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All $GPxxx sentence codes and short descriptions

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$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,*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.)

$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 position
a = N or S, latitutde hemisphere
dddmm.mmm = longitude of position
b = 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-level
M = units of antenna altitude, meters
c.d = Geoidal height
M = 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)

$GPGST

GPS Pseudorange Noise Statistics

Example: $GPGST,024603.00,3.2,6.6,4.7,47.3,5.8,5.6,22.0*58

Field Example Comments
Sentence ID $GPGST  
UTC Time 024603.00 UTC time of associated GGA fix
RMS deviation 3.2 Total RMS standard deviation of ranges inputs to the navigation solution
Semi-major deviation 6.6 Standard deviation (meters) of semi-major axis of error ellipse
Semi-minor deviation 4.7 Standard deviation (meters) of semi-minor axis of error ellipse
Semi-major orientation 47.3 Orientation of semi-major axis of error ellipse (true north degrees)
Latitude error deviation 5.8 Standard deviation (meters) of latitude error
Longitude error deviation 5.6 Standard deviation (meters) of longitude error
Altitude error deviation 22.0 Standard deviation (meters) of latitude error
Checksum *58  

$GPGSV

GPS Satellites in view 

eg. $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


$GPGSV,1,1,13,02,02,213,,03,-3,000,,11,00,121,,14,13,172,05*62


1 = Total number of messages of this type in this cycle
2 = Message number
3 = Total number of SVs in view
4 = SV PRN number
5 = Elevation in degrees, 90 maximum
6 = Azimuth, degrees from true north, 000 to 359
7 = SNR, 00-99 dB (null when not tracking)
8-11 = Information about second SV, same as field 4-7
12-15= Information about third SV, same as field 4-7
16-19= Information about fourth SV, same as field 4-7

$GPHDT

Heading, True.

Actual vessel heading in degrees Ture produced by any device or system producing true heading.

$--HDT,x.x,T
x.x = Heading, degrees True

$GPMSK

Control for a Beacon Receiver 

 $GPMSK,318.0,A,100,M,2*45

where:
 318.0 Frequency to use
 A Frequency mode, A=auto, M=manual
 100 Beacon bit rate
 M Bitrate, A=auto, M=manual
 2 frequency for MSS message status (null for no status)
 *45 checksum

$GPMSS

Beacon Receiver Status

Example 1: $GPMSS,55,27,318.0,100,*66 

where:
 55 signal strength in dB
 27 signal to noise ratio in dB
 318.0 Beacon Frequency in KHz
 100 Beacon bitrate in bps
 *66 checksum

Example 2: $GPMSS,0.0,0.0,0.0,25,2*6D

Field Example Comments
Sentence ID $GPMSS  
Signal strength 0.0 Signal strength (dB 1uV)
SNR 0.0 Signal to noise ratio (dB)
Frequency 0.0 Beacon frequency (kHz)
Data rate 25 Beacon data rate (BPS)
Unknown field 2 Unknown field sent by GPS receiver used for test
Checksum *6D  

$GPR00

List of waypoint IDs in currently active route 

eg1. $GPR00,EGLL,EGLM,EGTB,EGUB,EGTK,MBOT,EGTB,,,,,,,*58
eg2. $GPR00,MINST,CHATN,CHAT1,CHATW,CHATM,CHATE,003,004,005,006,007,,,*05


List of waypoints. This alternates with $GPWPL cycle
which itself cycles waypoints.

$GPRMA

Recommended minimum specific Loran-C data 

eg. $GPRMA,A,lll,N,lll,W,x,y,ss.s,ccc,vv.v,W*hh
A = Data status 
lll = Latitude
N = N/S
lll = longitude
S = W/E
x = not used
y = not used
ss.s = Speed over ground in knots
ccc = Course over ground
vv.v = Variation
W = Direction of variation E/W
hh = Checksum

