The North-seeking coordinate system of MEMS gyroscope

[kellyyu]

Before understanding north seeking, we need to know the three common north directions: true north, magnetic north and coordinate north. True north refers to the tangential direction connecting the North and South Pole of the Earth, and the direction of true north is fixed. Magnetic north is the end point of all magnetic meridians in the direction of the Earth’s magnetic force, and it changes with changes in the Earth’s magnetic field. Coordinate north is a zonal projection of true north, which is consistent with true north only at the central meridian, and deviations in the meridian convergence angle will occur in other places. The figure shows the relationship between these three north directions.

MEMS gyro searches north through the carrier coordinate system. The carrier coordinate system has different forms of coordinate systems depending on the carrier. In the figure, we refer to it as the b system for short. The carrier coordinate system records the attitude information of the carrier. Figure 5 shows the carrier coordinate system. Xb, Yb, and Zb point to three different directions respectively. Through the carrier coordinate system, the carrier attitude in the three directions of pitch, roll and heading can be measured.


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