NMEA National Marine Electronics Association

The NMEA is a set of standards established by the National Marine Electronics Association with the intent to bring marine devices together.

The NMEA Standard

NMEA Logo

The NMEA corresponds to a series of communication protocols established by the National Marine Electronics Association, which owns the copyright, with the aim of identifying common standards for the exchange of information between marine devices, although its spread has made it suitable for use in other types of applications.

The most commonly used formats today are NMEA 0183 and NMEA 2000.

The NMEA 0183 has replaced the old NMEA 0180 and NMEA 0182 and the transmission is unidirectional, establishing a transmitting device called talker and one or more receivers called listener. The data transmission speed is usually 4.8 Kbps.

The NMEA 2000 is the most advanced standard, it is bidirectional and its structure is linked to a single central cable (CANbus) through which all instruments can send information, receive it and, if necessary, be powered. It is intended as a plug and play system, where each unit can be connected at any time making the system richer and at the same time simplifying the wiring. Data transmission takes place at 250 Kbps.

List of NMEA judgments

The following is a non-exhaustive list of the most used NMEA judgments, with a "free" translation into Italian. For official guidance, please refer to the NMEA website (the link is among the related items).

NMEA Judgment	Original Description	Description English	Obsolete
AAM	Waypoint Arrival Alarm	Arrival alarm at waypoint
ALM	GPS Almanac Data	GPS almanac data
APA	Autopilot Sentence?	Autopilot sentences "A"	X
APB	Autopilot Sentence?	Autopilot sentences "B"
ASD	Autopilot System Data	Autopilot system data
BEC	Bearing and Distance to Waypoint	Route and distance to waypoint
BOD	Bearing - Waypoint to Waypoint	Route waypoint to waypoint
BPI	Bearing and Distance to Point of Interest	Route and distance to a point of interest	X
BWC	Bearing and distance to Waypoint - Great Circle	Orthodromic course and distance to waypoint
BWR	Bearing and distance to Waypoint - Rhumb Line	Route and rhumb line distance to waypoint
BWW	Bearing	Route
DBK	Depth Below Keel	Depth under the keel	X
DBS	Depth Below Surface	Depth below the surface	X
DBT	Depth below transducer	Depth below the transducer
DCN	Decca Position (obsolete)	Position calculated from Decca signals
DPT	Depth	Depth
DRU	Dual Doppler Auxilary Data	Dual Doppler Auxiliary Data	X
SDC	Digital Selective Calling Information	Digital Selective Calling Information
DSE	Extended DSC	DSC Complete
ISD	DSC Transponder Initiate	Initialization of DSC call
DSR	DSC Transponder Response	Response to DSC Initialization
DTM	Datum Reference	Map reference data
FSI	Frequency Set Information	Frequency setting information
GBS	GPS Satellite Fault Detection	GPS satellite error detection
GDA	Dead Reckoning Position	Estimated recalculation position	X
GGA	Global Positioning System Fix Data	GPS position, time and position data
GLA	Loran C Positions	Position Loran C	X
GLC	Geographic Position, Loran C	Topographic map Loran C
GLL	Geographic Position Latitude/Longitude	Topographic map Latitude/Longitude
GNS	GNSS fixed data	GNSS position data
GOA	OMEGA Positions	Omega position	X
GRS	GNSS Range Residual	Residual deviation from GNSS position
GSA	GPS DOP and active satellites	Dilution of GPS accuracy and active satellites
GST	GNSS Pseudorange Error Statistics	GNSS axial error statistics
GSV	Satellites in view	Visible satellites
GTD	Geographic Location in Time Differences	Geographical position in TD measure	X
GXA	TRANSIT Positions	Contesting position TRANSIT	X
HCC	Compass Heading	Route (Direction) compass	X
HCD	Heading and Deviation	Route and diversion	X
HDG	Heading Deviation and Variation	Course deviation and variations
HDM	Magnetic Heading	Magnetic course	X
HDT	Heading True	True course	X
HSC	Heading Steering Command	Route correction command
HTC	Heading True	True Route
HVD	Magnetic Variation, Automatic	Magnetic variation, automatic	X
HVM	Magnetic Variation, Manually Set	Magnetic variation, set manually	X
IMA	Vessel Identification	Vessel Identifier	X
LCD	Loran C Signal Date	Loran C signal data
MDA	Standard Meteorological Composite	Composite Weather Standard	X
MHU	Humidity	Humidity data (relative, apparent, dew)	X
MMB	Barometer	Barometer data (bar and inch)	X
MSK	MSK Receiver Interface (for DGPS Beacon Receivers)	MSK reception interface (for DGPS)
