FLAT CALIBRATION COURSES
The book’s requirement that a calibration course must be flat has been ignored for years. The question of “how flat is flat?” has never been addressed.
Over the same distance and the same riding posture, you will obtain fewer counts riding uphill than downhill, because your weight shifts to the rear, slightly unloading the front wheel. The reverse is true riding downhill.
The effect is the same when wind is present. A headwind produces fewer counts than does a tailwind.
The general sense is, I believe, is that if you do two rides in each direction the differences will even out. This remains unproven, but seems plausible. How steep a hill would be needed to make a difference is not known.
I believe we should eliminate or modify the “flat” requirement or reduce it to a “recommendation.” Most people will use a flat course anyway. I believe that this requirement, in practice, has not been enforced at any time.
One way to see how calibration courses vary is to download some cal course maps, and use Google Earth to check them for flatness.
It does my heart good to see Mark and Neville doing some actual experimentation. We spend a lot of time discussing rules rather than measurement science.