DATAGNSS GNSS Receiver NMEA Protocol Specification (NMEA V4.11)

    This document describes the NMEA 0183 V4.11 protocol implementation for DATAGNSS GNSS receivers.

    The default output includes GNGGA, GNGSA, GPGSV/GBGSV/etc., and GNRMC sent at a 1 period.

    1. Talker ID Prefixes

    Sentence prefixes identify the constellation or combination of constellations to which the message applies. Talker IDs are used as the first two characters of the NMEA sentence (after the $). Under NMEA V4.11, the following Talker IDs are supported:

    • GP: GPS / SBAS
    • GB: BeiDou
    • GL: GLONASS
    • GA: Galileo
    • GQ: QZSS
    • GI: NavIC (IRNSS)
    • GN: Combined multi-GNSS solution (used for $GNGGA, $GNRMC, $GNGSA, $GNGLL, $GNGST, $GNGRS, $GNVTG, $GNZDA)

    2. NMEA Messages Format

    Each sentence begins with $ and terminates with <CR><LF>. Sentences include an 8-bit XOR checksum appended after a * character.

    2.1 GNGGA - Global Positioning System Fix Data

    Provides UTC time, position, and fix-related data.

    Format:

    $GNGGA,hhmmss.fff,llll.lllllll,a,yyyyy.yyyyyyy,a,x,xx,x.x,x.x,M,x.x,M,x.x,xxxx*hh<CR><LF>

    GNGGA Field Descriptions

    Field # Format / Name Data Type Units Description
    0 $GNGGA String - NMEA Sentence Header
    1 hhmmss.fff String UTC UTC Time (HourMinuteSecond.fraction)
    2 llll.lllllll String Degrees Latitude: ddmm.mmmmmmm (Extended 7 decimals for high-precision series)
    3 a Character - Latitude hemisphere: N = North, S = South
    4 yyyyy.yyyyyyy String Degrees Longitude: dddmm.mmmmmmm (Extended 7 decimals for high-precision series)
    5 a Character - Longitude hemisphere: E = East, W = West
    6 x Integer - GNSS Quality Indicator (see table below)
    7 xx Integer - Number of satellites in use (00 to 40)
    8 x.x Float - Horizontal Dilution of Precision (HDOP)
    9 x.x Float Meters Antenna Altitude above/below mean-sea-level (geoid)
    10 M Character - Altitude Units: M = Meters
    11 x.x Float Meters Geoidal separation (WGS-84 earth ellipsoid to MSL). Negative - means MSL is below ellipsoid.
    12 M Character - Geoidal Separation Units: M = Meters
    13 x.x Float Seconds Age of differential GNSS data. Seconds since last SC104 Type 1 or 9 update. Null when DGPS/RTK is not used.
    14 xxxx Integer - Differential reference station ID (0000 to 1023)
    15 *hh Checksum - Hexadecimal checksum

    GNSS Quality Indicators (Field 6)

    Value Status Description
    0 Fix not available or invalid
    1 GNSS fix (SPS / Autonomous)
    2 Differential GNSS fix (DGPS)
    3 PPS fix
    4 Real Time Kinematic (RTK Fixed or CLAS RTK)
    5 Float RTK(CLAS RTK Float)
    6 Estimated (Dead Reckoning)
    7 Manual input mode
    8 Simulation mode

    Example: $GNGGA,071113.000,3957.7995312,N,11619.0286230,E,4,16,0.99,103.965,M,-8.408,M,1.0,4042*40

    2.2 GNGSA - GNSS DOP and Active Satellites

    Reports the receiver’s operating mode, active satellites used in the navigation solution, and Dilution of Precision (DOP) values. The combined $GNGSA sentence is output multiple times per cycle (once per active constellation) with a trailing System ID.

    Format:

    $GNGSA,a,m,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x.x,x.x,x.x,h*hh<CR><LF>

    GNGSA Field Descriptions

    Field # Format / Name Data Type Units Description
    0 $GNGSA String - NMEA Sentence Header
    1 a Character - Selection Mode: M = Manual (forced 2D/3D), A = Automatic
    2 m Integer - Mode: 1 = No fix, 2 = 2D fix, 3 = 3D fix
    3-14 x (12 fields) Integer - Satellite IDs (SVIDs) used in the position solution. Left-aligned, unused fields are empty/null.
    15 x.x Float - Position Dilution of Precision (PDOP)
    16 x.x Float - Horizontal Dilution of Precision (HDOP)
    17 x.x Float - Vertical Dilution of Precision (VDOP)
    18 h Integer - System ID (indicates which constellation this sentence describes, see table below)
    19 *hh Checksum - Hexadecimal checksum

    System ID Table (Field h)

    | System ID | Constellation | | :—: | :— | | 1 | GPS | | 2 | GLONASS | | 3 | GALILEO | | 4 | BEIDOU | | 5 | QZSS | | 6 | NavIC (IRNSS) |

    Satellite ID (SVID) Range Mapping

    SVIDs are mapped directly to their true constellation PRN ranges:

