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Question on taking off from Building Roof and Magnetic Interference
1512 6 2016-12-4
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MavicUser
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Flight distance : 431417 ft
United States
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I just did a flight today, taking off from the roof of a high rise building... I placed the Mavic on the floor of the building and turned it on, I get magnetic interference and the GPS will not lock, and the controller asks me to check the app.  Looking at the app, it asks me to calibrate the compass... Luckily, since I know that this is not the proper environment to calibrate, I DID NOT do a compass calibration.  During my last flight from a beach, I checked my compass and IMU calibration, it was all green, so I knew my Mavic didn't have any calibration issues.. I assume the magnetic interference is due to all the metal on the roof of the building.

I then turned off the Mavic, put it on the ledge of the wall running around the building, about 4 feet from the floor, carefully holding on the Mavic, turned it on... After IMU initialised, it gave me a green GPS lock with ready to take off... I then put the Mavic back on the floor of the building and immediately get a magnetic interference signal again, but this time, I still had GPS lock, and still ready to take off.

I did take off, and the Mavic had a perfect flight... No issues at all...   However, once landed, the magnetic interference message happens again.

My questions regarding such a flight are these:
1.  How safe is it to do what I did?  e.g. Initialise the IMU away from metal, but take off with magnetic interference?  Should I have launched by hand instead?
2.  Will the metal in such an environment screw around with the compass calibration even if you DO NOT calibrate it?
3.  What is the proper procedure to startup a DJI aircraft in such an environment?

@DJI-Ken/Mindy/Natalie - What is the official DJI advice on this?
2016-12-4
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dotfiles
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I think you did the right thing here, if you had calibrated the compass you would have had issues once you took off and got away from the source of the interference. This is a reason why you do not want to calibrate the compass on every single flight.
2016-12-4
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yoengel
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Flight distance : 2370988 ft
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I was also having issues with magnetic interference in an urban environment and the app kept asking to calibrate.  What's the best thing to do in these environments?  Keep the mavic close by?
2016-12-11
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MavicUser
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Flight distance : 431417 ft
Canada
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yoengel Posted at 2016-12-11 13:59
I was also having issues with magnetic interference in an urban environment and the app kept asking to calibrate.  What's the best thing to do in these environments?  Keep the mavic close by?

Whatever you do, DO NOT CALIBRATE in such an environment...  What I've decided to do if I really have to fly in such an environment, is to make sure my aircraft is already calibrated well in a previous near location, test fly it in that environment to make sure everything is functioning perfectly.  

In the noisy environment, I would bring along a non-metallic surface (e.g. table) that can lift the aircraft 3 or more feet away from the floor surface and as well as keep away from all walls.  The Mavic should be able to turn on and initialise IMU with minimal interference on such a surface.  Take off and land back on the non-metallic surface...  If a table is not available, it would probably be possible to turn on the Mavic in your hand, then hand launch and catch... This would not be ideal though..
2016-12-11
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Free Bird
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Canada
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Your problem might not be the environment. Others including myself are having issues. Check out these threads.

http://forum.dji.com/thread-75833-1-1.html
http://forum.dji.com/thread-75541-1-1.html
2016-12-11
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MavicUser
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Free Bird Posted at 2016-12-11 18:25
Your problem might not be the environment. Others including myself are having issues. Check out these threads.

http://forum.dji.com/thread-75833-1-1.html

Thanks for the links, but I'm already well aware of the issue of high current as I've posted links to this issue myself... The bug in the Mavic causes compass 1 to diverge from compass 2, causing TBE in a high current situation... The new firmware 1.03 changes to using compass 2 in these situations and posts a calibration warning, but this switch prevents TBE and loss of GPS...  This is not happening to all Mavics, only some, but it is good to see DJI changing the firmware to resolve this issue.  From another post over at Mavicpilots.com, a german user has reported that DJI informed him this issue is caused by a cable in the Mavic and to send his Mavic in for service (Link)... If anyone is encountering this issue, they should contact DJI and send their Mavic back for service.

I've never had to calibrate my Mavic since I'm in Hong Kong and only around 30km away from the DJI factory...

I'm very sure the problems in my original post IS caused by the environment I was flying in since I didn't encountered this issue, once the Mavic was moved 3-4 feet away from the floor/walls...   I've also never encountered this error before that flight or since that flight...


2016-12-11
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Free Bird
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reported that DJI informed him this issue is caused by a cable in the Mavic and to send his Mavic in for service.

I sure hope that is not my problem. Tomorrow I plan to go out into the center of a large field and fly my maiden flight, this will tell me more if there is a problem. I haven't been able to fly my new Mavic yet near my house which is a single dwelling house out in the forested suburbs. This bothers me because there should be no reason that there is magnetic interference outside my house.
2016-12-11
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