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How many satellites does everyone get?

Discussion in 'General Discussion' started by Seedler, Apr 1, 2014.

  1. Seedler

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    Hi,

    I'm still wondering if there is an issue with my Phantom 1.1.1's gps. I know the phantom needs 6 or 7 (preferably 7) satellites to fly in gps. Any less than 6 and it drifts as if it is in atti mode. Why is this? I have found out that apparently you only need 4 gps satellites for a gps module to accurately fix its location. If the phantom could fly on 4 satellites this would be great.

    This site http://www.calsky.com/?GPS= allows you to see how many satellites should be visible from a location at different times. I did a test when it was predicting 11 satellites. The phantom only seen between 7 and 8 with a clear horizon in all directions. I then used my car gps from the exact same location, it seen all 11. If they are there why is the phantom not seeing them?

    Another issue I noticed is loosing satellites when changing direction. I could have 8 on the ground, climb to a 10 metre hover and drop to 5 or 6 for a few seconds. If I let it sit it will lock on again, but drop a few when I yaw to head off on a flight.

    I have checked to make sure the gps plug is secure.

    How many do the rest of you get? How can I improve my reception? Would a bigger patch antenna work? Would shielding work?

    The reason I'm asking is because I want to get the ground station, but at the minute I wouldn't be confident letting it head of on its own. Again the best number of satellites I have ever got was 8. Host times I fly in atti because I don't get a full lock.

    Please let some of you have some advice.

    Damien.

    P.S. I have never crashed my bird.
     
  2. ElGuano

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    It depends on a lot of things, including where you are, and as you know, time of day and year. Where I am, I get between 9 and 11 satellites regularly, pretty sure I get one fewer or more on occasion, but I honestly haven't paid much attention other than making sure it's "seven or more." The only way you can tell for sure if your Phantom is getting fewer than normal is to be flying two Phantoms side by side and comparing the satellite counts between them.

    There are some parks I fly at with tall trees that make it difficult to get more than 5 satellites on the ground.
     
    Joeg1937 likes this.
  3. ianwood

    ianwood Taco Wrangler
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    It depends on the sensitivity of the GPS receiver, atmospheric conditions and how many satellites are available LOS at that time. The more satellites you can lock in, the higher the precision of the fix simply because there is more timing data to estimate a position from. In Southern California, I will typically start out with 9 satellites and after a minute of flying at 50 to 100ft, I'll have up to 14.
     
  4. ericdes

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    The fluctuation of satelitte signal has prompted many to suggest this may be a reason for loss of control of the phantom.

    Get that ATTI switch working and get to know how to fly it!
     
  5. Seedler

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    ianwood, wow 14 satellites at 100ft, that's amazing. My satellite count doesn't seem to change no matter what altitude I'm at.

    ericdes, I can fly the phantom pretty well in atti. The reason I was asking about gps is I want to use the ipad ground station, so would need a good gps lock.

    Don't know anyone else with a phantom for comparison, but to me 7 or 8 seems low.

    Are there any flyers in Northern Ireland, or UK? What's your best satellite counts?

    Thanks,

    Damien.
     
  6. ianwood

    ianwood Taco Wrangler
    Staff Member

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    You should not, at least in theory, see any variation of satellite availability based on region with the exception of the poles. Satellites are equally distributed to provide as uniform coverage as possible. Below the poles under normal conditions, you should be able to get a minimum of 6 SVs and most often it should be 9 or 10. Anything less you can attribute to ground based obstruction, RF noise or atmospheric conditions.

    GPS performance including the number of locked satellites has much to do with the receiver's capabilities, the amount of sky visible down to the horizon, other RF signals and atmospheric conditions. Clouds, rain, ionic charging, etc. will all impact signal strength and timing.

    The best thing to do is wait. Depending on the last place and time you used it, the receiver needs to update its tracking information in order to locate each satellite and make useful calculations from them.
     
  7. Seedler

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    How that definitely makes me think there is a problem. I live in the country with clear views of the horizon in all directions, besides a few distant trees. I usually wait for a minute before launch after I get 7 satellites cos I read it can take 30 seconds for the gps satellites to transmit their data or something. Even after that I still loose satellites when I take off.

    I would love the confidence to go flying and not have to worry about this. The only time I get all green flashes is around 12 noon. a few hours either side of that and I get one red flash at best.

    Don't know what to do next. Would a bigger antenna help, or does anyone think there is something wrong with my gps module?

    Thanks,

    Damien.
     
  8. Cr8tive_leo

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    7 indoors, 9-11 outdoors.
     
  9. EMCSQUAR

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    Before investing into anything, get someone else w/Phantom out there & compare. (if possible) and see if it's your GPS or the location. Also how are you measuring # of sats? Are you using IOSD mini?
     
  10. thongbong

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    max i've had is 14
     
  11. ianwood

    ianwood Taco Wrangler
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    Or just use your phone. If you have an Android phone that is. This is very useful for many GPS related functions: https://play.google.com/store/apps/deta ... gpsstatus2. If you have an iPhone, well, you can curse Apple for not seeing a need to let you have access to GPS technical data on your phone.
     
  12. Seedler

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    These numbers are making me jealous :)

    EMCSQUAR I'm using the iosd mini. I don't think its interference because my car satnav can lock onto a lot more, so I would expect local interference would effect it as well
     
  13. tupes

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    I usually lock 12 even before I take off and usually get 1 or 2 more while in the air.
     
  14. EMCSQUAR

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    You might want to pop the lid and check connections on GPS puck and also make sure sheilding is tight. I had cable from GPS to Naza come loose after a crash. That would be my next things to check.
     
  15. dataway

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    I usually get 12 also on a routine basis.
     
  16. wkf94025

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    +1
    Mountain View thumps Cupertino again!
     
  17. Seedler

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    EMCSQUAR I think your rite, I might check the ceramic antenna as well, in case there are any cracks.

    Hope its something simple.

    Do I need to be careful of static when working with gps module?

    Thanks,

    Damien.
     
  18. The Editor

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    Try this ---> http://satpredictor.navcomtech.com/

    It should give you an indication on how many sats you can expect to see.
     
  19. EMCSQUAR

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    If anything handle GPS & compass cable with care, those ends are pretty small and GPS end is just 4 soldered connections.
     
  20. nwillitts

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    i have p 1.1.1 with iosd mini and i consistently get 11 sats.