Mavic compass needs to be calibrated before each flight

[sar104]

I fully understand how they work and use them for non drone in daily life.

We have 2 simple facts here - the DJI manual states calibrate if moving over 30 miles or unused for 30 days and (ii) the drone appears to be knowing its moved a significant distance (probably via gps) and is prompting a calibration. You can deny it all you want but thats whats happening. See also the calibration after 30 days thread with someone getting that from the .dat file.

It looks like they've changed how it works and the checks it does to fit in with the new manual revisions.

(or are you also claiming DJI themselves and the engineers are unaware how their own compass works despite building it?)

The 30 day trigger appears to be real, since it gets recorded in the event log:

34.367 : 1922 [L-COMPASS][mag_cali_pt] date_from_last 30|
34.522 : 1931 [L-FMU/LED]action changed. compass out of range:need_cali(1)

The firmware certainly could trigger a request based on current location relative to last calibration location, but it does not appear to be doing that in the sense that (a) it doesn't consistently make that request after changing location and (b) there is no location check apparent in the event log.

As for the DJI statements on the issue it's not that the engineers don't know how these things work. The DJI manuals and statements themselves have been contradictory on this since the P2, and so we know that whoever writes the manuals doesn't always understand the subject.

I asked a few posts back if you would be willing to explain the nature and reasoning behind the calibrations that you mentioned as being required for other compasses you use. I'm still interested to hear that because I think it would advance the current discussion.

 

[Chips]

Occasionally, I get a message asking me to recalibrate the compass or move the aircraft to another spot. Sometimes I move it and the message goes away but it also goes away if I don't do anything sometimes. Generally, I don't have a compass problem and I followed the suggestion of someone to reset the Home Point again after takeoff from a slightly higher altitude. It's supposed to improve accuracy for when you return to land.

 

[Tzonny]

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?

I have had my mavic for a year now and flown over 250 miles,its flown in london devon and tenerife,i have never calibrated my mavic and the only time i had a compass error was when i tried to take off from a metal bin,i moved it a few feet and it was fine,its very strange you get error msg all the time and doesnt seem right,hope you find a solution.

 

[Rockin’ Jimmy ’]

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?

Are you wearing a belt with a metal buckle? I've removed my belt once or twice and found that the magnetic interference went away. Also turn the aircraft on where you intend to take off. When I move it to a new location from where I turned it on I get the calibration required notice.

 

[Vasek]

Mine doesnt ask every time but just when i move to a new location even if not very far. Usually not twice in the same day.

Yep the same here M2Pro few km distance causes it even if there is nothing that could issue magnetic field. Even same place after return from 150 km distance

 

[DanMan32]

Occasionally, I get a message asking me to recalibrate the compass or move the aircraft to another spot. Sometimes I move it and the message goes away but it also goes away if I don't do anything sometimes. Generally, I don't have a compass problem and I followed the suggestion of someone to reset the Home Point again after takeoff from a slightly higher altitude. It's supposed to improve accuracy for when you return to land.

Now that you mention it, I have seen my M2Z very briefly show compass issue as it sets up. Went away on GPS lock.

 

[STKNRUD]

Be careful where you turn it on. For example, I never turn mine on in or near my car, near a metallic table, or other metallic object.

Never had that problem or warning and I requently launch from the metal cover over my pick-up bed. But I do get it an interference error if I TO from concrete with rebar.

 

[STKNRUD]

It's not in the firmware, because mine has never asked to be calibrated - not after arriving from China and not after moving around within the US.

It would probably help the discussion here if, rather than just asserting that compasses need to be recalibrated after moving, you could explain why and how they are recalibrated. That might shed some light on where that idea comes from.

Your explanation was both correct and clear BUT.... there will still be those refuting it and ignoring it. Standby to copy and paste again in the next thread about a abused and beaten horse.

 

[Dronescuba]

My M2P asks a lot more than M1. If i move it a distance then it asks.
The manual says you should if more than 30 miles.

