public void StartRealTime(GpsRealTimeHandler realtimeCallback)
{
int total = 0;
int maxErrors = 5;
int errors = maxErrors;
bool finished = false;
m_stopRealTime = false;
while (!finished && !m_stopRealTime)
{
GpsRealTimeData pvtData = new GpsRealTimeData(); // will be returned empty if no data
MPacketReceived received = null;
try
{
received = m_linkLayer.ReceivePacket();
if (!received.isGood)
{
m_linkLayer.logError("StartRealTime: bad packet received, count=" + total);
pvtData.comment = "bad data packet from GPS";
realtimeCallback(pvtData);
continue;
}
}
catch (Exception e)
{
m_linkLayer.logError("StartRealTime: " + e.Message + " count=" + total);
//if(received != null)
{
try
{
m_linkLayer.ReOpen();
}
catch (Exception ee)
{
m_linkLayer.logError("while ReOpen(): " + ee.Message);
}
}
pvtData.comment = e.Message.StartsWith("Timeout") ?
"GPS not responding - check cable" : ("error: " + e.Message);
realtimeCallback(pvtData);
continue;
}
//m_linkLayer.log("" + total + " === " + received);
m_linkLayer.log("StartRealTime: good packet received, count=" + total + " " + received);
if (received.header.EndsWith("GGA")) // NMEA GGA expected for location
{
m_linkLayer.log("StartRealTime: " + received.header + " packet received, count=" + total + " content=" + received);
try
{
MPacket pvt = received.fromString();
/*
* $GPGGA,123519,4807.038,N,01131.000,E,1,08,0.9,545.4,M,46.9,M,,*47
*
* Where:
* GGA Global Positioning System Fix Data
* 0 123519 Fix taken at 12:35:19 UTC
* 1 4807.038,N Latitude 48 deg 07.038' N
* 3 01131.000,E Longitude 11 deg 31.000' E
* 5 1 Fix quality: 0 = invalid
* 1 = GPS fix
* 2 = DGPS fix
* 6 = estimated (2.3 feature)
* 6 08 Number of satellites being tracked
* 7 0.9 Horizontal dilution of position
* 8 545.4,M Altitude, Meters, above mean sea level
* 10 46.9,M Height of geoid (mean sea level) above WGS84
* ellipsoid
* 12 (empty field) time in seconds since last DGPS update
* 13 (empty field) DGPS station ID number
* 47 the checksum data, always begins with *
*/
double Lat = pvt.parseLat(1);
double Lng = pvt.parseLng(1);
double Elev = pvt.parseElev(8); // alt above mean sea level
pvtData.location = new GeoCoord(Lng, Lat, Elev);
//m_linkLayer.log("coord=" + pvtData.location);
// time component:
pvtData.time = pvt.parseNmeaTime(0, Project.localToZulu(DateTime.Now)); // UTC
// errors and velocity:
pvtData.posError = 0;
pvtData.posErrorH = 0;
pvtData.posErrorV = 0;
pvtData.fix = 0; // failed integrity check
switch ((string)pvt.fields[5])
{
case "0": // invalid
pvtData.fix = 1; // invalid
break;
case "1": // GPS fix
pvtData.fix = 2; // two dimensional
break;
case "2": // DGPS fix
pvtData.fix = 4; // two dimensional differential
break;
case "6": // estimated
pvtData.fix = 6; // estimated
break;
}
pvtData.velocityEast = 0;
pvtData.velocityNorth = 0;
pvtData.velocityUp = 0;
pvtData.comment = "received " + received.header;
//realtimeCallback(pvtData);
total++;
errors = maxErrors;
}
catch (Exception ee)
{
m_linkLayer.logError("StartRealTime: " + ee.Message);
}
}
else if (received.header.EndsWith("RMC")) // NMEA RMC may come
{
m_linkLayer.log("StartRealTime: " + received.header + " packet received, count=" + total + " content=" + received);
try
{
MPacket pvt = received.fromString();
// $GPRMC,052458.73,V,3334.6441,N,11739.6622,W,00.0,000.0,290103,13,E*4F
/*
* see http://www.gpsinformation.org/dale/nmea.htm for NMEA reference
*
* RMC - NMEA has its own version of essential gps pvt (position, velocity, time) data.
* It is called RMC, The Recommended Minimum, which might look like:
*
* $GPRMC,123519,A,4807.038,N,01131.000,E,022.4,084.4,230394,003.1,W*6A
* $GPRMC,050821.000,A,3334.5551,N,11739.7705,W,0.00,,251006,,,A*67
*
* Where:
* RMC Recommended Minimum sentence C
* 0 123519 Fix taken at 12:35:19 UTC
* 1 A Status A=active or V=Void.
* 2 4807.038,N Latitude 48 deg 07.038' N
* 4 01131.000,E Longitude 11 deg 31.000' E
* 6 022.4 Speed over the ground in knots
* 7 084.4 Track angle in degrees True
* 8 230394 Date - 23rd of March 1994
* 9 003.1,W Magnetic Variation
* 6A The checksum data, always begins with *
*
* Note that, as of the 2.3 release of NMEA, there is a new field in the RMC sentence
* at the end just prior to the checksum. The value of the entry is
* A=autonomous, D=differential, E=estimated, N=Data not valid.
