java 已知两个地点经纬度算距离（非常精确）

java 已知两个地点经纬度算距离（非常精确）

package com.lbnet.lzx.util;

public class GoogleMap {
 
 
  private static final double EARTH_RADIUS = 6378.137;
  private static double rad(double d)
  {
     return d * Math.PI / 180.0;
  }
 /**
  * ????}?????????????/γ???
  * @param lat1
  * @param lng1
  * @param lat2
  * @param lng2
  * @return
  */
  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 * 10000) / 10000;
     return s;
  }
  public static double D_jw(double wd1,double jd1,double wd2,double jd2)
  {
      double x,y,out;
      double PI=3.14159265;
      double R=6.371229*1e6;

      x=(jd2-jd1)*PI*R*Math.cos( ((wd1+wd2)/2) *PI/180)/180;
      y=(wd2-wd1)*PI*R/180;
      out=Math.hypot(x,y);
      return out/1000;
  }

 public static void main(String args[]){
  //31.1795100,121.3944810
  System.out.println(GoogleMap.D_jw(31.192609,121.431577,31.1822952,121.4314814));
  }
}