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No compass calibration?
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MySky
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JJB* Posted at 11-23 00:50
Hi,

Mayby i misunderstood, so what do you mean with "relative angle" in #4 ?
If you meant the relative angle = position on the AOI scale ; yes  than you need compass data from the mobile device as well.

Exactly
2020-11-23
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KlooGee
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bjr981s Posted at 11-21 19:24
Yes,

The issue is 2 fold.

I think we both still fundamentally disagree with what is happening during the compass calibration process.  I still agree with Geebax and Labroides' technical descriptions.

Cheers, and yes, wear a mask!
2020-11-23
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KlooGee
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Geebax Posted at 11-21 15:43
"Think about this....when calibrating DJI drone users can start on any heading the calibration, just make a 360 turn (flat+nose down).  SW measures the normal expected variation in magn fields though the magnetometer and if its done in a free of magn interference area  calibration is succesfull. Minor deviations through a full circle are averaged. Done."

Agreed. This is a vital point in the discussion, and one that many people simply do not understand. There is no point in the compass dance where you point the aircraft in a guaranteed heading, so the whole process cannot reasonably be called a 'calibration', because when calibrating any variable you would have to tell the device under calibration that the current variable corresponds to a known value. At no point in the compass dance do you do anything that indicates where either magnetic or true north is located.

"At the risk of starting another fight, and hurting even more butts, I will also suggest that local magnetic variation is a complete red-herring also."

I'm glad to see someone else with a similar thought.  I expressed basically the same thought in post #66.  Cheers!
2020-11-23
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GaryDoug
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JJB* Posted at 11-23 00:52
Hi Gary,

ofcourse, what i mean is to turn your RC to the left and right, see my video last part.

Yep, when you asked us What is causing this, I could not help but scream the answer at the pc monitor !!!!
2020-11-23
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R_Packard
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Labroides Posted at 11-22 18:12
You would be making a mistake.
The guy that made the video is just spreading misinformation.
He doesn't understand what he's talking about.

I've been reading the thread and paying attention to points made. If calibration is done, let's say once a month, you'd say its a waste of time due to your experience of 4 years without incident (calibration wise)? Appreciate your thoughts.
2020-11-23
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Geebax
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KlooGee Posted at 11-23 13:24
"At the risk of starting another fight, and hurting even more butts, I will also suggest that local magnetic variation is a complete red-herring also."

I'm glad to see someone else with a similar thought.  I expressed basically the same thought in post #66.  Cheers!

Thank you. Where I live in Australia there used to be a Royal Australian Air Force base, and on that base there was a concrete pad at the side of a taxiway. The pad was circular and had a marker showing magnetic north and true north. The idea was to line up the nose of the aircraft so it was pointing to magnetic north, then check if the aircraft's compass agreed with that alignment. If not, the compass could be unlocked and rotated in its gimbal to line up with the marker. This was called 'swinging the compass', and the purpose was to correct for any magnetic influence contained in the aircraft to 'calibrate' the compass.

This wa the only time I have every heard of the compass being actually adjusted this way. But note that it differs from the DJI approach in one important factor, the DJI approach does not require you to point the aircraft towards a 'marker' of any sort. Hence the reason I refuse to describe the DJI process as 'calibrating' the compass, unlike the procedure used by the RAAF to calibrate their compasses.
2020-11-23
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Labroides
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R_Packard Posted at 11-23 16:15
I've been reading the thread and paying attention to points made. If calibration is done, let's say once a month, you'd say its a waste of time due to your experience of 4 years without incident (calibration wise)? Appreciate your thoughts.

If calibration is done, let's say once a month, you'd say its a waste of time
I'd say it was a waste of time unless you've changed something about your drone.
Unless you modify the drone, the magnetic fields associated with the drone don't change and that's the only thing that compass calibration measures.
2020-11-23
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R_Packard
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Labroides Posted at 11-23 18:43
If calibration is done, let's say once a month, you'd say its a waste of time
I'd say it was a waste of time unless you've changed something about your drone.
Unless you modify the drone, the magnetic fields associated with the drone don't change and that's the only thing that compass calibration measures.

Thanks for the input.
2020-11-23
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GaryDoug
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...........
2020-11-23
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WebParrot
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I echo the majority of comments regarding the non-necessity of routine recalibration.  It will ask you to do it if it needs it.  After dozens of flights I received the notice to Recalibrate, and was really curious about what could have changed.  Nearly all my launches have been from my yard (rural).  I usually launch from a gravel driveway.  But, the last time I flew it had just finished raining, leaving the driveway muddy.  So I launched from the bottom stair step....poured concrete.  I'd forgotten that there were iron rebars imbedded in the concrete, likely source confusing the compass.  The drone let me know.   
2020-11-23
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JJB*
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Geebax Posted at 11-23 17:17
Thank you. Where I live in Australia there used to be a Royal Australian Air Force base, and on that base there was a concrete pad at the side of a taxiway. The pad was circular and had a marker showing magnetic north and true north. The idea was to line up the nose of the aircraft so it was pointing to magnetic north, then check if the aircraft's compass agreed with that alignment. If not, the compass could be unlocked and rotated in its gimbal to line up with the marker. This was called 'swinging the compass', and the purpose was to correct for any magnetic influence contained in the aircraft to 'calibrate' the compass.

