elevation during activity

Been covered a fair bit in the past, I know, but just went out for a 4 mile run and during this time, GPS started off and ended up wrong. Altitude was 53ft but my workout has been starting at -17ft and finishing -99ft.

30 mins before I ran, I also calibrated the altimeter using dem. First time I have done in a while as usually train enough with GPS through the week to keep it within reason but this week I haven't and it's drifted off a bit.

I also calibrated straight after the run, again using dem and it went back to the correct 53ft altitude.

GPS went green and I always leave for at least 30 seconds before starting. I have auto cal set to continuous during an activity (not start), so would expect it to have tracked better than this. Wondering if the stormy weather might have an impact as Ive not noticed this behaviour before.

Thanks

0 Former Member over 6 years ago

I ended up disabling auto calibration during activity because it would drift to values that would have nothing to do with reality.

I usually calibrate altitude before the activity (manual value entry, gps or dem) and then it tracks quite well the changes.

0 jaco.8 over 6 years ago

therefore during the activity it is better to deactivate the automatic calibration. if I leave it "continue" what happens because this function I never understand. even for the battery is better?

0 Former Member over 6 years ago

I posted a similar question last night. I turned auto calibration from continuous to ‘at start’ and seems to be an improvement this morning. Still not perfect though.

0 Former Member over 6 years ago

As far as I understood, and please someone correct me if I’m wrong, continuous auto calibration uses the GPS data to get the elevation from the map data (DEM).

This should work fine in theory but if the terrain is very abrupt it leads to very inaccurate calibration in my experience. That’s why I ended up disabling it.

I assume the advantage of auto calibration would be that it compensates for changes in weather, that is, the watch could tell if an increase / decrease in pressure has to do with weather or with a change of altitude.