Difference between revisions of "NMEA 0183"

Latest revision as of 19:44, 17 April 2019

Le standard NMEA-0183 est un format texte de messages structurant des données produites (essentiellement) par des récepteurs GPS via une liaison série (Baud rate: 4800 Number of data bits: 8 (bit 7 is 0) Stop bits: 1 (or more) Parity: none Handshake: none). NMEA-0183 est un format de données textuel des relevés GPS acquis par les terminaux GPS puis retournés à un hôte (par un port série par exemple). Il couvre un large spectre de données de navigation. Ces données sont envoyées par le récepteur en mode heartbeat à fréquence fixe (0,5 Hz par exemple).

Format

Documentation http://www.sparkfun.com/datasheets/GPS/NMEA%20Reference%20Manual1.pdf

Syntaxe

Chaque message est structuré de la manière suivante :

$AABBB,CC,DD,...*CK<CR><LF>

$ marqueur de début du message
AA pour l'identifiant de l'émetteur (''talker'')
BBB pour la phrase (''sentence'')
CK ''Checksum''
*
<CR> Carriage Return \r
<LF> Line Feed \n

le code C de la fonction de checksum

#define uchar unsigned char
        
uchar calcChecksum(uchar checksum,  uchar c){
        if ( c == '$' ) return 0;
        if ( c != '\r'  &&  c != '\n'  &&  c != '*' ) {
                checksum ^= c;
        }
        return checksum;
}

le code Arduino de la fonction de checksum

byte calcChecksum(byte checksum,  byte c){
  if ( c == '$' ) return 0;
  if ( c != '\r'  &&  c != '\n'  &&  c != '*' ) {
    checksum ^= c;
  }
  return checksum;
}

byte calcChecksumBuf(byte checksum,  byte buf[], int i, int len){
  for(;i<len; i++){
    checksum=calcChecksum(checksum,buf[i]);
  }
  return checksum;
}

Liens

http://www.tronico.fi/OH6NT/docs/NMEA0183.pdf

Messages de sortie

Chaque message est une ligne de texte commencant par $ et se terminant par [CR][LF] et contient les champs suivants

$IDMSG,D1,D2,D3,...Dn*CS[CR][LF]

ID: Talker id (GP pour GPS)
MSG: Message id
Di: Msg data fields
CS: Ckecksum 2 hexa for 8 bits

Most common message Ids are

GGA : GPS fix data (NMEA Version 2.1)
GLL : Geographic position - Latitude/Longitude
GSA : GPS DOP and active satellites
GSV : GPS satellites in view
RMC : Recommended minimum specific GPS/Transit data
VTG : Track made good and ground speed
ZDA : SiRF Timing Message
MSS : MSK Receiver Signal
150 : OkToSend
...

Exemples

$GPGGA,164503.0,4511.636,N,00546.242,E,1,6,3.25,00220,M,048,M,,*66
$GPVTG,000.0,T,002.0,M,000.00,N,000.00,K*4C
$GPRMC,214434,A,3753.666,N,12203.162,W,0.0,0.0,270901,15.4,E,A*33
$GPGGA,214616,3753.667,N,12203.167,W,1,04,5.6,121.1,M,-27.4,M,,*79
$GPGSV,3,1,10,01,69,062,47,03,12,106,37,04,12,279,00,08,12,250,00*77
$GPGLL,3753.667,N,12203.167,W,214616,A,A*54
$GPBOD,,T,,M,,*47

Messages d'entrée

$IDMSG,D1,D2,D3,...Dn*CS[CR][LF]

ID=PSRF

MSG=

100 : SetSerialPort : Set PORT A parameters and protocol
101 : NavigationInitialization : Parameters required for start using X/Y/Z (Input coordinates must be WGS84)
102 : SetDGPSPort = Set PORT B parameters for DGPS input
103 : Query/Rate Control = Query standard NMEA message and/or set output rate
104 : LLANavigationInitialization = Parameters required for start using Lat/Lon/Alt (Input coordinates must be WGS84)
105 : Development Data On/Off = Development Data messages On/Off
106 : Select Datum = Selection of datum to be used for coordinate transformations.
MSK : MSK Receiver Interface = Command message to a MSK radio-beacon receiver.

Messages

Message GLL - Geographic Position - Latitude/Longitude

contains the latitude and longitude of the present vessel position, the time of the position fix and the status.

$GPGLL,llll.lll,a,yyyyy.yyy,a,hhmmss.s,A*hh[CR][LF]

1,2 Latitude, N (North) or S (South)
3,4 Longitude, E (East) or W (West)
5 UTC of position
6 Status: A = Valid, V= Invalid
hh Checksum

Message GGA - GPS Fix Data

includes time, position and fix related data for the GPS receiver.

$GPGGA,hhmmss,llll.lll,a,nnnnn.nnn,b,t,uu,v.v,w.w,M,x.x,M,y.y,zzzz*hh[CR][LF]

1 UTC of Position
2,3 Latitude, N (North) or S (South)
4,5 Longitude, E (East) or W (West)
6 GPS Quality Indicator: 0 = No GPS, 1 = GPS, 2 = DGPS
7 Number of Satellites in Use
8 Horizontal Dilution of Precision (HDOP)
9, 10 Antenna Altitude in Meters, M = Meters
11, 12 Geoidal Separation in Meters, M=Meters. Geoidal separation is the difference between the WGS-84 earth ellipsoid and mean-sea-level.
13 Age of Differential GPS Data. Time in seconds since the last Type 1 or 9 Update
14 Differential Reference Station ID (0000 to 1023)
hh Checksum

Message VTG - Track Made Good and Ground Speed

conveys the actual track made good (COG) and the speed relative to the ground (SOG).

$GPVTG,x.x,T,x.x,M,x.x,N,x.x,K*hh[CR][LF]

1 Track made good in degrees true.
2 Track made good in degrees magnetic.
3,4 Speed over the ground (SOG) in knots.
5,6 Speed over the ground (SOG) in kilometer per hour.
hh Checksum

Remark: Velocity is always described as horizontal speed and heading

Outils

Mac OS X

Ligne de commande

screen /dev/tty.usbserial 4800

Linux

awk -F, '/\$GPGGA/ {print  strftime("%Y-%m-%d "),  $2, (substr($3,0,2) + (substr($3,3) / 60.0)) $4,  (substr($5,0,3) + (substr($5,4) / 60.0)) $6, $10; fflush();}' /dev/tty.usbserial

GPSLabel

GPSD

Windows

Bibliothèques

Arduino

MBed

STM32

https://github.com/Lora-net/LoRaMac-node/blob/ad7d0824cae91f1dac4978d9c938966a0d4f60c3/src/system/gps.c

Java avec RXTX

Javascript & Node.js

Node.js
GPS.js : parser NMEA + serial

git clone https://github.com/infusion/GPS.js.git
cd GPS.js/
npm install -g

npm install express --save
npm install socket.io --save
npm install sylvester --save
npm install kalman --save
npm install serialport --save
cd examples/
cd maps/
# Edit server.js for setting port and baudrate
node server.js
open http://localhost:3000

cd ..
cd dashboard/
# Edit server.js for setting port and baudrate
node server.js 
open http://localhost:3000