判断一个经纬度在另外一个经纬度的方向

package com.gis.launcher;

/**
 * Created by fc.w on 2017/12/7.
 */
public class LngLatDirection {

    public static void main(String[] args) {
        LngLatDirection lngLatDirection = new LngLatDirection();
        String str=getDirection(22.68324400, 114.11061200, 30.06430000,  121.18618900);
        System.out.println(str);
    }

    /**
     *
     * @param lat1    纬度1
     * @param lng1    经度1
     * @param lat2    纬度2
     * @param lng2    经度2
     * @return        方向
     */
    public static String getDirection(double lat1, double lng1, double lat2,double lng2) {
        double jiaodu = getAngle(lat1, lng1, lat2, lng2);
        if ((jiaodu <= 10) || (jiaodu > 350))
            return "东";
        if ((jiaodu > 10) && (jiaodu <= 80))
            return "东北";
        if ((jiaodu > 80) && (jiaodu <= 100))
            return "北";
        if ((jiaodu > 100) && (jiaodu <= 170))
            return "西北";
        if ((jiaodu > 170) && (jiaodu <= 190))
            return "西";
        if ((jiaodu > 190) && (jiaodu <= 260))
            return "西南";
        if ((jiaodu > 260) && (jiaodu <= 280))
            return "南";
        if ((jiaodu > 280) && (jiaodu <= 350))
            return "东南";
        return "";
    }

    public static double getAngle(double lat1, double lng1, double lat2,double lng2) {
        double x1 = lng1;
        double y1 = lat1;
        double x2 = lng2;
        double y2 = lat2;
        double pi = Math.PI;
        double w1 = y1 / 180 * pi;
        double j1 = x1 / 180 * pi;
        double w2 = y2 / 180 * pi;
        double j2 = x2 / 180 * pi;
        double ret;
        if (j1 == j2) {
            if (w1 > w2)
                return 270; // 北半球的情况，南半球忽略
            else if (w1 < w2)
                return 90;
            else
                return -1;// 位置完全相同
        }
        ret = 4* Math.pow(Math.sin((w1 - w2) / 2), 2)- Math.pow(
                Math.sin((j1 - j2) / 2) * (Math.cos(w1) - Math.cos(w2)),2);
        ret = Math.sqrt(ret);
        double temp = (Math.sin(Math.abs(j1 - j2) / 2) * (Math.cos(w1) + Math
                .cos(w2)));
        ret = ret / temp;
        ret = Math.atan(ret) / pi * 180;
        if (j1 > j2){ // 1为参考点坐标
            if (w1 > w2)
                ret += 180;
            else
                ret = 180 - ret;
        } else if (w1 > w2)
            ret = 360 - ret;
        return ret;
    }

}