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No GPS Lock Due to Low Satellite Count

Discussion in 'Phantom 2 Vision + Discussion' started by CoolP, Nov 13, 2014.

  1. CoolP

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    Where do I begin? I am a professional videographer and have a newly-purchased Phantom 2 Vision + which I bought in Philadelphia, PA. I calibrated it, took it out flying twice, and it gave me solid performance. It was truly like having a tripod in the sky. I consistently locked onto 8 or 9 satellites with no drifting in moderate winds. Now here's the kicker... I run a video production company down in Port-au-Prince, Haiti (where I currently live), and where I had always intended on using the Phantom.

    While I undersatand that a change in location will always require calibration (I calibrate before every outing anyway) I have never been able to get GPS lock down in Haiti. At first I thought it might be the abundance of high and low tension wires all over the place, but ruled that out after going to wide open spaces that were completly wire-free. I've checked apps and websites for the number of GPS satellites available at my location in Haiti, and while there are on average 2 fewer than Philly at any time of the day, there should still be enough for me to get a GPS lock with a rare minimum of 6. I am usually locked into 4, but have even occasionally gotten 6 or 7, but never long enough to establish GPS lock. Being forced to use the Phantom in ATTI mode is out of the question since that will cause me to concentrate solely on flying, rather than taking video (and defeats the purpose of my getting the Phantom in the first place.)

    I have read about rerouting the GPS cable and shielding it with aluminium tape, but am very reluctant to open up my Phantom after having it for less than a week. Also, I've seen at least 2 other Phantoms flying around with rock-solid performance (even though I realize they might have been Phantom 2's, which don't have this particular GPS problem.)

    Can anyone think of anything else I should look at, before I take the plunge and open up my brand new Phantom? Any suggestions are greatly appreciated, and I will keep everyone up to date on my progress.

    Thanks in advance!

    Thanks!
     
  2. Meta4

    Meta4 Moderator
    Staff Member

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    The Phantom has a known flaw that affects GPS reception.
    The cure is the foil mod that you mentioned.
    It's easy and fixes the problem for almost everyone.
    It makes such a big difference, I wouldn't fly without it.
    I get 11 or more sats every time I fly .. had 16 the other day!!
     
  3. msinger

    Approved Vendor

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    The foil mod will no doubt be the easiest thing to try first. And opening your Phantom is a simple task (if you have the right tools). I first opened mine two days after I bought it.

    See this video for instructions on opening it:
    https://www.youtube.com/watch?v=FLgwyoJvqM8

    Make sure you have the following tools to prevent stripping the screws (especially the small ones on the outside of the arms):

    • 2mm Hex Screwdriver (Amazon)
    • 00 Phillips Screwdriver (Amazon)
     
  4. burlbark

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    I would open it up and do the foil mod unless you have a dealer close to you and I kind of doubt that. I loved that tropical island I was there in 94 and got to swim in the surf and visit the presidential palace. If this is Cedric we can talk about all of this tomorrow after 10am pacific time. By the way your gimbal is up and running....:)
     
  5. CoolP

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    No, this isn't Cedric...lol..., but thanks for the advice. Being in Haiti doesn't give me the ability to easily ship things out, or get things in. The foil mod is an attractive approach since I have clients waiting, and can'r really afford to wait the months it will take to send it to DJI and get it back. Unfortunately, the Presidential palace is no longer aroiund after the earthquake we suffered in 2010. But one of the projects a will be working on is documentation of the development that has been taking place since the earthquake, making the Phantom a very necessary tool.

    Since the Phantom was working fine for me in Philly, I'm assuming that was because I simply had more satellites available to me period.

    I'm still looking for suggestions of things I might be overlooking. Thanks.
     
  6. N017RW

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    Satellite availability is the same anywhere on the globe with the exception of orbital periods which vary from time to time and are predictable. So on the average you have the same number available to you anywhere on the planet.
     
  7. 4wd

    4wd

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    Yes it makes little sense that the new location has significantly fewer.
    I'd suspect damage to the GPS antenna during the journey.
    This is potentially hazardous as you could lose all satellites for no obvious reason during a flight.
    A replacement is relatively inexpensive and easily fitted - once it arrives!
    First step would be have a look inside as sometimes damage is visible cracking.
     
