I flew a few months back and crashed due to brown out. I have now beefed up the cable and done a new flight test. In loiter mode it is showing bad toilet bowl effect. Moving in wider and wider circles.

I read through some stuff and found that compass / mag readings need to free of interference and within acceptable range.

I did a new reading which is as follows:

OFS_X 221
OFS_Y 155
OFS_Z 65
Are these OK?
I also downloaded an autocheck log which gave the following errors:
Test: Compass = FAIL - Large change in mag_field (187.27%)
Max mag field length (1195.51) > recommended (550.00)
Test: Event/Failsafe = FAIL - ERRs found: GPS FENCE 
Test: GPS = FAIL - Min satellites: 0, Max HDop: 99.99
It says GPS failed but the main logs gave an accurate map showing the path of the UAV during flight. Yet it says GPS failed. No satellites.
The GPS puck is not a 3DR type with arrow. I don't think it has a compass inside.
Any suggestions on how to resolve this? Thanks!

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Hello Jamie,

so you don't have an external compass?

Maybe the pixhawk use its onboard compass and getting interference from near ESC or power lines?

Do you change any GPS regarding parameters?


Hi Patrick,

Yes I think the pixhawk has an internal compass. If I rotate the GPS module the heading does not change on mission planner. But if I move the pixhawk it does change. I am getting some kind of GPS and compass readings as it seems to have the location but there are some issues I think.

The GPS pod has a blue light and also a red flashing light. The main pixhawk has a blue pulse changing to green.

Also the mission planner says 'HIGH GPS HDOP'

Thanks Bill. I think I need to run compass mot test. I have currently got my current going direct to my tx telemetry and not into the pixhawk. So the readings might not work unless I have the current there too? 

OK got the test running but it shows interference as zero which isn't right.

This seems to show something. This graph compares throttle to magnetic interference. The base magnetic field is 400 but then spikes up to 600 when throttle is applied. 

My pixhawk came with what i think might be a cheap GPS module. It did work ok before but after a brownout I upgraded my power cables to be much heftier. 10 awg to carry high current easily. Perhaps this has brought more current flow into the PDB and so has generated interference.

I'm think I could rectify this with an integrated gps+compas module.

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