Just saw the "compass error exit p-gps mode" flashing by while flying, should i worry?

[berisen]

Hi all! New guy from Sweden here that's just started flying! Happy to find his forum, seems to be a lot of good expertise in here and i feel like I could spend many hours of just reading old threads ?

And that brings me to my question. I have read a lot of crash-threads (i don't know why since it just spooks me up ) and particularly people with issues with crashes that seemed to be due to some sort of interference with the reedings from the IMU and Compass.

I got my MPP about a week ago and have had limited chance of flying due to bad weather but this weekend got me a few hours and it's a blast really, love it! I'm beginning to learn how to control it pretty good but i have a long way to go haha.

Anyway, yesterday I took it out to a lake for some flying and everything went well in normal mode but after playing around with the sport mode and some tough yaw-left/right and a few up's and down's I noticed this message "compass error exit p-gps mode" on the screen. It was there for maybe 1-2 seconds before going away and everything went back to "all green gps mode". I got this message once again a moment later and then I decided to pack up my stuff and return home to read more about this. I then found a couple of threads about crashes and fly-aways and other sad stuff.

Just to be sure, I re-did my calibration later that day in an open place without any stuff that could interfere and did a quick test runt and everything seemed fine and no errors so i guess I'm good?

I haven't gone through any logs yet but i just wanted to ask if I should be concerned about this or if this is normal behaviour? It's probably fine but always good to ask. Could it be due to interference in the area I was flying or "bad calibration"? It was a bit windy but nothing special really.

 

[Meta4]

Just to be sure, I re-did my calibration later that day in an open place without any stuff that could interfere and did a quick test runt and everything seemed fine and no errors so i guess I'm good?

I haven't gone through any logs yet but i just wanted to ask if I should be concerned about this or if this is normal behaviour? It's probably fine but always good to ask. Could it be due to interference in the area I was flying or "bad calibration"?

If your drone flies straight and hovers in place without slowly spiraling, its compass is properly calibrated and there's no need to recalibrate it

 

[berisen]

If your drone flies straight and hovers in place without slowly spiraling, its compass is properly calibrated and there's no need to recalibrate it

Thanks, good to know! It was steady before re-doing it so apparently it was unnecessary but I just wanted to be sure that there was no problem with the compass.

So, the gps error that i saw has nothing to do with the compass calibration?

Edit:
Is IMU calibration something you need to do after unboxing or should i only do this if prompted or if I notice any weird behaviour?

 

[Meta4]

So, the gps error that i saw has nothing to do with the compass calibration?

1. the compass was properly calibrated.
If it wasn't the drone would not have flown properly
2. We no information about the "gps error" you've mentioned so can't say anything about what it might have been or what caused it.
3. Recorded flight data might help to see what was going on during the flight.

Is IMU calibration something you need to do after unboxing or should i only do this if prompted or if I notice any weird behaviour?

Although some users do it, it's not required after unboxing.
If it was DJI would say so ... and they don't.
It would be very rare that you would ever have to recalibrate the IMU unless the drone is involved in a crash.

 

[berisen]

1. the compass was properly calibrated.
If it wasn't the drone would not have flown properly
2. We no information about the "gps error" you've mentioned so can't say anything about what it might have been or what caused it.
3. Recorded flight data might help to see what was going on during the flight.


Although some users do it, it's not required after unboxing.
If it was DJI would say so ... and they don't.
It would be very rare that you would ever have to recalibrate the IMU unless the drone is involved in a crash.

Ok thank you! I have uploaded the flight data for that specific flight on these links:

Dropbox

www.dropbox.com

Dropbox

www.dropbox.com

Dropbox

www.dropbox.com

Does these numbers tell you anything? On a closer look, it looks like every flight has these errors. Sometimes just a few seconds and sometimes a little more. Have never experienced any issues with flying though. I also noticed one error called "Yaw error" for a short period in one of the logs.

I'm just worried that I'll lose it due to a crash/drop down.

Is this normal behaviour or should I be worried? It flies just fine, no problems, no bad handling, super stable all the time but this error comes up briefly.

 

[Meta4]

I also noticed one error called "Yaw error" for a short period in one of the logs.
Is this normal behaviour or should I be worried? It flies just fine, no problems, no bad handling, super stable all the time but this error comes up briefly.

The flight you posted looks like this: DJI Flight Log Viewer - PhantomHelp.com
I see the compass error shows when you are within 2 metres of the launch point, so have to ask what is at the launch point?
Is there any obvious steelwork or large steel objects very close by?

