Glenn Baddeley - GPS - NMEA sentence information Contents All $GPxxx sentence codes and short descriptions 26 interpreted sentences transmitted by GPS unit 12 interpreted Garmin proprietary sentences transmitted by GPS unit 8 interpreted Garmin proprietary sentences received by GPS unit Format of latitudes and longitudes References [ Top ] [Glenn's GPS Contents Page] All $GPxxx sentence codes and short descriptions $GPAAM - Waypoint Arrival Alarm $GPALM - GPS Almanac Data $GPAPA - Autopilot format "A" $GPAPB - Autopilot format "B" $GPASD - Autopilot System Data $GPBEC - Bearing & Distance to Waypoint, Dead Reckoning $GPBOD - Bearing, Origin to Destination $GPBWC - Bearing & Distance to Waypoint, Great Circle $GPBWR - Bearing & Distance to Waypoint, Rhumb Line $GPBWW - Bearing, Waypoint to Waypoint $GPDBT - Depth Below Transducer $GPDCN - Decca Position $GPDPT - Depth $GPFSI - Frequency Set Information $GPGGA - Global Positioning System Fix Data $GPGLC - Geographic Position, Loran-C $GPGLL - Geographic Position, Latitude/Longitude $GPGRS - GPS Range Residuals $GPGSA - GPS DOP and Active Satellites $GPGST - GPS Pseudorange Noise Statistics $GPGSV - GPS Satellites in View $GPGXA - TRANSIT Position $GPHDG - Heading, Deviation & Variation $GPHDT - Heading, True $GPHSC - Heading Steering Command $GPLCD - Loran-C Signal Data $GPMSK - Control for a Beacon Receiver $GPMSS - Beacon Receiver Status $GPMTA - Air Temperature (to be phased out) $GPMTW - Water Temperature $GPMWD - Wind Direction $GPMWV - Wind Speed and Angle $GPOLN - Omega Lane Numbers $GPOSD - Own Ship Data $GPR00 - Waypoint active route (not standard) $GPRMA - Recommended Minimum Specific Loran-C Data $GPRMB - Recommended Minimum Navigation Information $GPRMC - Recommended Minimum Specific GPS/TRANSIT Data $GPROT - Rate of Turn $GPRPM - Revolutions $GPRSA - Rudder Sensor Angle $GPRSD - RADAR System Data $GPRTE - Routes $GPSFI - Scanning Frequency Information $GPSTN - Multiple Data ID $GPTRF - Transit Fix Data $GPTTM - Tracked Target Message $GPVBW - Dual Ground/Water Speed $GPVDR - Set and Drift $GPVHW - Water Speed and Heading $GPVLW - Distance Traveled through the Water $GPVPW - Speed, Measured Parallel to Wind $GPVTG - Track Made Good and Ground Speed $GPWCV - Waypoint Closure Velocity $GPWNC - Distance, Waypoint to Waypoint $GPWPL - Waypoint Location $GPXDR - Transducer Measurements $GPXTE - Cross-Track Error, Measured $GPXTR - Cross-Track Error, Dead Reckoning $GPZDA - UTC Date / Time and Local Time Zone Offset $GPZFO - UTC & Time from Origin Waypoint $GPZTG - UTC & Time to Destination Waypoint [Top] 26 interpreted sentences transmitted by GPS unit $GPAAM - Waypoint Arrival Alarm $GPALM - GPS Almanac Data (Can also be received by GPS unit) $GPAPB - Autopilot format "B" $GPBOD - Bearing, origin to destination $GPBWC - Bearing and distance to waypoint, great circle $GPGGA - Global Positioning System Fix Data $GPGLL - Geographic position, latitude / longitude $GPGRS - GPS Range Residuals $GPGSA - GPS DOP and active satellites $GPGST - GPS Pseudorange Noise Statistics $GPGSV - GPS Satellites in view $GPHDT - Heading, True $GPMSK - Control for a Beacon Receiver $GPMSS - Beacon Receiver Status $GPR00 - List of waypoints in currently active route $GPRMA - Recommended minimum specific Loran-C data $GPRMB - Recommended minimum navigation info $GPRMC - Recommended minimum specific GPS/Transit data $GPRTE - Routes $GPTRF - Transit Fix Data $GPSTN - Multiple Data ID $GPVBW - Dual Ground / Water Speed $GPVTG - Track made good and ground speed $GPWPL - Waypoint location $GPXTE - Cross-track error, Measured $GPZDA - UTC Date / Time and Local Time Zone Offset There is a full list of $GPxxx sentence codes available, without links to format details. [Top] $GPAAM 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. $GPAAM,A,A,0.10,N,WPTNME*43 Where: AAM Arrival Alarm A Arrival circle entered A Perpendicular passed 0.10 Circle radius N Nautical miles WPTNME Waypoint name *43 Checksum data $GPALM GPS Almanac Data A set of sentences transmitted by some Garmin units in response to a received $PGRMO,GPALM,1 sentence. It can also be received by some GPS units (eg. Garmin GPS 16 and GPS 17) to initialize the stored almanac information in the unit. Example 1: $GPALM,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,*CC 1 = Total number of sentences in set 2 = Sentence sequence number in set 3 = Satellite number 4 = GPS week number 5 = Bits 17 to 24 of almanac page indicating SV health 6 = Eccentricity 7 = Reference time of almanac 8 = Inclination angle 9 = Right ascension rate 10 = Semi major axis route 11 = Argument of perigee (omega) 12 = Ascension node longitude 13 = Mean anomaly 14 = af0 clock parameter 15 = af1 clock parameter Example 2: $GPALM,1,1,15,1159,00,441d,4e,16be,fd5e,a10c9f,4a2da4,686e81,58cbe1,0a4,001*5B Field Example Comments Sentence ID $GPALM   Number of messages 1 Total number of messages in sequence Sequence number 1 This is first message in sequence Satellite PRN 15 Unique ID (PRN) of satellite message relates to GPS week number 1159   SV health 00 Bits 17-24 of almanac page Eccentricity 441d   Reference time 4e Almanac reference time Inclination angle 16be   Rate of right ascension fd5e   Roor of semi-major axis a10c9f   Argument of perigee 4a2da4   Longitude of ascension node 686e81   Mean anomoly 58cbe1   F0 clock parameter 0a4   F1 clock parameter 001   Checksum *5B     $GPAPB Autopilot format "B" 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. 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. $GPAPB,A,A,0.10,R,N,V,V,011,M,DEST,011,M,011,M*82 where: APB Autopilot format B A Loran-C blink/SNR warning, general warning A Loran-C cycle warning 0.10 cross-track error distance R steer Right to correct (or L for Left) N cross-track error units - nautical miles (K for kilometers) V arrival alarm - circle V arrival alarm - perpendicular 011,M magnetic bearing, origin to destination DEST destination waypoint ID 011,M magnetic bearing, present position to destination 011,M magnetic heading to steer (bearings could True as 033,T) $GPBOD Bearing Origin to Destination eg. BOD,045.,T,023.,M,DEST,START 045.,T bearing 045 degrees True from "START" to "DEST" 023.,M breaing 023 degrees Magnetic from "START" to "DEST" DEST destination waypoint ID START origin waypoint ID Example 1: $GPBOD,099.3,T,105.6,M,POINTB,*01Waypoint 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*52This 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.) $GPBWC Bearing and distance to waypoint, great circle eg1. $GPBWC,081837,,,,,,T,,M,,N,*13 BWC,225444,4917.24,N,12309.57,W,051.9,T,031.6,M,001.3,N,004*29 225444 UTC time of fix 22:54:44 4917.24,N Latitude of waypoint 12309.57,W Longitude of waypoint 051.9,T Bearing to waypoint, degrees true 031.6,M Bearing to waypoint, degrees magnetic 001.3,N Distance to waypoint, Nautical miles 004 Waypoint ID eg2. $GPBWC,220516,5130.02,N,00046.34,W,213.8,T,218.0,M,0004.6,N,EGLM*11 1 2 3 4 5 6 7 8 9 10 11 12 13 1 220516 timestamp 2 5130.02 Latitude of next waypoint 3 N North/South 4 00046.34 Longitude of next waypoint 5 W East/West 6 213.0 True