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New P2V... compass?

Discussion in 'Phantom 2 Vision Discussion' started by mb33139, Feb 14, 2014.

  1. mb33139

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    Greetings to everyone here on the board. I am a relatively new P2V owner and have been lurking around these parts for a bit. Lots of very experienced users here and I'd like to thank you all for sharing your knowledge.

    Anyway, in the last couple months, I've had one fly away and since then I've been trying to figure out why it happened. Short version is this, I launched the Phantom Vision from an outdoor handball court (cement floor surrounded by metal fencing) with the intent of filming a game from about 25" overhead. After hovering for a couple minutes, the Phantom ended up slowly flying off in a random direction about 1,000 feet. After a moment of panic (I lost FPV and controls didn't seem to work), I ran after her and was able to reestablish contact over a heavy intersection and strip mall. LUCKILY, I got her to come back to me.. The Phantom was calibrated and achieved satellite lock prior to flight. Winds were light around 5-10mph. After returning to the handball courts, I flew her again, but kept her within arm's reach (boring!!) because I was so spooked.

    So my questions is this, would flying the Phantom over a cement floored area surrounded by metal fencing interfere with the compass? I've been doing some testing over large cement areas and the P2V does seem to "wobble around" more than compared to open grass. Ideally, I'd like to set her to hover above the heads of the players so I can record video, but thus far, it is not possible without a lot of manual position corrections (and wobbly video). She seems to wonder around a 5-8 foot area.

    Any insight or tips would be appreciated.

    Oh, and for those suffering through snow or bad weather, here's my greetings from South Florida:

    [​IMG]


    EDIT: are img tags not displaying images for new users?
     
  2. nhoover

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    Sorry - I fly in non-urban places only. I'm logged in and cannot see your image.
     
  3. Pull_Up

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    If your previous flight was trouble free, and you are in any doubt as to the ferro-magnetic nature of your current location then don't calibrate your compass.

    Concrete might be reinforced (lots of metal rebar in there), metal fencing can certainly affect things (I know this from experience), there could be metal conduits or pipes underneath, etc.

    My rule of thumb is if in doubt, don't calibrate - provided you had no issues last flight out and you aren't many tens of miles away. If you notice anything other than your usual benchmark hover in GPS mode bring her in immediately and go and do a calibration in as clear an area as you can find (preferably a big open field).

    Always do a test hover no more than 10ft off the deck for abot a minute after a new calibration or in a new flying area (or even every flight). Any issues should show up almost straight away and you're a hand-grab away rather than 50ft up and heading off.

    My opinion, anyway! :D
     
  4. ianwood

    ianwood Taco Wrangler
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    Metal fencing = Faraday cage.
     
  5. Pull_Up

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    I'm dredging up a physics lesson from a looooong time ago but I'm sure we did experiments with a Faraday Cage and it had no effect on a compass. Might be misremembering, though. Any ferro-magnetic components in the fence certainly will have an effect if you're close enough.
     
  6. Big Ben

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    When it flew away did it perhaps simply drift downwind?

    Loss of GPS fix would make it change to ATTI and drift downwind. The concurrent loss of control could fit a strong temporary interfering signal blocking both GPS signal and control signals. An interfering signal could also cause a flyaway in any direction. Hence RAP. Did you have Failsafe with RTH enabled? And RAP? (Does a P2V have the RAP option when not in NAZA mode?)
     
  7. ianwood

    ianwood Taco Wrangler
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    A compass shouldn't be impacted if the faraday cage is uniform enough. I was thinking more about the loss of range and impact on GPS signaling. If you're standing in what is effectively a semi-effective faraday cage and then you fly your Phantom out of it, your GPS position can jump once you clear it and your range is going to be severely impacted.
     
  8. mb33139

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    Good point on the rebar. I always do the hover test, and in this instance, I actually did it over the same cement but in a different area. She held position fairly well, even when I manually pushed/dragged her a few feet in a different direction. The only difference between the hover test and the fly away was that I was flying her around trying to get a good video angle. Maybe the cement interfered with the compass and the problem didn't appear until I started movement? Hmmm...
     
  9. mb33139

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    Was clear skies over head and at launch, I had seven satellites locked. LED's flashed green the whole time I could see the P2V. RTH was enabled, but did not activate. Could be that control was never actually lost and as she flew away from me and my visual became difficult, my panic'd attempt at control sent her further away (would explain lack of RTH). This was only my third time flying after all...

    Flyaway aside, my real concern is whether the P2V can hold position over cement well enough to shoot stable video? I don't see why not, but my efforts have not really bore this out.
     
  10. Pull_Up

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    If you have a good calibration in the bag I don't believe it will be a problem. Best thing to do would be go to a nice open grassy area, calibrate and see how it flies. It should hover within about a 6ft circle. If it's still not right then it might be worth plugging in and doing an IMU calibration...
     
  11. Big Ben

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    My advise would be to familiarise yourself with NAZA mode ASAP and switch to that mode so you can use IOC with Course Lock and Home Lock. I wouldn't be surprised more P2 than P1 owners experience flyaways due to loss of orientation and control because of the absence of these very useful features.
     
  12. Pull_Up

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    ...assuming they've familiarised themselves with the totally different LED light patterns and understand how the IOC modes work and when they won't (absence of a good home location lock, for example). I kind of agree with DJI in this respect - learn to simply fly the aircraft first, learn how to visually orientate yourself first (i.e. don't fly it too far), then activate the NAZAM mode if you want to - knowing you probably won't panic if you have learnt to rely on IOC and it's not available...

    Same as full-scale flying - you learn to navigate with a map and a ruler first (and must carry a paper map in the cockpit by law), not because of some old-school thinking but because when your GPS fails one day you have a fighting chance of navigating your way back home/to your destination using something that doesn't have electronics in it. :)
     
  13. Big Ben

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    Nice in theory. Unfortunately this happened on his third flight. Can't really expect much experience with orientation by then. Yes, maybe he should have gotten that experience first but in the absence of that simply knowing you can flick a switch which will let your bird fly towards you when pulling the right stick no matter where it is can be a great asset to have. Especially for inexperienced pilots.