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"In flight, working IMU encounters heading exception."
634 17 2018-10-30
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dwin1977
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I got this warning last week but have had several istances. It seems unsafe to fly. I'm sure this is posted but I've yet to find resoluthion. "In flight, working IMU encounters heading exception. Please switch to atti mode if craft behave abnormally". Meanwhile it is spinning and drifting horribly. I'm too busy to read all of the warnings just to keep it in the air. I was at 2084 ft away and 265.8 ft up.Then again at 1441 ft away and 121 ft up. Same flight.
I also get terrible sudden left yaw with no stick input randomly. Could both of these be caused by one root problem?
2018-10-30
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hallmark007
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This usually happens when there is conflict between compass and gps, was the area you were flying in or the ground you took off from prone to magnetic interference.

The best way I can explain this is. If you put your Aircraft on the ground in normal circumstances, start it up, then lift it up and turn it 90 degrees to the right both your compass heading and IMU will both move together 90 degrees and no problems.
If you put your Aircraft on the ground and there is magnetic interference only the heading of your compass will change, your aircraft will still take off. But when it clears magnetic interference compass will then move to correct heading which you would think was great. But No, what happens is IMU is then conflicted and confused because of this sudden movement by compass, so you receive IMU exceptional heading warning, your aircraft cannot deal with data conflict so decides to switch to Atti mode dropping gps in favour of compass simply because aircraft can fly without gps but not compass.

While I can’t be certain you picked up interference from the ground or surrounding area it is the most common cause.
2018-10-30
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hallmark007
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This usually happens when there is conflict between compass and gps, was the area you were flying in or the ground you took off from prone to magnetic interference.

The best way I can explain this is. If you put your Aircraft on the ground in normal circumstances, start it up, then lift it up and turn it 90 degrees to the right both your compass heading and IMU will both move together 90 degrees and no problems.
If you put your Aircraft on the ground and there is magnetic interference only the heading of your compass will change, your aircraft will still take off. But when it clears magnetic interference compass will then move to correct heading which you would think was great. But No, what happens is IMU is then conflicted and confused because of this sudden movement by compass, so you receive IMU exceptional heading warning, your aircraft cannot deal with data conflict so decides to switch to Atti mode dropping gps in favour of compass simply because aircraft can fly without gps but not compass.

While I can’t be certain you picked up interference from the ground or surrounding area it is the most common cause.
2018-10-30
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dwin1977
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hallmark007 Posted at 2018-10-30 15:02
This usually happens when there is conflict between compass and gps, was the area you were flying in or the ground you took off from prone to magnetic interference.

The best way I can explain this is. If you put your Aircraft on the ground in normal circumstances, start it up, then lift it up and turn it 90 degrees to the right both your compass heading and IMU will both move together 90 degrees and no problems.

This is great information. Thank you. It seems it's all about where the take off originates. It would be hard to determine magnetic information so I guess it's trial and error? And these errors didn't appear until much further away in the flight. Not at point of origin. Signed, Confused still. :-)
2018-10-30
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hallmark007
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dwin1977 Posted at 2018-10-30 15:22
This is great information. Thank you. It seems it's all about where the take off originates. It would be hard to determine magnetic information so I guess it's trial and error? And these errors didn't appear until much further away in the flight. Not at point of origin. Signed, Confused still. :-)

They won’t always give warning on take off, so it’s no harm to check compass values in your app before you take off, values should be green smaller the better, you can also check compass by checking small red triangle bottom left corner in your telemetry, it should be on the same heading as your craft, if it moves on start up it’s likely you may have a problem.
2018-10-30
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hallmark007
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dwin1977 Posted at 2018-10-30 15:22
This is great information. Thank you. It seems it's all about where the take off originates. It would be hard to determine magnetic information so I guess it's trial and error? And these errors didn't appear until much further away in the flight. Not at point of origin. Signed, Confused still. :-)

http://www.phantomhelp.com/LogViewer/Upload/

You could upload your log, just go to link above follow instructions.
2018-10-30
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dwin1977
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hallmark007 Posted at 2018-10-30 15:46
They won’t always give warning on take off, so it’s no harm to check compass values in your app before you take off, values should be green smaller the better, you can also check compass by checking small red triangle bottom left corner in your telemetry, it should be on the same heading as your craft, if it moves on start up it’s likely you may have a problem.

