NMEA Message Introduction

Custom Icon     1   NMEATALKE

1.1 Change TalkerID

NMEATALKER (Sentence ID) (Talker ID)

Sentence Identifier (ID): 10 sentence identifiers are available: GGA, GSA, GSV, GST, ZDA, HDT, RMC, VTG, GLL, ALL

Among these 10 identifiers, the first 9 are sentence identifiers and the last one ('ALL') is used to fulfill the function of manipulating all the first 9 identifiers.

Talker Identifier (ID): 6 talker identifiers are available: GN, GP, BD, GL, GA, AUTO

Among these 6 identifiers, the first 5 are talker identifiers and the last one ('AUTO') is used to indicate that receiver will automatically choose a talker identifier according to constellation used in current estimates. In 'AUTO' mode, how receiver choose a talker identifier is subject to the principles shown in the following table:

Table 1. NMEATALKER Available Identifiers Table

CONSTELLATION USED IN SOLUTIONS

TALKER IDENTIFIERS

GPS

GP

BDS

BD

GLONASS

GL

GALILEO

GA

Two or more constellations

GN

 

Note: According to the supplement NMEA 0183 V4.10 issued by NMEA and IEC on 19 June 2018, BDS Talker ID is no longer allowed to use "BD" and the standard requires the use of "GB". To maintain compatibility, ComNav's products use "BD" by default, but allow customers to change the BDS Talker ID to "GB" in custom firmware.

 

 

1.2 TalkerID Query

List talker identifiers for all current NMEA messages.

NMEATALKER LIST

 

1.3 TalkerID Reset

Reset talker identifiers to factory defaults.

NMEATALKER RESET

Tips:

Command is not case-sensitive and keywords are separated by space and each command is ended with a pair of Carriage Return (CR) and Line Feed (LF).

NMEATALKER commands only affect talker identifiers; LOG commands used to request a log is unaffected by NMEATALKER commands. Talker identifiers in LOG command remain 'GP':

 

Custom Icon     NMEA Message

Table 2. NMEA Message

No

Log Message

Description

1

GPGGA

GPS Fix Data and Undulation

2

GPGLL

Latitude and Longitude of Present Vessel Position

3

GPGSA

GPS DOP and Active Satellites

4

GPGST

Only Dop Values are Valid Currently

5

GPGSV

GPS Satellites in View

6

GPHDT

Actual Vessel Heading in Degrees True

7

GPRMC

GPS Specific Information

8

GPVTG

The Track Made Good and Speed Relative to the Ground

9

GPZDA

UTC Time and Date

 

 

2.1 GPGGA GNSS Fix Data

Description

This message is a standard NMEA log, but a little different from the standard one in position precision. The position precision of this log is the same as GPGGARTK, in order to be used in greater conditions. The header of GPGGA is always “GP” regardless if other GNSS information involved in solution computation.

Command

LOG GPGGA ONTIME 1

 

Table 3. Message definition

Field#

Structure

Description

Symbol

Example

1

$GPGGA

Log header

 

$GPGGA

2

utc

UTC time of position (hours/minutes/seconds/ decimal seconds)

hhmmss.ss

202134.00

3

lat

Latitude (DDmm.mm)

llll.lllllll

3110.4693903

4

latdir

Latitude direction (N = North, S = South)

a

N

5

lon

Longitude (DDDmm.mm)

yyyyy.yyyyyyy

121232621695

6

londir

Longitude direction (E = East, W = West)

a

W

7

GPS qual

GPS Quality indicator

0: Initialization

1: RTK Single solution

2: Code differential (including SBAS solution)

4: RTK fixed solution

5: RTK float solution

6: Combined navigation result

7:Manually input fixed value

x

1

8

# sats

Number of satellites in use. May be different to the number in view

xx

10

9

hdop

Horizontal dilution of precision

x.x

1.0

10

alt

Antenna altitude above/below mean sea level

x.x

1062.22

11

a-units

Units of antenna altitude (M = meters)

M

M

12

undulation

Undulation --- the relationship between the geoid and the WGS84 ellipsoid

x.x

-16.271

13

u-units

Units of undulation (M = meters)

M

M

14

age

Age of Differential GPS data (in seconds) b

xx

(empty when no differential data is present)

15

stn ID

Differential base station ID, 0000-1023

xxxx

16

*xx

Checksum

*hh

*48

17

[CR][LF]

Sentence terminator

 

[CR][LF]

 

In NMEA0183 standard, the maximum number for satellites is 12, why ComNav message shows more satellites? Does ComNav's module follow the standard?

Reply:

Yes ComNav follow NMEA0183 standard, but When NMEA0183 was initially released, GNSS receivers had limited capabilities and could typically track and receive signals from only 12 satellites simultaneously. Hence, to accommodate this limitation, the NMEA 0183 protocol specified a maximum of 12 satellites. With advancements in technology, modern GNSS receivers can track and receive signals from a higher number of satellites simultaneously, so it shows more satellites number in this message.

