Protocol Support Matrix¶

This page tracks message/PGN support and implementation details.

NMEA 0183¶

Message	Implemented	Tested	Notes
APB	✅ Yes	✅ Yes	Autopilot Sentence "B"
DBT	✅ Yes	✅ Yes	Depth Below Transducer
DPT	✅ Yes	✅ Yes	Depth of Water
GGA	✅ Yes	✅ Yes	Global Positioning System Fix Data
GLL	✅ Yes	✅ Yes	Geographic Position
GSA	✅ Yes	✅ Yes	GPS DOP and Active Satellites
GSV	✅ Yes	✅ Yes	GPS Satellites in View
HDG	✅ Yes	✅ Yes	Heading, Deviation and Variation
HDM	✅ Yes	✅ Yes	Heading, Magnetic
MTW	✅ Yes	✅ Yes	Mean Temperature of Water
MWV	✅ Yes	✅ Yes	Wind Speed and Angle
RMA	✅ Yes	✅ Yes	Recommended Minimum Specific Loran-C Data
RMB	✅ Yes	✅ Yes	Recommended Minimum Navigation Information
RMC	✅ Yes	✅ Yes	Recommended Minimum Navigation Data
VHW	✅ Yes	✅ Yes	Water Speed and Heading
VLW	✅ Yes	✅ Yes	Distance Traveled Through Water
VTG	✅ Yes	✅ Yes	Course Over Ground and Ground Speed
VWR	✅ Yes	✅ Yes	Relative Wind Speed and Angle
XDR	✅ Yes	✅ Yes	Transducer Measurements
XTE	✅ Yes	✅ Yes	Cross-Track Error, Measured
ZDA	✅ Yes	✅ Yes	Time and Date

NMEA 2000¶

Message / Transport	Implemented	Tested	Notes
Single-frame messages	✅ Yes	❌ No	Standard one-frame CAN payloads
Fast-packet transport	❌ No	❌ No	Multi-frame transport handling
PGN 128001	✅ Yes	✅ Yes	Vessel Acceleration
PGN 127245	✅ Yes	✅ Yes	Rudder
PGN 127250	✅ Yes	✅ Yes	Vessel Heading
PGN 127251	✅ Yes	✅ Yes	Rate of Turn
PGN 127257	✅ Yes	✅ Yes	Attitude (yaw, pitch, roll)
PGN 128259	✅ Yes	✅ Yes	Speed, Water Referenced
PGN 130306	✅ Yes	✅ Yes	Wind Data

Detailed Message/PGN Descriptions¶

NMEA 0183¶

This information has beed sourced from the gpsd documentation. All credits go to Eric S. Raymond esr@thyrsus.com.

GGA — Global Positioning System Fix Data¶

Provides time, position, and fix-related data for a GPS receiver.

Sentence format

                                                      11
        1         2       3 4        5 6 7  8   9  10 |  12 13  14   15
        |         |       | |        | | |  |   |   | |   | |   |    |
$--GGA,hhmmss.ss,ddmm.mm,a,dddmm.mm,a,x,xx,x.x,x.x,M,x.x,M,x.x,xxxx*hh<CR><LF>

Field definitions¶

#	Field	Description
1	UTC time (`hhmmss.ss`)	Hours, minutes, seconds
2	Latitude (`ddmm.mm`)	Degrees and minutes
3	Latitude hemisphere	`N` or `S`
4	Longitude (`dddmm.mm`)	Degrees and minutes
5	Longitude hemisphere	`E` or `W`
6	GPS quality indicator	`0` = Fix not available, `1` = GPS fix, `2` = DGPS fix, `3` = PPS fix, `4` = RTK, `5` = Float RTK, `6` = Estimated, `7` = Manual input mode, `8` = Simulation mode
7	Satellites in use	`00` to `12`
8	Horizontal dilution of precision (HDOP)	Meters
9	Antenna altitude	Above/below mean sea level (geoid), meters
10	Altitude units	`M` (meters)
11	Geoidal separation	Difference between WGS-84 ellipsoid and mean sea level (`-` means mean sea level is below ellipsoid)
12	Geoidal separation units	`M` (meters)
13	Age of DGPS data	Seconds since last SC104 Type 1 or 9 update (empty if unused)
14	Differential reference station ID	`0000` to `1023`
15	Checksum	`*hh`

The number of digits after the decimal point for time, latitude, and longitude is model-dependent.

