# Mounting a GPS/Compass
GPS/Compasses should be mounted on the frame as far away from other electronics as possible, with the direction marker pointing towards the front of the vehicle. If mounted in this way you can immediately proceed to compass calibration.
The diagram below shows the heading marker on the Pixhawk 4 and compass.
# Compass Orientation
The compass can be mounted in any of the standard MAVLink orientations defined in MAV_SENSOR_ORIENTATION (opens new window). The orientation follows the same frame convention as when orienting the flight controller.
If you're using the normal Compass Calibration process (with parameter SENS_MAG_AUTOROT enabled), the orientation should be detected automatically. Otherwise you can directly select the appropriate value in CAL_MAGn_ROT for up to three compasses.
You must mount the compass in a supported orientation!
If you mount the compass at an orientation that isn't supported, for example
Yaw 30, PX4 will detect the closest supported value.
This will result in errors/warnings, even if the calibration appeared to succeed.