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Wait time Acquire satellites

Discussion in 'Phantom FC40 Discussion' started by dirtdobber903, Apr 22, 2014.

  1. dirtdobber903

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    Hey guys from the point of battery plug in. What's the longest some of you have waited to obtain all green
     
  2. Norte23

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    Depends on your surroundings.....at home in the garden around houses & garages n stuff about a minute, but in an open space 15 - 20 seconds.

    Mark
     
  3. lostkiwi

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    In the back yard you can wait about 2 minutes. In an open field less than a minute.

    The backyard has high trees on one side and buildings on another. Very hard to get a clear view of the sky.
     
  4. EMCSQUAR

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    Location:
    N 44.895 W 93.354 Minnesota
    On my P1.5 usually 2mins - until I changed to upgrade board (why, who knows) but now 58 secs. On my E300 set-up 43 secs religiously w/2 sets of green flashes.
     
  5. dirtdobber903

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    I'll try again after work. Mines sat there for at least 4 min and nothing. Just 1 green and 2-4 reds. Partly cloudy day
     
  6. EMCSQUAR

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    Location:
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    Do an advance calibration first, then a compass cal, before your next flight.
     
  7. dirtdobber903

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    Well just got back in from 2nd flight. I didn't get chance to do a advance cal due to the hour I get ofF work. Powered her up and let it sit for 5 min and nothing. Did get down to 1 green and 1 red. I went ahead and did some nose out hover and it did that very well. Even pushed on it and it countered the move. Just can't reach the satellites I'm starting to miss my 350 qx
     
  8. mikeboruta

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    Location:
    Ouray, Colorado
    I am surrounded by mountains where I live. Sometimes it can take 5-10 minutes to get 6 satellites. And a couple times I couldn't get more than 5 (and I didn't fly). But, if I go 10 miles down the road where there is more open sky I can sometimes get 11+ within a minute.
     
  9. J.James

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    Tonight on my first flight It took about 3 minutes to get my all green flashes from the spot I usually take of from front of my house. and when it was time to change out the battery from the same spot were I landed with the return to home with in a few inches of were I started a few minutes before. Then when I plugged in the next battery it found them as soon as I plugged in the battery and it did its self check blinks and then when I was done with that flight and landed her at the 10 min mark I called it over and went in side and I still had all green lights when inside the house with no interruption of the greens. That is not to normal to get the all green when in side and when I do normally it takes a long time.
     
  10. Dalite

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    As long as you are flying from the same location, the GPS acquisition time should be short. I think that is considered a warm start

    If you have moved away from the last flying location, the GPS has to start from scratch - Cold start.

    On additional flights from the same location, the location is quickly verified - Hot start

    If you are using a GoPro, the electrical hash it generates can slow the acquisition process.

    You can actually take a GoPro that is powered up, no WiFi and not recording and pass it close to the shell after getting GPS lock and start getting red flashes again.

    Same deal if you pick up the Phantom and manually start the recording of video on the GoPro.

    Some builds are better shielded than others, and are less affected.

    The 2 Phantoms I have take anywhere from 30 seconds to 4 minutes, flying from the same location.

    On the other side of that coin, the US GPS grid maintained by the US Air Force keeps 31-32 birds in the sky, with the goal of 24 being always active. By their own projections, the grid can only guarantee 4 satellites to be in constant view from every location, at any given time. 3 or more satellites can provide 3D accuracy. The satellites are in orbit, around an earth that is slowly spinning. Distances vary by bird and attitude of the orbit.

    The first GPS units I played with cost hundreds of dollars and could take up to 15 minutes for their initial fix, or a new fix if started from a new location.

    Even 5 minutes to wait for good enough GPS accuracy to record both position lock and Home lock is quite an accomplishment.
     
  11. J.James

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    GPS satellites also make a full orbit every 12 hours. So they are moving pretty fast and just a few minutes can move pretty far causing on of them to be out of view or be hide some thing obstructing it. But if I'm remembering correctly most gps receivers remember were they last picked up a satellite from and the satellites also send date on its location and time corrections and the receiver can anticipate where it will be in the sky again when trying to ind it again.

    Its a pretty awesome thing that our birds can fully integrate and take advantage of the mighty accomplishment of putting up and maintaining the multi millions of $ worth of hardware flying around in space.
     
  12. Dalite

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    On a cold start (for sure) and possibly on a warm start, Almanac Data is received to give a synopsis of locations, predictions, etc).

    Since there are rarely any orbital maneuvers, and the rate of orbital decay is very minor, the Kepelarian elements are good for a long time as far as predicting position by time and location goes.

    http://www.amsat.org/amsat/keps/kepmodel.html

    There are also some phone apps that list the sats and visibility from your location.

    When you are trying to uplink to a Low Earth Orbiter with a 15 minute or less possible pass visibility, the Keps are crucial. The higher the orbit, the longer the pass.
     
  13. ElGuano

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    Depending on certain circumstances, the uBlox receiver on the GPS unit will take anywhere from a few seconds to 5+ minutes for full lock.

    Obviously, number of satellites in view makes a big difference. If you don't have 7+, you're not going to get to only green blinks.

    If you haven't flown in many days (or the backup battery on the GPS is dead), it will likely take a few minutes every time you plug in. The GPS receiver must have up to date almanac and ephemeris data downloaded directly from the satellites, and the transfer rate for this is SLOW. This is the main reason it'll take several minutes if you travel to a new location or don't fly for a month, and may have lock in 5 seconds if you're just changing out to a fresh battery after a flight.

    This doesn't affect the FC40 so much, but older NAZA-M modules have a longer hardwired warm-up time as well, so you may be sitting there waiting for a 2-minute warm-up that has nothing to do with GPS, but it adds significantly to pre-flight time.
     
  14. lostkiwi

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    Very good info on the workings of GPS here:
    http://en.wikipedia.org/wiki/GPS_signals

    Particularly notice the bit showing how many satellites are visible (and bear in mind its significantly speeded up). If you have a period of time where 6 satellites are the most it could possibly see and you are in a valley you could conceivably never get a blinking green light on its own.
     
  15. J.James

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    just out of curiosity when some one one says they had 10 or 12 or what ever number higher then 7 GPS sats locked in. How are they deriving the number over 7? Does the green light flash out a count or some thing? I only know about the counts from the amount of reds along with the green up to the 7+ count.
     
  16. ElGuano

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    iOSD will report an actual number of satellites acquired on your monitor/goggles.
     
  17. J.James

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    OH now I understand. seen the IOSD explained last night that looked sweet wish the FC40 had a way to add that.