Strava elevation off

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eforce123
Posts: 98
Joined: Sun Apr 08, 2018 9:27 pm

by eforce123

Anyone have issues with their strava and elevation differences? My fathers Garmon says we increase 2200 on a 25 mike ride and my strava says 3900?

Is strava off by that much?

by Weenie


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taodemon
Posts: 61
Joined: Tue Aug 29, 2017 2:04 pm
Location: Massachusetts

by taodemon

He is using a Garmin and you are on the phone app? There can be variations even between garmin devices. My dad's 520 always used to give him an extra 500ft of climbing compared to my edge 1000.

Aeo
Posts: 20
Joined: Wed May 25, 2016 2:06 am

by Aeo

It mostly depends on the GPS accuracy and the terrain that you are riding.
For example, if you ride on a windy road with steep cliffs on both sides, the GPS will sometimes locate you just a little bit to the side of the road and record the elevation from a few metres above or below. These errors accumulate and you get a super high total elevation.

kwakekeham
Posts: 65
Joined: Fri Jul 22, 2016 8:03 pm

by kwakekeham

Few points.

I've ridden a lot with 3 - 4 cycle computers simultaneously -- all with baro's. NONE have ever reported the same and in a lot of cases I've seen +/- 500m differences. There are reasons -- sometimes bad baro's (they are super cheaper components), sometimes the way the sun is shinning (elevation is a temperature corrected property) changes in pressure (storm), orientation on bike (gplama did an angle of attack test showing elevation can be messed up if wind can directly access the the baro hole), general access to the baro hole. Ride into a shadow area then back out, that temperature swing will look like going up then down.

Might want to ask what's true elevation.

Strava is not to blame at all in this case unless you're pointing the finger at the corrected data. So if you upload your garmin fit file to strava and then hit the "Correct elevation" it's generally more accurate. Why... I'm not sure which, but they either aggregate all "True" elevation data and average it thus creating a correction map that has trillions of data points and likely thousands to tens of thousands for the area or they use elevation maps. Neither is perfect. In ideal conditions a baro based unit can beat an elevation map for accuracy, but in most I'd say nope based on my experience thusfar.

Now if you recorded with the strava app it depends on how expensive your phone is. See a higher end phone has a barometer (check gsmarena for yours) like the garmin and a cheap phone does not. If temperature is stable a baro is good for +/-1 meter change or better, but if a storm front moves in and pressure drops it'll still think you're going up a hill (just like on a garmin). However on a cheaper phone without a baro it uses GPS elevation which is spotty at best and depends on reciever quality. Older units I remember around +/-25 - 50 meters, newer ones might be +/-5 - 10m depending on phone location, number of satellites, clarity of the sky, etc. But loss a GPS and wham! it just jumped 15 meters for no reason! Most now time delay filter to clean this up so you don't see those jumps. It just makes it harder to know when error is accumulating.

We can figure out where we are on a planet but we still suck at figuring out how high up we are.

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themidge
Posts: 902
Joined: Fri Jan 13, 2017 4:19 pm
Location: yer ma

by themidge

I live near the top of a hill, so according to the Garmin, most of my rides feature copious negative elevation :D. For some reason my Garmin takes my starting elevation as 0. Perhaps there's a way to tell it that I live at such and such an elevation and make it count from there, but then what if I don't start at home? :noidea:

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Calnago
Posts: 6616
Joined: Sun Nov 07, 2010 9:14 pm

by Calnago

@midge: Create a “location” in your Garmin. Call it “Home” or whatever you like. Use the known elevation (from a topo map or something) to set the elevation for that point. Then, whenever you start to record a ride from “home”, the Garmin automatically resets the starting elevation to whatever elevation you defined for your “Home” and goes from there.
If you don’t start from home you can still go through the same process to “set” the elevation at whatever current location you are at. You still need to know the actual elevation that you’re at however.
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AJS914
Posts: 2384
Joined: Tue Jan 28, 2014 6:52 pm

by AJS914

themidge wrote:
Fri Jul 20, 2018 12:54 pm
I live near the top of a hill, so according to the Garmin, most of my rides feature copious negative elevation :D. For some reason my Garmin takes my starting elevation as 0. Perhaps there's a way to tell it that I live at such and such an elevation and make it count from there, but then what if I don't start at home? :noidea:
Does your Garmin not have an altimeter? My 510 has always registered the proper elevation.

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themidge
Posts: 902
Joined: Fri Jan 13, 2017 4:19 pm
Location: yer ma

by themidge

AJS914 wrote:
Fri Jul 20, 2018 5:00 pm
themidge wrote:
Fri Jul 20, 2018 12:54 pm
I live near the top of a hill, so according to the Garmin, most of my rides feature copious negative elevation :D. For some reason my Garmin takes my starting elevation as 0. Perhaps there's a way to tell it that I live at such and such an elevation and make it count from there, but then what if I don't start at home? :noidea:
Does your Garmin not have an altimeter? My 510 has always registered the proper elevation.
I've nae clue :D It's a 500, perhaps it just uses GPS, but I'd be surprised. It must have some sort of way of measuring altitude or elevation gain/loss though, seeing as it gives me numbers.

by Weenie


AJS914
Posts: 2384
Joined: Tue Jan 28, 2014 6:52 pm

by AJS914

This says that you can calibrate it.

https://support.garmin.com/en-US/?faq=5 ... =noProduct

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