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Advice about compass calibraton

Discussion in 'Pro/Adv Discussion' started by lotusteve, Nov 11, 2015.

  1. lotusteve

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    i have done quite a few flights from around the same location and every time i fly i allways check the sensors and the compass is around 1500, sunday i went to a new location which is about 20 mile from the old location, i switched on checked the compass sensor and it was 1300 but the green safe to fly was on. i did a new calibration and it was back to 1500.. is the setting 1300 safe to fly ? even though the green safe to fly was on. what situations make the sensor lower or higher than the recommended 1500.
     
  2. D4T_PoM

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    Steve from my understanding between 1300-1700 your good (well atleast thats what I do)

    I have also flown with 1900 without an issue but I always ensure and try to be within the range I sepcified above.
     
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  3. BudWalker

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    Interesting. When you do a compass calibration the P3 is determining the gain required to make the reading be 1500. Could you check the compass values back at your old location? If they are higher than 1500 then the new location has less geomagnetic flux. If it's 1500 then the compass has changed. Both of these scenarios seem unlikely. Does the new location have metal, rebar, etc?
     
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  4. III% Streve

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    The 1300-1700 safe to fly estimation is not cutting it for me. I have diagnosed far too many people with drifting issues that had MOD values from 1530-1565. Not that the more broad range is bad. But the number in and of its self has proven to not be a solid indicator. What should be looked at more specifically is the variation in the MOD values between multiple flights from same location.

    When I go to a new location, I turn off VPS, hover and watch. If I get a good stable hover and the MOD value is still within 1450-1550 I turn VPS back on and fly all day without problems.

    If the MOD value changes more than 10 (seems to be a magic number) when flying from a known area then a compass cal is needed or there will likely be drifting.

    I know this is more involved an answer than the question really asked for. Just my observations and the info that I have forwarded to DJI while testing.
     
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  5. lotusteve

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    thanks for the reply.. the new location was in open green land, far away from any metal, the only things near me was 3 picnic benches. i will have a look at the compass latter today.
     
  6. JB-I

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    Maybe there was a Templar Horde beneath your feet! I'd go back and check it out!
     
  7. flyNfrank

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    I calibrate after each fresh battery install, which for me is every flight. Takes all the guessing out of it.
     
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  8. Pluto88888

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    I too calibrate each flight and check Mod Valve 1450 - 1550 before take off.
     
  9. StevenQX

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    Better to be as close as possible to 1500 imo
     
  10. lotusteve

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    I have done a check on the compass tonight,it's the first time it's been on since coming back from the new location and it was 1500ish
     
  11. BudWalker

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    Well, I guess that means that the compass got out of calibration. But, I'm having a hard time with this because I'm in the school that thinks the compass doesn't change without there being a reason. Is it possible that at the new location the P3 was sitting next to something metallic. And, when you picked it up to calibrate it got far enough away from that metal to be normal and then calibration didn't change it much? When the P3 is sitting close to a metal object the geomagnetic flux is drawn/bent to that object and becomes less at the P3. I've seen this in some of the experiments I've done.

    The foregoing is a shot in the dark. I'm really puzzled.
     
  12. John Locke

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    It's good practice to keep the craft away from anyone that may have a cellphone in their pocket when reading the mod value. Same with calibration, make sure you leave your phone in the car or backpack, a good distance from the craft when you pick it up to do the compass calibration dance. I also never have the controller in my hand, I also have the craft at least 15' away from everything when calibrating, just to optimize the area. On the rare occasion that I calibrate, I click the calibrate link in Go, set the controller down on the ground or hand it to someone else, then walk over to where the craft is sitting and do the field dance.
     
  13. Chris P Duck

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    Yup, I do the same. Even take my watch off and leave that with the controller.
     
  14. Mako79

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    Don't check the mod values at ground levels. Get some height, like 50ft or so and then check. The phantom spends more time flying then on the ground. The lower you are to the ground, the more the compass is influenced. This is why the compass dance must be done at a minimal height of 150cm.

    And I don't do compass dance at every new location. I do it logically. I prime the compass at an open field and assume this is perfect. If i'm near structures like buildings then I allow for influences and assume that it will correct itself in the sky. The only other times I do a dance if I know there is a massive change in magnetic declination (travelling further then 100km east/west).

    On a side note..
    In Aus = 1500.
    Travelled to Vietnam = 1300 (still safe to fly). I did compass calibration and got 1500.
    Came back to Aus = 2000, compass error.
     
    #14 Mako79, Nov 11, 2015
    Last edited: Nov 11, 2015
  15. Justgregg

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    I fly around 1300 tp 1400....thats the best I jave done...no problems.
     
  16. DEllis

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    Not to sound stupid but where do you get the compass readings such as 1300 to 1500?
     
  17. bobmyers

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    Sensors under the MC Setting Screen in the App.
     
  18. RedHotPoker

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    And scroll down, same page for IMU Calibration and Check buttons.

    RedHotPoker
     
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