ekf2_params.c: EKF2_MAG_TYPE: Info about yaw without mag

src/modules/ekf2/ekf2_params.c

@@ -490,7 +490,7 @@ PARAM_DEFINE_INT32(EKF2_DECL_TYPE, 7);
  * If set to '3-axis' 3-axis field fusion is used at all times.
  * If set to 'VTOL custom' the behaviour is the same as 'Automatic', but if fusing airspeed, magnetometer fusion is only allowed to modify the magnetic field states. This can be used by VTOL platforms with large magnetic field disturbances to prevent incorrect bias states being learned during forward flight operation which can adversely affect estimation accuracy after transition to hovering flight.
  * If set to 'MC custom' the behaviour is the same as 'Automatic, but if there are no earth frame position or velocity observations being used, the magnetometer will not be used. This enables vehicles to operate with no GPS in environments where the magnetic field cannot be used to provide a heading reference. Prior to flight, the yaw angle is assumed to be constant if movement tests controlled by the EKF2_MOVE_TEST parameter indicate that the vehicle is static. This allows the vehicle to be placed on the ground to learn the yaw gyro bias prior to flight.
- * If set to 'None' the magnetometer will not be used under any circumstance. Other sources of yaw may be used if selected via the EKF2_AID_MASK parameter.
+ * If set to 'None' the magnetometer will not be used under any circumstance. If no external source of yaw is available, it is possible to use post-takeoff horizontal movement combined with GPS velocity measurements to align the yaw angle with the timer required (depending on the amount of movement and GPS data quality). Other external sources of yaw may be used if selected via the EKF2_AID_MASK parameter.
  * @group EKF2
  * @value 0 Automatic
  * @value 1 Magnetic heading