Compass Reading on the DJI GO 4 App?

Discussion in 'Spark Discussions' started by nutsnbolts, Dec 6, 2017.

  1. nutsnbolts

    nutsnbolts Active Member

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    Whenever I fly as a PreFlight check I always verify my IMU and Compass us not wonky. IMU is usually green and the compass although green gives me a reading between 0 to 90 that fluctuates.

    Is that ok although it's green. It fluctuates up and down but never really goes yellow or red (upwards).

    I know a 0 is what we should arrive for but is there documentation somewhere that states what it should be at or what you should never fly if it's X.
     
  2. RaspPiGuy

    RaspPiGuy Active Member

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    Curious.. Does it improve after a calibration?
     
  3. msinger

    msinger Well-Known Member
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    I've never seen a value near 0. As long as the bar is green, you're good to go.
     
  4. nutsnbolts

    nutsnbolts Active Member

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    Ok thanks for the confirmation. I wasn't sure whether the color or the numerical value is what we should focus on.
     
  5. nutsnbolts

    nutsnbolts Active Member

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    You know I calibrated once for IMU for both my spark and Mavic pro when it arrived. Same with the compass. My understanding is that if you move to another location, compass calibration is what I should do. I haven't recalibrated because it has been green. I haven't gone anywhere else other than my backyard.
     
  6. msinger

    msinger Well-Known Member
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    You shouldn't have to calibrate the compass in most cases. Check out the Compass Calibration Guide for more details.
     
  7. nutsnbolts

    nutsnbolts Active Member

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    Awesome post. I guess one question I have. Does it really hurt to calibrate just to make sure as long as you do it right??
     
  8. msinger

    msinger Well-Known Member
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    No.
     
  9. nutsnbolts

    nutsnbolts Active Member

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    Ok thanks.

    I'm just not trusting that the app will inform me correctly. If it asks me to calibrate. I'm up for it. But if I travel across the world and when I launch the app and it tells me everything is normal and nothing to calibrate. I'm like uhh. Let me do it just in case. :)

    Also another clarification. After all calibration is done correctly. Can it get wonky once you're up in the air? I have read somewhere that it can still screw up. I think you mentioned it as well. I know once incident I read was it didn't go crazy till it went into fog. Which is understandable.
     
  10. msinger

    msinger Well-Known Member
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    The compass? It can if there is a magnetic metal object near the compass when you take off.
     
  11. nutsnbolts

    nutsnbolts Active Member

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    Well wouldn't I noticed that before I take off. My PreFlight checklist list out to make sure everything is green. If there is a magnetic metal object before I take off it should be red.
     
  12. msinger

    msinger Well-Known Member
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    The DJI GO app will not always warn you when there is magnetic interference near the Spark's compass.

    If you do see that warning, then you should definitely move your Spark to a different location. If you do not see that warning, then check the red aircraft symbol on the map in DJI GO to ensure it's pointing in the correct direction. Also, make sure it's not slowly rotating as your Spark is sitting on the ground.
     
  13. nutsnbolts

    nutsnbolts Active Member

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    Good Advice. !! See i can't always trust the app but multi checkpoints can help identify that things are not what it seems. :)
     
  14. Silversand

    Silversand Member

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    ...I have 2 phones and a tablet with magnetometer apps (I use these for other readings, not drone-related); wouldn't a magnetometer check (on a nice level surface near where you'll launch the drone) be beneficial? And, if beneficial, what reading would be a tolerable "field" to safely take off within?

    ....further to the above: now, the Spark's internal megnetometer. The reason why you would calibrate the quad (at a different launch site), is that depending on the patch of ground (and z space) you are launching from/up into, the calibration process would correct for different flux density/ies around your new patch of launch ground (this differing flux density would affect your yaw, pitch and roll (on edit: and cardinal orientation) as your quad crosses the different flux density x, y z at your new launch site, of course)...so, the trick is to calibrate your quad correctly (spinning it properly within its calibration timeframe)

    So, concluding, you never know if your new launch site is perched over a seam of hematite, old dump site of rusting steel under the soil, or "other"; this is why I would do a quick check with a magnetometer phone app always before launching a drone at any site I have never flown at previous...
     
    #14 Silversand, Dec 7, 2017
    Last edited: Dec 8, 2017 at 8:33 AM
  15. msinger

    msinger Well-Known Member
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    I'm not sure.

    I prefer to verify the direction of the aircraft. It's easy to check and it's a sure sign of a problem when the direction is not accurate.
     
  16. Silversand

    Silversand Member

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    OK. Fair enough.

    I'm doing more research into pre-flight portable magnetometer use at drone launch sites...If I find anything compelling, I'll def. share it here.
     
  17. nutsnbolts

    nutsnbolts Active Member

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    You think we are over complicating this :)

    I think the whole point is that we have an app that tells us the readings of what it should be at or safe to fly. The question of whether the app is accurate is that good enough? So far from what I understand the app is relatively accurate however it's best to always check the mini-map for the actual heading or any anomalies that doesn't look right after a compass reading.

    I think as far as compass calibration is concerned any new location should always be checked. It doesn't hurt , however we need to make sure that it's done correctly bearing in mind all the possible areas that will cause interference when doing the calibration.

    On the IMU standpoint that should really only be done once or when required and requested by the app on a very level surface correctly. Once again it doesn't hurt to perform an IMU check however it is an as picky as the Compass calibration which can lead to errors.
     
  18. msinger

    msinger Well-Known Member
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    It's not accurate enough. That's why it's important to always check the aircraft symbol on the map. If it was accurate enough, there would be no need to do additional checks.