2点经纬度计算相对方位

项目中用到的经纬度方位计算方法：

2点经纬度计算方位，先计算二者的方位角度：该方法得出方位是点A相对于B的逆时针方向

    /// <summary>
        /// 根据经纬度计算角度
        /// </summary>
        /// <param name="lat1"></param>
        /// <param name="lng1"></param>
        /// <param name="lat2"></param>
        /// <param name="lng2"></param>
        /// <returns></returns>
       
        public static double GetJiaoDu(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;
        }

根据角度区分方位：简单的区分8个方位 

 /// <summary>
    /// 计算方位 按360计算
    /// </summary>
    /// <param name="lat1">参照物纬度</param>
    /// <param name="lng1">参照物经度</param>
    /// <param name="lat2">目标纬度</param>
    /// <param name="lng2">目标经度</param>
    /// <returns></returns>
    public static string GetDirection(double lat1, double lng1, double lat2, double lng2)
    {
        double jiaodu = GetJiaoDu(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 string.Empty;

    }

 欢迎指正!