Getting compass error every time I try to take off from new location

[sar104]

Yep Mavic 2 (my m1 has never once prompted for calibration).

It absolutely for certain vanished after the first firmware update and came back with the one after that.
It was fairly obvious for me because due to work its moved > 30 miles every day. I went from having to calibrate daily to not at all so noticed it right away. Then it came back after an update.

2 others i know with M2Ps have never once been asked despite moving it large distances.

Right - the Mavic Pro never had that, or at least mine never asked for it and I have not seen a single reported case of it. That sounds conclusive on the firmware update. Did you ever look at the event stream with the first update when it wasn't requiring it to see if it even conducted the checks?

 

[gnirtS]

Right - the Mavic Pro never had that, or at least mine never asked for it and I have not seen a single reported case of it. That sounds conclusive on the firmware update. Did you ever look at the event stream with the first update when it wasn't requiring it to see if it even conducted the checks?

Yep i did look. The logs show nothing of the distance checking that was present initially.
Either it wasnt checking or if it was, the logic changed and it isnt logged at that detail level.

 

[sar104]

Yep i did look. The logs show nothing of the distance checking that was present initially.
Either it wasnt checking or if it was, the logic changed and it isnt logged at that detail level.

Very interesting. I cannot begin to imagine how they manage to be so random with implementation of these things.

 

[gnirtS]

Very interesting. I cannot begin to imagine how they manage to be so random with implementation of these things.

All i can think of are either different hardware tolerances or different components and revisions on the drone itself.
Different batch compass units might have different tolerances or maybe even different systems depending on when it was built.

I *suspect* the asking to calibrate is a deliberate design intention hence the manual stating it and the log files showing it. But it doesnt seem to be on all M2Ps as i know some people who have never once been asked.

Edit:- i should add this doesnt produce a compass *error*. It doesnt say "cannot take off" and you still can take off and everything is fine.
With an actual compass error it wont do that.

 

[dannybgoode]

@sar104 - apologies, I know you’ve posted this a million times but where are the instructions to retrieve the DAT files. Note I run Windows and iOS but not OS X if this has any impact at all.

I’ll dig out the relevant files for Cyprus and my first flight back in the UK. Note I am running the latest firmware and always update Go 4 etc when prompted

 

[BudWalker]

@sar104 - apologies, I know you’ve posted this a million times but where are the instructions to retrieve the DAT files. Note I run Windows and iOS but not OS X if this has any impact at all.

I’ll dig out the relevant files for Cyprus and my first flight back in the UK. Note I am running the latest firmware and always update Go 4 etc when prompted

How to retrieve a V3.DAT from the tablet

 

[sar104]

All i can think of are either different hardware tolerances or different components and revisions on the drone itself.
Different batch compass units might have different tolerances or maybe even different systems depending on when it was built.

I *suspect* the asking to calibrate is a deliberate design intention hence the manual stating it and the log files showing it. But it doesnt seem to be on all M2Ps as i know some people who have never once been asked.

Edit:- i should add this doesnt produce a compass *error*. It doesnt say "cannot take off" and you still can take off and everything is fine.
With an actual compass error it wont do that.

That's not the case with my M2 - when it triggers a time or distance recalibration request it will not start the motors until the calibration is completed. And I don't see how it has anything to do with component tolerances, since the calibration isn't actually calibrating anything - it's just measuring the aircraft's own magnetic field.

 

[gnirtS]

That's not the case with my M2 - when it triggers a time or distance recalibration request it will not start the motors until the calibration is completed. And I don't see how it has anything to do with component tolerances, since the calibration isn't actually calibrating anything - it's just measuring the aircraft's own magnetic field.

Its possible its reading a noise or quality level threshold that changes from tolerances or revisions of hardware. OR even some modules report it, some dont if not all mavics are identical to the exact component in all releases.

Mine certainly flies, the error is "Check App" (not the normal magnetic interference error). Although it brings up the calibration prompt in the apps the quality bar is single digit and in the green. If you ignore it you can start the motors and fly.

