Hi,
I was talking about compass calibration with some people and I was to reference the page where the user manual said that you should calibrate only when prompted. I found however that in version 2.0 (2017-12-19) of the User Manual now it says:

-------------------------------
It is recommended to calibrate the compass in any of the following situations when flying outdoors:

1. Flying at a location farther than 10 km away from the last flight location.
2. The aircraft hasn’t been flown for more than one month.
3. A compass interference warning appears in the DJI GO 4 app, and the warning persists after changing location.

Restart the aircraft when calibration is complete
-------------------------------

While version 1.8 (the previous one) says:

-------------------------------
Only calibrate the compass when the DJI GO 4 app or the status indicator prompt you to do so.
-------------------------------


I'm wondering why this recommendations changed so much. In fact, I do believe that after flying for over a year with my mavic pro following the previous recommendations this change should have been announced properly! In fact, my guess is that in the past you could claim that you just followed the user manual recommendations. Now if your drone flies away due to a problem with the compass, DJI can point out that you didn't perform a calibration while changing the takeoff point to a place more than 10km away. Furthermore, people MUST be notified about the requirement of RESTARTING the aircraft after performing the calibration. Everybody has been calibrating the compass and flying straight away, which can also trigger crashes being blamed on user error. There's also no video on DJI Support youtube channel explaining how to properlly calibrate the compass: New pilots checking videos on how to calibrate will be watching old videos and therefore learning an (according to the user manual) wrong method to calibrate.

This kind of changes must be warned somehow, maybe with a message when opening the APP, which is something that has been used to warn users before.

I would be glad to have the answer too!
There is different instructions about the compass for Phantoms and Mavics ))
What of them more correct?

From late January ....

https://forum.dji.com/thread-132421-1-1.html

Regardless of what DJI or any other vendor says you must recalibrate your compass if you move you flight location > 10 KLM. The compass uses the magnetic pole not true north.

The Variation from Magnetic north to true north depends on you location and time and date. Hence the timeframe advised to redo the calibration.

More information can be found on this site.

http://www.geomag.nrcan.gc.ca/calc/mdcal-en.php

Also if you move your launch location to where there is magnetic interference. e.g. to a city centre or near large metal structure you need to calibrate there as wel,l even if under 10klm from your normal location.

It is also recommended but not mandatory to recalibrate after a FW update.

Cheers

bjr981s Posted at 2018-3-14 22:40
Regardless of what DJI or any other vendor says you must recalibrate your compass if you move you flight location > 10 KLM. The compass uses the magnetic pole not true north.

The Variation from Magnetic north to true north depends on you location and time and date. Hence the timeframe advised to redo the calibration.

Your statement is absolutely correct.

I  am always checking the compass sensors within my pre-flight check and if the value goes constantly over 50 or spikes over 75 I do a good compass calibration. (far away from metallic objects, etc)

Those recommendations have already been mentioned in the manual of the Phantom 1 and is just common sense.

bjr981s Posted at 2018-3-14 22:40
Regardless of what DJI or any other vendor says you must recalibrate your compass if you move you flight location > 10 KLM. The compass uses the magnetic pole not true north.

The Variation from Magnetic north to true north depends on you location and time and date. Hence the timeframe advised to redo the calibration.

That is total rubbish, there will be no difference in declination when moving 10 km . Can you tell me why it’s 10km with Mavic Pro and 50 km with Mavic Air, never unless app tells you to with spark same with P4Pro inspire matrice .

Calibration gives the compass the information it needs to determine which magnetic influences are part of the Mavic  and what is the earth's normal magnetic field.
The compass doesn't lose calibration and doesn't ever need re-calibration unless you add or remove equipment to/from the Mavic.

The problem here is dji don’t know what they are doing and many users don’t know when to calibrate compass so they keep moving the goal posts, when we see more crashes from bad calibration the situation will change again.

I agree with Hallmark on this. I usually fly around my area but once a month drive 300km away for my monthly getaway and never calibrated compass there, never even get a warning to calibrate and bird fly's perfect.

I find there is a drift in compass accuracy after a few days sitting idle in my home environment. I think this is due to the amount of 'magnetic' fields in my house - multiple ferrous objects and power lines throughout the property. Because of this I tend to recalibrate when out in the field before each day's flying. Also have to remember to recalibrate the Crystalsky (base station) compass too.

hallmark007 Posted at 2018-3-15 17:08
That is total rubbish, there will be no difference in declination when moving 10 km . Can you tell me why it’s 10km with Mavic Pro and 50 km with Mavic Air, never unless app tells you to with spark same with P4Pro inspire matrice .

