Have used GMaps pedometer for some time now to measure running distances. Always thought this was accurate, as I checked some routes with the car mileometer. Now got a garmin, and finding that the garmin distances are often greater, by anything up to 0.2 miles. this is, say 200 yards, which is quite significant if trying to accurately measure run pace etc. I am now tempted to go back to using the car speedo again! I recently ran an offically measured race, and the garmin distance was way out, or was it the method that the race organiser used to measure the distance? who knows! Anyone with any experience of what is most accurate.