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Compass Issues

Discussion in 'General Discussion' started by Hughie, Dec 2, 2014.

  1. Hughie

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    I have had a P2 V2.0 (Non-Vision) for a week or so and am getting on with it OK.

    I calibrate the compass and wait for home lock/satellites before each flight.

    One recurring issue I have though is that I have never been able to calibrate the compass first go. In fact it is usually 5th or 6th go.

    The first phase when it is level, always comes back green, first time, but the end of the second phase, where I rotate with it pointing at the ground usually comes back red and green. I have to redo the whole thing another 4 or 5 times before I get greens at both stages.

    I have tried this at three or four different locations and it always seems to be the same.

    I have done an advanced calibration on the IMU and that is showing sensible values and a Mod of around 1000.

    Should it be this difficult to calibrate ? Am I missing something ?

    Thanks
     
  2. Meta4

    Meta4 Moderator
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    Why are you calibrating before each flight?
    Are you travelling a long distance between flights?
    Unless you are going 100 miles or more just get one good compass calibration and leave it.
    If you are having that much trouble, you risk getting a bad calibration when you already have a good one.
     
  3. Hughie

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    Understood, I guess the answer to the question is that I dont have much confidence in it, because it is so hard to calibrate, so I redo every time.
     
  4. IrishSights

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    Might it be the GPS saying something with the red green? As you are nose down and your hand over the GPS under the top of the shell it loses satellite lock and you get a red flash. Set it down and see if it settles. Power up and down again if you wish although not necessary. I think the compass calibration will have probably completed OK. Unless you travel big distance between sites you should not need to do it too often.
     
  5. Monte55

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    I have a customer that has a PV plus. While at his home doing service we were phantom talking. He mentioned that doing a compass cal was hit and miss for him. I told him to show me how he was doing it. In the horz part he was doing it ok but the vert part he was turning the quad like a pin wheel. I showed hem how and it was fine. We first checked values in assistant and compass was about 2200 and after proper dance we checked it again and it was down to about 1300.

    Now I hear many say to not do a compass all the time. I always do on first battery. I see no problem with doing it at same area for first flight. If there is a problem I want to know it before I fly. From the last time you did a dance someone could have placed quad next to magnet and a number of similar things. One day I did my dance a little differently than than I normally do. I held it close to my body rather than away. Calibration failed. Well, my keys were in my pocket along with a 1/4 inch magnetic chuck I always carry. I did the dance again with quad out at arms length still having keys and magnet on me and all went well.
     
  6. ianwood

    ianwood Taco Wrangler
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    Best to remove all ferrous metal from the immediate vicinity when doing a compass calibration. A bad calibration is likely worse than none. The real risk is a calibration that is bad but not bad enough for the FC to pick up on it. That can cause TBE and possibly a flyaway.
     
  7. turbodronepilot

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    Hey there hughie..I only calibrate if I move to a different location or if when I start up my phantom and the compass doesn't line up the same direction both the phantom and I are facing. .then i turn on the radar and look for the small compass in the left hand upper corner of the radar screen..it should be pointing north.. I know if both compasses are pointing the right direction it's all good..one thing I do too is mark down which way is north ..it can take me several times to get my compass to calibrate ..also dronecamps has a good video about flyaways. .check it out on their website. .turbodronepilot
     
  8. Hughie

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    I think you may have it.

    I have been doing compass calibration immediately after switch on and then doing the GPS/home lock after that, last, before the flight.

    When the compass calibration is done, I was expecting a solid LED, and I know the instructions say if I get alternate red and something the compass calib has failed. A compass failure is actually red and amber, the GPS acquisition is of course red and green. So, if a successful calibration is just that the green light goes off for a few seconds my compass calib has probably been OK all along.

    Perhaps the reason I have to do it 4 or 5 times before it "works" is because that is how long it takes for the GPS to get 6+ satellites :D

    I did notice however when I have just tried it that if I first get GPS greens, and then do the compass calibration after that, it is possible for the GPS to lose a satellite or two on the horizontal nose down part, and when complete show green and red again.

    Can anyone describe what a real compass failure looks like?
     
  9. Hughie

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    Thanks. Good tips to bear in mind.
     
  10. Hughie

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    OK thanks. I try to do calibration in an open space so hopefully this is not a problem this time.
     
  11. Hughie

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    Thanks for your comment, I am not a Visioner though just vanilla Phantom 2.
     
  12. SteveMann

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    Also, do a compass calibration if you add new equipment to your Phantom.
     
  13. BigPig

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    I was going to calibrate before each flight also since I read this on page 23, section 5.3(2) of the newly updated Phantom2 User Manual v1.2:

    5.3 When Recalibration is required:
    (1) When Compass Data is abnormal, the LED flight indicator will blink alternating between red and yellow.
    (2) Last compass calibration was performed at a completely different flying field/location.
    (3) The mechanical structure of the aircraft has changed, i.e. changed mounting position of the compass.
    (4) Evident drifting occurs in flight, i.e. the aircraft doesn’t fly in straight lines.
     
  14. Meta4

    Meta4 Moderator
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    Nothing there says you should recalibrate before each flight.
    DJI are over careful in the language they use in the manual.
    If calibration every flight was important, DJI would clearly say so.
     
  15. BigPig

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    I'll recalibrate if 1-4 above are true. Number 2 grabs my attention since I won't be flying at the same field all of the time.