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Why did my Spark have compass and IMU error over water?
1245 16 2017-8-9
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pashas_dad
Second Officer
Flight distance : 982723 ft
United States
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Was flying my Spark over the LI Sound this evening, the aircraft was  about 340 ft high and 750 ft over the water from my location on the  beach. I suddenly due to some unknown reason got a compass error  followed by an IMU error and it switched into ATTI mode.  I began to  panic and barely got the aircraft back to shore safely after trying to  fly in Sport mode to get back quickly.
Can't understand why I would get a compass error way out over water with  no magnetic material anywhere close to the aircraft. THis is why I  suspect some latent defect. I have attached some possible usefull photos  below.

May I have someone from DJI examine my flight logs to possibly see if  this is a defective aircraft? It has already been replaced once. How can  I open a case for this?



AirData log showing errors

AirData log showing errors

Showing location of error

Showing location of error

Maap of open area

Maap of open area
2017-8-9
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$gambino$
First Officer
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Seems like alot of us getting those errors
2017-8-9
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Rawsome
First Officer
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Canada
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in particular over water, with no obstructions around what so ever.
2017-8-9
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hallmark007
Captain
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Ireland
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You can pick up bad compass on the ground, this doesn't always show until further into your flight. You really should put up your full flight log, or post logs from phantomhelp which are a lot better than airdata.
2017-8-10
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Drone Man Bob
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Had these warnings recently too, although not over water
2017-8-10
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hallmark007
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If you take a look at this video it might give you more of an understanding of how easy it is to pick up compass problems from the ground.


2017-8-10
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Anuvis
First Officer
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Greece
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Since 4.1.5 dji go app i have these errors too
2017-8-10
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DJI Thor
Administrator
Flight distance : 13602 ft
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Sometimes it will affect the function of the drone when it flies above the water. But it should not affect that high as you mentioned it flew 340 ft high. Please try another place to fly. Remember to calibrate the compass and IMU first for this flight. Please keep us updated if the prompt persists, thank you.
2017-8-10
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PascalG
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In the case of that video I wonder if the ship radars (probably had two units running) and whatever transmitters were running (satcom, VHF, AIS etc) didn't contribute to the interference.

It would be nice if the app would display interference levels (compass and imu) on the screen as soon as they become elevated.
2017-8-10
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hallmark007
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PascalG Posted at 2017-8-10 04:11
In the case of that video I wonder if the ship radars (probably had two units running) and whatever transmitters were running (satcom, VHF, AIS etc) didn't contribute to the interference.

It would be nice if the app would display interference levels (compass and imu) on the screen as soon as they become elevated.

Most of the time you will get notice to move or calibrate or just compass error, some choose to ignore these problems and take off warning goes away because they have removed aircraft from interference, but compass may already be out of whack similar to what you seen in the video, where compass triangle is facing wrong way around.
Once you get warnings, you should always move from the area, or if you are in the air try to land safely somewhere.
2017-8-10
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pashas_dad
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hallmark007 Posted at 2017-8-10 01:11
You can pick up bad compass on the ground, this doesn't always show until further into your flight. You really should put up your full flight log, or post logs from phantomhelp which are a lot better than airdata.

Here is a link the flight log:
Flight data with errors over water
2017-8-10
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pashas_dad
Second Officer
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BTW this was the second flight of that same day with a second battery. There were no such issues on the first flight.
In fact these errors did not show up until after 11 minutes into flight #2. I would think if there was a compass cal problem it would have shown up much earlier. The compass was not calibrated again prior to flights on this day. THere was no need to recalibrate was not far at all from my calibrated launch point.

In fact I had deliberately checked that the red directional arrow in the lower left box in DJI GO4 and it actually was pointing in the direction the aircraft was pointed to prior to  launch!  I always do this now after a prior issue with a fly away and crash on my original Spark that was replaced by DJI for this one.
This reduces the possibility of compass errors at calibration!

2017-8-10
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hallmark007
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pashas_dad Posted at 2017-8-10 05:07
Here is a link the flight log:
Flight data with errors over water

Unreadable file sorry.
2017-8-10
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pashas_dad
Second Officer
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I'm sorry about that, just downloaded it again, here is a link again. I checked it and it read fine with the uploader.  I also have .dat file and Black Box data links below.

text file:
https://drive.google.com/file/d/ ... 2M/view?usp=sharing

Here is .dat file:
https://drive.google.com/file/d/ ... Ek/view?usp=sharing

Here is Black box Data:
https://drive.google.com/drive/f ... elA5QUk?usp=sharing


2017-8-10
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pashas_dad
Second Officer
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Here is a direct link to the GO4 flight record:
http://www.phantomhelp.com/LogViewer/V8W6S14SQJPWQQOJCGCA/
Perhaps someone from DJI could review this data and provide some insight!  Please!
2017-8-10
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hallmark007
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pashas_dad Posted at 2017-8-10 05:46
Here is a direct link to the GO4 flight record:
http://www.phantomhelp.com/LogViewer/V8W6S14SQJPWQQOJCGCA/
Perhaps someone from DJI could review this data and provide some insight!  Please!

You picked up compass interference somewhere you haven't said were you took off from or why you calibrated compass when you did .

Although we might think everything is ok because we receive no warning about bad compass or ground interference it isn't always the case we always should be aware of the area we are launching from, I am not saying this was the case in your situation, but I have seen many what seem like normal launches only to experience bad compass at sometime during the flight.

Your Aircraft went into mag yaw meaning compass is pulling one way gps another direction thus causing problems for IMU basically making it impossible to control heading of Aircraft, so Spark has to drop what is causing data conflict to IMU and since Spark can't fly without compass it drops gps and goes auto into Atti mode, you managed to control it well enough not to lose your spark,  your compass seemed to correct itself and gps was resumed.
From your log this looks like it happened when you turned to sport mode but I very much doubt that, at least I would have no explanation for that and I've never seen this before.

While it's a bit scary when it happens it shows the benefit of flying VLOS , and this makes it easier to control as best we can in Atti mode.

I think it would be wise to sync your flight contact a moderator here and ask them to have a look at your flight, they may also have a look at your dat file, dji have not released a program to decipher spark dat file to my knowledge yet, so they will check it out to see if there are any anomalies.

2017-8-10
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pashas_dad
Second Officer
Flight distance : 982723 ft
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Thank you for your assessment  hallmark007. I will contact moderator as you recommended.
However, this brings up a larger issue perhaps.  the issue of how often to calibrate the compass. If this really was a compass cal issue then it would benefit to recalibrate every time to be safe.
As was posted on this forum as not to calibrate every time, it may be unwise to NOT recalibrate every time if this event is an example.
Guess we get and give mixed messages.  This just brings out the need for DJI to come out with some statement about this problem and tell us what we should do. Users can get very confused!
2017-8-11
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