This wa the only time I have every heard of the compass being actually adjusted this way. But note that it differs from the DJI approach in one important factor, the DJI approach does not require you to point the aircraft towards a 'marker' of any sort. Hence the reason I refuse to describe the DJI process as 'calibrating' the compass, unlike the procedure used by the RAAF to calibrate their compasses.

Great story!

Not only was the aicraft nose pointed to the N marking, but nose moved in sequence every 30 degrees.
On each point readouts on the aircraft magnetic compass system and of the "handheld" calibrated compass in front of the nose. After this 360 swing some calculations were made and the average off-set adjusted on the aicraft compass. Flying longer distances aircrew had to adjust manually a variation correction to the compass.
On post processing of the compass swing a 360 correction card was made and sticked next to a standby (mandatory) small magn compass in the craft.

Happily DJI uses a simple magnetometer as a compass, no need and impossible to do a compass swing like above, no one has a checked on true N compass swing spot in their garden

BTW My MA2 came out of the box, did many many flights without compass calibration. (and china is not next to my country)
I only had to do a compass cal   bc  the app told me so.
My MM1 needs every 31 days of after traveling some distance a compass calibration, days and last position of cal are saved somewhere, data shows up in the DAT file.



cheers
JJB


2020-11-24
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KlooGee
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Geebax Posted at 11-23 17:17
Thank you. Where I live in Australia there used to be a Royal Australian Air Force base, and on that base there was a concrete pad at the side of a taxiway. The pad was circular and had a marker showing magnetic north and true north. The idea was to line up the nose of the aircraft so it was pointing to magnetic north, then check if the aircraft's compass agreed with that alignment. If not, the compass could be unlocked and rotated in its gimbal to line up with the marker. This was called 'swinging the compass', and the purpose was to correct for any magnetic influence contained in the aircraft to 'calibrate' the compass.

This wa the only time I have every heard of the compass being actually adjusted this way. But note that it differs from the DJI approach in one important factor, the DJI approach does not require you to point the aircraft towards a 'marker' of any sort. Hence the reason I refuse to describe the DJI process as 'calibrating' the compass, unlike the procedure used by the RAAF to calibrate their compasses.

I don’t personally have any first-hand experience in “real” aviation, but it’s my understanding that a painted compass rose is a pretty regular way for pilots to be able adjust their compass for deviations. I’ve had a look at my local airports via Google Maps and don’t see them, but from what I’ve read in the past, it was very common place.  Especially at smaller airports.
2020-11-24
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bjr981s
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KlooGee Posted at 11-23 13:19
I think we both still fundamentally disagree with what is happening during the compass calibration process.  I still agree with Geebax and Labroides' technical descriptions.

Cheers, and yes, wear a mask!

Yes OK. I guess I should have started right from the beginning.

I was talking about the specific part of the process not the calibration but the results of the calibration to determine declination. The offset between True and Magnetic North.

The calibration itself is the rotation of the drone in 360 degree circles in a couple of axis.

This "Calibration" requires you to rotate the drone so it cuts through the earth's magnetic field lines.

It can then align the compass to be parallel to those lines of force. i.e. point North. Magnetic north.

If anyone here did a degree in Electronics that would know about the left and right hand FBI rule. for motors and generators. If you use your hand to point like your are holding a gun Thumb up forefinger pointed forward and the middle finger out at 90 degrees Thumb (Force) represents the direction of rotation. Forefinger (B) is the magnetic field, measured in Teslas. And middle finger (I) is the direction of current. By the variations in the current flow the magnetometer can validate (Calibrate itself) to magnetic north.

Anyhow, this has gotten to be a PINA. I surrender, I cant educate those that refuse to listen.

I'm not talking about you KlooGee.

Oh p.s. local magnetic anomalies effect the magnetic line of force.      
2020-11-24
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bjr981s
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Geebax Posted at 11-23 17:17
Thank you. Where I live in Australia there used to be a Royal Australian Air Force base, and on that base there was a concrete pad at the side of a taxiway. The pad was circular and had a marker showing magnetic north and true north. The idea was to line up the nose of the aircraft so it was pointing to magnetic north, then check if the aircraft's compass agreed with that alignment. If not, the compass could be unlocked and rotated in its gimbal to line up with the marker. This was called 'swinging the compass', and the purpose was to correct for any magnetic influence contained in the aircraft to 'calibrate' the compass.

This wa the only time I have every heard of the compass being actually adjusted this way. But note that it differs from the DJI approach in one important factor, the DJI approach does not require you to point the aircraft towards a 'marker' of any sort. Hence the reason I refuse to describe the DJI process as 'calibrating' the compass, unlike the procedure used by the RAAF to calibrate their compasses.

Thanks for posting that. In Sydney harbour there is a set of marker poles for you to tie up to once you calibrate the ships compass. By doing a number of 360m degree turns, then tie up, and it gives a position of true north so you can calibrate you Ships autopilot compass heading for that locations declination. Navigation 101.


2020-11-24
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JohnLietzke
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I agree that the drones compass rarely needs calculated after the first time.  But on the Mavic Air 2 the orientation of the drone to the controller for some reason seems to be misaligned frequently.  Some part of the compass calibration for the drone resolves this problem.

These are two entirely different issues.  The drone's compass which in my experience holds a heading accurately.  And the orientation of the drone to the controller which in my experience often gets out of alignment.  All though they are two entirely different processes and computations when either is errant it can be remedied by a Compass Calibration of the Mavic Air 2.
2020-11-24
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