 

[sar104]

Its possible its reading a noise or quality level threshold that changes from tolerances or revisions of hardware. OR even some modules report it, some dont if not all mavics are identical to the exact component in all releases.

But that's my point - the prompt is based on time and distance, not an interference level or anything else.

Mine certainly flies, the error is "Check App" (not the normal magnetic interference error). Although it brings up the calibration prompt in the apps the quality bar is single digit and in the green. If you ignore it you can start the motors and fly.

Maybe I'm missing something. I get the "Check app" message too, but I've been unable to dismiss it without a calibration and the CSC doesn't start the motors. Do you recall exactly how you bypass it?

 

[gnirtS]

But that's my point - the prompt is based on time and distance, not an interference level or anything else.

Im not sure we can conclude that without a way to make the logging more verbose. All we see written there are the actual final decisions of check/nocheck and nothing of the actual mechanics behind it.
Without any way to set more verbose logging we dont know what "health" signals are sent from various modules or the criteria for triggering a calibration.

Mavic 1 was rooted so it would be possible to see the actual system logs (its android after all). M2 i dont think you can.

Maybe I'm missing something. I get the "Check app" message too, but I've been unable to dismiss it without a calibration and the CSC doesn't start the motors. Do you recall exactly how you bypass it?

I didnt do anything special - it was an accident the first time i did it. Simply closed the summary box you get when you first start Go4 and did an ESC, the props started and it flew. I only noticed "check app" later.

It should work if you switch it to manual ATTI before GPS gets a lock too.

 

[BudWalker]

Im not sure we can conclude that without a way to make the logging more verbose. All we see written there are the actual final decisions of check/nocheck and nothing of the actual mechanics behind it.
Without any way to set more verbose logging we dont know what "health" signals are sent from various modules or the criteria for triggering a calibration.

Mavic 1 was rooted so it would be possible to see the actual system logs (its android after all). M2 i dont think you can.




I didnt do anything special - it was an accident the first time i did it. Simply closed the summary box you get when you first start Go4 and did an ESC, the props started and it flew. I only noticed "check app" later.

It should work if you switch it to manual ATTI before GPS gets a lock too.

I think it's pretty compelling that the calibration requests are based on a 30 day elapsed criteria. The eventLog stream entries can be obscure sometimes but with something like this

-47.676 : 3918 [L-COMPASS][mag_cali_pt] date_from_last 30|

it's clear. Also, these entries will occur 30 days since the last calibration.

My theory is that some (most) of the M2s have magnetometers that can drift significantly over time. Those M2s will have the 30 day recalibration request. It's just a theory.

 

[gnirtS]

My theory is that some (most) of the M2s have magnetometers that can drift significantly over time. Those M2s will have the 30 day recalibration request. It's just a theory.

Thats pretty much what i mean, tolerance differences in the components. Something is triggering it and not on all M2Ps. Whether thats by design or not only DJI know.
I've never seen a 30 day calibration message but thats mostly because i fly a few times a week and nearly always moving 30+ miles inbetween flights so i get prompted for a distance calibration instead.
Its not unusual, my mobiles have all needed calibration a few times a day at times. Same for tablets. My digital compass i use underwater needs it frequently. Given the cheap hardware in the mavics i dont see why these should be any different - they're not high quality components and the M2 only has a single unit.

 

[HawkEye76]

The calibration will from my knowledge compensate for magnetic disturbances from the drone itself and local deviations. Most likely the World Magnetic Model is implemented to account for declination from true north. It is a complicated process that tries to make a sphere out of a twisted measured field.
A good link here that describes the process.

Magnetometer Calibration - MATLAB & Simulink

Magnetometers detect magnetic field strength along a sensor's X,Y and Z axes.

www.mathworks.com

Hakon

 

[sar104]

I think it's pretty compelling that the calibration requests are based on a 30 day elapsed criteria. The eventLog stream entries can be obscure sometimes but with something like this

-47.676 : 3918 [L-COMPASS][mag_cali_pt] date_from_last 30|

it's clear. Also, these entries will occur 30 days since the last calibration.

