Greetings!
I got my Mavic at the end of June, and have been having a blast with it this summer. Ive been flying for 4h28 min over 25 flights. I love flying it.

On three occasions I encountered a few Compass and IMU errors which have been putting the craft into ATTI-mode. I hope some insightful members will be able to help me figure out the cause. I've been lurking in this forum for a while and have been reading about issues caused by a bad compass calibration, and taking off from areas with magnetic inferference. I always check that my compass shows the right direction before and after take off.

My first encounter with ATTI-mode was 2m 24s into this flight:  http://app.airdata.com/main?share=qLnbAK

I recieved these warnings:
Warning: Compass Error. Exit P-GPS Mode
followed by
Warning: [IMU]heading exception (In Flight) please switch to atti mode if craft behave abnormally (Using)

The Mavic drifted slowly with the wind, but I had no difficulties controlling it. I didnt notice anything abnormal with the controllers before or after the warnings. The flight record on the DJI Go4 app seems to shows the correct orientation and movement of the drone until it suddenly goes into atti-mode.

I did an IMU Calibration and tried flying it a bit more with no issues until 4 flights later, when the same thing happened while I was flying in sport mode: http://app.airdata.com/main?share=Nofsou
(Ignore the Mobile device CPU fully loaded warnings. I found out that they were related to a full cache on my iPhone 6 Plus)
Still no issues controlling the Mavic, so I tried flying a bit more until it happened again in the same flight. After this flight i did a clean compass calibration on a field of grass. (Yes, I even took off my wedding ring ;) )

Then it happened again 10 flights later, also during sport mode: http://app.airdata.com/main?share=bznsqR.

Ive been flying more or less in the same area without any issues between these flights.Does anyone have any idea what could cause this? Bad Calibration? Magnetic interference in the general area?

I also uploaded the flights to Phantomhelp.com

Flight 1: http://www.phantomhelp.com/LogViewer/6NQF56BJESGHQ2ZXNW7J/ (Phantomhelp does show a few more compass errors than the DJi GO4 app and Airdata in this flight.)
Flight 2: http://www.phantomhelp.com/LogViewer/SB29P4AUNNVYNUUL9JJD/
Flight 3: http://www.phantomhelp.com/LogViewer/AZL17STM5AFQ5IEDR725/

(Please note that I am not blaming anything on-, or think i have a faulty Mavic just yet. The controls have been responsive and good at all times. Im just trying to learn and figure out what's going on. I haven't had any time to recalibrate and fly the done somewhere else after my holiday ended. I will try recalibrate everything and fly in a different area when I get the chance.)

And then i discovered a "hidden" No-Fly Zone Warning:
When looking through the "Warnings" section in the DJi Go app i also discovered this warning, which appeared prior to all of the compass errors mentioned above:
"Current RTH route will pass a No-Fly zone. Pay attention to the aircraft's position to avoid RTH failure." This warning -did not- show up during the flights, or appear when playing back the flight log in the DJI Go4 app. I only became aware of them when looking at "Warnings" log.
Also, There was no "No-Fly zone" close to where I was flying, so im guessing this is a bug with the app.

Does anyone have any idea what could cause this?

Based on where the flights occurred I suspect this might be another case of Mavic compass problems in areas where there's a high magnetic inclination. There have been several other cases of this reported lately (for example, here and here) but unfortunately I'm not aware of any solution to it from DJI or otherwise.

Whether it is the same problem or not we'll be in a better position to know what's going if we can take a look at the DAT files from the flights where this occurred, so please upload them someone will analyze them. The DAT files are stored on the Mavic itself and the instructions for extracting them are here. The correct file will have a time stamp that corresponds to when the flight occurred and will be at least tens of megabytes in size. Once you've retrieved the DAT file, upload it to DropBox or a similar service and provide a link in this thread.

Is compass calibration successful when the errors appear? May I have a screenshot of the Compass interface?

DroneFlying Posted at 2017-8-2 04:02
Does anyone have any idea what could cause this?

Based on where the flights occurred I suspect this might be another case of Mavic compass problems in areas where there's a high magnetic inclination. There have been several other cases of this reported lately (for example, here and here) but unfortunately I'm not aware of any solution to it from DJI or otherwise.

Thank you for your reply and willingness to look into my case.

