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UNDERSTANDING COMPASS AND MAGNETIC FIELDS

Discussion in 'Inspire 1 Discussion' started by PB30X, Jun 14, 2015.

  1. PB30X

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    http://gps.ece.cornell.edu/SpaceWeatherIntro_ed2_10-31-06_ed.pdf

    http://copter.ardupilot.com/wiki/common-appendix/automatic-compass-declination/

    ****If anybody would like to add, by all means PLEASE DO!! And make this a STICKY PLEASE!!****

    Seems to be allot of misunderstanding/misinterpretation of calibrations when, and why they should or SHOULD NOT be done! Instead of arguments of who's RIGHT or WRONG.. Now you decide and Learn for your own SAKE and SAFETY. Google Search Works wanders

    COMPASS SENSE goes a long ways
     
    #1 PB30X, Jun 14, 2015
    Last edited: Jun 14, 2015
  2. The Editor

    The Editor Moderator
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    Great couple of documents - thank you.
    First one might be a little daunting and probably a difficult read for some. Bubble theory!!!!
    Basically, for our purpose, space weather CAN affect GPS accuracy but as long as you keep an eye on what's going on and probably do not fly with anything over a kp index of 5 you should be fine.
    Second document, gives some good guidelines as to the minimum distances items can have an influence on the compass!

    Have stickied this thread.
     
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  3. MoxieSky

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    My first post...
    I have had 95 flawless flights on my I1....until yesterday. This thread caught my attention because yesterday I had my first "hard landing" and I was really confused at first as to what might have caused it. I had just flown it about a mile away with no issues. Drove to new location and launched it. Immediately after takeoff it started drifting. Was acting like it was in ATTI mode with a wind, however it had a great GPS signal and did not appear to change modes. It was very loose on the controls and concerned me (since I was near a lake). I tried to set it down, but with the excessive drifting side load it flipped over on its side. It only chipped 2 prop tips but also cracked a carbon fiber arm which I have repaired (for now) and it is flying normal again. Hurt my pride more than the craft.

    My question to you guys is, there was a thunderstorm pretty close...actually really close I'll admit. It was an isolated cell that was cruising by real fast. I was way out in the clear and it was moving away from me but I wondered if the electrical energy in the storm had effected this? The other thing I noticed was I failed to fold out the antennas into the proper position and didn't notice since they were behind my iPad. Any chance this could have caused it? The I1 never got more than 50' away from me though.

    This is my 3rd DJI product. I admit complacency may be setting in. I've went so long without any problems that I've started to take this amazing little machine for granted. I just flew the last 2 weeks with it in Hawaii and it was exilerating to fly there. Sure glad this didn't happen while I was standing out on the lava rocks cruising it over the Pacific!

    Any thoughts from you guys (The Editor in particular)? Thank you!
     
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  4. sirnikolas

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    Great posts guys!

    @MoxieSky - Firstly, welcome to my forum!

    Did you calibrate the compass before any of the 2 flights? Did you happen to look at your MOD values prior to taking off? If yes, what were the readings?

    Next time this happens to you please switch to ATTI and immediately try and land her safely and then check your mod values.
     
  5. lrwskyfilms

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    Very interesting thx for sharing, do alloys or aluminium have the same effect as steel?
     
  6. MoxieSky

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    Yes, I did a compass calibration he flight prior (about a mile away). I don't normally calibrate it before every flight, however I had just relocated it about 4000 miles so I definitely was going to. I failed to check MOD values before the flight (admit I was getting complacent) but I did a few minutes after the incident and they were normal. I will definitely switch to ATTI mode next time hopefully if this ever happens again, I think I was in shock that I was suddenly loosing control and just tried to get it on the ground immediately.
     
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  7. The Editor

    The Editor Moderator
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    YOUR forum eh? :p
     
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  8. The Editor

    The Editor Moderator
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    Welcome to the forum.

    KP index was high yesterday so you may have experienced more drift than usual even in GPS mode http://www.tesis.lebedev.ru/en/magnetic_storms.html
     
  9. richard.dyson1

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    I didn't fly yesterday but my car sat nav was way off! So I can imagine it caused chaos for any rookies flying.

    Sent from my GT-I9505 using Tapatalk
     
  10. InspiredOne

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    Maxwell's Equation...? What the...? :confused:

    Well, that certainly took the fun out of flying an Inspire 1 for a moment. o_O

    Postings such as that should come with a warning, like...
    WARNING: The following link contains deep scientific theory containing advanced partial differential equations that, together with the Biot-Savart law, form the foundation of classical electrodynamics as it pertains to the magnetic field on the axis of a current loop.

    The point being: If you can understanding that warning, then knock yerself out, click on the link and continue reading.

    For those of us who are totally clueless as to what the heck they're talking about, then click here.
     
    SpyderToph, Busch, PB30X and 2 others like this.
  11. FangsCPO

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    What's the app to measure the kp index?
     
  12. PB30X

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    This really isn't an app, but it works well

    http://www.uavforecast.com
     
  13. David Gibson

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    Wow! what a brilliant site, Thanks for the link PB30X
     
  14. FangsCPO

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    wow! OUTSTANDING site!!!
     
  15. dmelle

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    On the first link from the OP, if you scroll past all those word looking things, and the math type stuff, there are pretty pictures :)
     
  16. AllanVB

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    GREAT site.
    Thanks
    I will use every time I fly.
     
  17. ajohnsonlaird

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    Hmm. The forecast KP Indices do not seem to match up with n3kl.org (the NOAA site). Yesterday we had a major storm (don't think I've seen KpIndex = 8 before), though. Bear in mind this is UTC, so for Pacific Time we're -8 hours. Each bar is 3 hours.

    noaa_kp_3d 2015-06-23.gif

    However compare the above with uavforecasts:

    uavforecast 2015-06-23 2236 PDT.png

    Uavforecasts.com seems to be able to forecast KpIndex for 2015-06-24 through to 2015-06-30 -- which is interesting. I wonder where that forecast data is coming from.
     
  18. Richard in ky

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    I really don't understand why the compass is blamed so much, Most instruments that use compass and gps the compass is only needed when standing still as soon as you move, from the GPS reading the computer knows you moved from point a to point b so it not only knows what direction it is heading but how fast you are traveling. There is so much out there that can affect a compass reading that it seem silly that it should be relied upon so much.
     
  19. David Gibson

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    Hi Richard
    This magnetic storm will interfere with your compass, your GPS positioning and your RC radio transmission.
    If it did only interfere with the compass then I would agree with you, unfortunately it interferes with many other electronic devices as well.
    Rgds
    David
     
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  20. JohnHan

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