My theory is that some (most) of the M2s have magnetometers that can drift significantly over time. Those M2s will have the 30 day recalibration request. It's just a theory.

But then why the distance-based recalibration, which makes no sense to me under any obvious hypothesis? I had been working on the assumption that it was basically an "abundance of caution" rather than a well thought out requirement.

 

[sar104]

The calibration will from my knowledge compensate for magnetic disturbances from the drone itself and local deviations. Most likely the World Magnetic Model is implemented to account for declination from true north. It is a complicated process that tries to make a sphere out of a twisted measured field.
A good link here that describes the process.

Magnetometer Calibration - MATLAB & Simulink

Magnetometers detect magnetic field strength along a sensor's X,Y and Z axes.

www.mathworks.com

Hakon

That's a pretty nice explanation of the process.

 

[jeplane]

So what do you guys do?

IF the map in the bottom right corner shows a proper orientation of the drone and IF the sensors do not show a high number for the compass or IMU, do you calibrate the compass?

I admit that I am sometime lazy, and if both mentioned above looks good, I've launched without doing a compass recalibration...

 

[BudWalker]

But then why the distance-based recalibration, which makes no sense to me under any obvious hypothesis? I had been working on the assumption that it was basically an "abundance of caution" rather than a well thought out requirement.

Sorry, forgot to mention the second part of my theory is that the distance is just thrown in for good measure.
Mavic 2 Pro out of control, crashed into lake... help?

 

[GadgetGuy]

I'm still on FW version 1.0.0 on a new M2P refurb, and with a presumably properly calibrated M2 compass (no compass warning on the app at bootup), during the flight, the displayed compass direction line on the map and the radar North direction in GO 4 will suddenly change to an inaccurate direction and stay that way, even though the heading and the location on the map are accurate with a fixed North up setting. GO 4 iOS app version is 4.3.12.

Is this a compass issue of the aircraft or the iPad, and what are the suggested solutions? It keeps periodically reoccurring, despite compass calibrations of the aircraft. Fortunately, I know the area well, and so pointing the antennas at the aircraft, even with an incorrect line back to home (keeping the line vertical would result in pointing the RC away from the aircraft) , is still doable. No other issues, and I have over 50 flights on this aircraft.

 

[sar104]

I'm still on FW version 1.0.0 on a new M2P refurb, and with a presumably properly calibrated M2 compass (no compass warning on the app at bootup), during the flight, the displayed compass direction line on the map and the radar North direction in GO 4 will suddenly change to an inaccurate direction and stay that way, even though the heading and the location on the map are accurate with a fixed North up setting. GO 4 iOS app version is 4.3.12.

Is this a compass issue of the aircraft or the iPad, and what are the suggested solutions? It keeps periodically reoccurring, despite compass calibrations of the aircraft. Fortunately, I know the area well, and so pointing the antennas at the aircraft, even with an incorrect line back to home (keeping the line vertical would result in pointing the RC away from the aircraft) , is still doable. No other issues, and I have over 50 flights on this aircraft.

That's the mobile device compass getting the device orientation wrong. It has nothing to do with the aircraft compass. A common problem.

 

[GadgetGuy]

That's the mobile device compass getting the device orientation wrong. It has nothing to do with the aircraft compass. A common problem.

Thanks for clarifying. That makes sense.
What is the best way to reset the mobile device compass on a 9.7” iPad Pro on iOS 10.3.3 ?
Does mounting the iPad on a metal ball used as the tablet holder contribute to this problem?
I use the Skyreat mount in the link below.

Amazon.com: Skyreat Mavic Mini Air Pro Foldable Aluminum Metal 4-12" Ipad Tablet Mount Holder for Dji Mavic 2 Pro, Mavic 2 Zoom/Mavic Pro/Mavic Air,Spark Accessories Remote Controller: Electronics

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