Originally Posted by
njkayaker
All that doesn't make what Garmin said incorrect.
It's a short, simplified answer in an FAQ. It doesn't get into the details of how these devices work.
You don't know whether there's really any difference between using that and other methods.
It is the most accurate way to calibrate tire circumference.
Again, this is wrong. The GPS can have drop outs and doesn't account for elevation. And it might cut corners too. And Garmin says otherwise.
Elevation error is already very small AND it can be corrected using readings from a barometric altimeter. Errors from cutting corners can be an issue mountain biking, but they're pretty insignificant when road cycling.
This subject has been discussed at length in several other threads. Anyone interested should just search for those threads.