*/
bool status = "A".Equals(pvt.fields[1]);
if (status)
{
double Lat = pvt.parseLat(2);
double Lng = pvt.parseLng(2);
double Elev = 0.0d;
pvtData.location = new GeoCoord(Lng, Lat, Elev);
//m_linkLayer.log("coord=" + pvtData.location);
// time component (only time part):
pvtData.time = pvt.parseNmeaDateTime(0, 8); // UTC
if (!"".Equals(pvt.fields[6]))
{
double knots = Convert.ToDouble(pvt.fields[6]);
pvtData.velocity = knots * Distance.METERS_PER_NAUTICAL_MILE / 3600.0d;
// calculate velocity vector based on track angle:
if (!"".Equals(pvt.fields[7]))
{
double trackAngleRad = Convert.ToDouble(pvt.fields[7]) * Math.PI / 180.0d;
pvtData.velocityNorth = pvtData.velocity * Math.Cos(trackAngleRad);
pvtData.velocityEast = pvtData.velocity * Math.Sin(trackAngleRad);
}
}
pvtData.fix = 2; // assume two-dimensional
pvtData.comment = "received " + received.header;
realtimeCallback(pvtData);
}
total++;
errors = maxErrors;
}
catch (Exception ee)
{
m_linkLayer.logError("StartRealTime: " + ee.Message);
}
}
else if (received.header.EndsWith("GLL")) // NMEA GLL may come
{
m_linkLayer.log("StartRealTime: GLL packet received, count=" + total + " content=" + received);
try
{
MPacket pvt = received.fromString();
// $GPGLL,3334.6464,N,11739.6583,W,052707.129,A*29
/*
* see http://www.gpsinformation.org/dale/nmea.htm for NMEA reference
*
* GLL - Geographic Latitude and Longitude is a holdover from Loran data and some old units
* may not send the time and data valid information if they are emulating Loran data.
* If a gps is emulating Loran data they may use the LC Loran prefix instead of GP.
*
* $GPGLL,4916.45,N,12311.12,W,225444,A,*31
*
* Where:
* GLL Geographic position, Latitude and Longitude
* 0 4916.46,N Latitude 49 deg. 16.45 min. North
* 2 12311.12,W Longitude 123 deg. 11.12 min. West
* 4 225444 Fix taken at 22:54:44 UTC
* 5 A Data valid or V (void)
* 31 checksum data
*
*/
bool status = "A".Equals(pvt.fields[5]);
if (status)
{
double Lat = pvt.parseLat(0);
double Lng = pvt.parseLng(0);
double Elev = 0.0d;
pvtData.location = new GeoCoord(Lng, Lat, Elev);
//m_linkLayer.log("coord=" + pvtData.location);
// time component (only time part):
pvtData.time = pvt.parseNmeaTime(4, Project.localToZulu(DateTime.Now)); // UTC
pvtData.fix = 2; // assume two-dimensional
pvtData.comment = "received " + received.header;
//realtimeCallback(pvtData);
}
total++;
errors = maxErrors;
}
catch (Exception ee)
{
m_linkLayer.logError("StartRealTime: " + ee.Message);
}
}
else if (received.header.EndsWith("GSV")) // NMEA GSV may come for satellite reception status
{
m_linkLayer.log("StartRealTime: GSV packet received, count=" + total + " content=" + received);
/*
* see http://www.gpsinformation.org/dale/nmea.htm for NMEA reference
*
* $GPGSV,3,1,08,14,69,204,,15,57,105,36,18,45,047,36,03,42,263,36*71
* $GPGSV,2,1,08,01,40,083,46,02,17,308,41,12,07,344,39,14,22,228,45*75
*
* Where:
* GSV Satellites in view
* 0 2 Number of sentences for full data
* 1 1 sentence 1 of 2
* 2 08 Number of satellites in view
* for up to 4 satellites per sentence {
* 3 01 Satellite PRN number
* 4 40 Elevation, degrees
* 5 083 Azimuth, degrees
* 6 46 Signal strength - higher is better
* }
* 75 the checksum data, always begins with *
*/
//MPacket pvt = received.fromString();
//pvtData.comment = "received";
//realtimeCallback(pvtData);
total++;
errors = maxErrors;
}
else if (received.header.EndsWith("VTG")) // NMEA GSA may come
{
m_linkLayer.log("StartRealTime: GPVTG packet received, count=" + total + " content=" + received);
// $GPVTG,309.62,T,,M,0.13,N,0.2,K*6E
/*
* VTG - Course Over Ground and Ground Speed
*
* Name Example Units Description
* Message ID $GPVTG VTG protocol header
* Course 309.62 degrees Measured heading
* Reference T True
* Course degrees Measured heading
* Reference M Magnetic
* Speed 0.13 knots Measured horizontal speed
* Units N Knots
* Speed 0.2 Km/hr Measured horizontal speed
* Units K Kilometers per hour
*/
}
else if (received.header.EndsWith("GSA")) // NMEA GSA may come
{
m_linkLayer.log("StartRealTime: GPGSA packet received, count=" + total + " content=" + received);
// $GPGSA,A,2,15,18,14,31,,,,,,,,,05.6,05.6,*17
/*
* see http://www.gpsinformation.org/dale/nmea.htm for NMEA reference
*
* GSA - GPS DOP and active satellites. This sentence provides details on the nature of the
* fix. It includes the numbers of the satellites being used in the current solution and
* the DOP. DOP (dilution of precision) is an indication of the effect of satellite geometry
* on the accuracy of the fix. It is a unitless number where smaller is better. For 3D fixes
* using 4 satellites a 1.0 would be considered to be a perfect number. For overdetermined
* solutions it is possible to see numbers below 1.0. There are differences in the way the
* PRN's are presented which can effect the ability of some programs to display this data.
