Hi, I'm going to Cabo on Sat and plan on using my MP to film the whales. Did you have issue calibrating the compass because of the metal on the boat? Thanks
I think most people would advise you not to calibrate the compass on the boat. It's quite possible that if there's a lot of metal on the boat, the app might warn you of interference. However, calibrating at that point would only server to mis-calibrate the compass by compensating for the interference. Once the Mavic was up in the air and away from the interference, the compass would then be off due to the mis-calibration.
Here's what I would do: Do a test flight on dry land in the area you plan to fly, making sure there's nothing around to cause interference. If the app doesn't give you a compass warning, and if the Mavic flies fine as you test all the flight controls, then it should fly fine out over the water.
You really shouldn't need to calibrate the compass unless the app tells you to, and if you're sure it's not a false warning due to nearby interference. If you're worried that you'll need to calibrate due to distance traveled, I can tell you that I recently traveled from Sydney, Australia to Manila, Philippines (8 hour flight) and didn't have to calibrate my compass. My Mavic flies perfectly fine.