And mention of a Yaw error is concerning.
It is important to ensure you are not launching from close to steel.
Never launch from a steel reinforced concrete surface.

 

[berisen]

The flight you posted looks like this: DJI Flight Log Viewer - PhantomHelp.com
I see the compass error shows when you are within 2 metres of the launch point, so have to ask what is at the launch point?
Is there any obvious steelwork or large steel objects very close by?

And mention of a Yaw error is concerning.
It is important to ensure you are not launching from close to steel.
Never launch from a steel reinforced concrete surface.

Ah I see. I actually launched from a wood table with a steel-frame and nearby there is a big frame for a big outdoor roofing structure for a dance course. The errors is indeed occurring close to the launch location.

Didn’t know that steel had so much impact on the compass but maybe that’s the explanation here.

I think I need to analyze my previous flights and see if there’s any presence of steel nearby when the compass error is there.

 

[Meta4]

Ah I see. I actually launched from a wood table with a steel-frame and nearby there is a big frame for a big outdoor roofing structure for a dance course. The errors is indeed occurring close to the launch location.
Didn’t know that steel had so much impact on the compass but maybe that’s the explanation here.
I think I need to analyze my previous flights and see if there’s any presence of steel nearby when the compass error is there.

The effect of the steel depends on the size of the steel object and how close it is to the compass.
There have been cases of launching from a timber deck or table but with the compass directly above steel bolts or frames that have caused problems.
You can also check before launching to confirm no problems with magnetic fields by ensuring that the red paper plane icon in the radar or map box is pointing to the same compass direction as your drone is.

 

[berisen]

The effect of the steel depends on the size of the steel object and how close it is to the compass.
There have been cases of launching from a timber deck or table but with the compass directly above steel bolts or frames that have caused problems.
You can also check before launching to confirm no problems with magnetic fields by ensuring that the red paper plane icon in the radar or map box is pointing to the same compass direction as your drone is.

So if I see this message briefly when flying over something I shouldn’t be too worried about it as long I’m not launching from a magnetically interfered area?

I went through some logs from a flight out in the open fields with no structures within miles and I only have a few compass errors in the logs, could it be something in the ground I flew close by that caused it?

Think I never had a totally clean log without any compass errors from a total of 10-15 flights.

 

[Meta4]

So if I see this message briefly when flying over something I shouldn’t be too worried about it as long I’m not launching from a magnetically interfered area?
I went through some logs from a flight out in the open fields with no structures within miles and I only have a few compass errors in the logs, could it be something in the ground I flew close by that caused it?
Think I never had a totally clean log without any compass errors from a total of 10-15 flights.

It's unlikely that anything you flew over on the ground would trigger a compass error.
The magnetic field strength drops off rapidly with distance and you'd have to be very close for there to be any effect.
You can get a feel for how this works by slowly descending toward a steel roof until you start to see the drone wander a little and maybe slowly spiral.
You have to get down almost a metre above teh roof to see it.
It's quite safe and you simply climb higher to see things get back to normal.

The big problems can come from powering on where the sensors get a false idea of where north is because of local magnetic effects at the launch spot.
If the steel is large/close enough, the compass will alert you and warn of a problem (compass error) and prevent launching.
But when the difference between the problem magnetic field and the earth's normal magnetic field is not enough for the drone to identify it that can cause a nasty surprise when you fly out of the magnetic influence.

 

[berisen]

It's unlikely that anything you flew over on the ground would trigger a compass error.
The magnetic field strength drops off rapidly with distance and you'd have to be very close for there to be any effect.
You can get a feel for how this works by slowly descending toward a steel roof until you start to see the drone wander a little and maybe slowly spiral.
You have to get down almost a metre above teh roof to see it.
It's quite safe and you simply climb higher to see things get back to normal.

The big problems can come from powering on where the sensors get a false idea of where north is because of local magnetic effects at the launch spot.
If the steel is large/close enough, the compass will alert you and warn of a problem (compass error) and prevent launching.
But when the difference between the problem magnetic field and the earth's normal magnetic field is not enough for the drone to identify it that can cause a nasty surprise when you fly out of the magnetic influence.

Thanks for the explanation! So these errors shouldn’t pop up mid flight really in normal conditions unless you are flying straight above something that could interfere? In my case, would it be a good idea to re-calibrate both IMU and Compass in a new location prior to my normal start location at home? As far as i understand, if done correctly it should be able to fix some of these errors?

Yes I’m worried about loosing the drone in case you haven’t noticed ?

