In the case of BNO055, provided that the magnetic distortion is not too large on top of that little stick, then you can save the calibration profile when the vehicle is powerd off and reload it when it is powered on again.
However this only works properly is the vehicle is not moved significantly whil powered off. If the vehicle is loaded onto a trailer then powered on several hundred kilometers away, the magnetic field would not be the same in that location and therefore won't work.
Do you need the magnetic North as a reference ?
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