Compass Calibration Guide

Discussion in 'Mavic Pro Discussions' started by msinger, Oct 12, 2016.

  1. msinger

    msinger Well-Known Member
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    Why Calibrate?
    Compass calibration is important to safe, controlled flight. It compensates for changing background magnetic "noise", a.k.a. magnetic inclination and deviation. Inclination and deviation that isn't corrected through compass calibration will cause inconsistencies between GPS and compass that can result in "toilet bowl effect", a swirling motion that can cause the Mavic to fly out of control.

    What is Magnetic Inclination and Deviation?
    Magnetic deviation is a horizontal variation that comes from the Mavic itself and the equipment you have installed on it as well as the magnetic makeup of the area you are flying in (again not to be confused with declination). Sometimes the deviation will be insignificant, but other times it can be big enough to cause you to lose control. Inclination is a vertical magnetic variation that shifts depending on where you are.

    Warning Signs
    The Mavic can only detect when the compass is providing extremely poor (implausible) data. This typically occurs if you place it near a strong magnetic field or do not calibrate it properly. It will flash red and yellow lights and the Mavic will indicate a compass error in the app.

    IMPORTANT: The lack of a compass error does NOT mean your compass is working and calibrated properly.

    Compass Interference
    You can view the current compass interference in the "Main Controller Settings" --> "Advanced Settings" --> "Sensors" section of DJI GO. The colored bars should be in the green (Excellent) range when the Mavic is in a location that is away from magnetic influences. If the bars are in the red (Poor) range or close to it, move the Mavic to a different location and check again. If the compass interference is still in the red (Poor) range or close to it, the compass could need calibrated or it could be magnetized/damaged.

    IMPORTANT: A good compass interference value does NOT mean your compass is working and calibrated properly. For example, if you calibrate next to some rebar, the compass interference might report good values may still be OK until you fly away from the rebar.

    What Does Calibration Actually Do?
    Calibration measures the magnetic fingerprint of the surrounding area. By turning the compass 360 degrees, the Mavic can see where the compass reading doesn't smoothly increase or decrease. It uses this information to build an adaption table so that when the Mavic turns during flight, the reading is smooth and linear.

    When Should I Calibrate?
    You do not need to calibrate before every flight and in some cases you definitely should not calibrate. That doesn't mean you shouldn't ever bother doing it. It only takes one time for it to go very wrong. The most important aspect of compass calibration is making sure the magnetic "neighborhood" around your Mavic is consistent between calibration and during flight.

    IMPORTANT: The ideal place to calibrate is an open field with nothing metallic in a 20 ft radius. Keep away from drainage pipes, irrigation systems, rocks, etc.
    • DO Calibrate
      • Compass interference values are out of whack or compass error is reported (check area first).
      • Circling in flight (also check for other possible causes).
      • New equipment added or removed / new firmware installed.
      • Location change (greater than ~100 miles).
      • Significant change in terrain (e.g. to / from mountains).
      • If you just degaussed your compass (BTW, don't degauss unless instructed).
    • DO NOT Calibrate
      • If near concrete, buildings, and hidden or overhead power lines / pipes / etc.
      • If you're indoors, on a paved surface, on a stone surface, on the beach, on a boat, on a balcony, near a car, near speakers, etc.
      • If there are metallic (ferrous) objects nearby or you're not sure
    • Pre-Calibration Checklist
      • Everything used in flight should be powered during calibration, e.g. GoPro, tracker, etc.
      • Remove all metal from within 10 ft radius, e.g. watch, phone, ring, belt, coins, controller.
      • Calibrate on grass or dirt and not on concrete, asphalt.
      • Calibrate on a level surface if possible.
      • A cardboard box is a good idea to get it off the ground and level.
    • How to Calibrate
      • Power up your Mavic and accessories as normal.
      • Wait until your Mavic is ready to fly.
      • Select CALIBRATE under AIRCRAFT STATUS | COMPASS. Click OK.
      • Confirm solid yellow rear lights.
      • Pick up the Mavic and turn it smoothly and steadily a full 360 degrees until the lights turn solid green.
      • Point the front of the Mavic straight down and repeat until the lights turn off and resume normal flashing.
        Note: Don't be concerned if your gimbal reacts poorly to being face down, keep turning as normal.
    If for any reason you do not complete any of the above steps smoothly and evenly, restart the process.

    ─────────────────────────────────────────────────────────
    Note: A lot of this information was copied over from ianwood's thread in the Phantom Pilots forum.
     
    #1 msinger, Oct 12, 2016
    Last edited: Nov 18, 2016
  2. smartin53

    smartin53 Member

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    I'll stress something from using a Phantom 3 in the arctic. North is not magnetic north above the arctic circle. Calibrate your compass every time you use it. A coworker crashed his Phantom 2 prior to my arrival because of his compass calibration (it flew...and then nosedived). Mine was a bit better but wandered A LOT if I didn't do a preflight cal every time even with GPS lock. After the cal though...no issues. GPS connection is oddly flaky above the arctic circle for some reason even though it's supposed to be global. I would lose GPS nav quite a bit. I am assuming that the Mavic Pro will do better but best be safe.
     