* For example, in the example shown below there are 5 satellites in the solution and
* the null fields are scattered indicating that the almanac would show satellites in
* the null positions that are not being used as part of this solution. Other receivers
* might output all of the satellites used at the beginning of the sentence with the
* null field all stacked up at the end. This difference accounts for some satellite
* display programs not always being able to display the satellites being tracked.
*
* $GPGSA,A,3,04,05,,09,12,,,24,,,,,2.5,1.3,2.1*39
*
* Where:
* GSA Satellite status
* A Auto selection of 2D or 3D fix (M = manual)
* 3 3D fix - other values include: 1 = no fix
* 2 = 2D fix
* 04,05... PRNs of satellites used for fix (space for 12)
* 2.5 PDOP (dilution of precision)
* 1.3 Horizontal dilution of precision (HDOP)
* 2.1 Vertical dilution of precision (VDOP)
* 39 the checksum data, always begins with *
*
*/
}
else
{
m_linkLayer.log("StartRealTime: good other (unrecognized) packet received, count=" + total + " content=" + received);
}
} // end while()
m_linkLayer.log("StartRealTime: finished receiving fixes count=" + total);
}
public override void StartRealTime(GpsRealTimeHandler realtimeCallback)
{
m_appLayer.StartRealTime(realtimeCallback);
}
public override void StartRealTime(GpsRealTimeHandler realtimeCallback)
{
m_appLayer.StartRealTime(realtimeCallback);
}
public abstract void StartRealTime(GpsRealTimeHandler realtimeCallback);
private void simulateStartRealTime(GpsRealTimeHandler realtimeCallback)
{
int toWait = 3;
int toCount = 10;
double degIncr = 360.0d / (toCount * 4);
double degree = 0.0d;
int count = toCount;
GeoCoord location = new GeoCoord(CameraManager.This.Location.Lng, CameraManager.This.Location.Lat);
while (count-- > 0)
{
GpsRealTimeData rtData = new GpsRealTimeData();
rtData.location = location;
rtData.fix = 2;
rtData.time = DateTime.Now;
rtData.velocity = 10.0d;
rtData.velocityEast = 5.0d * Math.Sin(degree * Math.PI / 180.0d);
rtData.velocityNorth = 5.0d * Math.Cos(degree * Math.PI / 180.0d);
degree += degIncr;
realtimeCallback(rtData);
location.Lat += 0.0005d;
location.Lng += 0.0005d;
Thread.Sleep(toWait);
}
count = toCount;
while (count-- > 0)
{
GpsRealTimeData rtData = new GpsRealTimeData();
rtData.location = location;
rtData.fix = 2;
rtData.time = DateTime.Now;
rtData.velocity = 10.0d;
rtData.velocityEast = 5.0d * Math.Sin(degree * Math.PI / 180.0d);
rtData.velocityNorth = 5.0d * Math.Cos(degree * Math.PI / 180.0d);
degree += degIncr;
realtimeCallback(rtData);
location.Lat -= 0.0005d;
location.Lng += 0.0005d;
Thread.Sleep(toWait);
}
count = toCount;
while (count-- > 0)
{
GpsRealTimeData rtData = new GpsRealTimeData();
rtData.location = location;
rtData.fix = 2;
rtData.time = DateTime.Now;
rtData.velocity = 10.0d;
rtData.velocityEast = 5.0d * Math.Sin(degree * Math.PI / 180.0d);
rtData.velocityNorth = 5.0d * Math.Cos(degree * Math.PI / 180.0d);
degree += degIncr;
realtimeCallback(rtData);
location.Lat -= 0.0005d;
location.Lng -= 0.0005d;
Thread.Sleep(toWait);
}
count = toCount;
while (count-- > 0)
{
GpsRealTimeData rtData = new GpsRealTimeData();
rtData.location = location;
rtData.fix = 2;
rtData.time = DateTime.Now;
rtData.velocity = 10.0d;
rtData.velocityEast = 5.0d * Math.Sin(degree * Math.PI / 180.0d);
rtData.velocityNorth = 5.0d * Math.Cos(degree * Math.PI / 180.0d);
degree += degIncr;
realtimeCallback(rtData);
location.Lat += 0.0005d;
location.Lng -= 0.0005d;
Thread.Sleep(toWait);
}
}
public void StartRealTime(GpsRealTimeHandler realtimeCallback)
{
m_linkLayer.getPvtTransferProtocol().StartRealTime(realtimeCallback);
}
public void StartRealTime(GpsRealTimeHandler realtimeCallback)
{
int total = 0;
int maxErrors = 5;
int errors = maxErrors;
bool finished = false;
m_stopRealTime = false;
while(!finished && !m_stopRealTime)
{
GpsRealTimeData pvtData = new GpsRealTimeData(); // will be returned empty if no data
MPacketReceived received = null;
try
{
received = m_linkLayer.ReceivePacket();
if(!received.isGood)
{
m_linkLayer.logError("StartRealTime: bad packet received, count=" + total);
pvtData.comment = "bad data packet from GPS";
realtimeCallback(pvtData);
continue;
}
}
catch(Exception e)
{
m_linkLayer.logError("StartRealTime: " + e.Message + " count=" + total);
//if(received != null)
{
try
{
m_linkLayer.ReOpen();
}
catch (Exception ee)
{
m_linkLayer.logError("while ReOpen(): " + ee.Message);
}
}
pvtData.comment = e.Message.StartsWith("Timeout") ?