I believe that magnetic North is important to the drone to help it know which way to fly especially during RTH. Which way a compass points is called magnetic north and this is not in the same place as the geographic North Pole (top of the world). There are two compasses fitted to the M2P to add redundancy and aid accuracy. The place where Magnetic North is, and where the M2P compasses and all compasses at the same location point moves around during the year as the earth orbits around the sun during a year. The result is that average position of the Magnetic North Pole can move in a loop about 120 miles during the year and also loops about 50 miles per day! This together with where you are on the earths surface effects which direction a compass points. In Texas the compass points quite accurately to the geographic North, but Florida this direction is different by up to 10 degrees West. Conversely in California it can be up to 10 degrees East. This part of the variation is due to the earth molten outer iron core which is not evenly distributed and because it is molten tends to move about as the earth rotates and generally over time. So those variations I mentioned above go up and down slightly each year, but generally they stay around the same number. So whilst I agree there could be no need to calibrate when flying in the same place each day (as long as you are not near a car, metal pipes in the ground or other metric objects within a few feet away), if you travel hundreds of miles the compass will appreciate a re calibration to help it navigate in a new location. As a matter of practice during pre flight checks I almost always re calibrate the compasses. That's my thoughts on the subject.

 

[sar104]

Your explanation was both correct and clear BUT.... there will still be those refuting it and ignoring it. Standby to copy and paste again in the next thread about a abused and beaten horse.

Agreed. What is not clear is the reason for the 30 day recalibration, or whether DJI has added any kind of location check. As I said elsewhere, this is probably a topic that will, and should, keep coming up. A very durable horse.

 

[STKNRUD]

Agreed. What is not clear is the reason for the 30 day recalibration, or whether DJI has added any kind of location check. As I said elsewhere, this is probably a topic that will, and should, keep coming up. A very durable horse.

I remember the old days where after “swinging the aircraft” at the the compass rose you still had to manually input the mag variation based on your location and correct the DG’s drift. I am a pilot from the Stone Age.

 

[sar104]

I believe that magnetic North is important to the drone to help it know which way to fly especially during RTH. Which way a compass points is called magnetic north and this is not in the same place as the geographic North Pole (top of the world). There are two compasses fitted to the M2P to add redundancy and aid accuracy. The place where Magnetic North is, and where the M2P compasses and all compasses at the same location point moves around during the year as the earth orbits around the sun during a year. The result is that average position of the Magnetic North Pole can move in a loop about 120 miles during the year and also loops about 50 miles per day! This together with where you are on the earths surface effects which direction a compass points. In Texas the compass points quite accurately to the geographic North, but Florida this direction is different by up to 10 degrees West. Conversely in California it can be up to 10 degrees East. This part of the variation is due to the earth molten outer iron core which is not evenly distributed and because it is molten tends to move about as the earth rotates and generally over time. So those variations I mentioned above go up and down slightly each year, but generally they stay around the same number. So whilst I agree there could be no need to calibrate when flying in the same place each day (as long as you are not near a car, metal pipes in the ground or other metric objects within a few feet away), if you travel hundreds of miles the compass will appreciate a re calibration to help it navigate in a new location. As a matter of practice during pre flight checks I almost always re calibrate the compasses. That's my thoughts on the subject.

A couple of small corrections:

1. Unlike the Mavic Pro, the M2P has only one compass.
2. Calibration isn't how the aircraft gets its information on the direction of true north relative to magnetic north.

And now you have everyone worried about magnetic north moving during the day. A disaster waiting to happen.

 

[STKNRUD]

So if all of this is confusing and worrisome, just fly in ATTI mode.

 

[natbike]

I thought I would help counter the idea that all M2Ps act this way. My M2P has not ever requested compass calibration (except a time I tried to take off next to a sub station, I just moved further away) and been used in London and Marseille (France) along with many places in between. About 200 flights so far.

I'm interested in this thread because my Mavic air does constantly ask for calibration, seemingly when moved long (30km) distances. Could it be a manufacturing defect that causes this? Why some and not others? Do we all set the AC down and then turn it on?

