape length as you should do on twisting trails?

Still willing to listen to measuring techniques with a steel tape on a cross country course with undulating terrain and numerous turns. Keeping the tensioned tape firm to the ground seems "practically" impossible without stapling the tape to the ground in 6" or less increments on the ups and downs found on many cross county courses.

Math is Easy wrote:

Based on the numbers you posted in your comparisons, it looks like the cheap wheel was off by about 3.822 metres over 600m. Using that as your calibrated working value. Your cheap wheel and gold standard are the same, you just failed to calibrate the wheel.

However, there does appear to be additional under variance with the wheel, because a properly calibrated wheel should show a value longer than the tensioned steel tape if truly stretched in a 600m straight line. There is zero measuring error associated with a properly stretched steel tape, whereas much measuring errors may occur by the user picking up slight ground imperfections (bumps) and the nearly impossible task of roiling a truly "straight" line.

The problem with the wheel was that we got significantly different calibration numbers on the grassy parts of the course versus the firm dirt parts. This made it impossible to calibrate accurately because the wheel's precision would be changing throughout the course in unpredictable ways, and we had no way of finding out what the average correction number should be without measuring the whole course with both the tape and wheel. At that point why do the wheel at all?

The On Course Ratings guys warned us that the time of day would change the wheel measurement as well because of dew on the grass in the morning, etc.

With regard to your second paragraph, I thought the wheel would measure long as well, but it doesn't. The slipping error dominates the straight line deviation error. Maybe if you went reeeeeal slow and put a lot of pressure on your wheel, then maybe you could get a more precise calibration, but who can maintain that discipline over a 5k course? And how would you know you got it right without calibrating over the entire course?

Remember, our wheel measurements were supposed to represent the amateur who shows up with the $50 Home Depot wheel, and then declares that they have "the real measurement". They don't and they never did. They had an approximation good enough for PR purposes which was probably too short.

It comes down to this. If you can't make reliable calibrations which correctly reflect the behavior of your measuring device over the entire length of the course, then that measuring method is inaccurate and should only be considered an approximation. All wheeled devices have this problem on anything but smooth paved surfaces, and GPSs have this problem because many courses alternate between open stretches and wooded areas. GPSs are problematic around turns as well.

The steel tape method introduces errors, but those errors are very small compared to other methods and will be consistent from one course to the next, no matter what the surface is or how much tree cover there is. The error of the steel tape is a couple orders of magnitude smaller than the error for other methods. No matter how you look at it the steel tape is the best way to go.

Father Time wrote:

Great Thread! Makes me think that most courses - road and cross country are probably "off" by some amount. I have also heard of tracks being measured incorrectly, especially the steeple distances.

Every measurement ever reported was off by some amount. The question is, does that amount matter?

For the purposes of cross country course records I would say that most people would tolerate a pretty big error, maybe around 10 meters which is about 2 seconds of running, and still be willing to say those two courses are "the same length". By the time you get to 30 meters difference, everyone will want to do a conversion to compare times.

Our tests showed that other than the tape only the calibrated Jones counter bike could get that close, and probably couldn't do it on gravel, or mud, or on a wet day, or any condition where the surface changes significantly.

Survey Solutions, LLC wrote:

Survey Solutions, LLC wrote:

Definitely not overestimating when people on here can be within "two clicks" on a 5k.

Any thoughts on staking down a steel tape over undulating terrain and applying tension? Any thoughts on tensioning a steel tape in segments shorter than the tape length as you should do on twisting trails?

Still willing to listen to measuring techniques with a steel tape on a cross country course with undulating terrain and numerous turns. Keeping the tensioned tape firm to the ground seems "practically" impossible without stapling the tape to the ground in 6" or less increments on the ups and downs found on many cross county courses.

You seem to be operating under the assumption that a steel tape stretches by 3 meters when put under tension or something like that. Not so.

What method would you use to measure the error introduced by laying a steel tape over undulating ground that would be more accurate than laying another steel tape on the undulating ground right next to it to verify the first tape?

Go try it yourself and then come back here and tell us how your method is more accurate and more precise, as in repeatable and independent of ground conditions.