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Tip to Help Avoid Compass Interference
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hallmark007
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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 , you will know this by looking at your bar graph, it is recommended 4/5 bars are lit up.

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 about 1minute and is worthwhile doing before every flight,
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A CW
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Great advice, as always   
2018-5-14
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Far_North
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Couldn't agree more, especially #1.
I have never calibrated my compass and never been prompted to.  Was good right out of the box.  I fly a MPP.
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小仙女的星巴克
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great practice before you fly away
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Simmo1
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All good, but DJI already tell you to do this important step, its just that people dont conduct the step in its entirety, nor does DJI explain properly...

There is more to "The home point has been recorded.....please check it on the map."

1) By recording a homepoint, the FC says that 'GPS Health' is adequate, a much more desirable requirement than simply, the number of sats aquired.
2) Check it on the map! For sure, have a look and see if you still are in the same country!!
3) Takes about 4 seconds longer than checking your location is correct.... is the Red Icon, pointing the same way as your physical AC?

Thats it! Do what the app said... Go Fly!
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asaw
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> 1/ Never calibrate Compass unless prompted to.


This contradicts the Mavic Air's manual:


Screen Shot 2018-05-14 at 16.06.30.png
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Bulldog
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Great post.

I didn't know about #4. I knew about locking the home point, but didn't know the arrow should be pointing in the same direction as the drone. That seems like an important way to check accuracy. Thank you.

As for #1, even though asaw above posted the recommendations from DJI, I don't agree. I agree with Hallmark here. Extra calibration seems counter productive, IMO.
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asaw
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Bulldog Posted at 2018-5-14 05:16
Great post.

I didn't know about #4. I knew about locking the home point, but didn't know the arrow should be pointing in the same direction as the drone. That seems like an important way to check accuracy. Thank you.

It may be not necessary, but I don't see how it can do any harm if done correctly.
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Dirk52
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asaw Posted at 2018-5-14 05:11
> 1/ Never calibrate Compass unless prompted to.

You are completely right. And you should always act like the manufacturer and developer prescribes it. Don't rely on wrong tips here. In a case of flyaway or crash Dji will ask (or check via logs) whether you followed the steps in the manual. If you don't...byebye warranty or free replacement
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JJBspark
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asaw Posted at 2018-5-14 05:19
It may be not necessary, but I don't see how it can do any harm if done correctly.

i fully agree with you ; compass calibration doesn`t harm in any way your compass drone. So it can be done each and every flight in you want!

BUT in BIG CAPITALS : if you calibrate your compass in a area with magnetic interference you will calibrate that into your compass. When you start to fly and your drone is out that envirroment you will get a compass fail etc etc....probably end up in ATTI mode and bad luck on a windy day its a hell of a job to fly back to homepoint manually (some experts flyers do that easily ofcourse...)

So be absolutely sure that when you calibrate that the area you are in is "clean"!!

cheers
JJB

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hallmark007
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asaw Posted at 2018-5-14 05:11
> 1/ Never calibrate Compass unless prompted to.

You really should take the time to read all your manuals
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QuadKid
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I have only calibrated the compass once upon activation for any drone(s) after P4/Go4, and they have never prompted me to recalibrate since. Now my P3P requires it pretty much everytime I fly it and sometimes just when switching batteries.
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hallmark007
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JJBspark Posted at 2018-5-14 05:36
i fully agree with you ; compass calibration doesn`t harm in any way your compass drone. So it can be done each and every flight in you want!

BUT in BIG CAPITALS : if you calibrate your compass in a area with magnetic interference you will calibrate that into your compass. When you start to fly and your drone is out that envirroment you will get a compass fail etc etc....probably end up in ATTI mode and bad luck on a windy day its a hell of a job to fly back to homepoint manually (some experts flyers do that easily ofcourse...)

Your correct Compass calibration preformed correctly won’t do any harm, and if users choose to do this, it is their aircraft.

