Originally Posted by
DiabloScott
One fellow I follow recently rode 14 laps around his neighborhood in the late afternoon. His elevation chart looked like he was going downhill the entire time - he posts here and is public so check this out:
http://www.strava.com/activities/93277888
He uses a Garmin Edge 500 that has the altimeter function. The GPS elevation data will more likely be consistent from ride to ride even if it does sometimes give funny results when riding over a bridge.
Originally Posted by
rdtompki
Looks like the GPS altitude at the start was in error at the start and was gradually settling down to the correct value.
Actually what is happening is the barometric pressure was rising. If you look at the elevation track it looks like an angled saw blade. The low point is right after he turns onto Lincoln from Jefferson. If you look to the north of that you will see a creek/drainage channel that confirms that the terrain is sloping down in that direction. The difference between there and the opposite corner, Polk and Adams, appears to be about 15-20 ft. If you look at the graph of speed against elevation, the general shape of the elevation profile is confirmed.