两个经纬度点之间计算距离【经纬度距离计算】

/**
 * 测量方法来自百度地图
 */
public class MapDistance {
	private double DEF_PI = 3.14159265359; // PI
	private double DEF_2PI = 6.28318530712; // 2*PI
	private double DEF_PI180 = 0.01745329252; // PI/180.0
	private double DEF_R = 6370693.5; // radius of earth
	private MapDistance(){}
	private static MapDistance instance;
	
	public static synchronized MapDistance getInstance(){
		if(instance == null){
			instance = new MapDistance();
		}
		return instance;
	}
	/**
	 * 返回为m，适合短距离测量
	 * 
	 * @param lon1
	 * @param lat1
	 * @param lon2
	 * @param lat2
	 * @return
	 */
	public String 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 trans(distance);
	}
 
	/**
	 * 返回为m,适合长距离测量
	 * 
	 * @param lon1
	 * @param lat1
	 * @param lon2
	 * @param lat2
	 * @return
	 */
	public String 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 trans(distance);
	}
 
	private String trans(double distance) {
		boolean isBig = false; // 是否为大于等于1000m
		if (distance >= 1000) {
			distance /= 1000;
			isBig = true;
		}
		return (new DecimalFormat(".00").format(distance)) + (isBig ? "千米" : "米");
	}
 
}