However there are two things we should know, 1/ you cannot make a good compass better through calibration. 2/ as you have already pointed out it is very easy  to make it a whole lot worse.
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asaw
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hallmark007 Posted at 2018-5-14 06:21
You really should take the time to read all your manuals[view_image]

What my manuals? There's nothing like that in the MA manual. OK, found it in the safety guidelines. If it is not a contradiction then this is a mistake because when I first started my MA the DJI GO 4 didn't ask me to calibrate the compass although it hadn't flown for over a month and came from far away.
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B1houdini
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Thanks for the tips.
I will add it to my files that I keep and rely on when I have a problem.
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Suren
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Thank You Hallmark, I swear that when i got my spark and saw this the first time, I have used it always
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HedgeTrimmer
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JJBspark Posted at 2018-5-14 05:36
i fully agree with you ; compass calibration doesn`t harm in any way your compass drone. So it can be done each and every flight in you want!

BUT in BIG CAPITALS : if you calibrate your compass in a area with magnetic interference you will calibrate that into your compass. When you start to fly and your drone is out that envirroment you will get a compass fail etc etc....probably end up in ATTI mode and bad luck on a windy day its a hell of a job to fly back to homepoint manually (some experts flyers do that easily ofcourse...)

BUT in BIG CAPITALS : if you calibrate your compass in a area with  magnetic interference you will calibrate that into your compass.

For most part, that is the one time you need to worry about magnetic interference from not only obvious sources, but possible hidden sources.
I plan to post a TIP (link) I believe will help with possibility of hidden sources.  

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HedgeTrimmer
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Far_North Posted at 2018-5-14 03:23
Couldn't agree more, especially #1.
I have never calibrated my compass and never been prompted to.  Was good right out of the box.  I fly a MPP.

Lucky you.  For a long time, my MPP would insist on Compass Calibration anytime system (MPP / RC / GO-4) app was restarted or powered up.  Didn't matter if Compass was calibrated in different areas with nothing but field grass within 200-feet.

Problem went away either do to switching to CS-Ub or a firmware update.
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hallmark007
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asaw Posted at 2018-5-14 08:37
What my manuals? There's nothing like that in the MA manual. OK, found it in the safety guidelines. If it is not a contradiction then this is a mistake because when I first started my MA the DJI GO 4 didn't ask me to calibrate the compass although it hadn't flown for over a month and came from far away.


It’s disclaimer and safety manual, so it has great importance to all users, every user of dji aircraft have to sign this when activating their aircraft so it is prudent to read it.

Although manuals have changed and compass instructions have changed, for instance in P4Pro inspire2 the manual clearly tells you not to calibrate compass until prompted, with Mavic Pro they have changed to calibrate every 10km which would mean that because of battery range of Mavic Pro you could be under the impression that during your flight you might have to land and calibrate, with spark calibrate only when app tells you to, with MavAir we know it has a look up table so it knows where it is in the world so if it needs calibration it will always prompt you, I can vouch for this.

I also have Mavic Pro and have only ever calibrated once as per instructions when I purchased and likewise for P4Pro, I also fly matrice which is a little different but very similar to inspire2 and P4Pro .

Much of the myth surrounding calibration is down to much earlier craft and also incorrect information in older manuals, what dji’s take on the whole thing is somewhat strange my belief is that many crashes caused by bad calibration seen them change from advice to only calibrate when prompted and now we see but only aircraft used by mainly new users a seed change without explanation back to calibrate at intervals. This advice is only for their small aircraft.

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, or aircraft compass has been damaged.
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HedgeTrimmer
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Bulldog Posted at 2018-5-14 05:16
Great post.

I didn't know about #4. I knew about locking the home point, but didn't know the arrow should be pointing in the same direction as the drone. That seems like an important way to check accuracy. Thank you.

It is also a way to check for hidden / unknown Magnetic Interference.  Problem is that compass is pretty jumpy and granular in nature.
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HedgeTrimmer
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hallmark007 Posted at 2018-5-14 09:15
It’s disclaimer and safety manual, so it has great importance to all users, every user of dji aircraft have to sign this when activating their aircraft so it is prudent to read it.

Although manuals have changed and compass instructions have changed, for instance in P4Pro inspire2 the manual clearly tells you not to calibrate compass until prompted, with Mavic Pro they have changed to calibrate every 10km which would mean that because of battery range of Mavic Pro you could be under the impression that during your flight you might have to land and calibrate, with spark calibrate only when app tells you to, with MavAir we know it has a look up table so it knows where it is in the world so if it needs calibration it will always prompt you, I can vouch for this.

