10分鍾開發 GPS 應用,了解一下

1 前言

在導師公司實習了半個月，參加的是尾氣遙測項目，我的任務是開發GPS 的相關事情，從零到有的開發出了 GPS 的 Winform 應用，在這里記錄一下開發過程和簡要的描述一下將 GPS 數據提取轉換的過程。 

2 前期准備

2.1 GPS相關軟硬件准備

VS2017 、UB373設備一枚（WGS－84原始坐標系）、安裝驅動、VS2017 Nuget 安裝 SharpGIS.NmeaParser 1.10.0 版本程序包 。

2.2 GPS相關知識儲備

2.2.1 三種類型的地圖坐標系了解一下

• WGS－84原始坐標系，一般用國際GPS紀錄儀記錄下來的經緯度，通過GPS定位拿到的原始經緯度，Google和高德地圖定位的的經緯度（國外）都是基於WGS－84坐標系的；但是在國內是不允許直接用WGS84坐標系標注的，必須經過加密后才能使用；

• GCJ－02坐標系，又名“火星坐標系”，是我國國測局獨創的坐標體系，由WGS－84加密而成，在國內，必須至少使用GCJ－02坐標系，或者使用在GCJ－02加密后再進行加密的坐標系，如百度坐標系。高德和Google在國內都是使用GCJ－02坐標系，可以說，GCJ－02是國內最廣泛使用的坐標系；

• 百度坐標系:bd-09，百度坐標系是在GCJ－02坐標系的基礎上再次加密偏移后形成的坐標系，只適用於百度地圖。(目前百度API提供了從其它坐標系轉換為百度坐標系的API，但卻沒有從百度坐標系轉為其他坐標系的API)

2.2.2 GPS 數據位置發生偏移

由於坐標系之間不兼容，如在百度地圖上定位的經緯度拿到高德地圖上直接描點就肯定會發生偏移；只考慮國內的情況，高德地圖和Google地圖是可以不經過轉換也能夠准確顯示的（在國內用的都是GCJ－02坐標系）；下面是收錄了網上的WGS－84，GCJ－02，百度坐標系(bd-09)之間的相互轉換的方法，經測試，是轉換后相對准確可用的：

轉換代碼：

/**火星坐標系 (GCJ-02) 與百度坐標系 (BD-09) 的互轉
 * 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 火星坐標系 (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};
    }
 
    /**
     * * 火星坐標系 (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};
    }
    /**
     * 火星坐標系 (GCJ-02) 與百度坐標系 (BD-09) 的轉換算法 將 GCJ-02 坐標轉換成 BD-09 坐標
     *
     * @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;
    }
 
    /**
     * * 火星坐標系 (GCJ-02) 與百度坐標系 (BD-09) 的轉換算法 * * 將 BD-09 坐標轉換成GCJ-02 坐標 * * @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;
    }
 
    /**將gps84轉為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]);
        //保留小數點后六位
        gps84[0] = retain6(gps84[0]);
        gps84[1] = retain6(gps84[1]);
        return gps84;
    }
 
    /**保留小數點后六位
     * @param num
     * @return
     */
    private static double retain6(double num){
        String result = String .format("%.6f", num);
        return Double.valueOf(result);
    }
 
}

3 業務編程

3.1 從設備讀取GPS數據

        private void ReadGpsData()
        {
           try
            {
                bool IsConnected = false;
                while (!IsConnected)
                {
                    //獲取當前串行端口名稱數組
                    var availableSerialPorts = System.IO.Ports.SerialPort.GetPortNames().OrderBy(s => s);

                    //初始化 類的新實例，使用第一個端口名稱和4800波特率進行初始化
                    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 獲取設備
                    var device = new NmeaParser.SerialPortDevice(portName);
                    currentDevice = device;
                    currentDevice.MessageReceived += device_MessageReceived;

                    //打開連接
                    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("串口未連接,請檢查 Gps 串口", "ERROR");
            }
        }

3.2 接收 GPS 數據並進行  WGS－84原始坐標系——>GCJ－02坐標系轉換

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 = "";  // 緯度
            string longitudeWGS = ""; // 經度
            if (args.Message is NmeaParser.Nmea.Gps.Gprmc)
            {
                string[] result = args.Message.ToString().Split(',');
               
                //判斷 傳來的數據是否有效。
                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);

                    //不帶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數據從讀取到轉換過程已經成功。