Don Garrett and I plan to measure a couple of permanent calibration courses this week.
The one nearest my house can be as long as 450+ meters long and I believe the other course is about the same length.
Should we measure the full length available of approximately 450 meters ?
Any reason we should create a calibration course shorter that what is available ?
Any more than 300 meters adds no significant accuracy, but does add riding during calibration. I don't see a great benefit in longer calibration courses.
I think 300 m is just the minimum acceptable, not the ideal length. Although the extra accuracy with 450 m added is small, I would nevertheless layout the longer cal course if it was going to be used many times. To me, an extra 5 minutes spent on 8 calibration rides (if at 10 m.p.h.) is no big deal when I may spend at total of 6 to 10 hours in all on measuring a 5k to 10k course. Perhaps more significant is the time spent laying out and checking the calibration course if it is just a calibration course for a one-time use. In that case I would usually go with 300 m rather than 450 m
I am sufficiently concerned about maximising calibration accuracy that on the few occasions I have had to lay down a cal course less than 300 m eg 200 m and once 150 m that I will ride these short courses 6 to 8 times both before and after to get the best possible calibrations.
There was a recent thread about calibrating over 20 m or some such ridiculous distance. I would strongly advise novice measurers against that. You need to calibrate with the same riding style and approximate speed as you use during the measurement, in order to be sure that your wobbles and weight on the front wheel are the same when measuring and when calibrating.
My regular calibration course is just under 700 m which would doubtless seem overkill to many, and I have to admit that when rushing to do the 4 ride calibration at the end of a long day that extra five minutes sometimes seems to gain greater significance. However, it has never caused me a real problem. Greater time wasters by far are the problems generated by race directors when you have to measure lots of bits and pieces while they make up their minds, or as a certifier when you get a measurement report with which you are not happy.
An example of the latter is the measurer who tries to convince me that a single post calibration ride is sufficient. Although it could possibly be accepted in some exceptional circumstances, I really worry about a measurer whose time is in such short supply that he cant do 4 rides or understand their value. What other short cuts might he be taking with his measurement? (Or even worse long cuts!)
Mike Sandford -
Measurement Secretary South of England
UK Asssociation of Course Measurers
email contact m.sandford at lineone dot net
It would be a waste of effort to use a calibration course with a length greater than 300 m. The overall accuracy of a procedure is governed by that of the least accurate measurements. In the case of certification this is the actual measurement of the race course, because of such errors as that in following the shortest possible path through comparative complex layouts, and lack of correction for temperature, hills and road surface variation. Calibration over a 300-m course is the most accurate measurement, and will therefore not influence the overall accuracy. Improving it by going to a longer course would be wasted effort.
In fact, I have found recently as described on this bulletin board that I get the same calibration factor from a 25-m using a new method as that from a 300-m calibration course using standard riding technique. This may seem ridiculous to those measurers who are used to using a 700-m one, but in recent weeks I have observed this ten times. Maximum deviation has been less than 0.06 % and spread of readings in any set of four usually only 0.1 of a spoke interval. The new method works because I accurately follow the white line at the side of the road by coasting with the occasionally push from one foot on the ground. Also rotation measurement is 25 times more accurate than that from the Jones.
It would be interesting if while laying out your new course you would permanently mark one of your tape lengths and see if you can duplicate my results.
The argument against shorter calibration courses, say 100m, of normal riding is that the initial wobble affects the overall calibration constant too much, i.e., you aren't riding straight enough.
If it does indeed turn out to be true that with Neville's method the calibration constant is always smaller than found with 300m of normal riding, and with less variation, the argument against it would be that you are riding too straight!
I find it hard to believe that a 25 meter Cal Course is ever going to be acceptable. Wobble is very common for most riders when starting a cal ride. Yes, I'm sure you could get good results if you were very very careful.
As the electronic unit being 25 times more accurate than a Jones counter, how did this come about(don't answer please)? Why not 30 times or 10 times! Yes, the electronic counter is good and I don't feel we need to be negative toward the Jones Counter.
Going negative is bad and it's time for all of to stop.
Thanks to each of you for responding. I appreciate everyone's feedback.
I decided to make use of the distance that was available. Don Garrett came over yesterday afternoon and assisted with the measurement.
The calibration course measured to be 447.7 meters. This course is just 20-30 meters from my house so it will be really nice be able to do my calibration before loading up my bike. Also, will be nice to able to print-out target counts for the first ride before leaving my house.
Once again, thanks for taking time to respond to my question.
I was not aware I had said anything negative about the Jones. I do not like to see negative remarks such as those containing inflamatory or derogatory words,but I hope that no topic is too sacred for discussion on this BB.
I should point out that rim reading is not necessarily peculiar to the electronic counter and that Jones users can utilize it with their counter to get precisely the same accuracy as can be obtained as when it is used with an electronic counter.
You missed my point about starting wobble. The new method works because this is elimninated in the new method. It is performed a little differently than the traditional method but requires no more care.
We will not know as to whether it is acceptable until other measurers have tried it. It may give better results on a race course site as compared with those from a tradtional calibration course several hours away.
One of the greatest advantages I've found in the Protegé vs. J/O is that you can calculate and print out target split readings ahead of time, and not worry about what your counter will read at the start.
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