Odd compass error

[Neon Euc]

Looking through the airdata and it mentioned slight compass error when I flew the other day. I was in ATTI mode a lot practicing and noticed it on there (didn't see it on the screen as I was looking at the drone the whole time)

Odd thing is, on the same log, when I go to compass section it says no errors found? Is this normal ?

Here is the airdata flight log

May 8th, 2018 03:06PM | General / Overview | Drone Flight Log from DJI GO app, version 3.1.34 on Android | Total Mileage: 10,236 ft | United Kingdom | Airdata UAV

 

[sar104]

The compass section of the AirData analysis is simply looking to see if there are unphysical turn rates indicated by the magnetometers. The compass error from the FC is generated if the magnetic yaw and IMU yaw disagree and cannot be resolved - different criterion.

 

[Neon Euc]

The compass section of the AirData analysis is simply looking to see if there are unphysical turn rates indicated by the magnetometers. The compass error from the FC is generated if the magnetic yaw and IMU yaw disagree and cannot be resolved - different criterion.

Thanks sar104. It was hard to tell if I did have a compass error as I was learning flying in ATTI mode anyway lol. Was going to try again but a bit to windy and don't want to risk anything just yet

 

[Meta4]

Thanks sar104. It was hard to tell if I did have a compass error as I was learning flying in ATTI mode anyway lol. Was going to try again but a bit to windy and don't want to risk anything just yet

Airdata isn't much use for looking at flight data. It just shows a basic summary rather than the full data.
If you want to check details you should upload your data to the Phantomhelp log viewer.

Flying in atti makes no difference as the Phantom still uses the compass in atti mode.
You wouldn't be risking anything anyway.
A compass error (if you had one) is not a fault in the compass.
It's a good compass telling you that it's detected an abnormal magnetic field.

 

[The Phantom]

I also got a compass error and yaw error and something about IMU on my Spark a couple of days ago, all at the same time. I was flying at about 25 - 30 meters height and over a grass field.
Upon investigating online on different forums most people suggested it was due to being near iron messing up the compass, or a bad compass cal.
But in my case i was flying over a grass field so i don’t buy that explanation, and the compass values looked good before take off. So don’t really know what happened?
It of course also went into Atti mode for a brief moment. When thinking about it it happened directly after the craft went into RTH mode due to loss of signal for more than 3 seconds, don’t know if that has anything to do with what happened though?

I can add that this seems to be a relatively common thing, at least on the Spark.
I read some people who had it happen on their Phantoms, Mavic Pro’s and Inspire 1 & 2, but most where Spark’s.

 

[Meta4]

I also got a compass error and yaw error and something about IMU on my Spark a couple of days ago, all at the same time. I was flying at about 25 - 30 meters height and over a grass field.
Upon investigating online on different forums most people suggested it was due to being near iron messing up the compass, or a bad compass cal.

In Phantoms getting yaw errors is mostly caused by launching from a steel or reinforced concrete surface, and not related to what you are flying over.
Also there should be no such thing as a bad compass calibration.
Your drone shouldn't need compass calibration (even from new).
If it's flying properly, you don't need to recalibrate it.

 

[The Phantom]

In Phantoms getting yaw errors is mostly caused by launching from a steel or reinforced concrete surface, and not related to what you are flying over.
Also there should be no such thing as a bad compass calibration.
Your drone shouldn't need compass calibration (even from new).
If it's flying properly, you don't need to recalibrate it.

Well i also launched from grass or maybe it was from the rock/cliff, so that shouldnt be a reason for the problems either i guess?

And the bad compass calibration is what I’ve read many people saying, that or flying / taking off near iron etc.
But like i said i don’t think that was the reasons for my problems.
I only do a compass cal if told so by the GO app, which wasn’t the case this time, so no calibrations before this flight.
I could see a compass calibration going bad, let’s say the GO app tells you to do a compass cal. and one does the calibration in a not so good environment but not bad enough for the compass cal to fail, and one doesn’t check the compass values after the cal, so one takes off with bad compass values.
Maybe that would count as a bad compass calibration?

What about the lack of a IMU cal, if an IMU cal never has been done on the craft for example, could that trigger these kind of errors? In my case i also had a message saying “IMU encounters heading exception, please switch to Atti mode if craft behaves abnormally”
That message came together with the Yaw error, speed error and compass error.

 

[sar104]

Well i also launched from grass or maybe it was from the rock/cliff, so that shouldnt be a reason for the problems either i guess?

And the bad compass calibration is what I’ve read many people saying, that or flying / taking off near iron etc.
But like i said i don’t think that was the reasons for my problems.
I only do a compass cal if told so by the GO app, which wasn’t the case this time, so no calibrations before this flight.
I could see a compass calibration going bad, let’s say the GO app tells you to do a compass cal. and one does the calibration in a not so good environment but not bad enough for the compass cal to fail, and one doesn’t check the compass values after the cal, so one takes off with bad compass values.
Maybe that would count as a bad compass calibration?

What about the lack of a IMU cal, if an IMU cal never has been done on the craft for example, could that trigger these kind of errors? In my case i also had a message saying “IMU encounters heading exception, please switch to Atti mode if craft behaves abnormally”
That message came together with the Yaw error, speed error and compass error.

All those errors are related, but without looking at the IMU and magnetometer data in the mobile device or aircraft DAT file there is no way to say, definitively, what caused the problem. However, based on history, the least likely explanation is the compass calibration being bad.

 

[Meta4]

I only do a compass cal if told so by the GO app, which wasn’t the case this time, so no calibrations before this flight.
I could see a compass calibration going bad, let’s say the GO app tells you to do a compass cal ....?

DJI's manuals have been updated and they removed some bad instructions in the compass calibration section but they are still misleading.
The only times the app or lights will tell you to calibrate the compass is when your compass is disconnected and calibrating won't fix it.
If you try to launch from a steel or reinforced concrete surface (like the car roof in the pic) , the error message you get says: Magnetic Field Interference - Move the Aircraft or Calibrate.
Many people seeing this, think it's telling them to calibrate but the only correct action would be to move away from the source of magnetic interference.

What about the lack of a IMU cal, if an IMU cal never has been done on the craft for example, could that trigger these kind of errors?

My main Phantom has had a hard working life and never had a compass or IMU calibration.
It flies perfectly.

In my case i also had a message saying “IMU encounters heading exception, please switch to Atti mode if craft behaves abnormally”
That message came together with the Yaw error, speed error and compass error.

The heading exception is because the IMU was having trouble matching conflicting data from the compass and GPS.
The compass data indicates the drone has moved in a certain direction but GPS position data gives a different answer.
Since there are error messages regarding compass/yaw errors and GPS is very reliable, the cause is bad compass data.

 

[The Phantom]

The heading exception is because the IMU was having trouble matching conflicting data from the compass and GPS.
The compass data indicates the drone has moved in a certain direction but GPS position data gives a different answer.
Since there are error messages regarding compass/yaw errors and GPS is very reliable, the cause is bad compass data.

Okay I see.
So those errors are most often not hardware issues, is that safe to assume.