Calibration gives the compass the information it needs to determine which magnetic influences are part of the Mavic  and what is the earth's normal magnetic field.

You statement is partly correct, and the statement of @bjr981s "magnetic true" is also correct.
I agree that it is not necessary the distance affecting the calibration, but it can.
The magnetic earth field is not linear and not stable over the time, so depending where are you living or flying the effect can differ strongly.
I moved already about 1000km with my Mavic and no compass calibration was needed but on the other hand over the time of 1,5 years I had to re-calibrate 3-4 times.
I noticed also that during 2 switch to ATTI occurrences the compass calibration was slightly off, but not enough to trigger the calibration notice, it was still in the "Good" status. As one of these locations was my common flying field, where I calibrated the Mavic some weeks before , I decided to test. The result was that I could  trigger the switch to ATTI and that a calibration was needed.

Please note that also the compasses of real airplanes are periodically re-calibrated and that known magnetic anomalies are displayed on aviation maps.

Depending where you are the changes of earth magnetic field are more ore less affecting a compass, where the magnetic declination is one factor besides solar winds and other local factors.

If interested:
https://en.wikipedia.org/wiki/Earth%27s_magnetic_field
https://www.swpc.noaa.gov/products/planetary-k-index

Lamplighter55 Posted at 2018-3-16 03:00
I find there is a drift in compass accuracy after a few days sitting idle in my home environment. I think this is due to the amount of 'magnetic' fields in my house - multiple ferrous objects and power lines throughout the property. Because of this I tend to recalibrate when out in the field before each day's flying. Also have to remember to recalibrate the Crystalsky (base station) compass too.

Unless your drone is turned on nothing will effect your compass.

frankengels Posted at 2018-3-16 12:34
You statement is partly correct, and the statement of @bjr981s "magnetic true" is also correct.
I agree that it is not necessary the distance affecting the calibration, but it can.
The magnetic earth field is not linear and not stable over the time, so depending where are you living or flying the effect can differ strongly.

I agree we should all be aware of declination and the changes and effects it can have on compass, but every time you fly is bad advice, while it’s not overly difficult to calibrate it’s very difficult to make a good compass better by calibrating, but very easy to make it worse.
Calibration in areas of high metallic or magnetic interference is not a good idea unless you intend flying in a steel tube.
There are a few good practices to checking compass these should be applied before calibration, also you have app warnings before you fly telling you to move or calibrate, you should always move first.

I think DJI are just covering 'their' potential liabilities. After all if a calibration is done correctly then it can't do any harm. But as Hallmark007 says the potential for a bad calibration increases when done more often. I believe that the calibration is only taking into account any immediate disturbances in magnetic field generated by the structure and components of the aircraft itself. A traditional magnetic compass does not need calibration to know which way magnetic north is, but if you stick it on handle bars of a bicycle then some adjustment would have to be made. Perhaps using the Bezel as a guide :-)

Edit:- Another good example is 'Kelvins Balls' (No tittering in the back row there !) to calibrate a ships magnetic compass which is surrounded by steel.

Hi there, for the reason of the calibration, I had replied you on this post 47#. Please check.

DJI Thor Posted at 2018-4-2 03:36
Hi there, for the reason of the calibration, I had replied you on this post. Please check. https://forum.dji.com/forum.php?mod=redirect&goto=findpost&ptid=136804&pid=1285734&fromuid=332382

Sorry DJI Thor but your post you are referring to is gone.

It's simple, DJI entrusted that part of the manual to a newbie to rewrite, as they are prone to do, and they entered the technically correct  answer.   A BS answer, but technically correct.   Sorry guys, not buying into it.  I would only calibrate if given a warning, and that would happen only after I moved location twice.   The only time I have received a compass calibration warning.................over rebar, over a buried tank, buried piping, hood of my car, etc.    Have not had a issue from Texas to the Atlantic and Illinois to the Gulf Coast.   Mavic or Phantom.

DJI Thor Posted at 2018-4-2 03:36
Hi there, for the reason of the calibration, I had replied you on this post. Please check. https://forum.dji.com/forum.php?mod=redirect&goto=findpost&ptid=136804&pid=1285734&fromuid=332382

Bad link there, Thor. Would you double-check please?

