JJBspark Posted at 2018-7-8 10:46
Hi,

Had a look at your flightrecord, no errors in there.

Thanks for looking into this.  I really do want to understand what happened so I can know if this is a good idea to fly off of the boat or not.  Here's is what I know.
My boat weighs nearly 20,000 lbs.
There was a very slight breeze, one reason I wanted to do an "Asteroid" video at that time.
Would the boat move a little in that time sure.  But I practically live on that boat in the summer and am very tuned in to drift and motion.  As you can see from the Google map there are two other boats moored close to the one I'm on. This would give visual cues as to any motion, but again this is a heavy boat and the breeze was light so any motion would be both very slow and not of significant distance.
When I turned the drone back to the boat it was then travelling along the direction of drift of the boat but the Air was drifting off course toward the front of the boat which is not the direction of motion of the boat - the boat would have to be dragging it's mooring anchor for the Air to move toward the front of the boat.
Could the boat have drifted 29 feet in just over a minute, possibly that's pretty slow but I don't think that the breeze we had then was enough to move the boat that far. Again on the return to the boat the drone wanted to drift into the wind which is not the direction boat motion could account for.  The boat of course always faces into the wind when anchored / moored at the bow.
When I launched the drone was facing east toward the port side of the boat.
I moved the drone a few feet forward then let it hover while I switched modes for a quickshot.  (Didn't get that far before I noticed a drift again this drift was toward the bow of the boat and the drone was facing the boat so the drift was to the drones left (up wind)  That's what took it around the side of the boat making me have to move onto the deck to see it
When I brought it back to the boat I took it over the gunnel near the back end of the boat then turned to step out of the way.  When I looked back the drone was just coming into contact with a support strut striking with the left side of the drone. The distance the drone drifted in that short time was about 4 feet.  Then no more flying, 1 bounce off the gunnel and swim time.
FMI: I have flown drones off of this boat many times and routinely land them on a 2' by 2' deck table. this time as it was my first time from the boat with the Air I was using the entire deck space 13' x 7'.
All I want to know is: is the Air inherently confused/thrown off by slight motion before take off?
Oh one other thing I just remembered, I calibrated the Air's compass on the boat before taking off.
Thanks again to all and especially JJBspark for spending time thinking about this and offering opinions and facts.
Happy droning!

fans5760103b Posted at 2018-7-8 03:28
Good to know about the 90 degree tilt to stop the rotors.  When I'm talking about a "moving" vehicle here I'm talking about a barely perceptible motion.  When landing on the deck it's almost the same as landing on the ground because the motion is so slight.  That's one of the reasons I was surprised when the Air moved away after take off (Manual takeoff).  I could still control it but had to focus on compensating for the drift constantly.  When I looked away to clear deck space the Air moved sideways and clipped the boat.  I'm assuming that I released the stick and allowed it to drift for the < 2 seconds I looked away...

hmmm..  interesting behavior than..  i bet was just enough side to side movement on the boat surface to upset the VPS on bottom of your drone to cause it to drift away or become unstable.   

but im purely basing that on how my mavic pro behaves because if im on a boat and boat is only doing 2-5 mph once aircraft is over the boat and within 4.5 feet of the surface it actually moves with the boat unless its got to much side to side movement and bottom cameras cant lock on it drift away. but i always do hand catches whenever possible so that way little risk of it veering off.

Launching from a large moving metal platform will cause sensor confusion. The drone is designed to take off from a flat stationary non-magnetic platform.
You have the VPS using visual markings the take off point which is rocking side to side.
And then you have the GPS contradicting the VPS thinking that the drone isn't moving.
And then you have a vessel that may be heavily influenced by metals that may confuse the compass.

If you are going to launch from a boat - hand launch it. This will minimise any magnetic interference or compass warnings.

My final point is to never launch off a boat. If you have troubles launching then you will have bigger troubles landing.

HereForTheBeer Posted at 2018-7-8 14:44
hmmm..  interesting behavior than..  i bet was just enough side to side movement on the boat surface to upset the VPS on bottom of your drone to cause it to drift away or become unstable.   

but im purely basing that on how my mavic pro behaves because if im on a boat and boat is only doing 2-5 mph once aircraft is over the boat and within 4.5 feet of the surface it actually moves with the boat unless its got to much side to side movement and bottom cameras cant lock on it drift away. but i always do hand catches whenever possible so that way little risk of it veering off.

Hi,

In this flightlog is written that the VPS position is not used, VPS height is active. I think (don`t know if  i am right) that when the drone has good GPS signal VPS position isn`t used. Only when you have/get low GPS reception it will mode-down to OPTI or ATTI.

cheers
JJB

Tyredecals.com Posted at 2018-7-8 15:36
Launching from a large moving metal platform will cause sensor confusion. The drone is designed to take off from a flat stationary non-magnetic platform.
You have the VPS using visual markings the take off point which is rocking side to side.
And then you have the GPS contradicting the VPS thinking that the drone isn't moving.