MSS	MSK Receiver Signal Status	MSK signal reception status
MTA	Air Temperatures	Air temperature in centigrade	X
MTW	Water Temperature	Water temperature
MWH	Wave Height	Wave Height (meters and feet)	X
MWD	Wind Direction and Speed	Wind direction and speed
MWS	Wind and Sea State	Wind conditions and waves in Beaufort	X
MWV	Wind Speed and Angle	Wind speed and angle
OLN	Omega Lane Numbers	Number of Omega lines	X
OSD	Own Ship Data	Various current navigation data
RMA	Recommended Minimum Navigation Information Loran	Recommended minimum navigation information
RMB	Recommended Minimum Navigation Information GPS	Essential data for reaching a waypoint
CTMR	Recommended Minimum Navigation Information GPS	Essential navigation data (position, speed, etc.)
RNN	Routes	List of waypoints of a route	X
ROO	Waypoints in active route	Number of waypoints in the active route
ROT	Rate Of Turn	Rotation speed in degrees
RPM	Revolutions	Engine speed
RSA	Rudder Sensor Angle	Rudder bar sensor angle
RSD	RADAR System Data	Radar system data
TEN	Routes	Routes
SFI	Scanning Frequency Information	Frequency Scanning Information
SNU	Loran C SNR Status	Receiving status Loran C
STC	Time Constant	Time constant	X
STN	Multiple Data ID	Data from multiple identifiers
STR	Tracking Reference	Detection references	X
SYS	Hybrid System Configuration	Hybrid system configuration	X
TEC	TRANSIT Satellite Error Code and Doppler Count	TRANSIT satellite error code and Doppler counter
TOE	TRANSIT Satellite Predicted Elevation	Expected height of TRANSIT satellite
TGA	TRANSIT Satellite Antenna and Geoidal Heights	TRANSIT satellite antenna and geoidal height
TIF	TRANSIT Satellite Initial Flag	TRSAT satellite identifier
TLL	Target latitude and longitude	Target latitude and longitude
TRF	TRANSIT Fix Data (obsolete)	TRANSIT position data
TRP	TRANSIT Satellite Predicted Direction of Rise	Estimated direction of TRANSAT satellite appearance
TRS	TRANSIT Satellite Operating Status	TRANSIT satellite operating status
TTM	Tracked Target Message	Tracking data against a target group
VBW	Dual Ground/Water Speed	Longitudinal speed and cross with respect to the ground
VDC	Current at Selected Depth	Current at a certain depth
VDR	Set and Drift	Direction and speed of travel
VHW	Water speed and heading	Water speed and course
VLW	Distance Traveled through Water	Distance travelled on the water
VPE	Speed, Dead Reckoning Parallel to True Wind	Recalculated speed parallel to the real wind
VPW	Speed Measured Parallel to Wind	Measured speed parallel to the wind
ETA	Actual Track	Current track
VTG	Track made good and Ground speed	Course and speed with respect to the earth
VTI	Intended Track	Planned route
VWE	Wind Track Efficiency	Wind efficiency on course
VWR	Relative Wind Speed and Angle	Relative wind speed and direction
VWT	True Wind Speed and Angle	True wind speed and direction
WCV	Waypoint Closure Velocity	Speed of approach to waypoint
WDC	Distance to Waypoint Great Circle	Distance to waypoint on the great circle line
WDR	Distance to Waypoint Rhumb Line	Distance to waypoint on rhumb line
WFM	Route Following Mode	How to follow the route
WNC	Distance Waypoint to Waypoint	Distance from waypoint to waypoint
WNR	Waypoint To Waypoint Distance, Rhumb Line	Rhumb line distance from waypoint to waypoint
WPL	Waypoint Location	Waypoint position
XDR	Transducer Measurements	Transducer measurements
XTE	Cross Track Error, Measured	Off course error, Measured
XTR	Cross Track Error Dead Reckoning	Off course error, Recalculated
YWP	Water Propagation Speed	Speed of water propagation
YWS	Water Profile	Water (including chemical) characteristics
ZAA	Timer, Elapsed/Estimated	Elapsed/estimated time
ZCD	Timer	Hour
ZDA	Time and Date UTC, day, month, year and local time zone	UTC Date & Time, Day, Month, Year and Time Zone
ZDL	Time and Distance to Variable Point	Time and distance from a variable point
ZEV	Event Timer	Event timer
ZFI	Elapsed Time from Point Of Interest	Time spent from a point of interest
ZFO	UTC and Time from origin Waypoint	UTC and Time from the source waypoint
ZLZ	Time of Day	Time of day
ZPI	Arrival Time at Point Of Interest	Arrival time at point of interest
ZTA	Estimated Time Of Arrival at Waypoint	Estimated time to get to the waypoint
ZTE	Estimated Time to Even/Point Of Interest	Estimated time to event / point of interest
ZTG	UTC and Time to Destination Waypoint	UTC and time from arrival waypoint
ZTI	Estimated Time to Even/Point Of Interest	Estimated time to event / point of interest
ZWP	Arrival Time at Waypoint	Arrival time at waypoint
ZZU	Time, UTC	UTC time