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Constant compass error warning?

Discussion in 'Pro/Adv Discussion' started by Ollie613, Jul 31, 2016.

  1. Ollie613

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    Hello, I have currently done 4 flights on my P3A, all of which have at some point had a compass error. I ensure I calibrate the compass before each flight (Away from any metal objects), however during every flight I have received a compass error message. Sometimes if I slightly move the phantom closer to its home point it says safe to fly again, others it doesn't stop so I have to land in ATTI mode. I have even checked if there are any solar flares that could affect the compass. Does anyone else have this issue or is it a common occurance? If so is there an easy fix that doesn't require it to be sent back to dji? Thank you in advance for any replies!
     
  2. kinsey

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    Have you just updated the firmware ? what is the firmware you have in ?
     
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  3. Numone

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    Try calibrating it in another area.
     
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  4. jephoto

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    Also once you have a good calibration no need to do it every time. You could be calibrating it BAD in a new area and throwing the compass completely off.

    Once calibrated after starting up give it time to find its home point while you check your other settings. Most of the time it will lock o not your current location all by itself.
    Only if you are in an area with lots of interference, or lots of metal in the ground (rebar in cement for example) will you get the red compass error and Mosley just need to move a bit to a better spot. Sometimes as little as 15-20' can make the difference.

    Once I learned this I rarely need to do the compass dance unless I've gone to a completely different geographic region. 100 mi.+. Eve then maybe not.
    Or after any firmware update. Do an IMU and compass calibrate then as well.
     
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  5. ray rokni

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    Stop calibrating at each flight.
    Calibrated mine twice in one year, after calibration I double check it with an actual compass.
    Compass very sensitive, few inches makes a difference, e.g. I put it on my picnic table where it has a metal brace and I get compass error, I move it 6 inches and it's fine!!


    Sent from my iPhone using PhantomPilots mobile app
     
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  6. Ollie613

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    Ah, ok that makes sense thank you for all the replies! I have downloaded the newest firmware which was why I thought it was a bit odd. I also didn't realise the compass didn't need calibrating every flight as with my P1 it was required as I think that set it as the home point.
     
  7. ray rokni

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    There are two schools of thought, one that calibrate before each flight and the one that doesn't.
    Here it's how I have done mine, twice in one year. I may also add that I have traveled over a thousand miles from original calibration location and flew without recalibrating.

    I have a plastic box that I use to carry stuff around, I have drawn an arrow on it, using a compass I align the arrow to North. After I calibrated my p3p, I position it on the arrow and look on the dji go app to see if correspond s accordingly.
    I also do this if I go somewhere new.

    And my p3 calibration process is a bit exaggerated, I go in middle of a field away from the car, the rc, phone, no belt buckles, rings, watches, etc. If I wouldn't get arrested I would probably go naked!




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  8. jephoto

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    In June I flew to Los Angeles from Chicago, set up the drone the next day to fly. Found the home point within a minute with no further calibration.
     
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  9. Ollie613

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    So is it possible to see which way the compass 'thinks' is north on the dji go app??
     
  10. ray rokni

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    Of course.
    I put the p3 on the arrow on the box pointing to North, I then bring up the map and see if the actual and the map correspond.


    Sent from my iPhone using PhantomPilots mobile app
     
  11. Ollie613

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    Ah yes of course the map links to the compass! Thanks
     
  12. WetDog

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    You're doing it wrong.... The term 'compass' is a bit misleading as the magnetic field indicator system in the Phantoms works in 3 dimensions**. While your system would probably find a major discrepancy - likely from local field effects like buried rebar or the like - it is both too complex and not sensitive enough. Just check the MOD value for the compass in ADVANCED | SENSORS. Should be between 1400 and 1500.

    ** Yes, we all know that traditional magnetic compasses will reveal a field in three directions. Point a compass near a magnet and watch the needle drop off of horizontal. Go near the arctic circle and turn a regular magnetic compass on it's side and watch the needle dip downward. It;s just that for most people who neither live on Pandora or the near the arctic circle, the plane of magnetic field is pretty much parallel to the ground. But the Phantom has to fly in 3D so it needs to understand all three axes.
     
  13. ray rokni

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    Off course i check the mod values. If you noticed I said I go in middle of a field where I know there are no magnetic interference and I even get naked to do the calibration!!!
    As far as doing it wrong:
    So you basically saying a normal compass it's not reliable and that the position on the app map is not either.
    Either way, I do things in real experiments and not just in theory and it has worked for me for one year with the p3, over 1000 miles flight and in mountainous areas, the beach, suburbs etc.




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    #13 ray rokni, Jul 31, 2016
    Last edited: Jul 31, 2016
  14. WetDog

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    No, the mood values are what you check on with your partner before you take off go flying. Important, to be sure, but not the same thing.:)
     
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  15. Numone

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    I think you're not totally correct; in my experience, the mood value has a DIRECT correlation to a good or bad days flights..!;)
     
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  16. Northern Observer

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    Sounds like my unit currently on its way to DJI.
     
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  17. WetDog

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    No, I am saying that using a magnetic compass to check on the Phantom's compass is unnecessary. Won't hurt but if you really want to check accuracy you're going to have to know the current magnetic declination for every place you fly. Which is much more work than looking up the mod value which is calculated from some hairy math and really should be a good indicator of how well the compass is seeing the fields.

    And please, leave your clothes on. This hobby has enough bad publicity as it is.....

    EDIT: This is a nice overview of an IC magnetic compass. Don't know exactly what make and model DJI uses, but I am going to bet it functions similarly.
     
    #17 WetDog, Jul 31, 2016
    Last edited: Jul 31, 2016
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  18. Chris0137

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    I'm sure I've read you should calibrate your compass ANYTIME you go to a new location 200+ times. Now after reading this I don't know if I should skip the procedure or just do the naked MOON WALK across the field and pass the hat or continue to calibrate.
     
  19. ray rokni

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    As I said, two schools of thought
    One that calibrates constantly
    One that doesn't, unless mod values are off

    You should do what you feel is right, I've studied and read a lot regarding this and done actual tests and it leads me to believe that constant calibrating is not for me


    Sent from my iPhone using PhantomPilots mobile app
     
  20. WetDog

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    It would be nice if DJI engineering would pop in an tell us stuff. The best we have is people like Ianwood and Blade Strike who seem to be one removed from the internals at DJI but a hell of a lot closer than the rest of us. If you haven't, read Ianwood's magnum opus on compass calibrations.
     
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