Correcting G-forces for Device Yaw Angle

[aaronc7]

I don't record video with my phone, so usually I have the phone angled towards me when it's mounted in the car (vs mounted "straight forward) like the documentation recommends. This causes the g-force readings to be off a bit-- for example in hard straight line braking, there will be both linear and lateral (x and y) g-forces recorded and in the g-force plot in RaceRender or similar, it will not be in a "straight up" vector.

Minor annoyance/gripe, but I was bored one day so decided to do some of the legwork in hopes to maybe get it integrated into TrackAddict or RaceRender I am not sure what would be a better solution, an option in TA to "set" what angle the device is mounted offset to straight forward and all recorded values are pre-corrected, or something in RaceRender that you can correct all X and Y accel values with.

I did all testing with my phone in normal landscape mode, using TA where Accel X appears to be forward/back accel and Acces Y is left/right. The correction equation should be:

New Accel X = Accel X * cos(b) + Accel Y * sin(b)
New Accel Y = Accel Y * cos(b) - Accel X * sin(b)

where b is the angle of the phone in degrees in relation to straightforward. Positive values would be angled to the left (towards the driver in left hand drive).

Would be handy for me (maybe others)? to do this on the fly vs manually having to open up huge excel files and do the conversion, prior to importing into RaceRender.

Here's a little before/after video I did in my Tacoma (just braking in straight line to demo):

Before: https://www.youtube.com/watch?v=DeDu_JXU4_U

After: https://www.youtube.com/watch?v=A6eUgCzwYk4

[Weston@HPTuners]

The trick to auto calibration is that we look at which axis' gravity is acting upon (typically Z, and X/Y if there is any roll or pitch angle) and then calibrate based on that. When there's any yaw angle, there's no force upon that axis to detect, so there's nothing we can have the app do there.

We advise users to aim it straight, in line with the vehicle, knowing that hardly anyone is going to measure or know what actual angle they're really at, if not straight. If you do know that angle, it should be possible to add an approximate correction in RaceRender, using a calculated field.

[aaronc7]

I figured the RaceRender route would be easier and probably make more sense. Thanks for the quick reply- this would be a nice feature for me. I always mount my phone the same way and I know it would always be ~20 degrees. Worst case I'm guessing guys could "guess and check" values in the program and see the results in the preview screen before rendering videos.