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RTH in P-atti mode? (Low Sat count)

Discussion in 'Phantom 3 Help' started by Baaspiet, Apr 25, 2016.

  1. Baaspiet

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    Hi guys,
    I was wondering if anyone has experience or knowledge of this. On Saturday I had plans to film waterfalls in a valley with extremely high mountains on either side. Before taking off, my P3S reported safe to fly, but non-gps mode (P-atti). I'm comfortable with flying in atti mode and I know RTH is available in ATTI provided you have sattelites, but I'm not sure whether RTH will be available in P-ATTI mode with a low sattelite count. In my case, it picked up 5 sats, and this was 1 short of being sufficient for P-GPS. I know that position hold in P-GPS requires more sats (at least 6) because it needs to be very accurate, but my question is :
    Although the sattelite count is too low for P-GPS and position hold, surely DJI programmed the units to be able to use any sattelites it could find to use in RTH mode, and attempt RTH, even though that count may be too low for P-GPS and position hold? Or not?
    (I do know and realise that the home point obviously needs to be recorded for RTH to work, but lets assume it has been recorded).
    Help would be greatly appreciated. Thanks


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  2. Meta4

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    DJI haven't made any specific comment that addresses your situation.
    It could be something for you to test.
    My guess is that without 6 sats, the Phantom will not use GPS at all and stay in atti mode and RTH would not happen.
    If that was the case, you would have to pay particular attention to where your Phantom was at all times because it would be up to you to bring it home without RTH as backup.
    If you had clear above the Phantom, you might be able to climb until your Phantom could see more sky and then RTH in an emergency?
     
  3. Baaspiet

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    I should have tested it at close range there. Think I'll go back and test again, but I'd really like to think that the phantom tries to get back home at all costs regardless of a sat count too low for P-GPS. I hope support can answer me and I'll post back here.


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  4. Meta4

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    Until you get the required 6 sats, it's as if you have zero.
     
  5. Baaspiet

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    That's what I would assume as a precaution, but why? If you need only 3 (a guess) for geolock in other practical applications, why would the phantom require a full 6? Again, I know it needs at least 6 for P-GPS because it needs to be very accurate to be able to hover so accurately, but if it can make do with 3 in an emergency to determine its approximate location, why not use that at all costs to try to return to homepoint?

    UPDATE : This was the response from the official DJI Suport facebook page just now:

    "As long as a homepoint has been set, the aircraft will try to return home, even if there's low GPS signal below 6 bars."

    That's fantastic news. I sincerely hope it's factually correct.



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  6. jogforfitness

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    Going through a hypothetical situation. What if your phone/tablet crashes/battery runs out/etc. The RC is out of order. The Phantom 3 at this point loses contact with the RC. My belief is that the Phantom will initiate a RTH. If so, how could there be any usage of GPS/satellite info if the RC is down? I'm new at this but thought that it still would know (through magic?) where to return? If the Phantom requires GPS/satellite and can't communicate with the RC, how could it get the info needed to successfully RTH?


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  7. mdowney58

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    The GPS data is received by the Phantom, not the contoller or the mobile device.

    Also, before take off, the home point is recorded, and that data is also stored in the Phantom.
    If your home point was accurately set before takeoff, and not altered during flight, you can turn your RC off, and the Phantom will return to the home point.

    Sent from my SM-N910V using Tapatalk
     
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  8. Meta4

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    Your Phantom has its own GPS and there is no GPS in the controller unit.
     
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  9. robert eckert

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    nice pictures meta4 were is it?
     
  10. robert eckert

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    btw my phantom doesnt get any gps since i upgraded it, is there any trubble with the upgrades?
     
  11. RodPad

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    So for testing the OP question, you startup with proper satellite count. Then block the GPS signals with some foil, and try the RTH function. Anyways good information.
     
  12. Meta4

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    Photos are from Eastern Australia.

    Updating firmware should have no effect on satellite reception.
    Are you indoors perhaps?
     
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  13. robert eckert

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    today i finally had reception for a few seconds, maybe this could be something local since i am living in protugal. Are there ares in wich the signal are stronger? is there like a map to see wich exact locations have best reception in portugal? btw the pics are amazing ;)
     
  14. Meta4

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    GPS coverage is global.
    [​IMG]
    Wherever your Phantom has an unobstructed view of the sky it should be picking up satellites.
    If you have an android phone/tablet, get an app called GPS Status.
    It will give display the satellites that it can see in your sky for something to compare to.
    [​IMG]
     
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  15. RodPad

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    You come up with some of the coolest stuff...
     
  16. robert eckert

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    super nice i will try it later on if the weather clears up a bit ;) thanks for your help meta4