$GPRMB

Recommended minimum navigation information (sent by nav. receiver when a destination waypoint is active) 

eg1. $GPRMB,A,0.66,L,003,004,4917.24,N,12309.57,W,001.3,052.5,000.5,V*0B


A Data status A = OK, V = warning
0.66,L Cross-track error (nautical miles, 9.9 max.),
steer Left to correct (or R = right)
003 Origin waypoint ID
004 Destination waypoint ID
4917.24,N Destination waypoint latitude 49 deg. 17.24 min. N
12309.57,W Destination waypoint longitude 123 deg. 09.57 min. W
001.3 Range to destination, nautical miles
052.5 True bearing to destination
000.5 Velocity towards destination, knots
V Arrival alarm A = arrived, V = not arrived
*0B mandatory checksum


eg2. $GPRMB,A,4.08,L,EGLL,EGLM,5130.02,N,00046.34,W,004.6,213.9,122.9,A*3D
1 2 3 4 5 6 7 8 9 10 11 12 13

 
 1 A validity
 2 4.08 off track
 3 L Steer Left (L/R)
 4 EGLL last waypoint
 5 EGLM next waypoint
 6 5130.02 Latitude of Next waypoint
 7 N North/South
 8 00046.34 Longitude of next waypoint
 9 W East/West
 10 004.6 Range
 11 213.9 bearing to waypt.
 12 122.9 closing velocity
 13 A validity
 14 *3D checksum


eg3. $GPRMB,A,x.x,a,c--c,d--d,llll.ll,e,yyyyy.yy,f,g.g,h.h,i.i,j*kk
1 = Data Status (V=navigation receiver warning)
2 = Crosstrack error in nautical miles
3 = Direction to steer (L or R) to correct error
4 = Origin waypoint ID#
5 = Destination 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, degrees True
12 = Destination closing velocity in knots
13 = Arrival status; (A=entered or perpendicular passed)
14 = Checksum

$GPRMC

Recommended minimum specific GPS/Transit data 

eg1. $GPRMC,081836,A,3751.65,S,14507.36,E,000.0,360.0,130998,011.3,E*62
eg2. $GPRMC,225446,A,4916.45,N,12311.12,W,000.5,054.7,191194,020.3,E*68


225446 Time of fix 22:54:46 UTC
A Navigation receiver warning A = Valid position, V = Warning
4916.45,N Latitude 49 deg. 16.45 min. North
12311.12,W Longitude 123 deg. 11.12 min. West
000.5 Speed over ground, Knots
054.7 Course Made Good, degrees true
191194 UTC Date of fix, 19 November 1994
020.3,E Magnetic variation, 20.3 deg. East
*68 mandatory checksum


eg3. $GPRMC,220516,A,5133.82,N,00042.24,W,173.8,231.8,130694,004.2,W*70
1 2 3 4 5 6 7 8 9 10 11 12


1 220516 Time Stamp
2 A validity - A-ok, V-invalid
3 5133.82 current Latitude
4 N North/South
5 00042.24 current Longitude
6 W East/West
7 173.8 Speed in knots
8 231.8 True course
9 130694 Date Stamp
10 004.2 Variation
11 W East/West
12 *70 checksum


eg4. for NMEA 0183 version 3.00 active the Mode indicator field is added
$GPRMC,hhmmss.ss,A,llll.ll,a,yyyyy.yy,a,x.x,x.x,ddmmyy,x.x,a,m*hh
Field #
1 = UTC time of fix
2 = Data status (A=Valid position, V=navigation receiver warning)
3 = Latitude of fix
4 = N or S of longitude
5 = Longitude of fix
6 = E or W of longitude
7 = Speed over ground in knots
8 = Track made good in degrees True
9 = UTC date of fix
10 = Magnetic variation degrees (Easterly var. subtracts from true course)
11 = E or W of magnetic variation
12 = Mode indicator, (A=Autonomous, D=Differential, E=Estimated, N=Data not valid)
13 = Checksum

$GPRTE

Routes 

eg. $GPRTE,2,1,c,0,PBRCPK,PBRTO,PTELGR,PPLAND,PYAMBU,PPFAIR,PWARRN,PMORTL,PLISMR*73
 $GPRTE,2,2,c,0,PCRESY,GRYRIE,GCORIO,GWERR,GWESTG,7FED*34
 1 2 3 4 5 ..
  1. Number of sentences in sequence
  2. Sentence number
  3. 'c' = Current active route, 'w' = waypoint list starts with destination waypoint
  4. Name or number of the active route
  5. onwards, Names of waypoints in Route

$GPTRF

Transit Fix Data

Time, date, position, and information related to a TRANSIT Fix.

$--TRF,hhmmss.ss,xxxxxx,llll.ll,a,yyyyy.yy,a,x.x,x.x,x.x,x.x,xxx
hhmmss.ss = UTC of position fix
xxxxxx = Date: dd/mm/yy
llll.ll,a = Latitude of position fix, N/S
yyyyy.yy,a = Longitude of position fix, E/W
x.x = Elevation angle
x.x = Number of iterations
x.x = Number of Doppler intervals
x.x = Update distance, nautical miles
x.x = Satellite ID

$GPSTN

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.

