Effect of rain on altimeter

dirkmjk
dirkmjk Posts: 4
edited September 2013 in Road general
I’ve analysed a number of rides. Some preliminary conclusions: If you want to boost your ego, let Garmin recalculate your ascent. I’m not sure weather changes have a big effect on the altimeter, but heavy rain does seem to mess with it. Details here:
http://www.dirkmjk.nl/2013/09/cycling-garmin-altimeter-compared-elevation-databases
If anyone has done similar analyses, I’d love to hear about them.

Comments

  • Dorset_Boy
    Dorset_Boy Posts: 6,922
    The altimeter uses barometric pressure - if the pressure changes during your ride, as it often will, the reading will alter.
    Move from sunshine to rain and the barometric pressure will probably have dropped.
  • dirkmjk
    dirkmjk Posts: 4
    I looked into that possibility. The effect of pressure changes appears to be limited.
  • sungod
    sungod Posts: 16,545
    my 705 used to get altitude wrong in heavy rain, i think after a while the ports on the underside clog with water

    thinking about it, putting scotchgard on the underside of the body might prevent this
    my bike - faster than god's and twice as shiny
  • jezzpalmer
    jezzpalmer Posts: 389
    sungod wrote:
    my 705 used to get altitude wrong in heavy rain, i think after a while the ports on the underside clog with water

    thinking about it, putting scotchgard on the underside of the body might prevent this

    I've had this on the 800, did an out and back tt course along the same road in rain/spray, the gradient out recorded correctly, but went way out on the way back.
  • overlord2
    overlord2 Posts: 339
    There is a hole at the front underneath the Garmin that gets blocked with water. It also renders the %grade function useless.
  • mrfpb
    mrfpb Posts: 4,569
    My Garmin 800 and Cat Eye Adventure both drop about 100 metres at sunset. Haven't noticed any weather related inaccuracies.
  • dirkmjk
    dirkmjk Posts: 4
    Thanks for the feedback

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