Originally Posted by mschwett

yep. different underlying terrain models, different degrees of precision in those models and the way they interpolate the "2D" points onto the underlying model... and then just the inherent problems of that methodology. it took RwGPS about 10 years to not register riding across the golden gate bridge as dropping 200' to sea level, and then abruptly climbing 200' back up. an extreme example, but 400 additional feet of climbing per round trip.