NMEA-0183 messages: Common message elements

Each message contains:

  • a message ID consisting of a talker ID (i.e., $GP) followed by the message type. For example, the message ID of the GGA message is $GPGGA.

  • a comma.

  • a number of fields, depending on the message type, separated by commas.

  • an asterisk.

  • a checksum value.

The following example shows a simple message with a message ID ($GPGGA), followed by 13 fields and a checksum value:

$GPGGA,172814.0,3723.46587704,N,12202.26957864,W,2,6,1.2,18.893,M,-25.669,M,2.0,0031*4F

NMEA Talker ID Stings

The NMEA Talker ID is the first two characters after the $ sign. The Talker ID may indicate what constellation(s) are used in the solution or solution type:

  • $GP = GPS

  • $GN = GNSS

  • $GL = GLONASS

  • $GA = Galileo

  • $GB = BeiDou

  • $GI = NavIC

  • $IN = INS

  • $PTNL indicates a “Proprietary Trimble Navigation Limited” message, which will be followed by a message ID indicating the type of message

NMEA message values

NMEA messages that the receiver generates contains the following values:

Value

Description

Latitude and Longitude

Latitude is represented as ddmm.mmmm and longitude is represented as dddmm.mmmm, where:

  • dd or ddd is degrees

  • mm.mmmm is minutes and decimal fractions of minutes

Direction

Direction (north, south, east, or west) is represented by a single character: N, S, E, or W.

Time

Time values are presented in Universal Time Coordinated (UTC) and are represented as hhmmss.ss, where:

  • hh is hours, from 00 through 23

  • mm is minutes

  • ss.ss is seconds with variable length decimal-fraction of seconds