百度地图计算2点间距离

package com.qianmosen.utils;
/**
 * 百度查看两点间距离
 * @author Administrator
 *
 */
public class BaiDuMap {
    static double DEF_PI = 3.14159265359; // PI
        static double DEF_2PI= 6.28318530712; // 2*PI
        static double DEF_PI180= 0.01745329252; // PI/180.0
        static double DEF_R =6370693.5; // radius of earth
                //适用于近距离
        public static double GetShortDistance(double lon1, double lat1, double lon2, double lat2)
        {
            double ew1, ns1, ew2, ns2;
            double dx, dy, dew;
            double distance;
            // 角度转换为弧度
            ew1 = lon1 * DEF_PI180;
            ns1 = lat1 * DEF_PI180;
            ew2 = lon2 * DEF_PI180;
            ns2 = lat2 * DEF_PI180;
            // 经度差
            dew = ew1 - ew2;
            // 若跨东经和西经180 度，进行调整
            if (dew > DEF_PI)
            dew = DEF_2PI - dew;
            else if (dew < -DEF_PI)
            dew = DEF_2PI + dew;
            dx = DEF_R * Math.cos(ns1) * dew; // 东西方向长度(在纬度圈上的投影长度)