 

[Meta4]

So these errors shouldn’t pop up mid flight really in normal conditions unless you are flying straight above something that could interfere?

The errors are probably related to your launch spot and normally you'd never see them in flight, unless you are really, really close to a large steel object (closer than you'd normally fly).

In my case, would it be a good idea to re-calibrate both IMU and Compass in a new location prior to my normal start location at home? As far as i understand, if done correctly it should be able to fix some of these errors?

Your drone probably doesn't need any recalibrating, just launching from a "clean" site.
Compass errors are warnings rather than something that needs fixing.
Recalibrating the compass doesn't "fix" anything.
It just measures the magnetic fields that are part of the drone.
They don't change (unless you modify the drone), so there should be no need to do it again.

Yes I’m worried about loosing the drone in case you haven’t noticed

That's common for new flyers.
There's a lot of things that could go wrong and it takes a while to learn about them all and how to make sure they don't cause a problem for you.

 

[berisen]

Here is another flight from the same location (same day) that I have uploaded:

DJI Flight Log Viewer | Phantom Help

Upload and view flight logs from your DJI drones

www.phantomhelp.com

As you can see, here is also the yaw-error that i was talking about.

Do you see anything worrying about this log or is it just because of a bad location for flying?

Edit:
Just saw your reply @Meta4 . Thanks for the help.
I guess the same thing goes for this log. Same takeoff location in this one (don't remember if it was on or right next to steel table though but nearby).

 

[Meta4]

Here is another flight from the same location (same day) that I have uploaded:
As you can see, here is also the yaw-error that i was talking about.
Do you see anything worrying about this log or is it just because of a bad location for flying?

Here's that flight data in an easier to see format: DJI Flight Log Viewer - PhantomHelp.com
The yaw error showed up at 11:03.
Usually they happen sooner after launching, maybe the difference between north and the false north your drone got was not enough to cause a serious issue.
A bad yaw error usually results in loss of the drone.
The compass errors are probably related to the yaw error rather than the more common type.
Being careful to avoid launching from magnetically "dirty" sites is the best way to prevent yaw error situations.

 

[berisen]

Here's that flight data in an easier to see format: DJI Flight Log Viewer - PhantomHelp.com
The yaw error showed up at 11:03.
Usually they happen sooner after launching, maybe the difference between north and the false north your drone got was not enough to cause a serious issue.
A bad yaw error usually results in loss of the drone.
The compass errors are probably related to the yaw error rather than the more common type.
Being careful to avoid launching from magnetically "dirty" sites is the best way to prevent yaw error situations.

Thanks, I edited my post with your link instead since airdata messed up the whole page layout for some reason.

I guess I won't be able to figure out the exact reason why i got these compass errors but I'll just have to believe that it was due to "dirty compass" location. I have tried to look at the dat-files but that doesn't make me any wiser. It takes some skills to be able to read these and I don't have them unfortunately . I'm just worried that there is something wrong with the drone and that it will freak out at some point and just crash. I've read all too many of these stories on these forums to feel comfortable but the best thing is probably to keep flying with caution and be observant for any more warnings/errors.

Why did I ever start digging into this? ?

Edit:
Here's a link to a flight that should be in a very "clean" location but it stills has some of these errors:

DJI Flight Log Viewer | Phantom Help

Upload and view flight logs from your DJI drones

www.phantomhelp.com

No metal/concrete or anything in a very long distance and i'm taking off from a gravel road. Shouldn't have any errors in a flight like this right?

 

[berisen]

Just a little update here.

I did an IMU calibration and I think that it might have solved my problems. No more errors (no more compass/IMU/yaw errors) in the logs since and I've done a couple of flights in different locations and so far so good. Fingers crossed!

 

[Meta4]

I did an IMU calibration and I think that it might have solved my problems.

Calibrations don't cure yaw errors because yaw errors are caused by powering up the drone in a magnetic field and then flying out of it.

 

[berisen]

Calibrations don't cure yaw errors because yaw errors are caused by powering up the drone in a magnetic field and then flying out of it.

The strange thing here though is that I kept getting this error in multiple locations no matter what I did but since calibrating the IMU and compass I haven't seen any errors at all when flying in the exact same locations. I'm glad that the problem seems to have gone away but on the other hand I would very much like to understand why

Got some great help from @sar104 and he suggested that it might be related to a biased z-axis rate gyro but I'm still not sure. I had some unusual discrepancies between IMU and magnetic yaw when looking through the DAT-files but it's far from easy to understand this stuff for a beginner ?