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;
}