    Constellation SVID Range
    GPS 1 - 32
    GLONASS 65 - 96
    GALILEO 1 - 36
    BEIDOU 1 - 63
    QZSS 1 - 10
    NavIC (IRNSS) 1 - 18
    SBAS 40 - 54 (Original PRNs 120-141 offset by -87)

    Examples: $GNGSA,A,3,22,26,27,31,32,04,16,29,,,,,1.32,0.77,1.07,1*0D (GPS) $GNGSA,A,3,82,79,,,,,,,,,,,1.91,0.76,1.76,2*0E (GLONASS) $GNGSA,A,3,01,04,09,31,19,,,,,,,,1.32,0.77,1.07,3*03 (Galileo) $GNGSA,A,3,29,09,16,40,39,10,36,45,59,60,35,,1.91,0.76,1.76,4*0E (BeiDou) $GNGSA,A,3,02,04,07,,,,,,,,,,1.32,0.77,1.07,5*02 (QZSS) $GNGSA,A,3,04,07,03,09,05,02,,,,,,,2.41,1.40,1.96,6*04 (NavIC)

    2.3 GSV - GNSS Satellites in View

    Reports visible satellites, including SVID, elevation, azimuth, and SNR (C/N0). Separate GSV lists are output per constellation (Talker ID) and signal frequency (Signal ID).

    Format:

    $<Talker>GSV,total_msg,msg_num,total_sv,svid_1,elev_1,azim_1,snr_1,...,svid_4,elev_4,azim_4,snr_4,h*hh<CR><LF>

    (Talkers: $GPGSV for GPS/SBAS, $GBGSV for BeiDou, $GLGSV for GLONASS, $GAGSV for Galileo, $GQGSV for QZSS, $GIGSV for NavIC)

    GSV Field Descriptions

    Field # Format / Name Data Type Units Description
    0 $<Talker>GSV String - NMEA Sentence Header
    1 total_msg Integer - Total number of GSV messages in this signal group
    2 msg_num Integer - Message sequence number within the current group (1-indexed)
    3 total_sv Integer - Total number of satellites in view for this constellation
    4 svid_1 Integer - Satellite #1 PRN/ID number (with leading zero)
    5 elev_1 Integer Degrees Satellite #1 Elevation (00 to 90 degrees)
    6 azim_1 Integer Degrees Satellite #1 Azimuth to True North (000 to 359 degrees)
    7 snr_1 Integer dB-Hz Satellite #1 SNR / C/N0 (00 to 99), null when not tracked
    8-19 - - - Repeats SVID, Elevation, Azimuth, and SNR for Satellites 2, 3, and 4.
    20 h Character / Hex - Signal ID (defines the signal frequency band, see table below)
    21 *hh Checksum - Hexadecimal checksum

    GSV Signal ID Table (Field h)

    Constellation Signal ID Signal Name
    GPS (GNSS ID 1) 0
    1
    5
    6
    7
    8    		 All signals
    L1 C/A
    L2CM
    L2CL
    L5-I
    L5-Q
    GLONASS (GNSS ID 2) 0
    1
    3    		 All signals
    L1 C/A
    L2 C/A
    GALILEO (GNSS ID 3) 0
    1
    2
    3
    4
    5
    7    		 All signals
    E5a
    E5b
    E5a+b
    E6-A
    E6-BC
    L1-BC
    BEIDOU (GNSS ID 4) 0
    1
    2
    3
    4
    5
    6
    7
    8
    9
    A
    B
    C    		 All signals
    B1I
    B1Q
    B1C
    B1A
    B2-a
    B2-b
    B2 a+b
    B3I
    B3Q
    B3A
    B2I
    B2Q
    QZSS (GNSS ID 5) 0
    1
    2
    3
    4
    5
    6
    7
    8
    9
    A    		 All signals
    L1 C/A
    L1C (D)
    L1C (P)
    LIS
    L2C-M
    L2C-L
    L5-I
    L5-Q
    L6D
    L6E
    NavIC (IRNSS) (GNSS ID 6) 0
    1
    5    		 All signals
    L5-SPS
    L1-SPS

    Examples: $GPGSV,3,2,12,7,40,325,37,9,35,254,37,4,33,209,36,1,26,175,33,1*61 (GPS L1 C/A) $GPGSV,3,3,12,8,65,1,44,9,35,254,39,4,33,209,39,1,26,175,37,8*65 (GPS L5-Q) $GQGSV,2,1,06,195,62,100,38,199,59,149,33,194,56,55,38,1*56 (QZSS L1 C/A) $GQGSV,2,2,06,195,62,100,42,199,59,149,43,194,56,55,41,8*58 (QZSS L5-Q) $GLGSV,1,1,02,82,66,168,40,79,46,33,39,1*4D (GLONASS L1 C/A) $GBGSV,5,4,17,29,83,78,43,40,57,340,40,39,55,181,40,36,51,84,41,5*76 (BeiDou B2-a)

    2.4 GNRMC - Recommended Minimum Specific GNSS Data

    Provides key time, date, position, speed, and course data.

