Measuring a road race course with a car's odometer or even using a hand held GPS unit is just not accurate enough to allow meaningful comparisons of runners' times on different courses. We need to be able measure with an error of less than 0.1%.

Race Length
Maximum allowable error
10 km
10 m
10 mile
16 m
42.2 m

The only practical method, recommended by the IAAF and the UKA and used throughout the world, is the CALIBRATED BICYCLE METHOD:

  1. Calibrate the circumference of the front wheel of your bike, by counting the number of wheel revolutions over an accurately known distance. In this and the next two pages I call these "rev.counts"
  2. Calibration constant = rev. counts (ie complete revolutions and fraction) divided by distance
  3. Ride bike over the race course, counting the revolutions,
  4. Recalibrate front wheel to check for changes in calibration constant (due to temperature changes or air leaks)
  5. Calculate course length = Course counts divided by calibration constant (n.b. Use the largest calibration constant to make sure that the course will not be short)

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