http://gpsd.berlios.de/NMEA.txt This is a list of NMEA 0183 sentences with field descriptions. It is primarily intended to help people undestand GPS reports. It may originally have been redacted from the document cited as [NMEA200]; see the list of sources at the end of this document. The official NMEA standard was not consulted at any point, thus this document is not a derivative work of that standard and is not controlled by the rapacious lawyers of NMEA. It is originally from the gpsdrive distribution, but adds more information on the following topics: * Old and new forms of VTG * Units used in GGA * Vendor extensions PRWIZCH and PMGNST * FAA Mode Indicator field for RMC, RMB, VTG, GLL, BWC, XTE. * New documentation on BWC, DTM, GBS, GRS, GST, MSK, and MSS sentences. * Sentence examples merged from [GIDS] * Sentence explanations from [GIDS] and elsewhere * Corrected badly mangled GPZDA description. * Common talker IDs Many of these are only emitted by high-end maritime navigation systems. Most GPS sensors emit only RMC, GSA, GSV, GLL, and VTG. Note that the form of VTG is variable with NMEA version. In NMEA 2.3, several sentences (APB, BWC, BWR, GLL, RMA, RMB, RMC, VTG, WCV, and XTE) got a new last field carrying the signal integrity information needed by the FAA. (The values in the GGA mode field were extended to carry this information as well.) Here are the values: FAA Mode Indicator A = Autonomous mode D = Differential Mode E = Estimated (dead-reckoning) mode M = Manual Input Mode S = Simulated Mode N = Data Not Valid This field may be empty. In pre-2.3 versions it is omitted. [NTUM] says that according to the NMEA specification, it dominates the Status field -- the Status field will be set to "A" (data valid) for Mode Indicators A and D, and to "V" (data invalid) for all other values of the Mode Indicator. This is confirmed by [IEC]. Where a numeric latitude or longitude is given, the two digits immediately to the left of the decimal point are whole minutes, to the right are decimals of minutes, and the remaining digits to the left of the whole minutes are whole degrees. Eg. 4533.35 is 45 degrees and 33.35 minutes. ".35" of a minute is exactly 21 seconds. Eg. 16708.033 is 167 degrees and 8.033 minutes. ".033" of a minute is about 2 seconds. According to [UNMEA], the NMEA standard requires that a field (such as altitude, latitude, or longitude) must be left empty when the GPS has no valid data for it. However, many receivers violate this. It's common, for example, to see latitude/longitude/altitude figures filled with zeros when the GPS has no valid data. The physical-level protocol is RS232C-compatible (actually RS422), 4800bps, 8N1 or 7N2 (the latter is rare but does occur; the FV18 from San Jose Navigation uses it, for example). The data is all ASCII, the high bit is not used. It appears there is an international standard, IEC 61162-1, published in 2000, that is essentially NMEA 0183. [IEC] says "is closely aligned with NMEA 0183 version 2.30". Here are the NMEA-standard sentences. The names are listed without the "talker ID", a two-character prefix that identifies the type of the transmitting unit. By far the most common talker ID is "GP", identifying a generic GPS, but all of the following are well known: GP Global Positioning System receiver LC Loran-C receiver II Integrated Instrumentation IN Integrated Nvigation EC Electronic Chart Display & Information System (ECDIS) CD Digital Selective Calling (DSC) LC - LORAN-C is a marine navigation system run by the U.S. government, which is planning to shut it down in favor of GPS. Some non-LORAN devices emit GLL but use this talker ID for backward-compatibility reasons, so it may outlast the actual LORAN system. II - II is emitted by the NMEA interface of a widely-used line of marine-navigation electronics called the AutoHelm Seatalk system, made by Raytheon; see also [SEATALK]. IN -- Some Garmin GPS units use an IN talker ID. EC -- ECDIS is a specialized geographical information system intended to support professional maritime navigation. NMEA talker units meeting the ECDIS standard use this prefix. Some of these emit GLL. CD -- Modern marine VHF radios have a set of logic collectively known as Digital Selective Calling (DSC). These radios typically take data from a local position indicating device. This data is used in conjunction with a unique (FCC assigned) ID to cause your radio to broadcast your position data to others. Conversely, these radios are capable of recieving position data of other stations and emitting sentences indicating other station positions. This lets you plot the position of other vessels on a chart, for instance. There has been at least one instance of a DSC enabled radio overloading (mis-using) the LC talker prefix for this purpose. Otherwise they use the CD prefix. A vessel's nav system is likely to have both CD and some other position indicating talker on its bus(es). Until the U.S. Coast Guard terminated the Omega Navigation System in 1997, another common talker prefix was "OM" for an Omega Navigation System receiver. Here is a more complete list of talker ID prefixes. Most are not relevant to GPS systems. AG Autopilot - General AP Autopilot - Magnetic CC Computer - Programmed Calculator (outdated) CD Communications - Digital Selective