NMEA String Reference

nmea_logoHere’s a quick reference for commonly seen NMEA sentences in the realm of oceanographic research.  I find quick references like this useful when I need to decipher data files.

$–DBS, Depth Below Surface

Column Name Description Example Data
1 Sentence Identifier Depth Below Surface $SDDBS
2-3 Depth, feet Depth below surface in feet 2348.56,f
4-5 Depth, meters Depth below surface in meters 715.78,M
6-7 Depth, fathoms Depth below surface in fathoms 391.43,F
8 Checksum 2-byte XOR sum of data to check for transmission errors *4B

$–DPT, Depth Below Transducer

Column Name Description Example Data
1 Sentence Identifier Heading – Deviation and Variation $VDDPT
2 Depth, meters Depth in meters 2128.56
3 Offset from Transducer Positive means distance from transducer to waterline
Negative means distance from transducer to keel
3.4
4 Max Range Scale Max Range Scale in Use (meters) 200
5 Checksum 2-byte XOR sum of data to check for transmission errors *20

$–GGA, Global Position System Fix Data

Column Name Description Example Data
1 Sentence Identifier Global Positioning System Fix Data $GPGGA
2 Time GPS Time 170834 = 17:08:34 UTC
3-4 Latitude Degrees, decimal minutes, N/S 4124.8963,N = 41d 24.8963’N
5-6 Longitude Degrees, decimal minutes, E/W 08151.6838,W = 81d 51.6838’W
7 Fix Quality The Quality of the GPS Fix:
0 = Invalid
1 = GPS fix
2 = DGPS fix
2
8 # Satellites Number of satellites tracked 06
9 HDOP Horizontal Dilution of Precision 1.5
10-11 Altitude Height above sea-level in meters 234.5,M
12-13 Height over WGS84 Height above WGS84 ellipsoid in meters -25.1,M
14 DGPS stale interval Time since last DGPS update in seconds 9.0
15 DGPS Station ID Number of the DGPS station 0025
16 Checksum 2-byte XOR sum of data to check for transmission errors *4D

$–GLL, Geographic Position, Latitude/Longitude Data

Column Name Description Example Data
1 Sentence Identifier Global Position, Latitude/Longitude Data $GPGLL
2-3 Latitude Degrees, decimal minutes, N/S 4124.8963,N = 41d 24.8963’N
4-5 Longitude Degrees, decimal minutes, E/W 08151.6838,W = 81d 51.6838’W
6 Fix Time Time of position fix UTC 225423 = 22:54:23
7 Data Valid Is data active (A) or void (V) A
8 Checksum 2-byte XOR sum of data to check for transmission errors *4D

$–HDT, Heading, True

Column Name Description Example Data
1 Sentence Identifier Heading, True $HEHDT
2 Heading, true Heading in degrees, true 064.3
3 True Designation Static Text designating the heading is in reference to true North T
4 Checksum 2-byte XOR sum of data to check for transmission errors *2E

$PASHR, Attitude Sensor, INS

Column Name Description Example Data
1 Sentence Identifier Attitude Sensor $PASHR
2 Time Time (hhmmss.sss) UTC 134500.125
3-4 Heading Vessel Heading in degrees, true 270.34,T
5 Roll Vessel Roll in degrees, “+” = port up 0.12
6 Pitch Vessel Pitch in degrees, “+” = bow up 1.04
7 Heave Vessel Heave in meters 0.34
8 Roll Accuracy Roll angle accuracy estimate (stdev) in degrees 0.01
9 Pitch Accuracy Pitch angle accuracy estimate (stdev) in degrees 0.03
10 Heading Accuracy Heading angle accuracy estimate (stdev) in degrees 0.05/td>
11 Aiding Status Unknown 2
12 IMU Status Unknown 1
13 Checksum 2-byte XOR sum of data to check for transmission errors *7D

$PGSSRV_, Vehicle Attitude

Column Name Description Example Data
1 Sentence Identifier Sentence and Vehicle Identifier
$PGSSRVR = Little Hercules
$PGSSRVC = Camera Platform
$PGSSRVR
2 Heading Vehicle Heading in degrees 270.3
3 Pitch Vehicle Pitch in degrees 1.1
4 Roll Vehicle Roll in degrees -1.4
5 Depth Vehicle Depth 0.34
6 Depth Units Depth Units, Meters = m, Feet = f m
7 Altitude Vehicle Altitude 3.5
8 Altitude Units Altitude Units, Meters = m, Feet = f m
9 Data Validation Digital data field, bit-packed
Bit 0 (0x01) = Valid attitude data
Bit 1 (0x02) = Valid depth data
Bit 2 (0x04) = Valid altitude data
Bit 3 (0x08) = TBD
Bit 4 (0x10) = TBD
Bit 5 (0x20) = TBD
Bit 6 (0x40) = TBD
Bit 7 (0x80) = TBD
7
10 Spare Field TBD 0.0
11 Spare Field TBD 0.0
12 Checksum 2-byte XOR sum of data to check for transmission errors *AD