  8. CoolP

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    I'm not too sure about that. I did not check-in the Phantom on my flight, (and even bickered with a flight attendant who tried to force me to check it at the gate.) It did not experience any rough handling at all during my trip. I've checked satellite availability using websites and an iPhone app, and have again verified that on average I get two fewer satellites than I did in Philly, but again above the 6 needed for GPS lock.

    This morning, I fired up the Phantom (indoors) and after several calibrations, got as much as 5 satellites (I'm going to try it outdoors in a couple of minutes to see what I get.) I have also verified (which I did't do before) that whenever I start recording video, the satellite count immediately drops to 4, then 2, then zero, then back up to 5 once I stop recording, signaling that this might very well be due to interference as everyone is reporting. I'm sure this was happening to me in Philly also, but the increased number of satellites available to me there compensated for the ones I didn't lock on to.

    So now, more than ever, I'm tempted to try the GPS cable shielding mod. However, does anyone know if switching the Phantom from FCC to CE compliance might make a difference? ( I doubt it will, but thought it was worth asking.)
     
  9. N017RW

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    FCC vs. CE is controller transmit power.

    No effect on GPS reception issue(s).
     
  10. happydays

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    If your Phantom is only two weeks old, it might have had the DJI upgrade to the shielding that many have mentioned on here. Unless it was old stock that hadn't been sold yet, of course?

    Still probably worth doing, IMHO.
     
  11. paulajayne

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    Everything you have said indicates that you need to do the shielding mod.
     
  12. burlbark

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    The noise will only become worse with the wifi units failing right next to the GPS.
     
  13. CoolP

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    Thanks. I kind of figured that.
     
  14. CoolP

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    Update!

    This morning, right after posting here, I took the Phantom out to a the parking lot of the apartments I live in. Fired everything up, calibrated, got the rapid flashing lights, and BAM! locked into 8 satellites and full GPS mode! I placed it on the ground, gave it some throttle, and very cautiously lifted up to about 15 feet to the amazement of a young groundskeeper, and some local kids, who were curious about what the buzzing was all about.

    I let it hover for a couple of seconds, an it basically stayed in place, never letting the slight breeze take it more than a couple inches away. I was confident enough that I could take my eyes away from it to fire up the camera. It briefly dipped to 7, then back up to 8 satellites and remained in GPS lock mode. The little parking lot is kind of tight, and surrounded by trees and other structures, so I definitely didn't feel confident enough to "go crazy." I look it up about 2 more times, before being satisfied and calling it a day.

    So now that I have proven to myself that it can work in Haiti, I'm not as pressed to conduct the GPS cable shielding mod.

    Next steps: I will go back to the areas where satellite acquisition previously failed (they are not too far away), to see if my having locked into 8 satellites makes any difference. Port-au-Prince is a very crowded and hilly city, full of ravines, cell phone towers. There are high-tension wires, huge cinder block buildings, sloppily laid-down cabling of all sorts all over the place, and anything else that could make it a veritable electronic noise nightmare. Now I'm just hoping that low GPS sensitivity doesn't confine me to just a handful of ideal spots to shoot.

    My experiments continue!
     
  15. eyecon82

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    even the Phantom 2's have this problem.

    They fixed it in the version 2 though
     
  16. ToThePoint

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    Lucky for you it did a sat lock, but don't cry victory yet.
    You may have had enough sats and know how to see it on the iphone.
    I don't see anywhere mentioned the strength of the sats signal.
    On my app the signal strength goes from 0 to 100.
    All sats under 20 aren't showing up on the V+.
    If all sats give a signal around that value it is normal that when recording video it goes from 5 to 3 to 0 to 4.
    Because sats do move and there signal varies all the time.
    EMI weakens the sats signal even more.
    The conditions you mention are a schoolbook example of it.
    The only wise thing to do for you is to do the alu mod.
    You never shall improve poor conditions if you let it go on like that.
    Thats even seen in daily life in Haiti i guess.

    Someone mention you maybe have the V2 of the V+.
    That can be seen on what type of controler that came with the V+.

    Also i use a link that predicts sats on your location.
    http://satpredictor.navcomtech.com
    It doesn't mention the signal strength though.

    I tested the V+ with a external GPS module ( naza light ).
    That module was mounted some 15cm above the V+.
    It gave me more sats then the app on the tablet could detect.
    Due to circumstances i have to investigate that mod further, so mounting a naza light gps module on a V+ isn't something i can confirm to be working yet nor that it doesn't work.