NMEA Sentences

The LC29H outputs NMEA 0183 v4.10 sentences. This page documents each sentence type with field-by-field descriptions and examples.

GGA — Position Fix Data

Position fix with quality, satellite count, dilution of precision, and altitude.

$GNGGA,014033.00,2232.46820,N,11404.67480,E,4,18,0.7,42.3,M,-2.4,M,1.0,0000*71

Field	Name	Format	Example	Description
0	UTC Time	hhmmss.ss	014033.00	Hours, minutes, seconds
1	Latitude	ddmm.mmmmm	2232.46820	Degrees and decimal minutes
2	N/S	char	N	North or South hemisphere
3	Longitude	dddmm.mmmmm	11404.67480	Degrees and decimal minutes
4	E/W	char	E	East or West hemisphere
5	Fix Quality	digit	4	See Fix Quality table
6	Satellites Used	int	18	Count of satellites in solution
7	HDOP	float	0.7	Horizontal Dilution of Precision
8	Altitude	float	42.3	Altitude above mean sea level
9	Alt Units	char	M	Meters
10	Geoid Sep	float	-2.4	Geoidal separation
11	Sep Units	char	M	Meters
12	DGPS Age	float	1.0	Age of DGPS correction (seconds)
13	DGPS Ref ID	int	0000	Reference station ID

RMC — Recommended Minimum

The fundamental position-velocity-time sentence.

$GNRMC,010555.000,A,2232.4682,N,11404.6748,E,0.00,125.29,230822,,,D,V*0C

Field	Name	Format	Example	Description
0	UTC Time	hhmmss.sss	010555.000	Time of fix
1	Status	char	A	A=active (valid), V=void
2	Latitude	ddmm.mmmm	2232.4682	Degrees and decimal minutes
3	N/S	char	N	Hemisphere
4	Longitude	dddmm.mmmm	11404.6748	Degrees and decimal minutes
5	E/W	char	E	Hemisphere
6	Speed	float	0.00	Speed over ground (knots)
7	Course	float	125.29	Course over ground (degrees true)
8	Date	ddmmyy	230822	Day, month, year
9	Mag Var	float		Magnetic variation (not output by LC29H)
10	Mag Dir	char		E or W (not output by LC29H)
11	Mode	char	D	Positioning mode indicator
12	Nav Status	char	V	NMEA v4.10: S=safe, C=caution, U=unsafe, V=not valid

Mode Indicator (RMC field 11)

Char	Mode	Fix Type
N	No fix	NO_FIX (0)
A	Autonomous	GPS_FIX (1)
D	Differential	DGPS_FIX (2)
R	RTK Fixed	RTK_FIXED (4)
F	RTK Float	RTK_FLOAT (5)
E	Estimated / DR	ESTIMATED (6)
M	Manual	MANUAL (7)
S	Simulator	SIMULATION (8)

GSA — DOP and Active Satellites

Dilution of precision and PRN numbers of satellites used in the fix.

$GNGSA,A,3,01,03,06,09,17,19,21,22,30,,,,1.1,0.7,0.9,1*33

Field	Name	Format	Example	Description
0	Op Mode	char	A	A=automatic 2D/3D, M=manual
1	Fix Type	digit	3	1=no fix, 2=2D, 3=3D
2–13	SV PRN	int	01	PRN of satellite used (up to 12 slots)
14	PDOP	float	1.1	Position DOP
15	HDOP	float	0.7	Horizontal DOP
16	VDOP	float	0.9	Vertical DOP
17	System ID	int	1	1=GPS, 2=GLONASS, 3=Galileo, 4=BeiDou

Multiple GSA sentences are output per epoch, one per constellation.

GSV — Satellites in View

Satellite tracking: PRN, elevation, azimuth, and SNR. Each sentence carries up to 4 satellites.

