Why does my garmin always give a much lower total elevation compared to Strava

Home Forum Bike Forum Why does my garmin always give a much lower total elevation compared to Strava

Viewing 20 posts - 1 through 20 (of 20 total)
  • Why does my garmin always give a much lower total elevation compared to Strava
  • stevego
    Member

    I’ve a Garmin 800 and always get a much lower total elevation ridden on it compared to when Strava auto-corrects. The different is usually a factor of 2. Any ideas why?

    drofluf
    Member

    Probably because the Garmin uses barometric data whereas Strava will estimate your altitude based on your track and it’s mapping data.

    Premier Icon coolhandluke
    Subscriber

    I’d have thought that Garmin would use satellite data rather than a barometer.

    Satellite positioning is only accurate (to15mm or so) if atmospheric conditions are taken into account, otherwise it’s nearer 4 to 5m E, N and elevation, hence why your sat navs have your car icon going up a slip road of a motorway for a bit when you’ve decided to go straight on along the motorway.

    Usualy its the other way arround, strava tends to flatten small changes in elevation.

    Usualy I’d believe the garmin, I checked mine against an OS map for a fww rides and it was within within +/-5%, Strava was arround -40%.

    Premier Icon Bolt
    Subscriber

    Total ascent on strava is always less than what is on my bryton somtimes by quite a big margin!

    Bolt

    Premier Icon Paceman
    Subscriber

    Strava flattens out the ride from my understanding so total elevation recorded is often slightly less than actual.

    legend
    Member

    In mg experience Strava seems more accurate than my 819. I’ve kept an eye on the total ascent when climbing and watched it jump 5ft at a time when I’ve maybe done 1. Or maybe the red at GT does have 4,000ft of climbing…?

    Premier Icon ndg
    Subscriber

    Strava uses digital elevation data, so on routes where you are either climbing or descending I’ve found it to tie up pretty well with friends garmins. On routes with a alot of undulations (like trail centres) I find strava underestimates.

    zero cool
    Member

    Probably because the Garmin is actually accurate

    Premier Icon bigjim
    Subscriber

    If your garmin is using gps it will be very inaccurate. Strava will interpolate the route with something like SRTM data, this means it will still be pretty inaccurate, but fairly indicative. I keep meaning to interpolate one of my gpx with OS landform panorama data to see what the difference comes out as, I don’t have access to anything more accurate such as landform profile or nextmap DTM though.

    https://strava.zendesk.com/entries/20965883-Elevation-for-Your-Activity

    pdw
    Member

    Garmin 800 uses barometric which should be very accurate, provided it’s calibrated. Otherwise, you may see significant drift during the first 20 minutes or so of riding.

    Strava will do it off mapping data. This is particularly error prone on tracks that cross the side of hills, as small errors in position can lead to large errors in altitude.

    Generally I’d trust the Garmin.

    mduncombe
    Member

    see my post in this thread

    Elevation data on GPS and Websites

    Strava will use barometric elevation data from a GPS that supports it. Different websites apply different amounts of smoothing to that data, so that the value you see on the GPS screen will almost certainly differ from what you see on a website.

    Trimix
    Member

    Some Garmins can be set to do elevation from air pressure and / or satelites I believe. You do have to calibrate the barometer though.

    Premier Icon jezketley
    Subscriber

    It is odd. When I download garmin to strava, invariably, strava shows lower ascent and descent. Wherever I have ridden.

    stevego
    Member

    Garmin definately seems to flatten the rides, doesn’t matter whether on the mtb or roadie. Did a bigish road ride yesterday, the garmin gave 1100 m climbing over 130 km, strava about 2200 m climbing. Maybe it is the calibaration on the garmin.

    Premier Icon andytherocketeer
    Subscriber

    The only thing that needs calibrating on the Garmin is the current elevation at a specific point. That won’t affect total ascent/descent at all, only the absolute altitude.
    Unless it’s changed, all the Garmin does is sum up all the +/- changes from 1 data point to the next. Any “smoothing” or interpretation is down to how you set up the logging… Auto? Every N seconds?
    And then when you stick it in Strava / Endomondo / Mapmyride / etc. they then do their own interpretation of something that’s already probably been reduced according to an algorithm in the Garmin.

    In short… total ascent/descent is unreliable.

    When people say “i find my iphone accurate” or “strava accurate” etc… what are they actually using as a reference? Manual check of an OS map? or another app that interprets and smooths data?

    a value half or double that reported via another app/website is pretty normal IME.

    Premier Icon andytherocketeer
    Subscriber

    Just checked today’s ride
    Map says 440m up / 425m down
    Garmin says 385m up / 368m down
    Endomondo says 398 up / 368m down

    One of them is more right than the other. The start+end points are not the same and should be 15m difference.
    Last time I used Strava it made extra total ascent up even from the same data file.

    iolo
    Member

    Just enjoy your riding and Don’t worry so much about it. Life’s too short.

    Premier Icon bigjim
    Subscriber

    Garmin definately seems to flatten the rides, doesn’t matter whether on the mtb or roadie.

    that’s what I’d expect with a coarse elevation dataset like SRTM.

    When people say “i find my iphone accurate” or “strava accurate” etc… what are they actually using as a reference? Manual check of an OS map? or another app that interprets and smooths data?

    Count the contour lines crossed, divide by 2, multiply by 5m (or 10m or whatever the map is showing). That’s worked with both a Edge 305 and an 800, so I’d take the satelite data as being moderately accurate too. We had an old walking GPS on our boat as a backup (so should have read ~0m at all times) and it only ever recorded a few 10’s of meters in an hour, an insignificant ammount compared to an actual ride, unless you’re riding in Norfolk.

Viewing 20 posts - 1 through 20 (of 20 total)

The topic ‘Why does my garmin always give a much lower total elevation compared to Strava’ is closed to new replies.