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Unpublished No Fly Zone - Ever Seen This Behavior?

Discussion in 'Phantom 2 Vision + Discussion' started by ToddSmi, Jul 17, 2014.

  1. ToddSmi

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    So I'm flying out at a lake and get an unexpected red led warning light (consistent with a no-fly zone warning) that results in the loss of stick control through GPS mode.

    Watch this short video for all the details:

    [youtube]http://www.youtube.com/watch?v=N2hSlhQ9_K8[/youtube]

    I'm very curious if anyone else has had this specific problem before? Also, after carefully reviewing the "Flight Limits" section of the manual (pages 29-31), I'm still not clear on why ATTI mode would work fine and GPS mode would not. Maybe I am missing something?

    Oh, and just to answer the normal questions. V+ is all stock, latest firmware, has about 15 flights on this particular unit, no crashes, everything looks normal in DJI assistant, distance limits are set at default values, had a good compass calibration, etc etc. Nothing out of the ordinary until the copter just stopped responding to the sticks and appeared to freeze in place. Not sure what would have happened if I had left in GPS mode, but I didn't want to wait to find out! Being out in the middle of the lake like that, I have to admit I felt pretty exposed!

    So has anyone else seen this happen before? Any theories on what would cause it?
     
  2. cahutch

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    Since you were moving quickly in a boat, your home point would have been your launch point behind you. Had you moved 1500 meters from the point you launched it?
     
  3. ToddSmi

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    Good question. I was within a half mile of where I set the home point, so less than 800m.
     
  4. phantomguy

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    What would 1500 meters have to do with anything?

    However, did you have any flight distance limits set within the DJI software?
     
  5. ToddSmi

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    1500 meters is the default setting in the current DJI Assistant software, and I was set at the default values. So this was a great point brought up, but since I was less than 800 meters from homepoint (less than a half mile), this shouldn't have been what caused the problem. Any other ideas out there?
     
  6. cahutch

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    Maybe you launched it a while after it got the GPS lock and set the home point?
    In other words, you turned it on, it started up, got GPS lock and set home point.
    Meanwhile you're still moving.
    Then you launched it a few hundred meters after that.(?)
    Then ~800 meters later it reached the 1500 meter limit from the initial point it set home.
     
  7. ToddSmi

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    I like your thinking as this would be a good explanation for what happened...except that I confirmed homelock direct from boat then launched less than a minute later all while boat was not moving. Could it have been some kind of GPS mis-recognition that caused the V+ to suddenly think it was in a no fly zone? But in that case, would atti have worked fine like it did? Is that why you are very suspicious of a flight limit restriction instead of no fly zone problem? In the manual, it is very difficult to discern any difference in the warning lights for these two issues. I had been leaning towards this being some kind of no fly zone malfunction because I knew I was well within flight restriction limitations (and in fact was aware of this limitation when flying so the boat driver was instructed to stay in a pretty tight circular radius of takeoff point).
     
  8. cahutch

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    AFAIK, the no fly zones are only Airports. No idea why there would be one in the middle of a lake.
    Distance limit would seem more likely.

    Yeah, ATTI mode should ignore any no fly zones and distance limits. It basically ignores GPS.
     
  9. Dirty Bird

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    There are different onscreen messages for exceeding your geofence limits, and flying in a restricted flight area. I have received the restricted flight area warning a couple of times when flying at my cousin's house. I can't recall the exact wording of the onscreen popup but, aside from alerting you that you are in restricted airspace, it also details your altitude limit for the flight. In my case, my altitude was limited to 309m both times. Not sure why it picked "309m" but that's where it drew the line on altitude.
     
  10. ToddSmi

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    Interesting. I had looked in the manual to try and find pictures of the app warning message alerts for comparison to what I saw during flight, but it doesn't appear that DJI has included this in the documentation. But I do remember seeing something like "flight limit exceeded" on the app so based on your guys input, it sounds like this is a geofence problem and not a no-fly zone problem. I'm certain that I was not greater than 1500m from homepoint, so still not sure why I would get this error, but am glad that at least we seem to have narrowed down the issue somewhat. Thanks for the input.
     
  11. ElGuano

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    The ringfence is a good guess. I never use it so I don't know what the LED pattern is when it's hit. But if you are in a no-fly zone, it's hard to miss the little airplane-busters logo that shows up:

    [​IMG]

    Another thing to note is that home point isn't initially recorded until you first arm the motors. So if you were powered up but unarmed while on deck and moving, you might be in a situation where your homepoint isn't where you expect it to be.
     
  12. ToddSmi

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    I waited for homelock confirmation (remember sticking my head down low and shading the copter to see the rapid succession of green lights), but a very good point on your part. Regarding the error message, I wish I had remembered to get a screen grab. I'm fairly certain that the app message did not say that you are in a restricted zone nor give any numerical limits (like the example you showed). And I do recall that it said something to the effect of flight limit exceeded. But interestingly, I believe I saw an icon with the red circled out airplane (was incredibly bright out and hard to read my phone screen as you could imagine). Maybe DJI uses the same icon for both warnings?? I guess this would be easy enough to test. I can set my range limits really low and find out in a hurry. Will give that a try tomorrow.
     
