Why such different elevation corrections? (same route logg 1790m, 2615m, 3468m elev gain)

I rode with a friend the other day . I use a Garmin FR 305, he uses an IPhone. 

When I uploaded FR305 -> Strava, the elevation gain is 2,615m, see  http://www.strava.com/activities/138096662

When I uploaded FR305 -> Garmin Connect, the elevation gain is 1.790m (with elevation correction enabled)  and 1.724 m (with elevation correction disabled)  see http://connect.garmin.com/activity/494258370

My friend uploaded from IPhone Strava app , he logged 3,468m, see  http://www.strava.com/activities/138064391 (maybe this activity is not visible to public) 

The Garmin FR 305 is pretty accurate, I have compared data from Garmin Edge devices, and the difference < 5%

It would be good if it was possible to disable the elevation correction in Strava, it is not working very well. Garmin Connect. has the possibility to disable elevation correction even though it does a good job.  Maybe the elevation correction algorithm / database works fine in the US but where I am, it is no good.

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  • That appears to be correct, Liam. 

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  • To add: Please see the topic just created on Strava accepting the barometric altimeter data from the Wahoo RFLKT+.

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  • Well what I see with my datas and what I read here I think Strava got a serious problem with their own algorithms... not only elevation. 

    Elle Anderson you tell 2 years ago yours and GarminConnects site use same maps and other data for elevation correct? Its still same or some changes was made? 

    Because Its still really different between these two sites. Garmin shows me data as you when I upload first. After correction on both sites shows me huge differents. For example: GarminConnect: 1461m Strava: 1309m. Some times its much more around 500m different is almost rule.

    Why? How? If its still same as you say 2 years ago how is this possible? Cant be same as you see. 


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  • I have a similar situation. My device is a Sigma ROX 10.0, which uses barometric altitude measurements. I just rode a ride together with a friend. He was using the iPhone Strava App, I was using the ROX. He ended p with 1048m on the same track as many others, I had almost exactly the same values on my ROX when we arrived.

    When I uploaded my activity to Strava it underreported elevation by about 150m. Given the length of the thread it appears that Strava does have a material problem there. Of course the estimation for the calories burned will also be considerably off. That seems to be a consequence of the altitude problem. For reference - here's my ride with the faulty representation on Strava:

    https://www.strava.com/activities/724992647

    You'll find a few folks who have done the same ride and tracked it on Strava with the OS X app and seemingly good data. The average speed also shows a discrepancy. I was able to fix that by removing all the breaks before loading the data up on Strava. Now the average speed is in line with my GPS. This suggests that Strava's algo ALSO doesn't deal with breaks properly.

    Just so Strava support understands the impact (I hope someone is listening): there is not just the engineering problem that apparently hasn't been addressed, as a rider you also feel a bit cheated out of your effort. As it's happening all the time it leaves a bad taste in relation to Strava.

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  • Hi Jens, it doesn't work fine in the US. Same damn problem. Given the length of the thread I'm quite disappointed in Strava. Referring to the same Garmin database as they did in an earlier post doesn't cut it. Garmin doesn't have a problem with the data, Strava does with how they use it.

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  • Just to add to this thread.

    I rode with 3 others on Sat. I have a new Edge 820 and others used Strava app.

    Garmin logged 536m others logged 1080m,1143m and 1136m.

    https://www.strava.com/activities/779172986

    Strava has uploaded the device correctly. Device recorded 536m Strava shows 536m.

    Interestingly Google Earth kml elevation shows closer to 1000m not Garmin 536m.

    I'll try to correct the info.

     

     

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  • When will Strava roll out the new elevation correction method? It sickens me to have my elevation data shaved off because my device does not measure it while my friend's Edge 800 can use it's own captured elevation data without a correction. I don't care who is right and who is wrong, I just would like to see elevation data from Strava to be consistent for everybody. In another word, Strava needs to force a correction on everybody in order to be a fair game. The Leadership board has a category for elevation gain and it is a joke to see those with inflated elevation numbers from their devices make the top every week. Come on let's play fair, shall we.

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  • @ Vince:

    the problem is long known, for at least 2 Years. Starva applies a correction on all "non-trusted" devices, supposedly such without barometric sensor (including their own iPhone app), which puts them (like me, a Strava iphone-app user) at an advantage.

    Depending on the ride's profile, the mistake of elevation inflation can be >+100%, it is never negative.

    Its distressing I agree. Nobody seems to care though. I switched to alternative apps for logging, as the "challenges" are a joke due to the problem of wrong calculation

    Cheers

    Charly

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  • Charly:

    Yep that is the problem I see and would like to see a change so it will be a fair game for everyone.

