Hi joshld, Maybe it would be a bit easier for us to help you if you could explain a bit more in details what you are trying to measure, the required accuracy and range of expected motion of the device. In case of relative heading, indeed the IMU mode is a good choice, but only for a limited amount of time. Since the original post mentioned durations in the hours range, then the use of a magnetometer (or other) is paramount to calibrate the inherent heading drift with the integration of the gyroscope signal. Typically, the magnetometer data is used, but in cases where the magnetic field cannot be trusted, heading can be compensated with a GPS system, or complemented with cameras to name a few methods of compensation. If the rotation speed of the device does not exceed a few degrees per second, then the gyroscope is not necessarily required, and heading can be derived from accelerometer and magnetometer only (Compass and M4G modes) o_o
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