I hope i uploaded the correct flight Dat files. They can be found here:
https://www.getsky.no/p/get-9907 ... b78ac7c1cea1f894f7b (Edit: I just realized that the interface is in Norwegian. The yellow button that says "Last ned alle" translates to "Download all". Pressing it will download all files.)

I uploaded the ones with a timestamp closest to the take-off time.

It is an interesting theory about the high magnetic inclination.
I dont live that far north, but was there on holiday. We'll see if it still happens (in Oslo, 10° further south) when i get the chance to fly again.

DJI Susan Posted at 2017-8-4 02:33
Is compass calibration successful when the errors appear? May I have a screenshot of the Compass interface?

The compass calibraton completed successfully. I did not get a prompt or error telling me to do the calibration, but did it after the Compass error during flight.
I did not take a screenshot at the time, but both bars were green before and after the calibration.

Paddyralph Posted at 2017-8-4 12:38
Thank you for your reply and willingness to look into my case.  

I hope i uploaded the correct flight Dat files. They can be found here:

I've looked at the DAT files and it does look similar to those other cases I mentioned, and with an inclination of almost 79° it at least superficially matches their circumstances.

As you can see in the graph below from "1st Flight" (FLY019.DAT), the compass fluctuations (shown in blue) seem exaggerated relative to the rotation indicated by the gyro (green). For example, at around 120 seconds you commanded the aircraft to yaw left and the gyro indicates it rotated by about 40° but the compass changes by about 60°. And you can see that a similar event occured at about 133 seconds into the flight.

Again, I'm not aware of a solution to or workaround for this problem but DJI might so if you expect to fly in that area again you should contact them about this first, and maybe still should even if you don't expect to fly there again, as it may helpful for them to see another example of this behavior. In any case, I know you mentioned this isn't your usual flight location, and if you're normally flying significantly farther to the south from where this occurred I doubt you'll encounter the problem again.

Paddyralph Posted at 2017-8-4 12:40
The compass calibraton completed successfully. I did not get a prompt or error telling me to do the calibration, but did it after the Compass error during flight.
I did not take a screenshot at the time, but both bars were green before and after the calibration.

Noted with thanks! I would recommend you to test the performance in another location without interference and keep an eye of compass interface. If no helps, I'm afraid that you may consider send it in.

Got the same bug, but my drone drifted pretty hard, luckily I landed it. Guys from support told that it happened because of interference... Hope so, but it was first time with me, and the place wasn't specific...
Hope DJI will find the problem!!!

Looks like it happened just in the beginning of the flight. Where did you take off? Was it concrete with steel bars or any other metallic surface? Neva embankments can have some reinforcing metal poles in them to keep the shoreline in the marshy landmass below.

BumblerBee Posted at 2017-8-8 05:24
Looks like it happened just in the beginning of the flight. Where did you take off? Was it concrete with steel bars or any other metallic surface? Neva embankments can have some reinforcing metal poles in them to keep the shoreline in the marshy landmass below.

It was concrete, maybe it is reinforced inside... Probably..
But I had 4 flights that day, 3 of them was absolutely normal, all the time I took off from the same place..
And I had no warnings at all...
I thought if there is some kind of interference and compass or imu get affected you will be noticed about that!
Is it right?

NikoT Posted at 2017-8-8 11:16
It was concrete, maybe it is reinforced inside... Probably..
But I had 4 flights that day, 3 of them was absolutely normal, all the time I took off from the same place..
And I had no warnings at all...

Go to the same spot, start the aircraft, but don't take off. Check the sensor readouts, especially that of compass (Main controller settings -> Advanced Settings -> Sensors). Check which of the two is in use and if it's in the green zone.

I usually do that sensor check as part of my pre-take-off check list.

BumblerBee Posted at 2017-8-8 23:36
Go to the same spot, start the aircraft, but don't take off. Check the sensor readouts, especially that of compass (Main controller settings -> Advanced Settings -> Sensors). Check which of the two is in use and if it's in the green zone.

I usually do that sensor check as part of my pre-take-off check list.

Cmon man)) For sure I checked it after the incident, both of compass and imu were green..

Ok, same problem for me.
[img]https://forum44.djicdn.com/data/attachment/forum/%5BURL=https://www.hostingpics.net/viewer.php?id=392735IMG2495.png%5D[/URL][/img]

After a calibration of the IMU and the compass, everything seems to be working properly, Ouf…