Just to make things interesting, (at least to me :-) ), I am wondering
if the mountain bike distance was longer than the GPS distance beause as you
ride, the front wheel does not go perfectly straight, thereby
increasing the distance that it covers over the ground.
I am also curious if you have compared the bike, the GPS and the car over
a straight line from one know place to another.
All I am saying is that you are getting accuracies where a lot of these
"little things" that in the past could be neglected may be becoming the
major contributors to the little bit of error (or is disagreement between
each of the measurements a better way to phrase it) that still remains.
Restating that last thought, which of the three measurements that you have
is really the correct one? (As some people have been know to say, it is
sure nice to have a problem like that. :-) )
Joe jpu@kaiwan.com