北斗三号卫星授时系统精度是多少？
The BeiDou-3 global satellite navigation system has a total of 45 service satellites in orbit, including 15 BeiDou-2 satellites and 30 BeiDou-3 satellites, and the current BeiDou system operates continuously and stably, with a global horizontal positioning accuracy of about 1.52 meters and a vertical positioning accuracy of about 2.64 meters; the speed measurement accuracy is better than 0.1 m/sec, and the timing accuracy is better than 20 nanoseconds.