I forgot to calibrate compass

[techmyjustin]

The flight went well, it was the first time I've flown in this location, and the first time I've flown near mountains. I was in a canyon so the satellites were down to 9.

Once I landed after a full flight, it was after I had powered it down that I realized I forgot to calibrate the compass. I was being super careful in preparation for this flight and it's something I totally forgot to do.

I was under the impression that this should be done every time I'm flying in a new place. So this begs the question, if the flight went good and everything appeared normal, what is the real purpose for compass calibration?

 

[N017RW]

I see your registration here is recent. However you may have 'lurked' prior.

This is a very contentious issue with opinions ranging wildly and probably a hundred or more threads about it.

I have a P2 that has been compass cal-ed three times since May '14 with the last being about 1.5 years ago.
I have since traveled 600 miles from the last cal location and returned with no problems.

Compass compensation is more about correcting errors in the mag-field near the compass created by components in/on the aircraft, so-called "hard' and 'soft iron' distortions than from the mag-field itself. While this cal is dependent upon the local mag-field it is not, as you have just discovered, as critical as many think to do so before every flight.

If the App. did not alert you of a mag error than you have (had) nothing to worry about.

 

[msinger]

Check out this thread for more details on when and why to do the compass calibration.

 

[WetDog]

When I started out with the P3, the current feeling was 'calibrate early, calibrate often'. So, I dutifully did the dance and confused a lot of people ('mommy, why is that strange man going in circles?"). Then Ianwood's magnum opus (see above) came out. I'm not sure I agree with everything he says but the gist of it seems correct - check your Gyroscope mod value (Advanced | Sensors). If it's somewhere in the neighborhood of 1400 - 1500 you're fine. If not calibrate. Another point he makes is that a bad calibration can get you into a fair degree of trouble. I'm not sure you can really do that - when I've tried to calibrate in 'bad' areas (next to a car, on top of rebar) the app complains and stamps its feet. But he seems to feel that it happens and has quite a bit of experience.

So release yourself from the tyranny of Compass Calibration!

Makes flying a bit more enjoyable.

 

[kirk2579]

When I started out with the P3, the current feeling was 'calibrate early, calibrate often'. So, I dutifully did the dance and confused a lot of people ('mommy, why is that strange man going in circles?"). Then Ianwood's magnum opus (see above) came out. I'm not sure I agree with everything he says but the gist of it seems correct - check your Gyroscope mod value (Advanced | Sensors). If it's somewhere in the neighborhood of 1400 - 1500 you're fine. If not calibrate. Another point he makes is that a bad calibration can get you into a fair degree of trouble. I'm not sure you can really do that - when I've tried to calibrate in 'bad' areas (next to a car, on top of rebar) the app complains and stamps its feet. But he seems to feel that it happens and has quite a bit of experience.

So release yourself from the tyranny of Compass Calibration!

Makes flying a bit more enjoyable.

The p2 vision plus did not have the calibrate info in the app used then.
So it was a lot easier and common for folks to calibrate near metal structures or rebar etc.

As N017RW says do it when indicated, otherwise enjoy the time flying.

good luck and have fun flying!

 

[Kans]

Nice artice from Ian above, so here is a question,

As part of the pre flight, i check the radar icon to see if the direction is correct and then hover for around 20 secs to confirm things are normal before it goes too far.

Will a compass issue show up in that initial hover? Instable hover, random yaw?

That way i can land it and calibrate......

 

[John Locke]

If there is a compass error, you'll know it, not from the radar, but in the GREEN READY TO FLY (TOP of SCREEN) will go RED and say COMPASS ERROR. The craft will automatically go into ATTI mode, so if you're flying at the time you'll notice you'll drift with the wind. Just fly it back, promptly, and carefully land. Remember, you'll have to give it the brakes to stop, pull back on the right stick to stop. Take it slow and you should be OK. The elevation stabilization should be OK, that's handled by the barometer.

Compass errors happen at random, that's my experience. I can fly the same area twice before on the same day, and the third flight I'll get compass error. That was my only experience of a compass error while flying, and that was with my P3P, only happened once. But I brought the craft back, fortunately in calm air, landed, recalibrated, and it was fine to fly the 3rd flight. I had no problems. I was at the beach with nobody around, no structures nearby, nothing I could see that could possibly change the magnetic field. I was 75' in the air about 200' away and bingo, COMPASS error popped up on my screen. It just a happened for no reason, from what I can tell. I'm not pointing the finger at the craft causing the error, because it's been a great craft, very reliable, actually it's been an amazingly reliable P3P. I classified that event as an explainable anomaly.

My P4 has been a little more flakey, but my confidence isn't broken (currently in for repair). However, it's never had a compass error. I only calibrate when I move more than 100mi from the original compass calibration location, when I update the firmware, or sometimes when it tells me too during pre-flight setup.

In the last year, a couple times I have had a compass error before take off, but I don't automatically calibrate. I simply move the launch location, double check my mod value to be between 1425 and 1525 (my preferences), and sometimes I'll reboot the craft. Usually moving location fixes the problem. In those cases the cause of the error can usually be explained with having too much metal near the takeoff point, like a manhole cover, metal table, etc.

 

[ianwood]

Detecting compass errors is not an exact science which is why we can sometimes see errors at odd times. Another interesting tidbit is that a bad calibration can often only be bad in a subsection of the full compass range. With a bad calibration, you may not see any issues until you rotate into that range.

The guide I came up with is really just a summary of information collected from the experiences of many fliers out there combined with some insight into how the compass works and what the calibration is actually trying to achieve.

 

[Sim597]

I used to calibrate ever time on my p3, but I am new to this. That is because the directions from DJI kind of lead you into that on that version. I noticed on this series, the four, they actually contradict themselves, on one page they state it's one of the things that should be done before every flight, then they go on to say if you move to a new location, the latter is correct, the former is for lawyers to say they said every time.


Sent from my iPhone using PhantomPilots mobile app

 

[Meta4]

Another point he makes is that a bad calibration can get you into a fair degree of trouble. I'm not sure you can really do that - when I've tried to calibrate in 'bad' areas (next to a car, on top of rebar) the app complains and stamps its feet. But he seems to feel that it happens and has quite a bit of experience.

Often calibrating in a bad location, the compass will have trouble and protest about it.
But that isn't always the case and it is possible under the right circumstances to go through the calibration procedure in a distorted field and "successfully" calibrate for that distorted field.
The problems start when you fly away from the influence of that magnetism and now your compass is correcting for something that isn't there.
Here's an example of how that can look:

To view this content we will need your consent to set third party cookies.
For more detailed information, see our cookies page.

Accept third party cookies

 

[techmyjustin]

OK thanks for the feedback. I think I've seen a couple of video tutorials showing that if you've flown from a certain spot before, no compass calibration was needed, but if it was a new spot, you should perform a compass calibration.

That's good to know I don't need to perform a strange Mime act before I fly, as people are already watching me when I break out the Phantom 4, I never did like performing the "dance" in front of strangers.

Thanks!