Originally Posted by
svtmike
GPS is only accurate to about 10 feet (or more than the roll-out of a typical tire), and there's plenty of anecdotal evidence of the "auto-calibrate" function in the Garmins not being all that consistently accurate
Yes, but a Garmin can do a 'roll-out' 100s of times over hundreds of contiguous metres and get a statistical average, which would have a much lower margin of error.