The primary role of on-board magnetometer sensor is to continously correct estimated heading using Earth magnetic field as reference of North-South direction. Magnetometer measurement however can be a subject of various distorions whenever foreign sources of magnetism are around.
In case where magnetometer measurements can no longer be assumed to be free from distortion from non-Earth magnetic fields, trust to its measurements should be reduced to reduce impact of these to AHRS orientation estimations.
The trust to each of magnetometer measurement component (x,y,z) can be reduced by increasing values of magnetometer measurement matrix coeficiences in relation to similar coeficiences for accelerometer and gyroscope sensors.
Analogically, when AHRS is operating in environment where no distortions are applied to magnetometer sensor, AHRS performance can be improved by lowering values of magnetometer-related coeficiencies.
The magnetometer measurement coeficiencies can be changed with use of SET_FILTER_MAG message.