I'm currently stationary in port, just wondering if my Mavic Air will refuse to take off with compass error from the 90,000 tons of steel. Even with a nice Helicopter landing pad.

I have the same problem taking off from a car roof.  Lots of metal, compass error.  Have you tried hand launch?

Lunch it from you hand, Compass should be fine

Is Mavic Air giving you a compass error or warning?

Yes, you can with hand launch. Just be sure that you have enough gps sats

Check is the ship allow you to fly drone in there or not first if you don’t want to get trouble. RTH won’t work because you are moving. So lost signal means your drone will land on water. Expected a lot of radio and magnetic interference on the ship. Likely that you will lose or crash you drone on ship.

You can check for Magnetic Interference two different ways:

#1) using GO-4 App

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How to get ready:

Under main menu of GO-4 App - in middle at Top of Screen - Tap on QuadCopter Icon
At bottom of MC Settings screen - Tap on Adance Settings
At bottom of Advance Settings screen - Tap on Sensor State
At top of Sensor State screen - Tap on Compass

Below Interference, you should see two compasses for Mavic Pro, and one compass for Mavic Air
Blue dot next to Compass (1 or 2) indicates which one is being used in case of Mavic Pro

Checking for magnetic interference:

After powering up your drone, and it completes startup.  What you want to see {and not see} at your chosen takeoff spot

You want to see short 'Green' bar(s).  {You do not want to see 'Red' bar(s) at all.  And it is best you do not see 'Yellow' bar(s).}

Link HERE
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#2) using 3rd-Party Apps available for Android & iOS SmartDevices
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All you need is a Smartdevice (iPhone, iPad, Android phone or tablet)  that you can download and install one of several Tesla or Gauss magnetic  field strength Applications on.

What makes this method easy is all you do is walk around area, observing  magnetic field strength.  No need to walk straight line with digital  compass or align your smartdevice running GO-4 with direction your drone  is facing, then check GO-4 compasses.

If you observe any major field strength changes upwards or downwards, usally reported in Gauss or µT (micro Tesla),  you avoid that spot as possible takeoff point or area for compass  calibration.  If you are going to takeoff from within that area, last  step is to check your chosen takeoff spot.  Done by lowering Smartdevice  down to ground, then moving smartdevice around spot looking for any  changes from what you previously observed over the area.  This last  steps checks for buried ferrous metals (aka rebar, steel pipe, scrape  metal) and underground power lines.


At link below are example screensnaps of two different Apps showing deviations from Earth's magnetic field by different sources of magnetic intereference.

Link HERE
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GDL brings up a good warning about RTH.   Even though your ship is stationary in port, if ship is not tied up at a Pier, and instead is anchored - very likely ship is swaying at anchor.

It worked fine! Some issues very close to the ship with drift just after takeoff but rock solid after.

Landing fine and no compass error on the helipad.

I launch of a boat all the time.  Just remember the home point is not the same... also you can swipe, from the right side of screen for quick menu to update the home point as you are going.. like if chaseing the boat.

Well after proving that you technically can fly off the back of a Royal Caribbean Cruise ship while in port, the ship's security don't want you to.

I can reclaim it for shore trips. Frankly it was nerve wracking flying from deck and I've got a bunch of shots so I'm OK with that.

brianoflondon Posted at 2018-8-13 06:53
Well after proving that you technically can fly off the back of a Royal Caribbean Cruise ship while in port, the ship's security don't want you to.

I can reclaim it for shore trips. Frankly it was nerve wracking flying from deck and I've got a bunch of shots so I'm OK with that.

Let that serve as a WARNING to all - Get permission first.  

brianoflondon Posted at 2018-8-13 06:53
Well after proving that you technically can fly off the back of a Royal Caribbean Cruise ship while in port, the ship's security don't want you to.

I can reclaim it for shore trips. Frankly it was nerve wracking flying from deck and I've got a bunch of shots so I'm OK with that.

Did you take off from Stern (back of ship) or from Helipad at front shown in first picture?

I did mention on the first to get permission before you fly. Don’t understand why people willing to take the risk just for a photo or video. This is not respecting the place you visit and give drone pilot bad name.

It’s cool to take a photo in special location. But more important is respect the local people and law. You are not just trouble yourself but also the others.

GDL Posted at 2018-8-13 07:07
I did mention on the first to get permission before you fly. Don’t understand why people willing to take the risk just for a photo or video. This is not respecting the place you visit and give drone pilot bad name.

It’s cool to take a photo in special location. But more important is respect the local people and law. You are not just trouble yourself but also the others.

"Don’t understand why people willing to take the risk just for a photo or video."

Quote from Princess Diana?  I take it you have never met a photographer/paparazzi?  Anything for the shot.  

Gunship9 Posted at 2018-8-13 07:18
"Don’t understand why people willing to take the risk just for a photo or video."

Quote from Princess Diana?  I take it you have never met a photographer/paparazzi?  Anything for the shot.

Both press and photographers need to understand: Even though they may have Right to take a photograph - that does not mean they have Right to do so by violating other people's Rights, harassing people to do so, or detaining people to do so - thus I am in favor of running over paparazzi who block people from driving away, along with flashing photo strobes at drivers impairing their ability to safely drive.  

I do risking myself to take photo when necessary. But I won’t looking for trouble. Some photo worth the life to take some are just stupid action. Wiser people can make the right decision.

People ignore the rules not only give us bad name. It will cause more and more restriction in the future.

its all over the Cruise ships terms and conditions , that under NO circumstances should you fly a drone from the ship either moving or stationary ,
please ,please ,please , stick to the rules as mud sticks where drones  are concerned..
and cruise companys will NEVER GIVE PERMISSION TO FLY, unless you are regestered and hold all the paperwork and even then its doubtfull ...

well you can but get the permission first