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HELP!! Incorrect Distance display and compass direction.

Discussion in 'Phantom 2 Vision + Discussion' started by dksoundz, Oct 16, 2014.

  1. dksoundz

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    Hi everybody,

    I'm hoping someone will be able to help who may have had the same problem. I flew today and for some reason the distance display on the app was saying the bird was around 200 feet away from me when in actual fact it was directly above me. Also the compass was a bit hit and miss with regards to what way the bird was pointing. I calibrate the compass every time I fly so i can't imagine that would be the problem would it? Also it may be worth mentioning I have never had a crash either. This is the first time this has happened. Can anybody help please? Has anyone ever had the same problem? Many thanks!
     
  2. Panamon Creel

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    did it correct itself when you moved the Phantom so it's not directly above you?
     
  3. dksoundz

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    To be completely honest with you I can't actually remember. I really hope this was just a one off occasion. All i know is when I lose sight of the phantom by eye I rely on the compass to get me back home or for am accurate reading of my whereabouts. Do you think maybe this could be a one off? I cant see how though seeing as I calibrated the compass in a big open field next to the sea front.
     
  4. UKFlyer

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    Your compass on your smartphone will be out, is it android?
     
  5. dksoundz

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    Yes I am on android, using my Samsung galaxy s4. Do you think this could be the problem?
     
  6. Mori55

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    I had a Asus memo pad that I could never get the distance right. I returned it and got a iPad mini , never had a problem after that.
    It worked fine on my iPhone too. I bought the Asus because it was cheaper than the mini. Just couldn't get to show the correct distance. The mini is wifi only.
     
  7. dksoundz

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    Thank you very much for your information, it is reassuring to say the least. I have flown around 20 times now and never had an issue until today however thinking about it I have never enabled GPS on my android. Do you think I would get more reliable results if I were to do so? Also would the fact of the compass being out on my phone affect the distance display? Failing all of that I may look to invest something along the lines of what you have done.
     
  8. Meta4

    Meta4 Moderator
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    Also look into calibrating your phone's compass - google for info.

    Probably not but why do you do it every flight?
    DJI never recommended that.
    Once you have a good calibration, wouldn't it be better to keep it instead of introducing the potential to get a bad one?
     
  9. RedBaron

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    Calibrating every time doesn't hurt anything and gives you assurance everything is okay. If you had it next to any magnetic sources including speakers, things can get screwed up and you wouldn't know it. Also look at the "Where is My Phantom" in the Vision app to see if it corresponds to your location.
     
  10. RedBaron

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    The manual does not say "Do not calibrate after flight". What it does say is "Recalibrate when flying in a different location since last flight" and that "regular calibration is required for optimum performance".
     
  11. dksoundz

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    Well thanks very much for everybody's input I really appreciate it. I'm still at a bit of a loss as to what the problem is...I guess I tend to be a little OCD with the calibration thing but I can see where you are coming from if I interfere with a good calibration it could cause a worse off one. Weather permitting I shall fly this afternoon and try a couple of things, reboot my phone so nothing at all is running in the background, ensure gps is enabled on my phone and calibrate in a good location. I'll report back with results!
     
  12. dksoundz

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    Also just thinking about it.....on this particular occasion the transmitter was hanging from my neck with my phone in the holder during calibration....could my phone have caused this problem being to close to the GPS module while calibrating?
     
  13. Meta4

    Meta4 Moderator
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    From the manual ... DO NOT carry ferromagnetic materials with you during calibration such as keys and cellular phones
     
  14. Meta4

    Meta4 Moderator
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    The manual is very conservative with huge safety margins
    eg the manual says ..
    Do not use the aircraft in severe weather conditions. These include wind speed exceeding category 4.
    A Beaufort force 4 wind is a moderate breeze of 13–17 mph.
    The Phantom can easily fly at 30+ miles/hr and and manage a Force 6 wind (25–30 mph and 3x the strength of Force 4).
    That's how conservative the manual is.
    Calibration every time is completely unnecessary.
    If it was DJI would recommend it.

    Calibration every flight is for people that press the elevator button multiple times to make the elevator come faster.
    Superstition gives people an assurance that everything is OK.
     
  15. Mori55

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    If you know anyone with a iPhone , try that and serif the distance is right
     
  16. BlackTracer

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    I have looked in the manual and I cannot find anywhere where they recommend against it. They mention when it is required but nothing about calibrating every flight not being recommended. Are you guys making this **** up?
     
  17. Meta4

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    The manual says nothing about calibrating every flight (recommended or not).
    If DJI thought it was important they would have said so, particularly as they are very conservative.
    Since there is no recommendation, anyone that decides to do it is making up their own rituals and unless they have a reasonable scientific reason it is superstition.
     
  18. pb7424

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    Don't forget that the Vision app gives you a warning message if a compass calibration is required.
     
  19. dksoundz

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    Hi everyone,

    Just a quick update...firstly your response has been great and I really appreciate it. Just wanted to let everyone know just came back from a flight and on this occasion there were no problems with distance display or compass heading at all...it seems as though it was just a one off thank god! Still cannot answer as to why this problem occurred but I'm glad its not permanent! Thanks again :)
     
  20. Panamon Creel

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    The good old Phantom compass cali debate a never ending story :)
    What is the compass calibration for? I´ve seen DJI answer that question in their forum with: "compass calibration make corrections for magnetic interference around the magnetic compass in 3-D space. During flight, we have good algorithm to eliminate the influence of compass interference. so if the magnetic sensor north is off by a few degrees, it maybe have a J-hook when hold, but after a feel time flight, it will keep stable."
    and
    " the declination correction is running real time during flight when there is enough gps, no matter which flight mode"

    So the calibration dance is there to remove inaccuracies caused by magnetic & ferromagnetic materials that are around the compass and mounted to the Phantom, e.g. motors, servos, screws,...etc.
    Therefore if you add or remove something magnetic/ferromagnetic to the Phantom ----> CALIBRATE
    If you change to a location where the declination is a lot different than the last calibration location and you get J-hooks when holding in a position ---> FLY so it can "learn" since declination cannot be " learned" by the calibration

    One thing they did not say is if it also learns Inclination differences, likely not therefore better to do a compass calibration if you changed to a location where the inclination is a lot different to your last calibration location. Inclination will have an effect in the 3D world of the compass sensor and can be calibrated for.
    Another influence could be Earth magnetic field strength change in different locations.
    There are apps out there that give info about the Declination, Inclination and field strength while at a specific location and can be used to check for differences to the last known calibration location.

    What else, well the human error factor and that is bringing a strong magnetic field close to the compass module and accidentally magnetizing it. Usually that would give a compass error after power-up.

    So calibrate every time if you like, myself I will just do it if I think that the location is different enough from my last location I calibrated at.