Hello rvillagrasa,
This would happen for BNO055. Because the situation on the vehicle is more complicated than on hand. If I rotate the BNO055 randomly, and then goes back to the original position, the yaw angle would differs from the beginning for more than 10 deg.
And the rotation rate on hand should be different from that on vehicle. For example, it may takes 1 second to rotate the BNO055 360 degree on hand, but it may takes around 10 seconds for the vehicle to rotate 360 degrees. And for gyro, long time means large bias integration. So the yaw angle bias on the vehicle is larger.
And the vibration on the vehicle should also be larger that on hand. That would be another main factor.
We still recommend to use NDOF mode for BNO055 to get yaw angle.
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