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quick hook up to satilites

Discussion in 'Phantom FC40 Discussion' started by rogerdel, Jun 3, 2014.

  1. rogerdel

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    I took it out today for another flight and found after turning on transmitter then plug in batt that by the time i got to the back and check the lights already hpoked up.Is that possible to be that quick ?no warm up no time to aquire satilights?Flew rock solid! Also took some pics put in folder thentransfer to my device but can not find them? Nexus 7
     
  2. jerrymac12000

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    If it a nice day with the satilites just right it can be as little as 15 seconds. Other days, it can take up to 3 minutes.8
     
  3. jumanoc

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    First flight always take longer. (~2 minutes here)
    Sometimes I get only 10~ seconds for green lights in 2nd, 3th and other flights, after powering phantom.
     
  4. rogerdel

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    Ok thank you for your help.
     
  5. Ohary

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    Has to do with the number of satellites visible and their proximity to each other. The satellites move throughout the day. (I want to say they orbit the earth 2x a day). I also believe there are 32 satellites, so there are times when you can see as many as 11, and as few as 5 (based on my experience). Even less with tree canopy, structures.
     
  6. rogerdel

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    Ok thanks.Other question .I too.k some pics and used the app.then put them in the folder.clicked on to send to device but do not know where they went. I have my nexus 7 which is a android tablet .The pics downloaded but where do they go?
     
  7. darwin-t

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    I have an iPhone app called "GPS Plan". It shows the number of satellites above the horizon at any time. It also has a slider that you can move to show the number 12 hours in advance. It also includes a chart that shows the number. I have my minimum altitude set at 15 degrees above the horizon. There are a lot of times only 6 are above that altitude, and times when there are as few as 4.

    Lowering the altitude filter to 5 degrees shows more satellites, of course, but the lower the satellites are in the sky, the more likely that they will be blocked by buildings, trees, etc.
     
  8. ElGuano

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    All great info, but I think it's missing a big part of the equation, namely why you can get lock in less than less than 10 seconds sometimes, or take more than 3 minutes, on the same day in the same location:

    You'll notice that oftentimes you get satellite lock almost immediately if you plug in a new battery after flying your first battery.

    The reason this happens is because the GPS has its own button battery, for saving satellite data. When you first boot up a GPS, it has to download telemetry data directly from the satellites, that tell the GPS things like satellite health, orbital information, predicted positions in the next few days/weeks, clock corrections, etc. Some of this information is broadcast by each satellite for all satellites, some of it is satellite-specific. Some of the data is good for months, some of it only good for 30-minutes or so. And it's broadcast on a 30-second or 1-min interval.

    So, aside from the "standard" metrics of number of satellites visible overhead and signal strength, you also have this almanac and ephemeris data that has to be refreshed every few minutes or few days, or if you take a flight to a new region and boot up. If the info is stale, it needs to be re-downloaded. If you don't fly for a week, or your GPS battery is dead, it may take 2 minutes to initialize everything and get lock. If you change a battery between flights, or fly the next day, it may be much faster.

    All GPS units have to deal with this. Some internet-enabled GPS (like your phone) tend to be much faster because they can download this data online rather than through the slow satellite broadcasts (aGPS); and they also pull tricks like wifi/cellular triangulation to help as well.
     
  9. jerrymac12000

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    It also depends on the weather. If the quad is warm, the required internal temperature will be higher taking less time to aquire the satilites. If the weather is cold and the quad is also cold, the internal temperature will take longer to heat up. The same for a car engine. The car engine runs a little rough or the car may hesitate when cold. It runs better after it has warmed up.