判斷一個經緯度是不是在一個范圍內

        /// <summary>
        /// 判斷經緯度是否在范圍類
        /// </summary>
        /// <param name="longitudeCur">經度</param>
        /// <param name="latitudeCur">緯度</param>
        /// <param name="pathList"></param>
        /// <returns></returns>
        public static bool IsInRegion(double longitudeCur, double latitudeCur, IList<RegionPath> pathList)
        {
            if (pathList.Count < 3)//點小於3無法構成多邊形
            {
                return false;
            }
            int iSum = 0;
            int pathCount = pathList.Count;
            double longStart = 0, latiStart = 0, longEnd = 0, latiEnd = 0;
            double dLong = 0;
            for (int i = 0; i < pathCount; i++)
            {
                int nextIndex = i + 1;
                if (i == pathCount - 1)
                {
                    nextIndex = 0;
                }
                longStart = pathList[i].Longitude;
                latiStart = pathList[i].Latitude;
                longEnd = pathList[nextIndex].Longitude;
                latiEnd = pathList[nextIndex].Latitude;

                //判斷緯度即Y坐標是否在2點的Y坐標內，只有在其內水平線才會相交
                if ((latitudeCur >= latiStart && latitudeCur < latiEnd) || 
                    (latitudeCur >= latiEnd && latitudeCur < latiStart)) 
                {
                    if (Math.Abs(latiStart-latiEnd)>0)
                    {
                        dLong = longStart - ((longStart - longEnd) * (latiStart - latitudeCur)) / (latiStart - latiEnd);
                        if (dLong < longitudeCur)
                        {
                            iSum++;
                        }
                    }
                }
            }

            if ((iSum % 2) != 0)
            {
                return true;
            }
            return false;
        }