I just purchased a Gamin Edge 510 and took my first real ride this morning. It was one of my normal weekday morning rides along the coast that starts and ends at my house. My question is how is that the elevation chart is different at the end of the ride? I would think that if you could take the chart and fold in over itself at the midway point that the elevation would match since I rode out and back along the exact same course. I started at 31 feet (which seems off as well) and ended up at 2-3 feet or so. There are some parts of the course that shows below sea level.