Compass Calibration Confessions

[Bob N]

Okay. So I'll admit I calibrated the compass every time I went out to fly even if in the same location. Even the FAA now gets in on it as they say to recalibrate the compass before every flight with their Part 107 sample checklist.

Even if the small unmanned aircraft system (sUAS) manufacturer has a written pre-flight inspection procedure, it is recommended that the Remote Pilot in Command (Remote PIC) ensure that the following inspection items are incorporated into the preflight inspection procedure required by part 107 to help the Remote PIC determine that the sUAS is in a condition for safe operation.

And one of those steps is to calibrate the compass...

Calibrate UAS compass prior to any flight

However DJI in their operator's manual (version 1.8 (Phantom 3 Advanced) now says:

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

So now I only calibrate as directed which is also included in the documentation.

 

[jephoto]

I had done this when first started flying. Then, after a near disaster in downtown Chicago when my friends P3 started acting wacky & almost crashed before we could land it, found out how you can calibrate it WRONG if in a bad location, therefore causing enormous compass errors and making things worse than they should be.
Now I just wait for the Home point to set itself, or if I can't get a lock, move the bird over 10-20' & try again. Usually that is all that needed.


Sent from my iPhone using PhantomPilots mobile app

 

[Whiskey_Throttle]

I had done this when first started flying. Then, after a near disaster in downtown Chicago when my friends P3 started acting wacky & almost crashed before we could land it, found out how you can calibrate it WRONG if in a bad location, therefore causing enormous compass errors and making things worse than they should be.
Now I just wait for the Home point to set itself, or if I can't get a lock, move the bird over 10-20' & try again. Usually that is all that needed.


Sent from my iPhone using PhantomPilots mobile app

Interesting. I have been calibrating the compass only if I have moved farther away from the last calibration point than about 5 miles. Now I see the latest manual says "Only calibrate the compass when the DJI GO app or the status indicator prompt you to do so". I'll be calibrating a lot less now.

 

[jephoto]

Yup. Totally unnecessary. And potentially creating a problem when there shouldn't be one.

 

[jephoto]

In March I flew from chicago to Los Angeles. Next morning went to our job, fired up the drones, got a home point lock in 30 sec. Flew away. No problem. What's that- 1,700 miles away? More?
I did do an IMU calibration the night I got in. But that's all.

 

[Whiskey_Throttle]

In March I flew from chicago to Los Angeles. Next morning went to our job, fired up the drones, got a home point lock in 30 sec. Flew away. No problem. What's that- 1,700 miles away? More?
I did do an IMU calibration the night I got in. But that's all.

Did you do an IMU cal because of the distance traveled or because the phantom might have been jarred around a bit during the trip ?

 

[Bob N]

Interesting. I have been calibrating the compass only if I have moved farther away from the last calibration point than about 5 miles. Now I see the latest manual says "Only calibrate the compass when the DJI GO app or the status indicator prompt you to do so". I'll be calibrating a lot less now.

Be sure and turn the page. It also says to recalibrate for 4 reasons. One of which is a change in locations.

 

[Bob N]

In March I flew from chicago to Los Angeles. Next morning went to our job, fired up the drones, got a home point lock in 30 sec. Flew away. No problem. What's that- 1,700 miles away? More?
I did do an IMU calibration the night I got in. But that's all.

Home Lock is based on the GPS or at least that's what it looks like the manual is saying:

If the Home Point was successfully recorded and the compass is functioning normally, Failsafe RTH will be automatically activated ifthe remote controller signal is lost for more than three seconds.

 

[Pharm]

I've had mine since March and have never done an IMU calibration. Several weeks ago I did a compass calibration before flying. Later, back at home, I flew a 2 mile one way Litchi mission without calibration from my last flight (180 miles away) and it was spot on.

 

[Meta4]

Interesting. I have been calibrating the compass only if I have moved farther away from the last calibration point than about 5 miles. Now I see the latest manual says "Only calibrate the compass when the DJI GO app or the status indicator prompt you to do so". I'll be calibrating a lot less now.

That's poor wording on DJI's part.
If you put your Phantom on steel or reinforced concrete, you will get warning of a compass error.
Recalibrating in that situation is the worst thing to do.
Moving away from the magnetic distortion is all that's needed.

