With geomagnetic field model records, several kinds of secular variation of geomagnetic dipole moment and the position of the geomagneticNorthPole during the year 0 ~ 2000 a.
利用地磁场模型资料，计算和分析了公元0 ~ 2000年的地磁场偶极子磁矩和地磁北极位置的长期变化。
2
Y is tangential to the ground at the device's current location and points toward the geomagneticNorthPole.