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line of sight recovery if GPS is lost

Discussion in 'Phantom 2 Vision + Help' started by cjmwales, May 8, 2015.

  1. cjmwales

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    Yesterday I sent my phantom 2v+ higher and further away than I've previously dared, and I invoked RTH twice on the S1 switch to get me out of trouble - I made sure I had good GPS reception and a home point set.

    It really is a great feature for getting you out of trouble.

    It was only afterwards that it occurred to me - what if my phantom had lost the GPS signal in this scenario? I could still see the unit but working out which direction it was pointing at that distance was pure guesswork as I'd also lost video reception - in fact, the DJI app crashed several times on me during various flights. An errant gust of wind at that height would be a disaster in ATTI mode.

    Is there a fool-proof way of knowing which way your phantom is facing? Should I invest in some sort of ultra-bright LED to stick onto the front? or should I bring binoculars?

    It's easy to see how things can go pear shaped quite quickly. I am seriously considering investing in one of those stage 1 booster kits to firm up the video reception.
     
  2. msinger

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    It would have auto landed at it's current location.

    Look at the radar at the bottom, left of the DJI Vision app. That's only good as long as you maintain a Wi-Fi connection though. Once that has been lost, you can use the home lock feature to bring your Phantom back into range -- if you still have connection with the remote controller.
     
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  3. Meta4

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    The important factor to consider is, how likely is it that you would drop sat lock?
    If you have a late P2V+ or you have done the foil mod, and you are flying high and out in the open, it's extremely unlikely it would ever happen. Phantoms aren't noted for dropping sat lock and unless you drop into a canyon or under a forest canopy, I can't see it happening.
    Plenty of other things to be concerned about but losing GPS shouldn't be one of them.

    And definitely get to know your radar display.
     
    #3 Meta4, May 8, 2015
    Last edited: May 8, 2015
  4. cjmwales

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    I did spend a good portion of my first battery pack playing around with the radar arrow, getting used to how it responded & just developing my spacial awareness with it. But wouldn't home lock be reliant on a GPS lock?
     
  5. cjmwales

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    I've done the foil mod and the 4mm ceramic receiver change, just to be sure, and they've made a massive difference. But even so, my earlier flights with sketchy GPS have made me paranoid, perhaps overly so.
     
  6. msinger

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    Home Lock will only work correctly if your Phantom marked your home point before you took off and you still have 6+ satellites. Like Meta4 said, you usually will not lose satellites once in the air. It's more common to gain satellites.
     
  7. J.James

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    One way to tell which way its facing if you can still see the phantom is to just stop for a second and see what way it moves when you give it a bit of right stick. Tho that will only help if you can see it at all.

    But as far as losing GPS completely when In the air. That dont seem to likely unless some how your GPS unit had a wonky plug that broke connection in flight. Even on days when GPS reception is really bad you should usually still have more when in the air then when you are on the ground and ready to take off. Out of all the different phantoms I have had. The gps is one of the few things In them that I have come to know is pretty reliable. Providing you got a good home lock before take off. Even if it loses a few sats in flight it should still be able to find its way home if its in RTH. Tho the one thing I some times dont trust is if I use the switch to put it in to fail safe and if it seems like its taking a long time to reappear or hear it coming back. Then I switch off the radio just because there is no way that will fail to put it in to fail safe.
     
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  8. kirk2579

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    correct home lock does need gps

    course lock however does not. It will react based upon the course set at startup lock.
    that way you need not know which end is which.

    I kinda like evening flight just because the leds are so easy to see then..
     
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  9. len750

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    That's kind of genius! Binoculars. I never thought of that and I own a great pair. I'm going to practice with that next flight and just keep them on my neck from now on as a safety back up plan and make sure that bikini in the distance is worth a flyover. Just kiddin on the last part. Don't hate. Great cheap non technical idea though.
     
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  10. cjmwales

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    Well the unlikely actually happened to me yesterday!

    I was just having a bimble over Porthtowan beach, as it was quiet. According to my anemometer The winds were 12mph gusting to 18 - pretty hairy, but since it was such a large open space, I was happy the Phantom & I could handle it.

    I took off with 7 satellites, thinking that would be fine - but at around 55 seconds I went too close to the cliff, GPS is lost & 'Angry Bees' goes into ATTI & drifts rapidly with the wind. It was about 150 metres away but from the FPV feed I could quickly ascertain orientation & use corrective yaw, forward pitch & a bit of climb to arrest the drift before bringing it back to me, side-slipping all the way against the gusts.

    PUCKER FACTOR 9.

    My face at the end says it all :)

    Lesson learned? Topography can easily catch you out when it comes to GPS signal loss, check your count every few seconds (if flying by sight rather than FPV like I was here), take nothing for granted & be prepared to step in rapidly.

    It really would be nice if the DJI vision app had a full on screen-flashing warning and audible alarm to tell the user that the sat count has dropped below 6....!

    http://vid147.photobucket.com/albums/r281/cjm2007_photo/D2015May20143056DJI00087_zps89tobzvu.mp4

    [​IMG]
     
    #10 cjmwales, May 21, 2015
    Last edited: May 21, 2015