Example

$GNGGA,001043.00,4404.14036,N,12118.85961,W,1,12,0.98,1113.0,M,-21.3,M*47

Note: Jackson Labs replaces the quality indicator with GPSDO status.

GLL — Geographic Position - Latitude/Longitude¶

Provides latitude, longitude, and time of position fix.

Sentence format

        1       2 3        4 5         6 7
        |       | |        | |         | |
$--GLL,ddmm.mm,a,dddmm.mm,a,hhmmss.ss,a*hh<CR><LF>

NMEA 2.3 and later:

$--GLL,ddmm.mm,a,dddmm.mm,a,hhmmss.ss,a,m*hh<CR><LF>

Field definitions¶

#	Field	Description
1	Latitude (`ddmm.mm`)	Degrees and minutes
2	Latitude hemisphere	`N` or `S`
3	Longitude (`dddmm.mm`)	Degrees and minutes
4	Longitude hemisphere	`E` or `W`
5	UTC time (`hhmmss.ss`)	Hours, minutes, seconds
6	Status	`A` = Data valid, `V` = Data invalid
7	FAA mode indicator	NMEA 2.3 and later
8	Checksum	`*hh`

The number of digits after the decimal point for time, latitude, and longitude is model-dependent.

Example

$GNGLL,4404.14012,N,12118.85993,W,001037.00,A,A*67

Provides essential minimum navigation data.

Sentence format

        1         2 3       4 5        6  7   8   9    10 11
        |         | |       | |        |  |   |   |    |  |
$--RMC,hhmmss.ss,A,ddmm.mm,a,dddmm.mm,a,x.x,x.x,xxxx,x.x,a*hh<CR><LF>

NMEA 2.3:

$--RMC,hhmmss.ss,A,ddmm.mm,a,dddmm.mm,a,x.x,x.x,xxxx,x.x,a,m*hh<CR><LF>

NMEA 4.1:

$--RMC,hhmmss.ss,A,ddmm.mm,a,dddmm.mm,a,x.x,x.x,xxxx,x.x,a,m,s*hh<CR><LF>

Field definitions¶

#	Field	Description
1	UTC time (`hhmmss.ss`)	Hours, minutes, seconds
2	Status	`A` = Valid, `V` = Warning
3	Latitude (`ddmm.mm`)	Degrees and minutes
4	Latitude hemisphere	`N` or `S`
5	Longitude (`dddmm.mm`)	Degrees and minutes
6	Longitude hemisphere	`E` or `W`
7	Speed over ground	Knots
8	Track made good	Degrees true
9	Date (`ddmmyy`)	UTC date
10	Magnetic variation	Degrees
11	Magnetic variation direction	`E` or `W`
12	FAA mode indicator	NMEA 2.3 and later
13	Navigation status	NMEA 4.1 and later: `A` Autonomous, `D` Differential, `E` Estimated, `M` Manual input mode, `N` Not valid, `S` Simulator, `V` Valid
14	Checksum	`*hh`

A status of V means the GPS has a valid fix that is below an internal quality threshold, e.g., because the dilution of precision is too high or an elevation mask test failed.

The number of digits after the decimal point for time, latitude, and longitude is model-dependent.

Example

$GNRMC,001031.00,A,4404.13993,N,12118.86023,W,0.146,,100117,,,A*7B

VTG — Track Made Good and Ground Speed¶

Provides course over ground and ground speed information.

