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GPS Sentences | NMEA Sentences | GPGGA GPGLL GPVTG GPRMC

This page describes GPS Sentences or NMEA Sentences with example patterns. These GPS Sentences (i.e. NMEA Sentences) covers GPGGA, GPGLL, GPVTG, GPRMC etc.

Introduction:
• A GPS receiver module requires only DC power supply for its operation. It will start outputting data as soon as it has identified GPS satellites within its range.
• GPS module uses plain ASCII protocol known as NMEA developed by National Marine Electronics Association. Hence they are also known as NMEA sentences.
• Each block of data is referred as "sentence". Each of these sentences are parsed independently.
• The default transmission rate of these gps sentences is 4800 bps. Certain GPS modules use serial rate of 9600 bps also. It uses 8 bits for ASCII character, no parity and 1 stop bit.
• Sentence begins with two letters to represent GPS device. For example, "GP" represent GPS device and so on.
• Remainder of sentence consists of letters/numerals in plain ASCII. A sentence can not have more than 80 characters.
• A sentence carry latitude, longitude, altitude and time of readings obtained from satellites.
• Some sentence data structures are proprietary developed by device manufacturers which begins with letter "P".

Following is the generic table which mentions functional description of NMEA output messages.

GPS Sentences or NMEA Sentences

NMEA Sentence Meaning
GPGGA Global positioning system fix data (time, position, fix type data)
GPGLL Geographic position, latitude, longitude
GPVTG Course and speed information relative to the ground
GPRMC Time, date, position, course and speed data
GPGSA GPS receiver operating mode, satellites used in the position solution, and DOP values.
GPGSV The number of GPS satellites in view satellite ID numbers, elevation, azimuth and SNR values.
GPMSS Signal to noise ratio, signal strength, frequency, and bit rate from a radio beacon receiver.
GPTRF Transit fix data
GPSTN Multiple data ID
GPXTE cross track error, measured
GPZDA Date and time (PPS timing message, synchronized to PPS).
150 OK to send message.

GPS sentence | GPGGA

Following table mentions GPGGA sentence description with example.
➤Example of GPGGA GPS sentence:-
$GPGGA, 161229.487, 3723.2475, N, 12158.3416, W, 1, 07, 1.0, 9.0, M, , , , 0000*18

Name or Field Example Description
Message ID $GPGGA GGA protocol header
UTC time 161229.487 hhmmss.sss
Latitude 3723.2475 (37 degrees, 23.2475 minutes) ddmm.mmmm
N/S Indicator N N = North, S = South
Longitude 12158.3416 (121 degrees, 58.3416 minutes) dddmm.mmmm
E/W indicator W E = East or W = West
Position Fix Indicator 1 GPS Sentences Position Fix Indicator
Satellites used 07 Range is 0 to 12
HDOP 1.0 Horizontal Dilution of Precision
MSL Altitude 9.0 Meters
Units M Meters
Geoid Separation Meters
Units M Meters
Age of diff. corr. Second
Diff. ref. station ID 0000
Checksum *18
<CR><LF> End of message termination

GPS sentence | GPGLL

Following table mentions GPGLL sentence description with example.
➤Example of GPGLL GPS sentence:-
$GPGLL, 3723.2475, N, 12158.3416, W, 161229.487, A, A*41

Name or Field Example Description
Message ID $GPGLL GLL protocol header
Latitude 3723.2475 ddmm.mmmm
N/S indicator N N =North or S = south
Longitude 12158.3416 dddmm.mmmm
E/W indicator W E =East or W = West
UTC time 161229.487 hhmmss.sss
Status A A = data valid or V = data not valid
Mode A A =Autonomous , D =DGPS, E =DR (This field is only present in NMEA version 3.0)
Checksum *41
<CR><LF> End of message termination

GPS sentence | GPVTG

Following table mentions GPVTG sentence description with example.
➤Example of GPVTG GPS sentence:-
$GPVTG, 309.62, T, ,M, 0.13, N, 0.2, K, A*23

Name or Field Example Description
Message ID $GPVTG VTG protocol header
Course 309.62 degrees
Reference T True
Course Degrees
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
Mode A A = Autonomous, D = DGPS, E = DR
Checksum *23
<CR><LF> End of message termination

GPS sentence | GPRMC

Following table mentions GPRMC sentence description with example.
➤Example of GPRMC GPS sentence:-
$GPRMC, 161229.487, A, 3723.2475, N, 12158.3416, W, 0.13, 309.62, 120598, , *10

Name or Field Example Description
Message ID $GPRMC RMC Protocol Header
UTC time 161229.487 hhmmss.sss
Status A A = data valid or V = data not valid
Latitude 3723.2475 ddmm.mmmm
N/S indicator N N = North or S = South
Longitude 12158.3416 dddmm.mmmm
E/W indicator W E = East or W = West
Speed over ground 0.13 knots
Course over ground 309.62 degrees
Date 120598 ddmmyy
Magnetic Variation Degrees (E= East or W = West)
Mode A A = Autonomous, D = DGPS, E =DR
Checksum *10
<CR><LF> End of message termination


GPS RELATED LINKS

What is GPS system?  GPS vs AGPS  GPS Frame Structure  GPS vs GPRS  GPS Basics Tutorial  GPS Antenna  GPS Receiver Module  GPS Satellite  GPS Tracking System 

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