Just been for a ride with a mate and we both have Garmin 800s and we both rode the same route but one of our units said we’d climbed about 100m more than the other.

[irony]Now, you have to believe me when I say I really don’t mind looking like the bigger and better rider[/irony], but I was just wondering if anyone had any idea why two supposedly identical devices would record differently to such an extent (over a 40 mile route)?

Is there some sort of calibration that one of us should have done or something?

This crops up a lot – search the forums and you’ll find lots of info.

I assume you were doing this all the way round

It’s just poor signals from the satellites that usually do it.

I assume you were doing this all the way round

🙂

Does the 800s ahave an altimeter built in?

If not, it is picking up altiitude information from satellites, which is notoriusly inaccurate…

Does the 800 have an altimeter built in?

Yes.

Small variations in air pressure can add up to a fair amount over the length of a ride, I suspect even how the device is mounted (bar/stem etc)can affect the air pressure it see’s. I use the silicone case on mine which seems to go some way smoothing out fluctuations.