Decoding of NMEA signals (Part 1)

27.05.2014

This section describes the functionality associated with the reception of data from navigation sensors, supporting the standard IEC 61162-1 or NMEA 0183.

Summary table

Summary table illustrates the principles of interaction with each navigation sensor.

Sensor	The type of data transmitted by the sensor	Posts supporting the transmitted data	Channel in the System Configuration Utility / Service / Sensors / Accuracy of the connected sensor
GPS (GLONASS, DECCA, LORAN)	Position (Lat. & Lon.)	GGA GLL RMC SNU	Pos. system 1 (Pos. system 2)
	COG & SOG	RMC VTG	Pos. system 1 (Pos. system 2)
	Satellite information	GGA	Pos. system 1 (Pos. system 2)
	Datum	DTM	Pos. system 1 (Pos. system 2)
	LORAN-C data status	SNU	Pos. system 1 (Pos. system 2)
	UTC time	ZDA ZLZ ZZU GGA GLL	Time
	UTC date	ZDA	Time
ARPA	Targets	TTM	ARPA_A (ARPA_B)
	VRM's, EBL's, Cursor	RSD	ARPA_A (ARPA_B)
	Heading	OSD VHW	Compass
	Speed through the water	OSD VHW	Log
Sounder	Depth under the sounder vibrator	DBT DPT DBK DBS	Sounder
Compass	Heading	HDT HDM OSD VHW	Compass
Speed log (dopler log)	Dpeed through the water	OSD VHW VBW	Log
Speed log (dopler log)	SOG	VBW	Log
Digital anemometer	Wind direction speed	VWR MWV VWT	Wind
Digital thermometer	Water temperature	MTW	Temperature
Yeoman digitizer	WP position	WPL	Yeoman

Format Data

This section provides a description of message formats, standards IEC 61162-1 and / or NMEA 0183, received and processed by the various navigational instruments.

Message format consists of the following parts:

$ - AAA, xx, a, c --- c, ... * hh <CR> <LF>.

N	Field	Description
1	$	Start of sentence
2	-	Talker id
3	AAA	Mnemonic code of identifying the data type
4	,	Data field delimiter
5	xx, a, c --- c ...	Data
6	* Hh	Checksum field
7	<cr> <lf>	End of sentence

DBK (Depth Below Keel) - depth of water under the keel

Standard NMEA 0183 v.2.1, 1995 (not recommended for new designs).

$ - DBK, x.x1, f2, x.x3, M4, x.x5, F6 * hh <CR> <LF>.

N	Field	Title	Value	Note
1	xx	Depth	The depth
2	f	Unit	'F' - ft
3	xx	Depth	The depth
4	M	Unit	'M' - Meters
5	xx	Depth	The depth
6	F	Unit	'F' - Fathoms

DBS (Depth Below Surface) - water depth relative to the water surface

Standard NMEA 0183 v.2.1, 1995 (not recommended for new designs).

$ - DBS, x.x1, f2, x.x3, M4, x.x5, F6 * hh <CR> <LF>.

N	Field	Title	Value	Note
1	xx	Depth	The depth
2	f	Unit	'F' - ft
3	xx	Depth	The depth
4	M	Unit	'M' - Meters
5	xx	Depth	The depth
6	F	Unit	'F' - Fathoms

DBT (Depth Below Transducer) - depth, measured from the vibrator sonar

Standard IEC 61162-1, 2000.

$ - DBT, x.x1, f2, x.x3, M4, x.x5, F6 * hh <CR> <LF>.

N	Field	Title	Value	Note
1	xx	Depth	The depth
2	f	Unit	'F' - ft
3	xx	Depth	The depth
4	M	Unit	'M' - Meters
5	xx	Depth	The depth
6	F	Unit	'F' - Fathoms

DPT (Depth) - depth

Standard iec 61162-1, 2000 IMO Resolution a.224 (vii).

