Originally Posted by
AdelaaR
Taking only one wheel revolution is dodgy since you are then extrapolating the slight error you made and multiplying it by thousands.
The best way is to take a measured course.
The second best option is to use google maps and find a straight road with cycle path next to it ... then ride from and to a specific point that is easily pinpointed on the map and take a long enough ride of 10 miles or something like that ... the margin of error will be very small then.
Again you have to make sure you're following the measured course exactly, which would mean drawing a line and then making sure you don't swerve from it for the whole course - much harder than rolling the bike down a straight line for one full wheel revolution a dozen times and rounding out the result
