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  1. #1
    trail rat
    Reputation: slocaus's Avatar
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    Edge 305 Submarine?

    My Garmin Edge 305 was a little confused on an early morning ride. It seems to think my elevation is a little below sea level, but I swear, I was not all wet like it was.

    I usually let it set and calibrate altitude for about 15 minutes before I start to ride, but that morning, I turned it on, hopped on and rode. This ride goes from 213 feet to sea level, obviously. I just got a chuckle out of it when I saw the elevation reading while drinking my coffee.
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  2. #2
    Double-metric mtb man
    Reputation: Psycho Mike's Avatar
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    hehehe. That's the reason why pilots need to set their altimeters as part of their pre-flight. Pressure changes and when you're already that close to sea level, it can make the barometeric altimeter think you are below mean sea level.
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  3. #3
    mtbr member
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    I'm guessing that the pressure changed during your ride. Barometric altimeters are nice, but if there's a decent atmospheric pressure swing, they can be thrown off. So 30ft is not really that big of an issue.

  4. #4
    trail rat
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    Quote Originally Posted by dnlwthrn
    I'm guessing that the pressure changed during your ride. Barometric altimeters are nice, but if there's a decent atmospheric pressure swing, they can be thrown off. So 30ft is not really that big of an issue.
    I do not think the pressure changed much on this foggy morning (we call it marine layer in CA). It changes as the marine layer burns off. This was just a tongue in cheek post for grins, I understand the way altitude works in a GPS, so it is not an issue looking for a solution.

    I have a 60CSx that I calibrate before each ride, and it gives much more accurate readings, of course. If I let the Edge sit and calibrate for 15 minutes, it comes quite close to being correct.

    As Psycho Mike pointed out, anyone needing real accuracy has to calibrate an altimeter for each use.
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