    Not sure if some captured elevation numbers are 100% inflated, but my friend with his Garmin 800 had a ride a few months back that got 6,000+ feet captured, and out of curiosity, I remapped his route with ridewithgps and it only got around 3,700+ ft. Assuming ridewithgps is reasonable accurate, that is roughly 38% inflated, which is a lot. Now image if my friend and I try to complete for top spot on the Leaderboard every week on the elevation gain category, assuming we ride together the whole week, he would beat me every time, as my Strava corrected elevation gain would be shaved off significantly.

    The worst part is that Strava is using multiple methods to determine elevation gain data. As an exercise, I mapped a route on Strava's own route building that had around 1,800+ ft. I rode this route and uploaded it back to Strava. To my surprise, Strava activity corrected it to be 1,300+ ft. This shows that the system is pretty much f***up. I believe that Strava used to overestimate elevation data, and people were angry about it, so they decided to underestimate on purpose, but now that affect those of us rely on their correction. I guess that it is hard to make both camps happy.

    Again, I really don't care whatever calculation method being used here, just make it consistent and fair for everyone.

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  • Hello everyone,

    We are wrapping up an exciting project to address your concerns specifically regarding the accuracy of mobile elevation gain metrics. When we are ready to release more information, I'll be sure to keep this post informed. 

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  • Hi Vince,

    I found out long time ago and shared this on this site with Elle, that measurements done by an iPhone are quite accurate. I could verify that by analysing the gpx files produced using Excel.

    If you smoothen the raw  data,e.g. by disregarding elevation differences <1m then the whole thing is really precise.

    Other apps running on my phone, like MotionX-GPS do that really well and they do it locally without any server.

    The problem is with STRAVA, their server inflates the total elevation gained very well beyond any data contained in the uploaded gpx. Errors >100% have been observed, mostly the error is >20%. The problem is extreme when you ride alongside a sheer cliff, e.g. a coastal road with a sheer drop to the water. Obviously the Server sometimes calculates you being down in the water and in the next instant to be  back up on the road. Errors >100% are regular then.

    Interestingly the elevation graphs which STRAVA displays on the website seem to be accurate, only the total calculated elevation gain is crap. Posted this also.

    @ Elle: hope your improvement project will be rolled out rather than wrapped up. Any idea when we may expect improvement?

    Meanwhile I'm riding using alternative products.

    Ciao

    Charly

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  • Looks like this issue was never addressed, even though this post was some years ago. The difference between elevation data given by my Garmin, and given by Strava's "corrected elevation", is WILDLY drastically inaccurate. Among other rides, I was very disappointed when I did a 110 mile MTB race over the summer from Wolverine to Mackinaw City. I was giddy watching my elevation on my Garmin during the ride, only to my dismay when I uploaded the data to find it had been smoothed off 200 feet. This is not uncommon, I have had drastically different results using Strava even over the same climbs. Glad I don't care too much about my elevation gains!

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  • That is a very good news Elle! Although in my case it is the opposite that happens.

    When MTB riding with friends who have Garmin's barometric devices.
    I end with about 20-30% less elevation with my phones, either Android or iPhone.

    The elevation gain I get on my phone if I use viewranger.com for instance are more in line with Garmin devices.

    I hope the fix goes in both directions :)

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  • Check this one out. https://www.strava.com/activities/801275865

    Look at the elevation profile and you'll see my Garmin Edge 1000 has problems recording the elevation. The middle of the ride bears no resemblance to the actual ride and, while some of the hills that day were challenging for a fat old bloke from the flattest part of the UK, it never felt like I was riding up a 48% cliff. Or down it for that matter.

     

     

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  • @Owen, I would definitely recommend correcting the elevation manually for you activity. That's exactly what the feature is there for. Under the elevation statistic on the Activity page, click the blue link and select "correct elevation".

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  • Sorted, and an absolute life saver, I need this for work and it saves me a lot of time. Thanks.

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  • Another example of Strava Elevation Correction being significantly out of sync with Route Builder's estimated elevation.

    Here's Route Builder's detail for the route from Orford to Swansea on Tasmania's east coast:

    https://www.strava.com/routes/7398358

    We did the return journey and Elevation Correction gave a total ascent well under double that and about 25% less. Here's our ride with elevation correction applied:

    https://www.strava.com/activities/832269395

    It's not that big of a deal for us as we don't take this stuff all that seriously and think what you folks at Strava provide for our amusement is absolutely fantastic. Just thought that you'd like to know about inconsistencies in your software ... and it would be nice if things were more accurate. (For the record, our two Garmins originally measured our rides at 1200 and about 950 metres, so we thought we'd probably meet in the middle if we both did elevation correction, which is what has generally tended to happen in the past.)