Sentence format

         1  2  3  4  5  6  7  8 9
         |  |  |  |  |  |  |  | |
$--VTG,x.x,T,x.x,M,x.x,N,x.x,K*hh<CR><LF>

NMEA 2.3 and later:

$--VTG,x.x,T,x.x,M,x.x,N,x.x,K,m*hh<CR><LF>

Field definitions¶

#	Field	Description
1	Course over ground (degrees True)	Numeric angle
2	`T`	True reference indicator
3	Course over ground (degrees Magnetic)	Numeric angle
4	`M`	Magnetic reference indicator
5	Speed over ground (knots)	Numeric speed
6	`N`	Knots unit indicator
7	Speed over ground (km/h)	Numeric speed
8	`K`	Kilometers per hour unit indicator
9	FAA mode indicator	NMEA 2.3 and later
10	Checksum	`*hh`

In some older versions of NMEA 0183, the sentence appears as:

         1  2  3   4  5
         |  |  |   |  |
$--VTG,x.x,x,x.x,x.x*hh<CR><LF>

Old format field definitions

#	Field	Description
1	True course over ground (degrees)	`000` to `359`
2	Magnetic course over ground (degrees)	`000` to `359`
3	Speed over ground (knots)	`00.0` to `99.9`
4	Speed over ground (kilometers)	`00.0` to `99.9`
5	Checksum	`*hh`

The two forms can be distinguished by field 2, which will be the fixed text T in the newer form. The new form appears to have been introduced with NMEA 3.01 in 2002.

Some devices, such as those described in [GLOBALSAT], leave the magnetic-bearing fields 3 and 4 empty.

Example

$GPVTG,220.86,T,,M,2.550,N,4.724,K,A*34

VHW — Water Speed and Heading¶

Provides vessel heading and speed relative to the water.

Sentence format

        1   2 3   4 5   6 7   8 9
        |   | |   | |   | |   | |
$--VHW,x.x,T,x.x,M,x.x,N,x.x,K*hh<CR><LF>

Field definitions¶

#	Field	Description
1	Heading degrees (True)	Numeric angle
2	`T`	True reference indicator
3	Heading degrees (Magnetic)	Numeric angle
4	`M`	Magnetic reference indicator
5	Speed of vessel relative to water (knots)	Numeric speed
6	`N`	Knots unit indicator
7	Speed of vessel relative to water (km/h)	Numeric speed
8	`K`	Kilometers per hour unit indicator
9	Checksum	`*hh`

[GLOBALSAT] describes a different format in which the first three fields are water-temperature measurements. It’s not clear which is correct.

HDG — Heading, Deviation & Variation¶

Sentence Structure¶

        1   2   3 4   5 6
        |   |   | |   | |
 $--HDG,x.x,x.x,a,x.x,a*hh<CR><LF>

Field definitions¶

#	Field	Unit	Description
1	Magnetic sensor heading	degrees	Heading as reported by magnetic sensor
2	Magnetic deviation	degrees	Magnitude of deviation
3	Deviation direction	—	`E` = Easterly, `W` = Westerly
4	Magnetic variation	degrees	Magnitude of variation
5	Variation direction	—	`E` = Easterly, `W` = Westerly
6	Checksum	—	`*hh`

DBT — Depth Below Transducer¶

Reports water depth below the transducer in multiple units.

Sentence format

        1   2 3   4 5   6 7
        |   | |   | |   | |
$--DBT,x.x,f,x.x,M,x.x,F*hh<CR><LF>

Field definitions¶

#	Field	Description
1	Water depth (feet)	Numeric depth
2	`f`	Feet unit indicator
3	Water depth (meters)	Numeric depth
4	`M`	Meters unit indicator
5	Water depth (fathoms)	Numeric depth
6	`F`	Fathoms unit indicator
7	Checksum	`*hh`

In real-world sensors, sometimes not all three conversions are reported.
For example: $SDDBT,,f,22.5,M,,F*cs

Example

$SDDBT,7.8,f,2.4,M,1.3,F*0D

DPT — Depth of Water¶

Sentence Structure¶

        1   2   3   4
        |   |   |   |
 $--DPT,x.x,x.x,x.x*hh<CR><LF>

Field definitions¶

#	Field	Unit	Description
1	Water depth	meters	Depth relative to transducer
2	Transducer offset	meters	Positive = distance from transducer to waterline; Negative = distance from transducer to keel
3	Max range scale	meters	Maximum range scale in use (NMEA 3.0 and above)
4	Checksum	—	`*hh`

Example¶

$INDPT,2.3,0.0*46

Notes¶

⚠️ This sentence was incorrectly titled "Heading - Deviation & Variation" in [BETKE].

