quote:But with a Jones counter and a 300m course I think your precision is only about 20% of the SCPF.
Neal,
I think you are spot on with this assessment of the Jones counter precision. I recently calculated virtually the same maximum error for a single ride, assuming the Jones read to the nearest half digit, and I also allowed 5 mm at each end for alignment error with the centre of the nail. I reckon I can get well with in the head of the nail which is 11 mm diameter.
I notice that two IAAF grade A measurers always clamp their wheel between each of the 4 rides, and that takes the overall precision down to well less than a tenth of the SCPF. However, I would not think their overall result is that good, because they visibly wobble slightly as they ride (not just during the pushoff). I am afraid these grade A measurers are never going to get representative results from pushing their bikes along a short cal course unless they can keep control of those wobbles and somehow allow for them.
Actually I think that the variation of wobble amount contributes to the scatter I have observed in a set of cal rides taken with a solid tyres under well controlled conditions on a 650.60 m cal course which I recorded in my article in MN no 78 July 1996. N.B. these data were taken reading the Jones to 0.1 of a digit - Some optimistic interpolation there perhaps - but it is a bit more accurate than those who read to nearest half of a digit.
