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Can weather effect elevation readings?
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I recently did two rides in Acadia Nat'l park that were virtually identical. The first was on a sunny morning, 52 miles long, and I got 4100 ft of elevation according to my 520. The second ride was 54 miles (including a short out and back to tack on a bit more time) and I got just over 1000 ft of elevation. The second ride was in mostly drizzle/fog the whole ride. Over the years, I've done lots of riding in Acadia, and know that the elevation gain for this ride is close to the first ride. Could the weather have played any sort of role in messing up the elevation data? I don't think that the 520 has a altimeter, but I'd also think that other data could be used to get elevation pretty close.

I did IM Norway earlier this year and the weather on race day was pretty miserable - constant rain, wind and pretty nasty. In mapping out the course ahead of time it had around 5500 ft of elevation, but I only got a bit over 2000 ft on race day. Anyone else have issues like this (not that it's really a huge issue, but just wondering what's going on)?

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Last edited by: natethomas: Aug 17, 19 17:22
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Re: Can weather effect elevation readings? [natethomas] [ In reply to ]
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According to garmin's website the 520 does have a barometric altimeter. So, it CAN be affected by weather...ie, changes is local barometric pressure typical of a front coming through.

https://buy.garmin.com/en-US/US/p/166370#specs
Last edited by: Tom_hampton: Aug 17, 19 22:07
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Re: Can weather effect elevation readings? [natethomas] [ In reply to ]
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My garmin elevation data is just random as soon as it rains.
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Re: Can weather effect elevation readings? [natethomas] [ In reply to ]
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Where's the little port (hole) for the barometer on the 520?
I'd guess it's somehow getting 'blocked' by some rain drops / water run off ?

The altitude reading defo can vary when there's a weather change (esp a weather front moving through, that causes a pressure change) but I'd be surprised that it would lose you 3000 ft unless its gone from nice and sunny to a bit of a storm.

I have an edge 800 and it's used in plenty of shiite weather (UK, and used off road through our winter ) And it doesnt see that massive variation).

The port on that is on the underside, just as the curved front end of the unit gets onto the flat of the back. It's a small (1.5mm ish) D shaped hole.
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Re: Can weather effect elevation readings? [natethomas] [ In reply to ]
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Yes very much so, I see it on Strava very often when a rider has had a coffee stop they will appear to have gained or lost several hundred feet in elevation due to a temperature change.
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Re: Can weather effect elevation readings? [natethomas] [ In reply to ]
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Short answer:
yes, absolutely.

Longer answer:
If the elevation data is based on GPS data, then weather should not affect the info (well, unless the weather is somehow so intense that it affects GPS transmissions, not something that I have ever had happen). But if the elevation data is generated from a barometric pressure sensor, then yes absolutely, changes in local air pressure can make quite a difference on the resultant altitude number. Even more so if the number comes from a cheapo barometric sensor embedded in a standard cycling consumer gps. Having had some experience in this dept.,this issue of weather affecting pressure is why pilots get the local barometric pressure at the intended destination airport just prior to landing, so their altimeters reflect the correct altitude at touchdown, which is kind of an important thing ...

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