$--STN,xx
xx = Talker ID number, 00 to 99

$GPVBW

Dual Ground / Water Speed

Water referenced and ground referenced speed data.

$--VBW,x.x,x.x,A,x.x,x.x,A
x.x = Longitudinal water speed, knots
x.x = Transverse water speed, knots
A = Status: Water speed, A = Data valid
x.x = Longitudinal ground speed, knots
x.x = Transverse ground speed, knots
A = Status: Ground speed, A = Data valid

$GPVTG

Track Made Good and Ground Speed. 

eg1. $GPVTG,360.0,T,348.7,M,000.0,N,000.0,K*43
eg2. $GPVTG,054.7,T,034.4,M,005.5,N,010.2,K*41


054.7,T True course made good over ground, degrees
034.4,M Magnetic course made good over ground, degrees
005.5,N Ground speed, N=Knots
010.2,K Ground speed, K=Kilometers per hour


eg3. for NMEA 0183 version 3.00 active the Mode indicator field
is added at the end
$GPVTG,054.7,T,034.4,M,005.5,N,010.2,K,A*53
A Mode indicator (A=Autonomous, D=Differential,
E=Estimated, N=Data not valid)

$GPWPL

Waypoint location 

eg1. $GPWPL,4917.16,N,12310.64,W,003*65


4917.16,N Latitude of waypoint
12310.64,W Longitude of waypoint
003 Waypoint ID


When a route is active, this sentence is sent once for each
waypoint in the route, in sequence. When all waypoints have
been reported, GPR00 is sent in the next data set. In any
group of sentences, only one WPL sentence, or an R00
sentence, will be sent.


eg2. $GPWPL,5128.62,N,00027.58,W,EGLL*59
1 2 3 4 5 6


1 5128.62 Latitude of nth waypoint on list
2 N North/South
3 00027.58 Longitude of nth waypoint
4 W East/West
5 EGLL Ident of nth waypoint
6 *59 checksum

$GPXTE

Cross Track Error, Measured 

eg1. $GPXTE,A,A,0.67,L,N


A General warning flag V = warning
(Loran-C Blink or SNR warning)
A Not used for GPS (Loran-C cycle lock flag)
0.67 cross track error distance
L Steer left to correct error (or R for right)
N Distance units - Nautical miles


eg2. $GPXTE,A,A,4.07,L,N*6D
1 2 3 4 5 6


1 A validity
2 A cycle lock
3 4.07 distance off track
4 L steer left (L/R)
5 N distance units
6 *6D checksum

$GPZDA

UTC Date / Time and Local Time Zone Offset

Example 1: $GPZDA,hhmmss.ss,xx,xx,xxxx,xx,xx 

hhmmss.ss = UTC
xx = Day, 01 to 31
xx = Month, 01 to 12
xxxx = Year
xx = Local zone description, 00 to +/- 13 hours
xx = Local zone minutes description (same sign as hours)

Example 2: $GPZDA,024611.08,25,03,2002,00,00*6A

Field Example Comments
Sentence ID $GPZDA  
UTC Time 024611.08 UTC time
UTC Day 25 UTC day (01 to 31)
UTC Month 03 UTC month (01 to 12)
UTC Year 2002 UTC year (4 digit format)
Local zone hours 00 Offset to local time zone in hours (+/- 00 to +/- 59)
Local zone minutes 00 Offset to local time zone in minutes (00 to 59)
Checksum *6A  

[ Top ]

12 interpreted Garmin proprietary sentences transmitted by GPS unit

$HCHDG

Compass Heading

This sentence is used on Garmin eTrex summit, Vista and GPS76S receivers to output the value of the internal flux-gate compass. Only the magnetic heading and magnetic variation is shown in the message. 

