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Spooky Action at a Distance
1466 16 2016-11-26
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Sky Captain
lvl.3
Flight distance : 200075 ft
United States
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Hi All,

Well, I had my first problem with the mavic a few days ago. I've made about 30 flights so far without incident, it's a fantastic machine. I was flying around a lake far from power lines and using tap-fly as sort on an autopilot so I could concentrate on camera settings. I began getting yaw drift, to the point where I was almost flying sideways, as I could tell from the video feed. The rest of this story is told after reviewing the flight log many times. I then began heading back toward my home point, at which time I got the message "weak GPS signal". It had been showing 18 satellites, and still did, although the strength bars went down to 2 and turned red. The aircraft went into ATTI mode, as it should have, but began flying backwards and drifting sideways while maintaining an altitude of 150 feet. I made sure tap-fly mode was off. When I saw that the mavic was pointed in my general direction I pushed the right stick forward 100 % and got it back above me. I let go of both sticks and it began "toilet bowling", moving in circles above me without any input. I saw that the satellite strength bars were increasing and soon I had control back and was able to land.

I know that the yaw drift was probably from a bad compass calibration. I had just calibrated it at the park and there were frisbee golf goals not too far away, they may have caused a problem so my bad on that. However, after reading countless posts about the sudden loss of gps, and my own experience, I think the mavic does have a flaw. I think the gps unit is faulty and prone to sudden gps loss. I can understand going from 18 satellites to 10, but going from 18 to 0 in an instant in open country has got to be the gps unit. I welcome DJI to examine my flightlog, please let me know how to get it to you. Hopefully the gps can be fixed with a firmware update. If not, I should probably start a service ticket.
2016-11-26
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Sky Captain
lvl.3
Flight distance : 200075 ft
United States
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Ok, maybe it was all my fault. I got this reply on another forum by Kilrah:
Sky Captain said: ↑
I know that the yaw drift was probably from a bad compass calibration.

Then you got it.

Sky Captain said: ↑
I can understand going from 18 satellites to 10, but going from 18 to 0 in an instant in open country has got to be the gps unit

No, it's the compass. The FC can't do anything more than what you experienced without compass regardless of how good GPS reception is. When compass data is invalid it kind of invalidates the GPS data, which you see in the app by the bar going red. There are 18 satellites, but they're of no use for GPS-based navigation if the compass is not working.
#3Kilrah, Today at 4:16 PM

So, I will certainly be more careful with my compass calibrations from now on.
2016-11-26
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HWKIDD
lvl.4
Flight distance : 22877 ft
United States
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Sky Captain Posted at 2016-11-26 14:54
Ok, maybe it was all my fault. I got this reply on another forum by Kilrah:
Sky Captain said: ↑
I k ...

did you go in the app and look at the compass  settings,  green yellow or red,  there are two compass on this unit, and when one fails the other is to take over,   I have seen post,  where you  look at the compass settings, one will pass and the other did not,   I was on my third flight  two days ago at my son's house,  out in the middle of know where,   I did not re calc  the compass  as  it said normal,  and  I have read so much, where one persons says you should and another says you should not,  I really do not know anymore, what is correct,  but  I dropped down to 1 red bar  with 12 being tracked,  but  then it went back to green in  a few seconds,  Now I was also flying in beginner mode,  as I have not had a drone, since the Vision,  and on that drone you  did the  compass dance  before every new location flight,   will follow your post,  to look for updates,   Mine Mavic is one of the first run,  was  ordered on the first day, and shipped in the first release,  but  I did not fly it until after the update,   so  sure hope its not a issue with early production,  
2016-11-26
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DJI-Ken
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Flight distance : 1515312 ft
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Correct as what Kilrah stated, the flight controller relies on the GPS and compass, it's imperative that the compass be calibrated with no metal around.
Also, no metal on your person like a watch, phone, jewelry, and set the RC/phone on the ground several feet away from you during compass calibration.
2016-11-26
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DJI-Ken
DJI team
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HWKIDD Posted at 2016-11-26 19:07
did you go in the app and look at the compass  settings,  green yellow or red,  there are two comp ...