 

2.2 Geographic Position

Description

This message is a standard NMEA log, include information such as time, latitude, longitude and so on.

Command

LOG GPGLL ONTIME 1

 

Table 4.  Message definition

Field#

Structure

Description

Symbol

Example

1

$GPGLL

Log header

 

$GPGLL

2

lat

Latitude (DDmm.mm)

llll.lllllll

3110.4702936

3

latdir

Latitude direction

(N = North, S = South)

a

N

4

lon

Longitude (DDDmm.mm)

yyyyy.yyyyyyy

12123.2629222

5

londir

Longitude direction

(E = East, W = West)

a

W

6

utc

UTC time of position (hours/minutes/ seconds/decimal seconds)

hhmmss.ss

220152.50

7

data status

Data status: A = Data valid, V = Data invalid

A

A

8

mode ind

Positioning system mode indicator

a

A

9

*xx

Checksum

*hh

*1B

10

[CR][LF]

Sentence terminator

 

[CR][LF]

 

2.3 GPGSA GNSS DOP and Available Satellite

Description

This message contains available satellites used in solution computation and DOP values.

Command

LOG GPGSA ONTIME 1

 

Table 5.  Message definition

Field#

Structure

Description

Symbol

Example

1

$GPGSA

Log header

 

$GPGSA

2

mode MA

A = Automatic 2D/3D M = Manual, forced to operate in 2D or 3D

M

M

3

mode 123

Mode: 1 = Fix not available; 2 = 2D; 3 = 3D

x

3

4 - 15

prn

PRN numbers of satellites used in solution (null for unused fields), total of 12 fields

GPS = 1 to 32

SBAS = 33 to 64 (add 87 for PRN number)

GLO = 65 to 96

BD2 =141 to 177

xx,xx,.....

25,14,

15,18,

31,27,

09,21,

22,12,,,,

16

pdop

Position dilution of precision

x.x

1.5

17

hdop

Horizontal dilution of precision

x.x

0.9

18

vdop

Vertical dilution of precision

x.x

1.2

19

*xx

Checksum

*hh

*3F

20

[CR][LF]

Sentence terminator

 

[CR][LF]

 

2.4 GPGST Pseudorange Measurement Noise Statistics

Description

This message is a standard NMEA log. Pay attention to that rms, smjrstd, smnrstd and orient values are absent in the message currently.

Command

LOG GPGST ONTIME 1

 

Table 6.  Message definition

Field#

Structure

Description

Symbol

Example

1

$GPGST

Log header

 

$GPGST

2

utc

UTC time of position (hours/minutes/seconds/ decimal seconds)

hhmmss.ss

173653.00

3

rms

RMS value of the standard deviation of the range inputs to the navigation process. Range inputs include pseudorange and DGPS corrections.

x.x

 

4

smjrstd

Standard deviation of semi-major axis of error ellipse (m)

x.x

 

5

smnrstd

Standard deviation of semi-minor axis of error ellipse (m)

x.x

 

6

orient

Orientation of semi-major axis of error ellipse (degrees from true north)

x.x

 

7

latstd

Standard deviation of latitude error (m)

x.x

2.51

8

lonstd

Standard deviation of longitude error (m)

x.x

1.94

9

alt std

Standard deviation of altitude error (m)

x.x

4.30

10

*xx

Checksum

*hh

*6E

11

[CR][LF]

Sentence terminator

 

[CR][LF]

 

2.5 GPGSV GNSS Satellites in View

Description

This is a standard NMEA message which includes PRN numbers, elevation, azimuth, and SNR values of satellites in view.

Command

LOG GPGSV ONTIME 1

 

Table 7.  Message definition

Field#

Structure

Description

Symbol

Example

1

$GPGSV

Log header

 

$GPGSV

2

# msgs

Total number of messages (1-9)

x

3

3

msg #

Message number (1-9)

x

1

4

# sats

Total number of satellites in view. May be different than the number of satellites in use

xx

09

5

prn

Satellite PRN number

GPS = 1 to 32

SBAS = 120-138

GLO = 1-36

BD2 = 141~177

xx

03

6

elev

Elevation, degrees, 90 maximum

xx

51

7

azimuth

Azimuth, degrees True, 000 to 359

xxx

140

8

SNR

SNR (C/No) 00-99 dB, null when not tracking

xx

42

.... ....

... ...

Next satellite PRN number, elev, azimuth, SNR, ... Last satellite PRN number, elev, azimuth, SNR,

 

 

variable

*xx

Checksum

*hh

*72

variable

[CR][LF]

Sentence terminator

 

[CR][LF]

 

2.6 GPHDT Vessel Headin

Description

This message is a standard log which includes actual vessel heading for True North in degrees.

