Auto sync OBD2 to GPS data

edited September 2 in General
I was so happy with this function when it arrived but I have had problems especially with the GR Yaris where the OBD2 data is quite some time off.

Yesterday I did some trackday videos and first I synced OBD2 data manually so it looked right on the phone. The I exported to video but then it looked a bit off? There are not two different places to sync data/GPS/video for viewing and exporting are there? Maybe I got lost syncing only one and not both sessions that were on the phone, I got a bit confused.

So I sat down and fiddled around both with manually syncing OBD2 data and trying the auto sync. Poking around I found the auto sync wanted to go minus 401ms. Manually setting it, the best setting was roughly around plus 400. This looked okay in both the phone and in the exported videos. Odd coincidence....

Comments

  • @MagnusThome There's certain conditions where the current way to synchronise gives wrong results. Please send me an example session, so I can test it against my development version that has some related changes. If your data has "internal sensors" enabled, that would be helpful too (for other reasons).
  • Curious how it calculates the optimal offset. I almost always have to tweak the offset a bit (e.g. 300 ms instead of 400 ms).

    Does it account for wheel slip? When threshold braking the tire speed can be substantially lower than GPS speed, and under throttle in corners the wheel speed can be substantially higher than GPS speed.

    Does it account for the car's speedometer being constantly off due to bad calibration, or different tire size? My friend has tires that are 1.5% taller than OEM, and the speedometer reads lower than ~1–2 mph than GPS when driving at highway speeds on cruise control, and we end up tweaking the GPS/OBD offset manually too.
  • It's a bit of math magic that I do not want to reveal to competitors :wink: Next year's major version will have something that hopefully works little bit better.
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