gps-wizard

NMEA

Introduction

Pretty much all GPS / GNSS chipsets are NMEA-0183 compliant which is a simple text based protocol. NMEA-0183 is a closed standard which is available for purchase from the NMEA website, and it is not freely available to the public.

This website contains details that have been gleaned from a variety of open sources, including NMEA revealed and entirely independently of the official / commercial documentation. You can also find a decent overview of NMEA-0183 messages on the Trimble website.

A minimal NMEA implementation should support the GGA and RMC sentences. Click on the titles below for further details about each NMEA sentence.

Universal Sentences

The following NMEA sentences can be considered universal, apparently supported by all GPS / GNSS chipsets.

GGA - GNSS Fix

• Includes time (UTC), latitude, longitude, status, sats (00-12), HDOP, altitude.
• The maximum number of SVs (satellites) reported may be limited to 12, depending on the GPS / GNSS chipset.

GSA - GNSS Satellites Active

• Includes mode (2d / 3d), satellite and signal IDs, PDOP, HDOP, VDOP.
• Some manufacturers have made proprietary modifications to the GSA sentence for multi-band receivers.

GSV - GNSS Satellites in View

• Includes SVs for each constellation / signal and elevation + azimuth of each SV.
• Support for different signals from each satellite was added in NMEA 4.10.

RMC - Recommended Minimum Navigation Information

• Includes time (UTC), warning, latitude, longitude, SOG, COG, date.
• RMC is perhaps the most useful of all the NMEA sentences.

Common Sentences

The following NMEA sentences are relatively common, supported by many GPS / GNSS chipsets.

Most of the fields in these sentences are also available in GGA or GSV.

GLL - Geographic Latitude + Longitude

• The GLL sentence includes latitude and longitude, with time of position fix and status
• All of the fields in GLL are also present in RMC.

GNS - Global Navigation Satellite System

• Includes time (UTC), latitude, longitude, sats (0-99) and HDOP.
• The GNS sentence is a tweaked version of GGA, reporting the correct number of SVs (satellites).

VTG - Velocity and Track made Good

• Includes COG and SOG.
• All of the fields in VTG are also present in RMC, or can be derived from RMC.

ZDA - Zone Date and Time

• Includes time (UTC) and date (ddmmyyyy).
• This sentence may also provide the local time zone, if known by the GPS / GNSS receiver.

Support from Chipsets

Some example GPS / GNSS chipsets and their support for notable NMEA sentences:

Chipset	Example Device(s)	GGA	GLL	GNS	GSA	GSV	RMC	VTG	ZDA
Airoha AG3335M	COROS VERTIX 2, Garmin Fenix 7, Suunto 9/5/7	Yes	Yes	-	Yes	Yes	Yes	Yes	Yes
Broadcom BCM4774	Samsung Galaxy S7 + S8	Yes	-	-	Yes	Yes	Yes	-	-
Broadcom BCM47755	Quectel LC79D module	Yes	Yes	-	Yes	Yes	Yes	Yes	-
Broadcom BCM47758	Quectel LC29D module	Yes	-	Yes	Yes	Yes	Yes	-	-
Broadcom BCM4776	Google Pixel 7	Yes	-	-	Yes	Yes	Yes	-	-
MediaTek MTK3333	Garmin Fenix 3/5/5+	Yes	Yes	-	Yes	Yes	Yes	Yes	Yes
Qualcomm SDM845	Samsung Galaxy S10 Lite	Yes	-	Yes	Yes	Yes	Yes	Yes	-
Samsung Exynos 1280	Samsung Galaxy A53	Yes	Yes	-	Yes	Yes	Yes	Yes	-
Samsung Exynos 1380	Samsung Galaxy A54	Yes	Yes	-	Yes	Yes	Yes	Yes	-
SiRF Star III	Locosys GT-31	Yes	Yes	-	Yes	Yes	Yes	Yes	Yes
SiRF Star IV	Locosys GW-52 / GW-60	Yes	Yes	-	Yes	Yes	Yes	Yes	Yes
SiRF Star V	Suunto Ambit 3	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Sony CXD5603GF	COROS APEX Pro / VERTIX, Garmin Fenix 6	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes

Notes:

• All GPS / GNSS chipsets support GGA, GSA, GSV and RMC.
  • The majority of chipsets support GLL and VTG.
  • The minority of chipsets support GNS and ZDA.
• Locosys GT-31 firmware can output GGA, GLL, GSA, GSV, RMC, VTG and ZDA.
  • These can be selected in the “memory card” screen.
• Locosys GW-52 and GW-60 firmware only supports GGA, GSA, GSV and RMC with MediaTek chipsets.
  • This was determined by looking at text strings in the the firmware.
• GPSBabel outputs GGA , GSA (partially populated), RMC and VTG when processing SBP and SBN files.
  • GPSBabel is able to consume GGA, GLL, GSA, RMC, VTG and ZDA.

Rare Sentences

A number of rare NMEA sentences may be output by specific manufacturers.

These include $DTM, $EPE, $GBS, $GRS and $GST.

Some of these are described on a separate page.

Proprietary Sentences

A number of proprietary NMEA sentences may be output by specific vendors / manufacturers.

These include $PGLOR, $PGRM*, $PJL*, $PQ*, $PSAM*, $PSMSG, $PSRF*, $PSSGR, $PUBX.

These vendor specific extensions are summarised on a separate page.

Accuracy Estimates

A number of NMEA sentences may be output by specific manufacturers which give an idea about PVT accuracy.

Some of these accuracy estimates are described on a separate page.

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