I have been encountering numerous compass errors with my new Phantom 3 SE when flying over fields at high speed, in 50m height, definitely far away from magnetic interference. Before each flight, I calibrate the compass.
Going through old forums, I found this to be the likely reason:
When you draw a lot of power, the magnetc field created by the aircraft itself is higher, and on the P3 it is appearantly strong enough then to interfere with the compass.

My question is: Can anything be done against this? Is there a lightweight way to shield the aircraft to emmit less of a magnetic field?

Also, has anyone else experienced this lately? I would really like to know.

Stop calibrating the compass every time.  Speed should not affect it in any way.

What Alabama is saying is good, practical advice. I would like to add is to try flying in a different spot to see if this issue is consistent or only with this spot.

Alabama Will do.

Well, Mark, I have encountered issues in various spots. I also tried out a method that I found, it seemed a little bit unreasonable to me, but I did it anyway: I used a magnet to purposefully screw up the compass and kind of "reset" it, and then recalibrated it.
In the end, the problem might be that I'm calibrating in my backyard, and that sometimes seems to work well and soemtimes it doesn't. I don't really have a good spot to do test fligths, that's why I launch there.
Today I was even getting a compass error during the calibration, then other times it works fine. Is this inconsitency usual? Because it doesn't really seem to make sense.

By the way, at one flight today it was off so far that it was literally correcting its position in the wrong direction, effectively drifting sideways to the wind. This was in my backyard, though.

fansef854c89 Posted at 2017-10-16 11:31
Alabama Will do.

Well, Mark, I have encountered issues in various spots. I also tried out a method that I found, it seemed a little bit unreasonable to me, but I did it anyway: I used a magnet to purposefully screw up the compass and kind of "reset" it, and then recalibrated it.

You need to get a good compass calibration and then leave it alone.
Your problems are entirely due to messing around with a compass that didn't need anything in the first place.

Labroides Posted at 2017-10-16 15:22
You need to get a good compass calibration and then leave it alone.
Your problems are entirely due to messing around with a compass that didn't need anything in the first place.

I will definitely try to find a place where I can do that and then keep it.
It actually explains quite a lot, because I've heard advice to calibrate your compass often (obviously from people who don't know their stuff) and so I did. So I guess I caused my issues that way. I'll try doing my calibration properly tomorrow and then get back to this thread to tell you guys if it worked.