Hi,

I agree on taking off from metal platfrom will possible cause sensor confusion, hand lauch good advice if your really want to fly off a boat.
MA is less 'confusable' then a Spark, in this case not a single compass or other errors in the record.
Just don`t understand what really happend to this MA.

cheers
JJB

fans5760103b Posted at 2018-7-8 13:34
Thanks for looking into this.  I really do want to understand what happened so I can know if this is a good idea to fly off of the boat or not.  Here's is what I know.
My boat weighs nearly 20,000 lbs.
There was a very slight breeze, one reason I wanted to do an "Asteroid" video at that time.

Hi,

Calibrating your MA at the boat? asking for troubles, i think that`s something you should never do (unless its a plastic boat)

It is good possible that you calibrated the ship`s 'magn values' into the MA, compass calibrated OK but actually not OK. When takeoff and away from magn influence MA must get different heading values, and starts drifing.

cheers
JJB

How about the IMU? Is any problem turn on the MA on a moving platform? Will the IMU get confused by the movement when power on?

I regularly fly off a steel motor cruiser.

1  place drone on a position with least magnetic interference.
2 turn on RC and drone.
3 wait for a gps  lock and the" your home point has been updated"
4 ignore compass calibration warning.
5 hold in hand above head  with front facing away from boat.
6 be on leeward side and not where drift or swing could catch you out.
7 start props
8 fly up and away from boat about 30 ft
9 allow electronics to catch up, compass error to go etc.

Enjoy flight

recovery.
1 havent done underway as rigging etc  would make  for a disaster.

2 have a clear area of deck
3 fly in above, i find 10mtr  ok.

4 land vertically straight to hand quickly so the compass error etc doesnt take hold.

Flying from a boat is great. NO TREES !

Also fewer wifi  or drop out problems

just remember be careful flying near the deck as sensors do not pick up the sea.

Of course you can.  

djiuser_CEdNxuNmFbIZ Posted at 2018-7-9 01:49
Of course you can.  

Amazing video! just the way he throws away that phantom !!! Catching need more practising   lol

I would never take off and certainly not LAND from a moving boat.  The drone uses GPS to stay in one place, the boat doesnt so they collide.That said, i fly off a boat 90% of the time but i make sure its moored.  The natural swell and swinging on the mooring isnt really an issue.
I do sometimes get IMU errors on startup if its a bit bouncy and occasionally it isnt as stable in flight if it didnt get a nice smooth place to go through its startups.

Last year i saw customers crash a total of 4 drones off the boat.  Some pushed the battery it RTH and landeded 3m to the side of the boat.  Others tried to land and the slight swell or swinging on the mooring caused them to collide.  Its why i ALWAYS hand launch and hand catch.

As for the boat being fibreglass, what about electrical cables or transmitters such as VHF or radar?  Those can do it too.

JJBspark Posted at 2018-7-8 22:39
Hi,

I agree on taking off from metal platfrom will possible cause sensor confusion, hand lauch good advice if your really want to fly off a boat.

OK but it's not a metal platform.  It's fiberglass.  There's metal below deck but insulated by the structure of the deck itself.

JJBspark Posted at 2018-7-8 22:46
Hi,

Calibrating your MA at the boat? asking for troubles, i think that`s something you should never do (unless its a plastic boat)

Boat is plastic but I'll try calibrating compass on land before I set sail anyway,...
Thanks for that thought.

djiuser_CEdNxuNmFbIZ Posted at 2018-7-9 01:49
Of course you can.  https://youtu.be/17RWWVnFij8

Impressive, gutsy...  Wow.
I wouldn't think a drone could manage that much wind.  I would say that any hand catch in that wind especially under sail is a good catch.  Not so much to grab on my Air though.  

gnirtS Posted at 2018-7-9 04:07
I would never take off and certainly not LAND from a moving boat.  The drone uses GPS to stay in one place, the boat doesnt so they collide.That said, i fly off a boat 90% of the time but i make sure its moored.  The natural swell and swinging on the mooring isnt really an issue.
I do sometimes get IMU errors on startup if its a bit bouncy and occasionally it isnt as stable in flight if it didnt get a nice smooth place to go through its startups.

Well in my case all electronics were down.
For the other launching and landing on that moving sail boat.  I doubt that they were interested in the drone staying in place.  If you can just constantly control the drone and the drone is responding normally you can steer it through any reasonable motion.  Or in the case of that video unreasonable.

For moving vehicle I used Profile mode. Please check at my video.

djiuser_CEdNxuNmFbIZ Posted at 2018-7-9 01:49
Of course you can.  https://youtu.be/17RWWVnFij8

Awesome vid and a new way to launch.. zero fs given though..
Pretty dangerous landing as he nearly decapitated the skipper. The props are inches from his eyeball..
The person catching it on the rebound wore loose thick clothing and gloves and prevented any injuries.

Ok i just had a successful test from my boat with the replacement Air. Lifted off hovered like a rock flew around a while, returned.  Air refused to quite come over the deck as bulkhead is too close. Put controller down walked over and picked it out of the air.  All worked as i would expect. Yay.