    Cheers

    Doug Bruce & Dianne Batten from UnderDownUnder

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  • I'd like to send my congrats for Strava team for the great job they have done about elevation corrections here in Rio de Janeiro. Probably, it isn't perfect but the hay done a big huge great improvement. The elevations are now much more realistic. Thank you Guys. Well Done!

    May I ask you if Is it possible to correct the old data?

    Thx

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  • Still no updates on this? Im about ready to give up on Strava entirely. What is the point of using it at all if the data is inconsistent and inaccurate? I’m finding myself trying out different GPS/baro devices to see which ones Strava "trusts" to use elevation data from. Ridiculous! 

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  • @Justin V. I don't think your being "ready to give up on Strava entirely" (after being a member for 6 months) will really worry the folks that present and maintain the software. If you read the comment directly above yours you will see that progress is being made. And here in Hobart, it looks like applying Elevation Correction has made a significant difference in the last few months so from my limited test sample it looks like things are being sorted out.

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  • Doug, I didn’t realize my length of use of Strava has anything to do with the validity or importance of my feedback and usage. I pay for a Premium membership just like anyone that’s been here for longer. And for the record, I’ve been a Strava member for almost 2 years, I think the 6 months shown when you click a person’s name here is for the "Support" side of Strava.

    Good for you in Hobart. Here in Colorado, I’ve already lost 4,000’ in elevation this year across because Strava refuses to allow barometric elevation data from devices that aren’t on their mysterious "approved" list. Instead, Strava is replacing my barometric data with it’s own DEM data, and it’s quite off here in the front range of Colorado. 

    Quite frankly, I don’t think Strava should be so strict in allowing barometric altimeter data. If it’s in your file, it should be utilized. It shouldn’t matter what device recorded the data. At least then it’s up to the user to determine if their device is accurate and if they’d prefer to use Strava’s calculations or not. 

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  • I hear what you're saying Justin. My wife lost 100 metres off today's ride when normally she would have expected to gain about 200 metres. Certainly Strava does not always get it right, and for us it really depends on where we ride: more popular routes seem to have greater accuracy. Re the device issue, your argument seems reasonable. I guess what got up my nose is your comment about being "ready to give up on Garmin completely". I too pay for a Premium membership because it seems churlish not to. What a great resource Strava is. Yes, there are glitches here and there, but the community and richness of data is so fantastic. Really, does the elevation thing matter that much? Not that I don't think it would be good for them to get it right, especially before fiddling around with other things.

    Cheers and good luck with getting the elevation thing sorted. Sorry if I seemed a bit abrupt. It is a weakness of mine.

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  • There is a workaround that involves a bit of manual editing of the GPX file and forces Strava to accept the elevation data from the GPX file (regardless of what device it was recorded with) and not override it with Strava's corrected elevation. 

    To force the workaround you need to download GPX for your activity and edit it in any text editor. Look for the creator field in the beginning of the file that looks like creator="your device name here" and add " with barometer" at the end of the field. After editing it should look like this: creator="your device name here with barometer".

    Once done editing manually upload this GPX and voila! 

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  • I'm having an issue with Strava elevation correction. It simply doesn't work for rides over about 60km, it's been like this since of the start of 2017, before that it worked OK. I live in China and my Garmin 520 only shows vague altitude gain (you can see this when you create a segment and its not corrected) which is about a third less than Strava corrected data. I hit the blue button and it never does a thing to correct anything, tried multiple browsers.

    This is really aggravating as it sends my estimated power data and altitude gain right off making me seem like I did less climbing AND I'm less powerful than I really am. This makes me want to split my mega ride gran fondo into 5 different rides.

    Weirdly when I go to other countries Strava and my Garmin broadly agree, usually with the Garmin sightly overestimating.

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  • I am sorry if I have missed a thread but your elevation calculations are still shot!! - I have been riding with a friend on a regular basis now and we have set off on a challenge this week of 500 miles in a 5 day period both riding exactly the same course!. Well you would think as were riding together and the elevation;s are so different !! why is this>? we are both using gamins - a 100 and 810 please help. annoying,

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  • Ug. Lost 20% elevation gain versus Garmin watch on this mornings hill repeats. 

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  • 5 years later, this is still an issue.

    iPhone recording shows 178m, Garmin shows 69m.

     

    SORT IT

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