1 前言

在导师公司实习了半个月，参加的是尾气遥测项目，我的任务是开发GPS 的相关事情，从零到有的开发出了 GPS 的 Winform 应用，在这里记录一下开发过程和简要的描述一下将 GPS 数据提取转换的过程。 

2 前期准备

2.1 GPS相关软硬件准备

VS2017 、UB373设备一枚（WGS－84原始坐标系）、安装驱动、VS2017 Nuget 安装 SharpGIS.NmeaParser 1.10.0 版本程序包 。

2.2 GPS相关知识储备

2.2.1 三种类型的地图坐标系了解一下

• WGS－84原始坐标系，一般用国际GPS纪录仪记录下来的经纬度，通过GPS定位拿到的原始经纬度，Google和高德地图定位的的经纬度（国外）都是基于WGS－84坐标系的；但是在国内是不允许直接用WGS84坐标系标注的，必须经过加密后才能使用；
• GCJ－02坐标系，又名“火星坐标系”，是我国国测局独创的坐标体系，由WGS－84加密而成，在国内，必须至少使用GCJ－02坐标系，或者使用在GCJ－02加密后再进行加密的坐标系，如百度坐标系。高德和Google在国内都是使用GCJ－02坐标系，可以说，GCJ－02是国内最广泛使用的坐标系；
• 百度坐标系:bd-09，百度坐标系是在GCJ－02坐标系的基础上再次加密偏移后形成的坐标系，只适用于百度地图。(目前百度API提供了从其它坐标系转换为百度坐标系的API，但却没有从百度坐标系转为其他坐标系的API)

2.2.2 GPS 数据位置发生偏移

由于坐标系之间不兼容，如在百度地图上定位的经纬度拿到高德地图上直接描点就肯定会发生偏移；只考虑国内的情况，高德地图和Google地图是可以不经过转换也能够准确显示的（在国内用的都是GCJ－02坐标系）；下面是收录了网上的WGS－84，GCJ－02，百度坐标系(bd-09)之间的相互转换的方法，经测试，是转换后相对准确可用的：

转换代码：

/**火星坐标系 (GCJ-02) 与百度坐标系 (BD-09) 的互转
* Created by macremote on 16/5/3.
*/
public class GPSUtil {
public static double pi = 3.1415926535897932384626;
public static double x_pi = 3.14159265358979324 * 3000.0 / 180.0;
public static double a = 6378245.0;
public static double ee = 0.00669342162296594323;

public static double transformLat(double x, double y) {
double ret = -100.0 + 2.0 * x + 3.0 * y + 0.2 * y * y + 0.1 * x * y
+ 0.2 * Math.sqrt(Math.abs(x));
ret += (20.0 * Math.sin(6.0 * x * pi) + 20.0 * Math.sin(2.0 * x * pi)) * 2.0 / 3.0;
ret += (20.0 * Math.sin(y * pi) + 40.0 * Math.sin(y / 3.0 * pi)) * 2.0 / 3.0;
ret += (160.0 * Math.sin(y / 12.0 * pi) + 320 * Math.sin(y * pi / 30.0)) * 2.0 / 3.0;
return ret;
}

public static double transformLon(double x, double y) {
double ret = 300.0 + x + 2.0 * y + 0.1 * x * x + 0.1 * x * y + 0.1
* Math.sqrt(Math.abs(x));
ret += (20.0 * Math.sin(6.0 * x * pi) + 20.0 * Math.sin(2.0 * x * pi)) * 2.0 / 3.0;
ret += (20.0 * Math.sin(x * pi) + 40.0 * Math.sin(x / 3.0 * pi)) * 2.0 / 3.0;
ret += (150.0 * Math.sin(x / 12.0 * pi) + 300.0 * Math.sin(x / 30.0
* pi)) * 2.0 / 3.0;
return ret;
}
public static double[] transform(double lat, double lon) {
if (outOfChina(lat, lon)) {
return new double[]{lat,lon};
}
double dLat = transformLat(lon - 105.0, lat - 35.0);
double dLon = transformLon(lon - 105.0, lat - 35.0);
double radLat = lat / 180.0 * pi;
double magic = Math.sin(radLat);
magic = 1 - ee * magic * magic;
double sqrtMagic = Math.sqrt(magic);
dLat = (dLat * 180.0) / ((a * (1 - ee)) / (magic * sqrtMagic) * pi);
dLon = (dLon * 180.0) / (a / sqrtMagic * Math.cos(radLat) * pi);
double mgLat = lat + dLat;
double mgLon = lon + dLon;
return new double[]{mgLat,mgLon};
}
public static boolean outOfChina(double lat, double lon) {
if (lon < 72.004 || lon > 137.8347)
return true;
if (lat < 0.8293 || lat > 55.8271)
return true;
return false;
}
/**
* 84 to 火星坐标系 (GCJ-02) World Geodetic System ==> Mars Geodetic System
*
* @param lat
* @param lon
* @return
*/
public static double[] gps84_To_Gcj02(double lat, double lon) {
if (outOfChina(lat, lon)) {
return new double[]{lat,lon};
}
double dLat = transformLat(lon - 105.0, lat - 35.0);
double dLon = transformLon(lon - 105.0, lat - 35.0);
double radLat = lat / 180.0 * pi;
double magic = Math.sin(radLat);
magic = 1 - ee * magic * magic;
double sqrtMagic = Math.sqrt(magic);
dLat = (dLat * 180.0) / ((a * (1 - ee)) / (magic * sqrtMagic) * pi);
dLon = (dLon * 180.0) / (a / sqrtMagic * Math.cos(radLat) * pi);
double mgLat = lat + dLat;
double mgLon = lon + dLon;
return new double[]{mgLat, mgLon};
}

