When to calibrate compass (and what for)?

[kilhan]

Hi Guys,

I’m a bit confused with the problem of compass calibration. In the DJI P4P manual it is clearly stated: “ ONLY calibrate the compass when the DJI GO 4 app or the status indicator prompt you to do so.”

In many other tutorials (even on the my UAVO course) I’ve read or heard advices to calibrate compass every time when you change a starting place or even before EACH flight. As my P4P app or status has never asked me to calibrate the compass, following the DJI manual, I have never done it (though I know how to do it), even before the first flight.

So I ask myself a question: to calibrate or not to calibrate, and if calibrate, when and why?

RTH works perfectly, Home Lock also works perfectly.
I’m only not sure if the red arrow in the circle with artificial horizon works as expected. Should it show the drone’s nose orientation relative to me (i.e. RC)? If so, it doesn’t do it. Can it have any connection with the compass calibration?

And more theoretically: Which functions or indicators are influenced by good or bad compass calibration?

TIA for any hints and explanations

Chris

 

[davemex]

My understanding... and someone please step in if I'm wrong... Compass calibration is probably the most important when you're moving from one latitude to another. My theory here stems from the deviation between magnetic north and true north, I know in aviation you have to adjust your heading based on where you are (if I remember correctly - it's been a few years) as the magnetic deviation changes as you get further north or south.

I usually calibrate after a long trip but when staying within my own town I never calibrate unless it tells me to.

The compass is probably being used in conjunction with the GPS to determine auto flight paths. So if it's off, it could head in the wrong direction thinking it's going somewhere else.

 

[tcope]

You should understand that both of those instructions can be the same.

The P4 has 2 IMU's so it's very likely that you now won't have issues with incorrect calibrations. I don't know for sure that this means two compasses but it's still far less likely that the compass calibration will be off and when it is, it's more likely that the software will report this. As I mentioned above, there is usually only an issue when moving a great distance, especially east and west.

So you can feel free to only calibrate when prompted by software or when you move a great distance. I recommend only recalibrating when moving several hundred miles east and west. I also recommend against calibration each time you fly or only move a few miles. But these are my recommendations.

 

[ElGuapo]

davemex, I respect your opinion. However, I've been in many trips abroad, Costa Rica most recently, did not calibrate and did not have a problem. One day , while in CR, I flew out to the sea to take pics and vids of a fishing boat a mile and a half off the coast. Only problem I had was that it had to be a good 92 degrees on that day, when I brought her back to swap to a fresh battery the motors were extremely hot to the touch.

To the OP, you are going to find members in this forum highly divided on this topic, to calibrate or not calibrate.

Personally, this is just me, I only calibrate after a firmware update or when prompted by the DJI GO App.

 

[davemex]

You should understand that both of those instructions can be the same.

The P4 has 2 IMU's so it's very likely that you now won't have issues with incorrect calibrations. I don't know for sure that this means two compasses but it's still far less likely that the compass calibration will be off and when it is, it's more likely that the software will report this. As I mentioned above, there is usually only an issue when moving a great distance, especially east and west.

So you can feel free to only calibrate when prompted by software or when you move a great distance. I recommend only recalibrating when moving several hundred miles east and west. I also recommend against calibration each time you fly or only move a few miles. But these are my recommendations.

I didn't think about the dual IMU thing. I just switched over from a P3P and I was very very strict about always calibrating at new places but I'm guessing it was much more important with that model than it will be with the P4P.

 

[Richard R]

Divination actually occurs with longitude. But there is rarely a need to recalibrate the compas unless some other outside issue such as a firmware update or crash recovery causes the system to issue a warning. Remember that phantoms aren't really navigating from point a to point b, just out from and back to the home point. Don't really care if the magnetic heading back to home is 145 degrees or 148. It went out of a radial and will just head back on the reciprocal. So as long as there are no hick ups in the local magnetic field, the compass should be ok. Now if you have traveled several hundred miles east or west and have a mission where actual aircraft heading is critical such as the direction that you want the camera to point, you may want to consider a recalibrate. Short of that, I wouldn't until or unless the software gave me a warning and even then, my first thought would be to check that the takeoff location wasn't causing the problem due to local metals.

 

[Meta4]

I’m a bit confused with the problem of compass calibration. In the DJI P4P manual it is clearly stated: “ ONLY calibrate the compass when the DJI GO 4 app or the status indicator prompt you to do so.”

In many other tutorials (even on the my UAVO course) I’ve read or heard advices to calibrate compass every time when you change a starting place or even before EACH flight. As my P4P app or status has never asked me to calibrate the compass, following the DJI manual, I have never done it (though I know how to do it), even before the first flight.

Due to poor wording in the manuals for earlier Phantoms.a myth developed that caused people to believe they should recalibrate the compass frequently.
This was a complete myth and experience showed that a properly calibrated compass doesn't lose its calibration and you can safely fly for months or even longer without recalibrating.

The myth persisted because people liked the warm fuzzy feeling they got from doing something they believed was beneficial.
But unnecessarily recalibrating a perfectly good compass is the cause of many reported "flyaways".

To get a better understanding of what compass calibration is about, this thread has a lot of details:
Compass Calibration, A Complete Primer

I’m only not sure if the red arrow in the circle with artificial horizon works as expected. Should it show the drone’s nose orientation relative to me (i.e. RC)? If so, it doesn’t do it. Can it have any connection with the compass calibration?

Not the compass in your Phantom .... but the compass in your phone or tablet.
Google to find out how to calibrate the compass in your tablet.

And more theoretically: Which functions or indicators are influenced by good or bad compass calibration?

The most common indication of a bad compass calibration is your Phantom slowly spiraling rather than holding position (toilet bowl effect).

Your P4 pro doesn't need you to calibrate the compass - even after a firmware update.
That's why DJI finally updated the words in the manual.
Their wording still isn't perfect though.
If you ever get a warning of magnetic field interference, the appropriate corrective action is to move away from the magnetic field, not to recalibrate your compass.

 

[kilhan]

Thank you Meta4 for an extensive explanation and all others for the discussion.
I suspected that the word “ONLY” in the manual can mean that an unnecessary calibration of the compass can have even negative consequences and I see now that I was right not to calibrate and not following some “gurus” advices.

It was my first question in this forum and I am very positively surprised how quickly I got such a valuable help and not only from other members but also form the staff. Thanks once again to Meta4

Chris

 

[ibuyufo]

I never calibrate the compass and I've never had any issue.