Reference: Humminbird DPT Documentation

MWV — Wind Speed and Angle¶

Reports wind angle and speed, with reference and validity.

Sentence format

        1   2 3   4 5
        |   | |   | |
$--MWV,x.x,a,x.x,a*hh<CR><LF>

Field definitions¶

#	Field	Description
1	Wind angle	`0` to `359` degrees
2	Reference	`R` = Relative, `T` = True
3	Wind speed	Numeric value
4	Wind speed units	`K` = km/h, `M` = m/s, `N` = knots
5	Status	`A` = Data valid, `V` = Invalid
6	Checksum	`*hh`

Example

$WIMWV,45.0,R,10.5,N,A*1F

GSA — GPS DOP and Active Satellites¶

Reports DOP (Dilution of Precision) and active satellites used for the fix.

Sentence format

        1 2 3                        14 15  16  17  18
        | | |                         |  |   |   |   |
$--GSA,a,a,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x.x,x.x,x.x*hh<CR><LF>

Field definitions¶

#	Field	Description
1	Selection mode	`M` = Manual (forced 2D/3D), `A` = Automatic (2D/3D)
2	Mode	`1` = No fix, `2` = 2D fix, `3` = 3D fix
3	ID of 1st satellite used for fix	Satellite ID
4	ID of 2nd satellite used for fix	Satellite ID
5	ID of 3rd satellite used for fix	Satellite ID
6	ID of 4th satellite used for fix	Satellite ID
7	ID of 5th satellite used for fix	Satellite ID
8	ID of 6th satellite used for fix	Satellite ID
9	ID of 7th satellite used for fix	Satellite ID
10	ID of 8th satellite used for fix	Satellite ID
11	ID of 9th satellite used for fix	Satellite ID
12	ID of 10th satellite used for fix	Satellite ID
13	ID of 11th satellite used for fix	Satellite ID
14	ID of 12th satellite used for fix	Satellite ID
15	PDOP	Position Dilution of Precision
16	HDOP	Horizontal Dilution of Precision
17	VDOP	Vertical Dilution of Precision
18	System ID	NMEA 4.11+, optional, just before checksum: `1` GPS L1C/A L2CL L2CM, `2` GLONASS L1 OF L2 OF, `3` Galileo E1C E1B E5 bl E5 bQ, `4` BeiDou B1I D1 B1I D2 B2I D1 B2I D12
19	Checksum	`*hh`

NMEA 4.1+ systems (e.g., u-blox 9, Quectel LCD79) may emit the extra System ID field before the checksum.

Example

$GNGSA,A,3,80,71,73,79,69,,,,,,,,1.83,1.09,1.47*17

MTW — Mean Temperature of Water¶

Reports the mean water temperature.

Sentence format

        1   2 3
        |   | |
$--MTW,x.x,C*hh<CR><LF>

Field definitions¶

#	Field	Description
1	Temperature	Degrees
2	Unit of measurement	`C` = Celsius
3	Checksum	`*hh`

[GLOBALSAT] lists this as "Meteorological Temperature of Water", which is probably incorrect.

Example

$INMTW,17.9,C*1B

VWR — Relative Wind Speed and Angle¶

Reports relative wind direction and speed in multiple units.

