DroneFlying Posted at 2017-7-26 11:56
If you upload the DAT file from a flight where this occurred I'll take a look and see if I can figure out what might have happened.

PM'ed the dat

eyeloveteeth Posted at 2017-7-27 12:09
do you guys suggest doing compass calibration everytime?

No, you shouldn't calibrate the compass before every flight. Just make sure you do it right once and then don't calibrate it again unless you're prompted to do so or until you otherwise have a good reason to think it needs a new one.

Dronulator Posted at 2017-7-27 15:48
PM'ed the dat

Ok, I'll take a look and see what I can find.

Dronulator Posted at 2017-7-27 15:48
PM'ed the dat

I looked at it and wound up consulting with BudWalker, partly because he's more knowledgeable but also because I wanted confirmation of what I suspected, which is that it looks somewhat similar to a couple of other cases we've seen recently (here and here) where odd compass behavior occurs.

The common thread seems to be that these occur in locations of high magnetic inclination (about 71 in your case), and the best theory I know of is that the Mavic's compass just isn't effective at handling the lack of precision that necessarily occurs to some extent at these locations.

If you look at the graph below, you'll notice that magYaw (compass reading in blue) starts to decrease significantly at around 376 even though the gyro (in green) indicates only a much smaller amount of rotation. This produces a YAW_ERROR_LARGE (the pink shaded area), and you can see -- most obviously starting around 388 -- that the compass continues to show a significantly larger change in yaw than the gyro detects.

In other words, it appears that the compass fluctuations are out of proportion relative to the change in heading that actually occurred, and it's probably significant that the compass seems to overreact the most when the aircraft seems to be headed more or less due south at around 388.

Since you knew enough to extract and look at the DAT file I'm guessing you've already thought to try a compass calibration, but if you haven't already tried that I'd recommend doing one to see if it helps. If a compass calibration doesn't help and the problem persists you should try contacting DJI support about this and hopefully they'll have more insight into why it's happening and a solution that will help. Anyway, good luck and please do let us know how this turns out, even if it's only to say that the problem still occurs, because I'm always interested to hear the outcome in cases like this.

Thanks for the immense help! Ok, i calibrated compass, following all the necessary precautions. Sent it to a mid-range wp flight today. Returned again. Same thing happened Although i flew around that  location numerous times with no problems. Also tried to reproduce the issue while in RC range. Nope, works great that way.

Add: next day, flight to same area - same result. Will continue testing.

Dronulator Posted at 2017-7-31 04:36
Add: next day, flight to same area - same result. Will continue testing.

I didn't really expect the compass calibration to fix the problem since both of the other two people who experienced this had done calibrations before encountering the behavior. I'd suggest that you contact DJI about this problem and see if they have a solution or at least more information on what to try.

Hi Gents!

Two days ago I was out on flying the Mavic Pro two times and after a take off I get the warning "Magnetic Field interferance. Exit  P-GPS Mode."
Right after this message displayed for just a few seconds the Mavic took a life of its own and  it started flying away at top speed at first time or its flight
become unpredictable in the second time. Satellite count was around 15-17.   
Moreover when I was able to get control (in first time) and push the button landing I was unable to saw him or find in the map, it shows the same position where
AC was take off. It toke around 1 hour for me and my find it on the road in 300 mts from the place of take off.

Could you please explain to me what was the problems and how to avoid such situations?

The ling for the flight data is as follow

Will highly appreciate your suggestion and recommendations.

fans3fc79d84 Posted at 2017-8-23 09:54
Hi Gents!

Two days ago I was out on flying the Mavic Pro two times and after a take off I get the warning "Magnetic Field interferance. Exit  P-GPS Mode."

I just quickly glanced at the (FLY115.DAT) file and it looks like your launch site was geomagnetically distorted. It appears from the coordinates in the file that you were over water in or near a place where large ships are sometimes docked. Would I be correct in guessing that you took off from a ship containing a large quantity of steel? If so, that would have been the cause of the magnetic distortion that affected your Mavic's compass and made it go into what I call BATTI mode when you took off.

