在北斗和CAPS导航系统中利用高程作为虚拟星座可显著提高无源定位的精度.在授时应用中无源定位的结果用来计算卫星与用户的距离从而得到信号传输延迟.本文分析了高程误差对授时精度的影响.设定了高程误差,列出了定位方程;采用牛顿迭代法对方程进行了求解.方程的解表明高程误差主要影响定位结果的Z坐标值,而对授时敏感的距离值影响较小.因此高程误差导致的授时误差要小于定位误差.对5个中国城市的仿真结果表明在这些区域100m高程误差引起的授时误差要小于1μs.因此可以采用概略高程取代需要昂贵测试设备的精确高程.概略高程可以满足μs级授时精度的需求,从而满足电力和电信系统大部分场合对时间同步的需求.%Height can be used as virtual satellice to increase passive positioning aecuracy for COMPASS and CAPS system of China substantially. At timing application passive position result is used to calculate the distance between user and satellite to get the transmission delay. The passive timing accuracy when height used as virtual satellite is analyzed in this paper. Height error is set, and the positioning equation is formulated. Solving the equation by Newton method, it is well known that the Z coordinate of user is much sensitive to height error. At the same time the distance error between user and satellite caused by height error is much less. Simulation based on five cities of China is carried out. The result shows that timing error caused by 100m height error is less than 1μS in these regions. So height error is more suitable for timing. In many cases a probable height can be adopted instead of precise height which needs expensive devices. Probable height can meet the requirement of μs timing accuracy. It can be used for many case of power system and telecom system.
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