measuring xc courses?

David?

Maybe that is my name: a previous post makes a distinction you need to hone in on:"You know as well as I do that the ACCURACY of the wheel doesn't make any difference, only the CONSISTENCY."Does this change your question? You are confusing these two. You have to calibrate the measuring device you are using; a generally 'accurate' (e.g., one meter is very close to a meter) but uncalibrated device will not measure a course as precisely as a less 'accurate' (maybe 1 meter equals 1.2 meters, it does not matter, it comes out in the wash) device that is very precisely calibrated (because the 'meter' or whatever does not matter, it is the calibration, which will make the wheel go around more times if the nominal meter is short, but JR does not actually have 'meters' it just counts fractions of a revolution and the size of a revolution has been precisely measured you know the length you measured. Another point has been made a bit. It is commonly thought that a census, a complete count of the population, is more accurate than a sample. However, in a broad range of applications this is NOT the case, because a census cannot be carried out with complete fidelity (and sometimes over the necessarily short period of time). That is one of the problems with using a steel tape.

Please Reply wrote:

Measurer Wanna Be wrote:

I have read all posts in this thread and have found little support for why a surveyor's wheel is not accurate for mesuring cross country courses. I find it absolutely crazy that a steel tape would be even considered to try and measure a cross country course. Even on a road course, I question the process of measuring curves while maintaining proper tension on a steel tape. Is there anyone who has video of proper technique with a steel tape, especially what to do on corners and when one comes across depressions on the running surface of a cross country course.

David?

I love the calibrating before and after measuring mumbo jumbo. I have had the same wheel for ten years. Took it to the local track and was impressed that it hit 100m measuring a straight. Walked a lap - 400m, jogged a lap - 400m. Marked off several workout courses every 400m up to 5k in distance and probably twice a year I need to redo my painted marks so I take the wheel WITHOUT calibrating and amazingly I find my marks always within the meter. I bet the reason they aren't pefect is because I'm human and can't replicate each tangent precisely. I doubt I could with the Bike Counter either and I don't have to get on and off every 400 or calculate clicks.

I have read all posts in this thread and have found little support for why a surveyor's wheel is not accurate for mesuring cross country courses. I find it absolutely crazy that a steel tape would be even considered to try and measure a cross country course. Even on a road course, I question the process of measuring curves while maintaining proper tension on a steel tape. Is there anyone who has video of proper technique with a steel tape, especially what to do on corners and when one comes across depressions on the running surface of a cross country course?

I was hoping DAVID KATZ would repond to these questions and those posed by the other posters.

Sounds like there should be a measuring contest between dukerdog, David Katz, Mike Rohl, Surveyor Stevo, J.R. and any other poster that feels they have the best devise and expertise.

Maybe Lets Run or FloTrack can sponsor the event and bring all the contestants to Terre Haute to certify the NCAA course, or sounds like the Wisconsin course could use some tweaking.

Does anyone want to place bets on who will win this event?

Dear Posters,

Sorry I havent' replied. I am tied up with several events this week including one small one - the ING New York City Marathon!

The process of measuring a cross country course is difficult and very time consuming but I believe it is the only way of finding the true accuarcy of a non paved surface.

I don't think that most of you would do it this way, but I would.

What you need:

1.100 meter steel tape. I prefer one that the end is not the zero mark. They are not easy to find. I got mine in Europe.

2. A 100 + metal spikes at least 12 inches long.

3. A few hammerss

4. A few people as crazy as I am.

5. Double set of notes!!!

6. A few surveyors flags. The ones made of a wire & small flag.

7. Spring scale

8. Tape measure thermometer (if you really want to be accurate).

9. Calculator

The method

1. Use the wire surveyors flag to mark the "zero" mark of the tape & the 100 meter marks of all segments.

2. You should use the spring scale on all measured segments to ensure you have the correct tension.

3. For segments on turns and curves. This is the hard part for several reasons:

- identifying the parameters of the course (which would be a problem with any measuring device).

- where to measure? The shortest path? down the center? Different Federations, different standards.

So let's say you are measuring the shortest path and you have a pretty good idea of the left and right sides of the course. I would measure 30 cm from the outside edges of the course to be consistent with road course measuring.

I would hammer metal stakes every foot (or as needed)to create the curves/turns to pull the steel tape against.

Repeat the process until you get to the finish.

AND if you really want to be accurate, record the temperature of each segment and make your corrections at the end of each segment!.

