I have to complete my remarks. I have landed stable on my car but I cannot start from it. I get the red/yellow warning on the planeand the red warning in the app. The compass mod-value went up to 3500. When I took the P3 away from the roof the mod-value decreased to my normal 1450 and I could fly perfectly stable again.
So a "normal" nonmagnetized steel plate will disturb the compass only temporarily when it is in the very near vincinity.
If my compass mod-value rises above 2000 the red warning appears in the app and I cannot start the P3 anymore.
When I'm out in the open I will land the P3 again on the car and have a close look to the mod values.
