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Thread: Garmin 810 elevation gain recording inaccuracy - request for help from yall!

  1. #1
    Mojo Bike Part Terminator Seths Pool's Avatar
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    Thumbs down Garmin 810 elevation gain recording inaccuracy - request for help from yall!

    Whats up everyone,

    OK SO -

    I dont know if anyone remembers, but I received a refurbished Garmin 810 as a warranty replacement back in march of this year.

    I have been noticing for a while now that I always have DRASTICALLY less elevation gains on rides than other people that ride the exact same trails with me on said rides. the majority of people I ride with use smart phones with strava to record their rides, so recently my mentality having a dedicated GPS device has been that their phones must be far less accurate than my dedicated GPS device, and their phones were just adding elevation gains to the rides.

    but after today riding with 3 completely new guys all with different models of phones (iPhone 5, 7, and Samsung galaxy 8) at the greenbelt, everyone had about 1560 +/- feet of climbing and I had 839. same mileage, but very different elevation gain, I believe my Garmin is the problem

    I have a rubber cover on my Garmin, and usually keep it in my small zipper pocket located on my hip of the camelback fanny pack. I have a Garmin handlebar mount but seldom keep it there because I currently don't have a lanyard for it and fear of it falling off and me not noticing it right away.

    I called Garmin customer support today, and the girl I talked to tried to say that everyone else phones must be wildly inaccurate because they don't use barometric pressure to record elevation gain. I didn't engage in a useless argument that had no way of proving myself right or wrong, but what I suggested (before I had to put the phone down for a second and the advisor disconnected) was that I bring 2 garmins with me on a single ride and compare the elevation gains to give evidence as to what the actual problem is.

    does anyone have a garmin 800, 810, 1000 etc that I could borrow for a single ride so I can compare the recordings of both side by side and try to get Garmin to replace this one I got from them if it is in fact the problem?

    or if anyone has any other ideas or info it would be greatly appreciated!

    thanks in advance

    -seth
    Last edited by Seths Pool; 07-14-2017 at 04:35 PM.
    "Less yap more braap"

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  2. #2
    MoJo Mother Superior FJsnoozer's Avatar
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    What is the recording setting on the garmin?

    Are the starting and finishing elevations the same when you look at the ride?

    My garmin has always read higher and more accurate than iPhone recorded rides. iPhone will give a slightly higher mileage. Segments are within 1 second and usually identical, except some don't pick up in the same place. I have even noticed this with different model garmins for segment pickup when there is a switchback.

    Sorry for rambling.


    Sent from my iPhone using Tapatalk

  3. #3
    MoJo Mother Superior yosmithy's Avatar
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    I have the 800 and run it on my bike, but always have strava running on my iphone 5s. The 800 usually reads a little less elevation than the iphone, but not that significant. Just looked at my ride this morning, and there was only 30 feet difference between the two.

    I can't remember if it was the 800, or my earlier garmin, but there was some sampling rate settings that you could adjust. Although, I would think Garmin would have gone over that with you on the support call.

    edit: Look at the recording settings on the garmin. Mine is set to "smart" and there's another option for 1 second.
    Last edited by yosmithy; 07-14-2017 at 05:12 PM.

  4. #4
    MoJo Mother Superior AntonioGG's Avatar
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    There are a couple of things that will throw off barometric altitude measurements.
    #1) When on the handlebar, it will detect air pressure from your speed as high pressure, which it interprets as lower elevation.
    #2) When the barometric pressure itself is changing, it will affect your altitude change.

    You can easily see both of those if you ride some loops for a couple of hours. For the first, if you slow down on downhills for some loops, you'll see the bottom of the descent higher than the faster trips downhill.
    For the #2 issue, you'll see your charts tilting up.

    For this reason, Strava, Trainingpeaks (and I'm sure other online services) have elevation correction. They'll correlate the measurements against USGS elevation charts based on the GPS positions.

    The Garmin tech support saying barometric is more accurate is BS. I'd almost say if you have accurate GPS points from the Garmin, and use the elevation correction freature (the phones will likely not have more accurate GPS points than the Garmin) that would be more accurate than the phones.

    You can go check individual climbs through mapmyride which uses USGS elevation info and compare vs your device. Personally, I can't get Strava and Trainingpeaks correction to correlate either, so I don't really get too worked up about even 300ft difference.
    cramsay3 likes this.

  5. #5
    MoJo Mother Superior Desert Nomad's Avatar
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    The STRAVA app updates the last few months seem to have fixed the issues of short-changing elevation especially when riding fast. I do not know what algorithm they are using now, but it is now pretty spot on. For example my walnut lap today on my standard route sans Endo read 772' of elevation using iphone STRAVA app whereas at the start of the year it would have been around half that. If you go through and add up all the climbing values for this whole lap, that 772 is very accurate.

    As mentioned, check your settings on your garmin, but the barometric pressure sensor way of figuring altitude gain may no longer be the most accurate method compared to whatever the STRAVA app is doing.

