Important. To avoid problems with inspire compass. Remember to calibrate the compass on the iPad for each flight. Possible that the directional arrow indicates the wrong direction in Dji pilot app certain compass not to ipad calibrated.
If you are not promted by the pilot app to do it (I only do it when the app prompts me using the calibration sequence that is automatically generated) you can start the integrated compass app in the device and calibrate it from there ...
It asks you to calibrate as soon as you open it. At least on the version I am running.
This goes for iOS!