计算双基地雷达的GDOP值。有两个函数。根据里面的参数说明来计算。需要明白GDOP如何计算的同学可以参考一下。-shows a psuedocolor image of the PDOP (GDOP in 2-D is referred to as PDOP). xmin/xmax/ymin/ymax are the limits on the plot. SVs is an [x,y] matrix showing the position of the "Space Vehicles" (G