I have been a Marine Photographer for many years in the Rio de la Plata and Parana River area and my first drone a P2, I lost in the water of the Parana River trying to land it on the deck of a (slightly) moving boat. Now I just got a P4 and find it works flawlessly except that I usually take off from commercial boats or ships which are all metal. How bad is it if I cannot calibrate the compass every time I fly? This is my first flight on the water with my new drone yesterday. Thanks for any feedback on compass calibration!