源代码地址：http://files.cnblogs.com/psunny/SafetyNetMobileHttpService.rar

我在使用Windows Mobile向http://www.google.com/loc/json请求基站信息时，发现第一次发送基站信息能够获取到一个经纬度，第二次却失败，直接导致异常退出应用程序。由于基站信息只能在真机上才能获取，无法进行调试，我就以一个中间web页面来向手机发送位置信息，再者拼接Json和解析的Json都放在web上进行处理，也减少Windows Mobile应用程序的负担，Windows Mobile只单纯的负责接收一个经纬度字符串。

1. 具体思路

首先要清楚一点的是，每一个基站都能够通过请求http://www.google.com/loc/json获取到一个经纬度。如果用户能够在短时间内获取到较多的基站信息，比如4个或5个，可以通过这几个基站的经纬度计算出比较准确的用户位置。

举个例子，比如我在WM上取到4个基站信息：

50554,9513,460,1

50325,9513,460,1

50584,9513,460,1

50041,9513,460,1

每一行的4个数值分别对应：CID, LAC, MCC, MNC

说明：
CID——CellID，表示基站号 LAC——Location Area Code，表示区域编号 MCC——Mobile Country Code，表示国家编号，中国是460 MNC——Mobile Network Code，表示移动网络编号，移动是0，联通是1 更详细的MCC, MNC信息可以查看：http://en.wikipedia.org/wiki/Mobile_Network_Code

然后向Google发送基站信息是通过JSON串以Post的形式发送到http://www.google.com/loc/json，然后它会返回一个包含经纬度信息的JSON串。

RequestJson范例

{"version": "1.1.0","host": "maps.google.com","cell_towers": [    {"cell_id": 42,"location_area_code": 415,"mobile_country_code": 310,"mobile_network_code": 410,"age": 0,"signal_strength": -60,"timing_advance": 5555    },    {"cell_id": 88,"location_area_code": 415,"mobile_country_code": 310,"mobile_network_code": 580,"age": 0,"signal_strength": -70,"timing_advance": 7777    }  ],"wifi_towers": [    {"mac_address": "01-23-45-67-89-ab","signal_strength": 8,"age": 0    },    {"mac_address": "01-23-45-67-89-ac","signal_strength": 4,"age": 0    }  ]}

然后从google那边返回来的位置信息如下：

ResponseJson样例

{"location": {"latitude": 51.0,"longitude": -0.1,"altitude": 30.1,"accuracy": 1200.4,"altitude_accuracy": 10.6,"address": {"street_number": "100","street": "Amphibian Walkway","postal_code": "94043","city": "Mountain View","county": "Mountain View County","region": "California","country": "United States of America","country_code": "US"    }  },"access_token": "2:k7j3G6LaL6u_lafw:4iXOeOpTh1glSXe"}

说明：
即使只发送一个基站信息，也能够获取到一个经纬度。以上的RequestJson和ResponseJson只是样例，在实际Windows Mobile运用中，有可能取不到timing_adavance和singal_strength这两个参数，结合这两个参数定位会更准确一些。在我的代码例子中，我只取了CID, LAC, MCC, MNC参数。 关于JSON串中的属性各代表什么意思，详细请看：http://code.google.com/intl/zh-CN/apis/gears/geolocation_network_protocol.html

从上面的两端代码中我们可以大致了解到如何向Google发送基站请求，获取经纬度，下面我就以简单的代码来实现获取经纬度的方法。其实了解了上面的代码后，我们主要的工作就是拼接RequestJson串和解析
ResponseJson串，解析Json串我使用的是JSON.NET。

2.实现

using System;

/// <summary>/// CellInfocs 的摘要说明/// </summary>public class CellInfo{public string cid;public string lac;public string mcc;public string mnc;

public string CID    {        get { return cid; }        set { cid = value; }    }

public string LAC    {        get { return lac; }        set { lac = value; }    }

public string MCC    {        get { return mcc; }        set { mcc = value; }    }

public string MNC    {        get { return mnc; }        set { mnc = value; }    }

}

using System;using System.Collections.Generic;using System.Text;using System.Net;using System.IO;using Newtonsoft.Json.Linq;

/// <summary>/// LocationService 的摘要说明/// </summary>public class LocationService{public static string ErrorMessage;

public LocationService(string postData)    {        GetLocationInfomation(postData);    }

