Using a pre-programmed route is going to introduce as large a margin of error as an improperly set wheel circumference, if not more. After all, if you rode your bike on Lane 1 of a track four times, you'd cover 1,600 meters. If you did 4 laps in lane 8, you'd cover 1,815 meters. Every time you go around a corner, narrower or wider, you'd be changing the distance. Traveling a mile in as straight a line as possible (like on a river trail) should be plenty.