I have just shown that the calibration factor determined with the new 25-m course method differs from that on a home 400-m course with later temperature correction by pressure monitoring by only negative 0.008%. Since it only took a total of 5-10 min to do the calibration on the temporary 25-m course, this means that the new method is quite competitive.
At the start of a certification, I calibrated on my home 400-m course:
Temp: 70 deg
Tire press: 600 kPa
Whole rev: 191
Spoke intervals out of 32: 15.3, 15.7,15.1, and 15.4 (ave, 15.375)
Calibration factor: 1.001(191+15.375/32) /0.4 = 479.18 rev/km
After bicycling 20 miles over 75 min to the race course, temperature had risen to 80 deg and tire pressure to 612 kPa. Based on a pressure coefficient of negative 0.1333 rev/km/10 kPa, the new calibration factor was 479.18 - 0.16 = 479.02 rev/km. The uncorrected factor differed by plus 0.033%.
I decided to compare the factor obtained from the new 25-m method. There was no painted line at the side of the road, so I used the distinct line of a concrete gutter. (Mark Neal seems to have tested the method on something similar.) I did all measurements in the same direction, since the gutter sloped towards the curb and I felt most comfortable guiding the bicycle with my left foot on the upside of the slope.
Whole rev: 11
Spoke intervals: 30.8, 30.8, 30.9, and 30.7 (ave, 30.8)
Calibration factor: 1.001(11+30.8/32)/0.025 = 478.98 rev/km (negative 0.008% from pressure monitoring)
Thus the new method compares very well with pressure monitoring on a home 400-m course and much better than the conventional use of a home course.
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