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1040 total ascent data inaccurate - 50% too low

shiltian

I have a course on Garmin Connect that shows 2,539 ft total ascent. When I rode it, my Garmin 1040 only recorded 1,414 ft, which is way too low. My friend rode the same course with a 1050, and his recorded 2,800 ft. That seems too high, but that's outside the scope of this post. I did have auto altimeter calibration turned on. I can share the activity file and the course file if needed.

  • 0

    from where you know that is the 2539ft GC data correct? if it is a public link, can you share it? or do you upload your rides on Strava? what does Strava give you for the course after Strava Elevation Correction (the GC elevation correction "change elevation source" is useless, dont use or count on that)

  • 0 in reply to Luko79

    The course link is: https://ridewithgps.com/routes/51278494. After correction, Strava gives me 2,710 ft. I'm not saying 2,539 ft is 100% accurate but at least it should not be 1,400 ft.

  • 0 in reply to shiltian

    was it raining (on this ride or prior) or isnt the barometer's hole dirty?? is the elevation chart same as your friend's one? or is that already a mess?

  • 0 in reply to Luko79

    The elevation chart is same as my friend's. Hmm, it was indeed a fairly heavy rainy day. I was not aware of the hole actually.

  • 0 in reply to shiltian

    but you meant the original elevation chart is the same, not after the elevation correction on Strava , right? (because after correction the Strava redraw the chart by its own altitude datas, so the raw profiles on GC for both, i suppose your friend was not selecting the correction on GC)

  • 0 in reply to Luko79

    That's a good point. Yeah, after I reverted the elevation correction, the chart looks completely messed up.

    Bad:

    bad

    Good:

    good

  • 0 in reply to shiltian

    yeah, now we found your problem, the hole got dirty/moisured during the ride and it messed up the altitude data which messed up the total ascent also. blow it out and it will be fine during the next ride. 

  • 0 in reply to Luko79

    Thanks! What can we do to improve things when riding on a rainy day?

  • 0 in reply to shiltian

    probably checking those 4 tiny holes midride and blow out a few times. the reason why the 1050 could measure it better (without issue) that the holes are at different place in the back if i remember good but i think there is no 100% waterproof design. and probably the placement is also a key, if it is on a front mount, that a bit worse than if it is on the stem. but i am just guessing, i am not riding in rain , just in dry sunny weather if possible, i hate cleaning the bike :) 

  • 0 in reply to Luko79

    The 4 small holes on the backside of the device is NOT the Barometer. Thata the beeper.

    The Barometer is the small slotted hole on the right side behind the battery door.

    support.garmin.com/.../

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