FriedChicken_II
lvl.4
Flight distance : 721555 ft
Hong Kong
Offline
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Let me explain how the compass in your drone, your phone, or almost any digital devices is working today.
1. Your device usually has a 3-axis magnetometer. A 1-axis magnetometer also works but needs to be calibrated more frequently and it's almost not used anymore. The magnetometer is used to detect the direction of the magnetic field around it. The 3 axes magnetometer can figure out where the magnetic field is pointing and the strength of it immediately, while the 1 axis magnetometer needs other supporting informations but also can complete its job. The meters would generate a magnetic vector. We need the magnetic vector to figure out real world yaw angles.
2. Your device has an acceleration meter, or accelerometer, or gravity sensor. This is also a 3 axis sensor that is used to figure out the direction of gravity, or, the pitch angle of your drone.
3. Your device has a gyroscope. That is used to determine the angles that you've turned your drone. As we've known the pitch angle, now we also knows relative roll and yaw angles. Combined with realworld yaw angles that we've metered with the magnetometer, we know all angles on all axes now. However,
4. Your drone has other parts that may generate interference on the magnetic field. This usually can be considered as a constant interference so we can subtract it by using "calibrating compass".
5. The firmware of your drone keeps track of the "confidence level" of the compass. If it gets close to a strong magnetic interference source, this would be recorded, and the firmware would immediately lower the confidence of the compass. When it's lowered too much that the firmware cannot trust the compass anymore, the pop up of "need to calibrate" would appear.
6. Usually when you're not very close to the polar axis of earth, your turning angles recorded on gyroscope should be matching close to the turning angles recorded on your magnetometer. When these two doesn't match close enough, the firmware would lower the confidence of compass. When you get further away from the magnetic source, when you're turning the drone, the firmware constantly calibrates the compass and calculates the difference between the two angles measured. When the two angles are close enough again, considered by the firmware, it regains the confidence on compass.
7. In an ideal world without interference your 3 axes magnetometer's sampled magnetic vectors can build up a sphere around your drone. Because, when you're turning the drone, without any interference, the magnetic field of earth doesn't change. So the metered magnetic vector is always pointing to north, and has a constant strength. What happens when you turn your drone in 3 axes? This vector fills a sphere-like space.
8. In real world, due to the magnetic interferences that is close to your drone's sensor, the vector might change its direction and strength when turning your drone. Now the sampled vectors can only build up a strange potato like thing. Thankfully due to that these interfering parts on your drone also turns with your drone, this means that it builds a constant magnetic interference field that can be subtracted easily, if sampled in all axes/directions.
9. So there're two cases that you need to recalibrate the compass:
a. the firmware lost track of compass confidence (happened to many DJI Mini 2 pilots in earlier firmware). Things like power-off can cause this to happen if the function was not implemented properly.
b. the firmware lost confidence on compass due to mismatches between angles of magnetic vectors and attitude vectors.
10. But, anyway, you don't need ANY SCREEN to do the calibration. As I have stated, the calibration is a constant and automatic process.
11. If you turn your drone 360 degrees around 3 axes when it's powered on, then the compass would be able to filter out those interferences on drone and rebuild the confidence on compass when there's no strong magnetic interference around.
Read this before you post again:
https://docs.microsoft.com/en-us ... redirectedfrom=MSDN
I don't own a Mini 1, but I do own a Mini 2 and it was constantly requiring for calibration after almost every reboot due to firmware issues. I don't even use the calibration function in DJI Fly, simply turn the drone on 3 axes and the pop up is gone.
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