"GPS not responding - check cable" : ("error: " + e.Message);
realtimeCallback(pvtData);
continue;
}
//m_linkLayer.log("" + total + " === " + received);
m_linkLayer.log("StartRealTime: good packet received, count=" + total + " " + received);
if(received.header.EndsWith("GGA")) // NMEA GGA expected for location
{
m_linkLayer.log("StartRealTime: " + received.header + " packet received, count=" + total + " content=" + received);
try
{
MPacket pvt = received.fromString();
/*
$GPGGA,123519,4807.038,N,01131.000,E,1,08,0.9,545.4,M,46.9,M,,*47
Where:
GGA Global Positioning System Fix Data
0 123519 Fix taken at 12:35:19 UTC
1 4807.038,N Latitude 48 deg 07.038' N
3 01131.000,E Longitude 11 deg 31.000' E
5 1 Fix quality: 0 = invalid
1 = GPS fix
2 = DGPS fix
6 = estimated (2.3 feature)
6 08 Number of satellites being tracked
7 0.9 Horizontal dilution of position
8 545.4,M Altitude, Meters, above mean sea level
10 46.9,M Height of geoid (mean sea level) above WGS84
ellipsoid
12 (empty field) time in seconds since last DGPS update
13 (empty field) DGPS station ID number
*47 the checksum data, always begins with *
*/
double Lat = pvt.parseLat(1);
double Lng = pvt.parseLng(1);
double Elev = pvt.parseElev(8); // alt above mean sea level
pvtData.location = new GeoCoord(Lng, Lat, Elev);
//m_linkLayer.log("coord=" + pvtData.location);
// time component:
pvtData.time = pvt.parseNmeaTime(0, Project.localToZulu(DateTime.Now)); // UTC
// errors and velocity:
pvtData.posError = 0;
pvtData.posErrorH = 0;
pvtData.posErrorV = 0;
pvtData.fix = 0; // failed integrity check
switch((string)pvt.fields[5])
{
case "0": // invalid
pvtData.fix = 1; // invalid
break;
case "1": // GPS fix
pvtData.fix = 2; // two dimensional
break;
case "2": // DGPS fix
pvtData.fix = 4; // two dimensional differential
break;
case "6": // estimated
pvtData.fix = 6; // estimated
break;
}
pvtData.velocityEast = 0;
pvtData.velocityNorth = 0;
pvtData.velocityUp = 0;
pvtData.comment = "received " + received.header;
//realtimeCallback(pvtData);
total++;
errors = maxErrors;
}
catch(Exception ee)
{
m_linkLayer.logError("StartRealTime: " + ee.Message);
}
}
else if(received.header.EndsWith("RMC")) // NMEA RMC may come
{
m_linkLayer.log("StartRealTime: " + received.header + " packet received, count=" + total + " content=" + received);
try
{
MPacket pvt = received.fromString();
// $GPRMC,052458.73,V,3334.6441,N,11739.6622,W,00.0,000.0,290103,13,E*4F
/*
* see http://www.gpsinformation.org/dale/nmea.htm for NMEA reference
*
RMC - NMEA has its own version of essential gps pvt (position, velocity, time) data.
It is called RMC, The Recommended Minimum, which might look like:
$GPRMC,123519,A,4807.038,N,01131.000,E,022.4,084.4,230394,003.1,W*6A
$GPRMC,050821.000,A,3334.5551,N,11739.7705,W,0.00,,251006,,,A*67
Where:
RMC Recommended Minimum sentence C
0 123519 Fix taken at 12:35:19 UTC
1 A Status A=active or V=Void.
2 4807.038,N Latitude 48 deg 07.038' N
4 01131.000,E Longitude 11 deg 31.000' E
6 022.4 Speed over the ground in knots
7 084.4 Track angle in degrees True
8 230394 Date - 23rd of March 1994
9 003.1,W Magnetic Variation
*6A The checksum data, always begins with *
Note that, as of the 2.3 release of NMEA, there is a new field in the RMC sentence
at the end just prior to the checksum. The value of the entry is
A=autonomous, D=differential, E=estimated, N=Data not valid.