/**
* * 火星坐标系 (GCJ-02) to 84 * * @param lon * @param lat * @return
* */
public static double[] gcj02_To_Gps84(double lat, double lon) {
double[] gps = transform(lat, lon);
double lontitude = lon * 2 - gps[1];
double latitude = lat * 2 - gps[0];
return new double[]{latitude, lontitude};
}
/**
* 火星坐标系 (GCJ-02) 与百度坐标系 (BD-09) 的转换算法 将 GCJ-02 坐标转换成 BD-09 坐标
*
* @param lat
* @param lon
*/
public static double[] gcj02_To_Bd09(double lat, double lon) {
double x = lon, y = lat;
double z = Math.sqrt(x * x + y * y) + 0.00002 * Math.sin(y * x_pi);
double theta = Math.atan2(y, x) + 0.000003 * Math.cos(x * x_pi);
double tempLon = z * Math.cos(theta) + 0.0065;
double tempLat = z * Math.sin(theta) + 0.006;
double[] gps = {tempLat,tempLon};
return gps;
}

/**
* * 火星坐标系 (GCJ-02) 与百度坐标系 (BD-09) 的转换算法 * * 将 BD-09 坐标转换成GCJ-02 坐标 * * @param
* bd_lat * @param bd_lon * @return
*/
public static double[] bd09_To_Gcj02(double lat, double lon) {
double x = lon - 0.0065, y = lat - 0.006;
double z = Math.sqrt(x * x + y * y) - 0.00002 * Math.sin(y * x_pi);
double theta = Math.atan2(y, x) - 0.000003 * Math.cos(x * x_pi);
double tempLon = z * Math.cos(theta);
double tempLat = z * Math.sin(theta);
double[] gps = {tempLat,tempLon};
return gps;
}

/**将gps84转为bd09
* @param lat
* @param lon
* @return
*/
public static double[] gps84_To_bd09(double lat,double lon){
double[] gcj02 = gps84_To_Gcj02(lat,lon);
double[] bd09 = gcj02_To_Bd09(gcj02[0],gcj02[1]);
return bd09;
}
public static double[] bd09_To_gps84(double lat,double lon){
double[] gcj02 = bd09_To_Gcj02(lat, lon);
double[] gps84 = gcj02_To_Gps84(gcj02[0], gcj02[1]);
//保留小数点后六位
gps84[0] = retain6(gps84[0]);
gps84[1] = retain6(gps84[1]);
return gps84;
}

/**保留小数点后六位
* @param num
* @return
*/
private static double retain6(double num){
String result = String .format("%.6f", num);
return Double.valueOf(result);
}

}

3 业务编程

3.1 从设备读取GPS数据

private void ReadGpsData()
{
try
{
bool IsConnected = false;
while (!IsConnected)
{
//获取当前串行端口名称数组
var availableSerialPorts = System.IO.Ports.SerialPort.GetPortNames().OrderBy(s => s);

//初始化 类的新实例，使用第一个端口名称和4800波特率进行初始化
var portName = new System.IO.Ports.SerialPort(availableSerialPorts.First().ToString(), int.Parse("4800"));

while (!IsConnected)
{
if (portName == null)
{
IsConnected = false;
break;
}
else
{
IsConnected = true;
break;
}
}
//NMEA 获取设备
var device = new NmeaParser.SerialPortDevice(portName);
currentDevice = device;
currentDevice.MessageReceived += device_MessageReceived;

//打开连接
var _ = currentDevice.OpenAsync();

Console.WriteLine(_);
Console.WriteLine(string.Format("SerialPortDevice( port={0}, baud={1} )",
((NmeaParser.SerialPortDevice)device).Port.PortName,
((NmeaParser.SerialPortDevice)device).Port.BaudRate));
break;
}
}
catch
{
MessageBox.Show("串口未连接,请检查 Gps 串口", "ERROR");
}
}

