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Question re: Compass calibration on a boat
2290 15 2015-6-14
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Krafty
lvl.2

Singapore
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I am headed off on a liveaboard diving around the Maldives for 8 days and I am pretty stoked to be taking along my P3. I am concerned about doing a compass calibration on a boat which is made almost exclusively of metal. We will also be travelling quite long distances each day/night as we dive without heading to land, so I am not sure how I can calibrate/fly safely.
Any tips would be greatly appreciated.


2015-6-14
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Willie Wonka
First Officer

United States
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The boat has to be anchored and test the compass of an iPhone or an android plus a regular compass and compare it with the boats compass, it scares the hell out of me just thinking about it but good luck.
2015-6-14
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BobbyB
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United States
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You could take a small inflatable boat with you and paddle away from the dive boat to do the compass cal.  However,  you'll likely have electromagnetic compass problems if you try to launch and land back on the main vessel.  
2015-6-14
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Krafty
lvl.2

Singapore
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So should I just leave it behind? Would be a shame if I had to do that as it makes me drool thinking of some of the footage I could get. If I could calibrate on the ground before we got on the boat? just taken a look, max distance would probably be 30-40km from where we get on the boat.
2015-6-14
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labroides
Captain
Flight distance : 9991457 ft
Australia
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DON'T calibrate on a steel boat.
Calibrate somewhere on land - 30 km away would be fine.
Calibration is so your Phantom understands the local magnetic environment where it is going to be flying.
Calibrating for the distorted magnetic environment close to the boat won't help you at all.
2015-6-14
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Willie Wonka
First Officer

United States
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labroides@yahoo Posted at 2015-6-15 11:12
DON'T calibrate on a steel boat.
Calibrate somewhere on land - 30 km away would be fine.
Calibration ...

Yeah thats a best bet as i tried reading my electronic compass inside the car it was 180 degrees the other way, so calibrate it at the closest location you can be at to where you are going to be flying, BUT then taking off from an unstable magnetic location is another question?! is it safe ? is the P3 going to start going all over the place because it can't stabilize itself because of the incorrect reading from the magnetic field of the boat?
2015-6-14
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Krafty
lvl.2

Singapore
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Cheers guys, guess I will have to think fairly carefully whether to take it knowing it will be a risky operation.
2015-6-15
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kudlaty
lvl.2

Poland
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The main problem is not with the compass. Much more important is that you should NEVER initialize Phantom on a boat (or any other moving surface). Multiurotor depends on two main sensors - gyroscope and accelerometer. Compass is important for navigation, but quad can fly without it.

When you power up your Phantom, it stores actual signal from the gyroscope (this is called gyroscope bias), assuming that quad is not moving(!). So if you power up the Phantom on boat, every small movement will introduce error to signal from gyroscope, resulting in storing incorrect bias value. This may lead to severe drifting and flyaway or crash. Of course Phantom is, to some extent, able to detect that gyroscope bias value is incorrect, but only if the movement during IMU warmup was big enough. Much more smaller movement may destabilize Phantom after takeoff.

If compass will start to give abnormal readings, you can always switch to ATTI. But if your quad have incorrect gyro bias value stored, switching to ATTI won't help.
2015-6-15
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aburkefl
First Officer
Flight distance : 78612 ft
United States
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Krafty Posted at 2015-6-15 17:47
Cheers guys, guess I will have to think fairly carefully whether to take it knowing it will be a ris ...

Are we making mountains out of mole hills? Can the compass really be *that* important? That said, I understand your reluctance to risk your Phantom and I wold also hesitate, but....

One poster makes the argument (a persuasive argument, I might add) about the gyroscope, accelerometer, etc. Seems like those would be far more important than the compass. Can our Phantoms be relying so much on the compass that the GPS can't tell us where North is North?

I have a friend who owns a moderately old Blade 350. He has launched and retrieved many, many times from a small, moving boat - sometimes as fast as 25 mph - with nary a problem. It just seems bizarre that a much less sophisticated craft like the Blade can do something like what's proposed and there's danger that the Phantom cannot?

