I have been using a web site called runningmap.com to calculate my distances and my gps watch (stop watch portion) for the time. Maybe this site is not giving me accurate distances. I did check a straight 1 mile section of road with this web site once and it came out accurate. The trails I run on are not straight though but wind around with many curves. Wonder if its accuracy drops when calculating around these curves? Tried using a Garmin Nuvi that I use for traveling once to track my distance but found it to be very inaccurate. It consistantly could not track the first mile of my runs. Not even in pedestrian mode. Once past the 1st mile its seemed to track distance properly. Guess I'm gonna have too use something else. Time for a Forerunner apparently. I do have a measuring wheel which could be another option.