Compass interference

SHRED · Jul 9, 2022

My old Phantom 3A didn't like being launched from a rebar reinforced table top.
It went into ATTI Mode when I got out over the water on a strong wind. It was freaky but I saved it. Stupidly careless launch on my part.

Do the modern Mavics not do this? Is it safe to launch from a bench like this with the Mavic series particularly the Mini 3 Pro?

Phantomrain.org · Jul 9, 2022

My Experience that the Mavic are much better, all of them at handling Magnetic Interference compared to the Phantom 4 which was a disaster when it came to going into atti mode because of Magnetic interference.

Since we own all of the Mavic Series drones and fly them more than most , not once have we had a magnetic interference warning or atti mode surprise since getting the Mavic Pro.

Phantomrain.org
Gear to fly your Mavic in the Rain. Land on the Water

sar104 · Jul 9, 2022

Magnetic interference at the power-up location is still a problem, because it incorrectly initializes the IMU heading, and it still accounts for a large number of uncontrolled flight events. In some ways it is worse because the criterion for switching to ATTI has been changed since the Phantom range, and the Mavic FCs will stay in P-GPS for longer.

Some later firmware versions attempt to detect and correct that at launch by observing the apparent sudden change in magnetic heading (as the aircraft ascends out of the region of interference) with no corresponding rotation detected by the rate gyros, and then re-initializing the IMU heading based on the new magnetic heading. That is described here. I would not recommend relying on that, however, since it can fail for several reasons:

The aircraft was moved after powering up;
The firmware version doesn't support this function;
The region of magnetic interference is larger than expected.

In general, always verify that the aircraft orientation arrow in the app is correct, i.e. that it agrees with the direction that the aircraft is actually facing, before taking off.

A short explanation of compass function, calibration and errors.