  13. MattBW

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    I read when researching ground station that height is based on the actual land not on the surface of the water, if the water is deep, won't that mean you are effectively flying at sea level plus whatever depth of water? Im a newb so excuse me if Im talking rubbish ;)
     
  14. Cocoa Beach Kiter

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    If I understand it correctly, I believe GS uses the altitude referenced your zero point which is when you turn on the Phantom. Or unless you establish a different homeport. The altitude you select in the GS then is referenced against that altitude ... I can't imagine there is a terrain database included with the Maps function which would give altitude of your location. And there would be no way for that to be adjusted based on barometric pressures for local conditions.
     
  15. ElGuano

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    You may have been looking at the PC GroundStation documentation (which I haven't personally used), that has options to use Google Maps terrain height (which is coarse and doesn't take into account trees, etc., so use caution).

    The P2V+ GS goes solely by altitude above home point, as recorded by the Naza.
     
  16. ToddSmi

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    Okay guys, I just completed a test and learned some interesting things.

    I set the height limit in the Assistant software to 15 meters for a quick test. When I got to that height, the attached message came on my DJI app and I couldn't fly any higher. It does appear that DJI recycles the "airplane with crossed out circle" icon for more than one warning message. So this would seem to imply that maybe this message is what I saw and we could narrow it down to some type of misunderstanding between the default flight restrictions and where the flight controller thought I set the homepoint. However, I also noticed that when I switched out of GPS mode to ATTI mode after receiving this warning message, ATTI mode would also NOT allow me to fly any higher...so it appears that both GPS mode and ATTI mode are equally affected by the flight distance restrictions set in the Assistant software. So...that means I really don't have a clue what the warning lights were indicating to me as I lost total stick control in GPS mode at the lake, and then was able to recover as if nothing had happened in ATTI mode, with the red LED warning lights still active.

    Is any of my logic faulty here? Or any other ideas what may have happened?
     

    Attached Files:

  17. ToddSmi

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    After the last post, I realized I probably should have checked the distance limit, not the height limit, so I tried again. Set distance limit to 100 feet, and attached you can see the similar warning message. I noted the same red flashing led pattern on the model when I reached the limit. Interestingly however, unlike the height limit, the distance limit could be overcome by switching to ATTI mode. So...back to the initial theory that was posted on here. When flying at the lake, the Flight controller thought I was exceeding the distance limits imposed in the Assistant software and that is why I saw the intermittent flashing red led light warning, followed by standard LED lights, back to intermittent red flashing, etc., and that is why control from GPS mode stopped cold in its tracks, and ATTI mode was able to continue functioning.

    All evidence seems to point to this being the problem, and that I must have been much much farther away from my homelock point than I had previously thought, or some type of miscalc by the flight controller (I know, the latter is unlikely...just trying to wrap my head around how my distance measurements could have been off so wildly...was using a gps device to track).

    Anyhow, the key takeaways for me are:

    1) I now have a much better understanding of how the flight distance restrictions work vis-a-vis the DJI warning lights and now understand how model behavior is affected in both GPS and ATTI modes.

    2) Even if you are focused on staying within a tight radius of the mother ship (or whatever movable platform you are on), it is not worth it to risk flying when you have default flight restriction distances enabled if you plan to use GPS mode at all in your flight. Just turn up the restricted distances in the Assistant software ahead of time if you are planning to do anything where you are moving!!! Or maybe just leave them high all the time.

    3) If any DJI personnel see this, I would recommend changing the graphic on the app so that there is a different graphic for exceeding flight distance limits vs being in a no-fly zone to make it easier for folks to identify what warning they have actually triggered (since the LED flashing pattern on the copter seems to be the same for both warnings, having as much clarity in the app warning would be helpful).

    Final question: Is there any drawback any of you can think of to just always leaving the limits extremely high? This would just be like before they instituted that new feature, correct?


    Thanks all for helping me get to the bottom of this! Hopefully, someone else will benefit from reading about my experience.
     

    Attached Files:

  18. happydays

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    Good thread, well reasoned arguments and glad you found the solution.
     
  19. ElGuano

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    Todd,

    This is a really great thread, thanks for updating everyone with your troubleshooting, and I agree with your conclusion. I KNOW having spent a lot of time in and on the water that it's naturally very difficult to judge distance, and you might end up a lot farther out than you first imagine.

    As to effectively disabling the distance limit (set to 0, or far enough out that you'll never hit it, like 10,000m), I don't see too much downside unless you know you're 500m from a military installation and want to ensure you don't accidentally fly into it. If something causes a loss-of-control failure or true flyaway, it's unlikely IMO that the Phantom will be responding in a way that will make it respect the distance limits anyways.

    I fly my Phantom on fw4.0, so my distance limits are set out at 10,000m...

    Also, good suggestion to DJI on not recycling the airplane icon for the distance and height limits. There are a few language bits on the Vision app that could stand to be clarified.
     
  20. ToddSmi

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    Thanks El Guano. I always enjoy seeing your posts on the forums and value your insights. And my distance limits have been officially changed :D