nmea
What is a .nmea file?
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An .nmea file is a log of NMEA 0183 sentences, the ASCII protocol GPS and marine electronics use. Each line begins with `$` and a five-character talker-and-type identifier such as GPGGA, GPRMC, or GPGSV, carries comma-separated fields, and ends with `*` and a two-digit XOR checksum. Positions are encoded as degrees-and-decimal-minutes with a separate hemisphere field, not as decimal degrees.
How to use a .nmea file
Use an example .nmea file to test GPS log parsers and track converters, verifying checksum validation, correct degrees-minutes-to-decimal conversion, and sensible handling of sentences emitted before a fix is acquired.
Download example .nmea files
- NMEA 0183 — Mixed GGA/RMC/GSA/GSV/VTG LogA twelve-fix receiver log with the five sentence types a GPS unit normally interleaves, including three-part GSV satellite-in-view sets. Every checksum is correct, so a parser that verifies them should accept the whole file.
- NMEA 0183 — GGA Sentences OnlyThe same twelve fixes reduced to GGA alone. GGA carries time-of-day but no date and no speed, so a parser that only reads GGA cannot place the track on a calendar — a real limitation that this file makes obvious rather than leaving to be discovered later.
- NMEA 0183 — Receiver With No FixSix cycles of a receiver that has power but no satellite lock: GGA fix quality 0, RMC status V, and empty coordinate fields throughout. Parsers that split on commas and index positionally read these empty fields as zeros and plot the track at Null Island.
- NMEA 0183 — Bad Checksum and Truncated SentenceA log with one sentence whose checksum has been altered and a final sentence truncated mid-transmission with no checksum at all — the two ways a serial GPS feed actually degrades. A correct parser drops both and keeps everything else.
- NMEA 0183 — Southern and Eastern Hemisphere IndicatorsNMEA never writes a negative coordinate: sign lives entirely in the N/S and E/W letters, and the numeric field is always positive. This log sits in the southern and eastern hemispheres, so a parser that ignores the hemisphere letter puts every fix in the wrong quadrant of the world.
- NMEA 0183 — LF Line Endings Instead of CRLFThe same sentences terminated with a bare LF rather than the CR LF the standard mandates — what you get after a log passes through a text editor or a Unix pipeline. Parsers that strip only "\r\n" leave a stray character on every line and then fail the checksum.