3.2 接收 GPS 数据并进行  WGS－84原始坐标系——>GCJ－02坐标系转换

public static double pi = 3.1415926535897932384626;
public static double x_pi = 3.14159265358979324 * 3000.0 / 180.0;
public static double a = 6378245.0;
public static double ee = 0.00669342162296594323;        

private void device_MessageReceived(object sender, NmeaParser.NmeaMessageReceivedEventArgs args)
{

string gpsTime = "";
string latitudeWGS = "";  // 纬度
string longitudeWGS = ""; // 经度
if (args.Message is NmeaParser.Nmea.Gps.Gprmc)
{
string[] result = args.Message.ToString().Split(',');

//判断 传来的数据是否有效。
if (result[2] == "A")
{
string _parsePattern = "ddMMyy hhmmss.ff zzz";
string _date = result[9] + " " + result[1] + " +0000";
DateTimeOffset dto = DateTimeOffset.ParseExact(_date, _parsePattern, CultureInfo.InvariantCulture);
gpsTime = dto.AddHours(8).ToString("yyyy-MM-dd HH:mm:ss", CultureInfo.CreateSpecificCulture("zh-cn"));

latitudeWGS = result[3] + result[4];
longitudeWGS = result[5] + result[6];
//latitudeWGS = "3032.15568N"
//longitudeWGS = "11420.93903E"
string NewlatitudeWGS = latitudeWGS.Remove(10);
string NewlongitudeWGS = longitudeWGS.Remove(11);

double lat = Convert.ToDouble(NewlatitudeWGS);
double lon = Convert.ToDouble(NewlongitudeWGS);

double[] latlon = new double[2];
latlon = gps84_To_Gcj02(lat, lon);

//不带N和E
string Newlatitude = Convert.ToString(latlon[0]);
string Newlongitude = Convert.ToString(latlon[1]);
//加上 N和E
string latitude= Newlatitude.Insert(Newlatitude.Length, "N");
string longitude = Newlongitude.Insert(Newlongitude.Length, "E");
}
}
}
#endregion
public static double[] gps84_To_Gcj02(double lat, double lon)
{
if (outOfChina(lat, lon))
{
return new double[] { lat, lon };
}
double dLat = transformLat(lon - 105.0, lat - 35.0);
double dLon = transformLon(lon - 105.0, lat - 35.0);
double radLat = lat / 180.0 * pi;
double magic = Math.Sin(radLat);
magic = 1 - ee * magic * magic;
double sqrtMagic = Math.Sqrt(magic);
dLat = (dLat * 180.0) / ((a * (1 - ee)) / (magic * sqrtMagic) * pi);
dLon = (dLon * 180.0) / (a / sqrtMagic * Math.Cos(radLat) * pi);
double mgLat = lat + dLat;
double mgLon = lon + dLon;
return new double[] { mgLat, mgLon };
}
public static Boolean outOfChina(double lat, double lon)
{
if (lon < 72.004 || lon > 137.8347)
return true;
if (lat < 0.8293 || lat > 55.8271)
return true;
return false;
}
public static double transformLat(double x, double y)
{
double ret = -100.0 + 2.0 * x + 3.0 * y + 0.2 * y * y + 0.1 * x * y
+ 0.2 * Math.Sqrt(Math.Abs(x));
ret += (20.0 * Math.Sin(6.0 * x * pi) + 20.0 * Math.Sin(2.0 * x * pi)) * 2.0 / 3.0;
ret += (20.0 * Math.Sin(y * pi) + 40.0 * Math.Sin(y / 3.0 * pi)) * 2.0 / 3.0;
ret += (160.0 * Math.Sin(y / 12.0 * pi) + 320 * Math.Sin(y * pi / 30.0)) * 2.0 / 3.0;
return ret;
}

public static double transformLon(double x, double y)
{
double ret = 300.0 + x + 2.0 * y + 0.1 * x * x + 0.1 * x * y + 0.1
* Math.Sqrt(Math.Abs(x));
ret += (20.0 * Math.Sin(6.0 * x * pi) + 20.0 * Math.Sin(2.0 * x * pi)) * 2.0 / 3.0;
ret += (20.0 * Math.Sin(x * pi) + 40.0 * Math.Sin(x / 3.0 * pi)) * 2.0 / 3.0;
ret += (150.0 * Math.Sin(x / 12.0 * pi) + 300.0 * Math.Sin(x / 30.0
* pi)) * 2.0 / 3.0;
return ret;
}

至此，GPS数据从读取到转换过程已经成功。