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compass - can it go out of calibration in flight ?

Discussion in 'Pro/Adv Discussion' started by Bob Hyslop, May 26, 2016.

  1. Bob Hyslop

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    Hi all,

    Bit of a silly question I guess but I need to find out (before I make a massive dent in something expensive).

    Once the compass has been successfully calibrated before flight could it go out of calibration during a flight if you got too close to something with loads of steel such as a ship or large steel reinforced concrete structure.

    Also if taking off from a concrete structure which contains a lot of steel I would guess the compass would not be calibrated. Would it sort itself out once airborne and away from the structure?

    Any help appreciated.
     
  2. Mimoid

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    The compass in the Phantom can be affected by metal objects in the proximity. If you would calibrate the drone in such an area where the Earth's magnetic field is disturbed by nearby ferrous objects, you will encounter serious issues once you fly away from the disturbance.

    If you on the other hand have a perfectly calibrated compass, you should try to keep the calibration values, as they are perfectly valid for all flights within your generic area (within a 100 km range). If you during flight encounter a severe magnetic anomaly, the Phantom will warn you about that, and suggest that you switch to Atti mode.

    Normally, this should not occur unless you are pretty much flying on top of a huge electromagnet. I have flown (reasonably) close to ships with metal hulls, electric pylons and even trains in motion, and the compass never got the least bit disturbed.

    On the other hand, I have also performed bad compass calibrations, and had both Compass Error messages and malfunctioning GPS functions as result.

    If you have a perfectly calibrated compass but the Phantom warns you about compass disturbances upon start from the same generic geographic area, I would recommend that you do not recalibrate, but instead find a different spot to take off from. Sometimes it is enough to just move 10-20 meters.

    //Tom
     
    #2 Mimoid, May 26, 2016
    Last edited: May 26, 2016
  3. sar104

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    The calibration primarily maps local magnetic variations (deviation), mostly due to the equipment on the aircraft. The aircraft flight may be affected if it approaches an area where different magnetic variations exists, such as around large steel or iron structures, but it will not change the calibration. Calibrating in such an area will result in a flawed calibration table.

    Only magnetic fields large enough to change the magnetization of the aircraft itself will put it out of calibration. Changing location on the earth's surface should be accounted for by a stored map of declination and inclination, but I don't know how comprehensive and detailed that is in the Phantom firmware; possibly a lack of detail is the reason for the recommendation to recalibrate when significantly changing location.
     
  4. Oso

    Oso

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  5. Bob Hyslop

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    Cheers Guys, had a bit of a flappy moment whilst filming an old paddle steamer and had to abort flight as not sure what happened.
    Tried again this morning and had the same happen again so wondered if anything to do with compass.
    Compass calibration showed just over the 14 mark and had no warnings just gets to a point by the steamer and starts to drift over it towards some very expensive looking yachts.
     
  6. Bob Hyslop

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    yeah already seen that Oso but calibration at start of flight was good just had problem at certain part of flight in approx
    same area on 2 difference occasions, sudden drift in same direction at same point by steamer.
     
  7. Oso

    Oso

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    Then you've probably also seen the video which demonstrates many of the items noted in the earlier post and also your question about compass calibration around a concrete structure which contains a lot of steel.

    An example of bad compass calibration