That's great you are offering assistance, you've studied quite a bit and I'm glad that you can contribute to help assist others.
Thanks for doing so, I really appreciate it.
And not to worry, your Mavic is in great shape and if there is something that comes up, that's what the warranty is for.
2016-11-26
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HWKIDD
lvl.4
Flight distance : 22877 ft
United States
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DJI-Ken Posted at 2016-11-26 17:19
That's great you are offering assistance, you've studied quite a bit and I'm glad that you can con ...

thanks Ken,   a hobby is made of a lot of people helping on another, not  trying to be the forum bully,    I learn so much by reading other folks issues,  and  then  look for those things on my own unit,   I am not worried,  about  mine,  things happen,  but  operator error is something I am in control of, and  I hate it when its, that,,,  love to be apart of the group,  
2016-11-26
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HWKIDD
lvl.4
Flight distance : 22877 ft
United States
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DJI-Ken Posted at 2016-11-26 17:16
Correct as what Kilrah stated, the flight controller relies on the GPS and compass, it's imperative  ...

ken,  does gold affect the compass?
2016-11-26
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Sky Captain
lvl.3
Flight distance : 200075 ft
United States
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Thanks all for your input, I now have a much better understanding of how this bird works
2016-11-26
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DJI-Ken
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HWKIDD Posted at 2016-11-26 19:25
thanks Ken,   a hobby is made of a lot of people helping on another, not  trying to be the forum b ...

Sounds good.
2016-11-26
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DJI-Ken
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HWKIDD Posted at 2016-11-26 19:30
ken,  does gold affect the compass?

Pure gold I wouldn't think so but I make sure I have NO metal of  ANY kind around when I calibrate, I just like to be safe.
2016-11-26
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trance728-
First Officer
Flight distance : 179738 ft
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United Kingdom
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DJI-Ken Posted at 2016-11-26 21:32
Pure gold I wouldn't think so but I make sure I have NO metal of  ANY kind around when I calibrate ...

Is this metal thing new or did I just miss something when I had my last drone, the Phantom 2? I never had any issues with it and I'm sure there was metal around when I would calibrate it.
2016-11-26
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DJI-Ken
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trance728- Posted at 2016-11-26 20:37
Is this metal thing new or did I just miss something when I had my last drone, the Phantom 2? I ne ...

I've always calibrated the compass in a magnetic interference free area and have no metal on me.
Screen Shot 2016-11-26 at 8.01.48 PM.png
2016-11-26
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MacIak
lvl.4
Flight distance : 3419 ft
Belgium
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Ken, this is a consumer product. No NASA tool, try to stay realistic please. Electromagnetism is everywhere and it interferes with everything else, not necessarily making things fail. In the environment im in I am sure I cannot find any location which is "magnetic interference free" as you state.  The manual extract you are showing, funny, reminds me of the Bible.. and preachers (You?) using small parts of it out of their context to manipulate the mass or justify crap (im Christian by the way, not offending here). If this manual is trying to tell us we cannot wear a ring, keys in pocket, necklace, neighbours WiFi... come on. Why doesn't DJi tell us to summon Magneto every time a compass needs calibration so he'll extract the Fe out of the operator's blood, just to make sure. The manual is talking STRONG interference, ferromagnetic such as CELLULAR PHONES (WHAT? next point says the GO app wil prompt you....). It almost sounds like launching a smartphone and telling people not to apply pressure on the screen cause it might break.
2016-11-27
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Shill Slayer
lvl.2

United States
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MacIak Posted at 2016-11-27 13:46
Ken, this is a consumer product. No NASA tool, try to stay realistic please. Electromagnetism is eve ...

Hail Magneto!  
2016-11-27
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nils.heidorn
lvl.4
Flight distance : 183533 ft
Germany
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DJI-Ken Posted at 2016-11-27 02:16
Correct as what Kilrah stated, the flight controller relies on the GPS and compass, it's imperative  ...

The toilet bowl & yawing can only happen if GPS & Kompass DISAGREE about heading.
But (whyever) the GPS was out of the Equation, the Mavic was in ATTI mode if i got it right.
So it cant be a compass offset or the Mavic was "lying" about beeing in ATTI.
And: having some metal meters away does not mess up compass calibration no matter what some manual says. I have been calibrating conpasses for 6 years now and unlike DJI APM & Pixhawk show the actual computed offset values and metal (NON magnetic) in a distance > 2m does not play a role.

So something is wrong here, and i am NOT talking about the sudden GPS loss which is the most mysterious thing off all that happened...

Greetings,

Nils
2016-11-27
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DJI-Ken
DJI team
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nils.heidorn Posted at 2016-11-27 13:17
The toilet bowl & yawing can only happen if GPS & Kompass DISAGREE about heading.
But (whyever) the ...

If GPS is working, there still can still be toilet bowl if the compass is not calibrate correctly.
2016-11-27
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QuanthonyTrang
First Officer
Flight distance : 419980 ft
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Australia
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Open grassy field. Take pants off (belt, phone, watch). Open arms and use the sports mode button and flick it 5x fast and then do the dance. I find it best to do with mavic above my head, high as possible. I then spin 360, then drop the nose down and spin another 360.  
2016-11-27
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