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Flying in Low GPS Signal Environments

Discussion in 'General Discussion' started by mtbendurogirl, Mar 10, 2015.

  1. mtbendurogirl

    Mar 10, 2015
    Likes Received:
    I took the drone out to a waterfall on the weekend, it was in a gorge, so rocky cliffs on both sides (like being in a narrow valley). If you zoom in to the attached pic you can see me and the kind of environment.

    The thing is, I wanted to take more shots from better angles but the Phantom was reading out 5 sattelittes, which is grey on the indicator, so I got paranoid and landed it (I have read about fly aways when they lose GPS signal).

    I wanted to try and flick the switch to "Atti" mode and fly semi manual (the mode where it just holds altitude, not position), but I was too scared and just landed and gave up.

    Has anyone here ever tried flying in low GPS signal, like say indoors? Is flicking to Atti the safe option, or does that (and I suspect it will) need GPS anyway and still be a fly away risk?

    Thanx for the help gurus!

    Attached Files:

  2. Lonewolf

    Jun 3, 2014
    Likes Received:
    Flying in a gorge like you've shown is not uncommon and yes, GPS signal may be either lost of diminished because of the cliffs hiding the GPS signals.

    However, flying in ATTI mode is not as harrowing as you might think. Practice doing so in an open field to get a better understanding of the physics involved and your confidence level will increase dramatically. Practice slow maneuvers at first and then gradually move on to more aggressive maneuvers in the open field. After a several minutes you'll be most comfortable flying in ATTI mode. "Flyaways" are most often operator/pilot error. In ATTI mode you'll have safer control of your bird if you've ever lost GPS signal.

    Finally, no. Flying indoors trying to obtain GPS signal is not advised. Too many obstructions to block their signal.
    Enjoy flying and have NO FEAR!
  3. Hughie

    Nov 22, 2014
    Likes Received:
    Leeds, United Kingdom
    Welcome to the forum.

    I suggest that it is essential that you practise in ATTI mode. This is not manual and this is not semi manual.

    In GPS mode with no input, the quad will hold its height and its position above the ground, as best it can.
    In ATTI mode with no input the quad with hold its height only.

    So, all this means is that with no input the quad will be carried by the wind if there is any. If the wind is not excessive you can fly through it.

    The other difference is that in ATTI mode the quad will hold a steeper maximum angle and so will fly faster than in GPS mode.

    So find a safe environment (start on a day when there is no wind) and once you are in the air select ATTI on the S2 switch and fly it around. If you are worried at any point flick it into GPS and it will immediately go back in to GPS mode (assuming you have satellites). Practise this. ATTI is your friend.

    Also a point on fly aways - which are not conclusively understood anyway. One hypothesis for fly aways is that if the home point is not recorded properly and the quad enters a return to home (RTH) mode, it can try to fly somewhere which is miles away. The remedy for this is to immediately switch from GPS to ATTI (which stops the RTH) and fly it back in ATTI.

    There is a real manual mode. Make sure it is not configured for use. This is very different to ATTI and I suggest you stay clear of it... for now anyway.
  4. landmannnn

    Jan 18, 2015
    Likes Received:
    Coventry and Limoges
    As above, don't practice new stuff in a gorge! Atti mode is a bit different, not only will the phantom drift in the wind, it also has momentum. So if you are flying along and let go of the sticks it will carry on and gradually slow down.

    When you practice it is recommended you mark out a course, perhaps a square, then fly to that. Generally flying around doesn't teach the hand-eye coordination you need.
  5. Meta4

    Meta4 Moderator
    Staff Member

    Jan 8, 2014
    Likes Received:
    The Phantom won't flyaway when it loses GPS signal. Quite the opposite.
    It would need a GPS signal to be able to fly to anywhere.
    WIthout GPS lock, the Phantom defaults to atti mode and without input from the pilot, it would just sit there and drift if there is a breeze. Presumed flyaways in this situation are most likely due to flying out of range and losing GPS leading to the Phantom being blown or drifting away and this being misunderstood by an inexperienced pilot as flying away.

    Atti doesn't need GPS. Atti is what your Phantom will do if you lose sat lock.
    And again .. it won't fly away.
  6. lake_flyer

    Jul 17, 2014
    Likes Received:
    The Low Lands
    If you ever did ice hockey.....in Atti with wind still weather, the phantom will behave like an ice puck.
    In a gorge you will get strange winds and vortexes on moments you cannot predict. Don't fly near any wall because it will suck itself towards it (lower pressure between props and wall).

    As said before: don't practice this in a gorge for the first time. First in a controlled wind still environment. Then you try it with wind. Lot of difference and the first time is scary because only 4m/s wind is already quite fast and before you know it, the bird is beyond LOS, keep a good eye on it.

    But Atti is your best friend, that's for sure. Saved me a few times.

    Better check your switches are functioning good, they are a bit low quality and some people reported malfunctioning right when they needed them. Check them in the software and move them up and down for a number of times. Make sure you see the function change accordingly on the screen while in the program.
  7. ianwood

    ianwood Taco Wrangler
    Staff Member

    Jan 7, 2014
    Likes Received:
    Lost Angeles
    GPS = driving a car with the parking brake on.
    ATTI = driving a car with no brakes whatsoever.
  8. capodrone81

    Nov 22, 2014
    Likes Received:

    I have kids so this comes to mind:

    GPS: driving a power wheels with a gas pedal only (brakes immediately when you let go of pedal)
    ATTI: driving a real car with both gas and brake when you let go of gas you need to apply brake otherwise it keeps going. :lol:
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