说明：  多星座导航系统GDOP递推特性的仿真程序,程序主要是争对在现有系统中增加一颗现有星座的可见星时GDOP的变化情况组合仿真
(GDOP recursive multi-constellation navigation system features simulation program, the program is primarily a struggle for an increase in the existing system, the existing constellation of stars visible changes in the combination of simulation GDOP)