 $HCHDG,101.1,,,7.1,W*3C

where:
 HCHDG Magnetic heading, deviation, variation
 101.1 heading
 ,, deviation (no data)
 7.1,W variation

$PGRMB

DGPS Beacon Information

$PGRMB,1,2,3,4,5,6,7,8,9*HH
1 = Tune frequency, Kilohertz (283.5 - 325.0 in 0.5 steps)
2 = Bit rate, Bits / second (0, 25, 50, 100, 200)
3 = SNR (Signal to Noise Ratio), 0 - 31
4 = Data Quality, 0 - 100
5 = Distance to beacon reference station
6 = Distance unit (K=Kilometres)
7 = Receiver communication status (0=Check wiring, 1=No signal, 2=Tuning, 3=Receiving, 4=Scanning)
8 = Fix source (R=RTCM, W=WAAS, N=Non-DPGS fix)
9 = DGPS Mode (A=Automatic, W=WAAS only, R=RTCM Only, N=None; DGPS disabled)
HH = Checksum

$PGRME

Estimated Position Error 

eg. $PGRME,15.0,M,45.0,M,25.0,M*22


15.0,M Estimated horizontal position error (HPE), M=metres
45.0,M Estimated vertical position error (VPE), M=metres
25.0,M Overall spherical equivalent position error, M=metres

$PGRMF

GPS Position Fix Data

$PGRMF,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15*HH
1 = GPS week number
2 = GPS seconds in current week
3 = UTC date, ddmmyy format
4 = UTC time, hhmmss format
5 = GPS leap second count
6 = Latitude, dddmm.mmmm format
7 = Latitude hemisphere, N or S
8 = Longitude, dddmm.mmmm format
9 = Longitude hemisphere, E or W
10 = Mode (M=Manual, A=Automatic)
11 = Fix type (0=No fix, 1=2D fix, 2=3D fix)
12 = Speed over ground, kilometres / hour
13 = Course over ground, degrees true
14 = PDOP (Position dilution of precision), rounded to nearest integer
15 = TDOP (Time dilution of precision), rounded to nearest integer
HH = Checksum

$PGRMM

Map datum

Example 1: $PGRMM,Astrln Geod '66*51

'Astrln Geod 66' = Name of currently active datum

Example 2: $PGRMM,NAD27 Canada*2F

'NAD27 Canada' = Name of currently active datum 









$PGRMT





Sensor Status Information 





$PGRMT,1,2,3,4,5,6,7,8,9*HH




1 = Garmin product model and software version (eg. GPS 16 VER 2.10)




2 = ROM checksum test (P=Pass, F=Fail)




3 = Receiver failure discrete (P=Pass, F=Fail)




4 = Stored data lost (R=Retained, L=Lost)




5 = Real time clock lost (R=Retained, L=Lost)




6 = Oscillator drift discrete (P=Pass, F=Excessive drift detected)




7 = Data collection discrtete (C=Collecting, Null=Not Collecting)




8 = GPS sensor temperature (Degrees C)




9 = GPS sensor configuration data (R=Retained, L=Lost)




HH = Checksum 













$PGRMV





3D Velocity Information 





$PGRMV,1,2,3*HH




1 = True east velocity, metres / sec




2 = True north velocity, metres / sec




3 = Upward velocity, metres / sec




HH = Checksum 













$PGRMZ





Altitude Information 





eg1. $PGRMZ,246,f,3*1B
eg2. $PGRMZ,93,f,3*21

 
 93,f Altitude in feet
 3 Position fix dimensions 2 = user altitude
 3 = GPS altitude
 This sentence shows in feet, regardless of units shown on the display.


eg3. $PGRMZ,201,f,3*18
1 2 3


1 201 Altitude
2 F Units - f-Feet
3 checksum








$PSLIB





Tune DPGS Beacon Receiver 





Proprietary Differential Control
sentences to control a Starlink differential beacon receiver, assuming
Garmin's DBR is made by Starlink. 





eg1. $PSLIB,290.5,100,J*22
eg2. $PSLIB,300.0,200,K*23





These two sentences are normally
sent together in each group of sentences from the GPS. 





The three fields are: Frequency,
bit Rate, Request Type. The value in the third field may be: J = status
request, K = configuration request, blank = tuning message. 





When the GPS receiver is set to
change the DBR frequency or baud rate, the "J" sentence is replaced
(just once) by (for example): $PSLIB,320.0,200*59 to set the DBR to 320
KHz, 200 baud. 





To tune a Garmin GBR 21, GBR 23
or equivalent beacon receiver. 





$PSLIB,1,2*HH




1 = Beacon tune frequency, Kilohertz (283.5 - 325.0 in 0.5 steps)




2 = Beacon bit rate, Bits / second (0, 25, 50, 100, 200




HH = Checksum 






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8 interpreted Garmin proprietary sentences received by GPS
unit





 





A few Garmin GPS receiver units are known to receive these
sentences, including the GPS 16 and GPS 17 modules. 





