android 計算地圖上兩點距離的算法

android計算地圖上兩點距離的算法
接口：

    package com.computedistance;

    public interface DistanceComputeInterface {


    double getDistance(double lat1, double lng1, double lat2, double lng2);  

    double getShortDistance(double lat1, double lon1, double lat2, double lon2);  

    double getLongDistance(double lat1, double lon1, double lat2, double lon2);  

    double getDistanceBySpeed(double speed, double timeSpace);  

    double getAccurancyDistance(double lat_a, double lng_a, double lat_b, double lng_b);  

}  </pre> 


 實現類：
    package com.computedistance.impl;

    import java.security.InvalidParameterException;

    import com.baidu.mapapi.utils.DistanceUtil;

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

    import com.computedistance.DistanceComputeInterface;

    public class DistanceComputeImpl implements DistanceComputeInterface{


    private final static double DEF_PI = 3.14159265359; // PI  
    private final static double DEF_2PI= 6.28318530712; // 2*PI  
    private final static double DEF_PI180= 0.01745329252; // PI/180.0  
    private final static double DEF_R =6370693.5; // radius of earth  
    private static DistanceComputeImpl instance = null;  

    public synchronized static DistanceComputeImpl getInstance(){  
        if (instance == null) {  
            instance = new DistanceComputeImpl();  
        }  
        return instance;  
    }  

    private DistanceComputeImpl(){}  

    @Override  
    public double getDistance(double lat1, double lng1, double lat2, double lng2) {  
        GeoPoint p1LL = new GeoPoint((int) (lat1*1e6), (int) (lng1*1e6));  
        GeoPoint p2LL = new GeoPoint((int) (lat2*1e6), (int) (lng2*1e6));  
        double distance = DistanceUtil.getDistance(p1LL, p2LL);  
        return distance/1000;  
    }  

    @Override  
    public double getShortDistance(double lat1, double lon1, double lat2,double lon2) {  
        double ew1, ns1, ew2, ns2;  
        double dx, dy, dew;  
        double distance;  
        // 角度轉換為弧度  
        ew1 = lon1 * DEF_PI180;  
        ns1 = lat1 * DEF_PI180;  
        ew2 = lon2 * DEF_PI180;  
        ns2 = lat2 * DEF_PI180;  
        // 經度差  
        dew = ew1 - ew2;  
        // 若跨東經和西經180 度，進行調整  
        if (dew > DEF_PI)  
            dew = DEF_2PI - dew;  
        else if (dew < -DEF_PI)  
            dew = DEF_2PI + dew;  
        dx = DEF_R * Math.cos(ns1) * dew; // 東西方向長度(在緯度圈上的投影長度)  
        dy = DEF_R * (ns1 - ns2); // 南北方向長度(在經度圈上的投影長度)  
        // 勾股定理求斜邊長  
        distance = Math.sqrt(dx * dx + dy * dy);  
        return distance/1000;  
    }  

    @Override  
    public double getLongDistance(double lat1, double lon1, double lat2,double lon2) {  
        double ew1, ns1, ew2, ns2;  
        double distance;  
        // 角度轉換為弧度  
        ew1 = lon1 * DEF_PI180;  
        ns1 = lat1 * DEF_PI180;  
        ew2 = lon2 * DEF_PI180;  
        ns2 = lat2 * DEF_PI180;  
        // 求大圓劣弧與球心所夾的角(弧度)  
        distance = Math.sin(ns1) * Math.sin(ns2) + Math.cos(ns1) * Math.cos(ns2) * Math.cos(ew1 - ew2);  
        // 調整到[-1..1]范圍內，避免溢出  
        if (distance > 1.0){  
            distance = 1.0;  
        } else if (distance < -1.0){  
            distance = -1.0;  
        }  
        // 求大圓劣弧長度  
        distance = DEF_R * Math.acos(distance);  
        return distance/1000;  
    }  

    @Override  
    public double getDistanceBySpeed(double speed, double timeSpace) {  
        if (speed  < 0 || timeSpace <= 0) {  
            throw new InvalidParameterException();  
        }  
        return speed * timeSpace;  
    }  

    @Override  
    public double getAccurancyDistance(double lat_a, double lng_a,double lat_b, double lng_b) {  
        double pk = (double) (180 / 3.14169);  
        double a1 = lat_a / pk;  
        double a2 = lng_a / pk;  
        double b1 = lat_b / pk;  
        double b2 = lng_b / pk;  

        double t1 = Math.cos(a1) * Math.cos(a2) * Math.cos(b1) * Math.cos(b2);  
        double t2 = Math.cos(a1) * Math.sin(a2) * Math.cos(b1) * Math.sin(b2);  
        double t3 = Math.sin(a1) * Math.sin(b1);  
        double tt = Math.acos(t1 + t2 + t3);  
        return 6366000 * tt / 1000;  
    }  
}  </pre>