/// <summary>/// 返回经纬度信息/// 格式如下：/// 22.506421,113.918245|22.497636,113.912647|22.496063,113.91121/// </summary>/// <param name="postData"></param>/// <returns></returns>public string GetLocationInfomation(string postData)    {        List<CellInfo> list = GetCellInfos(postData);        StringBuilder sb = new StringBuilder();

for (int i = 0; i < list.Count; i++)        {            CellInfo info = list[i];//基本步骤//1. 生成发往google的json串//2. 接收google返回的json串//3. 解析json串，只取得经纬度//4. 拼接经纬度string json = GenerateRequestJson(info);string content = GetResponseJson(json);string latLon = ParseResponseJson(content);

            sb.Append(latLon);            sb.Append("|");        }

return sb.ToString().Substring(0, sb.Length - 1);//return sb.ToString();    }

/// <summary>/// 接收从手机端发送过来的数据/// '|'分割对象，','分割属性/// </summary>/// <param name="postData"></param>/// <returns></returns>private List<CellInfo> GetCellInfos(string postData)    {string[] strInfos = postData.Split('|');        List<CellInfo> list = new List<CellInfo>();for (int i = 0; i < strInfos.Length; i++)        {string[] properties = strInfos[i].Split(',');            CellInfo info = new CellInfo();

            info.CID = properties[0];            info.LAC = properties[1];            info.MCC = properties[2];            info.MNC = properties[3];

            list.Add(info);        }return list;    }

/// <summary>/// 发送一个基站信息，并返回一个位置信息/// 位置信息是以json串的形式存在/// 需要对json串进行解析/// </summary>/// <param name="requestJson"></param>private string GetResponseJson(string requestJson)    {string responseJson = string.Empty;try        {            ServicePointManager.Expect100Continue = false;            System.Text.ASCIIEncoding encoding = new System.Text.ASCIIEncoding();byte[] data = encoding.GetBytes(requestJson);

            HttpWebRequest myRequest = (HttpWebRequest)WebRequest.Create(@"http://www.google.com/loc/json");

            myRequest.Method = "POST";            myRequest.ContentType = "application/requestJson";            myRequest.ContentLength = data.Length;            Stream newStream = myRequest.GetRequestStream();

// Send the data.             newStream.Write(data, 0, data.Length);            newStream.Close();

// Get response JSON string             HttpWebResponse myResponse = (HttpWebResponse)myRequest.GetResponse();

            StreamReader reader = new StreamReader(myResponse.GetResponseStream(), System.Text.Encoding.Default);            responseJson = reader.ReadToEnd();        }catch (Exception ex)        {            ErrorMessage = ex.Message;        }

return responseJson;    }

/// <summary>/// 解析从google Response的JSON串，获取经纬度/// </summary>/// <param name="responseJson"></param>/// <returns></returns>private string ParseResponseJson(string responseJson)    {        StringBuilder latLon = new StringBuilder();        JObject obj = JObject.Parse(responseJson);

string lat = obj["location"]["latitude"].ToString();string lon = obj["location"]["longitude"].ToString();

        latLon.Append(lat);        latLon.Append(",");        latLon.Append(lon);

return latLon.ToString();    }

/// <summary>/// 生成发往http://www.google.com/loc/json的json串/// 仅仅只有一个基站/// </summary>/// <param name="info"></param>/// <returns></returns>private string GenerateRequestJson(CellInfo info)    {

string json = "";        json += "{";        json += "\"version\":\"1.1.0\"" + ",";        json += "\"host\":\"maps.google.com\"" + ",";        json += "\"cell_towers\":[";

        json += "{";        json += "\"cell_id\":" + info.CID + ",";        json += "\"location_area_code\":" + info.LAC + ",";        json += "\"mobile_country_code\":" + info.MCC + ",";        json += "\"mobile_network_code\":" + info.MNC;        json += "}";

        json += "],";        json += "\"wifi_towers\": [{}]";        json += "}";

return json;    }}

中间的web页面：Default.aspx(发送请求时，就请求这个页面)

<%@ Page Language="C#" AutoEventWireup="true"  CodeFile="Default.aspx.cs" Inherits="_Default" %>

using System;

public partial class _Default : System.Web.UI.Page{

protected void Page_Load(object sender, EventArgs e)    {string postData = Request.Form["POST_DATA"];        ResponseLocation(postData);    }

/// <summary>/// 向手机端返回位置信息/// </summary>/// <param name="postData"></param>public void ResponseLocation(string postData)    {        LocationService service = new LocationService(postData);string location = service.GetLocationInfomation(postData);        Response.Write(location);    }}

测试页面：index.html

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml" ><head><title>Index Page</title></head><body><form id="form1" method="post" action="Default.aspx"><input name="POST_DATA" value=" 50554,9513,460,1|50325,9513,460,1|50584,9513,460,1|50041,9513,460,1"/><input type="submit"/></form></body></html>