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  1. bkushner

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    Sometimes flying on the Delaware River I go under a bridge where my GPS drops dramatically. If I'm going to fly under a bridge would it be better in ATTI mode?
     
  2. With The Birds

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    Yes, or prepared to be.
     
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  3. macoman

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    I flew the other day under the commodore Barry bridge and didn't lose GPS signal. I have a P3S.
     
  4. Goof

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    The IMU should be able to dead reckon for a small period of time without satellite contact, but AFAIK the software tends to kick straight into ATTI mode anyway. Be aware of the air movement before, under and after the bridge and be prepared to counter its movement and you should be fine.
     
  5. John Locke

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    Yes, this is where it's good to have some experience flying ATTI. I've had the same think happen when flying under a cement bridge in close quarters. Knowing your risk in ATTI is essential, based on wind factors and drone clearances. Many professional videographers prefer flying in ATTI to have smoother video results, looking more graceful, less sudden stops, etc. In ATTI you'll be able to maintain elevation with no problem, but side to side slippage is where some experience under your belt helps build your confidence and know your safety limits.
     
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  6. GadgetGuy

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    A bigger concern is losing RC signal, if you will be losing LOS while under the bridge. Should that happen, RTH altitude ascension will be your enemy, and not your friend! Make sure you are flying fast enough that you can get out from under the bridge before RTH kicks in! :eek:
     
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  7. Meta4

    Meta4 Moderator
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    If you lose GPS, your Phantom is in atti mode anyway regardless of what you do with the switches.
     
  8. bkushner

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    I have RTH set to compensate for being under the bridge. When flying over I do the same thing .
     
  9. MGS9500

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    I thought RTH altitude depended on a GPS signal. How would the drone determine the correct altitude under a bridge? I thought with loss of GPS it simply hovers until acquisition.

    Loss of GPS is different that loss of signal.

    When my drone has had loss of GPS, it will fly under manual but will hover until I take over.
     
  10. Meta4

    Meta4 Moderator
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    If you lose GPS, your Phantom can't find its way to anywhere and will just hover unless you provide some control input with the joysticks.
    But you shouldn't be losing GPS unless you fly under cover that blocks GPS reception.
    Your Phantom determines its altitude under a bridge the same way it does anywhere - using its barometer.
    GPS is 100% unrelated to altitude.
     
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  11. Tommy J 111

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    Somebody please explain if im wrong.
    when i loose signal my p4p+ seems to back track until it finds signal, then it comes home.
     
  12. bkushner

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    Yes now I'm concerned..So if I go under bridge, lose gps and signal but drone just sits under bridge until it dies and falls in the water?
     
  13. John Locke

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    If that were to happen, losing GPS and also control signal, the drone would drift in the wind in ATTI and crash into the first obstacle it finds. It wouldn't die first.

    Just make sure you have a LOS connection as you fly under the bridge and you're golden.

    If you encounter ATTI mode, using the right stick to counter left-right drift is more helpful than using the left stick for yaw direction. Practicing ATTI flight beforehand will help learn to adapt when flying ATTI.
     
    #13 John Locke, Aug 23, 2017
    Last edited: Aug 23, 2017
  14. GadgetGuy

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    The key is that any 3 second loss of signal will trigger your RTH setting, and you cannot set a negative RTH value, so if you are flying from any altitude above the bridge, setting to anything other than "hover" for signal loss will cause the aircraft to elevate and crash into the top of the bridge. OA does not work directly above the aircraft. So, if you lose signal, and set loss of signal setting to "Hover", you will have to move closer to regain signal control before the battery "decides" it needs to land, as it will then autoland beneath the bridge into water, or whatever is beneath it. Be careful and vigilant! Flying under bridges is cool, but can be risky. Don't attempt it unless you know and accept the risks!
     
  15. John Locke

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    I went into ATTI flying under this bridge about a year ago at Big Bear Lake, just below the dam. I lost GPS signal flying too slow and lingering too long under the bridge. It blew all over the place because of wind. Fortunately I managed to keep it away from colliding with anything.

    [​IMG]



     
    #15 John Locke, Aug 23, 2017
    Last edited: Aug 24, 2017
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  16. GadgetGuy

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    5 lane bridges, like this, are a little more challenging from 2 miles away!
    IMG_6086.jpg
    The hardest part was the auto exposure change in the video. It opened up under the bridge, and then grossly under-exposed, as it came out the far side, into the setting sun, during the 10 second signal loss, so I couldn't override it, so I turned it into an artistic effect, as though it was intentional. :cool:
     
    #16 GadgetGuy, Aug 24, 2017
    Last edited: Aug 25, 2017
  17. John Locke

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    You got me beat, mine was only 3 lane, and I was about 200' away. :cool:
    upload_2017-8-23_22-3-7.png

    We want to see your video pal. 2mi away, that's really asking for trouble, glad you made it through.
     
  18. GadgetGuy

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    Trying to find it now! I think it was with the P3P, so may require some digging! That seems like a lifetime ago! I do remember flying at full speed, which was 35mph or so, before Sport mode existed, and before OA, which seems to get in the way of my recent similar attempts!
     
  19. KevMo Photog

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    I
    I'm amazed that you didn't lose RC signal going under that one at 2 miles out! Wow!
     
  20. GadgetGuy

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    I did, but not for a full 3 seconds, until I was on the far side, out from under it. At 35 mph, 51 feet per second, you can cover a lot of ground in a very short period of time! As Adm. David Farragut said, "D*mn the torpedoes, full speed ahead!" :D
     
    #20 GadgetGuy, Aug 24, 2017
    Last edited: Aug 25, 2017
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