高德地圖 GPS 轉地址，座標轉地址，

通過調用高德的WebApi，將經緯度轉換爲地址描述。

        const string KEY = "這個地方填寫你申請的高德WebAPIKey";
        /// <summary>
        /// 根據GPS地址獲取中文詳細地址
        /// </summary>
        /// <param name="lon">經度</param>
        /// <param name="lat">維度</param>
        /// <param name="radius">匹配半徑，單位爲米</param>
        /// <returns>中文詳細地址</returns>
        public static string GPSToPositionString(double lon, double lat, int radius = 1000)
        {
            WebClient server = new WebClient();
            string url = String.Format("http://restapi.amap.com/v3/geocode/regeo?location={0},{1}&key={2}&radius={3}&extensions=base", lon, lat, KEY, radius);
            var replyBuffer = server.DownloadData(url);
            var reply = System.Text.Encoding.UTF8.GetString(replyBuffer);
            if (String.IsNullOrEmpty(reply))
                return "";
            JObject result = (JObject)JsonConvert.DeserializeObject(reply);
            if (result["status"].Value<string>() == "1")
            {
                var regeocode = result["regeocode"];
                var formatted_address = regeocode["formatted_address"];
                return formatted_address.Value<string>();
            }
            else
                return "";
        }