I'm especially curious since SAR104 pointed out that DJI might intend this to be done every 30 days. Why is mine not exhibiting that behaviour?

The information in this thread is excellent, I just hope we find some answers.

 

[sar104]

I thought I would help counter the idea that all M2Ps act this way. My M2P has not ever requested compass calibration (except a time I tried to take off next to a sub station, I just moved further away) and been used in London and Marseille (France) along with many places in between. About 200 flights so far.

I'm interested in this thread because my Mavic air does constantly ask for calibration, seemingly when moved long (30km) distances. Could it be a manufacturing defect that causes this? Why some and not others? Do we all set the AC down and then turn it on?

I'm especially curious since SAR104 pointed out that DJI might intend this to be done every 30 days. Why is mine not exhibiting that behaviour?

The information in this thread is excellent, I just hope we find some answers.

Is yours over 30 days old?

 

[DanMan32]

I thought mine was 30 days old, but my first flight according to Go log was 8/31.
30 days has September... I guess we'll see next week.
Manual excerpt presented says 30 days of not being used however.

 

[Meta4]

Is yours over 30 days old?

Interestingly, the wording from the manual doesn't suggest calibration every 30 days.
It says:
It is recommended that the compass is calibrated (when) the aircraft has not been flown for more than 30 days.
That would suggest that if you flew every week or two, it would not require recalibration.
The reason (if there is one) for this is quite a mystery.
As is the reason for the recommendation for recalibration if moving >50km.
As has been proved for every other DJI drone, this is completely unnecessary but the mention of it in manuals has perpetuated myths about what calibration does.
Is there really something different about the mavic 2's compass or is this just DJI continuing their tradition of poor and inaccurate documentation?

 

[pooderbill]

...Do you ever get "MAG INTERFERE" across the Remote Controller?

Big surprise: Almost all modern laptops have a massively large magnetic field at the left and right end of the case. These thin laptops don't use a mechanical switch and instead use hidden magnets. This is strong enough to grab nails and paper clips, destroy credit card stripes and affect the RC controller. No phone or drone needs to be connected -- the controller is sensitive to magnetic fields. Any large pieces of concrete (steps, walls, bridges) have long pieces of rebar buried inside. There are several magnetometer apps for IOS and Android that can sniff out magnetic areas.

 

[Meta4]

...Do you ever get "MAG INTERFERE" across the Remote Controller?

Big surprise: Almost all modern laptops have a massively large magnetic field at the left and right end of the case. These thin laptops don't use a mechanical switch and instead use hidden magnets. This is strong enough to grab nails and paper clips, destroy credit card stripes and affect the RC controller. No phone or drone needs to be connected -- the controller is sensitive to magnetic fields. Any large pieces of concrete (steps, walls, bridges) have long pieces of rebar buried inside. There are several magnetometer apps for IOS and Android that can sniff out magnetic areas.

The radio signas received and sent by your controller can be affected by wifi and other forms of radio or electromagnetic interference but they aren't particularly affected by magnetic fields.
The compass sensor in your drone is what's affected by magnetic interference.
The compass does exactly what those apps you mention do.

 

[sar104]

Interestingly, the wording from the manual doesn't suggest calibration every 30 days.
It says:
It is recommended that the compass is calibrated (when) the aircraft has not been flown for more than 30 days.
That would suggest that if you flew every week or two, it would not require recalibration.
The reason (if there is one) for this is quite a mystery.
As is the reason for the recommendation for recalibration if moving >50km.
As has been proved for every other DJI drone, this is completely unnecessary but the mention of it in manuals has perpetuated myths about what calibration does.
Is there really something different about the mavic 2's compass or is this just DJI continuing their tradition of poor and inaccurate documentation?

The manual advises that but the firmware check appears to be independent of whether it was flown, based on personal experience. And the event log entry simply refers to when the compass was last calibrated, not when it was last flown.