It's quite hard to say what is the definite case of your issues without more information, but here are some answers and common causes for issues : - The library that you are using is not from Bosch but from Adafruit, I do not know what is the default config. We always recommend to use the official BNO055 driver
- Heading drift in NDOF mdoe is almost always caused by magnetometer distortions. Please also log the acc, gyr and mag calibration statuses. The BNO055 cannot compensate for distortions of the magnetic field, only offsets. Therefore please place the sensor far away from ferromegnetic pieces.
-An offset between BNO055 heading (magnetic north) and GPS is expected, due to magnetic declination
- You data seems to have discontinuities in the heading which I would instinctively attribute to tilting. (especially around 520). I would recommend to use the quaternion output directly.
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