Does anyone else have issues with Garmin elevation in the rain?

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  • Mikey23
    Mikey23 Posts: 5,306
    I think all the newer ones do. If i remember correctly the 500 had the hole right underneath so never seemed to get clogged
  • cycleclinic
    cycleclinic Posts: 6,865
    My 500 has elevation trouble in windy conditions (more elevation that i have climbed) and in fog or rain i get alot less elevation.

    Anything but calm conditions mean my elevation numbers are simply wrong.
    http://www.thecycleclinic.co.uk -wheel building and other stuff.
  • Dorset_Boy
    Dorset_Boy Posts: 7,579
    Strava elevation correction is wildly inaccurate in hilly and mountainous areas, often overstating actual climbing by in excess of 50%. The Strava phone app is just as inaccuarate.

    Garmins do need to re-position the barometric alimeter holes for sure.
    Also 810s tend to under read, 510s over read and 800s are pretty accurate........
  • ElectronShepherd
    ElectronShepherd Posts: 227
    I really wouldn't trust it at all. As has been said, it's based on air pressure, so if the air pressure changes, it will count as an elevation change, regardless of if that's due to you slogging up the side of a mountain, or simply the weather improving.

    I've been on loops from home, (i.e. starting and finishing on my drive), and I've seen my Garmin report a total ascent of 2,200 feet and a total descent of 2,450 feet. I think I would have noticed if my house had slid 250 feet down the side of the hill while I was out riding!
  • chris_bass
    chris_bass Posts: 4,913
    I climbed 12 meters on my turbo this morning apparently!
    www.conjunctivitis.com - a site for sore eyes
  • Lookyhere
    Lookyhere Posts: 987
    i ve a case open with Garmin atm, they offered me a new device for a grade display issue ie under any trees or cloud cover the grade drops to 0.0%, even if the hill doesnt!!! i never lose the GPS signal.
    i said (to Garmin) why dont you try and fix it, as its most likely a s/w thing, they ve copied everything off my 520 and opened a case with Garmin US.

    the more the display drops to 0.0% or another random figure (on hills) the more the elevation data is different for a given route, following a course and it is always accurate, so uses course data in this case.

    Is it a given its the barometric sensor that only calculates the elevation and not a combo of this and/or GPS data?
  • ElectronShepherd
    ElectronShepherd Posts: 227
    Elevation data from GPS is much worse than position data, for a variety of technical reasons. See http://gpsinformation.net/main/altitude.htm for some more information.

    I would imagine that the Garmin is using barometric data only to get a gradient, since altitude information from GPS will have far too high an error associated with it.

    The barometric sensor is sensitive and precise, but not accurate. That means you can use it to determine a gradient, since it can detect changes in altitude with reasonable precision over a short period, since atmospheric conditions don't change that quickly.
  • Lookyhere
    Lookyhere Posts: 987
    Well, yes but that doesnt explain why, on a hill the grade display drops to zero when under trees, this would suggest that the gps data is somehow involved too, as tree cover isnt going to effect any barometric pressure.
  • rolf_f
    rolf_f Posts: 16,015
    You can't get a gradient from barometric data alone - you still need the spatial data to know over what distance the elevation change has occurred. If you climb 1ft in 10ft the gradient will be obviously be different than if you climbed that 1ft in 20ft. So if the gps has lost reception it will likely momentarily assume it is stationary and therefore the gradient will be infinite which the gps is probably programmed not to display.

    You should be able to check this by displaying elevation alone as that would be unaffected by the trees.
    Faster than a tent.......

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