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How many GPS satellites?

Discussion in 'Phantom 2 Discussion' started by duccio, Jul 6, 2014.

  1. duccio

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    Hi,

    I own a Phantom 2 with IOSD mini and AVL58 video transmitter.

    I'm in Italy, I tried P2 in a country open space and I got always (also waiting more than 5 minutes) 6 maximum 7 GPS sats.

    I viewed all videos on YouTube showing P2 and IOSD mini and always see 10/11 and 12 satellites.

    What is the problem with my P2? Suggestions?

    Thanks,

    Duccio
     
  2. Diesel31

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    As long as you're getting 7 satellites, you should have nothing to worry about. Often, I 'll wait for 5-7 minutes an still only get 5-6 satellites. I'll pop it up and hover for a few seconds, then i'll get 7-8 satellites, than upwards to 11-12 satellites.
     
  3. xgeek

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    It depends on the time of day and your current location. I sometimes see as low as 5 in which case I would never fly. Remember the GPS satellites are continuously moving in orbit, so best to check with an app like GPS plan on the iPhone or on a site like this to see how many GPS satellites will be visible before you fly:-
    http://satpredictor.navcomtech.com
     
  4. duccio

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    Hi Diesel31, thanks for your reply!

    Half of battery has gone waiting for more than 7 satellites (5/6 sats in less than a minute)... So I decided to fly anyway (the lights on P2 was flashing green) and during the flight I got always 6/7 satellites, no more. This was my first flight, so max height was 80 meters :)

    Maybe my P2 GPS antenna is wrong?

    Thanks,

    Duccio
     
  5. duccio

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    xgeek, wow!

    I checked at satpredictor for my time, location and elevation mask (default 10 degrees, maybe). I flew at 16:10 and 16.30 (with the second battery pack) and sats visible were 8 for the first flight (on P2 only 7) and 7 for the second flight (on P2 6/7)…

    Is it right my interpretation to the sat predictor graph (attached)?

    Thanks,

    D.
     

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  6. Kotik

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    Location:
    Weston-super-Mare, UK
    I am in a similar situation: lots of trees where I fly so poor GPS reception at ground level. The solution is to wait till you have 5 or 6 satellites then take off in Atti mode and hover 50 or 60 feet up for a minute or so. When you see 7 or more satellites switch to GPS mode. The phantom records its position at take-off even if you have less than 7 satellites, but the fewer the less accurate the GPS fix. You could also try reset your home point when more satellites are visible by rapidly flicking the left switch 6 times.
     
  7. FASTFJR

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    I'll get 6 right within 15 seconds, followed by 7,8,9, 10-12 within the next 30-35 seconds. If your waiting any longer than 2 minutes and your in the open shut down the PS and restart it. I've had this happen 2-3 times, After 2-3 minutes its still showing zero. I'll do a shut down and restart and bam.....I've got 12
     
  8. KBurn

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    I travel a lot to new locations. In the last month, my P2 has been to Iceland, Norway, Korea, Malaysia, Singapore, Estonia, London and I'm now in Cappadocia Turkey...

    Each time I move to a new location which requires me to do a compass calibration (further than 30km away), I find that it takes a while. The first flight is usually a long wait and at times I need to take off and hover (if not windy) for more sats the show up. However, following flights seem to get progressively better and the cold start wait time is shorter. If I move again (even if just miles away by car to a new site that requires me to calibrate), it shows far less sats again.

    One thing to note, taking off even just at a low height to hover without GPS should only be done in very slight or no wind conditions! Don't forget. A sudden gust will send your P2 flying... and if you have no flying experience, it could go into someone or crash into something.... just saying ;)
     
  9. FedeVision

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  10. scratch009

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    So you find this solution of putting alu foil below the gps antenna also working for a Phantom 2 (not vision). I live in Belgium. Usually will get 7 sats but can take a while. 8 or 9 is rare. If this trick would improve signal for p2 also I'd consider it. I thought this was done to eliminate wifi interference for the Vision+ model.
     
  11. FedeVision

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    I used aluminium tape, the one with adhesive on one side, used by air conditioner and refrigeration technitians, but seems aluminium foil will work fine too. This trick worth the try, if you see no difference, it's easy to remove, but I'm sure this can help a lot of people.
     

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  12. OI Photography

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    Thanks!! I've been planning to do this mod as well and wasn't sure what material to use, the aluminum tape makes perfect sense :) Did you add one layer or two?


    I've seen this trick used effectively on P1's before the P2 was released, but it may be of even more benefit in later models due to the increased RF noise level they have inside.
     
  13. ianwood

    ianwood Taco Wrangler
    Staff Member

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    Curious about this aluminum mod. Not sure how much it is going to help but curious.

    Everyone should keep in mind one of the major factors in how long it takes to acquire satellites: the age and relevance of the ephemeris and almanac data. This is based on the last time and location where you last used the Phantom. If I fly 45 minutes after my previous flight and I am not far (couple of miles) from my previous location, the GPS should pick up the satellites pretty quickly using the cached data. If it's a week later and/or I am many miles from the previous location, the data is too old and/or inaccurate and it will need to be refreshed.
     
  14. OI Photography

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    Very true, and the other factor is the fact the battery on the GPS module that lets it cache that info will eventually die and cause you to sit through full acquisition at every boot up. One of the replacement GPS boards I ordered already had a dead battery when it arrived.
     
  15. FedeVision

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    I tested with one layer, good enough for me.
    GL.
     
  16. duccio

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    I'm using aluminum tape and paper tape for isolation, finally I got 12 GPS satellites, really happy! Thanks for suggestions ;-)
     

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  17. FedeVision

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    Good to know, enjoy your flights!
     
  18. Helveticus

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    Do not forget to also shield the cable that goes to the GPS antenna with some aluminum tape ;)
     
  19. Original poster

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    Both of my flights today I was getting 10.

    I do wait about a minute though and have the iOSD which tells me how many sats I have picked up, the iOSD is worth it for this feature alone IMO.
     
  20. Kelso Kubat

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    I wait for initial warmup sequence to go through. After getting both sequences of rapid greens and plus 6 I do compass cal. After that it always has 7-9 and a minute into most flights I have at least 10. As time goes on you lock more. Lock 6 or 7 at compass cal is what I wait for. And double green sequences