说明：  GPS定位中调用的选星子程序，依据每颗卫星贡献的GDOP值的大小进行选星，其中又分为递推选星和直接选星。考虑到机动载体存储空间限制，选星为4颗或6颗。而6颗卫星的GDOP值更接近所有卫星时的值，且计算量小。
(GPS positioning called planetesimals selection process, based on the contribution of each satellite GDOP value of the selected size of stars, which are divided into the selection of satellite delivery, and direct elections stars. Taking into account the motor vehicle storage space constraints, the election of four stars, or 6. The six satellites, GDOP value is closer to the value of all the satellites, and the computation amount.)