椭球距离计算的java实现（转）

本文代码转自： http://www.blogjava.net/sinoly/archive/2007/01/22/95406.html

今天遇到了一个距离计算的问题，经过查资料，大概知道了原理，而且还找到这个非常牛的类，谢谢前人的栽树，再此致敬，代码如下：

package com.geotools.test;

/**
 * 
 * CopyRight (C)    All rights reserved.<p>
 * 
 * WuHan Inpoint Information Technology Development,Inc.<p>
 * 
 * Author sinoly<p> Project Name: PostGeo
 *
 * @version 1.0    2006-11-13
 *
 * <p>Base on : JDK1.5<p>
 *
 */ 
public class GeoUtils {
    public enum GaussSphere{
        Beijing54,
        Xian80,
        WGS84,
    } 
    private static double Rad(double d){
        return d * Math.PI / 180.0;
    }
 public double DistanceOfTwoPoints(double lng1,double lat1,double lng2,double lat2,
   GaussSphere gs){
        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 * (gs == GaussSphere.WGS84 ? 6378137.0 : (gs == GaussSphere.Xian80 ? 6378140.0 : 6378245.0));
        s = Math.round(s * 10000) / 10000;
        return s;
 }
}