*/
bool status = "A".Equals(pvt.fields[1]);
if(status)
{
double Lat = pvt.parseLat(2);
double Lng = pvt.parseLng(2);
double Elev = 0.0d;
pvtData.location = new GeoCoord(Lng, Lat, Elev);
//m_linkLayer.log("coord=" + pvtData.location);
// time component (only time part):
pvtData.time = pvt.parseNmeaDateTime(0, 8); // UTC
if(!"".Equals(pvt.fields[6]))
{
double knots = Convert.ToDouble(pvt.fields[6]);
pvtData.velocity = knots * Distance.METERS_PER_NAUTICAL_MILE / 3600.0d;
// calculate velocity vector based on track angle:
if(!"".Equals(pvt.fields[7]))
{
double trackAngleRad = Convert.ToDouble(pvt.fields[7]) * Math.PI / 180.0d;
pvtData.velocityNorth = pvtData.velocity * Math.Cos(trackAngleRad);
pvtData.velocityEast = pvtData.velocity * Math.Sin(trackAngleRad);
}
}
pvtData.fix = 2; // assume two-dimensional
pvtData.comment = "received " + received.header;
realtimeCallback(pvtData);
}
total++;
errors = maxErrors;
}
catch(Exception ee)
{
m_linkLayer.logError("StartRealTime: " + ee.Message);
}
}
else if(received.header.EndsWith("GLL")) // NMEA GLL may come
{
m_linkLayer.log("StartRealTime: GLL packet received, count=" + total + " content=" + received);
try
{
MPacket pvt = received.fromString();
// $GPGLL,3334.6464,N,11739.6583,W,052707.129,A*29
/*
* see http://www.gpsinformation.org/dale/nmea.htm for NMEA reference
*
GLL - Geographic Latitude and Longitude is a holdover from Loran data and some old units
may not send the time and data valid information if they are emulating Loran data.
If a gps is emulating Loran data they may use the LC Loran prefix instead of GP.
$GPGLL,4916.45,N,12311.12,W,225444,A,*31
Where:
GLL Geographic position, Latitude and Longitude
0 4916.46,N Latitude 49 deg. 16.45 min. North
2 12311.12,W Longitude 123 deg. 11.12 min. West
4 225444 Fix taken at 22:54:44 UTC
5 A Data valid or V (void)
*31 checksum data
*/
bool status = "A".Equals(pvt.fields[5]);
if(status)
{
double Lat = pvt.parseLat(0);
double Lng = pvt.parseLng(0);
double Elev = 0.0d;
pvtData.location = new GeoCoord(Lng, Lat, Elev);
//m_linkLayer.log("coord=" + pvtData.location);
// time component (only time part):
pvtData.time = pvt.parseNmeaTime(4, Project.localToZulu(DateTime.Now)); // UTC
pvtData.fix = 2; // assume two-dimensional
pvtData.comment = "received " + received.header;
//realtimeCallback(pvtData);
}
total++;
errors = maxErrors;
}
catch(Exception ee)
{
m_linkLayer.logError("StartRealTime: " + ee.Message);
}
}
else if(received.header.EndsWith("GSV")) // NMEA GSV may come for satellite reception status
{
m_linkLayer.log("StartRealTime: GSV packet received, count=" + total + " content=" + received);
/*
* see http://www.gpsinformation.org/dale/nmea.htm for NMEA reference
*
$GPGSV,3,1,08,14,69,204,,15,57,105,36,18,45,047,36,03,42,263,36*71
$GPGSV,2,1,08,01,40,083,46,02,17,308,41,12,07,344,39,14,22,228,45*75
Where:
GSV Satellites in view
0 2 Number of sentences for full data
1 1 sentence 1 of 2
2 08 Number of satellites in view
for up to 4 satellites per sentence {
3 01 Satellite PRN number
4 40 Elevation, degrees
5 083 Azimuth, degrees
6 46 Signal strength - higher is better
}
*75 the checksum data, always begins with *
*/
//MPacket pvt = received.fromString();
//pvtData.comment = "received";
//realtimeCallback(pvtData);
total++;
errors = maxErrors;
}
else if(received.header.EndsWith("VTG")) // NMEA GSA may come
{
m_linkLayer.log("StartRealTime: GPVTG packet received, count=" + total + " content=" + received);
// $GPVTG,309.62,T,,M,0.13,N,0.2,K*6E
/*
VTG - Course Over Ground and Ground Speed
Name Example Units Description
Message ID $GPVTG VTG protocol header
Course 309.62 degrees Measured heading
Reference T True
Course degrees Measured heading
Reference M Magnetic
Speed 0.13 knots Measured horizontal speed
Units N Knots
Speed 0.2 Km/hr Measured horizontal speed
Units K Kilometers per hour
*/
}
else if(received.header.EndsWith("GSA")) // NMEA GSA may come
{
m_linkLayer.log("StartRealTime: GPGSA packet received, count=" + total + " content=" + received);
// $GPGSA,A,2,15,18,14,31,,,,,,,,,05.6,05.6,*17
/*
* see http://www.gpsinformation.org/dale/nmea.htm for NMEA reference
*
GSA - GPS DOP and active satellites. This sentence provides details on the nature of the
fix. It includes the numbers of the satellites being used in the current solution and
the DOP. DOP (dilution of precision) is an indication of the effect of satellite geometry
on the accuracy of the fix. It is a unitless number where smaller is better. For 3D fixes
using 4 satellites a 1.0 would be considered to be a perfect number. For overdetermined
solutions it is possible to see numbers below 1.0. There are differences in the way the
PRN's are presented which can effect the ability of some programs to display this data.