$GPGSV,3,1,11,01,45,090,42,03,70,315,45,06,12,045,38,09,55,180,44,1*6E

Field	Name	Format	Example	Description
0	Total Msgs	int	3	Total GSV sentences in this cycle
1	Msg Number	int	1	Sequence number
2	Total SVs	int	11	Total satellites in view
3	SV PRN	int	01	Satellite PRN number
4	Elevation	int	45	Degrees above horizon (0–90)
5	Azimuth	int	090	Degrees from true north (000–359)
6	SNR	int	42	Signal-to-noise ratio (dB-Hz)
7–18	(repeat)			2nd, 3rd, 4th satellite blocks
19	Signal ID	int	1	NMEA v4.10: signal identifier

PRN Numbering by Constellation

Constellation	PRN Range	Notes
GPS	1–32	Standard space vehicles
SBAS	33–64	WAAS, EGNOS, MSAS, GAGAN
GLONASS	65–96	PRN = slot + 64
Galileo	1–36	Separate GSV via $GA talker
BeiDou	1–63	Separate GSV via $GB talker
QZSS	1–10	Separate GSV via $QZ talker

VTG — Course and Speed

$GNVTG,125.29,T,,M,0.00,N,0.00,K,D*26

Field	Name	Format	Example	Description
0	Course True	float	125.29	Degrees true north
1	True Ref	char	T	Always T
2	Course Mag	float		Degrees magnetic (often empty)
3	Mag Ref	char	M	Always M
4	Speed Knots	float	0.00	Speed over ground in knots
5	Knots Unit	char	N	Always N
6	Speed km/h	float	0.00	Speed over ground in km/h
7	km/h Unit	char	K	Always K
8	Mode	char	D	Positioning mode

GLL — Geographic Position

$GNGLL,2232.46820,N,11404.67480,E,014033.00,A,D*7A

Field	Name	Format	Example	Description
0	Latitude	ddmm.mmmmm	2232.46820	Degrees and decimal minutes
1	N/S	char	N	Hemisphere
2	Longitude	dddmm.mmmmm	11404.67480	Degrees and decimal minutes
3	E/W	char	E	Hemisphere
4	UTC Time	hhmmss.ss	014033.00	Time of position
5	Status	char	A	A=valid, V=invalid
6	Mode	char	D	Positioning mode (NMEA v4.10+)

GNS — Extended Fix Data

Combined fix data from multiple constellations with per-constellation mode indicators.

$GNGNS,014033.00,2232.46820,N,11404.67480,E,RRRR,18,0.7,42.3,-2.4,1.0,0000,V*55

Field	Name	Format	Example	Description
0	UTC Time	hhmmss.ss	014033.00	Time of fix
1	Latitude	ddmm.mmmmm	2232.46820	Degrees and decimal minutes
2	N/S	char	N	Hemisphere
3	Longitude	dddmm.mmmmm	11404.67480	Degrees and decimal minutes
4	E/W	char	E	Hemisphere
5	Mode	string	RRRR	One char per constellation
6	Satellites	int	18	Count in solution
7	HDOP	float	0.7	Horizontal DOP
8	Altitude	float	42.3	MSL altitude (meters)
9	Geoid Sep	float	-2.4	Geoidal separation
10	DGPS Age	float	1.0	Correction age (seconds)
11	Ref ID	int	0000	Reference station ID
12	Nav Status	char	V	S=safe, C=caution, U=unsafe, V=not valid

GNS Mode Characters (field 5, one per constellation in order GPS/GLONASS/Galileo/BeiDou):

N=No fix, A=Autonomous, D=Differential, P=Precise, R=RTK Fixed, F=RTK Float, E=DR, M=Manual, S=Simulator

ZDA — Time and Date

UTC time and date. Useful for time synchronization applications.

GRS / GST — Range Residuals and Error Statistics

Available on some variants for pseudorange residuals (GRS) and error statistics (GST). These are advanced sentences primarily used for quality analysis.

Fix Quality Indicators

Value	Name	Description
0	No Fix	Position not available
1	GPS Fix	Standard autonomous fix
2	DGPS Fix	Differential correction applied
3	PPS Fix	Precise Positioning Service
4	RTK Fixed	Centimeter accuracy
5	RTK Float	Decimeter accuracy
6	Estimated	Dead reckoning
7	Manual	Manually entered
8	Simulation	Simulator mode

Default Output Configuration

Sentence	Default Rate	PAIR Command
GGA	1 (every fix)	PAIR073
GLL	0 (disabled)	PAIR070
GSA	1 (every fix)	PAIR074
GSV	1 (every fix)	PAIR075
RMC	1 (every fix)	PAIR071
VTG	1 (every fix)	PAIR072
GNS	0 (disabled)	PAIR076