Sentence format

         1  2  3  4  5  6  7  8 9
         |  |  |  |  |  |  |  | |
$--VWR,x.x,a,x.x,N,x.x,M,x.x,K*hh<CR><LF>

Field definitions¶

#	Field	Description
1	Wind direction magnitude	Degrees
2	Wind direction	`L` = Left of bow, `R` = Right of bow
3	Speed (knots)	Numeric speed
4	`N`	Knots unit indicator
5	Speed (meters per second)	Numeric speed
6	`M`	Meters per second unit indicator
7	Speed (kilometers per hour)	Numeric speed
8	`K`	Kilometers per hour unit indicator
9	Checksum	`*hh`

ZDA — Time & Date (UTC, Day, Month, Year, Local Time Zone)¶

Reports UTC time, date, and local time zone offset.

Sentence format

        1         2  3  4    5  6  7
        |         |  |  |    |  |  |
$--ZDA,hhmmss.ss,xx,xx,xxxx,xx,xx*hh<CR><LF>

Field definitions¶

#	Field	Description
1	UTC time	Hours, minutes, seconds (may have fractional subseconds)
2	Day	`01` to `31`
3	Month	`01` to `12`
4	Year	Four digits
5	Local zone hours	`00` to `±13` (hours offset from UTC)
6	Local zone minutes	`00` to `59` (apply same sign as local hours)
7	Checksum	`*hh`

Example

$GPZDA,160012.71,11,03,2004,-1,00*7D

APB — Autopilot Sentence "B"¶

This is a fixed form of the APA sentence with some ambiguities removed.

Note: Some autopilots (Robertson in particular) misinterpret "bearing from origin to destination" as "bearing from present position to destination".
This is likely due to the difference between the APB and APA sentences. For the APA sentence this interpretation would be correct for the data in the same field.
APA differs from APB only in this field and also omits the last two fields where this distinction is clearly defined.
This may result in poor performance if the vessel is sufficiently off-course and the two bearings differ.

Sentence format

                  1 2 3   4 5 6 7 8   9 10   11  12|   14|
                  | | |   | | | | |   | |    |   | |   | |
$--APB,A,A,x.x,a,N,A,A,x.x,a,c--c,x.x,a,x.x,a*hh<CR><LF>

Field definitions¶

#	Field	Description
1	Status	`A` = Data valid, `V` = Loran-C Blink/SNR warning or general warning when reliable fix is unavailable
2	Status	`V` = Loran-C Cycle Lock warning flag, `A` = OK or not used
3	Cross Track Error Magnitude	Cross-track error value
4	Direction to steer	`L` = Left, `R` = Right
5	Cross Track Units	`N` = Nautical miles
6	Arrival circle status	`A` = Arrival circle entered
7	Perpendicular passed at waypoint	`A` = Perpendicular passed
8	Bearing from origin to destination	Numeric bearing
9	Bearing type	`M` = Magnetic, `T` = True
10	Destination waypoint ID	Waypoint identifier
11	Bearing from present position to destination	Numeric bearing
12	Bearing type	`M` = Magnetic, `T` = True
13	Heading to steer to destination waypoint	Numeric heading
14	Heading type	`M` = Magnetic, `T` = True
15	Checksum	`*hh`

Example

$GPAPB,A,A,0.10,R,N,V,V,011,M,DEST,011,M,011,M*82

Sent by a navigation receiver when a destination waypoint is active.

Sentence format

                                                                                                                                                                 14
                  1 2   3 4    5    6       7 8        9 10  11  12  13|
                  | |   | |    |    |       | |        | |   |   |   | |
$--RMB,A,x.x,a,c--c,c--c,llll.ll,a,yyyyy.yy,a,x.x,x.x,x.x,A*hh<CR><LF>