track to waypoint 7 T True Track 8 218.0 Magnetic track to waypoint 9 M Magnetic 10 0004.6 range to waypoint 11 N unit of range to waypoint, N = Nautical miles 12 EGLM Waypoint name 13 *11 checksum $GPGGA Global Positioning System Fix Data eg1. $GPGGA,170834,4124.8963,N,08151.6838,W,1,05,1.5,280.2,M,-34.0,M,,,*75 Name Example Data Description Sentence Identifier $GPGGA Global Positioning System Fix Data Time 170834 17:08:34 UTC Latitude 4124.8963, N 41d 24.8963' N or 41d 24' 54" N Longitude 08151.6838, W 81d 51.6838' W or 81d 51' 41" W Fix Quality:- 0 = Invalid- 1 = GPS fix- 2 = DGPS fix 1 Data is from a GPS fix Number of Satellites 05 5 Satellites are in view Horizontal Dilution of Precision (HDOP) 1.5 Relative accuracy of horizontal position Altitude 280.2, M 280.2 meters above mean sea level Height of geoid above WGS84 ellipsoid -34.0, M -34.0 meters Time since last DGPS update blank No last update DGPS reference station id blank No station id Checksum *75 Used by program to check for transmission errors Courtesy of Brian McClure, N8PQI. Global Positioning System Fix Data. Time, position and fix related data for a GPS receiver. eg2. $GPGGA,hhmmss.ss,ddmm.mmm,a,dddmm.mmm,b,q,xx,p.p,a.b,M,c.d,M,x.x,nnnn hhmmss.ss = UTC of position ddmm.mmm = latitude of positiona = N or S, latitutde hemispheredddmm.mmm = longitude of positionb = E or W, longitude hemisphere q = GPS Quality indicator (0=No fix, 1=Non-differential GPS fix, 2=Differential GPS fix, 6=Estimated fix) xx = number of satellites in use p.p = horizontal dilution of precision a.b = Antenna altitude above mean-sea-levelM = units of antenna altitude, meters c.d = Geoidal heightM = units of geoidal height, meters x.x = Age of Differential GPS data (seconds since last valid RTCM transmission) nnnn = Differential reference station ID, 0000 to 1023 $GPGLL Geographic Position, Latitude / Longitude and time. eg1. $GPGLL,3751.65,S,14507.36,E*77 eg2. $GPGLL,4916.45,N,12311.12,W,225444,A 4916.46,N Latitude 49 deg. 16.45 min. North 12311.12,W Longitude 123 deg. 11.12 min. West 225444 Fix taken at 22:54:44 UTC A Data valid eg3. $GPGLL,5133.81,N,00042.25,W*75 1 2 3 4 5 1 5133.81 Current latitude 2 N North/South 3 00042.25 Current longitude 4 W East/West 5 *75 checksum $--GLL,lll.ll,a,yyyyy.yy,a,hhmmss.ss,A llll.ll = Latitude of position a = N or S yyyyy.yy = Longitude of position a = E or W hhmmss.ss = UTC of position A = status: A = valid data $GPGRS GPS Range Residuals Example: $GPGRS,024603.00,1,-1.8,-2.7,0.3,,,,,,,,,*6C Field Example Comments Sentence ID $GPGRS   UTC Time 024603.00 UTC time of associated GGA fix Mode 1 0 = Residuals used in GGA, 1 = residuals calculated after GGA Sat 1 residual -1.8 Residual (meters) of satellite 1 in solution Sat 2 residual -2.7 The order matches the PRN numbers in the GSA sentence Sat 3 residual 0.3   Sat 4 residual   Unused entries are blank Sat 5 residual     Sat 6 residual     Sat 7 residual     Sat 8 residual     Sat 9 residual     Sat 10 residual     Sat 11 residual     Sat 12 residual     Checksum *6C     $GPGSA GPS DOP and active satellites eg1. $GPGSA,A,3,,,,,,16,18,,22,24,,,3.6,2.1,2.2*3C eg2. $GPGSA,A,3,19,28,14,18,27,22,31,39,,,,,1.7,1.0,1.3*34 1 = Mode: M=Manual, forced to operate in 2D or 3D A=Automatic, 3D/2D 2 = Mode: 1=Fix not available 2=2D 3=3D 3-14 = PRN's of Satellite Vechicles (SV's) used in position fix (null for unused fields) 15 = Position Dilution of Precision (PDOP) 16 = Horizontal Dilution of Precision (HDOP) 17 = Vertical Dilution of Precision (VDOP)

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