Did you do an IMU cal because of the distance traveled or because the phantom might have been jarred around a bit during the trip ?

Distance traveled has no effect on your IMU but it is recommended that you recalibrate the IMU after any big bumps etc.

 

[jephoto]

Did you do an IMU cal because of the distance traveled or because the phantom might have been jarred around a bit during the trip ?

Distance. Just as precaution. I carried it in backpack so jarring wasn't an issue.
Acording to the Go, it wasn't needed.

 

[Vertigo]

Did you do an IMU cal because of the distance traveled or because the phantom might have been jarred around a bit during the trip ?

Distance is relative, but long distance you should recalibrate for several reasons;

-magnetic declination. Its possible the Phantom does this automatically based on GPS location, Im unsure. On a pixhawk flight controller this is an option you can configure, on the phantom Id be guessing. Either way, this map will give you a sense of scale, its not an issue when driving 100 miles, it is an issue if you travel to another continent:

-Another potential reason is local magnetic anomalies. Here is another map to give you a sense of scale:

NAMAD - A New Magnetic Anomaly Map of North America

We're talking variations of less than 1000nT here, which isnt huge (earths magnetic field is on the order of 50000 nT), but could be enough to give problems. But in this case, the Phantom ought to warn you that you need a recalibration.

 

[phantomi]

Compass recalibration is almost unnecesary and doing it at every flight is calling for problems.

 

[Whiskey_Throttle]

Distance is relative, but long distance you should recalibrate for several reasons;

-magnetic declination. Its possible the Phantom does this automatically based on GPS location, Im unsure. On a pixhawk flight controller this is an option you can configure, on the phantom Id be guessing. Either way, this map will give you a sense of scale, its not an issue when driving 100 miles, it is an issue if you travel to another continent:

-Another potential reason is local magnetic anomalies. Here is another map to give you a sense of scale:

NAMAD - A New Magnetic Anomaly Map of North America

We're talking variations of less than 1000nT here, which isnt huge (earths magnetic field is on the order of 50000 nT), but could be enough to give problems. But in this case, the Phantom ought to warn you that you need a recalibration.

Thanks - interesting. Manual says to calibrate only when the Go app or status indicator prompts you to do so. Then includes 4 other caveates - including flying in a new location as Bob N points out. The only time I've had the app tell me to re-calibrate was when the drone was near magnetic distortion - drone just needed to be moved, not calibrated.

 

[Bill A]

I drive from omaha ne to wichita ks. 300 miles. No recalibration. Home point recorded ok. And no issues flying. Although I was extremely nervous.

 

[Falcon900]

I drive from omaha ne to wichita ks. 300 miles. No recalibration. Home point recorded ok. And no issues flying. Although I was extremely nervous.

If you look at the declination map above posted by Vertigo, you will see Omaha and Wichita are nearly on the same declination line.

 

[cactus683]

I would have never known the wordings have changed in the manual,great post here.Is this for all the advanced models regardless of when purchased?

 

[WetDog]

Thanks - interesting. Manual says to calibrate only when the Go app or status indicator prompts you to do so. Then includes 4 other caveates - including flying in a new location as Bob N points out. The only time I've had the app tell me to re-calibrate was when the drone was near magnetic distortion - drone just needed to be moved, not calibrated.

But I noticed the typically unhelpful little blurb that pops up when you start the DJI GO app still says to calibrate 'if you move to a different location'.

Be nice if somebody got all the DJI employees responsible for this sort of thing in a room and beat them soundly until they managed to get a consistent message across.

 

[cactus683]

Compass recalibration is almost unnecesary and doing it at every flight is calling for problems.

I also heard this,i dont fly enough to know but i just wanna know whats the right thing to do.

 

[flyboyQuad3]

Okay. So I'll admit I calibrated the compass every time I went out to fly even if in the same location. Even the FAA now gets in on it as they say to recalibrate the compass before every flight with their Part 107 sample checklist.


And one of those steps is to calibrate the compass...

However DJI in their operator's manual (version 1.8 (Phantom 3 Advanced) now says:


So now I only calibrate as directed which is also included in the documentation.

Good to know.