    Format:

    $GNRMC,hhmmss.fff,A,llll.lllllll,a,yyyyy.yyyyyyy,a,x.x,x.x,ddmmyy,x.x,a,a,a*hh<CR><LF>

    GNRMC Field Descriptions

    Field # Format / Name Data Type Units Description
    0 $GNRMC String - NMEA Sentence Header
    1 hhmmss.fff String UTC UTC Time (HourMinuteSecond.fraction)
    2 A Character - Status: A = Valid Data, V = Navigation receiver warning
    3 llll.lllllll String Degrees Latitude: ddmm.mmmmmmm (Extended 7 decimals for high-precision series)
    4 a Character - Hemisphere: N = North, S = South
    5 yyyyy.yyyyyyy String Degrees Longitude: dddmm.mmmmmmm (Extended 7 decimals for high-precision series)
    6 a Character - Hemisphere: E = East, W = West
    7 x.x Float Knots Speed over ground
    8 x.x Float Degrees Course over ground (True Track, degrees relative to True North)
    9 ddmmyy String UTC UTC Date (DayMonthYear)
    10 x.x Float Degrees Magnetic variation (null/empty on DATAGNSS receivers)
    11 a Character - Magnetic variation direction: E/W (null/empty)
    12 a Character - Mode Indicator (see table below)
    13 a Character - navStatus: S = Safe / Valid
    14 *hh Checksum - Hexadecimal checksum

    Mode Indicators (Field 12)

    • A: Autonomous (GNSS fix)
    • D: Differential GNSS fix (DGPS)
    • F: Float RTK
    • P: Precise
    • R: Real Time Kinematic (Fixed RTK)
    • V: Invalid (No fix)

    Example: $GNRMC,115522.000,A,4006.20885,N,11628.14498,E,0.000,0.50,041215,,,A,S*30

    2.5 GNVTG - Course over Ground and Ground Speed

    Reports the actual course and speed relative to the ground.

    Format:

    $GNVTG,x.x,T,x.x,M,x.x,N,x.x,K,a*hh<CR><LF>

    GNVTG Field Descriptions

    Field # Format / Name Data Type Units Description
    0 $GNVTG String - NMEA Sentence Header
    1 x.x Float Degrees Track Degrees (True course over ground)
    2 T Character - True Track unit indicator: T = True
    3 x.x Float Degrees Track Degrees (Magnetic course over ground, null/empty on DATAGNSS receivers)
    4 M Character - Magnetic Track unit indicator: M = Magnetic
    5 x.x Float Knots Speed over ground
    6 N Character - Speed unit indicator: N = Knots
    7 x.x Float km/h Speed over ground
    8 K Character - Speed unit indicator: K = Kilometers per hour
    9 a Character - Mode Indicator: A = Autonomous, D = Differential, V = Invalid
    10 *hh Checksum - Hexadecimal checksum

    Example: $GNVTG,0.50,T,,M,0.000,N,0.000,K,A*26

    2.6 GNZDA - Time & Date

    Provides UTC time, day, month, year, and local timezone offset.

    Format:

    $GNZDA,hhmmss.fff,dd,mm,yyyy,xx,yy*hh<CR><LF>

    GNZDA Field Descriptions

    Field # Format / Name Data Type Units Description
    0 $GNZDA String - NMEA Sentence Header
    1 hhmmss.fff String UTC UTC Time (HourMinuteSecond.fraction)
    2 dd Integer - UTC Day (01 - 31)
    3 mm Integer - UTC Month (01 - 12)
    4 yyyy Integer - UTC Year (4-digit format)
    5 xx Integer Hours Local zone hours offset (-13 to 13)
    6 yy Integer Minutes Local zone minutes offset (0 to 59)
    7 *hh Checksum - Hexadecimal checksum

    Example: $GNZDA,072319.000,14,10,2015,-7,45*5F

    2.7 GNGST - GNSS Pseudorange Error Statistics

    Reports statistical quality metrics for the computed position solution.

    Format:

    $GNGST,hhmmss.fff,rms,major,minor,orient,lat_std,lon_std,alt_std*hh<CR><LF>

    GNGST Field Descriptions

    Field # Format / Name Data Type Units Description
    0 $GNGST String - NMEA Sentence Header
    1 hhmmss.fff String UTC UTC Time (HourMinuteSecond.fraction)
    2 rms Float Meters RMS value of the standard deviation of range inputs
    3 major Float Meters Standard deviation of semi-major axis of error ellipse
    4 minor Float Meters Standard deviation of semi-minor axis of error ellipse
    5 orient Float Degrees Orientation of semi-major axis (degrees from True North)
    6 lat_std Float Meters Standard deviation of latitude error
    7 lon_std Float Meters Standard deviation of longitude error
    8 alt_std Float Meters Standard deviation of altitude error
    9 *hh Checksum - Hexadecimal checksum

    Example: $GPGST,082356.00,1.8,,,,1.7,1.3,2.2*7E