NMEA 2.3 and later

$--RMB,A,x.x,a,c--c,c--c,llll.ll,a,yyyyy.yy,a,x.x,x.x,x.x,A,m*hh<CR><LF>

Field definitions¶

#	Field	Description
1	Status	`A` = Active, `V` = Invalid
2	Cross Track Error	Nautical miles
3	Direction to steer	`L` = Left, `R` = Right
4	Origin waypoint ID	Waypoint identifier
5	Destination waypoint ID	Waypoint identifier
6	Destination waypoint latitude (`llll.ll`)	Latitude value
7	Latitude hemisphere	`N` = North, `S` = South
8	Destination waypoint longitude (`yyyyy.yy`)	Longitude value
9	Longitude hemisphere	`E` = East, `W` = West
10	Range to destination	Nautical miles
11	Bearing to destination	Degrees true
12	Destination closing velocity	Knots
13	Arrival status	`A` = Arrival circle entered, `V` = Not entered/passed
14	FAA mode indicator	Present in NMEA 2.3 and later
15	Checksum	`*hh`

Example

$GPRMB,A,0.66,L,003,004,4917.24,N,12309.57,W,001.3,052.5,000.5,V*0B

XDR — Transducer Measurement¶

                  1 2   3 4            n
                  | |   | |            |
 $--XDR,a,x.x,a,c--c, ..... *hh<CR><LF>

Field definitions¶

#	Field	Description
1	Transducer type	Single character identifier
2	Measurement data	Numeric value
3	Units	See table below
4	Transducer name	Free-form label

Fields 1–4 form a quadruplet and may repeat any number of times (n), each describing one sensor. The message ends with a standard checksum.

Units of measurement¶

Code	Unit
`A`	Amperes
`B`	Bars / Binary
`C`	Celsius
`D`	Degrees
`H`	Hertz
`I`	Litres/second
`K`	Kelvin / kg/m³
`M`	Metres / Cubic metres
`N`	Newton
`P`	% of full range / Pascal
`R`	RPM
`S`	Parts per thousand
`V`	Volts

Example¶

$HCXDR,A,171,D,PITCH,A,-37,D,ROLL,G,367,,MAGX,G,2420,,MAGY,G,-8984,,MAGZ*41

This sentence contains five quadruplets: pitch, roll, and three magnetic field components (X, Y, Z).

HDM — Heading, Magnetic¶

Vessel heading in degrees with respect to magnetic north produced by any device or system producing magnetic heading.

$--HDM,x.x,M*hh

Field definitions¶

#	Field	Description
1	Heading degrees	Magnetic heading value
2	`M`	Magnetic reference indicator
3	Checksum	`*hh`

XTE — Cross-Track Error, Measured¶

XTE Sentencies are formatted as:

 $--XTE,A,A,x.x,a,N*hh<CR><LF>

or, in NMEA 2.3 standard:

 $--XTE,A,A,x.x,a,N,m*hh<CR><LF>

Field definitions¶

#	Field	Description
1	Status	`A` = Valid, `V` = Loran-C Blink or SNR warning, or general warning when reliable fix is unavailable
2	Status	`V` = Loran-C Cycle Lock warning flag, `A` = Valid
3	Cross Track Error Magnitude	Cross-track error value
4	Direction to steer	`L` or `R`
5	Cross Track Units	`N` = Nautical miles
6	FAA mode indicator	NMEA 2.3 and later, optional
7	Checksum	`*hh`

Example: $GPXTE,V,V,,,N,S*43

VLW — Distance Traveled through Water¶

Sentence Structure¶

                  1   2 3   4 5   6  7  8  9
                  |   | |   | |   |  |  |  |
 $--VLW,x.x,N,x.x,N,x.x,N,x.x,N*hh<CR><LF>

Field definitions¶

#	Field	Unit	Description
1	Total cumulative water distance	nm	Total distance through water since manufacture/reset
2	Unit	—	`N` = Nautical Miles
3	Water distance since reset	nm	Distance through water since last reset
4	Unit	—	`N` = Nautical Miles
5	Total cumulative ground distance	nm	(NMEA 3.0 and above)
6	Unit	—	`N` = Nautical Miles (NMEA 3.0 and above)
7	Ground distance since reset	nm	(NMEA 3.0 and above)
8	Unit	—	`N` = Nautical Miles (NMEA 3.0 and above)
9	Checksum	—	`*hh`