Please don't get me wrong. I'm not pooh-poohing the defenses proferred - just trying to understand how these things tick. Some of the logic seeming defies logic - "...hey guys, drop me off here and go away 20 km then come back and get me - I need to calibrate my compass." Then later, you'll have no option but to launch and retrieve from the boat? I'll bet Mr. Spock would tell us that sounds illogical.
2015-6-15
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Willie Wonka
First Officer

United States
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aburkefl@gmail. Posted at 2015-6-15 19:51
Are we making mountains out of mole hills? Can the compass really be *that* important? That said,  ...

LOL you crack me up....  its always a risk, like me flying my hex 2000 feet in the ocean with a big chance it might fail and loose it completely with no chance of recovery, It is a risky world out there and to achieve greatness one must gamble.
2015-6-15
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jsdrone
lvl.1

United States
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hi everyone..... I live on a boat and fly my quad copter off it all the time.... I have a mariner made by fpv factory and it has all the same electronics the phantom has... I would not do the compass cal down below as it might interfere with the vessels auto pilot electric compass but if u do it from topside u will be fine... differnts is mine is water prof and yours is not so dont land it in the water but would love to see your footage.... if u go to you tube and look up rick moore.... he is in the bvi flying the mariner off everything that floats.... good luck an make sure to post your footage

capt. john
2015-6-15
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QuadKoppta
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United States
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Krafty Posted at 2015-6-15 10:03
So should I just leave it behind? Would be a shame if I had to do that as it makes me drool thinking ...

I am certainly no expert on this so don't blast me if I am wrong, But I recently had a similar problem with a lot of magnetic interference where I was going to lift off.  I had the idea of moving it away from the area to recalibrate and then move it back to my launch area.  When I moved it back, the area with interference, I received a compass error again.  In hindsight, it is probably a good thing that I received the error as it probably saved me from making a bad decision taking off from an area with magnetic interference.
2015-6-15
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Krafty
lvl.2

Singapore
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I think the way to go will be to take it, calibrate it onshore and then if I have a super calm day or access to a beach, no errors and feeling confident I will fly. I think buying a drone right now it is almost inevitable that I will kill it at some point in its career, the goal is that when I do I want to know I mitigated every risk I could, there is no chance it hurts anyone or anything and the shot I am going for is worth the (lowest possible) risk in a given situation.

Will let you know how it pans out and thanks for all the advice.
2015-6-15
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rieckstudioaust
lvl.1

Australia
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Krafty Posted at 2015-6-16 14:31
I think the way to go will be to take it, calibrate it onshore and then if I have a super calm day o ...

I have the same predicament. My previous PV2+ drone didnt have this problem. Switched to atti mode and I could take off anywhere. No compass error to prevent a lift off. Providing youre comfortable flying in atti mode and you stay well within your flight parameters. However- my P3 wont even lift off in Atti mode because it needs the compass calibrated. Has anyone been able to calibrate close by and then move back to the magnetic zone and take off successfully ??
2015-6-22
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Michael Starley
Second Officer

United States
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Krafty -Now that is living up to that user name . As log as you don't travel over 200 miles or so after calibration you will be fine.
As far as launching goes, launch from the boat.

Launch from your hand and catch in your hand .You can do it. I have faith in you .A lanyard  to hold the remote helps.
Do not worry about the Return To Home Point that is set for a failsafe. If Failsafe is triggered the P3p is maneuverable.You can fly it back to you as long as you are reasonably close to it.Within 100 yards or so.
If you trust the driver of the boat it can be done . It is a tightrope walk however ,small margin for error.

Focus completely on what you and the bird are doing. Very easy to get distracted by well built women and curious onlookers.
Ignore them until the bird is back in your hands.Then crack open a good dark beer and check out the video .Whatever you decide best wishes.  
2015-6-22
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Michael Starley
Second Officer

United States
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Hey  Willy Wonka
Ever heard of Beach Camera?  I see the Jersey State Seal.
2015-6-22
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