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Weird bumps in the speed from GPS

NetQvist
over 2 years ago

Has anyone seen something similar to this? On Strava my speed looks like this, it didn't use to do this and some days it's worse and some days better. The average seems to even out however. The roads here are quite flat and I can't figure out anything that should be causing this from my actual riding.

Should be 1 second recording also and not smart.

On Garmin connect and intervals.icu it's flat but I tried to export the activity and open it in some random editors and the same spikes were there as well so I guess some tools average it out.

i.imgur.com/fDHPgiH.png

  • 0 over 2 years ago

    Hi, I have similar problem but I am using speed / cadence sensor.

    Kind of solution is to use "Correct distance" option in strava.

    Original:

    After clicking "correct distance" option:

    Source:

  • 0 over 2 years ago in reply to 4699266

    with speed sensor You shouldnt get any issue on Strava speed chart. are You sure that is it working properly? :) the battery and the signal strength/quality could be problem (some sensors are not working good on rear wheel only on the front one). If You share the FIT file here, i can read out these datas 

  • 0 over 2 years ago in reply to NetQvist

    i lent my 830 to my GF a few days ago and she rode without speed sensor , it is a stock 9.40fw, without any CIQ app, no BT, nothing, and master reseted , fully formatted, manually reset everything (so no backup files ) on a clean unit, and there are "cracks" in every 1 minute... (it is the result of the duplicated GPS positions in the FIT file and faulty distance field datas) this Edge programming team is a joke , as we experiencing it since 10 years apprx... 

  • 0 over 2 years ago in reply to Luko79

    Thanks for reply :)

    I'm using Sigma Rox 11 and Bontrager DuoTrap speed / cadence sensor.

    Pretty sure it is working fine. Battery is new and in software (source) before uploading to Strava it is looking ok.

    https://poliweglan.eu/~gtc/sss/log/2022_07_14__18_06.fit

  • 0 over 2 years ago in reply to 4699266

    ahh, sigmarox, that is a garbage (sorry to say it), with powermeter there is no enough power resource in the unit to record every sec and it causing lagging and incomplete recording . one of my friend had this SR11, an another one had the SR12 (both got them as sponsored riders...), both were junk, they thrown them out after 1y and bought Edge 530s (which has problem too as we see but at least it works/records good with powermeter). probably the Sigma is also ok without sensors (and only with GPS datas), the older Brytons had this issue too , so it is not only Sigma-related.

    I will analyze your FIT file later today, i am sure i will find "nasty" things in the file! (and i will show You for sure:D)

  • 0 over 2 years ago in reply to Luko79

    Thanks!

    I'm using Sigma for a 3-4 yrs now and it was ok (only missed navigation).

    "with powermeter there is no enough power resource in the unit to record every sec and it causing lagging and incomplete recording" - thankfully I can set the device to record every 1, 2, 5, 10s, (currently set to 2) and I did change it from 5 to 2 last summer so maybe You are right! :)

    However if that's the case - shouldn't the spikes be visible in the source graph as well?

    Edit:

    When I ride and when I look at the sigma - everything is also very smooth.

  • 0 over 2 years ago in reply to 4699266

    As i checked it is not 2sec, it is sometimes 2s , sometimes 3s, but not constant. As i know You cant set it to real 1sec , the possibility is exist in the menu but the unit cant record with stable 1s rate. and it is a huge problem.

    The speed graph (on the bottom) is drawed from "speed" datafield and that is nice. But the Strava is drawing the speed graph from the change of the "distance" datafield, and probably it is problematic in the Sigma FIT file too . The Strava correction what You mentioned is changing this calculation method and the Strava recalculate the distance values from the recorded GPS LAT/LON positions and will draw the speed chart from this recalculated distance datafield. 

    the situation is the same with the Garmins too, if you check the speed chart on Garmin Connect, that is looking good, because that is drawing from the "speed" datafield too 

    here is a quick view from your FIT file, as You see, there are 2secs and 3sec gaps (and these are continously changing in the whole file), and not stable 2s gaps as you set