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Installing DJI A2 Flight control on Phantom 2 - GPS accuracy

Discussion in 'Phantom 2 Discussion' started by heuteheute, Jun 4, 2014.

  1. heuteheute

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    Hello,

    I want the Phantom 2 to fly accurate waypoints using the 2.4 Ghz datalink.

    Anyhow I found that the GPS Data is not very accurate in this experiment:

    I did read the GPS coordinates out of the pc groundstation software (2.4Ghz datalink) when placing the Phantom 2 on the prefered waypoints manually.
    Later, when I did let it fly manually, there was always a displacement in x and y by one to two meters or even more.
    Height was also not very accurate (plus minus 30 cm )

    Then I took an app on my mobile phone (high end), that i did use to read GPS data on each waypoint, before, too.
    These where fundamentally different from the GPS data the Phantom 2 generates!

    I want a real accurate approach of the waypoints. Question: Can I install the DJI A2 on the Phantom 2 to acchieve this?

    Will the read out waypoints be more accurate this time, and also have a better accuracy when repetively approaching each waypoint?

    Ciao
     
  2. Xrover

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    Re: Installing DJI A2 Flight control on Phantom 2 - GPS accu

    Doesn't the A2 cost Twice as much as the Phantom itself?
    As far as I know, you cannot replace the NazaMv2 on the Phantom with any other controller.
     
  3. OI Photography

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    Re: Installing DJI A2 Flight control on Phantom 2 - GPS accu

    The A2 system won't fit inside a Phantom, mainly due to the size of the IMU. You would also have to figure out how to mount the GPS.
     
  4. ElGuano

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    Re: Installing DJI A2 Flight control on Phantom 2 - GPS accu

    Yeah, OI is right. Based on size alone, it's not going to happen. But if someone is going to step up and prove me wrong, I'll be thrilled, I would love to see that project.

    Technically, you can replace the Phantom Naza in the P2 with anything. There are some people running Naza-M V2s in their P2s to bypass the smart battery. You do have to make some accommodations for the custom programming affecting the mainboard (namely, a new status LED module).
     
  5. Xrover

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    Re: Installing DJI A2 Flight control on Phantom 2 - GPS accu

    I thought the P2's already come with Naza M V2's
     
  6. tom3holer

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    Re: Installing DJI A2 Flight control on Phantom 2 - GPS accu

    The P2 comes with a version of the Naza but no, it is not a Naza-M V2.

    Tom
     
  7. Xrover

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  8. ElGuano

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    Re: Installing DJI A2 Flight control on Phantom 2 - GPS accu

    The Phantom Naza is indeed based on the Naza-M V2, but is fundamentally different to the point where they should be considered incompatible.

    You cannot use your Phantom Naza in another MR unless you move the battery and mainboard over as well, for instance. The Phantom Naza has its own dedicated Assistant and cannot use the Naza-M V2 Assistant or use Naza-M V2 firmware. The LED is locked, it's the only FC that supports the no-fly zones (for now), and F2 and possibly other channels seem to work differently as well. This is all pretty well documented at this point.

    Naza-M v2: [​IMG]

    Phantom 2 Naza: [​IMG]
     
  9. heuteheute

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    Re: Installing DJI A2 Flight control on Phantom 2 - GPS accu

    Hello,

    thanks for the replies.

    I do not care about the costs on the phantom 2 and the A2. My objective is accurate waypoints, and as i mentioned,
    the gps data i did read was fundamentally different from what i did read out of the smartphone and again the phantom 2 flew to the programmed waypoints, but with 2 or even 3 meters next to them!!

    Can i not just plug the A2 inside and take the NAza out?
    Why even program something? idindnt understand that part...

    plus, why is the system so inaccurate after all...
     
  10. OI Photography

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    Re: Installing DJI A2 Flight control on Phantom 2 - GPS accu

    No, again, the A2 system will not fit inside a Phantom. You would have to mount the A2 flight controller and the A2 IMU as well as the A2 GPS and the A2 LED module.

    The NAZA uses less precise (and smaller and less expensive) sensors than the Wookong or A2.
     
  11. ElGuano

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    Re: Installing DJI A2 Flight control on Phantom 2 - GPS accu

    The position hold for NAZA GPS is ~2.5m horizontal, so it can drift around that much in any direction and still be considered on target. 2-3m accuracy for a pure GPS unit is exceptionally good actually. A GPS unit, especially one at rest, is generally only accurate to about 15m. A smartphone or high-precision GPS unit is potentially able to leverage augmented GPS, wifi/cell triangulation, WAAS, RTK, etc. to dramatically enhance accuracy, but such systems are more expensive and require additional equipment.

