To Those Who've Experienced Compass Errors.....

[Vertigo]

Your statement implies that you can calibrate a compass successfully in an environment that has some local effects (ie, rebar) and still have acceptable mod values. And that you should calibrate pretty much at every flight.

I'm certainly not implying the latter, far from, I recommend recalibrating only if you have a good reason to.

As for the former, Im pretty certain you can do a 'successful' calibration that is location specific. Whether or not mod values will always tell you that, Im not sure. I wouldnt count on it.

 

[Kima kim]

Stop calibrating the compass before every flight. It is not necessary. You are introducing errors when you do this. When you get a good calibration, leave it.

If you don't calibrate the compass as you suggest, would it still know where "Home" is after RTH is activated or loss of signal from RC?

 

[Kima kim]

No its worse than a waste of time; chances are one day you will calibrate somewhere with a local magnetic anomaly, and once you are high/far from the anomaly, your bad calibration will come back to bite you.

But isn't Compass Calibration needed for the P3 to know where the "Home" is?

 

[HWCM]

If you don't calibrate the compass as you suggest, would it still know where "Home" is after RTH is activated or loss of signal from RC?

Yes it will. It stores the calibration.
The home point is gathered from the GPS coordinates, not the compass. This information is downloaded to the craft every time you turn it on. That is why the app displays and the lady says, "Home Point Recorded, verify it on the map".

 

[HWCM]

But isn't Compass Calibration needed for the P3 to know where the "Home" is?

No, the compass tells the flight controller which way to go. The GPS records the home point.
North is always North etc.

 

[Dal]

I've been fighting the compass error for three weeks now with my new second p3s tried it all I got 166 flights with the first one. So I'm not new to proper calibrations. I've eliminated software as the issue as I fly both quads in the same are as well as calibrate them in the same place old one never once set that error and new one does. So it's something with the unit itself in my case


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[Vertigo]

Try degaussing the compass. Spin a (strong) magnet close to it, pull it away. like this guy is doing to degauss a CRT monitor:

 

[out_droning]

I'm a bit bemused why people calibrate every fight. It really is not needed. The only time I re-calibrate my compass is if I ever fly more than 100km from where I last flew it.

I test the calibration by taking off and hovering 10-15 meters above the ground for a good 20 seconds. You'll have no dramas in my opinion.

 

[Kima kim]

Yes it will. It stores the calibration.
The home point is gathered from the GPS coordinates, not the compass. This information is downloaded to the craft every time you turn it on. That is why the app displays and the lady says, "Home Point Recorded, verify it on the map".

Thanks!

 

[Szamboti]

Just thought that I'd chime in on this and mentioned that I just had my first compass error and resolved by restarting the app. I recalibrated the compass more than a few times but the app kept coming up with the error. The bird however showed a successful calibration by its lights. I am a total newbie and I am enjoying this forum immensely, trying to learn what I can.


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[Dal]

Try degaussing the compass. Spin a (strong) magnet close to it, pull it away. like this guy is doing to degauss a CRT monitor:

That looks sketchy and how/where do I apply to the p3s. Drill with some magnets and what pass it by the landing leg with the compass on it? Should o put on a tin foil hat so I look legit? Lol


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[Dal]

Well the p3s was sent in today. Let's see if they actually fix it. I just missed out on the 15 day exchange deal. But who knows maybe I get a nice rep. And just sends a new one. My educated guess it's ether the compass in the landing leg or what ever it hooks up to that processes the data. Hope they figure it out


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[Vertigo]

That looks sketchy and how/where do I apply to the p3s. Drill with some magnets and what pass it by the landing leg with the compass on it? Should o put on a tin foil hat so I look legit? Lol

nothing sketchy about degaussing. Its just a way to remove a magnetic field:
Degaussing - Wikipedia, the free encyclopedia
Which will solve the problem if the cause is that the sensor or wires themselves have been magnetized, which can happen with magnetic screw driver, putting the phantom too close to speaker magnet etc.

Maybe this video will convince you its not hocus pocus:

 

[Dal]

Yeah, no I believe it. I was mostly making fun of that video. Well I sent it in now will see what they say and how it flys. If it's still the same I'll try it. So I pass a magnet around the leg where the compass is?


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[Vertigo]

You spin or rotate a strong magnet pointing at the compass leg yes. A screwdriver likely isnt enough, find a large rare earth magnet.

BTW the thinfoil may actually help; not as a hat, but as wrap for your phantom. This is pure speculation on my part, but I wonder if many people with this problem are driving electric or hybrid vehicles and that these cars produce a non trivial magnetic field inside the car. Googling I did find this:
Measurement of the magnetic field inside electric vehicles
On a tesla forum, I read someone measured between 100 and 1400nT

While Im sure these levels are safe for humans, I wonder
if these levels could possibly be problematic for our drones.

 

[Dal]

Well correct me if I'm wrong but isn't the top shell shielded with a stick on sort of foil from factory


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[Vertigo]

Well correct me if I'm wrong but isn't the top shell shielded with a stick on sort of foil from factory

Nope, its not. And even if it where, it would do nothing to protect the magnetometer in the landing leg. You can not put a magnetometer in a Faraday cage and expect it to work, or IOW, you can not shield it from magnetic influence and still be able to measure earths super weak magnetic field.

 

[Dal]

Got ya


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