Problems with magfield

Hello, good afternoon, how are you?
I have a fleet of drones that use GPS:
I usually use them flying in groups, and I always had problems with magfield, for example, in fly with 30 drones, about 20 accuse magfield when I turn on.
Recently analyzing magfield and magfield2 data, I noticed that I have a huge variation in the data, for example magfield1 which is the GPS, starts at 190~200, but when I move the drone to any direction, it goes up to 800, but then that I do compass it sets in the range of 200 which is a good number according to ardupilot wiki.
However, if I turn off the same drone that was calibrated and had a good value, sometimes just by turning it on, it comes back with instability and accuses magfield.
I “cleaned” as much of the cables and components as possible that could be interfering with the FC and gps, and even then, it’s still bad.
I needed to improve this because in a show of 60, 70 drones, if we have to do 30 bars, we lose almost all the drums and there’s nothing left to do the show.
Could someone help me with this problem, please? I will be forever grateful for the answers!
I don’t know if it’s the quality of the GPS, or some parameter that doesn’t store its offsets and generates this magfield, I even raised the hypothesis that it’s the territory I’m in (Brazil), because I have contact with friends from other places in the world and they don’t have this problem, using the same materials/drones.

I think it’s important to notify is that when I rotate the drone, the GPS magfield variation is very large, for example, at one point it reaches 170 and at another, 550, 500, just by rotating the drone.

Regarding the “fitness” that appears on the MissionPlanner compass page, does it influence anything on the GPS accuracy?

Try doing the Compass/Motor calibration, but otherwise people would need to see a .bin log

I don’t know if this is helpful or not, but I give you my observations.

I live in Thailand, we fly many missions with our VTOL in many parts of the country. We found that in some locations, we have very weird compass readings.

One for example, is on the shore of a lake, and the compass is at least 30 degrees off when we start our preparations. When we first came there, we recalibrate the compass, but had compass errors in flight.

I think the reason is that there is something in the ground that screws up the magnetic field. Nowadays, we know which places have these problems and we just take off and fly. No compass errors during flight, only at take off and landing.

It may be an old burried scrap yard, it may be some iron ore or something else.

So we now calibrate our compasses in an area where we are 1000% sure there is no problem. Maybe this is helpful to you.

Hello Facta! Good night, how are you?
Yes, I’ve already performed this test on all our drones, but the problem of having to do compass often when we go to different places still persists, I know a team that hardly needs to compass as often, in a scenario of 100 drones do only 5 compass.

Hello verloop! Good night, how are you?
Thank you very much for your reply, and I regret the delay of mine.
I believe you are absolutely right, we face a lot of adversity from places that we did not know what was there before, and we always have a high rate of drones asking for a compass just by calling.
We decided to adopt this action for all our next flights to recalibrate the compass at all shows, because we can’t have the same precision as some partners that are in other corners of the world.
But I’ll keep studying to see if I can improve the GPS accuracy to the point where I don’t have to recalibrate every time.
Thank you very much for your willingness to respond!

My pleasure. Sharing experiences is what this community is all about. :smile: