Flying from a boat

Discussion in 'ALTA' started by alex ryan, Jun 24, 2017.

  1. alex ryan

    alex ryan Member

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    i have a job coming up where I will be launching from a boat about 4nm off shore.
    I have never flown from a boat this far from land before.
    Usually I would do a compass calibration on shore before boarding the boat.
    Do you think it would be wise to do a calibration on the boat?
     
  2. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Alex, to rewrite your question slightly: "If I'm on board a metal boat that's going to distort the Earth's magnetic field, is it wise to calibrate the compass and "bake in" any errors that the boat will cause?" :):)

    If it's a wooden boat, then it's not likely to distort the Earth's magnetic field much, but there may be metal in the superstructure.....

    Bottom line: Depending on how far away you are from the on-land point where you do the calibration, and provided that you find a suitable place for doing the calibration (not near metal structures, reinforced concrete, cars, railings, and volcanoes) then I'd calibrate it on land.

    Be sure to read up on "Motion booting" while you're still on-shore, too!

    Hope this helps.
    Andy

    Forensic Software & sUAV / Drone Analyst : Photographer : Videographer : Pilot (Portland, Oregon, USA): Trees=2, Ground=1, Props=11. :(
    The Ground Is The Limit™
    ---------- Forensic Drone Analyst : Forensic sUAV Analyst : Forensic Unmanned Aircraft Analyst : Forensic Drone Expert
     
  3. alex ryan

    alex ryan Member

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    Good point.

    We will be about 8km or so from the shore where I will be able to do the calibration away from things that will distort.

    Do you think that that calibration will be accurate enough for the new location?

    If not, got any suggestions?
     
  4. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Hi Alex:
    Yes -- the underlying point of compass calibration is to deal with compass "variation" (sometimes called "declination" -- the errors between true north and compass north) and let the Hall Effect compass (aka flux gate magnetometer) figure out which way is North.

    Have a look a a map such as those on this Wikipedia page and you'll see that apart from locally induced errors from metal structures and the magma in volcanoes (don't laugh, there's a specific warning re: compass errors for Mt. St. Helens near where I live -- magma has a lot of ferrous iron in it), the magnetic variation varies quite slowly with respect to distance.

    So just be sure that you are, meh, 20 - 30 yards from the nearest chunks of metal when you calibrate the compass. Out of an abundance of caution some folks remove the keys, small change, etc. from their pockets when they're doing the calibration. I just leave my magnetic personality in the car. :rolleyes:

    Hope that helps.
    Andy

    Forensic Software & sUAV / Drone Analyst : Photographer : Videographer : Pilot (Portland, Oregon, USA): Trees=2, Ground=1, Props=11. :(
    The Ground Is The Limit™
    ---------- Forensic Drone Analyst : Forensic sUAV Analyst : Forensic Unmanned Aircraft Analyst : Forensic Drone Expert
     
  5. alex ryan

    alex ryan Member

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    Great. So if I understand you correctly the effect distance has on compass errors is relatively low? (At least when compared to your personality).

    Just out of curiosity if distance was the only factor at play, how far would you have to travel for the compass to need recalibrating?
     
  6. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Yeah -- you're really asking "by how much does the Earth's magnetic field's deviation change with respect to distance" -- and generally speaking, it's not much. The bigger risk is that you calibrate in a place where the field is distorted and that throws off the ALTA's compass because you "lied" to it which way is north. In Oregon, the deviation is 16 degrees East -- the compass points 16 degrees east of true north -- enough to get you killed in a manned aircraft if you're flying using a compass to navigate by.

    Far enough that the Earth's magnetic deviation causes a major error -- that's where the maps in the link I put in my previous posting are relevant. Sorry to sound like that's a non-answer, but it's the truth. No covfefe here! :)

    Andy

    Forensic Software & sUAV / Drone Analyst : Photographer : Videographer : Pilot (Portland, Oregon, USA): Trees=2, Ground=1, Props=11. :(
    The Ground Is The Limit™
    ---------- Forensic Drone Analyst : Forensic sUAV Analyst : Forensic Unmanned Aircraft Analyst : Forensic Drone Expert
     
  7. Jason Toth

    Jason Toth Active Member

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    We fly off boats constantly, doing it right now actually. Calibrate on the shore away from metal objects (keys & phone in your pocket apply). Do not do this on the boat :)
     
  8. alex ryan

    alex ryan Member

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    Ok so just did the job and it was a success. We calibrated on shore. We were flying about 8-10km off shore.
    We were filming whales that put on a massive show for us. It was amazing.
    Everything was working as it should, but when I flicked it into position mode the Alta started flying south. Do you think this was because the compass and gps were giving conflicting readings?
    It was fine. I just flew without gps, but gps would have been helpful at times.
    I took off the distance restrictions and had motion booting on. Gps worked perfect on shore.
     
  9. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Alex: That's odd. I checked the solar weather (n3kl.org) for the Estimated Planetary K Index (sometimes known as the Kp Index) and Mr. Sun has been very quiet since June 27 -- so that rules out GPS errors induced by a solar storm.

    Is there a chance that you might have a transmitter trim set on the right hand stick that would cause a drift?

    When you went into position mode, did it head south aggressively or just drift South?

