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Compass Calibration, A Complete Primer

Discussion in 'General Discussion' started by ianwood, Jan 8, 2015.

  1. N017RW

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    If you hover the mouse pointer on the "?" that appears in the upper righ hand corner in the calibration 'window' (if you will) you'll get a pop-up that explains it.

    Mine reads:
    Raw values should be between -500 to +500

    Mod value should be between +750 to +2250
     
  2. phenom3030

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    Thank you for the tip good sir!
     
  3. ianwood

    ianwood Taco Wrangler

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    Depending on the boat, it will usually have a whole lot of stuff on it that can interfere with the compass. Many times, you don't know if there's a bilge pump or a depth sounder (or a battery) in close proximity. The hull itself can introduce magnetic deviations. As well, the motion of the boat over the water will contribute to a less balanced rotation which will create artificial deviations beyond what you would get on level ground.

    It's much better to get one good calibration on shore and use that for any boat based flights.
     
  4. Marlin009

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    Makes sense. Thanks.
     
  5. morph000

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    "Wait for the Phantom to complete home position and heading recording (2 sets of green flashes) "

    Y'know... I was just now wondering if the order of events is significant.
    Calibrate compass first after power-up or wait for gps/course lock then do it.
    So much to learn, so few hard facts, so little time left (2015.75) :mrgreen:
     
  6. N017RW

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    It's extremely insignificant.

    I have calibrated my P2nv's compass 3 times since May '14.

    Twice out of the box, once after replacing the Rx.

    I have ~100 flights and flown as far away as 600 miles from the cal. location with no issues.

    YMMV
     
  7. ianwood

    ianwood Taco Wrangler

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    I'll admit there's no science to that recommendation but the Naza is probably not the best at multitasking cleanly (no idea if it is an RTOS). So waiting until home point/heading are done simply means the Naza is probably doing less and is more likely to get a cleaner, more accurate reading.

    I often go dozens of flights before I need to recalibrate as well. I do follow the criteria in the first post. Are you recalibrating after firmware updates? It is possible for DJI to give you the perfect magnetic calibration for Shenzhen via their firmware.
     
  8. PTCX

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    A quick tip for flying from a dry sandy beach is to use a C-Gear mat to stop any sand getting into the motors or anywhere else.
    If it's good enough for military helicopters in the desert it's good enough for Phantoms.
    See one in use in this video of mine.
    https://www.youtube.com/watch?v=3qz5hvzW9FE
    Works just as well in dusty areas too.
    Search for C-Gear mats on ebay or google to find them in your area.
    Buy the way there was a lot of Rutile & Zircon in the sand on the beach in the video above but it has been mined out.There are many metallic substances in beach sand depending where you are but if you see dark grey,brown or black grains you can be pretty sure it is metallic.
     
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  9. N017RW

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    Yes I cal. after a f/w upgrade.

    It was at the same time as replacing the Tx, early August I believe as I also updated to 3.06 at the same time.

    No other f/w or hardware mods/updates updates since.
     
  10. nipharmacy-mail

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    As a newbie I have noticed 2 variations of the second calibration step on YouTube i.e. The stage where you rotate copter nose down. I have seen 2 different axis planes used; in the first one, the copter is rotated as if it where a wheel turning around a horizontal axel. In the next the copter rotates around a vertical axis, if you can imagine an axis coming down through battery and out of camera which is nose down. I feel the latter is correct but am not 100% sure??
     
  11. Marlin009

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    You'll find a lot of "variety" on youtube for calibrating and everything else. Just because someone makes a video it doesn't make them accurate.

    It's best go by the manual. At least verify what you're hearing is accurate.
     
  12. Ttito9

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    Nice to know great post
     
  13. snerd

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    I just watched the DJI video on YouTube, and the rep used the compass calibration method of turning his body while holding the bird horizontal, then vertical. I have seen it done that way in another guy's video too. But then I've also seen it twirled in-place.............. just using the hands to spin it in horizontal, then vertical, position.
     
  14. Ttito9

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    They both work the same I my self turn my whole body
     
  15. neslex

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    Thanks for this. Does it matter if you rotate clockwise or counter clockwise? I've seen videos of it being done both ways.
     
  16. Buk

    Buk

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    I've always done it counterclockwise.
     
  17. BlackHawk388

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    I'd be one who wouldn't do a calibration on any beach.

    My other hobby is metal detecting. I find a LOT of trash people have left behind buried just under the surface. Everything from aluminum cans to bottle caps and steel tent stakes, metal toy cars/planes, horseshoes, more than one cell phone, hundreds of dollars in lost change and also, many beaches are highly mineralized due to the nature of a particular beach.

    ANY beach that has volcanic based sand, pebbles and/or flakes is going to be extremely mineralized and in Army aviation back in the 90's, prior to EMI shielding being installed, we were not allowed to perform an INU (Internal Navigation Unit found on some Special Ops aircraft that was used in addition to GPS) initialization if taking off from ANY volcanic area. Hawaii was a place where this was critical, but the world over you can find volcanic remnants. We would be required to do an in flight INU initialization which took forever to complete!

    Finally, even the white sandy beaches here on the Emerald Coast of Florida have a LOT of steel and iron flakes from ships and oil platforms at sea that will wash up due to wave action. In addition to hull flakes, anode pieces from all manner of vessels. All of this shows up extremely well via my metal detector. So much so that I have to use my settings to "notch" out those metal types via iron discrimination or my detector is going off constantly when I'm looking for coins and jewelry.

    This morning when I performed the maiden flight of my new P2V+ V3, I first chose my spot from my truck, the walked over to it with just my metal detector and an Army issue compass to check that area out. The first two places I checked, my metal detector showed underground utilities but my compass barely wobbled. The third patch of ground I checked the metal detector was silent and the compass locked to North without any wobbling.
     
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  18. blade strike

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    I dance with mine, been doing my compass cals this way since 2011. Either way though would be fine..
     
  19. Scifictus

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    Great post - thanks!
     
  20. Rob Flizzle

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    Oh wow, good read...I've been calibrating before every flight, including the times I fly in the same area because I thought I was being safe. Smh
     
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