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Compass Calibration Guide

msinger

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Why Calibrate?
Compass calibration is important to safe, controlled flight. It compensates for changing background magnetic "noise", a.k.a. magnetic inclination and deviation. Inclination and deviation that isn't corrected through compass calibration will cause inconsistencies between GPS and compass that can result in "toilet bowl effect", a swirling motion that can cause the X-Star to fly out of control.

What is Magnetic Inclination and Deviation?
Magnetic deviation is a horizontal variation that comes from the X-Star itself and the equipment you have installed on it as well as the magnetic makeup of the area you are flying. Sometimes the deviation will be insignificant, but other times it can be big enough to cause you to lose control. Inclination is a vertical magnetic variation that shifts depending on where you are.

Warning Signs
The X-Star can only detect when the compass is providing extremely poor (implausible) data. This typically occurs if you place it near a strong magnetic field or do not calibrate it properly. The X-Star will indicate a compass error in the Starlink app.

IMPORTANT: The lack of a compass error does NOT mean your compass is working and calibrated properly.

What Does Calibration Actually Do?
Calibration measures the magnetic fingerprint of the surrounding area. By turning the compass 360 degrees, the X-Star can see where the compass reading doesn't smoothly increase or decrease. It uses this information to build an adaption table so that when the X-Star turns during flight, the reading is smooth and linear.

When Should I Calibrate?
You do not need to calibrate before every flight and in some cases you definitely should not calibrate. That doesn't mean you shouldn't ever bother doing it. It only takes one time for it to go very wrong. The most important aspect of compass calibration is making sure the magnetic "neighborhood" around your X-Star is consistent between calibration and during flight.

IMPORTANT: The ideal place to calibrate is an open field with nothing metallic in a 20ft radius. Keep away from drainage pipes, irrigation systems, rocks, etc.
  • DO Calibrate
    • Compass error is reported in the Starlink app (check area for possible interference first).
    • Circling in flight (also check for other possible causes).
    • New equipment added or removed / new firmware installed.
    • Location change (greater than ~100 miles).
    • Significant change in terrain (e.g. to/from mountains).
    • If you just degaussed your compass (don't degauss unless instructed).
  • DO NOT Calibrate
    • If near concrete, buildings, and hidden or overhead power lines, pipes, etc.
    • If you're indoors, on a paved surface, on a stone surface, on the beach, on a boat, on a balcony, near a car, near speakers, etc.
    • If there are metallic (ferrous) objects nearby or you're not sure
  • Pre-Calibration Checklist
    • Everything used in flight should be powered during calibration, e.g. GoPro, tracker, etc.
    • Remove all metal from within 10 ft radius (e.g. watch, phone, ring, belt, coins, remote controller).
    • Calibrate on grass or dirt and not on concrete, asphalt.
    • Calibrate on a level surface if possible.
    • A cardboard box is a good idea to get it off the ground and level.
  • How to Calibrate
    • Power on X-Star and remote controller.
    • Connect your mobile device to the X-Star remote controller.

    • Open the Starlink app on your mobile device,then tap "Settings" --> "Flight Control Settings" --> "Compass Calibration" --> "Calibrate". Once the calibration process is initiated, you will see the four LEDs on the drone flash yellow.

      Note: You can also start the calibration process with the remote controller instead of using the Starlink app. Simply press and hold the Take Off/Land button and Home button simultaneously for 3 seconds.

    • Hold the aircraft by its arms (not the landing gear), and rotate your body and aircraft 360° horizontally. The four LEDs on the aircraft will flash yellow during the process, and then will flash green when the calibration is successful.

    • Turn the aircraft 90° so the battery is facing up. Repeat the 360° rotation, this time holding the aircraft with the battery facing up. When calibration is successful, the app will alert you, and the four LEDs on the aircraft will turn solid green for five seconds before returning to normal indicating mode.

      Note: If the calibration is unsuccessful, the four LEDs on the aircraft will turn solid yellow. Start the compass calibration again at Step 1. If the compass calibration repeatedly fails, contact [email protected].

─────────────────────────────────────────────────────────
Note: A lot of this information was copied over from ianwood's thread in the Phantom Pilots forum.
 