    Andy

    Forensic Software & sUAV / Drone Analyst : Photographer : Videographer : Pilot (Portland, Oregon, USA): Trees=2, Ground=1, Props=11. :(
    The Ground Is The Limit™
    ---------- Forensic Drone Analyst : Forensic sUAV Analyst : Forensic Unmanned Aircraft Analyst : Forensic Drone Expert
     
  10. alex ryan

    alex ryan Member

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    It wasn't aggressive, just a drift, but quick enough to notice straight away.
     
  11. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Hmm. Most likely candidate is a trim issue. Normally GPS instability shows up as the ALTA flying in small circles. In the technical community this is known as "toilet-bowling." :rolleyes:

    Andy

    Forensic Software & sUAV / Drone Analyst : Photographer : Videographer : Pilot (Portland, Oregon, USA): Trees=2, Ground=1, Props=11. :(
    The Ground Is The Limit™
    ---------- Forensic Drone Analyst : Forensic sUAV Analyst : Forensic Unmanned Aircraft Analyst : Forensic Drone Expert
     
  12. alex ryan

    alex ryan Member

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    The only other thing I can think of was position mode was working correctly and it was the movement of the boat that I was witnessing, but I could have sworn it was the Alta that was moving.
     
  13. alex ryan

    alex ryan Member

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    If it was a trim issue wouldn't the same thing be happening in all flight modes?
     
  14. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Not necessarily -- I find that experienced pilots automagically compensate for small trim settings just because they're flying the aircraft visually and deflecting the sticks to achieve the required result.

    As to whether the boat or the ALTA was moving, that's a tough question. You rapidly get into Einstein's Relativity and Mach's Principle (https://en.wikipedia.org/wiki/Mach's_principle). :)

    Andy

    Forensic Software & sUAV / Drone Analyst : Photographer : Videographer : Pilot (Portland, Oregon, USA): Trees=2, Ground=1, Props=11. :(
    The Ground Is The Limit™
    ---------- Forensic Drone Analyst : Forensic sUAV Analyst : Forensic Unmanned Aircraft Analyst : Forensic Drone Expert
     
  15. alex ryan

    alex ryan Member

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    Good point. I do have magic fingers. At least that's what she says.
     
  16. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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  17. Mike Reid

    Mike Reid Member

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    On boats, I have done this 2 ways.

    First way calibrating on land then turn on motion booting, bring it on the boat and it works no problem.

    If I know that I will be flying all day I will boot on land then bring it on the boat and keep it powered all day, hot swap batteries between flights and keep it on the whole time.

    I've never had an issues using either method, probably 100's of flights done each way. Now just perfect your hand catches for when you have rough seas!
     
  18. Dylan Glockler

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    Hey Mike,

    ** Nevermind - correction to below, I was looking at your join date.. not the post date ** pretty recent tips .. have to do some research to see if there's any way to boot up on-board, very often we won't have the option of booting on shore.

    I read your post from a few years ago - sounds like you have a lot of experience flying from boats - any updated tips/experience/changes? I'm moving onto a 70 foot boat and looking for the best/safest way to launch and land. Unfortunately there is no great/open spot to launch or land on the vessel as it's a motor yacht but has backup/stabilization sails, so a lot of rigging to get in the way!

    Was thinking of building some kind of launch platform that can mount to the outer railings and then hand-grab-land.

    I have an Alta 6, Movi m5 and for those fun and easy flights or preflight vis - DJI Mavic.


     

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  19. Jason Toth

    Jason Toth Active Member

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    Hi! Yeah flown off a boat once or twice :)

    The Alta SUCKS for landing/taking off from a boat cuz the landing gear!

    Here’s some tips
    - make a 8x8 deck out of 2 sheets of play wood. 8 foot might sound excessive but when the winds are blowing and the boats a rockin you need all the space you can get!
    - put some rubber ends on the bottom landing gear. Better yet come up with a way to have four legs instead of three, the three legs have a tendency to make the drone tip over, and on a boat that is no Bueno :(
    - make sure motion bootin is on & the boat is not traveling when taking off-Landon, the wind is going away from you, take off in manual pretty much full throttle get the fucker up in the air around 30 feet away from you and water and put it immediately into GPS . Once you’re settled then fly ATT or GPS.
    - landing is the tricky part, I land in GPS only, you’ll have to adjust for the wind and the waves, be patient and don’t rush it. Again the movi landing gear suck on the boat so coming up with something that has four legs instead of three is huge!
    - Also make sure you’re landed by 21.6v (3.6v loaded).
    - depending on weather conditions and how risky you are you have to make the call on whether to go up or not. Light rain and constant winds up to 15 kn are doable, but if it’s gusting make your own call. Last week I didn’t listen to my gut and decided to take off in gusting winds, as soon as I took off I mediately a boarded the flight and it took me 10 minutes to land back on the boat - it sucked :(

    Later, J
     
  20. Mike Reid

    Mike Reid Member

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    One other tip to add onto Jasons. I use the TITH extension when flying from the boat when I know that I have times when the only option will be hand catching. The extension gives you enough room to reach up and grab the space between the gimbal and the alta, then get a second hand on either part for extra support.

    Definitely, practice on land before jumping into it, but it is a lot safer than it sounds.
     

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