Harry's GPS Suite Forum

Hi,


I have an iPhone 8 running Harry’s GP edition version 23.0 with my track bike and external GPS Dual XGPS160.

I’ve been using the app for almost two years (love it) but recently I realized the lateral acceleration recorded is crazy, very erratic showing lateral acceleration of over 3g, any idea what may be the problem?

Thanks .... love the app btw

Below screenshots of how the graphs look

Lateral acceleration for motorbikes is actually calculated from downforce. This is necessary because lateral acceleration measurements will deliver around zero due to the lean. The disadvantage from this calculation is that it is very sensible to wrong mounting angles. See illustration #4 in Quick Reference. So the answer is “please check angles of your mount”.

In case this doesn’t work, please use. Calculation from GPS measurements: Lap List ‣ your lap ‣ Positions ‣ Recalculate Icon ‣ Acceleration.

Harry

Thanks Harry, I can’t use the proposed mounting angle in my bike, could I use an alternative mount and calibrate it instead?

Can I calibrate it directly in the track? Could you redirect me to the instructions?

Thanks!!!

Individual calibration is not working for motorbike mounting. It is optimized to calibrate lateral / longitudinal axles for cars while LapTimer uses the downforce acceleration to derive lean for motorbikes.

Which angles / mountain orientation would you like to use?

- Harry

Thanks for the clarification Harry.

My phone is currently mounted horizontally in the back of my sit with the screen facing me, you can see it on the below photos so you can get an idea.

This looks like it is correctly mounted for driving backwards? If not, try to adjust it like this. Goto Expert Settings and select flipping both longitudinal and lateral acceleration. This may work.

In case this doesn’t work, use calculated acceleration please. Select any lap from your session from Lap List. Select Positions / recalculate icon in the bottom / Acceleration and use the slider to get a realistic result. Confirm this calculation is applied to the whole session when asked.

Harry

Thanks Harry,


Let me play with it next track session and will let you know.

I was having a look to laps recorded last year and they look pretty good, the only difference is that I used to record the lap with my phone’s front camera, any idea why it was working well back then?

The red dots are my new reference lap taken last week (all erratic) while the white dots are almost 1 year ago.

Thanks!!

When recording a video, a different orientation is used. This means a different rotation matrix is applied. See www.gps-laptimer.de/documentation for the document "Acceleration Handling".

- Harry

That may be an option as well, I’ll give a try the next track session, flipping acceleration first and if It doesn’t work I’ll record the lap with video enabled.

I’ll let you know how I go, thanks!!