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RACELOGIC Support Centre

What is the NMEA output format during a LabSat 3 replay?

LabSat 3 users can monitor the NMEA output, alongside the RF during replay. The NMEA output is available via the USB port on the rear of the LabSat 3, connecting to a PC will allow the output to be viewed in a terminal program.

The NMEA output from LabSat 3 will resemble the screenshot below.  Highlighted within the red square is an individual packet of the NMEA string.
 

nmea (1).png
 

GGA NMEA Format Definition

$GPGGA,hhmmss.ss,llll.ll,a,yyyyy.yy,a,x,xx,x.x,x.x,M,x.x,M,x.x,xxxx*hh
 

1    = UTC of Position

2    = Latitude

3    = N or S

4    = Longitude

5    = E or W

6    = GPS quality indicator (0=invalid; 1=GPS fix; 2=Diff. GPS fix)

7    = Number of satellites in use [not those in view]

8    = Horizontal dilution of position

9    = Antenna altitude above/below mean sea level (geoid)

10   = Meters  (Antenna height unit)

11   = Geoidal separation (Diff. between WGS-84 earth ellipsoid and mean sea level.  -=geoid is below WGS-84 ellipsoid)

12   = Meters  (Units of geoidal separation)

13   = Age in seconds since last update from diff. reference station

14   = Diff. reference station ID#

15   = Checksum
 

GSA NMEA Format Definition

$GPGSA,A,3,,,,,,16,18,,22,24,,,3.6,2.1,2.2*3C

$GPGSA,A,3,19,28,14,18,27,22,31,39,,,,,1.7,1.0,1.3*35
 

1    = Mode:

M=Manual, forced to operate in 2D or 3D

A=Automatic, 3D/2D

2    = Mode:

1=Fix not available

2=2D

3=3D

3-14 = IDs of SVs used in position fix (null for unused fields)

15   = PDOP

16   = HDOP

17   = VDOP
 

GSV NMEA Format Definition

$GPGSV,3,1,11,03,03,111,00,04,15,270,00,06,01,010,00,13,06,292,00*74

$GPGSV,3,2,11,14,25,170,00,16,57,208,39,18,67,296,40,19,40,246,00*74

$GPGSV,3,3,11,22,42,067,42,24,14,311,43,27,05,244,00,,,,*4D

 

$GPGSV,1,1,13,02,02,213,,03,-3,000,,11,00,121,,14,13,172,05*67

 

1     = Total number of messages of this type in this cycle

2     = Message number

3     = Total number of SVs in view

4     = SV PRN number

5     = Elevation in degrees, 90 maximum

6     = Azimuth, degrees from true north, 000 to 359

7     = SNR, 00-99 dB (null when not tracking)

8-11  = Information about second SV, same as field 4-7

12-15 = Information about third SV, same as field 4-7

16-19 = Information about fourth SV, same as field 4-7
 

GLL NMEA Format Definition

$GPGLL,3751.65,S,14507.36,E*77

$GPGLL,4916.45,N,12311.12,W,225444,A
 

4916.46,N          Latitude 49 deg. 16.45 min. North

12311.12,W       Longitude 123 deg. 11.12 min. West

225444              Fix taken at 22:54:44 UTC

A                        Data valid

 

$GPGLL,5133.81,N,00042.25,W*75

1     2     3     4    5

 

1  =  5133.81   Current latitude

2  =  N         North/South

3  =  00042.25  Current longitude

4  =  W         East/West

5  =  *75       checksum

 

RMC NMEA Format Definition

$GPRMC,081836,A,3751.65,S,14507.36,E,000.0,360.0,130998,011.3,E*62

$GPRMC,225446,A,4916.45,N,12311.12,W,000.5,054.7,191194,020.3,E*68
 

225446               Time of fix 22:54:46 UTC

A                         Navigation receiver warning A = OK, V = warning

4916.45,N           Latitude 49 deg. 16.45 min North

12311.12,W        Longitude 123 deg. 11.12 min West

000.5                  Speed over ground, Knots

054.7                  Course Made Good, True

191194               Date of fix  19 November 1994

020.3,E               Magnetic variation 20.3 deg East

*68                      Mandatory checksum
 

$GPRMC,220516,A,5133.82,N,00042.24,W,173.8,231.8,130694,004.2,W*70

1      2       3      4       5       6       7       8        9      10      11      12
 

      1 =  220516     Time Stamp

      2  = A          validity - A-ok, V-invalid

      3  = 5133.82    current Latitude

      4  = N          North/South

      5  = 00042.24   current Longitude

      6  = W          East/West

      7  = 173.8      Speed in knots

      8  = 231.8      True course

      9  = 130694     Date Stamp

      10 = 004.2      Variation

      11 = W          East/West

      12 = *70        checksum

 

$GPRMC,hhmmss.ss,A,llll.ll,a,yyyyy.yy,a,x.x,x.x,ddmmyy,x.x,a*hh

 

1    = UTC of position fix

2    = Data status (V=navigation receiver warning)

3    = Latitude of fix

4    = N or S

5    = Longitude of fix

6    = E or W

7    = Speed over ground in knots

8    = Track made good in degrees True

9    = UT date

10   = Magnetic variation degrees (Easterly var. subtracts from true course)

11   = E or W

12   = Checksum

 

VTG NMEA Format Definition

$GPVTG,360.0,T,348.7,M,000.0,N,000.0,K*43

$GPVTG,054.7,T,034.4,M,005.5,N,010.2,K
 

054.7,T      True track made good

034.4,M      Magnetic track made good

005.5,N      Ground speed, knots

010.2,K      Ground speed, Kilometers per hour
 

$GPVTG,t,T,,,s.ss,N,s.ss,K*hh

 

1    = Track made good

2    = Fixed text 'T' indicates that track made good is relative to true north

3    = not used

4    = not used

5    = Speed over ground in knots

6    = Fixed text 'N' indicates that speed over ground in in knots

7    = Speed over ground in kilometers/hour

8    = Fixed text 'K' indicates that speed over ground is in kilometers/hour

9    = Checksum

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