Calling (DSC) CM Computer - Memory Data (outdated) CS Communications - Satellite CT Communications - Radio-Telephone (MF/HF) CV Communications - Radio-Telephone (VHF) CX Communications - Scanning Receiver DE DECCA Navigation (outdated) 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) HC Heading - Magnetic Compass HE Heading - North Seeking Gyro HN Heading - Non North Seeking Gyro II Integrated Instrumentation IN Integrated Navigation LA Loran A (outdated) LC Loran C MP Microwave Positioning System (outdated) OM OMEGA Navigation System (outdated) OS Distress Alarm System (outdated) RA RADAR and/or ARPA SD Sounder, Depth SN Electronic Positioning System, other/general SS Sounder, Scanning TI Turn Rate Indicator TR TRANSIT Navigation System VD Velocity Sensor, Doppler, other/general DM Velocity Sensor, Speed Log, Water, Magnetic VW Velocity Sensor, Speed Log, Water, Mechanical WI Weather Instruments YC Transducer - Temperature (outdated) YD Transducer - Displacement, Angular or Linear (outdated) YF Transducer - Frequency (outdated) YL Transducer - Level (outdated) YP Transducer - Pressure (outdated) YR Transducer - Flow Rate (outdated) YT Transducer - Tachometer (outdated) YV Transducer - Volume (outdated) YX Transducer ZA Timekeeper - Atomic Clock ZC Timekeeper - Chronometer ZQ Timekeeper - Quartz ZV Timekeeper - Radio Update, WWV or WWVH ------------------------------------------------------------------------------ AAM - Waypoint Arrival Alarm This sentence is generated by some units to indicate the Status of arrival (entering the arrival circle, or passing the perpendicular of the course line) at the destination waypoint. 1 2 3 4 5 6 | | | | | | $--AAM,A,A,x.x,N,c--c*hh Field Number: 1) Status, BOOLEAN, A = Arrival circle entered 2) Status, BOOLEAN, A = perpendicular passed at waypoint 3) Arrival circle radius 4) Units of radius, nautical miles 5) Waypoint ID 6) Checksum Example: GPAAM,A,A,0.10,N,WPTNME*43 WPTNME is the waypoint name. ------------------------------------------------------------------------------ ALM - GPS Almanac Data This sentence expresses orbital data for a specified GPS satellite. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | | | | | | | | | | | | | | | | $--ALM,x.x,x.x,xx,x.x,hh,hhhh,hh,hhhh,hhhh,hhhhhh,hhhhhh,hhhhhh,hhhhhh,hhh,hhh,*hh Field Number: 1) Total number of messages 2) Message Number 3) Satellite PRN number (01 to 32) 4) GPS Week Number : Date and time in GPS is computed as number of weeks from 6 January 1980 plus number of seconds into the week. 5) SV health, bits 17-24 of each almanac page 6) Eccentricity 7) Almanac Reference Time 8) Inclination Angle 9) Rate of Right Ascension 10) Root of semi-major axis 11) Argument of perigee 12) Longitude of ascension node 13) Mean anomaly 14) F0 Clock Parameter 15) F1 Clock Parameter 16) Checksum Example: $GPALM,1,1,15,1159,00,441d,4e,16be,fd5e,a10c9f,4a2da4,686e81,58cbe1,0a4,001*5B ------------------------------------------------------------------------------ APA - Autopilot Sentence "A" This sentence is sent by some GPS receivers to allow them to be used to control an autopilot unit. This sentence is commonly used by autopilots and contains navigation receiver warning flag status, cross-track-error, waypoint arrival status, initial bearing from origin waypoint to the destination, continuous bearing from present position to destination and recommended heading-to-steer to destination waypoint for the active navigation leg of the journey. 1 2 3 4 5 6 7 8 9 10 11 | | | | | | | | | | | $--APA,A,A,x.xx,L,N,A,A,xxx,M,c---c*hh Field Number: 1) Status V = LORAN-C Blink or SNR warning V = general warning flag or other navigation systems when a reliable fix is not available 2) Status V = Loran-C Cycle Lock warning flag A = OK or not used 3) Cross Track Error Magnitude 4) Direction to steer, L or R 5) Cross Track Units (Nautic miles or kilometers) 6) Status A = Arrival Circle Entered 7) Status A = Perpendicular passed at waypoint 8) Bearing origin to destination 9) M = Magnetic, T = True 10) Destination Waypoint ID 11) checksum Example: $GPAPA,A,A,0.10,R,N,V,V,011,M,DEST,011,M*82 ------------------------------------------------------------------------------ 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 sentence and the APA sentence. for the APA sentence this would be the correct thing to do for the data in the same field. APA only differs from APB in this one field and APA leaves off the last two fields where this distinction is clearly spelled out. This will result in poor performance if the boat is sufficiently off-course that the two bearings are different. 