Surveyor Steve wrote:
There are click wheels, electro magnetic wheels, gear driven wheels, and belt driven wheels. They all perform the same function but accuracy varies dramatically. The Jones-Reigel unit is just a typical gear driven devise from what I have seen. The tolerances and gear mechanisms may be the best in the world but I have seen no date to prove such a statement or no data to prove it as superior to any other gear driven push wheel.
You know as well as I do that the accuracy of the wheel doesn't make any difference, only the consistency. If I calibrate my wheel on a surface and then measure a course on that same surface, and the wheel is consistent, I will be just as accurate as someone using a wheel that is giving precisely one linear meter per revolution on the surface. But you can never be sure your wheel is doing that, so you have to calibrate it. Your surveyor measurements are no different. Even though you claim you always get 1 linear meter per revolution, you are still required to calibrate before and after every measurement.
You are correct. The JR counter is no different from any other gear-driven device that counts wheel revolutions. Just like a measuring wheel, when you calibrate you aren't calibrating the counter, you are calibrating to find out how much linear distance is covered in 1 wheel revolution. When people say a JR counter measurement is more accurate, they are really saying that riding a road course on a bicycle with a calibrated front wheel is more accurate than trying to push a calibrated measuring wheel, mostly for practical reasons. It is easier (and thus more likely that it will actually be done) to ride in a straight line over long distances than push a wheel. It is easier to contend with traffic. Small rocks in the road don't affect a bicycle tire nearly as much as an, essentially, rigid measuring wheel.
The American Congress on Surveying and Mapping (ACSM) does not recognize the Jones-Reigel counter as an acceptable devise for any measuremnt purposes.
What device do they approve for measuring 10km road race courses?
Didn't David Katz also say the JR Counter is not an accurate measuring tool?
He said it's not accurate for measuring CROSS COUNTRY courses. He also said a measuring wheel is not accurate for that purpose. I think he would agree that an uncalibrated measuring wheel is just about the worst thing you could use.
How do you know he didn't calibrate his Gandy Wheel?
I don't know for sure, but I'd be willing to bet a lot of money that he doesn't calibrate his Gandy wheel before and after every measurement. I'd be willing to bet almost as much that he has never calibrated it. You want to take that bet?
Actually, if he did calibrate his wheel I think his course measurement is pretty accurate since he has taken multiple measurements with a couple different devices.
Do you own a JR Counter?
Of course I do.