經緯度方位計算方法：
2點經緯度計算方位，先計算二者的方位角度：該方法得出方位是點A相對於B的逆時針方向
/// <summary>
/// 根據經緯度計算角度
/// </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; //北半球的情況，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爲參考點座標
{
if (w1 > w2) ret += 180;
else ret = 180 - ret;
}
else if (w1 > w2) ret = 360 - ret;
return ret;
}
根據角度區分方位：簡單的區分8個方位
/// <summary>
/// 計算方位 按360計算
/// </summary>
/// <param name="lat1">參照物緯度</param>
/// <param name="lng1">參照物經度</param>
/// <param name="lat2">目標緯度</param>
/// <param name="lng2">目標經度</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 "東";
if ((jiaodu > 10) && (jiaodu <= 80)) return "東北";
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 "東南";
return string.Empty;
}