13 15 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 Field Number: 1) Status V = LORAN-C Blink or SNR warning V = general warning flag or other navigation systems when a reliable fix is not available 2) Status V = Loran-C Cycle Lock warning flag A = OK or not used 3) Cross Track Error Magnitude 4) Direction to steer, L or R 5) Cross Track Units, N = Nautical Miles 6) Status A = Arrival Circle Entered 7) Status A = Perpendicular passed at waypoint 8) Bearing origin to destination 9) M = Magnetic, T = True 10) Destination Waypoint ID 11) Bearing, present position to Destination 12) M = Magnetic, T = True 13) Heading to steer to destination waypoint 14) M = Magnetic, T = True 15) Checksum Example: $GPAPB,A,A,0.10,R,N,V,V,011,M,DEST,011,M,011,M*82 ------------------------------------------------------------------------------ BOD - Bearing - Waypoint to Waypoint 1 2 3 4 5 6 7 | | | | | | | $--BOD,x.x,T,x.x,M,c--c,c--c*hh Field Number: 1) Bearing Degrees, TRUE 2) T = True 3) Bearing Degrees, Magnetic 4) M = Magnetic 5) TO Waypoint 6) FROM Waypoint 7) Checksum Example 1: $GPBOD,099.3,T,105.6,M,POINTB,*01 Waypoint ID: "POINTB" Bearing 99.3 True, 105.6 Magnetic This sentence is transmitted in the GOTO mode, without an active route on your GPS. WARNING: this is the bearing from the moment you press enter in the GOTO page to the destination waypoint and is NOT updated dynamically! To update the information, (current bearing to waypoint), you will have to press enter in the GOTO page again. Example 2: $GPBOD,097.0,T,103.2,M,POINTB,POINTA*52 This sentence is transmitted when a route is active. It contains the active leg information: origin waypoint "POINTA" and destination waypoint "POINTB", bearing between the two points 97.0 True, 103.2 Magnetic. It does NOT display the bearing from current location to destination waypoint! WARNING Again this information does not change until you are on the next leg of the route. (The bearing from POINTA to POINTB does not change during the time you are on this leg.) ------------------------------------------------------------------------------ BWC - Bearing & Distance to Waypoint - Geat Circle 12 1 2 3 4 5 6 7 8 9 10 11| 13 14 | | | | | | | | | | | | | | $--BEC,hhmmss.ss,llll.ll,a,yyyyy.yy,a,x.x,T,x.x,M,x.x,N,c--c,m,*hh Field Number: 1) UTCTime 2) Waypoint Latitude 3) N = North, S = South 4) Waypoint Longitude 5) E = East, W = West 6) Bearing, True 7) T = True 8) Bearing, Magnetic 9) M = Magnetic 10) Nautical Miles 11) N = Nautical Miles 12) Waypoint ID 13) FAA mode indicator (NMEA 2.3 and later, optional) 14) Checksum Example 1: $GPBWC,081837,,,,,,T,,M,,N,*13 Example 2: GPBWC,220516,5130.02,N,00046.34,W,213.8,T,218.0,M,0004.6,N,EGLM*11 ------------------------------------------------------------------------------ BWC - Bearing and Distance to Waypoint - Great Circle 1 2 3 4 5 6 7 8 9 10 11 12 13 | | | | | | | | | | | | | $--BWC,hhmmss.ss,llll.ll,a,yyyyy.yy,a,x.x,T,x.x,M,x.x,N,nnn,*hh Field number: 1) UTC time of fix 2) Latitude of waypoint 3) N or S 4) Longitude of waypoint 5) W or E 6) Bearing to waypoint, degrees true 7) T indicating true bearing 8) Bearing to waypoint, degrees magnetic 9) M indicating magnetic 10) Distance to waypoint, Nautical miles 11) N indicating nautical miles 12) Waypoint ID 13) Checksum Example 1: $GPBWC,225444,4917.24,N,12309.57,W,051.9,T,031.6,M,001.3,N,004*29 Example 2: $GPBWC,220516,5130.02,N,00046.34,W,213.8,T,218.0,M,0004.6,N,EGLM*11 ------------------------------------------------------------------------------ BWR - Bearing and Distance to Waypoint - Rhumb Line 11 1 2 3 4 5 6 7 8 9 10 | 12 13 | | | | | | | | | | | | | $--BWR,hhmmss.ss,llll.ll,a,yyyyy.yy,a,x.x,T,x.x,M,x.x,N,c--c*hh Field Number: 1) UTCTime 2) Waypoint Latitude 3) N = North, S = South 4) Waypoint Longitude 5) E = East, W = West 6) Bearing, True 7) T = True 8) Bearing, Magnetic 9) M = Magnetic 10) Nautical Miles 11) N = Nautical Miles 12) Waypoint ID 13) Checksum ------------------------------------------------------------------------------ BWW - Bearing - Waypoint to Waypoint 1 2 3 4 5 6 7 | | | | | | | $--BWW,x.x,T,x.x,M,c--c,c--c*hh Field Number: 1) Bearing Degrees, TRUE 2) T = True 3) Bearing Degrees, Magnetic 4) M = Magnetic 5) TO Waypoint 6) FROM Waypoint 7) Checksum ------------------------------------------------------------------------------ DBK - Depth Below Keel 1 2 3 4 5 6 7 | | | | | | | $--DBK,x.x,f,x.x,M,x.x,F*hh Field Number: 1) Depth, feet 2) f = feet 3) Depth, meters 4) M = meters 5) Depth, Fathoms 6) F = Fathoms 7) Checksum ------------------------------------------------------------------------------ DBS - Depth Below Surface 1 2 3 4 5 6 7 | | | | | | | $--DBS,x.x,f,x.x,M,x.x,F*hh Field Number: 1) Depth, feet 2) f = feet 3) Depth, meters 4) M = meters 5) Depth, Fathoms 6) F = Fathoms 7) Checksum ------------------------------------------------------------------------------ DBT - Depth below transducer 1 2 3 4 5 6 7 | | | | | | | $--DBT,x.x,f,x.x,M,x.x,F*hh Field Number: 1) Depth, feet 2) f = feet 3) Depth, meters 4) M = meters 5) Depth, Fathoms 6) F = Fathoms 7) Checksum ------------------------------------------------------------------------------ DCN - Decca Position 11 13 16 1 2 3 4 5 6 7 8 9 10| 12| 14 15| 17 | | | | | | | | | | | | | | | | | $--DCN,xx,cc,x.x,A,cc,x.x,A,cc,x.x,A,A,A,A,x.x,N,x*hh Field Number: 1) Decca chain identifier 2) Red Zone Identifier 3) Red Line Of Position 4) Red Master Line Status 5) Green Zone Identifier 6) Green Line Of Position 7) Green Master Line Status 8) Purple Zone Identifier 9) Purple Line Of Position 10) Purple Master Line Status 11) Red Line Navigation Use 12) Green Line Navigation Use 13) Purple Line Navigation Use 14) Position Uncertainity 15) N = Nautical Miles 16) Fix Data Basis 1 = Normal Pattern 2 = Lane Identification Pattern 3 = Lane Identification Transmissions 17) Checksum (The DCN sentence is obsolete as of 3.01) ------------------------------------------------------------------------------ DPT - Heading - Deviation & Variation 1 2 3 | | | $--DPT,x.x,x.x*hh Field Number: 1) Depth, meters 2) Offset from transducer, positive means distance from tansducer to water line negative means distance from transducer to keel 3) Checksum ------------------------------------------------------------------------------ DTM - Datum Reference 1 2 3 4 5 6 7 8 9 | | | | | | | | | $ --DTM,ref,x,llll,c,llll,c,aaa,ref*hh Field Number: 1) Local datum code. 2) Local datum subcode. May be blank. 