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$PGRMC





Sensor Configuration Information 





Used to configure the GPS
sensor's operation. The GPS will also transmit this sentence upon
receiving this same sentence or the $PGRMCE sentence. 





$PGRMC,1,2,3,4,5,6,7,8,9,10,11,12,13,14*HH




1 = Fix mode (A=Automatic, 2=2D exclusively; host system must supply
altitude, 3=3D exclusively)




2 = Altitude above/below mean sea level, metres




3 = Earth datum index. If the user datum index is specified (96),
fields 4 to 8 must contain valid values, otherwise they must be blank.




4 = Semi-major axis, metres, 0.001 metre resolution




5 = Inverse flattening factor, 285 to 310, 10e-9 resolution




6 = Delta X earth centred coordinate, metres, -5000 to 5000, 1 metre
resolution




7 = Delta Y earth centred coordinate, metres, -5000 to 5000, 1 metre
resolution




8 = Delta Z earth centred coordinate, metres, -5000 to 5000, 1 metre
resolution




9 = Differential mode (A=Automatic; output DGPS fixes when available
otherwise non-DGPS, D=Only output differential fixes)




10 = NMEA 0183 baud rate (1=1200, 2=2400, 3=4800, 4=9600, 5=19200,
6=300, 7=600)




11 = Velocity filter (0=None, 1=Automatic, 2-255=Filter time constant;
seconds)




12 = PPS mode (1=None, 2=1 Hertz)




13 = PPS pulse length, N = 0 to 48. Length (milliseconds) = (N+1)*20




14 = Dead reckoning valid time, 1 to 30, seconds




HH = Checksum 








$PGRMCE





Sensor Configuration Information
Enquiry 





The unit will respond by
transmitting a $PGRMC sentence containing the current default values. 





$PGRMCE*HH




HH = Checksum 








$PGRMC1





Additional Sensor Configuration
Information 





Used to configure additional
aspects of the GPS sensor's operation. The GPS will also transmit this
sentence upon receiving this same sentence or the $PGRMC1E sentence. 





$PGRMC1,1,2,3,4,5,6,7,8,9*HH




1 = NMEA 0183 output time, 1-900, seconds (Not applicable to GPS16A)




2 = Binary phase output data (1=Off, 2=On)




3 = Position pinning (1=Off, 2=On)




4 = DGPS beacon frequency, Kilohertz, 283.5 to 325.0 in 0.5 steps




5 = DGPS beacon bit rate (0, 25, 50, 100, 200)




6 = DGPS beacon scanning (1=Off, 2=On)




7 = NMEA 0183 version 3.00 mode indicator (1=Off, 2=On)




8 = DGPS mode (A=Automatic, W=WAAS only, R=RTCM only, N=None; DGPS
disabled)




9 = Power save mode (P=Activated, N=Normal)




HH = Checksum 








$PGRMC1E





Additional Sensor Configuration
Information Enquiry 





The unit will respond by
transmitting a $PGRMC1 sentence containing the current default values. 





$PGRMC1E*HH




HH = Checksum 








$PGRMI





Sensor Initialization Information






Used to set the GPS sensor's set
time and position and then commences satellite acquisition. The GPS
will also transmit this sentence upon receiving this same sentence or
the $PGRMIE sentence. 





$PGRMI,1,2,3,4,5,6,7*HH




1 = Latitude, dddmm.mmm format




2 = Latitude hemisphere, N or S




3 = Longitude, dddmm.mmm format




4 = Longitude hemisphere, N or S




5 = Current UTC date, ddmmyy format




6 = Current UTC time, hhmmss format




7 = Receiver command (A=Auto locate, R=Unit reset)




HH = Checksum 








$PGRMIE





Sensor Initialization
Information Enquiry 





The unit will respond by
transmitting a $PGRMI sentence containing the current default values. 





$PGRMIE*HH




HH = Checksum 








$PGRMO





Output Sentence Enable / Disable 





$PGRMO,xxxxx,n*HH




xxxxx = Target sentence name (eg. GPGGA, GPGSA)




n = Target mode (0=Disable specified sentence, 1=Enable specified
sentence, 2=Disable all output sentences except PSLIB, 3=Enable all
output sentences except GPALM, 4=Restore factory defaults)




HH = Checksum 






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Format of latitudes and longitudes





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. 






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