Compass calibration, toilet-bowl effect

[Rob Suggs]

Every time I launch my inspire it goes into a spiraling, toilet bowl spin. I usually just take control, rock it around a bit, spin it, and then it's hovers stationary. I have two questions: does the compass continue to calibrate as it flys (like smart phones do with continued motion) and am I calibrating wrong before launch?

I have noticed that after calibrating the compass, the orientation of the aircraft is always about 20 degrees to the right based on what the satellite map shows. That is, if I point the aircraft directly at a landmark, the map show the aircraft pointing 20 degrees to the right of the landmark. After flying a bit, the directions of the map and aircraft align.

To calibrate, I am using the hold-at-arms-length-and-spin-while-I-look-like-a-dork-dance. The instructions seem to suggest a much more difficult hand-over-hand-and-hope-you-don't-drop-it-motion. And, yes, I set the controller and all other electronics at least 10 feet away before doing this.

Thoughts?

 

[lrwskyfilms]

I am using the hold-at-arms-length-and-spin-while-I-look-like-a-dork-dance.

LOL, yes the "compass dance". Can I assume oyu are you doing both parts, 360 degrees horizontal and 360 vertical?

 

[Rob Suggs]

Yep, I am doing both parts.

I have noticed the deviation between my true direction and the map with my Phantom also (same direction, same amount). I had assumed this might be a failure of the app to compensate for the difference between true north and magnetic north--just a guess. However, If my phantom toilet-bowls, it is usually within a 5' circle. The Inspire starts out at about 5' and grows with each revolution to over 50'. I have never let it keep going to see just how large the circle will grow.

 

[QuadGrandad]

I am having same effect when putting quad in flight position. If I leave it in landing mode, I get no toilet bowl behavior.
The quad settles down after a few minutes, and hovers fine.
Question is, why does it only happen with gear up? I've flown with no GPS, and in opti mode with legs down, and had no problems. The quad is an early one, dated 12/27/14.

 

[QuadGrandad]

I am having same effect when putting quad in flight position. If I leave it in landing mode, I get no toilet bowl behavior.
The quad settles down after a few minutes, and hovers fine.
Question is, why does it only happen with gear up? I've flown with no GPS, and in opti mode with legs down, and had no problems. The quad is an early one, dated 12/27/14.

I should clarify.. I get toilet bowl effect with landing gear up. It does settle down after a few minutes, but it has to be "flown" and made to behave. At no time do I lose GPS , nor do I get a compass error.

 

[RolandRSA]

I have not experienced the toilet bowl effect and in Cape Town our declination is -24 degrees. It was a huge problem on my P2 before the firmware update late last year. I have not experienced it on my Inspire yet but I have only done 3 flights.

I do have the issue where the nose of the aircraft is always off slightly. I have recalibrate do the compass two or three times before flight to try and correct it but it does not really make a difference. My iPhone does the same thing in Apple maps or Google maps, could it be a declination issue? Is it something I need to be concerned about?
I generally do the same procedure as Turbo when powering up if that makes any difference.

 

[RolandRSA]

Cool, when i was doing it i was on a Galaxy Tab. Gonna do a flight with my iPad today and test it out.
Thanks.

 

[Rob Suggs]

I did a little research relating to similar issues with the P2, Naza, and other DJI products. It seems that DJI assumes a declination of zero on launch but that the flight controller "learns" the proper declination as you fly. Also, it forgets this information when you power down. This matches what I am seeing with the Inspire. Relative to the P2, the Inspire's toilet-bowl effect is a bit more scary because the aircraft moves more quickly. I sent an email to DJI support asking if they had any advice on an after takeoff calibration dance that will settle the aircraft down before I do any precise moves. I don't have an answer yet.

 

[lrwskyfilms]

I did a little research relating to similar issues with the P2, Naza, and other DJI products. It seems that DJI assumes a declination of zero on launch but that the flight controller "learns" the proper declination as you fly. Also, it forgets this information when you power down. This matches what I am seeing with the Inspire. Relative to the P2, the Inspire's toilet-bowl effect is a bit more scary because the aircraft moves more quickly. I sent an email to DJI support asking if they had any advice on an after takeoff calibration dance that will settle the aircraft down before I do any precise moves. I don't have an answer yet.

I still put my quads in a 10ft hover for at least 30secs before I fly, not sure it helps but it helps me to watch and listen for anything unusual.

 

[turbodronepilot]

Hey RolandRSA. ..maybe this is whats causing your toilet bowl issue. ..

Cool, when i was doing it i was on a Galaxy Tab. Gonna do a flight with my iPad today and test it out.
Thanks.

Hey RolandRSA. .I think j found the answer to the toilet bowl effect. .
do an imu calabration again..this time on a flat surface. .
Use a level with a bubble and get it perfectly level..some one mentioned using a stack of cards to shim it if necessary. .
once you calibrate it right you won't have to do another one unless you have a big crash..

 

[LeesburgAirlines]

Has anyone been able to find the Compass Calibration selection in the UI? I can't find it after my upgrade. I took a test flight without calibration to see if perhaps DJI has some new self-calibrating feature in the new firmware, and the aircraft was flawless right down to the auto-RTH. And . . . I'm not inclined to trust that one flight.

