Nmea

NMEA

Talker Identifiers

AG Autopilot - General
AP Autopilot - Magnetic

CD Communications – Digital Selective Calling(DSC)
CR Communications – Receiver / Beacon Receiver
CS Communications – Satellite
CT Communications – Radio-Telephone (MF/HF)
CV Communications – Radio-Telephone (VHF)
CX Communications – Scanning Receiver

DF Direction Finder

EC Electronic Chart Display & Information System (ECDIS)
EP Emergency Position Indicating Beacon (EPIRB)
ER Engine Room Monitoring Systems

GP Global Positioning System (GPS)
GL GLONASS Receiver 
GN Global Navigation Satellite System (GNSS) 

HC Heading – Magnetic Compass
HE Heading – North Seeking Gyro
HN Heading – Non North Seeking Gyro

II Integrated Instrumentation
IN Integrated Navigation

LC Loran C

P Proprietary Code

RA RADAR and/or ARPA

SD Sounder, Depth
SN Electronic Positioning System, other/general
SS Sounder, Scanning

TI Turn Rate Indicator

VD Velocity Sensor, Doppler, other/general
DM Velocity Sensor, Speed Log, Water, Magnetic
VW Velocity Sensor, Speed Log, Water, Mechanical
WI Weather Instruments 

YX Transducer

ZA Timekeeper – Atomic Clock
ZC Timekeeper – Chronometer
ZQ Timekeeper – Quartz
ZV Timekeeper – Radio Update, WWV or WWVH

Sentence Identifiers

AAM Waypoint Arrival Alarm
ABK UAIS Addressed and binary broadcast acknowledgement
ACA UAIS Regional Channel Assignment Message
ACS UAIS Channel management information Source
AIR UAIS Interrogation Request
ALM GPS Almanac Data
ALR Set Alarm State
APB Heading/Track Controller (Autopilot) Sentence “B”
BEC Bearing and Distance to Waypoint – Dead Reckoning
BOD Bearing – Origin to Destination
BWC Bearing and Distance to Waypoint
BWR Bearing and Distance to Waypoint – Rhumb Line
BWW Bearing – Waypoint to Waypoint
CUR Water Current Layer
DBT Depth Below Transducer
DCN Decca Position
DPT Depth
DSC Digital Selective Calling Information
DSE Expanded Digital Selective Calling
DSI DSC Transponder Initialize
DSR DCS Transponder Response
DTM Datum Reference
FSI Frequency Set Information
GBS GNSS Satellite Fault Detection
GGA Global Positioning System Fix Data
GLC Geographic Position – Loran C
GLL Geographic Position – Latitude/Longitude
GMP GNSS Map Projection Fix Data
GNS GNSS Fix Data
GRS GNSS Range Residues
GSA GNSS DOP and Active Satellites
GST GNSS Pseudo range Error Statistics
GSV GNSS Satellites in View
HDG Heading, Deviation and Variation
HDT Heading, True
HMR Heading Monitor Receive
HMS Heading Monitor Set
HSC Heading Steering Command
HTC Heading/Track Control Command
HTD Heading/Track Control Data
LCD Loran-C Signal Data
LRF UAIS Long-Range Function
LTI UAIS Long-Range Interrogation
LR1 UAIS Long-Range Reply Sentence 1
LR2 UAIS Long-Range Reply Sentence 2
LR3 UAIS Long-Range Reply Sentence 3
MLA GLONASS Almanac Data
MSK MSK Receiver Interface
MSS MSK Receiver Signal
MTW Water Temperature
MWD Wind Direction and Speed
MWV Wind speed and Angle
OSD Own Ship Data
RMA Recommended Minimum Specific Loran-C Data
RMB Recommended Minimum Navigation Information
RMC Recommended Minimum Specific GNSS Data
ROT Rate of Turn
RPM Revolutions
RSA Rudder Sensor Angle
RSD Radar System Data
RTE Routes RTE – Routes
SFI Scanning Frequency Information
SSD UAIS Ship Static Data
STN Multiple Data ID
TLB Target Label
TLL Target Latitude and Longitude
TTM Tracked Target Message
TUT Transmission of Multi-language Text
TXT Text Transmission
VBW Dual Ground/Water Speed
VDR Set and Drift
VHW Water Speed and Heading
VLW Dual Ground/Water Distance
VPW Speed – Measured Parallel to Wind
VSD UAIS Voyage Static Data
VTG Course Over Ground and Ground Speed
WCV Waypoint Closure Velocity
WNC Distance – Waypoint to Waypoint
WPL Waypoint Location
XDR Transducer Measurements
XTE Cross-Track Error, Measured
XTR Cross-Track Error – Dead Reckoning
ZDA Time and Date
ZDL Time and Distance to Variable Point
ZFO UTC and Time from Origin Waypoint
ZTG UTC and Time to Destination Waypoint Encapsulation Formatters
ABM UAIS Addressed binary and safety related message
BBM UAIS Broadcast Binary Message
VDM UAIS VHF Data-link Message
VDO UAIS VHF Data-link Own-vessel report

HEROT + HEHDT -> HEHRC

$HEROT,xxx.xx,A*XX
$HEHDT,yyy.yy,T*XX (deg/min) 
->$HEHRCaaaaa,bbb*XX
aaaaa – yyy.yy, bbb – x.xx (deg/s)