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Garmin Edge / Strava elevation correction


jatho

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I went on a ride a few months back and a lot of it was under trees so my Garmin (Edge 520) would pause randomly as it lost GPS connectivity and could no longer determine if I was moving, no problem I thought I'll just use that handy Elevation correction option on Strava, boom sorted.

 

I started randomly correcting the elevation after rides and noticed that the differences were sometimes quite significant at up to 20% even on rides where I didn't lose GPS connectivity, now I know that the GPS data is not synced continuously on a ride but rather periodically to save battery life but surely it should be quite accurate?

 

My question.... Is the corrected elevation data from Strava accurate / more accurate than the Garmin and why is there sometimes such a big difference between the Garmin data and strava data?

 

My Edge is using GPS+Glonass

 

BTW, my Garmin does seem to under read, was on a ride with a mate who has a Wahoo and his total ascent for the ride was a fair bit more than mine.

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AFAIK the 520 has a barometric altimeter, so in theory it should be more accurate than Strava.

to test find out where the trig beacons are in your area, go there and check elevation on your edge compared to the info as per the beacon

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I have a garmin edge and a garmin fenix and they are always 10% different to each other. If you read the garmin disclaimer on altitude you will see that they acknowledge their units are not accurate. Strava help section says the same but what strava does it collects data on segments from hundreds of users and calculates an average. I think strava also tracks contours and tries to estimate from that but read their site and see.

 

Sent from my SM-G925F using Tapatalk

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Take readings with a slight pinch of salt in my opinion...

 

When last did you calibrate your barometric altimeter? My guess is never...

 

Strava has a global DEM which they are now updtating with Barometer readings from people which in my opinion is not ideal seeing as no one ever calibrates them.

I know Garmin had an auto calibration function but can't find the poi dataset it uses for that so can't comment if that works.

 

So really having an accurate and precise altitude is not as common as you would like.

 

In my opinion the DEM from strava is not as accurate as a calibrated altimeter, but it is more precise and thus more reliable especially as you are more interested in difference in altitude not exact elevation.

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I have a 520 too, and it has a barometric altimeter - GPS elevation data is notoriously inaccurate. By that I am not saying the Garmin is always right, mine malfunctioned on a ride in the rain once.

 

I have also found some large discrepancies in some instances on Strava.

 

Not really sure what dataset Strava uses.

 

You can also plot your route on https://www.doogal.co.uk/RouteElevation.php, which uses Google data, and get yet another answer.

Edited by Halfdoesyn
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I have a 520 too, and it has a barometric altimeter - GPS elevation data is notoriously inaccurate. By that I am not saying the Garmin is always right, mine malfunctioned on a ride in the rain once.

 

I have also found some large discrepancies in some instances on Strava.

 

Not really sure what dataset Strava uses.

 

You can also plot your route on https://www.doogal.co.uk/RouteElevation.php, which uses Google data, and get yet another answer.

 

Barometer measures pressure, water stuffs atmoshpheric pressure around. 

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Take readings with a slight pinch of salt in my opinion...

 

When last did you calibrate your barometric altimeter? My guess is never...

 

Strava has a global DEM which they are now updtating with Barometer readings from people which in my opinion is not ideal seeing as no one ever calibrates them.

I know Garmin had an auto calibration function but can't find the poi dataset it uses for that so can't comment if that works.

 

So really having an accurate and precise altitude is not as common as you would like.

 

In my opinion the DEM from strava is not as accurate as a calibrated altimeter, but it is more precise and thus more reliable especially as you are more interested in difference in altitude not exact elevation.

 

Yup, never calibrated it, need a reference point to do that with accurate altitude which I need to find.

 

My issue is not so much that the altitude may be incorrect its more that its not logging the correct ascent for a ride, by calibrating the unit its not necessarily going ensure the logging is corrected.

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Are you eventually back from your Cape Town epic training camp? You two put in serious miles down there.

Edited by Long Wheel Base
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Are you eventually back from your Cape Town epic training camp? You two put in serious miles down there.

Well I've moved to the Cape so still here but Wally is back :D

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This has been discussed a view times.

I've looked at some strava points vs geo maps, and strava is also out a bit.

 

I would rather trust the unit (if calibrated), and event then, its probably at best within 10-15%

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Strava Always over estimates the elevation and more important it is device dependent with apple devices being the worst.

 

Certain Garmin devices are more accurate than others and the ones with barometric elevation are closer the the correct values. 

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I recorded my flight back from CPT to JNB on Tuesday, just to see what data it spits out afterwards. Didn’t get any KOM’s so I deleted it from Strava... [emoji12]

 

The elevation gain was 12683m (Strava) and 12607m (Garmin Connect) with the elevation correction disabled. With elevation correction on it shows a 20144m gain on GC.

 

The graph for the elevation correction shows the profile as if I were driving over the mountains on the flight path, versus driving around the mountain on the road.

 

Elevation correction disabled:

7be194a9413a6a2e15492905eaf26330.jpg

 

Elevation correction enabled:

4f3d7ad6729d98c11be2601a323ff877.jpg

 

 

Sent from my iPhone using Tapatalk

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