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My Thoughts On The Compass Calibration Dance

Discussion in 'Phantom 2 Vision + Discussion' started by MikeTess, Jun 9, 2015.

  1. MikeTess

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    Yes, it does look silly to see someone spinning in the middle of a field, lake front, beach, etc while holding a quadcopter but here's why I do it every time regardless if I just flew there the previous day. Unfortunately, I live in an area where I can't step off my back porch and take off. If I did then I probably would not compass boogie every time. However, I need to load all my "stuff" into the hatch of my car and travel to the field of the day. I learned the hard way that putting your quad between two 4" speaker magnets tends to do funny things to the compass. I won't get into the nitty-gritty details but my experience is that the two don't mix and you should always do the hustle when you get to where ever it is that you are driving. Thirty seconds of insurance is all it takes. And btw, baba booey, baba booey howard stern. That is all.
     
  2. msinger

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    What exactly does a compass calibration have to do with magnetizing the compass? If that happens, you'll need to degauss the compass. Unfortunately, that cannot be fixed by dancing.

    Here's a good explanation on when to calibrate your compass:
    http://www.phantompilots.com/viewtopic.php?f=4&t=32829
     
  3. tcope

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    I'd tend to agree that magnets should throw a compass off only as long as the compass is exposed to the magnet. Each time the compass is set, there is an ever so slight chance something will have gone wrong.
     
  4. macsoft

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    you know you don't need to do the dance yourself. I just turn the Phantom in my hands, and I stay put. Its more of a standing still dance :)
     
  5. MikeTess

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    The Phantom can 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 will not start the motors when this happens. Unfortunately, it can only detect this in extreme conditions and you can still fly with really bad compass data if you're not careful.
     
  6. msinger

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    MikeTess, are you suggesting people can forgo the degaussing step and just do a compass calibration? Or, are you suggesting the attempt to calibrate the compass will fail and thus make it apparent that the compass needs to be degaussed?
     
  7. N017RW

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    M. Tess,

    Your last sentence is contradictory.

    Can you link to or cite your sources?
     
    #7 N017RW, Jun 9, 2015
    Last edited: Jun 9, 2015
  8. donco234

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    The Chinese just want to see if we will do it. The Phantom 4 will require you to pat your head while you turn two times left then two times right.
     
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  9. RoyVa

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    Good rule of thumb. When I doubt don't pout just dance. Better to be safe that sorry afterwards. I haven't had to dance for weeks on end. Have changed location and have subjected my quad to magnets either. But if I was doubtful I would dance the night away. To much $$$ to take chances.
     
  10. cjmwales

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    In the early exploratory flights I moved a few hundred metres to another location for launch.

    I didn't do the compass dance (thought I didn't need to bother) and after taking off, the Phantom wanted to drift backwards hard, to the point of needing fill forward pitch to bring it back. It all happened pretty quickly and was quite worrying.

    I did the compass dance and all was well again. Now I do it every time.
     
  11. RoyVa

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    The compass is certainly important but it is only one of the needed sensors.
    IMU ( Inertial Measurement Unit = Accelerometer + gyroscope + compass)
    Roll, Pitch and Yaw. Without almost any drift.
    The IMU is an electronic sensor device that measures the velocity, orentation and gravational forces of the Quadcopter.
    These measurements allow controlling electronics to calculate the required changes in the motor speeds.
    It's a combination of 3 axis accelerometer and a 3 axis gyroscope and a 3 axis magnetometer (compass) for better Yaw control.
    The accelerometer measures acceleration and also force and measured the downward gravity force. As it has 3 axis it can work out the orentation of the quad.
    The gyroscope measures angular velocity, in other words rotational speed around the 3 Axis.
    A magnetometer measures the direction and strength of the earths magnetic field. The sensor can then determine which way is north and south. The pole locations are then used as a reference with the Yaw angular velocity around the gyroscope to calculate a stable Yaw angle.
    All of the information is fed into the processor for proper control of the Quadcopter. All three main sensors data is needed. Anyone of these failure could result in disorientation. So yes the compass dance is important as is the other sensors. IMU calibration and the compass dance are the portions we control. Screw up on either and you give the processor bad data and the potential for fly a ways or crazy crashes. Hope this helps to understand the importance of both.
     
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  12. dronebandit

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    last time in the grassy field I tried to lift off from my backpack (with another 2 batteries inside it) laying on the ground.
    I was not able to calibrate compass near to it, I had to step back few meters away and do the dance, then it was fine.
     
  13. SnoozeDoggyDog

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    Bingo! I took mine of from my bacpack last night and it had batteries in it. The quad flew but it just wasnt right .... I can only describe it as stuttering as out tried to adjust for wind. It was very windy and I just put it down to that. I was concerned about it so didn't take it up more than the initial 6ft hover health check. Packed up and went home.

    No more taking of from backpack with batteries .... And zips, and USB sticks and multi tool. How could I have missed that!
     
  14. MikeTess

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    Yes, I was quoting from the link provided by PhantonHelp above....and YES, IT MAKES NO SENSE!
    That was my point. I simply maintain that I compass calibrate whenever the Phantom travels in the hatch of my car due to the large speaker magnets inches away. PhantomHelp seems fixated on debating the virtues of degaussing. Whatever.
     
  15. N017RW

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    Roger that.
     
  16. dgd3

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    Is compass calibration required between several battery swaps when taking off from the same location?
    Reason to know is that I calibrate, launch, fly out a short way, initiate an RTH test then when nearly home sit and program waypoints while hovering. I wonder if I can program waypoints while landed to conserve battery flight time since the DJI VISION iOS app does not allow saving waypoint missions.
    Comments?
     
  17. msinger

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    No.
     
  18. ARM

    ARM

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    I always have and always will do the compass every time, I don't want to see my phantom fly back to china!
     
  19. msinger

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    How exactly would not redoing a good previously saved compass calibration make your Phantom fly back to China? Is this just an unfounded fear or do you have a related experience you can share?
     
  20. ARM

    ARM

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    Nothing to share..... just overstating that I do the compass dance no matter what place or the same place I fly. back to china was a little humor you didn't get.