3) Latitude offset (minutes) 4) N or S 5) Longitude offset (minutes) 6) E or W 7) Altitude offset in meters 8) Datum name. What's usually seen here is "W84", the standard WGS84 datum used by GPS. 9) Checksum. ------------------------------------------------------------------------------ FSI - Frequency Set Information 1 2 3 4 5 | | | | | $--FSI,xxxxxx,xxxxxx,c,x*hh Field Number: 1) Transmitting Frequency 2) Receiving Frequency 3) Communications Mode (NMEA Syntax 2) 4) Power Level 5) Checksum ------------------------------------------------------------------------------ GBS - GPS Satellite Fault Detection 1 2 3 4 5 6 7 8 9 | | | | | | | | | $--GBS,hhmmss.ss,x.x,x.x,x.x,x.x,x.x,x.x,x.x*hh Field Number: 1) UTC time of the GGA or GNS fix associated with this sentence 2) Expected error in latitude (meters) 3) Expected error in longitude (meters) 4) Expected error in altitude (meters) 5) PRN of most likely failed satellite 6) Probability of misse detection for most likely failed satellite 7) Estimate of bias in meters on most likely failed satellite 8) Standard deviation of bias estimate 9) Checksum Note: Source [MX521] describes a proprietary extension of GBS with a 9th data field. 11 ------------------------------------------------------------------------------ GGA - Global Positioning System Fix Data Time, Position and fix related data for a GPS receiver. 1 2 3 4 5 6 7 8 9 10 | 12 13 14 15 | | | | | | | | | | | | | | | $--GGA,hhmmss.ss,llll.ll,a,yyyyy.yy,a,x,xx,x.x,x.x,M,x.x,M,x.x,xxxx*hh Field Number: 1) Universal Time Coordinated (UTC) 2) Latitude 3) N or S (North or South) 4) Longitude 5) E or W (East or West) 6) GPS Quality Indicator, 0 - fix not available, 1 - GPS fix, 2 - Differential GPS fix (values above 2 are 2.3 features) 3 = PPS fix 4 = Real Time Kinematic 5 = Float RTK 6 = estimated (dead reckoning) 7 = Manual input mode 8 = Simulation mode 7) Number of satellites in view, 00 - 12 8) Horizontal Dilution of precision (meters) 9) Antenna Altitude above/below mean-sea-level (geoid) (in meters) 10) Units of antenna altitude, meters 11) Geoidal separation, the difference between the WGS-84 earth ellipsoid and mean-sea-level (geoid), "-" means mean-sea-level below ellipsoid 12) Units of geoidal separation, meters 13) Age of differential GPS data, time in seconds since last SC104 type 1 or 9 update, null field when DGPS is not used 14) Differential reference station ID, 0000-1023 15) Checksum ------------------------------------------------------------------------------ GLC - Geographic Position, Loran-C 12 14 1 2 3 4 5 6 7 8 9 10 11| 13| | | | | | | | | | | | | | | $--GLC,xxxx,x.x,a,x.x,a,x.x,a.x,x,a,x.x,a,x.x,a*hh Field Number: 1) GRI Microseconds/10 2) Master TOA Microseconds 3) Master TOA Signal Status 4) Time Difference 1 Microseconds 5) Time Difference 1 Signal Status 6) Time Difference 2 Microseconds 7) Time Difference 2 Signal Status 8) Time Difference 3 Microseconds 9) Time Difference 3 Signal Status 10) Time Difference 4 Microseconds 11) Time Difference 4 Signal Status 12) Time Difference 5 Microseconds 13) Time Difference 5 Signal Status 14) Checksum ------------------------------------------------------------------------------ GLL - Geographic Position - Latitude/Longitude 1 2 3 4 5 6 7 8 | | | | | | | | $--GLL,llll.ll,a,yyyyy.yy,a,hhmmss.ss,a,m,*hh Field Number: 1) Latitude 2) N or S (North or South) 3) Longitude 4) E or W (East or West) 5) Universal Time Coordinated (UTC) 6) Status A - Data Valid, V - Data Invalid 7) FAA mode indicator (NMEA 2.3 and later) 8) Checksum Introduced in NMEA 3.0. ------------------------------------------------------------------------------ GRS - GPS Range Residuals 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | | | | | | | | | | | | | | | $ --GST,hhmmss.ss,m,xx,xx,xx,xx,xx,xx,xx,xx,xx,xx,xx,xx,*hh Field Number: 1) TC time of associated GGA fix 2) 0 = Residuals used in GGA, 1 = residuals calculated after GGA 3) Satellite 1 residual in meters 4) Satellite 2 residual in meters 5) Satellite 3 residual in meters 6) Satellite 4 residual in meters (blank if unused) 7) Satellite 5 residual in meters (blank if unused) 8) Satellite 6 residual in meters (blank if unused) 9) Satellite 7 residual in meters (blank if unused) 10) Satellite 8 residual in meters (blank if unused) 11) Satellite 9 residual in meters (blank if unused) 12) Satellite 10 residual in meters (blank if unused) 13) Satellite 11 residual in meters (blank if unused) 14) Satellite 12 residual in meters (blank if unused) 15) Checksum The order of satellites the same as those in the last GSA. Example: $GPGRS,024603.00,1,-1.8,-2.7,0.3,,,,,,,,,*6C ------------------------------------------------------------------------------ GST - GPS Pseudorange Noise Statistics 1 2 3 4 5 6 7 8 9 | | | | | | | | | $ --GST,hhmmss.ss,x,x,x,x,x,x,x,*hh