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Compass Calibration, A Complete Primer

Discussion in 'General Discussion' started by ianwood, Jan 8, 2015.

  1. George Weaver

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    ian,

    Thanks for the post, especially on when and when not to calibrate. I'm of the old-school "if it ain't broke" philosophy, but still need to watch our for cumulative errors.
     
  2. LOONEYHD

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    I am a new P3P user and very much appreciate your post. Thank you!


    Sent from my iPhone using PhantomPilots mobile app
     
  3. HawkeyeImaging

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    I have had my P3 Pro for about 9 months now. I usually calibrate the compass every time I fly in a different area. Do I not need to do this???
     
  4. msinger

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    No. Check out the first post in this thread for more details.
     
  5. HawkeyeImaging

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    I did, That's why I was asking. Great info. The last calibration I did was in an asphalt parking lot at an Industrial Warehouse and it went flawless. I think I'm gonna just hit the field across the street now and do another calibration and leave it at that.
     
  6. msinger

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    So, you're wondering if the info in the first post is accurate/trustworthy? If so, it's great advice that everyone should be following.
     
  7. HawkeyeImaging

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    Not at all. Just confirming that it does not need to be done every time!
    I have seen other posts on other forums (including this one) that said it should be done everytime you fly in a different location!
     
  8. msinger

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    Right. And, the DJI manual says to calibrate before every flight.
     
    HawkeyeImaging likes this.
  9. HawkeyeImaging

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    That's what I have always done. Sometimes it's a hassle..especially on a construction site to find a good place to calibrate. Makes me feel a lot better knowing now that I don't have to do this every time!
     
  10. HawkeyeImaging

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    Now I just have to figure out flying inside these big warehouses when they are completed!
     
  11. Mokkas

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    thank you
     
  12. Cornscot21

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    Much appreciated; finally a concise and definitive post on this. Although I do think there might be an issue with P3A firmware recently as have had apparent compass issues every flight. New P3A to now fly and will start off by following this advice.
     
  13. Alex Baxter

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    I was recently in the Pyrenees, lots of rust coloured boulders, they even mined for iron there in the past. I picked my compass calibration location very carefully indeed... Likewise, would magnetite in a sandy beach discolour the sand in a similar manner?
     
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  14. Reed L

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    Nope, because the sand is being constantly turned over so the oxidation over time that turns it red is not present. 1 minute into the video it goes into oxidation and shows the difference between the oxidized red and the still black or washed black sands. As long as the black sand stays out of the water it will rust and turn red :)

     
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  15. David_Cambridge

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    I have a marine/aviation background, and would never be without a well calibrated compass. It is a great backup for the other far more complex systems. My boat compass requires a 360 degree rotation to calibrate, and in addition to finding magnetic north at that position, it calibrates out the changes on the other points of the compass. The dead simple marine compasses require a mechanical process - rotating left right and front back shafts to compensate for the compass point non-linearities. It is not a problem with a poorly made compass, but the net effect of the location, the boat's equipment etc.

    Logging those settings over time establishes pretty clearly that 5 degree variations occurr routinely, and calibration gets rid of most of the errors.

    Deriving heading, from the GPS as others have mentioned, works only if the Phantom is moving. This, if there is a side wind, is not the direction the ac is pointing, but rather the direction of travel, which is the vector combination of the heading and the wind offset. A further complication is the intrinsic error in the GPS position,which Can be up to 16 feet, and still be in spec.

    DJI has created a very sophisticated and interdependent system, which uses gyros, gps, and compass, all working independently, and integrates these readings into a combination that works extremely well. Nobody has any control of the factors that impact the individual sensor systems errors. The systems job is to use all of the independent sensor data to arrive at a best guess of the truth.

    Pilots and captains do this in their heads, based on their training and experience.


    Sent from my iPad using PhantomPilots
     
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  16. Alex Baxter

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    Just a thought, if you dug up wet sand above the high tide level, and it was not stained brown then there is no iron in it? It would be exposed to salt water and oxygen, but not disturbed, so ideal conditions for oxidation. Come to think of it, any wet sand that's undisturbed and not discoloured must not contain iron?
     
  17. Ken Nash

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    Excellent post.
     
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  18. Martin on Guam

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    Having issues with my new out of the box Mavic. IMU calibrates fine. Compass will calibrate horizontally but not vertically nose down. Always magnetic interference. Have tried several times, restarted everything several times as well. Quite frustrating.
     
  19. msinger

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    Are you calibrating it outside? Are there any metal objects on you and/or nearby?
     
  20. Matchlock

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    So, are you saying that even when the DJI GO 4 App says "Compass Calibration Required" we shouldn't calibrate the compass?
     
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