Compass Calibration, A Complete Primer

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So, are you saying that even when the DJI GO 4 App says "Compass Calibration Required" we shouldn't calibrate the compass?
Not unless you are already in an area completely clear of all metal, are outside, and have decided this is an appropriate place to calibrate. Instead of calibrating the compass, first try moving to a clear area area outside, with absolutely no metal interference. Compass Calibration Required means you need to move first, to see if it is the location that is the problem. If it goes away, leave it alone.
 
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So, are you saying that even when the DJI GO 4 App says "Compass Calibration Required" we shouldn't calibrate the compass?
Does it show that message when you're near magnetic metal objects? If so, you should not calibrate it. If there is no potential interference in the area, then it's okay to calibrate it.
 
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You're absolutely right about that because I've taken my Phantom out of the back of my SUV and calibrated the compass right behind the vehicle. Sometimes it wouldn't calibrate and I'd move a few feet away and it would calibrate no problem. I'd occasionally forget about all the steel in the vehicle.

Bud


Not unless you are already in an area completely clear of all metal, are outside, and have decided this is an appropriate place to calibrate. Instead of calibrating the compass, first try moving to a clear area area outside, with absolutely no metal interference. Compass Calibration Required means you need to move first, to see if it is the location that is the problem. If it goes away, leave it alone.
 
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You're absolutely right about that because I've taken my Phantom out of the back of my SUV and calibrated the compass right behind the vehicle. Sometimes it wouldn't calibrate and I'd move a few feet away and it would calibrate no problem. I'd occasionally forget about all the steel in the vehicle.

Bud
Worst place to try and launch your drone from is the trunklid of your car. It may be nice and level, but it will immediately generate compass errors. "Step away from the vehicle!" ;)
 
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I've never launched my Phantom from the trunk of my vehicle. I just removed it from the inside of my vehicle.

Worst place to try and launch your drone from is the trunklid of your car. It may be nice and level, but it will immediately generate compass errors. "Step away from the vehicle!" ;)
 
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Why Calibrate?
Compass calibration is important to safe, controlled flight. It compensates for changing background magnetic "noise", a.k.a. magnetic inclination and deviation (not to be confused with declination). Inclination and deviation that isn't corrected through compass calibration will cause inconsistencies between GPS and compass that can result in "toilet bowl effect", a swirling motion that can cause the Phantom to fly out of control.

What is Magnetic Inclination and Deviation?
Magnetic deviation is a horizontal variation that comes from the Phantom itself and the equipment you have installed on it as well as the magnetic makeup of the area you are flying in (again not to be confused with declination). Sometimes the deviation will be insignificant, but other times it can be big enough to cause you to lose control. Inclination is a vertical magnetic variation that shifts depending on where you are.

Warning Signs
The Phantom can only detect when the compass is providing extremely poor (implausible) data. This typically occurs if you place it near a strong magnetic field or do not calibrate it properly. It will flash red and yellow lights and the P3 will indicate a compass error in the app.

IMPORTANT: The lack of a compass error does NOT mean your compass is working and calibrated properly.

MOD Value
This is the total magnetic field calculated using the "sum of squares" from the X, Y and Z axes. On the P2, you need to plug in the cable and use the assistant software. For the P3, you can see it in the app. It should be between 1,300 and 1,600, ideally just above 1,400. Check it away from magnetic influences. If it reads very high or very low, check it again in a different location. If it is still off, it could need calibration or it could be magnetized or damaged.

IMPORTANT: A good mod value does NOT mean your compass is working and calibrated properly. For example, if you calibrate next to some rebar, your mod value may still be OK until you fly away from the rebar.

What Does Calibration Actually Do?
Calibration measures the magnetic fingerprint of the surrounding area. By turning the compass 360 degrees, the Phantom can see where the compass reading doesn't smoothly increase or decrease. It uses this information to build an adaption table so that when the Phantom turns during flight, the reading is smooth and linear.

When Should I Calibrate?
You do not need to calibrate before every flight and in some cases you definitely should not calibrate. That doesn't mean you shouldn't ever bother doing it. It only takes one time for it to go very wrong. The most important aspect of compass calibration is making sure the magnetic "neighborhood" around your Phantom is consistent between calibration and during flight.

IMPORTANT: The ideal place to calibrate is an open field with nothing metallic in a 20ft radius. Keep away from drainage pipes, irrigation systems, rocks, etc.
  • DO Calibrate
    • Mod value out of whack or compass error reported (check area first).
    • Circling in flight (also check for other possible causes).
    • New equipment added or removed / new firmware installed.
    • Location change (greater than ~100 miles).
    • Significant change in terrain (e.g. to / from mountains).
    • If you just degaussed your compass (BTW, don't degauss unless instructed).
  • DO NOT Calibrate
    • If near concrete, buildings, and hidden or overhead power lines / pipes / etc.
    • If you're indoors, on a paved surface, on a stone surface, on the beach, on a boat, on a balcony, near a car, near speakers, etc.
    • If there are metallic (ferrous) objects nearby or you're not sure
  • Pre-Calibration Checklist
    • Everything used in flight should be powered during calibration, e.g. GoPro, tracker, etc.
    • Remove all metal from within 10ft radius, e.g. watch, phone, ring, belt, coins, controller.
    • Calibrate on grass or dirt and not on concrete, asphalt.
    • Calibrate on a level surface if possible.
    • A cardboard box is a good idea to get it off the ground and level.
  • How to Calibrate
    • Power up your Phantom and accessories as normal.
    • Wait until your Phantom is ready to fly.
    • P1 / P2: Flip S1 five times between the top two positions.
      P3: Select CALIBRATE under AIRCRAFT STATUS | COMPASS. Click OK.
    • Confirm solid yellow rear lights.
    • Pick up the Phantom and turn it smoothly and steadily a full 360 degrees until the lights turn solid green.
    • Point the front of the Phantom straight down and repeat until the lights turn off and resume normal flashing.
      Note: Don't be concerned if your gimbal reacts poorly to being face down, keep turning as normal.
    • Optional: power off and restart Phantom.
    • Enjoy your flight!
If for any reason, you do not complete any of the above steps smoothly and evenly, restart the process.
As a nooby....this was great info!!! This forum is the absolute best!!
 
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Great thread! I always thought I had to calibrate before every flight, regardless of if I flew in same spot. I have a P4 and have only flew around my backyard so far and each time I've been calibrating it. Good to know!
 
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Great thread! I always thought I had to calibrate before every flight, regardless of if I flew in same spot. I have a P4 and have only flew around my backyard so far and each time I've been calibrating it. Good to know!
If it ain't broke, don't fix it! You are far more likely to introduce a bad caibration in an unfamiliar area. If your last calibration was a good one, and you haven't travelled more than 100 miles, leave it alone!
 
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If it ain't broke, don't fix it! You are far more likely to introduce a bad caibration in an unfamiliar area. If your last calibration was a good one, and you haven't travelled more than 100 miles, leave it alone!
That makes total sense. I always thought it was a bit strange that I had to calibrate before each flight.
 
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Question: Does it make any difference if the AC is held steady in front of you and you turn around 360 yourself, vs. rotating the AC on it's axes?

All my physics and engineering background tells me it makes absolutely no difference, but I thought I'd check with the hivebrain.

It's much much much easier to get a uniform, steady 360 that way.
 

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