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Calibrate compass before each flight? The debate

Discussion in 'Phantom 2 Discussion' started by pianoflyer, Mar 16, 2015.

  1. pianoflyer

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    Fairly new pilot... I believe I have seen as many posts and articles saying that I should calibrate before each flight as those they say don't ( only in special circumstances, i get that)..So which is it, why should I listen to the answer...:). And why is there no consensus about this? .thnx
     
  2. 4wd

    4wd

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    There's no need, but you can do it if it makes you feel better!

    If the compass is well out it will tell you on the app for vision range and LEDs in P1 + P2
    It's rather hard on the S1 switch toggling rapidly and they are known to be somewhat flimsy.
    (no longer needed with Vision, you can do it from the app)
    There's a chance of messing things up with a worse calibration than you had already if you inadvertently are near some metal object.

    If you've had it in a vehicle pehaps not far from strong loudseaker magnets it's probably sensible to do it especially if you also travelled at least 20 miles.
    There is no exact distance after which you should redo it.
    Earth magnetic field varies from place to place and over time.
    Some parts of the globe you could move 1000s of miles and it would be little changed, other places there might be a disruption and it could need doing if you moved a much shorter distance.
     
  3. TeamYankee

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    You should only calibrate your compass when;

    * It tells you too.
    * You have added or removed any components from the quad
    * It's been near a magnetic field, speakers in the car etc.
    * Been through TSA scanners...:)
    * Traveled a "significant" distance - YMMV - see here for magnetic declination http://en.wikipedia.org/wiki/Magnetic_declination. Some parts of the world you may not need to recalibrate after travelling North-South for a couple of thousand miles.
    * If you feel it needs to be done due to flight characteristics - TBE etc.
    * If it makes you more "secure" that it won't have a fly-away episode :)

    It's a "hot" topic... ;-)
     
  4. Meta4

    Meta4 Moderator
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    Despite being very conservative in the recommendations of the manual, DJI never recommended compass calibration every flight. If it was important, they would have.
    People who do, do it as a ritual because they don't understand what compass calibration does.
    They feel that if something is good, then more of something must be better.
    It's the equivalent of pushing the button 5 times to make the elevator arrive sooner.

    If the calibration is a little bit out the Phantom won't fly off into the distance.
    It will just have difficulty flying straight.
     
  5. N017RW

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    I have calibrated three times since May '14. The latest due to the swapping of control system to Futaba in June '14.

    Not sure I agree with TSA scanner warning. It did not effect mine.

    YMMV
     
  6. pianoflyer

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    Great input...especially the idea of fragility of the toggle switch. I am curious about the problem of speakers in my car. If I have a 7 speaker sound system in the car, is it basically one big magnetic field that can effect the compass? Hoe close to a speaker is too close? Also , I drive a Chevy Volt plug -in vehicle. Is there a chance the " bed of batteries " under the car could cause a problem? even after calibration on my last flight, I noticed slight drifting on hover in GPS mode, but since it was with a couple of meters figured it was normal.
    Any thoughts about speakers or electric car batteries?
    Thanks
     
  7. tbwester

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    I have only calibrated mine once (when I bought it). It has been all over the United States and traveled by car many miles. I have owned it for almost a year.

    Never had a single problem. But I am always careful to watch how it hovers after takeoff, usually if there are issues you will see them instantly on take-off.
     
  8. TeamYankee

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    A drift in the hover is to be expected.. gps accuracy is not all it's cracked up to be. There is a circular error of probability of around 16 feet with a very good satellite lock.
    Civvies now have the same accuracy as military users, give or take ionospheric glitches.
    http://www.gps.gov/systems/gps/performance/accuracy/
     
  9. ianwood

    ianwood Taco Wrangler
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    Don't listen to these "I never calibrate and I am still alive" rebels. Here's what you need to know: viewtopic.php?f=4&t=32829
     
  10. N017RW

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    Those who calibrate frequently as a prophylactic have no idea if it was necessary or not.
    Because they do so and have had no problems they correlate this to necessary and warranted.

    Doing so when alerted by the system, after hardware changes, or upon observation as 'tbwester' has explained helps to better understand the need and effects of calibration correctable issues.

    "To each his own" I say.
     
  11. lake_flyer

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    The compass calibration is needed when you go to a location where the deviation might be different. But that's very far from where you are now.
    On the other hand, the compass can quite easily be confused when near metal objects (but only when the Phantom is turned on) or magnetic radiation (always disrupting), like in a car with subwoofer etc, or placing it next to your working magnetron. Batteries don't radiate magnetism and generally don't have any effect on the compass.

    It doesn't harm to do the compass dance whenever you want, even in your sleep.
    I only do it when I suspect an error, after any upgrade or change, or when I see that my Phantom is not hovering like I want it to.
     
  12. ianwood

    ianwood Taco Wrangler
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    No. Not all do so blindly.

    Not calibrating increases your risk of uncontrolled flight. Misalignment between compass and GPS increases, vertical orientation is effected. Add a lack of periodic IMU calibration and you increase the percentage of bad data even further.

    Like all auto-pilot systems, the Naza is not perfect. It has edge conditions where it gets confused. But unlike more sophisticated ones, it has no backup or sanity check. Feed it enough bad data and you will eventually go for a ride.
     
  13. pianoflyer

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    Hi. so Ianwood, are you recommending calibrating each time you fly? Also is IMU calibration done simply in Phantom assistant, or is it the thing I've read about where you have to pass a strong magnet around the compass?
    THanks.
    Steve
     
  14. ianwood

    ianwood Taco Wrangler
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    No. Not every flight. That often does more harm than good. Read this: viewtopic.php?f=4&t=32829

    It explains when and when not to calibrate the compass.
     
  15. thestone11

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    My rule of thumb is if I am flying in a different location than my previous take off position. I will do a compass cal just to minmize the chance of flyaway. Less than a min work, but have my equipment safe. I guess it is a good min investment.
     
  16. Meta4

    Meta4 Moderator
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    That's exactly what N017RW meant on the previous page when he said:
    A poor calibration doesn't make your Phantom fly to somewhere else.
    That's not what calibration of the compass is about.
    Understanding how the Phantom flies makes you a better pilot.
     
  17. tbwester

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    I feel like every time you calibrate you have a chance of a mis-calibration. I'd rather just watch how it flies and re-calibrate if there is an issue. It has served me well so far.