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NMEA Sentences
for GPS Receivers


Prof. David Bernstein
James Madison University

Computer Science Department
bernstdh@jmu.edu

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Introduction
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  • 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
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  • 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
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  • 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
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  • 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
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  • 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
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