  6. #6
    MoJo Mother Superior coopers98's Avatar
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    Also consider that GPS/contour elevation tracking may in fact be less accurate than barometric sensor tracking due to smoothing/etc. If I 'correct' my rides from barometric to 'corrected' elevation, it ALWAYS adds a considerable amount of elevation. I'm typically inclined to trust the barometric readings over phone or 'corrected' readings anytime.

  7. #7
    Mojo Bike Part Terminator Seths Pool's Avatar
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    Quote Originally Posted by coopers98 View Post
    Also consider that GPS/contour elevation tracking may in fact be less accurate than barometric sensor tracking due to smoothing/etc. If I 'correct' my rides from barometric to 'corrected' elevation, it ALWAYS adds a considerable amount of elevation. I'm typically inclined to trust the barometric readings over phone or 'corrected' readings anytime.
    all I know is that with this stupid Garmin that I have, EVERY single ride I have about 500' +/- less than everyone else.
    "Less yap more braap"

    "Strava is like Tinder for bros"

  8. #8
    MoJo Mother Superior coopers98's Avatar
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    I'd wager your Garmin is more accurate. Let's ride Greenbelt and we can compare vs my 520

  9. #9
    Mojo Bike Part Terminator Seths Pool's Avatar
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    Quote Originally Posted by coopers98 View Post
    I'd wager your Garmin is more accurate. Let's ride Greenbelt and we can compare vs my 520
    Let's do it. I'm off sat-Mon every week!

  10. #10
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    Quote Originally Posted by Seths Pool View Post
    all I know is that with this stupid Garmin that I have, EVERY single ride I have about 500' +/- less than everyone else.
    Perhaps it's because you float above the trail and rarely actually touch it?

  11. #11
    MoJo Mother Superior AntonioGG's Avatar
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    Quote Originally Posted by coopers98 View Post
    Also consider that GPS/contour elevation tracking may in fact be less accurate than barometric sensor tracking due to smoothing/etc. If I 'correct' my rides from barometric to 'corrected' elevation, it ALWAYS adds a considerable amount of elevation. I'm typically inclined to trust the barometric readings over phone or 'corrected' readings anytime.
    I agree, with one exception: Garmin on the handlebar, and fast downhills. Try this on the road, get on a long downhill, displaying elevation, then in the fastest part, put your hand in front of the Garmin to block the wind. You'll gain elevation even though you're still going down.

  12. #12
    Live Medium Bamwa's Avatar
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    Quote Originally Posted by AntonioGG View Post
    I agree, with one exception: Garmin on the handlebar, and fast downhills. Try this on the road, get on a long downhill, displaying elevation, then in the fastest part, put your hand in front of the Garmin to block the wind. You'll gain elevation even though you're still going down.
    Dude is trying to kill you !!!!!!!!!!!!One handed Hill of Life! Only one hombre we know can pull that off!
    Spicewookie and AntonioGG like this.
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  13. #13
    MoJo Mother Superior FJsnoozer's Avatar
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    I'm suddenly having issues on my 1 month old 510. Rides have been Way off for the past two weeks. I am reporting around 60% of the elevation I should get. My normal identical loop in the GB was 500 vs 800. a very climby 10 mile ride that incorporated Kens reported only 800 when 3 other users with me had 1400.

    My sampling is on "smart" should this be on 1 second? I cant remember which is better.


    It is travel season for me. Could flying in a plane with the Garmin in my carry-on in any way affect it?


    Edit:The elevation has been off since I have installed a new fork and moved my K edge mount and stem down. I am grasping for straws here...
    Last edited by FJsnoozer; 08-08-2017 at 03:45 PM.

  14. #14
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    I quit using "smart" sampling because it was dumb. I use 1 second sampling. On really long rides you end up having to use smart sampling or it runs out of memory.

    Traveling on your carry on should not affect the accuracy. There is supposed to be a "zero pressure" reference built into the barometric pressure sensor. Unless it leaks, flying should not cause a problem.

    Suggest you google "Garmin barometric pressure" and maybe throw in or take out the model number. Lots of people are asking similar questions.

  15. #15
    Mojo Bike Part Terminator Seths Pool's Avatar
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    Well, so me and cooper rode jester trails together today, he has a bar mounted Garmin 520 and I have the Garmin 810. Our 7 mile ride had both of us within 50' of each other in climbing comparison.

    Me 778, cooper 732' of climbing in 5.9 miles.

    I keep my Garmin in the hip pocket of my camelback fanny pack and his is bar mounted with open air. So I guess this in my mind would settle it. You guys with cell phones are probably just getting a lot more climbing credit than what's earned! Lol
    coopers98 likes this.

  16. #16
    MoJo Mother Superior FJsnoozer's Avatar
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    My wife's cell phone was usually always less than my ride with a garmin. This was pretty consistant over the past year. Now that she uses tom tom, its slightly higher.

    I'm glad you got your's sorted. My ride yesterday seemed to give me a fair elevation, however, I did notice MTB bonnell was low and off by about 70 feet and my starting elevation was also too high by over 50 feet. I am going to try the process of resetting.

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