NMEA Sentences
for GPS Receivers
Prof. David Bernstein
James Madison University
Computer Science Department
bernstdh@jmu.edu
Introduction
Who?
The National Marine Electronics Association (NMEA)
What?
A standard (NMEA-0183) for the formatting of Global Positioning System (GPS) information.
Why?
Boats/ships were some of the first users of GPS
Some Sentences for Marine Navigation
AAM - Waypoint arrival alarm
BOD - Bearing, origin to destination
BWC - Bearing and distance to waypoint, great circle
BWR - Bearing and distance to waypoint, rhumb line (overridden by BWC if available)
DPT - Depth of water
HDM - Heading, magnetic north
HDT - Heading, true north
MTW - Mean water temperature
WCV - Waypoint closure velocity
WPL - Waypoint location
Some General Sentences
GGA - Global Positioning System Fix Data
GLL - Geographic position, latitude and longitude (and time)
GSA - GPS DOP and active satellites
GSV - Satellites in view
The GGA Sentence
Example:
$GPGGA,210230,3855.4487,N,09446.0071,W,1,07,1.1,370.5,M,-29.5,M,,*7A
Fields:
The sentence type
Current time (if available; UTC; may include a decimal point)
Latitude (in DDMM.MMM format)
Latitude compass direction
Longitude (in DDDMM.MMM format)
Longitude compass direction
Fix type (0 for no fix, 1 for GPS, 2 for DGPS)
Number of satellites used for fix
Horizontal dilution of precision
Altitude above mean sea level
Altitude units (M for meters)
Height of mean sea level above WGS-84 earth ellipsoid
Units of the above geoid seperation (M for meters)
Time since last differential correction (ignored if inactive)
Differential station ID (ignored if inactive)
The checksum validation value (in hexadecimal)
The GSV Sentence
Example:
$GPGSV,2,1,08,02,74,042,45,04,18,190,36,07,67,279,42,12,29,323,36*77
$GPGSV,2,2,08,15,30,050,47,19,09,158,,26,12,281,40,27,38,173,41*7B
Fields:
The sentence type
The number of sentences in the sequence
The number of this sentence
The number of satellites
The satellite number, elevation, azimuth, and signal to noise ratio for each satellite
The checksum validation value (in hexadecimal)
There's Always More to Learn