Field Number: 1) TC time of associated GGA fix 2) Total RMS standard deviation of ranges inputs to the navigation solution 3) Standard deviation (meters) of semi-major axis of error ellipse 4) Standard deviation (meters) of semi-minor axis of error ellipse 5) Orientation of semi-major axis of error ellipse (true north degrees) 6) Standard deviation (meters) of latitude error 7) Standard deviation (meters) of longitude error 8) Standard deviation (meters) of altitude error 9) Checksum ------------------------------------------------------------------------------ GSA - GPS DOP and active satellites 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 Field Number: 1) Selection mode 2) Mode (1 = no fix, 2 = 2D fix, 3 = 3D fix) 3) ID of 1st satellite used for fix 4) ID of 2nd satellite used for fix ... 14) ID of 12th satellite used for fix 15) PDOP 16) HDOP 17) VDOP 18) checksum Robin Darroch writes: "As I understand it, DOP is unit-less, and can only be compared meaningfully to other DOP figures. A DOP of 4 indicates twice the likelihood of a given position error compared with a DOP of 2. The DOP is calculated from the expected errors due to current geometry of the satellites used to obtain the fix. The estimated position errors should show a strong correlation with DOP, but be completely different in value as they are measured in distance units (i.e. metres), and they are trying to tell you "you're very probably within x metres of this point" rather than "I'm about twice as sure of my position as I was a couple of minutes ago". ------------------------------------------------------------------------------ GSV - Satellites in view These sentences describe the sky position of a UPS satellite in view. Typically they're shipped in a group of 2 or 3. 1 2 3 4 5 6 7 n | | | | | | | | $--GSV,x,x,x,x,x,x,x,...*hh Field Number: 1) total number of messages 2) message number 3) satellites in view 4) satellite number 5) elevation in degrees (0-90) 6) azimuth in degrees to true north (0-359) 7) SNR in dB (0-99) more satellite infos like 4)-7) n) checksum Example: $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 ------------------------------------------------------------------------------ GTD - Geographic Location in Time Differences 1 2 3 4 5 6 | | | | | | $--GTD,x.x,x.x,x.x,x.x,x.x*hh Field Number: 1) time difference 2) time difference 3) time difference 4) time difference 5) time difference n) checksum ------------------------------------------------------------------------------ GXA - TRANSIT Position - Latitude/Longitude Location and time of TRANSIT fix at waypoint 1 2 3 4 5 6 7 8 | | | | | | | | $--GXA,hhmmss.ss,llll.ll,a,yyyyy.yy,a,c--c,X*hh Field Number: 1) UTC of position fix 2) Latitude 3) East or West 4) Longitude 5) North or South 6) Waypoint ID 7) Satelite number 8) Checksum (The GXA sentence is obsolete as of 3.01.) ------------------------------------------------------------------------------ HDG - Heading - Deviation & Variation 1 2 3 4 5 6 | | | | | | $--HDG,x.x,x.x,a,x.x,a*hh Field Number: 1) Magnetic Sensor heading in degrees 2) Magnetic Deviation, degrees 3) Magnetic Deviation direction, E = Easterly, W = Westerly 4) Magnetic Variation degrees 5) Magnetic Variation direction, E = Easterly, W = Westerly 6) Checksum ------------------------------------------------------------------------------ HDM - Heading - Magnetic Vessel heading in degrees with respect to magnetic north produced by any device or system producing magnetic heading. 1 2 3 | | | $--HDM,x.x,M*hh Field Number: 1) Heading Degrees, magnetic 2) M = magnetic 3) Checksum ------------------------------------------------------------------------------ HDT - Heading - True Actual vessel heading in degrees true produced by any device or system producing true heading. 1 2 3 | | | $--HDT,x.x,T*hh Field Number: 1) Heading Degrees, true 2) T = True 3) Checksum ------------------------------------------------------------------------------ HSC - Heading Steering Command 1 2 3 4 5 | | | | | $--HSC,x.x,T,x.x,M,*hh Field Number: 1) Heading Degrees, True 2) T = True 3) Heading Degrees, Magnetic 4) M = Magnetic 5) Checksum ------------------------------------------------------------------------------ LCD - Loran-C Signal Data 1 2 3 4 5 6 7 8 9 10 11 12 13 14 | | | | | | | | | | | | | | $--LCD,xxxx,xxx,xxx,xxx,xxx,xxx,xxx,xxx,xxx,xxx,xxx,xxx,xxx*hh Field Number: 1) GRI Microseconds/10 2) Master Relative SNR 3) Master Relative ECD 4) Time Difference 1 Microseconds 5) Time Difference 1 Signal Status 6) Time Difference 2 Microseconds 7) Time Difference 2 Signal Status 8) Time Difference 3 Microseconds 9) Time Difference 3 Signal Status 10) Time Difference 4 Microseconds 11) Time Difference 4 Signal Status 12) Time Difference 5 Microseconds 13) Time Difference 5 Signal Status 14) Checksum ------------------------------------------------------------------------------ MSK - Control for a Beacon Receiver 1 2 3 4 5 6 | | | | | | $--MSK,nnn,m,nnn,m,nnn*hh Field Number: 1) Frequency to use 2) Frequency mode, A=auto, M=manual 3) Beacon bit rate 4) Bitrate, A=auto, M=manual 5) Frequency for MSS message status (null for no status) 6) Checksum ------------------------------------------------------------------------------ MSS - Beacon Receiver Status 1 2 3 4 5 6 | | | | | | $--MSS,nn,nn,fff,bbb,xxx*hh