Just saved that as another takeoff checklist for my Air. Thank you again!
2018-10-30
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JJBspark
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dwin1977 Posted at 2018-10-30 15:52
Just saved that as another takeoff checklist for my Air. Thank you again!

Hi Dwin,

Just to be more clear about that red arrow wich indicates heading of your drone.
1. If it is not pointing the same direction of the craft most like your mobile device compass need to be calibrated.
2. If the read arrow is not steady indicating (correct hdg or not correct hdg, see point 1) than there is a good chance that there is a magn interference at take off point.

Red arrow gets its info from your craft.
Outer ring compass (sets the North marking) gets its info from your mobile device.

In sutiation 1; its safe to fly but not smart as you cannot use the little compass in the app. (well, arrow pointing home brings craft back but to see easily where your drone is...pfff, needs lots of my brainpower :-) )

In situation 2 ist not very wise to start flying.



cheers
JJB
2018-10-31
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Boffin
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There are several magnetometer apps online for both Android and IOS, just search.
Here is a linky to a typical example Magnetometer
Of course it depends whether your phone/tablet has such a sensor but most seem to be equipped with a magnetic sensing device nowadays
2018-10-31
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Sato Zoom 2
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hallmark007 Posted at 2018-10-30 15:46
They won’t always give warning on take off, so it’s no harm to check compass values in your app before you take off, values should be green smaller the better, you can also check compass by checking small red triangle bottom left corner in your telemetry, it should be on the same heading as your craft, if it moves on start up it’s likely you may have a problem.

Hallmark let me pick your brain if I can........
I often take off from a convenient area of a park that is paved asphalt (no rebar, zero compass interference).  However, the area is not level.  It's not terribly slanted I'd guess maybe no more than a 20 degree decline but definitely a noticeable unevenness.  My M2 seems to launch and fly fine from there.  Do you think launching from an uneven position could mess with the IMU somehow by starting unevenly then suddenly jumping to level flight?  Do you see any danger in launching this way?
2018-10-31
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hallmark007
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Sato Zoom 2 Posted at 2018-10-31 06:14
Hallmark let me pick your brain if I can........
I often take off from a convenient area of a park that is paved asphalt (no rebar, zero compass interference).  However, the area is not level.  It's not terribly slanted I'd guess maybe no more than a 20 degree decline but definitely a noticeable unevenness.  My M2 seems to launch and fly fine from there.  Do you think launching from an uneven position could mess with the IMU somehow by starting unevenly then suddenly jumping to level flight?  Do you see any danger in launching this way?

No I have often looked for a slight slant in the ground, simply because Mavic camera is so low to the ground. Technically yes the IMU has to work slightly harder to find correct attitude, but IMU in these aircraft are well capable, I always use test below both to check compass and IMU etc before taking off to the sky.


Tip To Help Avoid compass interference and crash.


1/ Never calibrate Compass unless prompted to.

2/ start AC leave until you receive enough gps lock ,

3/ if you get Compass interference turn off AC and move to another location,
without interference.

4/ In bottom left hand corner on your map you will see small red triangle, check to make sure that this triangle is pointing in the same direction (heading) as your AC, this will show good compass on the ground.

Raise AC to height of 8ft
Hover for 20 seconds
Fly forward 2ft
Backward 2ft
Left 2ft
Right 2ft
Up 2ft
Down 2ft
Yaw left
Yaw right
Each time returning to hover position
If you have a good horizontal each time, you will then know you have good GPS good IMU and good Compass, and your ready to fly.

