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Why does my Phantom take so long to get GPS lock?

Discussion in 'General Discussion' started by rilot, Oct 15, 2013.

  1. rilot

    rilot
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    My phantom can sometimes take well over a minute to get a GPS lock.
    I also fly an F550 with a Naza-M and it gets lock in literally seconds after connecting the power.

    As a test, I timed them both in the same field yesterday.

    F550. Full lock in 8 seconds after power connected
    Phantom. Full lock in 64 seconds after power connected

    Any ideas why?
     
  2. discv

    discv
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    A complete shot in the dark- your 550 GPS is on a tower, I presume, and the Phantom GPS is buried in the works?

    Edit- It would appear from the posts that follow, my theory might have some mileage. I wonder if it could be an option to lift the GPS up and out of the body-essentially as fitted to the 550.
     
  3. insatiable

    insatiable
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    Mine also takes a long time to lock on. I've not timed it but I am sure it's inexcess of 1 minute. After a flight, the subsequent flight if immediately after is already locked on and ready to go.
     
  4. Ksc

    Ksc
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    A local guy cut a hole in the center of his so the antenna has a direct line of sight to the sky. He says it speeds up everything.
     
  5. miskatonic

    miskatonic
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    I noticed that the IOSD MINI distinguishes from the number of satellites that the Phantom can see vs. the number that the Phantom has locked. For the longest time today my Phantom say six satellites but it would not lock onto the 6th until I moved it about three feet.
     
  6. FrankB

    FrankB
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    What this illustrates is the need to have a better GPS in the Phantom and, hopefully, the Vision. They should use a high sensitivity antenna, like the SiRF, and also use a GPS that is capable of making use of both the Russian GLONASS GPS system and also the European Galileo System when it becomes operational.
     
  7. The Editor

    The Editor
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    I don't think DJI would be concerned about making their system compatible with Galileo - A project that is currently running over six years late, has been beset by problems from day one, lost most of it's funding, not that technologically advanced and with the US about to update the already proved GPS system that makes Galileo out of date! It's a vanity project devoid of all commercial logic. I seriously wouldn't hold my breath for an EU conglomerate to complete on a project that nobody wants or needs...... Oh wait a minute... it's the EU... THAT'S exactly the sort of project they might finish :lol: :lol: :lol: .

    Seriously though - if you were a company making UAV's would you seriously waste good time and effort on R&D on something that isn't and may never become operational this side of 2020?
     
  8. MenaceCat

    MenaceCat
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    May I suggest that the issue is less about antenna sensitivity than about the time required to acquire satellites under different contexts.

    Although the original poster claimed that both systems were deployed in the same field, it matters whether one of the systems had more recently acquired a lock - in the last minutes or 2 h. If such, the system is said to 'hot start'. If you turn on a GPS receiver from a 'cold start' (haven't used the system for many hours or days) ~45 s is not unusual*. All this is related to the currency of that devices GPS ephemeris data.

    This has to do with the updating of satellite position and timing information which is done every few hours and not with hardware.

    Global Positioning System (GPS) navigation satellites transmit electronic ephemeris data consisting of health and exact location data that GPS receivers then use (together with the signal's elapsed travel time to the receiver) to calculate their own location on Earth using trilateration.

    Again, nothing to do with different satellite constellations (e.g. GLASSNOS) as the basic process of satellite acquisition is common across that factor. The GPS chips are made by companies like Broadcom / Philips / Sony. DJI won't have resources to design these.

    *Look at https://www.sparkfun.com/products/465 for data on tine ti GPS lock.
     
  9. rilot

    rilot
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    Both were from a cold start, neither having been flown for about 2 weeks.
     
  10. MenaceCat

    MenaceCat
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    Try a few times. What I said is technically correct. The GPS on the phantom is by no means an inferior unit.
     
  11. miskatonic

    miskatonic
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    I might have an answer for this. I took my Phantom apart today to do some repairs. I even looked under the hood at the GPS.

    The GPS has a tiny battery. I don't know for sure but maybe this battery is for recording GPS locations. Try replacing it and see if your lock times get batter.

    [​IMG]
     
  12. PhantomFan

    PhantomFan
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    Is a minute delay so hard to tolerate? The difference is interesting, but not important from a practical standpoint, and I certainly wouldn't call it a defect. For such an inexpensive machine with so many capabilities and safety features, 60 seconds seems like a bargain.

    I guess you've never flown the old-school glow-fuel models. By the time you get to the flying field and deploy all your stuff (field box, gallon of glow fuel, set up your car charger (for Rx and Tx re-charging) assembled and fueled your plane, got the engine started and fuel mixture set to slightly rich (so it leans out mid-flight to optimal) - an hour and a half may have gone by.

    60 seconds seem like a bargain now?? :lol:

    PF
     
  13. rilot

    rilot
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    Oh, I don't have a problem with it at all. It takes me a minutes to get set up anyway.
    I was just curious as to the reasons why compared to the Naza-M in my F550.
     
  14. miskatonic

    miskatonic
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    The Phantom is a precision machine and it has a lot going on with the internals. If you do have a dead battery or even a dislodged battery I would look into it. No telling what else that battery may do.
     
  15. rilot

    rilot
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    Huh?
    There's nothing wrong with my batteries and I'm well aware of what's inside my Phantom.
     
  16. BrewserB

    BrewserB
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    I have 2 phantoms. Me and my friend fly them both. For some reason my newer one takes longer to get a GPS track. It's about a min. so it's no big deal but it does take longer for some reason. I don't really care because he was flying my Phantom and totally lost it in the sky crossing a lake. It was totally out of sight. He shut down the controller and about 3 min. later we found it hovering over our head. It was starting its decent. I was totally amazed. What a feature. I would have lost my copter and gopro 3 black. That's a lot to worry about...LOL
     
  17. PhantomFan

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    I don't presume to speak for miskatonic, but I interpreted what he wrote as trying to say is if your GPS battery was dislodged and loose within the GPS unit, it could cause a short or some other problem. If (when!) I have a bad crash and the GPS seems a bit wonky, I'll remember to check on that.

    I had no idea there was a battery in there! Makes sense now that I think about it. If the Phantom is powered up close to its last known position, I'm guessing it would probably cut down on the satellite search time. Certainly is true of the one in my car.

    PF
     
  18. rilot

    rilot
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    Ahha, right. Sorry.
    I'll check mine when I get a sec. Wife just had a baby so I'm a little short of time at the moment :)
     
  19. miskatonic

    miskatonic
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    Exactly, Thank you for the clarification PhantomFan! :D
     
  20. fizzviic

    fizzviic
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    I have been wondering about what folks mean by GPS lock and the time it takes. Once my IMU finally warms up and the yellow light quits flashing, it only takes seconds for my Phantom to cycle through the double green and the reds until I have a solid 6 or more satellites locked on and I have a "green board" for flying.

    My problem is the approximately 2 minutes of blinking yellow, which from what I can determine from the manual, is the IMU "warming up"

    Any thoughts?
     
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