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Phantom Original - Compass Interference!

Discussion in 'Photos and Video' started by AlexanderAF, Jan 11, 2015.

  1. AlexanderAF

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    I took my Phantom to the top of a mountain today and tried to calibrate the compass pre-flight. After three attempts, I still got a yellow/red blinking light, a first. I decided to restart it, skip the calibration, and get a GPS lock. Once I got that, I took off...

    http://youtu.be/8Nn0Lr7VZik

    Enjoy!
     
  2. ianwood

    ianwood Taco Wrangler
    Staff Member

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    Those big things. Not the dogs. The things sticking out of the ground. The rocks. They've probably got some iron in them. Don't calibrate near them and don't take off from them. You can probably take off near the dogs. They don't seem to mind.

    viewtopic.php?f=4&t=32829
     
  3. Great Pumpkin

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    Alexander AF: Please tell us the location of the mountain top where you had the compass calibration difficulties so that we can determine the kind of rocks there and if they may have enough iron in them to have caused your problems.
     
  4. AlexanderAF

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    U Mound at the Sandia Mountains
    Lat: 35deg 4'52.66"N
    Long: 106deg 28'50.77"W
     
  5. Great Pumpkin

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    Everything I can see and read about U Mound says that it is a 1.4 billion year old porphyritic biotite granite. That may not mean much to you readers, but to me is says that magnetic problems should be highly unlikely on the rock, because granite is almost devoid of magnetic minerals such as magnetite and ilmenite.
    But you can test it yourself at U Mound or anywhere else. Take an ordinary compass out with you. See if it points north as it should. See if the needle starts to swing back and forth as you lower it to the ground. I'll bet 30ยข the compass will be very stable on U Mound. You can cause a compass to go haywire just by getting up close to your metallic belt buckle or by putting a mechanical pencil on the cover glass and rotating it around a vertical axis.
    Having said that, Alexander AF, I have no ready explanation for why you had compass calibration issues on U Mound, but I don't believe it was due to the rocks.
     
  6. AlexanderAF

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    Great Pumpkin

    Thank you, that is amazing! I've always wanted to know more about the giant mound behind my backyard. The only other things I can think of is it is at altitude, and/or there were tall power lines nearby. However, I started back down the mound closer toward the power lines and was able to successfully calibrate the compass. I had three successful flight from there in fact?
     
  7. AlexanderAF

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    Just curious, could I calibrate the compass somewhere where I can get an accurate calibration and then move it to the top of the mountain. If a normal compass works on the top of the mountain, would this prevent this situation from occurring?
     
  8. badbrad97

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    Yes. You only really need to recalibrate your compass if you move a great distant from where you calibrated it. I fly within about 100 miles of my house and have had success calibrating only at the field behind my house and only about every 50 flights.
     
  9. Great Pumpkin

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    You need not recalibrate your Phantom's compass in the western US if you move east or west only a hundred miles or so, but the isogonal lines (lines of equal magnetic declination) are much closer together in the eastern US http://artofwayfinding.blogspot.com/2014/08/magnetic-and-true-north-dealing-with.html, so I wouldn't travel more than 50 miles or so in an east-west direction there without recalibrating my Phantom's compass.