DistanceUtils.java

package com.itbox.grzl.map;

import com.baidu.platform.comapi.basestruct.GeoPoint;

/**
 * 距离计算
 * 
 * @author hyh creat_at：2013-9-22-上午9:18:13
 */
public class DistanceUtils {
	
	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
	static double DEF_R = 6378137;
	
	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)
		dy = DEF_R * (ns1 - ns2); // 南北方向长度(在经度圈上的投影长度)
		// 勾股定理求斜边长
		distance = Math.sqrt(dx * dx + dy * dy);
		return distance;
	}

	public static double GetLongDistance(double lon1, double lat1, double lon2, double lat2){
		double ew1, ns1, ew2, ns2;
		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;
		// 求大圆劣弧与球心所夹的角(弧度)
		distance = Math.sin(ns1) * Math.sin(ns2) + Math.cos(ns1) * Math.cos(ns2) * Math.cos(ew1 - ew2);
		// 调整到[-1..1]范围内，避免溢出
		if (distance > 1.0)
			distance = 1.0;
		else if (distance < -1.0)
			distance = -1.0;
		// 求大圆劣弧长度
		distance = DEF_R * Math.acos(distance);
		return distance;
	}
	
	public static boolean CompareGeoPoint(GeoPoint gp1,GeoPoint gp2){
		if(gp1 == null || gp2 == null){
			return false;
		}
		if(gp1.equals(gp2)){
			return true;
		}
		if(gp1.getLatitudeE6()/100 == gp2.getLatitudeE6()/100 && gp1.getLongitudeE6()/100 == gp2.getLongitudeE6()/100){
			return true;
		}
		return false;
	}
}