Field Number: 1) Signal strength (dB 1uV) 2) Signal to noise ratio (dB) 3) Beacon frequency (kHz) 4) Beacon data rate (BPS) 5) Unknown integer value 6) Checksum ------------------------------------------------------------------------------ MTW - Water Temperature 1 2 3 | | | $--MTW,x.x,C*hh Field Number: 1) Degrees 2) Unit of Measurement, Celcius 3) Checksum ------------------------------------------------------------------------------ MWV - Wind Speed and Angle 1 2 3 4 5 | | | | | $--MWV,x.x,a,x.x,a*hh Field Number: 1) Wind Angle, 0 to 360 degrees 2) Reference, R = Relative, T = True 3) Wind Speed 4) Wind Speed Units, K/M/N 5) Status, A = Data Valid 6) Checksum ------------------------------------------------------------------------------ OLN - Omega Lane Numbers 1 2 3 4 |--------+ |--------+ |--------+ | $--OLN,aa,xxx,xxx,aa,xxx,xxx,aa,xxx,xxx*hh Field Number: 1) Omega Pair 1 2) Omega Pair 1 3) Omega Pair 1 4) Checksum (The OLN sentence is obsolete as of 2.30) ------------------------------------------------------------------------------ OSD - Own Ship Data 1 2 3 4 5 6 7 8 9 10 | | | | | | | | | | $--OSD,x.x,A,x.x,a,x.x,a,x.x,x.x,a*hh Field Number: 1) Heading, degrees true 2) Status, A = Data Valid 3) Vessel Course, degrees True 4) Course Reference 5) Vessel Speed 6) Speed Reference 7) Vessel Set, degrees True 8) Vessel drift (speed) 9) Speed Units 10) Checksum ------------------------------------------------------------------------------ R00 - Waypoints in active route 1 n | | $--R00,c---c,c---c,....*hh Field Number: 1) waypoint ID ... n) checksum ------------------------------------------------------------------------------ RMA - Recommended Minimum Navigation Information 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 Field Number: 1) Blink Warning 2) Latitude 3) N or S 4) Longitude 5) E or W 6) Time Difference A, uS 7) Time Difference B, uS 8) Speed Over Ground, Knots 9) Track Made Good, degrees true 10) Magnetic Variation, degrees 11) E or W 12) Checksum ------------------------------------------------------------------------------ RMB - Recommended Minimum Navigation Information To be sent by a navigation receiver when a destination waypoint is active. 14 1 2 3 4 5 6 7 8 9 10 11 12 13| 15 | | | | | | | | | | | | | | | $--RMB,A,x.x,a,c--c,c--c,llll.ll,a,yyyyy.yy,a,x.x,x.x,x.x,A,m,*hh Field Number: 1) Status, A= Active, V = Void 2) Cross Track error - nautical miles 3) Direction to Steer, Left or Right 4) TO Waypoint ID 5) FROM Waypoint ID 6) Destination Waypoint Latitude 7) N or S 8) Destination Waypoint Longitude 9) E or W 10) Range to destination in nautical miles 11) Bearing to destination in degrees True 12) Destination closing velocity in knots 13) Arrival Status, A = Arrival Circle Entered 14) FAA mode indicator (NMEA 2.3 and later) 15) Checksum Example: $GPRMB,A,0.66,L,003,004,4917.24,N,12309.57,W,001.3,052.5,000.5,V*0B ------------------------------------------------------------------------------ RMC - Recommended Minimum Navigation Information 12 1 2 3 4 5 6 7 8 9 10 11| 13 | | | | | | | | | | | | | $--RMC,hhmmss.ss,A,llll.ll,a,yyyyy.yy,a,x.x,x.x,xxxx,x.x,a,m,*hh Field Number: 1) UTC Time 2) Status, V=Navigation receiver warning A=Valid 3) Latitude 4) N or S 5) Longitude 6) E or W 7) Speed over ground, knots 8) Track made good, degrees true 9) Date, ddmmyy 10) Magnetic Variation, degrees 11) E or W 12) FAA mode indicator (NMEA 2.3 and later) 13) Checksum 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. ------------------------------------------------------------------------------ ROT - Rate Of Turn 1 2 3 | | | $--ROT,x.x,A*hh Field Number: 1) Rate Of Turn, degrees per minute, "-" means bow turns to port 2) Status, A means data is valid 3) Checksum ------------------------------------------------------------------------------ RPM - Revolutions 1 2 3 4 5 6 | | | | | | $--RPM,a,x,x.x,x.x,A*hh Field Number: 1) Sourse, S = Shaft, E = Engine 2) Engine or shaft number 3) Speed, Revolutions per minute 4) Propeller pitch, % of maximum, "-" means astern 5) Status, A means data is valid 6) Checksum ------------------------------------------------------------------------------ RSA - Rudder Sensor Angle 1 2 3 4 5 | | | | | $--RSA,x.x,A,x.x,A*hh Field Number: 1) Starboard (or single) rudder sensor, "-" means Turn To Port 2) Status, A means data is valid 3) Port rudder sensor 4) Status, A means data is valid 5) Checksum ------------------------------------------------------------------------------ RSD - RADAR System Data 14 1 2 3 4 5 6 7 8 9 10 11 12 13| | | | | | | | | | | | | | | $--RSD,x.x,x.x,x.x,x.x,x.x,x.x,x.x,x.x,x.x,x.x,x.x,a,a*hh Field Number: 9) Cursor Range From Own Ship 10) Cursor Bearing Degrees Clockwise From Zero 11) Range Scale 12) Range Units 14) Checksum ------------------------------------------------------------------------------ RTE - Routes 1 2 3 4 5 x n | | | | | | | $--RTE,x.x,x.x,a,c--c,c--c, ..... c--c*hh Field Number: 1) Total number of messages being transmitted 2) Message Number 3) Message mode c = complete route, all waypoints w = working route, the waypoint you just left, the waypoint you're heading to then all the rest 4) Waypoint ID x) More Waypoints n) Checksum The Garmin 65 and possibly other units report a $GPR00 in the same format. ------------------------------------------------------------------------------ SFI - Scanning Frequency Information 1 2 3 4 x | | | | | $--SFI,x.x,x.x,xxxxxx,c .......... xxxxxx,c*hh Field Number: 1) Total Number Of Messages 2) Message Number 3) Frequency 1 4) Mode 1 x) Checksum ------------------------------------------------------------------------------ STN - Multiple Data ID This sentence is transmitted before each individual sentence where there is a need for the Listener to determine the exact source of data in the system. Examples might include dual-frequency depthsounding equipment or equipment that integrates data from a number of sources and produces a single output. 