Discussions

Here's the specifics: APM 2.5, 2.8.1 Software, Mission Planner 1.2.40

Mounted on a quad. The quad flies in stabilize mode very well. I'm hesitant to venture into any of the guided modes - here's why:

Quad is sitting on the table in front of me facing north and connected to MP via the USB cable. GPS is locked with 10 satellites and 3D lock. Compass is calibrated. Flight battery is not connected.

When I first connect MP shows the quad facing north on the map, as expected. As time goes by (say 10 minutes) the compass drifts to the east. The HUD shows 20 degrees and the map matches this new position. Obviously that is wrong, the quad is still on the table and still facing north. The longer I leave it the more it continues to drift.

Watching the yaw numbers in MP's status screen is interesting. Pitch and roll hunt plus/minus around 1.6 and 1.4 respectively. Yaw hunts around 360/0 for maybe five minutes. Once it goes much beyond 0 the positive number builds up faster. Five minutes, it is still around zero, at 10 minutes it has reached and 3.0 is is continuing to build at an even faster rate. At the moment it is taking 30 seconds to add another degree of yaw. I disconnected the GPS thinking somehow that was affecting things but it made no difference. The quad thinks it is turning slowly clockwise. Trust me, it is still facing north on the table and hasn't moved :)

If I simply press MP's disconnect button, then immediately reconnect, the compass display in the HUD and the direction on map are once again pointing directly north.

Again the flight battery is not connected, the only power to the board is through the USB connection. It behaves the same outside too and as far as I know I don't live on top of a magnetic anomaly. My hand held compasses and GPS's work just fine.

So my question - what is going on here?