$PRDID, RDI Proprietary Heading, Pitch, Roll

Column Name Description Example Data
1 Sentence Identifier RDI Proprietary, Heading, Pitch, Roll $PRDID
2 Pitch Vessel Pitch in degrees, “+” = bow up. 1.21
3 Roll Vessel Roll in degrees, “+” = port up 0.12
4 Heading Vessel Heading in degrees, true 254.32
5 Checksum 2-byte XOR sum of data to check for transmission errors *7D

$–ROT, Rate of Turn

Column Name Description Example Data
1 Sentence Identifier Rate of Turn $HEROT
2 Rate of turn Rate of turn in degrees/min, “-” means turning to port 0007.8
3 Data Valid Is date valid (A) or void (V) A
4 Checksum 2-byte XOR sum of data to check for transmission errors *7B

$–VBW, Speed Through Water and Speed Over Ground

Column Name Description Example Data
1 Sentence Identifier Speed Through Water and Speed Over Ground $VDVBW
2 Longitudinal Water Speed Speed Ahead, through water “-” means astern 10.4
3 Transverse Water Speed Speed to Starboard, through water “-” means port 0.35
4 Water Data Status A = Valid, V = Void A
5 Longitudinal Ground Speed Speed Ahead, over ground “-” means astern 8.3
6 Transverse Ground Speed Speed to Starboard, over ground “-” means port 0.25
7 Ground Data Status A = Valid, V = Void A
8 Checksum 2-byte XOR sum of data to check for transmission errors *1C

$–VTG, Track Made Good and Speed Over Ground

Column Name Description Example Data
1 Sentence Identifier Track Made Good, Ground Speed $GPVTG
2-3 TMG T Track made good, True 054.3,T
4-5 TMG M Track made good, Magnetic 032.3,M
6-7 SOG N Speed Over Ground, knots 008.3,N
8-9 SOG K Speed Over Ground, kilometers/hour 016.3,K
10 Checksum 2-byte XOR sum of data to check for transmission errors *0E

$–M01, Zeno Met Sensors

Column Name Description Example Data
1 Sentence Identifier Zeno Met Sensor $WIM01
2 Sensor Date Sensor Date YY/MM/DD 10/06/24
3 Sensor Time Sensor Time hh:mm:ss 11:04:43
4 Barometer Uncorrected hPa (mBar) 1001.8
5 Sensor Height Sensor height above sea level 17.4
6 Quality Measurement Quality A = Valid, X = Void A
7 Air Temperature Temperature in C 29.36
8 Sensor Height Sensor height above sea level 17.4
9 Quality Measurement Quality A = Valid, X = Void A
10 Relative Humidity Relative Humidity (%) 74.3
11 Sensor Height Sensor height above sea level 17.4
12 Quality Measurement Quality A = Valid, X = Void A
13 Vector Wind Speed Vector Mean Relative Wind Speed meters/sec 15.9
14 Vector Wind Direction Vector Mean Relative Wind Direction, degrees Relative to Bow 77.4
15 Scalar Wind Speed Relative Mean Scalar Wind Speed meters/sec 15.9
16 Maximum Wind Speed Relative Wind Maximum Speed meters/sec 16.2
17 Sensor Height Sensor height above sea level 17.4
18 Quality Measurement Quality A = Valid, X = Void A
19 Shortwave Irradiance Shortwave Irradiance, Mean RAD output (Wm-2) 225.11
20 Sensor Height Sensor height above sea level 18.0
21 Quality Measurement Quality A = Valid, X = Void A
22 Longwave Irradiance Longwave Irradiance, Mean RAD output (Wm-2) -32.70
23 PIR Thermopile Voltage PIR Thermopile Voltage (mV) -368.00
24 PIR Case Temperature PIR Case Temperature (C) 32.25
25 PIR Dome Temperature PIR Dome Temperature (C) 31.99
26 Sensor Height Sensor height above sea level 18.0
27 Quality Measurement Quality A = Valid, X = Void X
28 Checksum 2-byte XOR sum of data to check for transmission errors *42

$–MWV, Acoustic Wind Sensor

Column Name Description Example Data
1 Sentence Identifier Acoustic Wind Sensor $WIMWV
2 Wind Direction Wind Direction in degrees 154.3
3 Direction Reference Wind Direction Reference, R = Relative, T = True R
4 Wind Speed Wind Speed 16.4
5 Speed Units Wind Speed Units, K = km/hr, M = m/sec, N = kt K
6 Sensor Status Sensor Status, A = Valid, V = Void A
7 Checksum 2-byte XOR sum of data to check for transmission errors *0A

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