For example, in the example shown below there are 5 satellites in the solution and
the null fields are scattered indicating that the almanac would show satellites in
the null positions that are not being used as part of this solution. Other receivers
might output all of the satellites used at the beginning of the sentence with the
null field all stacked up at the end. This difference accounts for some satellite
display programs not always being able to display the satellites being tracked.
$GPGSA,A,3,04,05,,09,12,,,24,,,,,2.5,1.3,2.1*39
Where:
GSA Satellite status
A Auto selection of 2D or 3D fix (M = manual)
3 3D fix - other values include: 1 = no fix
2 = 2D fix
04,05... PRNs of satellites used for fix (space for 12)
2.5 PDOP (dilution of precision)
1.3 Horizontal dilution of precision (HDOP)
2.1 Vertical dilution of precision (VDOP)
*39 the checksum data, always begins with *
*/
}
else
{
m_linkLayer.log("StartRealTime: good other (unrecognized) packet received, count=" + total + " content=" + received);
}
} // end while()
m_linkLayer.log("StartRealTime: finished receiving fixes count=" + total);
}
public void StartRealTime(GpsRealTimeHandler realtimeCallback)
{
int total = 0;
int maxErrors = 5;
int errors = maxErrors;
bool finished = false;
m_stopRealTime = false;
DateTime lastGPGGA = DateTime.MinValue;
DateTime lastGPRMC = DateTime.MinValue;
double lastGPRMCvelocity = 0.0d;
double lastGPRMCvelocityNorth = 0.0d;
double lastGPRMCvelocityEast = 0.0d;
//m_linkLayer.SetHandshake(Project.gpsMagellanHandshake);
m_linkLayer.SetHandshake(true); // safer with handshake on
m_linkLayer.SendPacket(new MPacketCmd("FIX"));
m_linkLayer.SendPacket(new MPacketCmd("NMEAON"));
while(!finished && !m_stopRealTime)
{
GpsRealTimeData pvtData = new GpsRealTimeData(); // will be returned empty if no data
MPacketReceived received = null;
try
{
received = m_linkLayer.ReceivePacket();
if(!received.isGood)
{
m_linkLayer.logError("StartRealTime: bad packet received, count=" + total);
pvtData.comment = "bad data packet from GPS";
realtimeCallback(pvtData);
continue;
}
}
catch(Exception e)
{
m_linkLayer.logError("StartRealTime exception: " + e.Message + " count=" + total);
//if(received != null)
{
try
{
m_linkLayer.ReOpen();
}
catch (Exception ee)
{
m_linkLayer.logError("while ReOpen(): " + ee.Message);
}
}
pvtData.comment = e.Message.StartsWith("Timeout") ?
"GPS not responding - check cable" : ("error: " + e.Message);
realtimeCallback(pvtData);
continue;
}
m_linkLayer.log("StartRealTime: good packet received, count=" + total + " " + received);
if(received.header.Equals("GPGGA")) // NMEA GGA expected for location (best data packet to hope for from Magellan)
{
try
{
MPacket pvt = received.fromString();
/*
$GPGGA,123519,4807.038,N,01131.000,E,1,08,0.9,545.4,M,46.9,M,,*47
Where:
GGA Global Positioning System Fix Data
0 123519 Fix taken at 12:35:19 UTC
1 4807.038,N Latitude 48 deg 07.038' N
3 01131.000,E Longitude 11 deg 31.000' E
5 1 Fix quality: 0 = invalid
1 = GPS fix
2 = DGPS fix
6 = estimated (2.3 feature)
6 08 Number of satellites being tracked
7 0.9 Horizontal dilution of position
8 545.4,M Altitude, Meters, above mean sea level
10 46.9,M Height of geoid (mean sea level) above WGS84
ellipsoid
12 (empty field) time in seconds since last DGPS update
13 (empty field) DGPS station ID number
*47 the checksum data, always begins with *
*/
double Lat = pvt.parseLat(1);
double Lng = pvt.parseLng(1);
double Elev = pvt.parseElev(8); // alt above mean sea level
pvtData.location = new GeoCoord(Lng, Lat, Elev);
//m_linkLayer.log("coord=" + pvtData.location);
// time component:
pvtData.time = pvt.parseNmeaTime(0, Project.localToZulu(DateTime.Now)); // UTC
// errors and velocity:
pvtData.posErrorH = Convert.ToDouble((string)pvt.fields[7]) * 2.0d; // ad-hoc factor to match device EPE reading
pvtData.posError = pvtData.posErrorH;
pvtData.posErrorV = -1;
pvtData.fix = 0; // failed integrity check
switch((string)pvt.fields[5])
{
case "0": // invalid
pvtData.fix = 1; // invalid
break;
case "1": // GPS fix
pvtData.fix = 2; // two dimensional
break;
case "2": // DGPS fix
pvtData.fix = 5; // two dimensional differential
break;
case "6": // estimated
pvtData.fix = 6; // estimated
break;
}
string msg = "received " + received.header;
// GPGGA is lacking velocity data, mix it in from a recent GPRMC
if(DateTime.Now.Ticks < lastGPRMC.AddSeconds(10.0d).Ticks)
{
msg += "/GPRMC";
pvtData.velocity = lastGPRMCvelocity;
pvtData.velocityNorth = lastGPRMCvelocityNorth;
pvtData.velocityEast = lastGPRMCvelocityEast;
}
else
{
pvtData.velocity = -1.0d;
pvtData.velocityNorth = 0.0d;
pvtData.velocityEast = 0.0d;
}
pvtData.velocityUp = 0.0d;
pvtData.comment = msg;
lastGPGGA = DateTime.Now; // GPGGA is the best we can hope for, don't allow others to be processed if we have this one
realtimeCallback(pvtData);
total++;
errors = maxErrors;
}
catch(Exception ee)
{
m_linkLayer.logError("StartRealTime: " + ee.Message);
}
}
else if(received.header.Equals("GPRMC")) // NMEA GPRMC may come with positioning data
{
m_linkLayer.log("StartRealTime: GPRMC packet received, count=" + total + " content=" + received);
try
{
MPacket pvt = received.fromString();
// $GPRMC,052458.73,V,3334.6441,N,11739.6622,W,00.0,000.0,290103,13,E*4F
/*
* see http://www.gpsinformation.org/dale/nmea.htm for NMEA reference
*
RMC - NMEA has its own version of essential gps pvt (position, velocity, time) data.