Kevjones1959 Posted at 2018-4-2 03:51
Sorry DJI Thor but your post you are referring to is gone.

Sorry for this, I had updated the link, please check if it works.

SkySailorMan Posted at 2018-4-2 06:30
Bad link there, Thor. Would you double-check please?

Thank you for bringing the attention, I had refreshed the link, please let me know if it works.

hallmark007 Posted at 2018-3-15 17:08
That is total rubbish, there will be no difference in declination when moving 10 km . Can you tell me why it’s 10km with Mavic Pro and 50 km with Mavic Air, never unless app tells you to with spark same with P4Pro inspire matrice .

Calibration gives the compass the information it needs to determine which magnetic influences are part of the Mavic  and what is the earth's normal magnetic field.

Umm a bit harsh. Let me give you some further clarification.

The compass in the Spark and Mavic Air is a single compass. The Mavic Pro has 2 compasses.

The compass calibrate warning is generic and just says "hey my compass has gone wacko." Either calibrate or move away from a huge anomily.

When the calibration is done it takes into account any local magnetic anomalies. There will always be some.

Moving over 10 Klm is far enough away that a new calibration is required. Not just because there may be anomalies in the new location but also because you have moved away from any anomalies that were previously registered.

Also while you may not have any issues in your locale, the further you move towards the poles the greater the drift due to Latitude.

So either DJI publishes a calibration routine for every city / locale on the planet for all latitudes, including a database that includes every magnetic anomaly on the planet. Or they provide a general  set of instructions to suit everyone to provide a safe and reasonable non intrusive procedure.

Which alternative would you pick?

Cheers
     

This has been a long running debate, as I live in Florida the magnetic declination is minimal from the East to West Coast +/- 1, my P4P, MP and MA never ask me to calibrate the compass from coast to coast, however my P3P always asks me to calibrate compass wherever I go.

Gonna stay away from the Bermuda Triangle for awhile

bjr981s Posted at 2018-4-4 10:11
Umm a bit harsh. Let me give you some further clarification.

The compass in the Spark and Mavic Air is a single compass. The Mavic Pro has 2 compasses.

You see the problem is to much confusion, actually Mavic Air has two compass and instructions from manual say calibrate Mavic Pro every 10k moved Mavic Air every 50k and Spark and phantom 4pro never unless your app tells you, this confusion is mainly down to dji not knowing what should be done.

You can calibrate how ever many times you like so long as you do it properly, but this is not necessary unless you have a bad compass or app requires you to.

Taking on the the anomalies of the area your launching in would be the worse piece of advice you could give anyone particularly if you are calibrating in an area where high forms of magnetic interference is around, if you were to calibrate in this area as soon as you fly out of the magnetic area your compass will be totally out of whack, and this could be as soon as flying to height of 20ft.

Where there is a big difference in magnetic declination yes you should calibrate, where there is as Quadkid pointed out below small amount of declination there is no need to calibrate.

One thing we must all remember is if you have a good compass by calibrating you won’t make it any better, but you could make it worse.

Your right I was a bit harsh so please accept my apology, there was no call for it.

bjr981s Posted at 2018-4-4 10:11
Umm a bit harsh. Let me give you some further clarification.

The compass in the Spark and Mavic Air is a single compass. The Mavic Pro has 2 compasses.

Just one other thing you should be aware of Mavic Air has built in look up table that stores global information so there should never be any need to calibrate unless your app tells you to and even then be sceptical and move your drone to a safe location and try again.

hallmark007 Posted at 2018-4-4 12:09
Just one other thing you should be aware of Mavic Air has built in look up table that stores global information so there should never be any need to calibrate unless your app tells you to and even then be sceptical and move your drone to a safe location and try again.

That is very interesting information, thank you!

i was last year on Cape Verde (from Slovakia) and i forgot to do compass calibration and flew for 2 weeks and everything was good. With mavic pro i calibrated once or twice. With mavic air only once after unboxing. Zero crashes and errors

There may be a big difference between magnetic declination from place to place. What matters most is the soils or rocks containing of iron as well as how close you are north/south pole. In the link here you can find the magnetic declination on every place on the globe:  http://www.magnetic-declination.com/

Regards Leif