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Compass cal while IMU warming?

Discussion in 'Pro/Adv Discussion' started by StratocasterDave, Oct 20, 2015.

  1. StratocasterDave

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    Quick question. Is it okay to do a compass calibration while the IMU, and aircraft for that matter, is in its warm up process?
     
  2. RedHotPoker

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    When your IMU is warming up, you might consider to recalibrate it, when the drone is cold. There wouldn't be any noticeable warm up.

    Leave it stationary until you get the green safe to fly indicator.
    Then though, the calibration is unnecessary. You only, really should calibrate the compass, once. That is, unless you travel more than 100 miles away, from that point, to fly.

    RedHotPoker
     
    #2 RedHotPoker, Oct 20, 2015
    Last edited: Oct 20, 2015
    JohnK likes this.
  3. StratocasterDave

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    Okay, on screen the IMU Warming Up blinks yellow for a few seconds. Then it says Aircraft Warming Up. Then I get the Green Safe to Fly indicator.

    If I needed to do a compass calibration, do I wait until I get the green light?

    Then...this raises the whole calibration process as a whole. I have been doing it whenever I depart a new location from the last time I flew.
     
  4. John Locke

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    As redhotpoker states, there's no need to recalibrate the compass unless you travel 100+ miles from your last flight. The controller will usually tell you to recalibrate the compass when needed, but not all the time.

    It's unwise to recalibrate at every location. You should minimize this to 100+mi relocations.
     
  5. dirtybum

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    Doesnt hurt to if it makes ya feel safer
     
  6. JohnK

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    Why would you risk it? Let the processes complete fully and independently. BTW ... I just did a road trip of 5,800 miles and calibrated my IMU twice (for temperature) and my compass 5 times without incident. Big fan of checking the compass mod value before every single flight.
     
  7. StratocasterDave

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    Okay, I'm getting confused. I would tend to side with you guys but here's a clip from the actually P3 manual:

    IMPORTANT: Always calibrate the compass in every new flight location.

    Page 44

    So, obviously calibrate when it says to do so. But DJI says to do it as part of your pre-flight or when you "fly in a new location or in a location that is different from the most recent flight"
     
  8. JohnK

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    As important, if not MORE important, than how OFTEN you calibrate is WHERE in terms of conditions. On concrete with rebar? Near power lines? Etc. I can only report my practice. I check my compass mod and compare it to the prior setting. On this road trip, it was nearly always between 1450 and 1510. If it went outside of that range (above 1510 in each case), I did a recalibration. I can tell you I flew 45 times from Bismarck, ND to Seattle to Portland to Salt Lake City and back to Bismarck over a one-month period with no problems.
     
  9. eyecon82

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    I calibrate every time. It's out of habit of owning the p2vison +

    Sent from my SM-G900P using Tapatalk
     
  10. JohnK

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    Honestly I don't read the threads here much anymore due to all of the conflicting info that just adds to the stress and uncertainty of flying. So far so good with what I am doing ... no reason to tune a guitar that's already in tune.

    My road trip gave me added confidence in the status readouts and , as a result, I would rather not introduce the risks inherent in changing stable parameters due to some arbitrary rule that no one can seem to justify objectively.

    But I'm stubborn. :)

    If you read enough posts, you will begin to notice the absolute certainty of people with opposite opinions. Gets old after a while.
     
    #10 JohnK, Oct 20, 2015
    Last edited: Oct 20, 2015
  11. John Locke

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    Logically a 100mi east or west movement in location is less than 2 degrees to magnetic north. Do you really think the compass sensor is that accurate, or that it matters?
     
  12. JohnK

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    Declination is also not uniform, and the 100 mile recommendation makes far less sense if one is heading north-south (in terms of magnetic north) vs east-west. If you look at this map, you will see why I ddn't recalibrate my compass when traveling from central North Dakota until well into Montana.


    The map shows why arbitrary "100 mile" rules are not meaningful. People in North Dakota would prob never need to recal based on position alone.

    Magnetic Declination
     
  13. JohnK

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    Anyone who wants to do a REAL study of this should correlate reports of "fly-away" with the severity of the declination in the flight area at the time of the occurrence. A strong correlation would not be surprising, imo, although without specific info I would not make any large bets.