根据经纬度计算两点之间的距离

/**
 * 百度地图 帮助类
 */
public class MapUtils {
    //private static double EARTH_RADIUS = 6378.137;
    private static double EARTH_RADIUS = 6371.393;

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

    /**
     * 计算两个经纬度之间的距离(单位/米)
     */
    public static double GetDistance(double lat1, double lng1, double lat2, double lng2)
    {
        double radLat1 = rad(lat1);
        double radLat2 = rad(lat2);
        double a = radLat1 - radLat2;
        double b = rad(lng1) - rad(lng2);
        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 * 1000);
        return s;
    }