Compass question

[gymnast46]

Apologies if this question has already been answered but a search didn't bring it up. Is it necessary to recalibrate the compass each time you fly? Or only if prompted? After my first flight less than a week ago, I've had several flights from around town and have calibrated the compass each time. I'm just wondering if I can skip this step.

 

[Dedal]

Normally yes, you can skip it. It will tell you if it's needed. It can't hurt to do it before every flight, but not necessary. Search threads, it's been covered already:

Mavic compass needs to be calibrated before each flight

Long time phantom owner here, the M2P is my first mavic. I have flown about 12 flights and I’ve noticed the compass gives me an error before every flight. Reguardless of where I am I get a compass error when I take the mavic out of the bag, is this normal?

mavicpilots.com

I know that the thread above is not for Mini, certainly it's not the only one, still, you can read through.

 

[gymnast46]

Thanks. Some of the posters there indicated that they rarely recalibrate. That gives me peace of mind.

 

[OldEd]

Up to now, I calibrated the compass and imu only two times. Meanwhile I made 40 flights without any problems.

 

[Dedal]

It has been said that IMU should be calibrated after FW update (at least checked together with compass if it needs calibrating), honestly, ask pilots who is doing it on regular basis, I'd be curious to see answers. You could print pre-flight check list and have it with you all the time. For example here:

MM Pre Flight Check List

Suggestions for a pre-fight check list in PDF? I have checked the internet and found various list for DJI drones, but as of yet, none for the MM. I realize that the others could be modified but wondering if anyone has created one for the MM.

mavicpilots.com

Pre-flight Checklist template

Below is a basic preflight checklist that might be useful to some, if nothing else as a way to develop a habit of best practices before you fly. It is based off of one I found online at The Drone Trainer - Free Video Training and Drone Resources I hope some of you find it useful. UAV...

mavicpilots.com

Of course, you can find many more info on this topic by searching the threads.

 

[RichR]

I recalibrate the compass (but not the IMU) if I'm taking off from a different location to the last time I did it, as the local magnetic conditions could be different there. On my other drones you have to calibrate every time you plug the battery in, so having it optional on the Mavic is a huge bonus for me.

 

[jwp721]

44 flights in and I have only been asked to calibrate one time........

 

[Xanadu]

According to the manual...

 

[Brightspark]

According to the manual...

View attachment 99987

Didn’t read the manual but another thing I’ve learnt on this forum [emoji106]

 

[Jeffdj]

Aihough the drone normally tells you if it needs a compass calibration sometimes it doesn’t, it’s important that you check that the direction indicator on the map actually corresponds to the actual direction on the ground. I recently had my first crash with any of my 4 DJI drones because the mini didn’t ask for a calibration but I failed to notice the postion indicator was 120 degrees out, initially it took off and hovered as normal but as I flew forward the mini yawed off to the right and quickly crashed into nearby rocks.

 

[sar104]

I recalibrate the compass (but not the IMU) if I'm taking off from a different location to the last time I did it, as the local magnetic conditions could be different there. On my other drones you have to calibrate every time you plug the battery in, so having it optional on the Mavic is a huge bonus for me.

The calibration isn't to compensate for external local magnetic conditions, so that doesn't buy you anything.

 

[RichR]

Perhaps 'conditions' wasn't quite the right word. Is it not calibrating for the local magnetic declination and deviation? That's what I understand from the manuals for my Hubsan and Syma drones that require calibration on every power connection.

Admittedly if I'm only 2 miles away I probably wouldn't bother, but if I was 100 miles away the local magnetic deviation could be different? I'm keen to understand how things work, so maybe I've misunderstood.

 

[Guitarzan]

44 flights in and I have only been asked to calibrate one time........

About the same with me!

 

[sar104]

Perhaps 'conditions' wasn't quite the right word. Is it not calibrating for the local magnetic declination and deviation? That's what I understand from the manuals for my Hubsan and Syma drones that require calibration on every power connection.

Admittedly if I'm only 2 miles away I probably wouldn't bother, but if I was 100 miles away the local magnetic deviation could be different? I'm keen to understand how things work, so maybe I've misunderstood.

It cannot account for declination (the difference between magnetic north and true north) or deviation (the difference between magnetic north and the local magnetic field due to nearby magnetic objects) because it has no way to know the direction of true north except by reference to the magnetic field. It computes declination based on location from a global model of the earth's magnetic field that is in the firmware. Deviation cannot be determined by any method, and is the cause of many compass/yaw errors and uncontrolled flight.

The compass calibration is simply to measure and subtract the magnetic field of the aircraft itself, leaving just the external field. It measures it during the calibration process by separating the components of the magnetic field that don't change as you rotate the aircraft (the aircraft's magnetic field since that rotates with the aircraft) from the components that do change - the external magnetic field - that is assumed to be the earth's magnetic field.

 

[gymnast46]

It cannot account for declination (the difference between magnetic north and true north) or deviation (the difference between magnetic north and the local magnetic field due to nearby magnetic objects) because it has no way to know the direction of true north except by reference to the magnetic field. It computes declination based on location from a global model of the earth's magnetic field that is in the firmware. Deviation cannot be determined by any method, and is the cause of many compass/yaw errors and uncontrolled flight.

The compass calibration is simply to measure and subtract the magnetic field of the aircraft itself, leaving just the external field. It measures it during the calibration process by separating the components of the magnetic field that don't change as you rotate the aircraft (the aircraft's magnetic field since that rotates with the aircraft) from the components that do change - the external magnetic field - that is assumed to be the earth's magnetic field.

Good to know. Thanks to everyone who responded.

 

[RichR]

Yes, thanks. That's a much better explanation than the Hubsan and Syma manuals give for the reason for calibration!

 

[Meta4]

Yes, thanks. That's a much better explanation than the Hubsan and Syma manuals give for the reason for calibration!

That's interesting to see that DJI isn't alone in giving confusing and misleading information about the compass.
The very poor compass information in manuals has caused no end of confusion and myths about the drone's compass.
Much of what many flyers believe about it is completely wrong.

 

[ff22]

The calibration isn't to compensate for external local magnetic conditions, so that doesn't buy you anything.

So why does the Zoom drone (have not had the mini long enough to know) ask to be recalibrated after moving 30 or more miles away from its last position? If it is only for dealing with the drone's magnetic influences. Each time I've taken the drone for longer field trips it asks to be recalibrated? Driving to the Cascades - recalibrate. Come home, recalibrate. Drive to Seaside, Or, recal and same coming back home. One or two similar instances. It is that DJI thinks I may have had it in the wrong/bad location in my car?

Thanks

 

[sar104]

So why does the Zoom drone (have not had the mini long enough to know) ask to be recalibrated after moving 30 or more miles away from its last position? If it is only for dealing with the drone's magnetic influences. Each time I've taken the drone for longer field trips it asks to be recalibrated? Driving to the Cascades - recalibrate. Come home, recalibrate. Drive to Seaside, Or, recal and same coming back home. One or two similar instances. It is that DJI thinks I may have had it in the wrong/bad location in my car?

Thanks

Both Mavic 2 models request recalibration based on distance (50 km) or time (30 days). I cannot answer definitively as to the reasoning behind that, but I can note that calibration cannot compensate for external influences - that's basic physics. DJI has been very inconsistent in their approach to compass calibration - the M2 was the first model to implement that requirement and previous models had varying advice on when to calibrate.

 

[Phergie]

I couldn't figure out why my MM asked for compass calibration on nearly every flight, and then I figured out that my in-ground pool is just loaded with re-bar that extends at least 50' out from the pool. Once I got the MM outside of this envelope, the compass problem was solved!