Sources of Compass interference

[Michal T]

After reading how some members are calibrating their compasses in the middle of a filed butt naked, I decided to test for the infamous interference.
I went to settings>advanced>compass tab and the interference indicator was at about 5% (green). You can actually see the interfeerence increase as you bring your mavic to magnetically charged objects. Bringing my belt buckle, keys etc caused no deviation there. Also having my phone near the mavic, produced no interference. I had the cellular and wifi radios enabled. The only instance when the phone's proximity affected the compass was when the phone speaker was on top of the drone.
The only consistant method of producing interference was to place a pocket knife on top of the battery. Thats when I would notice a significant change. You can actually pinpoing Compass1 and Compass2 that way Thats is also when it switched from GPS to ATTI mode. Interestingly enough, even after the source of interference (knife) was removed, and the interference went down, it kept on switching back and forth betwen the modes. However, a simple reboot brought it back to normal, and no additional calibration was required. I hope this helps some of you out there that are seeing large ammounts of interference. Do some ground testing, and definitly check you compass interference before taking off...
M

 

[duelingglove]

also stay at least 20 meters from cars, powerlines , huge metal deposits like junkyards......try for an open field with grass and trees. unless you're on top of an ancient mine.....in which case youre !@#$%^&&

 

[Techcop50]

Thanks, good to know.

 

[Ender]

THANK you.
Nearly everything is blamed on bad compass or bad IMU calibration which is plain BS.

When i started Multirotors (APM) i watches those numbers closely when calibrating (in Mission Planner you can SEE them, no guesswork) and did a lot of supposedly "deadly" things with only minimal influence.

Its just a tool of the Apologists, not saying there is no bad compass / IMU calibration but its not responsible for each and every incident.

Just take off and do some Yawing at an Altitude above VPS range.
If the Mavic is rock solid so is your Compass calibration.
Add some small fast movements and see if it brakes on spot and you are good to go.

End of compass story.

Ender

 

[BusinessDrone]

Does anyone know how to turn off the 16 ft altitude limitation when flying indoors after an unsatisfactory calibration due to magnetic interference?

I had a job this week where I was using the Mavic to photograph inside a large indoor atrium. I couldn't establish a "clean" compass calibration due to magnetic interference, though I was still able to get the Mavic airborn and up to 16ft. There was a 16 ft ceiling imposed on the flights, and I would have preferred to turn this off, despite acknowledging there was magnetic interference. I flew cautiously, with the expectation that it would start to drift and I may have to hand land. Ultimately, a series of safe flights and landings, but unable to capture the shot required which would have been achieved by approximately 100ft altitude, instead only 16 ft was possible.

 

[gregw]

Does anyone know how to turn off the 16 ft altitude limitation when flying indoors after an unsatisfactory calibration due to magnetic interference?

I had a job this week where I was using the Mavic to photograph inside a large indoor atrium. I couldn't establish a "clean" compass calibration due to magnetic interference, though I was still able to get the Mavic airborn and up to 16ft. There was a 16 ft ceiling imposed on the flights, and I would have preferred to turn this off, despite acknowledging there was magnetic interference. I flew cautiously, with the expectation that it would start to drift and I may have to hand land. Ultimately, a series of safe flights and landings, but unable to capture the shot required which would have been achieved by approximately 100ft altitude, instead only 16 ft was possible.

You need to turn off Downward Vision System to disable the 16 feet/5M height limit if there is no GPS lock. With Downward Vision System off, the Mavic can be flown to a max height of 164 feet/50M...

 

[Logger]

..
Just take off and do some Yawing at an Altitude above VPS range.
If the Mavic is rock solid so is your Compass calibration.
Add some small fast movements and see if it brakes on spot and you are good to go.

End of compass story.

Thanks Ender nice suggestion. . Just to cap it off, what should one look for to see during these tests if the compass was out of whack. By yawing you mean spinning around on the spot right? So if out of whack will it do a spiral instead?

 

[Michal T]

Thanks Ender nice suggestion. . Just to cap it off, what should one look for to see during these tests if the compass was out of whack. By yawing you mean spinning around on the spot right? So if out of whack will it do a spiral instead?

Search for TBE (toilet bowl effect) on the forum

 

[Logger]

No Thanks. I already know exactly what TBE (toilet bowl effect) is, having posted my own TBE events on this and other forums and having the DAT files diagnosed and acknowledged as such.

You describe a process where one should "take off and do some Yawing at an Altitude above VPS range, If the Mavic is rock solid so is your Compass calibration.". Sounds like an excellent idea - I was simply asking what I should expect to see if the compass calibration is out. So if it is not rock when I spin the thing around I gather it should start drifting away aimlessly is that it? Do you reckon this Yaw trick may trigger an impending TBE and cause it to occur at the home point when otherwise it would have happened downtrack when it would be more problematic?

I agree with what you have said and find it hard to believe many of these events including mine were caused by dodgy compass calibrations. Like OP my compass is always well and truly in the green and has been calibrated but once nearly 140 flights ago. I have not done any calibrations since to create a bad or dodgy one.

 

[Ender]

No Thanks. I already know exactly what TBE (toilet bowl effect) is, having posted my own TBE events on this and other forums and having the DAT files diagnosed and acknowledged as such.

You describe a process where one should "take off and do some Yawing at an Altitude above VPS range, If the Mavic is rock solid so is your Compass calibration.". Sounds like an excellent idea - I was simply asking what I should expect to see if the compass calibration is out. So if it is not rock when I spin the thing around I gather it should start drifting away aimlessly is that it? Do you reckon this Yaw trick may trigger an impending TBE and cause it to occur at the home point when otherwise it would have happened downtrack when it would be more problematic?

I agree with what you have said and find it hard to believe many of these events including mine were caused by dodgy compass calibrations. Like OP my compass is always well and truly in the green and has been calibrated but once nearly 140 flights ago. I have not done any calibrations since to create a bad or dodgy one.

Hi !

If you yaw above VPS range and the compass is NOT okay it will at least drift while yawing, it COULD start the TBE as well but at least it should drift.
If you use roll and nick commands (just short twitches of the stick) it should just do that and brake fast afterwards (depending on your active braking system). If the compass is off it should start launching towards a TBE spiral.

All the latest incidents look like compass was fine at the beginning and got some deviation after those (or CAUSING those) GPS alerts (high sat cound, low quality) and then the deathmatch usually starts...

So be sure to try the above but that wont save us from the mysterious things happening, IF you do that and the Mavic behaves nicely it will just be another hint that the compass calibration isnt bad, it just BECOMES bad in the flight somehow.
Lets pray for a SW Bug, not HW.

Ender

 

[Logger]

Thanks for the explanation. Yes indeed, fingers crossed.

 

[BusinessDrone]

You need to turn off Downward Vision System to disable the 16 feet/5M height limit if there is no GPS lock. With Downward Vision System off, the Mavic can be flown to a max height of 164 feet/50M...

Thank you! That will be helpful for next time I am faced with the same situation.