Sentence Structure¶

                                                                                                                                         12
                  1 2       3 4        5 6   7   8   9   10  11|
                  | |       | |        | |   |   |   |   |   | |
 $--RMA,A,llll.ll,a,yyyyy.yy,a,x.x,x.x,x.x,x.x,x.x,a*hh<CR><LF>

Field definitions¶

#	Field	Unit	Description
1	Status	—	`A` = Valid, `V` = Invalid
2	Latitude	—	`llll.ll` format
3	Latitude direction	—	`N` = North, `S` = South
4	Longitude	—	`yyyyy.yy` format
5	Longitude direction	—	`E` = East, `W` = West
6	Time Difference A	μs	Loran-C time difference A
7	Time Difference B	μs	Loran-C time difference B
8	Speed over ground	knots	—
9	Track made good	degrees	True heading of travel
10	Magnetic variation	degrees	—
11	Variation direction	—	`E` = Easterly, `W` = Westerly
12	Checksum	—	`*hh`

GSV — Satellites in View¶

One of the sentences commonly emitted by GPS units. Describes the sky position of GPS satellites currently in view. Typically transmitted in a group of 2 or 3 sentences.

Sentence Structure¶

                  1 2 3 4 5 6 7     n
                  | | | | | | |     |
 $--GSV,x,x,x,x,x,x,x,...*hh<CR><LF>

Field definitions¶

#	Field	Range	Description
1	Total sentences	—	Total number of GSV sentences in this group
2	Sentence number	1–9	Index of this sentence within the group
3	Satellites in view	—	Total satellites in view (leading zeros sent)
4	Satellite ID / PRN	—	Satellite ID or PRN number (leading zeros sent)
5	Elevation	-90 to 90°	Elevation in degrees (leading zeros sent)
6	Azimuth	000 to 359°	Azimuth to true north in degrees (leading zeros sent)
7	SNR	00–99 dB	Signal-to-noise ratio (leading zeros sent; null if not tracking)
…	(repeat 4–7)	—	Additional satellite quadruples (fields 4–7 repeated per satellite)
n-1	Signal ID	—	(NMEA 4.11 and above)
n	Checksum	—	`*hh`

Examples¶

$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

$GLGSV,3,3,09,88,07,028*51

Notes¶

⚠️ PRN vs Satellite ID: $GNGSV uses PRN in field 4, while other $GxGSV variants use Satellite ID. Several manufacturers (Jackson Labs, Quectel, Telit, and others) implement this inconsistently.

ℹ️ Extra quadruples: Some receivers emit more than 12 satellite quadruples (more than three sentences), even though NMEA-0183 does not formally allow this — WAAS satellites are a common example.

ℹ️ Untracked satellites: Receivers may report quadruples for satellites they are not actively tracking, in which case the SNR field will be null.

ℹ️ Signal ID (NMEA 4.10+): Systems such as u-blox 9 and Quectel LC79 may include an extra Signal ID field immediately before the checksum.

NMEA 2000¶

Single-frame messages¶

Standard NMEA 2000 messages that fit in one CAN frame and can be parsed directly without transport reassembly.

Fast-packet transport¶

Multi-frame transport for payloads larger than 8 bytes. Support is currently marked as not implemented in this matrix.

PGN 127245 — Rudder¶

Reports rudder command/feedback values for a specific rudder channel.

Field definitions¶

Rudder ID — rudder instance identifier
Direction — rudder direction selector (0=none, 1=starboard, 2=port)
Angle order — signed radians, resolution 1e-4
Position — signed radians, resolution 1e-4
Reserved — protocol-reserved bits/bytes for future use

PGN 128001 — Vessel Acceleration¶

Reports vessel acceleration in vessel axes.

Field definitions¶

Sequence ID — message sequence counter
Longitudinal acceleration — m/s^2, signed, resolution 1e-2
Transverse acceleration — m/s^2, signed, resolution 1e-2
Vertical acceleration — m/s^2, signed, resolution 1e-2
Reserved — reserved byte for future use

PGN 127250 — Vessel Heading¶

Reports vessel heading and related magnetic correction values.

