Compass Error During Flight

I was in a descending procedure from a higher altitude and came at say 40 m over the church’s metal roof. I deviated to the yard and all went well down to landing. But uploading the flight data to AirdataUAV I noticed the AC has recorded a compass error warning exactly when the bird had to deal with the large church’s metal roof.

Ideea is the compass doesn’t like at all any large metal surfaces, so you would better avoid flying over such. There are known cases (see on YT) with drones that crashed following a flight over / around a ship, the huge metal surfaces compromising permanently the compass.

I had to fly these days around a huge Liebherr 1600 crane, involved on a highway construction. Uploading the flight to AirdataUAV, I found that the max compass turn rate per 0.1 seconds became 11.50 value which is huge compared to values as 3.50-6.00 I usually get. This is still inside the acceptable span of 15-16 degrees per 0.1 seconds, but it’s obvious the bird didn’t liked at all the vicinity of the crane.
If you were 40 metres above a steel roof your drone's compass would not even detect it.
As mentioned in post #5 you would have to get much closer - try it some time.
The explanation is more likely related to something else.
Airdata is not really useful for investigating incidents as it shows a brief summary.
Use the Phantomhelp log viewer to see the actual data.
Idea is the compass doesn’t like at all any large metal surfaces, so you would better avoid flying over such. There are known cases (see on YT) with drones that crashed following a flight over / around a ship, the huge metal surfaces compromising permanently the compass.
This doesn't sound right at all.
The compass is flying all day long within the magnetic field of the earth without problems.
If it's flown close enough into the magnetic field of a large enough iron/steel object, its idea of where magnetic north is will deviate.
Fly out of the magnetic field and everything is back to normal.

There are known cases (see on YT) with drones that crashed following a flight over / around a ship, the huge metal surfaces compromising permanently the compass.
I had to fly these days around a huge Liebherr 1600 crane, involved on a highway construction. Uploading the flight to AirdataUAV, I found that the max compass turn rate per 0.1 seconds became 11.50 value which is huge compared to values as 3.50-6.00 I usually get. This is still inside the acceptable span of 15-16 degrees per 0.1 seconds, but it’s obvious the bird didn’t liked at all the vicinity of the crane.
How close were you to the crane?
You would have to be extremely close to see any compass effect.
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Every week I fly over and around ships without any issues at all.
There's a lot more steel in these than in a crane.
If it was the way you are describing it, I wouldn't be able to do this.
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Stop making guesses based on Airdata.
Find out the real caused of what Airdata was hinting at.
Go back and try what I suggested in post #5 to see how this really works.
 
@Meta4 let me highlight you something: I remember during descending while having nearby (10 m) church’s metal roof, the bird has started to slowly spiral which is a typical symptom when the compass is affected. Noticing this, I’ve stopped its spiral by forcing a small rotation in the opposite direction. Surprisingly, in the visual flight log from DJI Go the bird doesn’t seem to rotate its nose during this spiral descending portion.
Is it meaning DJI Go is not recording accurate compass data when the device becomes affected by magnetic perturbances ?
 
@Meta4 let me highlight you something: I remember during descending while having nearby (10 m) church’s metal roof, the bird has started to slowly spiral which is a typical symptom when the compass is affected. Noticing this, I’ve stopped its spiral by forcing a small rotation in the opposite direction.
Surprisingly, in the visual flight log from DJI Go the bird doesn’t seem to rotate its nose during this spiral descending portion.
Is it meaning DJI Go is not recording accurate compass data when the device becomes affected by magnetic perturbances ?
The app records what the sensors are detecting.
If the compass is getting a false reading due to additional magnetic fields nearby, the app will record the false data.

To see the actual flight data go to DJI Flight Log Viewer
Follow the instructions there to upload your flight record from your phone or tablet.
It will give you a detailed report.
If you need help analysing or understanding what it shows, come back and post a link to the report it provides.
 
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I have an additional question to compass errors.

I often fly from boats, or startling point close to reinforced concrete (lots of steel in it), and the drone warns about a compass error. I know it is temporary. Do you agree it is safe to have a quick start (going away quickly) as the error disappears right after the drone is far enough?

Thank you in advance for your opinions...
 
As meta has said, if you are prepared and don’t panic you won’t have problems. I often launch from my deck, it’s a suspended concrete slab with a ridiculous amount of steel reinforcing- I often have compass errors when launching (have to hand launch from above head height) and when returning but all is good once clear.
I just read this before writing my last post. Thanks for the supportive message I needed! Cheers!
 
I have an additional question to compass errors.

I often fly from boats, or startling point close to reinforced concrete (lots of steel in it), and the drone warns about a compass error. I know it is temporary. Do you agree it is safe to have a quick start (going away quickly) as the error disappears right after the drone is far enough?

Thank you in advance for your opinions...
Absolutely not! A compromised Yaw resulting from a geomagnetic distortion will not immediately correct itself when the AC rises above the distortion. The Yaw is determined mostly using IMU data with magnetometer data being used but at a lower gain. It can take anywhere from 15 to 60 secs before the magnetometer data fully corrects the Yaw value. This has been the cause of many a fly away.

This delay can also work in your favor though. If the AC is powered on away from the distortion, e.g. you turn it on while holding it, then the Yaw will be correct. Then placing it on the ground where there is a distortion will cause the compass error message you see. But, if it's launched immediately there will not have been enough time for the Yaw to have been compromised (at least not enough to cause a problem).

Your best bet is to check before launch that the red triangle heading indicator in the map display is consistent with the AC's actual heading.

Typically, the distortion due to rebar only extends for .5 meter or so. Hand launching will be above this.
 
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Hi All. Earlier I was approaching a metal silo of sorts to get a close up picture. At about 20 feet out I started receiving a compass error warning. I do not know exactly what the message said as I flew away from the object ASAP. So, my question is, what would happen if I ignored warning and flew closer. I snapped this picture, and after descending a little bit more received the warning.

View attachment 101009

Having just dealt with this on another post , let me say this : Compass errors and Magnetic interference are two errors you cannot mess with as they both have the potential to crash your drone .

Atti mode is the back up for when things go wrong and some people claim that you can continue to fly but not if you have also experienced a YAW error .
If that happens than your drone is not going to be able to be controlled and its going to fly on it own in any direction it wants .

We have never been able to fly in Atti mode after a magnetic or Compass error , only if we deliberately take off in Atti mode can we sustain it, but if we get a warning that something is wrong , we start praying to the atti gods that we can just land.

Watch what happens when we take off on a concrete pier with metal rails , the drone stops moving as soon as we get the magnetic Interference error.
the drone does not want to move forward or back I was hoping it might go into Atti Mode and I would catch it. All Red Lights .

So that Pier has proven to be a magnetic Bomb for the drone , even a hand release has failed on this pier..
Unfortunately the rain took out the Audio on the Sony Camera. Sorry about that.

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