SatSleuth GPS Tracking

Common NMEA Setence types

The following information describes the most common NMEA-0183 sentences transmitted by GPS receivers. The NMEA standard provides quite a range of sentences, but many relate to non-GPS devices and some others are GPS related but rarely used. We normally recommend the use of NMEA mode for new GPS applications to give maximum compatibility with all GPS receivers. Most GPS receivers also have a binary mode but it is normally best to reserve the use of binary GPS protocols for applications that really require their use, such as those requiring position updates of greater than once per second.

We also have a page that covers other NMEA sentences that are also used by GPS receivers, although somewhat less commonly.

Sentence	Description
$GPGGA	Global positioning system fixed data
$GPGLL	Geographic position - latitude / longitude
$GPGSA	GNSS DOP and active satellites
$GPGSV	GNSS satellites in view
$GPRMC	Recommended minimum specific GNSS data
$GPVTG	Course over ground and ground speed

$GPGGA Sentence (Fix data)

Example (signal not acquired): $GPGGA,235947.000,0000.0000,N,00000.0000,E,0,00,0.0,0.0,M,,,,0000*00
Example (signal acquired): $GPGGA,092204.999,4250.5589,S,14718.5084,E,1,04,24.4,19.7,M,,,,0000*1F

Field	Example	Comments
Sentence ID	$GPGGA
UTC Time	092204.999	hhmmss.sss
Latitude	4250.5589	ddmm.mmmm
N/S Indicator	S	N = North, S = South
Longitude	14718.5084	dddmm.mmmm
E/W Indicator	E	E = East, W = West
Position Fix	1	0 = Invalid, 1 = Valid SPS, 2 = Valid DGPS, 3 = Valid PPS
Satellites Used	04	Satellites being used (0-12)
HDOP	24.4	Horizontal dilution of precision
Altitude	19.7	Altitude in meters according to WGS-84 ellipsoid
Altitude Units	M	M = Meters
Geoid Seperation		Geoid seperation in meters according to WGS-84 ellipsoid
Seperation Units		M = Meters
DGPS Age		Age of DGPS data in seconds
DGPS Station ID	0000
Checksum	*1F
Terminator	CR/LF

$GPGLL Sentence (Position)

Example (signal not acquired): $GPGLL,0000.0000,N,00000.0000,E,235947.000,V*2D
Example (signal acquired): $GPGLL,4250.5589,S,14718.5084,E,092204.999,A*2D

Field	Example	Comments
Sentence ID	$GPGLL
Latitude	4250.5589	ddmm.mmmm
N/S Indicator	S	N = North, S = South
Longitude	14718.5084	dddmm.mmmm
E/W Indicator	E	E = East, W = West
UTC Time	092204.999	hhmmss.sss
Status	A	A = Valid, V = Invalid
Checksum	*2D
Terminator	CR/LF

$GPGSA Sentence (Active satellites)

Example (signal not acquired): $GPGSA,A,1,,,,,,,,,,,,,0.0,0.0,0.0*30
Example (signal acquired): $GPGSA,A,3,01,20,19,13,,,,,,,,,40.4,24.4,32.2*0A

Field	Example	Comments
Sentence ID	$GPGSA
Mode 1	A	A = Auto 2D/3D, M = Forced 2D/3D
Mode 1	3	1 = No fix, 2 = 2D, 3 = 3D
Satellite used 1	01	Satellite used on channel 1
Satellite used 2	20	Satellite used on channel 2
Satellite used 3	19	Satellite used on channel 3
Satellite used 4	13	Satellite used on channel 4
Satellite used 5		Satellite used on channel 5
Satellite used 6		Satellite used on channel 6
Satellite used 7		Satellite used on channel 7
Satellite used 8		Satellite used on channel 8
Satellite used 9		Satellite used on channel 9
Satellite used 10		Satellite used on channel 10
Satellite used 11		Satellite used on channel 11
Satellite used 12		Satellite used on channel 12
PDOP	40.4	Position dilution of precision
HDOP	24.4	Horizontal dilution of precision
VDOP	32.2	Vertical dilution of precision
Checksum	*0A
Terminator	CR/LF

$GPGSV Sentence (Satellites in view)

Example (signal not acquired): $GPGSV,1,1,01,21,00,000,*4B
Example (signal acquired): $GPGSV,3,1,10,20,78,331,45,01,59,235,47,22,41,069,,13,32,252,45*70

Field	Example	Comments
Sentence ID	$GPGSV
Number of messages	3	Number of messages in complete message (1-3)
Sequence number	1	Sequence number of this entry (1-3)
Satellites in view	10
Satellite ID 1	20	Range is 1-32
Elevation 1	78	Elevation in degrees (0-90)
Azimuth 1	331	Azimuth in degrees (0-359)
SNR 1	45	Signal to noise ration in dBHZ (0-99)
Satellite ID 2	01	Range is 1-32
Elevation 2	59	Elevation in degrees (0-90)
Azimuth 2	235	Azimuth in degrees (0-359)
SNR 2	47	Signal to noise ration in dBHZ (0-99)
Satellite ID 3	22	Range is 1-32
Elevation 3	41	Elevation in degrees (0-90)
Azimuth 3	069	Azimuth in degrees (0-359)
SNR 3		Signal to noise ration in dBHZ (0-99)
Satellite ID 4	13	Range is 1-32
Elevation 4	32	Elevation in degrees (0-90)
Azimuth 4	252	Azimuth in degrees (0-359)
SNR 4	45	Signal to noise ration in dBHZ (0-99)
Checksum	*70
Terminator	CR/LF

$GPRMC Sentence (Position and time)

Example (signal not acquired): $GPRMC,235947.000,V,0000.0000,N,00000.0000,E,,,041299,,*1D
Example (signal acquired): $GPRMC,092204.999,A,4250.5589,S,14718.5084,E,0.00,89.68,211200,,*25

Field	Example	Comments
Sentence ID	$GPRMC
UTC Time	092204.999	hhmmss.sss
Status	A	A = Valid, V = Invalid
Latitude	4250.5589	ddmm.mmmm
N/S Indicator	S	N = North, S = South
Longitude	14718.5084	dddmm.mmmm
E/W Indicator	E	E = East, W = West
Speed over ground	0.00	Knots
Course over ground	0.00	Degrees
UTC Date	211200	DDMMYY
Magnetic variation		Degrees
Magnetic variation		E = East, W = West
Checksum	*25
Terminator	CR/LF

$GPVTG Sentence (Course over ground)

Example (signal not acquired): $GPVTG,,T,,M,,N,,K*4E
Example (signal acquired): $GPVTG,89.68,T,,M,0.00,N,0.0,K*5F

Field	Example	Comments
Sentence ID	$GPVTG
Course	89.68	Course in degrees
Reference	89.68	T = True heading
Course		Course in degrees
Reference	89.68	M = Magnetic heading
Speed	0.00	Horizontal speed
Units	N	N = Knots
Speed	0.00	Horizontal speed
Units	K	K = KM/h
Checksum	*5F
Terminator	CR/LF