Decoding of NMEA signals (Part 1)

27.05.2014

Decoding of NMEA signals (Part 1)

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

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

Value

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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