    [​IMG]

    The A2 isn't a drop-in replacement for the NAZA. It's larger, and separates the IMU into a discrete, isolated unit from the rest of the controller. All of the connectors are intended for larger, external mounting as well. There simply isn't enough space in the Phantom for the A2.

    If you really need the added precision offered by the A2, you really want to look at a larger platform than the Phantom. Some people have stuffed the A2 into a 450mm frame, but even that is a really tight squeeze!
     
  12. macheung

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    Re: Installing DJI A2 Flight control on Phantom 2 - GPS accu

    There had been people successfully installing a regular naza m v2 in the phantom 2. Everything works except for the underarm led lights. You get no no fly zone, can use any battery. Check rc groups p2 owner thread for details.
     
  13. heuteheute

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    Re: Installing DJI A2 Flight control on Phantom 2 - GPS accu

    Thanks a lot for the help!

    I dont mind making holes to the chassis or simply mounting the A2 stuff outside, e.g. below the phantom 2 and then wiring everything accordingly. the question was only if techically speaking, the phantom 2 would allow me to do this.

    i will give it a try once it arrives!
     
  14. rilot

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    Re: Installing DJI A2 Flight control on Phantom 2 - GPS accu

    I'm sure it will work, but I don't see the point. Buy a larger platform.

    I fly an A2 by the way in my S800 EVO.
     
  15. sar104

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    Re: Installing DJI A2 Flight control on Phantom 2 - GPS accu

    It may work, but none of these solutions will provide the horizontal accuracy that the OP wants, so it really is a completely pointless exercise.
     
  16. heuteheute

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    Re: Installing DJI A2 Flight control on Phantom 2 - GPS accu

    Hello Rilot,

    when you fly the A2 on the s800 EVO, what is your horizontal accuracy? Do you have the datalink?

    If so, this is the experiment i am trying to conduct:

    1. you place the evo on certain waypoints of your choice, manually, and read out the gps coordinates on the computer display using the datalink.

    on each waypoint you choose, you put a mark into the ground.

    2. next, you enter the waypoints and the coordinates you did read out of the datalink software, into it.
    then you let it fly these waypoints. of course, the height will be set low, e.g. 2 meter, so you can compare.

    the question is: how accurately will these waypoints be targeted when the datalink software guides it to them?

    so the general question is, how accurately the gps coordinates can be repetedly approached and read out in the first place.
     
  17. ElGuano

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    Re: Installing DJI A2 Flight control on Phantom 2 - GPS accu

    I think this should be your main concern. Hover altitude is normally +/- 0.8m relative, which is pretty darned good. But absolute altitude is not exceptionally accurate because of variations in barometric pressure and inaccuracies with GPS altitude readings. You may have a 1-2m altitude reading swing while sitting on the ground without even arming the motors, and once in the air it's not uncommon for reported altitude to drift well over several meters. Setting waypoints with 2m clearance to the ground is really asking for trouble!
     
  18. heuteheute

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    Re: Installing DJI A2 Flight control on Phantom 2 - GPS accu

    Hello,
    thanks for the advice,
    the tests i conducted worked fine with 2meters of altitude, but of course it was with the Phantom 2.

    Anyhow, i have two opions here. One said the A2 does not come with better horizontal accuracy,
    and on the DJI website it sais it was one of the most accurate systems.

    So if somebody knows something or wants to do the experiment I described above, please let me know :)
     
  19. riblit

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    Re: Installing DJI A2 Flight control on Phantom 2 - GPS accu

    GPSr accuracy is dependent on a range of factors including the time of day, position of the satellite constellation you are using, number of satellites, receiver location, reflections etc. All of these can combine to give a high DOP.
    You need a GPSr that gives you a number for HDOP at least. The lower the number the better the horizontal accuracy.

    Don't use a smartphone, buy a real GPSr, turn WAAS off unless you are sure the module you are using in the Phantom uses it ( I doubt it does ) and you are in an area that supports WAAS, and use it to check your positions.

    I have been using the GPS system for over 10 years and can tell you that the accuracy varies between 1 and 10 metres here in Eastern Aust. Smartphones can be as far as 200 metres out as they don't have an efficient antenna and switch to cell tower triangulation if they lose signal. Cell tower triangulation is extremely inaccurate.
     
  20. ElGuano

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    Re: Installing DJI A2 Flight control on Phantom 2 - GPS accu

    Yep, no WAAS on the Phantom implementation afaik.