DroneFlying Posted at 2017-8-23 10:51
I just quickly glanced at the (FLY115.DAT) file and it looks like your launch site was geomagnetically distorted. It appears from the coordinates in the file that you were over water in or near a place where large ships are sometimes docked. Would I be correct in guessing that you took off from a ship containing a large quantity of steel? If so, that would have been the cause of the magnetic distortion that affected your Mavic's compass and made it go into what I call BATTI mode when you took off.

Hey Droneflying, something might be of interest to you regarding all the problems taking of in areas where compas interference can occur. In the new firmware for Spark " I don't know if it was included in new Mavic firmware " they have introduced a new failsafe for compass problem on the ground, your AC will now be restricted to height of 5 metres until your compass comes right, as usual no mention of it in the new firmware so maybe a bit of beta going on. I'll leave you link below to the first case I've seen of this happening, it certainly would be a good move if it works. Watch out for it appearing on Mavic.

https://forum.dji.com/forum.php? ... &fromuid=260008

DroneFlying Posted at 2017-8-23 10:51
I just quickly glanced at the (FLY115.DAT) file and it looks like your launch site was geomagnetically distorted. It appears from the coordinates in the file that you were over water in or near a place where large ships are sometimes docked. Would I be correct in guessing that you took off from a ship containing a large quantity of steel? If so, that would have been the cause of the magnetic distortion that affected your Mavic's compass and made it go into what I call BATTI mode when you took off.

Thank you for your feedback!

Yes, I took of from the deck of the steel vessel. But before take off I made calibration of magnetic compass and waited when the GPS signal become a strong and constant.

fans3fc79d84 Posted at 2017-8-24 21:39
Thank you for your feedback!

Yes, I took of from the deck of the steel vessel. But before take off I made calibration of magnetic compass and waited when the GPS signal become a strong and constant.

Calibrating in a situation like that won't help; you have to make sure your Mavic is moved away from the source of interference (steel in this case) before you take off. Hand launching isn't normally something I do or recommend but it probably would have been a better choice in this case.

DroneFlying Posted at 2017-5-15 09:41
Technically you can probably take off from the sidewalk if you avoid being too close to the rebar, which is laid out in a grid and has gaps; I've done it myself many times without any problems. The trick is just to make sure that you aren't seeing the "Magnetic interference" message I mentioned (or the icon pointing in the wrong direction as BudWalker said) before you take off. If you do see that message just move the aircraft a short distance away until the message is no longer displayed.

But yes, the safest and simplest approach is just to avoid the sidewalk altogether and use a landing pad over a spot where you know there's no metal. That's my preferred approach and is what I do most of the time; others advocate hand launching, but it's not something I personally recommend.

Hello.

My landing pad is a nylon material that has a collapsible ring that, when folded on to itself, reduces its size dramatically. Unfolded it is 32", can that metal ring be enough to trigger the magnetic interference warning?

Is there a way to read a magnetic interference level from the DJI Go App? How close or how much metal constitutes the need to move the take off point?

Thank you and have a great day, Rick.

R_Adams Posted at 2017-8-25 09:34
Hello.

My landing pad is a nylon material that has a collapsible ring that, when folded on to itself, reduces its size dramatically. Unfolded it is 32", can that metal ring be enough to trigger the magnetic interference warning?

My landing pad is a nylon material that has a collapsible ring . . . can that metal ring be enough to trigger the magnetic interference warning?

You mean something like this? No, I use the same thing and it isn't a problem.

Is there a way to read a magnetic interference level from the DJI Go App? How close or how much metal constitutes the need to move the take off point?

You can always check your compasses in the Go app by choosing Main Controller Settings > Advanced Settings > Sensors, and then clicking on "Compass", but it shouldn't be necessary. In theory the Go app should warn you when there's a problem, but in practice it's not clear that it always does, so the best thing is just to avoid places where you know there is or might be ferrous metals (such as concrete) when taking off.

