说明：  关于导航定位中的卡尔曼滤波程序。X1，X2分别代表经过转换以后的位置X,Y轴的坐标。V1，V2为其相对应的速度。卡尔曼滤波可以使定位数据更加平滑。
(Calman filtering program in navigation and positioning. X1, X2, respectively, after conversion to the position of the X, Y axis coordinates. V2, V1 for its relative speed. Calman filter can make the positioning data more smooth.)