GPS接收机模糊搜索粗时定位方法

由于难以获得免时定位算法所需的接收机概略位置,提出模糊搜索的粗时定位方法。为减小搜索空间,在位同步后优选几何精度因子值较好的4颗卫星通过遍历伪距模糊的方式进行位置估计,并基于伪距残余均方根最小准则选出最合理的位置估算结果。根据概略位置恢复所有卫星的完整伪距。利用5状态的免时定位算法估计接收机位置。使用11个国际卫星导航服务观测站的观测数据对算法进行验证,结果表明,在概略位置未知情况下该方法能够实现粗时定位,且定位精度与直接使用完整伪距的精时最小二乘定位精度相当。

A coarse-time GPS positioning algorithm with ambiguity search

The position can be estimated with partial pseudoranges. This technique is referred to as time-free positioning and requires a coarse receiver time, a priori position and GPS satellite ephemeris. The approximate receiver time can be kept with the real time clock (RTC). And the ephemeris can be stored in the receiver. So this leaves only the a-priori receiver position requirement. The coarse-time GPS positioning algorithm with ambiguity search was proposed to solve this problem. And this positioning method was discussing with bit synchronization. Once bit synchronization has been achieved, the receiver will have sub-20-milliseconds pseudoranges. The proposed positioning method can be described as the following procedure. First, four satellites were selected for coarse positioning. Iterate through all combinations of integer ambiguity and select the most reasonable combination based on minimum root mean square of residuals criterion. Then, the full pseudoranges of all satellites were constructed. Finally, the position was estimated using time-free positioning algorithm. The performance of the proposed method was verified by using the observation data of IGS stations. And this method provides comparable positioning results as compared with the traditional precise-time positioning.