Lets talk about the DUAL gps claim..

Discussion in 'Mavic Pro Discussions' started by J3ffrey, Oct 23, 2016.

  1. J3ffrey

    J3ffrey Active Member

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    One problem I had with a previous quad was how much it dropped GPS while flying.... is this dual gps claim in the videos something that will make fly away's a thing of the past??
     
  2. LuvMyTJ

    LuvMyTJ Administrator
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    It uses GPS & GLONASS (Russian system) like the P3A/P and the P4. So it has more satellites to lock onto.
    Never rely only on GPS when flying an sUAS. You should know how to fly in ATTI or without the help of GPS. Any cheap non-fps quad is a great trainer.
     
  3. thefrisbee995

    thefrisbee995 Well-Known Member

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    It uses GPS and GLONASS. Many phones use this so that they can be more accurately track you on a map. If the Mavic uses this too, it should be a pretty sound claim, think about it, more satellites will be available so if you drop one, you should have many more you can connect to, meaning it should be reliable and it means that potentially the Mavic will be more likely to be connected to more satellites at any given time making the positioning more accurate (more sources feeding into one destination means a better average can be made). Hope that's clear aha
     
  4. J3ffrey

    J3ffrey Active Member

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    All I care about is the thing doesn't fly away on me like my other did... it flashed "GPS lost" and for some reason the controller disconnected and I watched it go into the ocean... (was not a DJI)..
     
  5. thefrisbee995

    thefrisbee995 Well-Known Member

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    That could have happened due to a number of potential issues but if GPS was in that case the issue, the Mavic should be a lot less likely (nothing is guaranteed!) to run away.
     
  6. Dirty Bird

    Dirty Bird New Member

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    In 1000+ flights of DJI drones ranging from the Vision+ to the P4 I have never lost GPS signal during a mission. I've never experienced a fly away either.

     
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  7. J3ffrey

    J3ffrey Active Member

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    Glad to hear that. I got a replacement of the same quad and it had the same problem, dumped it on ebay the next day.

    I've been all over the data and argued it pretty strongly with the company, getting into it so deep that I had to explain what some of the logs meant to their own tech guys/girls. They always came back with "well the gps in your phone doesn't always have a 100% accurate lock either" - my answer was "Well, the logs in my phone kind of says it does...but even if it didn't THIS ISNT A PHONE!"

    The main issue was that when this quad lost gps it would also not be able to hover, it would start to move in one direction... it wouldn't hold altitude either.. .so all of the flyaways seem to show the same thing. Loses GPS, controller locks up and it shoots off in one direction like a rocket till it hits the ground.

    I'm hoping that because this one has "cameras" it can hold position even without GPS or at the very least hold altitude.
     
  8. Dirty Bird

    Dirty Bird New Member

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    I don't know the brand or model of your previous quad, but the Mavic is a 5th generation product. Not that it is impossible to fail but DJI quads have proven themselves extremely reliable. I have 6...well actually 5 at the moment since I sold my P4 to get the Mavic. All have proven quite reliable.

     
  9. The Editor

    The Editor Well-Known Member

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    Nothing can make fly-aways a thing of the past or an impossibility.
    What dual GPS, dual IMU and dual Magnetometer (compass) can give you is redundancy so that potentially things are more reliable since if one fails you have a back up.
    Although dual GPS is not really to do with preventing fly-aways, it is simply used for better positional accuracy.
    Now for the price point DJI cannot give true redundancy which requires three of each module. That way a comparison can be made between each of the three and if one starts giving differing data to the other two it can be switched out the system by the flight controller and all is well. With only having two of each sensor, if one gives some strange data there is no real way of knowing which of the two is feeding the erroneous information to the flight controller. So, no, dual modules DOES NOT mean no more fly-aways. However, DJI would have written in algorithms to the flight controller that will look at the data coming from the accelerometers and gyros whilst comparing the attitude of the aircraft with correlation to stick input. If the two do not agree, the erroneous IMU would be ignored.

    Having said that, the Mavic (like the Inspire and P4) utilises both the Navstar constellation (GPS) and Glonass to give a better HDOP/VDOP accuracy and thus better positional hold.
    Altitude information can still be utter rubbish utilising GPS data which is why the barometer is used for altitude hold. The solid state barometers used have a resolution of around 10cm so are pretty accurate (but can still fail)
    To date, no manufacturer (including DJI) have built a platform that has no single point of failure - they will come but as yet nobody has achieved it (and certainly impossible on a quad)!
     
    #9 The Editor, Oct 23, 2016
    Last edited: Oct 23, 2016
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  10. Ed Windham

    Ed Windham Well-Known Member

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    Editor. No hobby class MR will even approach the level of military craft. Even they crash. There is nothing that is 100% reliable. If you fly it you will crash it as some time.
     
  11. m0j0

    m0j0 Well-Known Member

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    300 miles on my P3p.. only one time did it drop GPS during a flight. DJI has been using both nav and Glonass for a while. Forget about flyaways they are rare.
     
  12. m0j0

    m0j0 Well-Known Member

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    Not likely, I started with the P3p and never had anything close to a significant problem..
     
  13. Mako79

    Mako79 Well-Known Member

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    If your P3/P4 switches to ATTI mode when you are in an open sky, that's the redundancy system preventing the fly-away. This happens if you have poorly primed your compass or if your compass is faulty or if you take off from your car.
     
  14. The Editor

    The Editor Well-Known Member

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    Stuck accelerometers can still cause a flyaway and have nothing to do with GPS or compass.
     
  15. The Editor

    The Editor Well-Known Member

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    Hi Ed,

    Wasn't suggesting that for one minute but the OP asked whether dual GPS would prevent or put an end to fly-aways to which the answer is obviously no. Navstar and Glonass reception is purely meant as an aid to positional accuracy.:)

    Although the A3 comes close to TMR we will see multiple flight controllers emerging in the future which will give the sought after no single point of failure.
     
  16. Pablo

    Pablo Well-Known Member

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    It's a dual compass that's new and should prevent the flyaways, not the dual GPS (That's been around for a while)
     
  17. 4wd

    4wd Well-Known Member

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    With the Vision Plus on GPS only it was common to be informed your were going in and out of ATTI mode due to less than six satellites, if any trees or buildings covered even part of the sky it might never find 6.
    Using glonass too there is usually at least 12 and often 17 or more.
     
  18. Mako79

    Mako79 Well-Known Member

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    Yeah. But a stuck gyro accelerometer won't let you take off.
     
  19. LivinLarge

    LivinLarge Member

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    But it could get stuck in flight.
     
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  20. LivinLarge

    LivinLarge Member

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    When you have two compass sensors which do not agree, how do you know which is correct?
     
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