Sensor positioning on the airframe (pitch + roll compensated GPS + Magnetometer)

Hello! I hope I am posting in the correct category. We will soon build a conventional quadrotor using pixhawk 2.1 and px4. The quadrotor will transport a sensor that is mounted on a 1m long stick (axis = parallel to motor shafts). The sensor on top of that 1m long stick will be pitch and roll compensated (using two servos and the camera gimbal functionality), because it needs to be levelled all the time.Note that the stick itself is not pitch + roll compensated, but only the sensor on top of that stick.
For practical reasons I am considering to mount the GPS also on top of that stick. What will happen if I mount the Here+ RTK GPS (which includes the magnetometer) on top of that roll and pitch compensated stick?
I could imagine that the GPS data doesn’t suffer, maybe it becomes even better because it is far away from interferences and the antenna will always point vertically to the sky. Also the raw data of the magnetometer might become less prone to interference. BUT: Does PX4 assume that the magnetormeter tilts together with the accelerometer? Will it be confused when the copter pitches forward and the magnetometer reports no tilting at all?
If that is the case, would it be possible to disable the GPS internal magnetometer and add another external module that is NOT pitch and roll compensated?

Thanks a lot for your input!


The position offset of the GPS relative to the center of gravity can be compensated for by configuring the GPS position parameters correctly in the EKF.

Yes the firmware assumes that the magnetometer is fixed to the same rigid body as the IMU. However, you can turn off individual sensors so adding another magnetometer sounds like a good idea.

Ok, great thank you! That helps me to finish my design.
If I would attach a fourth (2xinternal, 1x external in GPS, 1x added Magnetometer) sensor that it would appear automatically in this tab?