 

[The Editor]

Has anyone been able to find the Compass Calibration selection in the UI? I can't find it after my upgrade. I took a test flight without calibration to see if perhaps DJI has some new self-calibrating feature in the new firmware, and the aircraft was flawless right down to the auto-RTH. And . . . I'm not inclined to trust that one flight.

I never do a compass Calibration in the field, there is no need to and my views on the subject are well documented over various threads on this forum.
However, you can manually put the Inspire into calibration mode by moving the flight control switch quickly backward and forwards between P-GPS and Atti 5 times.

 

[Mazz]

If you press where it says Connected GPS mode in green or disconnected in red or grey it will bring up the menu. So top center button.

 

[gray52]

If it's slightly off to your RC then just turn your RC 360 degrees and that always works for me.

 

[Rob Suggs]

I never do a compass Calibration in the field, there is no need to and my views on the subject are well documented over various threads on this forum.
However, you can manually put the Inspire into calibration mode by moving the flight control switch quickly backward and forwards between P-GPS and Atti 5 times.

Hey Editor, I can't find your prior posts, but I want to hear your opinion. It makes no sense to me to recalibrate in the field near ground structures that do not exist in the air after I have meticulously calibrated in a controlled environment (wide open field). But, I do it because DJI says so. What is your thought?

 

[The Editor]

Hey Editor, I can't find your prior posts, but I want to hear your opinion. It makes no sense to me to recalibrate in the field near ground structures that do not exist in the air after I have meticulously calibrated in a controlled environment (wide open field). But, I do it because DJI says so. What is your thought?

Exactly my thoughts and a practice I have kept to for the last two years.
The only reason to do a compass calibration is to give the magnetometer a reference for the magnetic declination at your geographic location.
By doing repeated calibrations you run the risk of unknowingly introducing an error by calibrating near a hidden metallic object. The mod values will adjust for this object but once airborne you are then clear of this anomoly and only the magnetic flux for your declination is acting upon your compass. Unfortunately because a skewed calibration was done on the ground your mod values are now out of the optimum range and your AC flies like it's drunk or worse causes inexperienced pilots to crash.
I have only ever calibrated my compass in a known trusted location.
As far as IMU calibrations, I have done three, one after each FW update and that's it!

 

[Rob Suggs]

Exactly my thoughts and a practice I have kept to for the last two years.
The only reason to do a compass calibration is to give the magnetometer a reference for the magnetic declination at your geographic location.
By doing repeated calibrations you run the risk of unknowingly introducing an error by calibrating near a hidden metallic object. The mod values will adjust for this object but once airborne you are then clear of this anomoly and only the magnetic flux for your declination is acting upon your compass. Unfortunately because a skewed calibration was done on the ground your mod values are now out of the optimum range and your AC flies like it's drunk or worse causes inexperienced pilots to crash.
I have only ever calibrated my compass in a known trusted location.
As far as IMU calibrations, I have done three, one after each FW update and that's it!

Makes perfect sense to me. Are there situations where you would recommend a recalibration? New firmware - yes. Travel to a vastly new location by plane - yes. Are there others?

 

[The Editor]

Makes perfect sense to me. Are there situations where you would recommend a recalibration? New firmware - yes. Travel to a vastly new location by plane - yes. Are there others?

I have never come across any personally. I have travelled 300 miles and not calibrated without issue.
One thing I would add is I ALWAYS check my mod values (accelerometer, gyro and compass) before EVERY flight. If something isn't right I don't fly from that spot.
It is a practice that has served me well this far.

 

[PB30X]

I have never come across any personally. I have travelled 300 miles and not calibrated without issue.
One thing I would add is I ALWAYS check my mod values (accelerometer, gyro and compass) before EVERY flight. If something isn't right I don't fly from that spot.
It is a practice that has served me well this far.

One of the Best features to have in my opinion[emoji6]! Didn't know anything about it until it was discussed here! Beings I was and still am a Phantom pilot, I didn't have this tech stuff readily available unless you had or have a vision.. Never old enough to still learn[emoji6]!! As stated I only do IMU or calibrations when prompted, otherwise I just do the normal pre flight sequence and checks.. This forum as well as others have a wealth of knowledge, be patient and READ ALONG[emoji6]!!!

 

[LeesburgAirlines]

Has anyone been able to find the Compass Calibration selection in the UI? I can't find it after my upgrade. I took a test flight without calibration to see if perhaps DJI has some new self-calibrating feature in the new firmware, and the aircraft was flawless right down to the auto-RTH. And . . . I'm not inclined to trust that one flight.

Exactly my thoughts and a practice I have kept to for the last two years.
The only reason to do a compass calibration is to give the magnetometer a reference for the magnetic declination at your geographic location.
By doing repeated calibrations you run the risk of unknowingly introducing an error by calibrating near a hidden metallic object. The mod values will adjust for this object but once airborne you are then clear of this anomoly and only the magnetic flux for your declination is acting upon your compass. Unfortunately because a skewed calibration was done on the ground your mod values are now out of the optimum range and your AC flies like it's drunk or worse causes inexperienced pilots to crash.
I have only ever calibrated my compass in a known trusted location.
As far as IMU calibrations, I have done three, one after each FW update and that's it!

Thanks to everyone for your great insights and information about this issue. It's been extremely helpful and ultimately a flight time saver.