TomKnAL

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...
Note:
You can also start the calibration process with the remote controller instead of using the Starlink app. Simply press and hold the Take Off/Land button and Home button simultaneously for 3 seconds.
  • Hold the aircraft by its arms (not the landing gear), and rotate your body and aircraft 360° horizontally. The four LEDs on the aircraft will flash yellow during the process, and then will flash green when the calibration is successful.

    Turn the aircraft 90° so the battery is facing up. Repeat the 360° rotation, this time holding the aircraft with the battery facing up. When calibration is successful, the app will alert you, and the four LEDs on the aircraft will turn solid green for five seconds before returning to normal indicating mode
This does not match what I see. The lights start out as flashing yellow. At some point during horizontal calibration they go solid green, which is when I tilt the X-Star forward. Then they start flashing green quickly, going solid green when calibration is successful.

The advice against calibrating on a beach surprised me.

I generally try to calibrate on grass but there have been times that asphalt was the only practical option. Are you suggesting that I should not fly if I can't find a grassy spot? Last weekend I calibrated on a gravel parking lot, with fairly large rocks in the gravel.
 

DronerOwner

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Yesterday I had an experience with this. I was at a park with no grass nearby so I calibrated over asphalt and there were rocks and possibly culverts nearby. Rec'd confirmation the compass was calibrated. I took off and flew around for a few minutes, ascended to 400', flew away and initiated a RTH. The XSP dropped normally to about 100 feet then went into the "toilet bowl" dive. Luckily, trees broke the fall and prevented the drone from crashing really hard OR going into the nearby river. Broke 2 propellers but otherwise no visible damage. I shut down the XSP then restarted. I tried recalibration and again got a positive reading from the app and drone. This time I only went up 400' and away ~100' and initiated a RTH. The XSP dropped properly to about 10' and then started drifting sideways slowly. I tired to regain control with no luck and the drone eventually hit the ground and flipped over but sustained only a few scratches. Needless to say, I put the drone away and came home. When I got home, I cranked up the drone and app and immediately got a "magnetic interference" warning on the controller. I shut down everything, then cranked it back up again, recalibrated, and it's been working properly since.

Nothing like that type experience to remind one to be diligent with these things.
 

brian bwin

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The XSP dropped normally to about 100 feet then went into the "toilet bowl" dive.
Just for the future (you may already know by now but others might not) make sure to enable ATTI mode in the Starlink app. This gives you the ability to switch to ATTI on the controller in the event of a compass error/magnetic interference and land manually. Glad you escaped without serious harm!

Definitely find a wide open field to do a clean calibration and don't re-calibrate unless the conditions listed above are present.
 

Guy

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Just for the future (you may already know by now but others might not) make sure to enable ATTI mode in the Starlink app. This gives you the ability to switch to ATTI on the controller in the event of a compass error/magnetic interference and land manually. . . ..
I was a little concerned about this before my first flight with the XSP. I had heard somewhere of someone inadvertently switching the mode selector the wrong way and going into ATTI mode by mistake, so from that perspective I liked the ability of being able to lock it out of that mode in the settings; however, for the reason that Brian just pointed out, I was also concerned that I might need that ATTI mode in case of a compass malfunction. I was under the impression that the XSP would move into ATTI mode regardless of the settings if there was a mag interference compass malfunction. Nonetheless I took the path that he suggested and enabled the ATTI right off of the bat.

After the initial compass calibration, I had not been re-calibrating but saw an Autel video that suggested that it was a good idea to calibrate before every flight, so today I re-calibrated pre-flight and then at about 250 ft. lost the compass. Fortunately, it was still close by and I was able to wrangle it back to the ground without incident despite moderate winds. I will say that it did get my adrenaline going though. If it had been at a greater distance, it would have been a real challenge to get a bearing on the the direction of the quad. Hence I am taking this as a wake-up call to make sure that I am always mentally aware of my aircraft's orientation without looking at the screen/controller.

Wish that I had read this post earlier as I fear that my well-intended re-calibration must have been too close to something. I have not experienced the "toilet bowl" effect yet; however, I think that based upon today's experience I will cancel my thoughts of performing this before each session / location as originally prescribed unless I believe that there is a good reason for doing so and after re-calibrating, staying close to home until I am comfortable that there are no issues.
 
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LuvMyTJ

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My personal philosophy is to only calibrate the compass when it asks me to, or if I travel 100 miles from where I last calibrated.
 

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