WM下的GPS开发

  内置GPS： 对于通用的WM设备，我们是通过串口Com9来获得内置GPS的信息的，而一般我们打开的比特率使用的是4800

  gPort.OpenPort(“com9”, 4800)

打开端口之后，一般我们会启用新线程进行读数据

 

void ReadThreadFun() 
        { 
            byte[] buf = new byte[512];//端口缓存大小为512 
            int readLength = 0; 
            while (_isWorking) 
            { 
                readLength = gPort.ReadPort(buf.Length, buf); 
                lastReport += System.Text.Encoding.ASCII.GetString(buf, 0, readLength); 
                    try 
                    { 
                        string[] reports = lastReport.Split(new char[] { '\n' }); 

                        if ((reports[reports.Length - 1].Length > 0) && (reports[reports.Length - 1][reports[reports.Length - 1].Length - 1] != '\r')) 
                            lastReport = reports[reports.Length - 1]; 
                        else 
                            lastReport = ""; 
                        for (int i = 0; i < reports.Length; i++) 
                        {

                         if (GetGpsInfo(reports[i])) 
                           { 
                           //记录GPS的各种信息 
                        } 
                    } 
                    catch (Exception err) 
                    { 
                    } 
                } 
            } 
        }

根据从端口读出的帧数据，我们需要根据协议NMEA0183来解析出GPS所包含的信息

 

public bool GetGpsInfo(string scr) 
        { 
            if (scr.Length < 1) 
                return false; 
            bool ret = false; 

            if (scr.StartsWith("$GPGGA")) 
                ret = GetAltitudeFromGGA(scr); 
            else if (scr.StartsWith("$GPRMC")) 
                ret = GetGpsInfoFromRMC(scr); 

            if ((this.latitude <= 90 && this.latitude >= -90) && 
                (this.longitude <= 360 && this.longitude >= -360)) 
                return ret; 
            else 
                return false; 
        }

 

根据NMEA0183协议的规定，以“$”开始，主要语句有GPGGA，GPVTG，GPRMC等

他们分别是1、 GPS DOP and Active Satellites（GSA）当前卫星信息

               2、 GPS Satellites in View（GSV）可见卫星信息

 

               3、Global Positioning System Fix Data（GGA）GPS定位信息

  private bool GetAltitudeFromGGA(string scr) 
        { 
            float altitude = -1000, geoideAltitude = -1000; 
            string[] fields; 
            bool paramChanged = false; 

            fields = scr.Split(','); 
            if (fields.GetLength(0) < 15) 
                return false; 
            // 获取altitude 
            if (fields[9].Length > 2) 
            { 
                if (System.Text.RegularExpressions.Regex.Match(fields[9], @"^[0-9]+[.]?([\d]+)?").Value == fields[9]) 
                { 
                    altitude = Convert.ToSingle(fields[9]); 
                    if (altitude != this.altitude && altitude != -1000) 
                    { 
                        this.altitude = altitude; 
                        paramChanged = true; 
                    } 
                } 
            } 
            // 获取geoideAltitude 
            if (fields[11].Length > 2) 
            { 
                if (System.Text.RegularExpressions.Regex.Match(fields[11], @"^[0-9]+[.]?([\d]+)?").Value == fields[11]) 
                { 
                    geoideAltitude = Convert.ToSingle(fields[11]); 
                    if (geoideAltitude != this.geoideAltitude && geoideAltitude != -1000) 
                    { 
                        this.geoideAltitude = geoideAltitude; 
                        paramChanged = true; 
                    } 
                } 
            } 
            //高度信息作为辅助信息，不单独报告，只有当经纬度这样的主信息发生变化的时候跟随主信息一起上报 

            return false;// paramChanged; 
        }

               

                4、Recommended Minimum Specific GPS/TRANSIT Data（RMC）推荐定位信息

               

private bool GetGpsInfoFromRMC(string scr) 
        { 
            int latiDegree = 400, longiDegree = 400; 
            float latiMinute = 400, longiMinute = 400, speedTemp = 0, directionTemp = this.direction; 
            char statusTemp = (char)0x0; 
            float latitudeTemp = 400, longitudeTemp = 400; 
            bool paramChanged = false; 

            string[] fields = scr.Split(','); 

            if (fields.GetLength(0) < 12) 
                return false; 
            // 状态 

            if (fields[2].Length == 1) 
            { 
                statusTemp = Convert.ToChar(fields[2]); 
            } 
            // Lati 
            if (fields[3].Length > 5) 
            { 
                if (System.Text.RegularExpressions.Regex.Match(fields[3], @"^[0-9]+[.]?([\d]+)?").Value == fields[3]) 
                { 
                    latiDegree = Convert.ToInt32(fields[3].Substring(0, 2), 10); 
                    latiMinute = Convert.ToSingle(fields[3].Substring(2, fields[3].Length - 2)); 
                    paramChanged = true; 
                } 
            } 
            // NSHemisphere 
            if (fields[4].Length == 1) 
            { 
                //'s' 'S' 
                if (string.Equals(fields[4], "S", StringComparison.CurrentCultureIgnoreCase)) 
                { 
                    latitudeTemp = -latitudeTemp; 
                } 
            } 
            // long 
            if (fields[5].Length > 5) 
            { 
                if (System.Text.RegularExpressions.Regex.Match(fields[5], @"^[0-9]+[.]?([\d]+)?").Value == fields[5]) 
                { 
                    longiDegree = Convert.ToInt32(fields[5].Substring(0, 3), 10); 
                    longiMinute = Convert.ToSingle(fields[5].Substring(3, fields[5].Length - 3)); 
                    paramChanged = true; 
                } 
            } 
            // EWHemisphere 
            if (fields[6].Length == 1) 
            { 
                //'w' 'W' 
                if (string.Equals(fields[6], "W", StringComparison.CurrentCultureIgnoreCase)) 
                { 
                    longitudeTemp = -longitudeTemp; 
                } 
            } 
            // speed 
            if (fields[7].Length > 2) 
            { 
                if (System.Text.RegularExpressions.Regex.Match(fields[7], @"^[0-9]+[.]?([\d]+)?").Value == fields[7]) 
                { 
                    speedTemp = (float)(Convert.ToSingle(fields[7]) * 1.852); 
                    paramChanged = true; 
                } 
            } 
            // direction 
            if (fields[8].Length > 2) 
            { 
                if (System.Text.RegularExpressions.Regex.Match(fields[8], @"^[0-9]+[.]?([\d]+)?").Value == fields[8]) 
                { 
                    directionTemp = Convert.ToSingle(fields[8]); 
                    paramChanged = true; 
                } 
            } 
            if ((latiDegree != 400) && (latiMinute != (float)400.0)) 
            { 
                latitudeTemp = (float)(latiDegree + latiMinute / 60.0); 
            } 
            if ((longiDegree != 400) && (longiMinute != (float)400.0)) 
            { 
                longitudeTemp = (float)(longiDegree + longiMinute / 60.0); 
            } 
            if (paramChanged) 
            { 
                if ((this.latitude == latitudeTemp) && 
                    (this.longitude == longitudeTemp) && 
                    (this.speed == speedTemp) && 
                    (this.direction == directionTemp) && 
                    (this.status == statusTemp)) 
                    return false; 
                else 
                { 
                    this.latitude = latitudeTemp; 
                    this.longitude = longitudeTemp; 
                    this.direction = directionTemp; 
                    this.speed = speedTemp; 
                    this.status = statusTemp; 
                    return true; 
                } 
            } 
            else 
                return false; 
        }

 

                  5、 Track Made Good and Ground Speed（VTG）地面速度信息