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Mavic constant YAW and weak gps errors
1387 27 2018-7-26
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SepiMeister
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Hello,

I having some issues with my Mavic. It used to work like a charm but now i face constant yaw and weak gps signal errors.  IMU is calibrated with a cool unit and did the compass calibration on a grassy field. Also the lastest firmware is updated.

Could it just be drone picking up interference from the spot i take off? If so it seems i can only take of from open fields. There also seems to be a pattern. Shortly after take off (approx 1-2min) errors pop up and forces the drone to ATTI. After a while it goes back to P-GPS.  Here is the log from last flight http://www.phantomhelp.com/LogViewer/IRZOEK7AD3TEDAS1Y0GS/


Im a bit scared to fly at the moment :s I can manage the drone in ATTI mode if there is no strong winds or im flying on open field Just wanted to ask if someone can tell me if this is just a pilot error or is there a possibility it is a defected unit.

Thanks!
2018-7-26
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gnirtS
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Looking at that briefly, it doesnt seem to be GPS kicking it into ATTI.  Its the yaw error and compass errors.  
To me it looks like IMU and/or compass calibration or faults.
Just to narrow things down, can you DO to an open field and recalibrate both those?  You're quite low - it COULD be localised magnetic interference or similar in the area.
2018-7-27
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SepiMeister
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gnirtS Posted at 2018-7-27 02:48
Looking at that briefly, it doesnt seem to be GPS kicking it into ATTI.  Its the yaw error and compass errors.  
To me it looks like IMU and/or compass calibration or faults.
Just to narrow things down, can you DO to an open field and recalibrate both those?  You're quite low - it COULD be localised magnetic interference or similar in the area.

Good point. I'll try calibrating the compass again. Should i calibrate the IMU as well? Kinda hard to do IMU on open field where you dont have a place to level. So doing that indoors should be ok, right, ?
2018-7-27
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msinger
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I don't think calibrating the IMU is going to help, but it would be okay to calibrate the IMU indoors since it's not negatively affected by magnetic metal objects.
2018-7-27
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gnirtS
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Id do the IMU indoors on the most level surface you can find.  Magnetic has no effect on that.

Compass is a little trickier, a few things can affect it - buried wires or cables, overhead cables, even phones in your pocket or wearing a chunky watch.  I always make sure im a good 10m from the tablet and RC when i do it (use the status light to see when to rotate etc).

Once calibrated check the sensor status in the app to check they roughly agree with each other and well in the green area.
2018-7-27
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SepiMeister
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Thanks for the advice. Calibrated the IMU and compass. Little bit yaw movement when hoovering but no compass errors this time.

I’ll keep testing in different locations
2018-7-27
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gnirtS
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SepiMeister Posted at 2018-7-27 08:51
Thanks for the advice. Calibrated the IMU and compass. Little bit yaw movement when hoovering but no compass errors this time.

I’ll keep testing in different locations

IS it actual yaw movement or gimbal drift?

A lot of MPs it seems have what seems to be yaw movement but on examining the logs its the gimbal slowly drifting to the side instead.

Can you physically see the drone rotate with your own eyes or is it the screen picture moving?
2018-7-27
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SepiMeister
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MP was too high to see that little movement. Could be gimbal drift too. Last time i had same drift i callibrated the IMU and the drift was gone, so i just thought it would be yaw related.  So MP does that gimbal drift and it is pretty much normal?
2018-7-27
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DJI Stephen
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Hi. For additional reference, I will be posting the official DJI Video Tutorial on how to calibrate the IMU properly. Please keep us posted on the issue that you are having.

2018-7-27
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gnirtS
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Not everyones drifts for sure but a board search here and elsewhere turns up quite a lot.  Mine does it.  Sometimes all flight, sometimes part of the flight, occasionally not at all.
Its currently in an "all the time" phase which makes straight line flying quite hard.
The gimbal is effectively a rubber band so not exactly a precision machine.
2018-7-27
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SepiMeister
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Okay so, IMU calibrated, compass calibrated. Losing compass during the flight reduced to 1 out of 5 flies.

But! Mavic doesn’t fly straight and gimbal drift is terrible. I really don’t know what to do here.

2018-7-30
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gnirtS
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Upload the logs from the last dodgy flight so we can see?
2018-7-30
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SepiMeister
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gnirtS Posted at 2018-7-30 09:45
Upload the logs from the last dodgy flight so we can see?

Yes, srry was on my way to home from flying.