The compass doesn't lose calibration and doesn't ever need re-calibration unless you add or remove equipment to/from the Mavic, or aircraft compass has been damaged.

What about when flying in a completely different area from where compass was calibrated?
For example: Flying in Texas, when compass was calibrated in Minnesota.  Or flying in South America, when compass was calibrated in France.
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hallmark007
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HedgeTrimmer Posted at 2018-5-14 09:21
The compass doesn't lose calibration and doesn't ever need re-calibration unless you add or remove equipment to/from the Mavic, or aircraft compass has been damaged.

What about when flying in a completely different area from where compass was calibrated?

Magnetic declination should be reported in your app, for MavAir users they have a look up table so the compass knows where in the world it is, it will most likely prompt you when this happens if it requires calibration.

I have traveled distances of over 2000 miles with both Mavic Pro and MavAir many times and only once have I been asked to calibrate with MavAir, never with Mavic Pro and have never had any issues but always in pre check , I check compass .
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JJBspark
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hallmark007 Posted at 2018-5-14 07:59
Your correct Compass calibration preformed correctly won’t do any harm, and if users choose to do this, it is their aircraft.

However there are two things we should know, 1/ you cannot make a good compass better through calibration. 2/ as you have already pointed out it is very easy  to make it a whole lot worse.

You have read my post the way i wanted it to be read ; /2 find a nice large open area without any metal / concrete / etc and do your calibration. No need to calibrate after that for 'ages'....

Last time i had my MA in a top-case on my motorcycle, had a 50 km ride and had to calibrate my MA.
GoApp told me this. After that calibration its still OK each flight.

cheers JJB
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hallmark007
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JJBspark Posted at 2018-5-14 10:08
You have read my post the way i wanted it to be read ; /2 find a nice large open area without any metal / concrete / etc and do your calibration. No need to calibrate after that for 'ages'....

Last time i had my MA in a top-case on my motorcycle, had a 50 km ride and had to calibrate my MA.

With the look up table on MavAir it seems that it is very aware of movement of drone and will always prompt to calibrate if it needs you to.
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HedgeTrimmer
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hallmark007 Posted at 2018-5-14 09:27
Magnetic declination should be reported in your app, for MavAir users they have a look up table so the compass knows where in the world it is, it will most likely prompt you when this happens if it requires calibration.

I have traveled distances of over 2000 miles with both Mavic Pro and MavAir many times and only once have I been asked to calibrate with MavAir, never with Mavic Pro and have never had any issues but always in pre check , I check compass .

Thank you.
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HedgeTrimmer
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Bulldog Posted at 2018-5-14 05:16
Great post.

I didn't know about #4. I knew about locking the home point, but didn't know the arrow should be pointing in the same direction as the drone. That seems like an important way to check accuracy. Thank you.

In regards to #4.  

After setting your drone down in takeoff spot, you really need to take a couple of paces back with smartdevice running GO-4 app.

Otherwise compass in smartdevice is likely to be effected by any magnetic interference that may be effecting your drone's compass.

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Oracle Miata
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I know its been discussed countless times, but my Mavic Air is really the only DJI drone that asks me to calibrate.  Almost every time I settle in to a flying session...  only for the first battery.
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Oracle Miata
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Also, I am curious about the look up table?  What  is that?
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SparksBird
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Very good info here.  Thanks for posting this.
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asaw
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hallmark007 Posted at 2018-5-14 09:15
It’s disclaimer and safety manual, so it has great importance to all users, every user of dji aircraft have to sign this when activating their aircraft so it is prudent to read it.

Although manuals have changed and compass instructions have changed, for instance in P4Pro inspire2 the manual clearly tells you not to calibrate compass until prompted, with Mavic Pro they have changed to calibrate every 10km which would mean that because of battery range of Mavic Pro you could be under the impression that during your flight you might have to land and calibrate, with spark calibrate only when app tells you to, with MavAir we know it has a look up table so it knows where it is in the world so if it needs calibration it will always prompt you, I can vouch for this.

