The standard sentence format GPS and marine electronics use to report data over a serial link. Each line begins with a dollar sign, a two-letter talker id and a three-letter sentence type, followed by comma-separated fields and a checksum.

How do I convert NMEA coordinates to decimal degrees?

Split the field into degrees and minutes: everything except the last two digits before the decimal point is degrees, the rest is minutes. Divide the minutes by 60, add, then negate for S or W.

What does GPGGA mean?

GP is the GPS talker id and GGA is the fix data sentence: time, position, fix quality, satellites in use, HDOP and altitude. GN appears instead of GP when a receiver combines several constellations.

How is the NMEA checksum calculated?

By XOR-ing the character codes of everything between the leading dollar sign and the asterisk, then writing the result as two hex digits. This parser recomputes it for every line and marks any that disagree.

Is my GPS log uploaded anywhere?

No. The log is parsed in your browser, so track data that reveals where you have been stays on your device.

NMEA Parser

Decode GPS NMEA sentences into coordinates, speed and GeoJSON, with checksums verified.

The NMEA Parser runs entirely in your browser. Your GPS log is decoded on your device, so location history never leaves it.

Open the GPX Viewer

About NMEA Parser

Almost every GPS receiver speaks NMEA 0183: comma-separated sentences that start with a talker id and a type, and end with an XOR checksum. Reading them by eye is tedious and error-prone, mostly because coordinates arrive as degrees and decimal minutes rather than decimal degrees. The field 4807.038,N means 48.1173 degrees, not 48.07 — misreading it is the classic way to plot a point in the wrong country. This parser decodes GGA, RMC, GLL, VTG, GSA, GSV and ZDA sentences into a readable table, verifies every checksum so corrupt lines are visible rather than silently trusted, and exports the track as GeoJSON.

Features

Decodes GGA, RMC, GLL, VTG, GSA, GSV and ZDA sentences
Converts degrees-and-decimal-minutes to decimal degrees correctly
Verifies the XOR checksum on every line and flags mismatches
Shows time, altitude, speed, course, fix quality and satellite count
Degrees, minutes and seconds available on hover
Exports fixes as a GeoJSON track plus one point per fix
Counts sentence types so you can see what a receiver is emitting
Unrecognised proprietary sentences are shown rather than dropped

How to use the NMEA Parser

Paste a log from your receiver, one sentence per line
Read the decoded table — bad checksums are marked in the first column
Switch to GeoJSON to see the track as geometry
Download the GeoJSON to open it in a map or GIS tool

Example

Input

$GPGGA,123519,4807.038,N,01131.000,E,1,08,0.9,545.4,M,46.9,M,,*47

Output

48.117300, 11.516667 · 12:35:19 UTC
GPS fix · 8 satellites · 545.4 m altitude

4807.038 is 48° 07.038′, which is 48.1173° — not 48.07°, the mistake that moves a point 50 kilometres.

Common errors & troubleshooting

Positions plot in the wrong place by a few dozen kilometres. — The degrees-and-minutes field has been read as decimal degrees. The first two or three digits are whole degrees and the rest is minutes, which must be divided by 60.
Sentences show a checksum mismatch. — The line was truncated or a serial connection dropped bytes. The checksum is the XOR of everything between the dollar sign and the asterisk, so any lost character makes it fail — treat those rows as unreliable.
Coordinates are all zero. — The receiver had no fix yet. An RMC sentence with status V, or a GGA with fix quality 0, carries empty or zero position fields until the antenna sees enough satellites.

Frequently asked questions

What is NMEA 0183?: The standard sentence format GPS and marine electronics use to report data over a serial link. Each line begins with a dollar sign, a two-letter talker id and a three-letter sentence type, followed by comma-separated fields and a checksum.
How do I convert NMEA coordinates to decimal degrees?: Split the field into degrees and minutes: everything except the last two digits before the decimal point is degrees, the rest is minutes. Divide the minutes by 60, add, then negate for S or W.
What does GPGGA mean?: GP is the GPS talker id and GGA is the fix data sentence: time, position, fix quality, satellites in use, HDOP and altitude. GN appears instead of GP when a receiver combines several constellations.
How is the NMEA checksum calculated?: By XOR-ing the character codes of everything between the leading dollar sign and the asterisk, then writing the result as two hex digits. This parser recomputes it for every line and marks any that disagree.
Is my GPS log uploaded anywhere?: No. The log is parsed in your browser, so track data that reveals where you have been stays on your device.

Related tools

GPX Viewer — Open a GPX file and see its tracks, routes and waypoints on a map, with distance, elevation and bounds.
Coordinate Converter (DMS & Decimal) — Convert coordinates between decimal degrees, DMS and degrees-decimal-minutes, both ways, in your browser.
GPX to GeoJSON — Convert GPX to GeoJSON and back — GPS tracks, routes and waypoints to GeoJSON features, or GeoJSON back to a GPX file.
GeoJSON Viewer & Validator — Paste or drop GeoJSON to validate it and see its features on a map, with feature counts and a bounding box.
Distance Between Coordinates — Measure the great-circle distance between two latitude/longitude points in km, miles and nautical miles, with bearing and a map.
Map Tile Calculator — Convert between coordinates, XYZ tiles, TMS and quadkeys, with tile counts.