Contains: the depth measured from the vibrator sonar and correction value for the location of the vibrator. positive correction means the distance from the vibrator to the water surface, the negative - distance from the vibrator to the keel.

$ - DPT, x.x1, x.x2, x.x3 * hh <CR> <LF>.

N	Field	Title	Note
1	xx	The depth (in meters)
2	xx	Correction (in meters)	not processed
3	xx	Maximum range scale in use	not processed

DTM (Datum reference) - geodetic data on the basis of

Standard IEC 61162-1, 2000.

Contains information on the reference ellipsoid into which the received coordinates.

$ - DTM, ccc1, a2, x.x3, a4, x.x5, a6, x.x7, ccc8 * hh <CR> <LF>.

N	Field	Title	Value	Note
1	ccc	Local datum	'W72' - WGS 72 'W84' - WGS 84 'IHO' - reference ellipsoid terminology IHO '999' - reference ellipsoid defined by the user 'S85' - SGS85 'P90' - PE90	Processed only 'W84'
2	a	Local datum subdivision code		not processed
3	xx	Lat offset, min		not processed
4	a	Hemisphere	'N' - North; 'S'-South	not processed
5	xx	Lon offset, min		not processed
6	a	Hemisphere	'E' - East; 'W' - West	not processed
7	xx	Altitude offset, m		not processed
8	ccc	Reference datum	'W84' - WGS84 'W72' - WGS72 'S85' - SGS85 'P90' - PE90	not processed

GGA (Global Positioning System Fix Data) - coordinate data for gps

Standard IEC 61162-1, 2000.

Contains: time, location and related data from the receiver-GPS.

$ - GGA, hhmmss.ss1, llll.ll2, a3, yyyyy.yy4, a5, x6, xx7, x.x8, x.x9, M10, x.x11, M12, x.x13, xxxx14 * hh <CR > <LF>.

N	Field	Title	Value	Note
1	hhmmss.ss	UTC time of observation	Hours, minutes, seconds	not processed in 3000 ns ecdis
2	llll.ll	Latitude waypoint	Degrees, minutes and tenths of minutes
3	a	Hemisphere	'N' - the north; 'S' - South
4	yyyyy.yy	Longitude Waypoint	Degrees, minutes and tenths of minutes
5	a	Hemisphere	'E' - the east; 'W' - Western
6	x	GPS quality indicator observation	'0' - observation is impossible or ineffective; '1' - valid observation, GPS type SPS; '2' - observation is valid diff. GPS SPS type '3' - valid observation, GPS PPS type '4' - valid observation, RTK	'4' is not processed
7	xx	Number of satellites used	0 to 12
8	xx	Horizontal Dilution of Precision
9	xx	Antenna height above sea level		not processed
10	m	Units	'M' - Meters	not processed
11	xx	Geoid separation	The vertical difference between the ellipsoid 'WGS-84' and sea level (geoid), 'minus' - below sea level ellipsoid	not processed
12	m	Units	'M' - Meters	not processed
13	xx	Age data diff. gps (seconds)
14	xxxx	Station code diff.gps	from 0000 to 1023

GLL (Geographic Position - Latitude / Longitude) - geographic coordinates

Standard IEC 61162-1, 2000.

Contains: the coordinates of the MS, the time of observation and data status.

$ - GLL, llll.ll1, a2, yyyyy.yy3, a4, hhmmss.ss5, A6, a7 * hh <CR> <LF>.

N	Field	Title	Value	Note
1	llll.ll	Latitude waypoint	Degrees, minutes and tenths of minutes
2	a	Hemisphere	'N' - the north; 'S' - South
3	yyyyy.yy	Longitude Waypoint	Degrees, minutes and tenths of minutes
4	a	Hemisphere	'E' - the east; 'W' - Western
5	hhmmss.ss	UTC time of observation	Hours, minutes, seconds	not processed in 3000 ns ecdis
6	a	Status data from the receiver-	'A' - reliable data; 'V'

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