It is called RMC, The Recommended Minimum, which might look like:
$GPRMC,123519,A,4807.038,N,01131.000,E,022.4,084.4,230394,003.1,W*6A
Where:
RMC Recommended Minimum sentence C
0 123519 Fix taken at 12:35:19 UTC
1 A Status A=active or V=Void.
2 4807.038,N Latitude 48 deg 07.038' N
4 01131.000,E Longitude 11 deg 31.000' E
6 022.4 Speed over the ground in knots
7 084.4 Track angle in degrees True
8 230394 Date - 23rd of March 1994
9 003.1,W Magnetic Variation
*6A The checksum data, always begins with *
Note that, as of the 2.3 release of NMEA, there is a new field in the RMC sentence
at the end just prior to the checksum. The value of the entry is
A=autonomous, D=differential, E=estimated, N=Data not valid.
*/
bool status = "A".Equals((string)pvt.fields[1]);
if(status)
{
// velocity is used to mix in GPGGA, compute it first:
double knots = Double.Parse((string)pvt.fields[6]);
lastGPRMCvelocity = knots * Distance.METERS_PER_NAUTICAL_MILE / 3600.0d;
// calculate velocity vector based on track angle:
double trackAngleRad = Convert.ToDouble(pvt.fields[7]) * Math.PI / 180.0d;
lastGPRMCvelocityNorth = lastGPRMCvelocity * Math.Cos(trackAngleRad);
lastGPRMCvelocityEast = lastGPRMCvelocity * Math.Sin(trackAngleRad);
lastGPRMC = DateTime.Now;
// GPGGA is the best data we can hope for, don't allow others to be processed if we had a recent GPGGA
if(DateTime.Now.Ticks > lastGPGGA.AddSeconds(10.0d).Ticks)
{
double Lat = pvt.parseLat(2);
double Lng = pvt.parseLng(2);
double Elev = 0.0d;
pvtData.location = new GeoCoord(Lng, Lat, Elev);
//m_linkLayer.log("coord=" + pvtData.location);
// time component (only time part):
pvtData.time = pvt.parseNmeaDateTime(0, 8); // UTC
pvtData.velocity = lastGPRMCvelocity;
pvtData.velocityNorth = lastGPRMCvelocityNorth;
pvtData.velocityEast = lastGPRMCvelocityEast;
pvtData.fix = 2; // assume two-dimensional
pvtData.comment = "received " + received.header;
realtimeCallback(pvtData);
}
}
total++;
errors = maxErrors;
}
catch(Exception ee)
{
m_linkLayer.logError("StartRealTime: " + ee.Message);
}
}
else if(received.header.Equals("GPGLL") || received.header.Equals("LCGLL")) // NMEA GPGLL may come with positioning data
{
m_linkLayer.log("StartRealTime: GPGLL packet received, count=" + total + " content=" + received);
// GPGGA is the best we can hope for, don't allow others to be processed if we had a recent GPGGA
if(DateTime.Now.Ticks > lastGPGGA.AddSeconds(10.0d).Ticks)
{
try
{
MPacket pvt = received.fromString();
// $GPGLL,3334.6464,N,11739.6583,W,052707.129,A*29
/*
* see http://www.gpsinformation.org/dale/nmea.htm for NMEA reference
*
GLL - Geographic Latitude and Longitude is a holdover from Loran data and some old units
may not send the time and data valid information if they are emulating Loran data.
If a gps is emulating Loran data they may use the LC Loran prefix instead of GP.