I called one of my friends on the other side of the Pond who is one of the best course measurers in the world and he agreed with me that this is truly the best way to find the accuracy of a XC course.

So who wants to help me measure VC?

??????????????????????????????????

How would you know who is right if you think that all methods are accurate???????????

David Katz wrote:

I would hammer metal stakes every foot (or as needed)to create the curves/turns to pull the steel tape against.

and here is where I feel your method will yield a very inaccurate result. This method will really only work reliably on flat surfaces or concave portions of a slope. Measuring a dip will require significant downward pressure on the tape which is going to interfere with the tension. The same situation is going to occur during tight turns. The alternative is taking a lot of short intermediate measurements which while technically possible isn't going to yield a significantly more accurate measurement than a weighted wheel.

This gets back to my original point. If you have a surface that's not severely undulating without sharp turns I doubt steel tape is going to yield a level of accuracy any better than a calibrated weighted wheel (whether it's attached to a bike or not). I would bet the hours of extra effort wouldn't mean a difference of more than a few feet if experienced measurers were doing both.

If the course had many turns or undulations, I venture a bet a weighted wheel would come out more accurate with an order of magnitude time savings. Sharp turns on an uneven surface are difficult on a bicycle but not with a weighted wheel.

Now the reason I keep saying "weighted" wheel is most push wheels are relatively light and do an incredibly poor job on non-paved surfaces. Most, even the Gandy's I've seen, require some consistent downward pressure to maintain reliable contact. I have not felt the larger metal Gandy's I saw on their site.

What I have seen and felt that worked well was essentially a front fork with a 20" mountain bike type tire, a handle and cross-bar kickstand with a Jones-type counter on it. The stand when not pushed down gave a nice stabilizing action and the entire unit weighted enough to maintain good ground contact. I'd love to buy one if I could figure out who makes them.

David Katz wrote:

??????????????????????????????????

How would you know who is right if you think that all methods are accurate???????????

Why do you think I feel all methods are accurate?

I just think it would be fun to see how much time each of you spent, and the distance differences each would come up with.

Lastly, you need to freshen up on your measuring methodolgy if you plan on measuring a college course. 30cm is not part of the protocol in the NCAA Manual.

Keith

Good points. But here's the basic problem measuring a xc course - do you measure up and over roots and rocks on the course or take a straight path?

Maybe surveyors should measure to the deepest part of a water jump in the steeple or the arc over the hurdles I'm being silly, but we have no standards for this. And when I say "we", I mean us - as amateur surveyors.

I believe surveyors employ a method called "breaking tape" to measure a slope that is so great that the entire tape cannot be used. It's basically what you described as measuring shorter segments but this time with a longer tape.

Obviously there are standards that a surveyor would use that most of us don't.

For example: When you use a steel tape it must be corrected for temperature and slope correction and tension correction. the formulas for these are available in any basic survyor's book.

We are all playing around with this looking for a convienent, quick way to get a relative accurate course. But we are just talking about the tip of the iceberg when it comes to being truly accurate.

Dear Gentlemen & any ladies out there,

This has been a fun discussion.

Thank you to all of the very informative posters. Maybe someday I will have the oppertunity to work with some of you. I'm sure I would learn some new tricks of the trade (this old dog can learn new tricks!). But it's time to move on and I need to focus on some other real time issues. Good luck to all of you - especially those running the ING NYCM this weekend.

For anyone needing my assistance for any technical issues, I can be reached at

katz@flrrt.com

. but please wait until after the marathon.

See you at the finish line.

Regards,

David

Well Said!

Measure Off! wrote:

Sounds like there should be a measuring contest between dukerdog, David Katz, Mike Rohl, Surveyor Stevo, J.R. and any other poster that feels they have the best devise and expertise.

Maybe Lets Run or FloTrack can sponsor the event and bring all the contestants to Terre Haute to certify the NCAA course, or sounds like the Wisconsin course could use some tweaking.

Does anyone want to place bets on who will win this event?

Cross country courses are not eligible for certification - for all the reasons that've been discussed repeatedly on this thread. How would we pick a winner? How would we know who had the most accurate measurement of the cross country course? Me, I'd use the method I proposed at the outset: take a reliable measuring wheel, calibrate it on a representative stretch of the course to be measured, the follow the path as outlined in the NCAA manual - whatever it is. DKatz would use his steel tape method.

Again - I think it would just be interesting to see the different methods used, the amount of time each put into it, and in the end the different measurements. If I lived on the East Coast I would pay to help DKatz tape out VC - just because I think it would be interesting and enlightening.