计算两个经纬度之间的距离

// 计算距离常量
private static final double EARTH_RADIUS = 6378137;


/**
* 根据两点间经纬度坐标（double值），计算两点间距离，单位为米
* 
* @param x1
* @param y1
* @param x2
* @param y2
* @return
*/
public static double getDistance(double x1,double y1,double x2,double y2) {


double radLat1 = rad(y1);
double radLat2 = rad(y2);
double a = radLat1 - radLat2;
double b = rad(x1) - rad(x2);
double s = 2 * Math.asin(Math.sqrt(Math.pow(Math.sin(a / 2),2)
+ Math.cos(radLat1) * Math.cos(radLat2)
* Math.pow(Math.sin(b / 2),2)));
s = s * EARTH_RADIUS;
s = Math.round(s * 10000) / 10000;
return s;

}


private static double rad(double d) {
return d * Math.PI / 180.0;
}