1 2 | | $--STN,x.x,*hh Field Number: 1) Talker ID Number 2) Checksum ------------------------------------------------------------------------------ TRF - TRANSIT Fix Data 13 1 2 3 4 5 6 7 8 9 10 11 12| | | | | | | | | | | | | | $--TRF,hhmmss.ss,xxxxxx,llll.ll,a,yyyyy.yy,a,x.x,x.x,x.x,x.x,xxx,A*hh Field Number: 1) UTC Time 2) Date, ddmmyy 3) Latitude 4) N or S 5) Longitude 6) E or W 7) Elevation Angle 8) Number of iterations 9) Number of Doppler intervals 10) Update distance, nautical miles 11) Satellite ID 12) Data Validity 13) Checksum (The TRF sentence is obsolete as of 2.3.0) ------------------------------------------------------------------------------ TTM - Tracked Target Message 11 13 1 2 3 4 5 6 7 8 9 10| 12| 14 | | | | | | | | | | | | | | $--TTM,xx,x.x,x.x,a,x.x,x.x,a,x.x,x.x,a,c--c,a,a*hh Field Number: 1) Target Number 2) Target Distance 3) Bearing from own ship 4) Bearing Units 5) Target speed 6) Target Course 7) Course Units 8) Distance of closest-point-of-approach 9) Time until closest-point-of-approach "-" means increasing 10) "-" means increasing 11) Target name 12) Target Status 13) Reference Target 14) Checksum ------------------------------------------------------------------------------ VBW - Dual Ground/Water Speed 1 2 3 4 5 6 7 | | | | | | | $--VBW,x.x,x.x,A,x.x,x.x,A*hh Field Number: 1) Longitudinal water speed, "-" means astern 2) Transverse water speed, "-" means port 3) Status, A = Data Valid 4) Longitudinal ground speed, "-" means astern 5) Transverse ground speed, "-" means port 6) Status, A = Data Valid 7) Checksum ------------------------------------------------------------------------------ VDR - Set and Drift 1 2 3 4 5 6 7 | | | | | | | $--VDR,x.x,T,x.x,M,x.x,N*hh Field Number: 1) Degress True 2) T = True 3) Degrees Magnetic 4) M = Magnetic 5) Knots (speed of current) 6) N = Knots 7) Checksum ------------------------------------------------------------------------------ VHW - Water speed and heading 1 2 3 4 5 6 7 8 9 | | | | | | | | | $--VHW,x.x,T,x.x,M,x.x,N,x.x,K*hh Field Number: 1) Degress True 2) T = True 3) Degrees Magnetic 4) M = Magnetic 5) Knots (speed of vessel relative to the water) 6) N = Knots 7) Kilometers (speed of vessel relative to the water) 8) K = Kilometers 9) Checksum ------------------------------------------------------------------------------ VLW - Distance Traveled through Water 1 2 3 4 5 | | | | | $--VLW,x.x,N,x.x,N*hh Field Number: 1) Total cumulative distance 2) N = Nautical Miles 3) Distance since Reset 4) N = Nautical Miles 5) Checksum ------------------------------------------------------------------------------ VPW - Speed - Measured Parallel to Wind 1 2 3 4 5 | | | | | $--VPW,x.x,N,x.x,M*hh Field Number: 1) Speed, "-" means downwind 2) N = Knots 3) Speed, "-" means downwind 4) M = Meters per second 5) Checksum ------------------------------------------------------------------------------ VTG - Track made good and Ground speed 1 2 3 4 5 6 7 8 9 10 | | | | | | | | | | $--VTG,x.x,T,x.x,M,x.x,N,x.x,K,m,*hh Field Number: 1) Track Degrees 2) T = True 3) Track Degrees 4) M = Magnetic 5) Speed Knots 6) N = Knots 7) Speed Kilometers Per Hour 8) K = Kilometers Per Hour 9) FAA mode indicator (NMEA 2.3 and later) 10) Checksum Note: in some older versions of NMEA 0183, the sentence looks like this: 1 2 3 4 5 | | | | | $--VTG,x.x,x,x.x,x.x,*hh Field Number: 1) True course over ground (degrees) 000 to 359 2) Magnetic course over ground 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 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. ------------------------------------------------------------------------------ VWR - Relative Wind Speed and Angle 1 2 3 4 5 6 7 8 9 | | | | | | | | | $--VWR,x.x,a,x.x,N,x.x,M,x.x,K*hh Field Number: 1) Wind direction magnitude in degrees 2) Wind direction Left/Right of bow 3) Speed 4) N = Knots 5) Speed 6) M = Meters Per Second 7) Speed 8) K = Kilometers Per Hour 9) Checksum ------------------------------------------------------------------------------ WCV - Waypoint Closure Velocity 1 2 3 4 | | | | $--WCV,x.x,N,c--c*hh Field Number: 1) Velocity 2) N = knots 3) Waypoint ID 4) Checksum ------------------------------------------------------------------------------ WNC - Distance - Waypoint to Waypoint 1 2 3 4 5 6 7 | | | | | | | $--WNC,x.x,N,x.x,K,c--c,c--c*hh Field Number: 1) Distance, Nautical Miles 2) N = Nautical Miles 3) Distance, Kilometers 4) K = Kilometers 5) TO Waypoint 6) FROM Waypoint 7) Checksum ------------------------------------------------------------------------------ WPL - Waypoint Location 1 2 3 4 5 6 | | | | | | $--WPL,llll.ll,a,yyyyy.yy,a,c--c*hh Field Number: 