Jagged GPS recording with iPhone 13 mini

[jdujic]

My shiny new iPhone 13 mini has apparent issues with jagged GPS tracks, consistently adding some 2-5% to the total route length. For an illustration, check out the two runs of mine: the first from August recorded with iPhone 8, and the second from October with 13 mini:

https://www.strava.com/activities/7584918073

https://www.strava.com/activities/8025639130

The two tracks are supposed to be identical, and the physical difference should not exceed 20 m. Yet, the first shows up as 5.10 km, and the second as 5.31 km (therefore, making me appear faster than I am 😉). If you zoom in, you can notice the recording **bleep**-zagging, while the track is of course perfectly smooth.

While this is probably not a Strava issue, does anyone have an idea how I can possibly fix this?

As a feature request idea, Strava could probably implement some route smoothing by default for estimating distances. At least for faster activities such as cycling and running, it should smooth out such pesky gremlins.

[Jane]

Hi @jdujic 

To troubleshoot this situation, please try turning your phone completely off and then on as well as turning your location services off and then on again. Location services are located in settings > privacy > location services (turn off/on).

Also, sometimes GPS data quality can be improved by simply giving your phone more time to acquire satellites prior to starting your activity.

For more tips on how to improve your GPS quality see our article on Troubleshooting GPS issues for iPhone

If you find that the information above does not resolve the issue, please perform a GPS reset on your device:

GPS reset instructions:

1. Close all open apps on your phone.
2. Then go into settings and turn on airplane mode.
3. Next, go to settings > general > reset and choose reset network settings (you will need to re-enter your wifi passwords!)
4. Once your phone has reset, go to settings > location services. Turn this setting off and then on again.
5. Finally, go to settings > privacy > location services > system services and turn setting time zone OFF.

If you continue to experience the same trouble after performing a GPS reset, please let us know.

[jdujic]

Hi @Jane

It took a while to test it, but no, it did not solve the problem. I believe the problem is not in GPS as such, but in the algorithm how a gpx track is recorded and noise analyzed. Noise is immanent to GPS recording, but my particular GPS sensor seems to be more noise-prone, and it simply shows up in the traces.

There is, however, a well-known "noise cancelation" algorithm for GPS tracks known as Kalman filter. An excellent explanation and implementation can be found e.g. here. However, it seems that it is not implemented on Strava side either, and it should, at least as an option to post-process the data.

I've just tested Strava's "Correct distance" option on my recent hike, reported as 15.69 km by my iPhone (the correct distance is some 15.10 km, as previously measured by two separate smartphones), and it made a mess out of it, "correcting" it to 16.98 km. It seems something is seriously wrong there. A properly implemented Kalman filter can only shorten the reported distance, as it filters out all the wobbling, yet I've only seen the option increasing the total distance.

As a workaround for my problem, I ordered a Garmin watch as a present for my upcoming birthday. 😉 And I carry my old phone to my runs (hiking distance is of lesser concern).

[Jane · Accepted solution]

Hi @jdujic

Thanks for getting back to us. Our Support Team would be happy to work with you to investigate this further.

Please submit a support ticket and somebody will be in touch.

[jdujic]

A similar issue has been reported at

https://www.reddit.com/r/Strava/comments/k8n1t9