Calibration at least provides information on how the sensor responds to a constant magnetic induction along each of its three axes (in order to determine biases along each axis) and determines magnetic induction readings of undisturbed Earth magnetic field at the current location. These biases may change over time just like with any measurement devices which may be affected by temperature, humidity or the way they were stored/transported/handled. And these magnetometers being microelectromechanical systems do react to such factors.

My MA, when it came from the factory, didn't ask me to calibrate the compass. I looked into the compass section in GO 4 anyway and noticed that its error readings varied between green and yellow (I don't remember the exact numbers). It got much better after I finally calibrated it. But this only has an effect when flying outdoors. First time I flew indoors from a reinforced concrete floor and for the sake of safety it was more important to configure the drone not to return home on RC signal loss rather than fiddle with the compass. So it is better to understand how these autopilots and various sensors they rely on work than blindly follow contradicting instructions.
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hallmark007
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asaw Posted at 2018-5-14 12:20
Calibration at least provides information on how the sensor responds to a constant magnetic induction along each of its three axes (in order to determine biases along each axis) and determines magnetic induction readings of undisturbed Earth magnetic field at the current location. These biases may change over time just like with any measurement devices which may be affected by temperature, humidity or the way they were stored/transported/handled. And these magnetometers being microelectromechanical systems do react to such factors.

My MA, when it came from the factory, didn't ask me to calibrate the compass. I looked into the compass section in GO 4 anyway and noticed that its error readings varied between green and yellow (I don't remember the exact numbers). It got much better after I finally calibrated it. But this only has an effect when flying outdoors. First time I flew indoors from a reinforced concrete floor and for the sake of safety it was more important to configure the drone not to return home on RC signal loss rather than fiddle with the compass. So it is better to understand how these autopilots and various sensors they rely on work than blindly follow contradicting instructions.

Your first point if there is a problem with your compass you will get a warning through your app.

Your second point by all means calibrate your compass , I would always say that it is prudent to check your compass.
Regarding re setting parameters of RTH indoors I’m not aware of any for MavAir, except if aircraft is within 5 metres of take off it will just land but I don’t know how you would change this, normally flying indoors you would be without gps so RTH in these cases would not occur . I know in Mavic you have option to hover with loss of signal, but not with RTH , maybe you can share how to reset RTH for indoors.
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KlooGee
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Good post (and timing), I've got a video in the works on this same topic talking about the compass and includes these same points!  Hopefully I find the time to finalize it in the next couple of days.
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hallmark007
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KlooGee Posted at 2018-5-14 12:53
Good post (and timing), I've got a video in the works on this same topic talking about the compass and includes these same points!  Hopefully I find the time to finalize it in the next couple of days.

Good I look forward to watching, as I do to all your videos.
Good luck.
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asaw
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hallmark007 Posted at 2018-5-14 12:47
Your first point if there is a problem with your compass you will get a warning through your app.

Your second point by all means calibrate your compass , I would always say that it is prudent to check your compass.

We have three options: RTH, hover and land. GPS positioning may start working indoors near a window for example. It is undesirable but, alas we can't choose the mode we want to fly in manually.
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Griffith
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Bulldog Posted at 2018-5-14 05:16
Great post.

I didn't know about #4. I knew about locking the home point, but didn't know the arrow should be pointing in the same direction as the drone. That seems like an important way to check accuracy. Thank you.

The arrow is important.  If it is not pointing in the direction of aircraft orientation, it a fairly sure indication of a compass mis-calibration.
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hallmark007
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asaw Posted at 2018-5-14 13:03
We have three options: RTH, hover and land. GPS positioning may start working indoors near a window for example. It is undesirable but, alas we can't choose the mode we want to fly in manually.

With loss of signal hover or land these are choices , unless they came with new FW I don’t have them I do have hover with MP and P4Pro not as RTH option only as loss of signal wasn’t aware of hover on MavAir.
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hallmark007
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Oracle Miata Posted at 2018-5-14 10:52
I know its been discussed countless times, but my Mavic Air is really the only DJI drone that asks me to calibrate.  Almost every time I settle in to a flying session...  only for the first battery.

I’m not sure but I have a feeling the sensor for compass is set way to sensitive, there are many here having similar problems, not sure what the answer is , hopefully it gets fixed for those with problems.
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Montfrooij
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Good info.
Thanks!
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hallmark007
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Your very welcome.
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Montfrooij
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