Field definitions¶

Sequence ID — message sequence counter
Heading — radians, resolution 1e-4
Deviation — signed radians, resolution 1e-4
Variation — signed radians, resolution 1e-4
Heading reference — true or magnetic reference selector

PGN 127251 — Rate of Turn¶

Reports vessel rate of turn.

Field definitions¶

Sequence ID — message sequence counter
Rate — angular rate in rad/s
Reserved1 — reserved byte for future use
Reserved2 — reserved byte for future use
Reserved3 — reserved byte for future use

PGN 127257 — Attitude¶

Reports vessel attitude in yaw, pitch, and roll.

Field definitions¶

Sequence ID — message sequence counter
Yaw — signed radians, resolution 1e-4
Pitch — signed radians, resolution 1e-4
Roll — signed radians, resolution 1e-4
Reserved — reserved byte for future use

PGN 128259 — Speed, Water Referenced¶

Reports water-referenced and ground-referenced vessel speed.

Field definitions¶

Sequence ID — message sequence counter
Speed water referenced — m/s, resolution 1e-2
Speed ground referenced — m/s, resolution 1e-2
Speed water referenced type — sensor/source indicator
Speed direction — direction relative to the water

PGN 130306 — Wind Data¶

Reports wind speed and wind direction with reference type.

Field definitions¶

Sequence ID — message sequence counter
Wind speed — m/s, resolution 1e-2
Wind direction — radians, resolution 1e-4
Wind reference — true/apparent wind reference selector

Protocol Support Matrix¶

NMEA 0183¶

NMEA 2000¶

Detailed Message/PGN Descriptions¶

NMEA 0183¶

GGA — Global Positioning System Fix Data¶

Field definitions¶

GLL — Geographic Position - Latitude/Longitude¶

Field definitions¶

RMC — Recommended Minimum Navigation Information¶

Field definitions¶

VTG — Track Made Good and Ground Speed¶

Field definitions¶

VHW — Water Speed and Heading¶

Field definitions¶

HDG — Heading, Deviation & Variation¶

Sentence Structure¶

Field definitions¶

DBT — Depth Below Transducer¶

Field definitions¶

DPT — Depth of Water¶

Sentence Structure¶

Field definitions¶

Example¶

Notes¶

MWV — Wind Speed and Angle¶

Field definitions¶

GSA — GPS DOP and Active Satellites¶

Field definitions¶

MTW — Mean Temperature of Water¶

Field definitions¶

VWR — Relative Wind Speed and Angle¶

Field definitions¶

ZDA — Time & Date (UTC, Day, Month, Year, Local Time Zone)¶

Field definitions¶

APB — Autopilot Sentence "B"¶

Field definitions¶

RMB — Recommended Minimum Navigation Information¶

Field definitions¶

XDR — Transducer Measurement¶

Field definitions¶

Units of measurement¶

Example¶

HDM — Heading, Magnetic¶

Field definitions¶

XTE — Cross-Track Error, Measured¶

Field definitions¶

VLW — Distance Traveled through Water¶

Sentence Structure¶

Field definitions¶

RMA — Recommended Minimum Navigation Information¶

Sentence Structure¶

Field definitions¶

GSV — Satellites in View¶

Sentence Structure¶

Field definitions¶

Examples¶

Notes¶

NMEA 2000¶

Single-frame messages¶

Fast-packet transport¶

PGN 127245 — Rudder¶

Field definitions¶

PGN 128001 — Vessel Acceleration¶

Field definitions¶

PGN 127250 — Vessel Heading¶

Field definitions¶

PGN 127251 — Rate of Turn¶

Field definitions¶

PGN 127257 — Attitude¶

Field definitions¶

PGN 128259 — Speed, Water Referenced¶

Field definitions¶

PGN 130306 — Wind Data¶

Field definitions¶