This exercise takes less than 2 minutes and is worthwhile doing before every flight,
2018-10-31
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dwin1977
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hallmark007 Posted at 10-30 15:49
http://www.phantomhelp.com/LogViewer/Upload/

You could upload your log, just go to link above follow instructions.

http://www.phantomhelp.com/LogViewer/EX2XAQAJ98VN9FU9U5J1/

I hope I did this right. The two occurrences were between 1:50 and 2:11 into the flight.
2018-11-1
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hallmark007
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dwin1977 Posted at 11-1 09:44
http://www.phantomhelp.com/LogViewer/EX2XAQAJ98VN9FU9U5J1/

I hope I did this right. The two occurrences were between 1:50 and 2:11 into the flight.

Looking at your flight log , I would still say your interference began from launch, you launched from a driveway according to your log, driveways often have rebar and or electrical cables , because it cleared up very quickly would suggest that it was pretty low interference so not to serious, if your craft goes into Atti mode in order to control it first you would need to be able to see it , if it was me before flying I would check compass if there is a problem I would first move and check again before calibration, if it’s ok then leave it , it will be fine.
I don’t believe you picked up any interference in the air you were 77 metres above the ground, so highly unlikely.
2018-11-1
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dwin1977
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hallmark007 Posted at 11-1 10:02
Looking at your flight log , I would still say your interference began from launch, you launched from a driveway according to your log, driveways often have rebar and or electrical cables , because it cleared up very quickly would suggest that it was pretty low interference so not to serious, if your craft goes into Atti mode in order to control it first you would need to be able to see it , if it was me before flying I would check compass if there is a problem I would first move and check again before calibration, if it’s ok then leave it , it will be fine.
I don’t believe you picked up any interference in the air you were 77 metres above the ground, so highly unlikely.

Before calibration. That is something I had not considered. I sincerely appreciate this feedback. And as I had never uploaded flight data before, seeing the telemetry available on the CSV file was mind blowing! Encountering an issue and having your drone live to fly another day is a win-win. This will go far in making me a better pilot. Thank you so much for the education.
2018-11-1
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hallmark007
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dwin1977 Posted at 11-1 10:17
Before calibration. That is something I had not considered. I sincerely appreciate this feedback. And as I had never uploaded flight data before, seeing the telemetry available on the CSV file was mind blowing! Encountering an issue and having your drone live to fly another day is a win-win. This will go far in making me a better pilot. Thank you so much for the education.

Your welcome hope it helps.
2018-11-1
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JJBspark
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dwin1977 Posted at 11-1 10:17
Before calibration. That is something I had not considered. I sincerely appreciate this feedback. And as I had never uploaded flight data before, seeing the telemetry available on the CSV file was mind blowing! Encountering an issue and having your drone live to fly another day is a win-win. This will go far in making me a better pilot. Thank you so much for the education.

Hi dwin,

Had a look at your flight too.

My advice is to ask DJI to help you out.

Why, because your MA dropped height from 77 meters to 36 meters, even when you pushed your stick upwards!
Speed increased as well. about my ID 1100-1200 in the charts.
Not sure if a strong interference to your MA can cause this kind of IMU exceptions.
You had several interferences to your craft during flight, but momentarily and after that the RTH`s went ok.


If you had picked this up at your take-off spot than imo your whole flight should be a 'compass' mess flight, and RTH would not work as good as it did.
During your flight no ATTI mode was there.
cheers
JJB

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2018-11-1
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dwin1977
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JJBspark Posted at 11-1 12:58
Hi dwin,

Had a look at your flight too.

Thank you so much! I do recall a drop in altitude during the event causing me to shout out to my spotter that I was crashing. How do I report this to DJI? I had thought the forum would be the venue. Any help is greatly appreciated.
2018-11-1
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JJBspark
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dwin1977 Posted at 11-1 13:26
Thank you so much! I do recall a drop in altitude during the event causing me to shout out to my spotter that I was crashing. How do I report this to DJI? I had thought the forum would be the venue. Any help is greatly appreciated.

contact DJI >  support@dji.com

@DJI moderators ; is this the correct procedure?

cheers
JJB
2018-11-1
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