Originally Posted by
Snuffleupagus
FYI - One of my frequent riding partners is an artillery officer, and he states that GPS data is unreliable for altitude. You'd be better off using a benchmark calibrated altimeter.
This is true, however it was with my edge 305 which also has a built in pressure based altimeter, and uses that in combination with the GPS signals. The accuracy is questionable, but it does give a rough estimate. The same 30 mile loop normally comes in + or - 50 feet of variance from rides in the past.