One simple and effective test is just to check the aircraft icon prior to taking off and making sure that the aircraft / arrow displayed in the Go app's map is pointing in the direction your Mavic is really facing. If the two are different then it's probably because you're near some metal and should move to a different location before taking off.

DroneFlying Posted at 2017-8-25 13:33
My landing pad is a nylon material that has a collapsible ring . . . can that metal ring be enough to trigger the magnetic interference warning?

You mean something like this? No, I use the same thing and it isn't a problem.

Thank you for the reply.

Yes, that image of a folded landing pad is what I meant. The first time I opened it I discovered just how thick the spring ring was when it clipped my nose.

I watched the video of a pilot that took off close to a ship near a steel lift bridge. He believed that he lost contact because he calibrated his compass on a pier with steel and concrete. If he rotated the Mavic while standing, I would assume about five feet off the ground; was that close enough to the steel pier and rebar in the concrete to affect the calibration? Some felt the ship contributed to the interference. If it possible to calibrate the compass in these situations, how was it he could still take off and then discover the compass was malfunctioning? I was hoping that there might be a way of quantifying just how much steel is too much if the DJI Go App only reports if there is sufficient interference present?
In any case, it is just one more thing I'll remember to be a safe pilot and control the aircraft responsibly.

Thank you very much, have a great day, Rick.

hallmark007 Posted at 2017-5-16 14:46
As I explained to you earlier your Aircraft didn't fly away it went into Atti mode and if you read your logs it responded to your stick movements, you chose to raise your aircraft which was the right move, but while you were doing this your aircraft was drifting in Atti mode if you had used other stick movements you could have controlled your aircraft but Atti mode is not easy, and you were lucky you regained gps and stability.
My conclusion is the environment you were flying in was effecting your aircraft where the interference was coming from I do not know, but it was there.

nope, after losing video i walked over to check on the aircraft assuming it was hovering according to the flight history video, i had no control at all and as some pointed out the flight records show this with errors.

The records clearly show it flew away, let me know how this happened as my remote had lost connection,  no video feed, no more info on the FIND MY DRONE map other then that last point i had in site.

the DJI  engineer explained that the last drone scenario was the remote, but had no idea why the RTH function did not work.

This drone shows the same type of scenario but more flight info, including the distance from home, you would think it would return by itself if the battery went low no?  i tried hitting the RTH over an over and over for 5 mins, nada

BudWalker Posted at 2017-5-16 05:29
IMHO  fan18d204cd's incident was not a launch-from-a-geomagneticaly-distorted-site incident. If it had been then erratic flight would have occured immediately after launch. Also, these incidents occur because the switch to ATTI is not done as it should be. Typically, a compass error isn't declared.

The thing to note about this incident is that there was a SPEED_ERROR_LARGE at 524 followed by a YAW_ERROR_LARGE and then gpsHealth drop from 0 to 5 at 529. Finally, the switch to ATTI at 530. This could have been caused by a turbulence. The Flight Controller gives up and asks the pilot to do the navigating.

that .DAT file is  here i checked it.

your correct about the turbulence,  there was no way anyone could of controlled it in this state

realdeal Posted at 2018-2-25 12:47
nope, after losing video i walked over to check on the aircraft assuming it was hovering according to the flight history video, i had no control at all and as some pointed out the flight records show this with errors.

The records clearly show it flew away, let me know how this happened as my remote had lost connection,  no video feed, no more info on the FIND MY DRONE map other then that last point i had in site.

Check your logs again every stick move you made while in Atti mode was recorded and can be seen in how the aircraft moved at that time so your Aircraft was working fine in Atti mode you just couldn’t control it because you couldn’t see it .

eyeloveteeth Posted at 2017-7-27 12:09
do you guys suggest doing compass calibration everytime?

check it before take off and a min after, if it changes colors between yellow and orange bail out home!