1) Latitude 2) N or S (North or South) 3) Longitude 4) E or W (East or West) 5) Waypoint name 6) Checksum ------------------------------------------------------------------------------ XDR - Cross Track Error - Dead Reckoning 1 2 3 4 n | | | | | $--XDR,a,x.x,a,c--c, ..... *hh Field Number: 1) Transducer Type 2) Measurement Data 3) Units of measurement 4) Name of transducer x) More of the same n) Checksum ------------------------------------------------------------------------------ XTE - Cross-Track Error, Measured 1 2 3 4 5 6 7 | | | | | | | $--XTE,A,A,x.x,a,N,m,*hh Field Number: 1) Status V = LORAN-C Blink or SNR warning V = general warning flag or other navigation systems when a reliable fix is not available 2) Status V = Loran-C Cycle Lock warning flag A = OK or not used 3) Cross Track Error Magnitude 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 ------------------------------------------------------------------------------ XTR - Cross Track Error - Dead Reckoning 1 2 3 4 | | | | $--XTR,x.x,a,N*hh Field Number: 1) Magnitude of cross track error 2) Direction to steer, L or R 3) Units, N = Nautical Miles 4) Checksum ------------------------------------------------------------------------------ ZDA - Time & Date - UTC, day, month, year and local time zone 1 2 3 4 5 6 7 | | | | | | | $--ZDA,hhmmss.ss,xx,xx,xxxx,xx,xx*hh Field Number: 1) UTC time (hours, minutes, seconds, may have fractional subsecond) 2) Day, 01 to 31 3) Month, 01 to 12 4) Year (4 digits) 5) Local zone description, 00 to +- 13 hours 6) Local zone minutes description, apply same sign as local hours 7) Checksum Example: $GPZDA,160012.71,11,03,2004,-1,00*7D ------------------------------------------------------------------------------ ZFO - UTC & Time from origin Waypoint 1 2 3 4 | | | | $--ZFO,hhmmss.ss,hhmmss.ss,c--c*hh Field Number: 1) Universal Time Coordinated (UTC) 2) Elapsed Time 3) Origin Waypoint ID 4) Checksum ------------------------------------------------------------------------------ ZTG - UTC & Time to Destination Waypoint 1 2 3 4 | | | | $--ZTG,hhmmss.ss,hhmmss.ss,c--c*hh Field Number: 1) Universal Time Coordinated (UTC) 2) Time Remaining 3) Destination Waypoint ID 4) Checksum ------------------------------------------------------------------------------ **************************************************************** Found on the web: (data fields unknown) ASD - Autopilot System Data DSC - Digital Selective Calling Information DSE - Extended DSC DSI - DSC Transponder Initiate DSR - DSC Transponder Response MWD - Wind Direction & Speed TLL - Target Latitude and Longitude WDR - Distance to Waypoint - Rhumb Line WDC - Distance to Waypoint - Great Circle ZDL - Time and Distance to Variable Point **************************************************************** Vendor extensions (this list is very incomplete): Garmin Estimated Error 1 2 3 4 5 6 7 | | | | | | | $PGRME,hhh,M,vvv,M,ttt,M*hh Field Number: 1) Estimated horizontal position error (HPE), 2) M=meters 3) Estimated vertical position error (VPE) 4) M=meters 5) Overall spherical equivalent position error 6) M=meters 7) Checksum Example: $PGRME,15.0,M,45.0,M,25.0,M*22 ------------------------------------------------------------------------------ Magellan Status 1 2 3 4 5 6 7 8 | | | | | | | | $PMGNST,xx.xx,m,t,nnn,xx.xx,nnn,nn,c Field Number: 1) Firmware version number? 2) Mode (1 = no fix, 2 = 2D fix, 3 = 3D fix) 3) T if we have a fix 4) numbers change - unknown 5) time left on the GPS battery in hours 6) numbers change (freq. compensation?) 7) PRN number receiving current focus 8) nmea_checksum Only supported on Magellan GPSes. ------------------------------------------------------------------------------ $PRWIZCH,n,s,n,s,n,s,n,s,n,s,n,s,n,s,n,s,n,s,n,s,n,s,n,s,c*hh Fields consist of 12 pairs of a satellite PRN followed by a signal quality number in the range 0-7 (0 worst, 7 best). Only emitted by the Zodiac (Rockwell) chipset. ------------------------------------------------------------------------------ Sources: [NMEA2000] The NMEA 0183 protocol http://nmeatool.nmea2000.de/download/0183.pdf Probably the origin of this document. [DEPRIEST] "NMEA data" http://www.gpsinformation.org/dale/nmea.htm Used for PMGNST and the FAA mode code. [MX521] "MX521 GPS/DGPS Sensor Installation Manual" http://www.mx-marine.com/downloads/MX521_Install_manual_051804.pdf Used for GBS, GRS. [ZODIAC] "Zodiac Serial Data Interface Specification" http://users.rcn.com/mardor/serial.pdf Used for PRWIZCH. [GH79L4N] "Specifications for GPS Receiver GH-79L4-N" http://www.tecsys.de/db/gps/gh79l1an_intant.pdf Used for GPDTM. [GIDS] "GPS - NMEA sentence information" http://aprs.gids.nl/nmea/ Used for BWC, MSK, MSS. [NMEAFAQ] "The NMEA FAQ" http://vancouver-webpages.com/peter/nmeafaq.txt Used for R00. [UNMEA] "Understanding NMEA 0183" http://pcptpp030.psychologie.uni-regensburg.de/trafficresearch/NMEA0183/ Source for the claim that NMEA requires undefined data fields to be empty. [NTUM] "NemaTalker User Manual" http://www.sailsoft.nl/NemaTalker/UserManual/InstrGPS.htm Source for the claim that Mode Indicator dominates Status. [IEC] "International Standard IEC 61162-1" (preview) http://domino.iec.ch/preview/info_iec61162-1%7Bed2.0%7Den.pdf [SEATALK] "SeaTalk Technical Reference" http://www.thomasknauf.de/seatalk.htm