  3. Victor

    Victor Member

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    For GPS satellites the (orbital) inclination angle is 55º and for Galileo the planned inclination angle is 56º. This means in practice that no satellites signals are received in the zenith direction north of the corresponding latitudes (i.e. north of 55º and 56º N). If the GNSS receiver is located further north, the elevation angles of the satellites is reduced as the latitude increases.

    Source : Coordinates : A resource on positioning, navigation and beyond » Blog Archive » Challenges for Positioning and Navigation in the Arctic
     
  4. smartin53

    smartin53 Member

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    Ah duh you are correct. For some reason I forgot that little tidbit. I did get signals, but at 76º N the angle was terrible.
     
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  5. kmaluo

    kmaluo Well-Known Member

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    So I live on Oahu, Hawaii, and it sounds like I calibrate once in a large open field, and I don't have to do it again unless prompted or flying in the mountains? The radius of the island is approximately 20 miles.
     
  6. msinger

    msinger Well-Known Member
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    Right -- you shouldn't have to calibrate on every flight if you're only flying within that 20 mile area.
     
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  7. piccoloflyerr

    piccoloflyerr Member

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  8. devinrhall

    devinrhall Well-Known Member

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    thanks for this...i've only had racers before this...thanks for the lessons even though i've done so much research i've seen something like this...awesome work getting it here though because compass calibration is important...im new to compass calibration so thanks...i take whatever i can get


    Sent from my iPhone using MavicPilots
     
  9. Mattman

    Mattman Well-Known Member

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    So... You mention some empirical measurements that don't necessarily imply a good calibration (and can't be trusted to imply a good calibration like mod value and compass error). Are there any that actually DO indicate a good calibration or do you just have to calibrate as best you can and hope?
     
  10. msinger

    msinger Well-Known Member
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    After you complete the calibration process, the Mavic and DJI GO will alert you if the calibration failed.
     
  11. Rom3oDelta7

    Rom3oDelta7 Active Member

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    Thanks. Questions:

    1. Does the center of rotation matter? Recently I've see a lot of videos where the user rotates the drone in a circle around their bodies vs using the drone as the center axis of rotation. The DJI wikis and FAQs say to rotate the drone only. I have always done this by holding it off to my side and rotating my body in a wide circle keeping the drone in the center. (Otherwise, it was a two-handed operation and it wasn't very smooth.)
    2. I've used the DJI Assistant in the past to look at the Mod data for the compass. Is 1400-1600 still a good nominal range for the Mavic?
     
  12. msinger

    msinger Well-Known Member
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    It does not matter if you rotate the Mavic in your hands or hold the Mavic still and turn your body. I personally turn my body since it eliminates the risk of accidentally dropping the Mavic.

    The DJI GO app now displays colored bars to show the amount of compass interference. I updated that section above since the mod values no longer apply in the more recent versions of DJI GO.
     
  13. Rom3oDelta7

    Rom3oDelta7 Active Member

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    Thanks! Where are the bars displayed, btw?


    Sent from my iPhone using MavicPilots
     
  14. msinger

    msinger Well-Known Member
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    You can find them in the "Main Controller Settings" --> "Advanced Settings" --> "Sensors" section of DJI GO. You will only see them if your Mavic is connected to DJI GO.
     
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  15. Butterpuff 6

    Butterpuff 6 Well-Known Member

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    The Mavic manual says "Only calibrate the compass when the DJI GO app or the status indicator prompt you to do so." Do you think this indicates that Mavic's software has been designed to eliminate the need for manually checking compass interference values?
     
  16. msinger

    msinger Well-Known Member
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    No. It only indicates that the DJI manuals are not always the best source of information.
     
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  17. Butterpuff 6

    Butterpuff 6 Well-Known Member

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    Thanks msinger, this was very good an thorough information. I guess the people who always respond with "read the $@&#% manual!" whenever someone asks a question, might not be giving the best advice :)
     
  18. msinger

    msinger Well-Known Member
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    The manual isn't all bad though. It's chock-full of a lot of great advice.
     
  19. Crusader

    Crusader Well-Known Member

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    Down the rabbit hole!
    @msinger, thank you for yet another helpfull thread on this forum.
     
  20. The Editor

    The Editor Well-Known Member

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    I wouldn't hold your breath on Galileo - they will not make their planned 30 orbital by 2020, they are already years late and billions over budget.
    Oh , and so far, not enough satellites have been ordered to even reach the proposed 30.:rolleyes: That doesn't include the three that are already faulty (and probably will need replacing)
    We will all be flying Mavic 20's by the time the constellation is of any use - that is, if the EU don't scrap it and leave it up there as Space junk. :p

    Sorry - a bit off topic. :(
     
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