Command

LOG GPHDT ONTIME 1

 

Table 8.  Message definition

Field#

Structure

Description

Symbol

Example

1

$GPHDT

Log header

 

$GPHDT

2

heading

Heading in degrees

x.x

89.2769

3

True

Degrees True

T

T

4

*xx

Checksum

*hh

*36

5

[CR][LF]

Sentence terminator

 

[CR][LF]

 

2.7 GPRMC GNSS Specification Information

Description

This is a standard NMEA message which includes time, date, speed and true heading.

Command

LOG GPRMC ONTIME 1

 

Table 9.  Message definition

Field#

Structure

Description

Symbol

Example

1

$GPRMC

Log header

 

$GPRMC

2

utc

UTC of position

hhmmss.ss

065029.00

3

pos status

Position status:

A = data valid, V = data invalid

A

A

4

lat

Latitude (DDmm.mm)

llll.ll

3110.4722495

5

latdir

Latitude direction:

N = North, S = South

a

N

6

lon

Longitude (DDDmm.mm)

yyyyy.yy

12123.2644026

7

londir

Longitude direction:

E = East, W = West

a

E

8

speed Kn

Speed over ground, knots

x.x

0.456

9

track true

Track made good, degrees True

x.x

330.1

10

date

Date: dd/mm/yy

xxxxxx

050512

11

mag var

Magnetic variation, degrees

x.x

0.0

12

vardir

Magnetic variation direction E/W

a

W

13

mode ind

Positioning system mode indicator

A = Single-point positioning

D = Differential positioning

E = Derivation positioning

M = Manual input by user

N = Data invalid

a

A

14

*xx

Checksum

*hh

*12

15

[CR][LF]

Sentence terminator

 

[CR][LF]

 

2.8 GPVTG Track Make Good and Ground Speed

Description

This is a standard NMEA message which includes make good and ground speed.

Command

LOG GPVTG ONTIME 1

 

Table 10.  Message definition

Field#

Structure

Description

Symbol

Example

1

$GPVTG

Log header

 

$GPVTG

2

track true

Track made good, degrees True

x.x

213.710

3

T

True track indicator

T

T

4

track mag

Track made good, degrees Magnetic;

Track mag = Track true + (MAGVAR correction)

x.x

213.710

5

M

Magnetic track indicator

M

M

6

speed Kn

Speed over ground, knots

x.x

0.304

7

N

Nautical speed indicator (N = Knots)

N

N

8

speed Km

Speed, kilometers/hour

x.x

0.563

9

K

Speed indicator (K = km/hr)

K

K

10

mode ind

Positioning system mode indicator

a

A

11

*xx

Checksum

*hh

*24

12

[CR][LF]

Sentence terminator

 

[CR][LF]

 

2.9 GPZDA UTC Time and Date

Description

This message is a standard NMEA log which includes UTC time and date.

Command

LOG GPZDA ONTIME 1

 

Table 11.  Message definition

Field#

Structure

Description

Symbol

Example

1

$GPZDA

Log header

 

$GPZDA

2

utc

UTC time

hhmmss.ss

071642.000

3

day

Day, 01 to 31

xx

05

4

month

Month, 01 to 12

xx

05

5

year

Year

xxxx

2012

6

null

Local zone description - not available

xx

(empty when no data is present)

7

null

Local zone minutes description - not available

xx

N

8

*xx

Checksum

*hh

*6F

9

[CR][LF]

Sentence terminator

 

[CR][LF]

 

 


About ComNav Technology 


ComNav Technology develops and manufactures GNSS OEM boards and receivers for high precision positioning demanded applications. Its technology already been used in a wide range of applications such as surveying, construction, machine control, agriculture, intelligent transportation, precise timing, deformation monitoring, unmanned system. With a team dedicated for the GNSS technology, ComNav Technology is trying its best to supply reliable and competitive products to worldwide customers. ComNav Technology has been listed on the Shanghai Stock Exchange (Science and Technology Board), securities :ComNav Technology (Compass Navigation), Stock code: 688592.


 

About SinoGNSS®


SinoGNSS® is the official trademark of ComNav Technology Ltd., registered in People's Republic of China, EU, USA and Canada. All other trademarks are the property of their respective owners. 


About ComNav Technology


ComNav Technology develops and manufactures GNSS OEM boards and receivers for high precision positioning demanded applications. Its technology already been used in a wide range of applications such as surveying, construction, machine control, agriculture, intelligent transportation, precise timing, deformation monitoring, unmanned system. With a team dedicated for the GNSS technology, ComNav Technology is trying its best to supply reliable and competitive products to worldwide customers. ComNav Technology has been listed on the Shanghai Stock Exchange (Science and Technology Board), securities :ComNav Technology (Compass Navigation), Stock code: 688592.



About SinoGNSS®


SinoGNSS® is the official trademark of ComNav Technology Ltd., registered in People's Republic of China, EU, USA and Canada. All other trademarks are the property of their respective owners.

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