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Speed Display BUG: Head unit shows GPS speed, although the fit profile records sensor speed.

alanyu
over 4 years ago

The speed shown on 830 fluctuates a lot, when I ride on a 20-meter-long small bridge (<2% on both sides during a daily route, e.g, I keep 28~32 km/h, but 830 shows 14~38 km/h) for unknown reason, as there is no any covering (no buildings, only a few trees, on the flat aera, good sunny days, etc). This is one of the reasons I bought a Garmin speed sensor 2. However, after pairing with it, the speed shown on 830 is still the same, a lot of fluctuations. The speed sensor is 100% working and the battery is still good.

However, the speed data in the fit profiles are all sensor speed , as the speed data in GC or golden cheetach without smoothing have no any such fluctuation.

I also checked quite a bit fit profiles recently, including the ride which I went through a tunnel, or rode under a lot of trees, and I remember the "satellite lost" beeping and the funny speed fluctuaion with the the speed sensor at the same time. They are all the same: the displayed speed is given by GPS, while the fit profiles give a correct speed reported by the sensor

I tried to find the speed sensor priority in the setup again with the sensor connected and waked up, but couldn't find it anyway.

Please fix this bug. Adding a choice between GPS priority or speed sensor priority would be better.

  • 0 over 4 years ago

    It's a 80-meter-long small bridge, typo.

  • 0 over 4 years ago

    The speed sensor always has priority. Something else is going on here.You may need to go into the fit file to see what is happening with one of the fit file tools.

  • 0 over 4 years ago in reply to cheracogoff

    Do you really understand what is shown in golden cheetach without smoothing? That is the original fit file data points.

  • 0 over 4 years ago in reply to alanyu

    I 'm not familiar with Golden Cheetach. Does it show speed data for every second of the ride? Not just a chart. If so, then you have a very unique problem which I have never seen. Do you have the Garmin set for 1 second recording or smart recording?

  • 0 over 4 years ago in reply to cheracogoff

    Yes, both curves and points in Golden Cheetach. 830 is set to smart recording. This is not a unique problem. It (display GPS speed when paired with a sensor) has already been posted in this forums before and in other forums by different users. I decided to go through some fit files recently to check what is happening with my 830, and found this issue.

  • 0 over 4 years ago in reply to alanyu

    I recall when I first used my 705 Garmin years ago and I did not have a speed sensor. Every time there was any kind of tree cover the speed would fluctuate. When I started using a sensor that fluctuation stopped. I have a 1030 now and I have not seen any fluctuations like you are seeing. Is this just a 830 issue?  I've never tried this but I wonder what would show on the Garmin if GPS is is set to off? Does it show the sensor speed? Are you using Garmin sensors or another brand? Do you have the speed sensor on the front or rear hub?

  • 0 over 4 years ago

    @alanyu Can You share the FIT file of this activity?

    Are You pairing it via BT or ANT+? I have speed sensor 1 and via ANT+ it is working flawlessly with 1s recording (i have to use this speed sensor because the 530/830's firmware still buggy and without speed sensor the speed chart /and distance field and the strava is calculated the speed from the change of distances sec by sec/ is an awful jaggy...) 

  • 0 over 4 years ago in reply to cheracogoff

    I have stated clearly it is a Garmin speed sensor 2. It is on my rear hub. Never experienced a drop off msg.

  • 0 over 4 years ago in reply to Luko79

    ANT+ but it is smart recording. I will try 1s recording for next several days.

    drive.google.com/.../view

  • 0 over 4 years ago in reply to alanyu

    Where is the speed sensor , on your front wheel or on the rear? try the front if it is on the rear. How is the quality of the road on that bridge? Is it bumpy a bit? Because if the road has "wave form" and bumpy a bit that can fool the gyroscope in the speed sensor and measuring such a huge deviations (i had an experience in the past years before on a "bikepath" of a bridge , they made it undulated heavily for some reason and probably the "road wave" length was just similar as the rotation speed of the wheel  and with that bikespeed the speedsensor measured so off everytime i went through,  maybe if i were moving slower it would be accurate but i dont know it for sure, i just tried that bridge-bikepath once or twice in my life)

    update: i checked this bridge thing at me and i had the same problem with 45km/h and with 28km/h, so the problem could be the bumpy roads there , clearly seeing where the good road quality is turning to bad , the measuring is getting wrong.