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The Phantom has a very poor quality GPS!

Discussion in 'General Discussion' started by FrankB, Jun 24, 2013.

  1. FrankB

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    I live in the mountainous and heavily treed West Coast of Canada and am finding that the Phantom just can't lock onto a good GPS signal unless you're right out in the open on a big field with no mountains or trees nearby.

    If you take off without having a good GPS Home location, your Phantom could fly away if something goes wrong, or do something else unexpected, like fly into nearby trees.

    All modern GPS's today use the fast SiRF chip set, which is able to pick up very low signal levels and, in the case of the SiRFstarV, signals from all available satellite networks- the original GPS system, the Russian GLONASS system, the European Galileo system, and others.

    If DJI is listening, they should take heed and make sure that the next generation of Phantoms have a modern, sensitive, and fast GPS.
     
  2. Darrell1

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    I have never had any issues. I wonder if something is wrong with yours. Granted, I'm in the Midwest, but I have flown around large buildings, under trees, etc.

    If you have a poor signal, it will not fly away. I believe it just a witches to atti mode.
     
  3. FrankB

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    No, it works fine out in the open- but not if I'm surrounded by 75 metre high Douglas Fir trees in a tight little glaciated valley. But even in that setting, my iPhone GPS and normal Garmin 76CSx work fine- so it is the Phantom's GPS that is at fault.

    I'm worried that if it doesn't have a good reference as to where its Home location is, it will set down just about anywhere if it has to go into "Return to Home (RTH)" mode.
     
  4. Roadkilt

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    I'm on the west coast of bc and always get a full signal, but it sometimes takes a bit of a wait.
     
  5. auck

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    I know for a fact iPhones does not have a real GPS unit built in. It uses cell tower signals to triangulate your position Don't know about the garmon though.
     
  6. Smort78

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    Then you have to check your facts - since iPhone 3G the iPhone have had a real GPS reciever.
    The Garmin 76CSX is a dedicated (and very accurate) GPS reciever.
     
  7. GearLoose

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    FrankB... I wonder if your Phantom's GPS is faulty? I also live in a narrow forested valley with 75 metre fir trees almost overhanging our cabin. Because of the surrounding mountains we have no cell signal, no broadcast TV and very poor radio. I also use a Garmin CSX and though it is much quicker to lock onto a position, I haven't noticed any particular problem with my Phantom, other than being rather slow to get a firm GPS lock.

    I regularly practice flying about 75 feet from the tree line. On the other side of me, the valley is open for about 250 metres -- then a forested hill about 50 metres high, and then about a kilometer away, a very high ridge.

    When flying here, I occasionally see a single red blinking light between the green, especially when making fast tight turns. So far, however, the all-green "good GPS" light has been quite consistent.
     
  8. martcerv

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    I think relying on GPS in such a location is bound to cause you trouble, the GPS receiver probably isnt the best out their but I have found it quite good and I know where to use it and where not to.

    In your location even if you had a great signal the odds of RTF working properly without hitting a large tree on the way back would be pretty lucky. In such locations fly only with good line of sight in atti modes as GPS will be less accurate causing switching between GPS and Atti mode when signal is low, The phantom will have a smaller tolerance for GPS then other devices as it wouldnt want to have a 10m fix but would need something inside a few meters to work properly. Your better off sticking to atti mode so you know your always in it rather then assuming your in GPS and it switched to atti causing you to drift into one of the big trees that also blocked your GPS.

    In your location if you did a proper GPS test you will see the accuracy will be down greatly with any GPS device so the last thing you want is to rely on auto pilot to work with maybe a 10-20m radius in a tricky location where it doesnt have that much room for error. I think you are asking too much of the GPS mode and your particular location is the last place I would ever fly in GPS mode unless above all the trees.
     
  9. GearLoose

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    Martcerv, you just clarified a very puzzling question I've had about flying my Phantom in GPS mode. Yesterday for example, I was getting occasional red flashes while flying in GPS -- and when I sent it close to a stand of very tall trees (into an area shaped like a "bay"), the Phantom drifted dangerously close to the trees. I didn't realize that it must have switched to ATTI, as you described. In fact, now that I look back on my tragic history of crashes into trees, perhaps I can blame GPS-error for some of them instead of pilot error?
     
  10. FrankB

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    Actually, the iPhone does have a GPS chip set- but you're right, it also uses cell tower triangulation to improve the accuracy of its position.

    Here is a reference:http://gps.about.com/od/gpsproductoverview/a/How-To-Use-iPhone-GPS.htm
     
  11. Alaska-Flyer

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    All,
    I have seen quite a few posts regarding the Phantom GPS quality.
    In my day job I work as a mapping professional working with survey grade GPS systems.

    Whether you are using a professional grade GPS or consumer grade GPS like in the phantom, the same rules apply.
    You must have a clear view of the sky in order to get accurate GPS positions. Think of it as line of sight.
    Obstacles such as Hills, Mountains, trees, etc... that block your view of the horizon will greatly degrade the GPS signal quality.
    Also flying near buildings or large metal or flat surface structures will not only block your view of the sky but also create a condition known as "multi-path", where the GPS signal rebounds off the vertical structure face which creates a timing lag in the signal prior to be received by the GPS sensor which can create large errors in the calculated position.
    There are several other conditions that can impact GPS reception but the above covers the primary ones.

    Simple rule of thumb when flying the Phantom in GPS mode is "the more sky you can see the better"

    Happy flying :D