$GPGLL,4916.45,N,12311.12,W,225444,A,*31
Where:
GLL Geographic position, Latitude and Longitude
0 4916.46,N Latitude 49 deg. 16.45 min. North
2 12311.12,W Longitude 123 deg. 11.12 min. West
4 225444 Fix taken at 22:54:44 UTC
5 A Data valid or V (void)
*31 checksum data
*/
bool status = "A".Equals((string)pvt.fields[5]);
if(status)
{
double Lat = pvt.parseLat(0);
double Lng = pvt.parseLng(0);
double Elev = 0.0d;
pvtData.location = new GeoCoord(Lng, Lat, Elev);
//m_linkLayer.log("coord=" + pvtData.location);
// time component (only time part):
pvtData.time = pvt.parseNmeaTime(4, Project.localToZulu(DateTime.Now)); // UTC
pvtData.fix = 2; // assume two-dimensional
pvtData.comment = "received " + received.header;
realtimeCallback(pvtData);
}
total++;
errors = maxErrors;
}
catch(Exception ee)
{
m_linkLayer.logError("StartRealTime: " + ee.Message);
}
}
}
else if(received.header.Equals("GPGSV")) // NMEA GPGSV may come for satellite reception status
{
m_linkLayer.log("StartRealTime: GPGSV packet received, count=" + total + " content=" + received);
/*
* see http://www.gpsinformation.org/dale/nmea.htm for NMEA reference
*
$GPGSV,3,1,08,14,69,204,,15,57,105,36,18,45,047,36,03,42,263,36*71
$GPGSV,2,1,08,01,40,083,46,02,17,308,41,12,07,344,39,14,22,228,45*75
Where:
GSV Satellites in view
0 2 Number of sentences for full data
1 1 sentence 1 of 2
2 08 Number of satellites in view
for up to 4 satellites per sentence {
3 01 Satellite PRN number
4 40 Elevation, degrees
5 083 Azimuth, degrees
6 46 Signal strength - higher is better
}
*75 the checksum data, always begins with *
*/
//MPacket pvt = received.fromString();
//pvtData.comment = "received";
//realtimeCallback(pvtData);
total++;
errors = maxErrors;
}
else if(received.header.Equals("GPGSA")) // NMEA GPGSA may come for satellite status
{
m_linkLayer.log("StartRealTime: GPGSA packet received, count=" + total + " content=" + received);
// $GPGSA,A,2,15,18,14,31,,,,,,,,,05.6,05.6,*17
/*
* see http://www.gpsinformation.org/dale/nmea.htm for NMEA reference
*
GSA - GPS DOP and active satellites. This sentence provides details on the nature of the
fix. It includes the numbers of the satellites being used in the current solution and
the DOP. DOP (dilution of precision) is an indication of the effect of satellite geometry
on the accuracy of the fix. It is a unitless number where smaller is better. For 3D fixes
using 4 satellites a 1.0 would be considered to be a perfect number. For overdetermined
solutions it is possible to see numbers below 1.0. There are differences in the way the
PRN's are presented which can effect the ability of some programs to display this data.
For example, in the example shown below there are 5 satellites in the solution and
the null fields are scattered indicating that the almanac would show satellites in
the null positions that are not being used as part of this solution. Other receivers
might output all of the satellites used at the beginning of the sentence with the
null field all stacked up at the end. This difference accounts for some satellite
display programs not always being able to display the satellites being tracked.
$GPGSA,A,3,04,05,,09,12,,,24,,,,,2.5,1.3,2.1*39
Where:
GSA Satellite status
A Auto selection of 2D or 3D fix (M = manual)
3 3D fix - other values include: 1 = no fix
2 = 2D fix
04,05... PRNs of satellites used for fix (space for 12)
2.5 PDOP (dilution of precision)
1.3 Horizontal dilution of precision (HDOP)
2.1 Vertical dilution of precision (VDOP)
*39 the checksum data, always begins with *
*/
}
else if(received.header.Equals("PMGNST")) // Magellan PMGNST may come for device status
{
m_linkLayer.log("StartRealTime: PMGNST packet received, count=" + total + " content=" + received);
/*
$PMGNST,02.12,3,T,534,05.0,+03327,00*40
where:
ST status information
0 02.12 Firmware version number
1 3 2D or 3D
2 T True if we have a fix False otherwise
3 534 numbers change - unknown
4 05.0 time left on the gps battery in hours
5 +03327 numbers change (freq. compensation?)
6 00 PRN number receiving current focus
*40 checksum
*/
MPacket pvt = received.fromString();
bool haveFix = "T".Equals((string)pvt.fields[2]);
if(!haveFix)
{
pvtData.comment = "no satellite fix";
realtimeCallback(pvtData);
}
//total++;
errors = maxErrors;
}
else
{
m_linkLayer.log("StartRealTime: good other packet received, count=" + total + " content=" + received);
}
} // end while()
m_linkLayer.SendPacket(new MPacketCmd("NMEAOFF"));
m_linkLayer.SendPacket(new MPacketCmd("STOP"));
//if(Project.gpsMagellanHandshake)
{
m_linkLayer.SetHandshake(false);
}
m_linkLayer.log("StartRealTime: finished receiving fixes count=" + total);
}
public abstract void StartRealTime(GpsRealTimeHandler realtimeCallback);
public void StartRealTime(GpsRealTimeHandler realtimeCallback)
{
m_linkLayer.getPvtTransferProtocol().StartRealTime(realtimeCallback);
}