Here is the log http://www.phantomhelp.com/LogViewer/LEELI7M6GP8AGW7X2MVP/
2018-7-30
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SepiMeister
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https://www.dropbox.com/s/lqtzmltuyl0vc2j/BLNW8279.MOV?dl=0  Gimbal drift

https://www.dropbox.com/s/cxpju6xiwxn2nv0/GOGG6001.MOV?dl=0 Fly record from app

https://www.dropbox.com/s/wykxinsfep63fmn/QYUY5867.MOV?dl=0 Mavic goes to left
2018-7-30
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gnirtS
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The actual flight log .txt files are needed from the tablet not the videos.
Those will have data and errors.
2018-7-30
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SepiMeister
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gnirtS Posted at 2018-7-30 10:01
The actual flight log .txt files are needed from the tablet not the videos.
Those will have data and errors.

http://www.phantomhelp.com/LogViewer/LEELI7M6GP8AGW7X2MVP/   <- this not the right one?
2018-7-30
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HedgeTrimmer
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gnirtS Posted at 2018-7-27 10:46
Not everyones drifts for sure but a board search here and elsewhere turns up quite a lot.  Mine does it.  Sometimes all flight, sometimes part of the flight, occasionally not at all.
Its currently in an "all the time" phase which makes straight line flying quite hard.
The gimbal is effectively a rubber band so not exactly a precision machine.

Has your Mavic always had on/off drifting problem?  
2018-7-30
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PS013
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I noticed that you are in Finland. Do you know that aurora borealis will perturb GPS signal as well as you compass. So you may want to check the solar weather  ( http://en.ilmatieteenlaitos.fi/auroras-and-space-weather )
2018-7-30
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SepiMeister
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HedgeTrimmer Posted at 2018-7-30 10:17
Has your Mavic always had on/off drifting problem?

Not that i remember. It was flying very straight and nice the first month.  Then i had 2-3 weeks off, didn't fly at all.  Next time i went out to fly compass errors started, after that i noticed the gimbal drift and it feels like i can't fly straight anymore.

I was inspecting my mavic 5 min ago and noticed something.  The gimbal plate is broken - https://imgur.com/ohAzXN0  that little "clamp" is broken. Could this be the reason behind unsual behaviour? :/
2018-7-30
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SepiMeister
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PS013 Posted at 2018-7-30 10:22
I noticed that you are in Finland. Do you know that aurora borealis will perturb GPS signal as well as you compass. So you may want to check the solar weather  ( http://en.ilmatieteenlaitos.fi/auroras-and-space-weather )

Yes, thanks for the link. Today was low probability of auroras (0.01 - 0.02). Yet still some compass errors occured.  But it still could be something to consider when living this up north.
2018-7-30
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gnirtS
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Is that a new file after you calibrated?
A brief skim of the logs show it got compass interference shortly after or during takeoffand errors come at a low altitude of 5-6ft.
That to me hints it could be something metallic or electrical.  Any rebar, buried cables, power lines, metal pipes or anything around the take off point?  It comes back at the end in the same location.

Not looked in too much detail though but that one at least appears to me it was miscalibrated at takeoff so never really recovered.
Although, the fact its not turning around or spinning with no controller input is confusing.  Normally a screwed up compass will do a toilet bowl shape.
2018-7-30
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SepiMeister
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gnirtS Posted at 2018-7-30 11:05
Is that a new file after you calibrated?
A brief skim of the logs show it got compass interference shortly after or during takeoffand errors come at a low altitude of 5-6ft.
That to me hints it could be something metallic or electrical.  Any rebar, buried cables, power lines, metal pipes or anything around the take off point?  It comes back at the end in the same location.

Compass was calibrated few days ago. After that i had 0 compass errors (4 flights). Log file was from today.  I took off from a gritty parking lot.  Nearest metal was a car about 10 meters  away and some phonelines 20m away. But i could never know if there is cables going through grit below.

Shouldn't mavic tell me if there is interference?

Im a bit lost now with the Mavic. I accept the fact that pilot errors happen to newbies like me all the time and i'll try to avoid them best i can by trying to take off from a spot no metal or anything  nearby which could interference with the compass.

Probably just going to have to send Mavic for gimbal vibration absorbing plate repair also.

2018-7-30
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gnirtS
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It'll warn of interference if it detects there is some but it cant always detect.

Have you had it launching from other places (grass fields, or hand launch etc) ?

Its just a bit suspicious to me the errors only seem to happen in one place.
2018-7-30
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SepiMeister
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I’ve lauched it from grassy places, worked fine.

It seems that, gritty launching places always follows with compass errors and asphalt too.

Maybe it is just better to take off from grass.

Just weird too see videos where people take off similar places to mine, but not having any problems.

2018-7-30
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gnirtS
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Grit and asphalt on their own wont cause errors unless theres something buried nearby.
You can roughly test an area with a mobile phone, lots of compass apps display the field strength in micro tesla.  It should be fairly constant.  If you go somewhere and that reading changes dramatically theres some source of interference there.
2018-7-30
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SepiMeister
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I use the Magnitude app. I’ll sweep the area with my app next fly and see if it will repeat the compass error. Thanks!
2018-7-30
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gnirtS
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Try hand launch just to eliminate.
Its hard to narrow down an intermittent issue.  Could be a fault, might not be.
2018-7-30
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SepiMeister
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Mavic is now in Holland for a " Gimbal Vibration Damping Module, Gimbal Control Board " repair. But i think DJI is not going to inspect the drone for compass and not flying straight issues even tho i asked and DJI support said they will check the drone if i send it for repair.   

They sent an e-mail for repair quote but not a single word about other problems.  Maybe they didn't find anything wrong but they should at least tell that to the customers.

2018-8-8
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