01
Keep empty tokens in place
Paste one sentence per line. Blank lines are ignored without renumbering later records. GSA has twelve satellite slots; deleting empty tokens would move the DOP fields into the wrong positions.
Protocols & Binary Serialization
NMEA parserRead the fields behind the fix
Paste a captured log to inspect each sentence, including unknown layouts and damaged lines.
NMEA parser
Sentence details
Enter a log or try the example.
Your log is processed in this browser, without uploading or storing it.
Parsing options
Named fields: GGA, RMC, GLL, GSA, GSV, VTG and ZDA.
Decoded coordinates are numerical values, not a navigation approval. Inspect checksum and fix diagnostics.
Enter a log or try the example.
Use this NMEA parser when a receiver log looks plausible but the application reads the wrong position, drops a line or loses satellite fields. The report keeps the original tokens beside their meaning, so an empty slot never silently turns into zero.
Why use this NMEA parser?
Trace every line in a mixed log
The NMEA parser returns a record for each non-empty physical line. Recognized sentences, unknown vendor messages and malformed text remain in the same report, with their original line numbers for comparison with the capture.
Separate coordinates from confidence
A converted latitude does not certify a fix. Read the independent checksum result and receiver diagnostics alongside the numeric conversion; a bad checksum remains visible even when the fields can be read.
Check the details a quick split can miss
02
Distinguish missing from matching
Checksum inspection always runs. A missing suffix means unverified integrity; a mismatch includes both received and calculated values. The parser never rewrites the suffix to make a damaged sentence pass.
03
Control when the report updates
Automatic parsing waits 350 ms after an edit. Turn it off to use Parse or Ctrl/Cmd + Enter. Old results cannot be copied until refreshed; the JSON download includes every record, beyond the first 50 shown.
From wire tokens to inspectable fields
Seven receiver layouts
GGA, RMC and GLL cover position fields; GSA retains satellite slots and DOP; GSV lists per-message satellite groups; VTG exposes course and speed; ZDA carries a full date.
Checksum evidence
The NMEA sentence decoder computes XOR over the printable ASCII payload between the start marker and asterisk. Missing, malformed and mismatching suffixes have distinct states, independent of supported sentence type.
Coordinates and UTC
Latitude uses ddmm and longitude dddmm, followed by optional decimal minutes. Conversion applies S/W signs, checks minute and degree bounds, and preserves fractional UTC seconds, including a valid leap second.
Original fields and extensions
This GPS log parser preserves station and satellite identifiers with leading zeros. Optional mode, navigation status, system and signal fields keep their positions; extra fields are retained without invented names or meanings.
What this report can establish
- A documented subset
- Named decoding covers the seven listed layouts using public receiver manuals. Unknown standard or proprietary addresses remain raw fields. The tool does not certify conformance to every NMEA version or decode AIS payloads and NMEA 2000.
- No inferred timeline
- RMC carries ddmmyy: the two-digit year stays two digits. GGA and GLL receive no borrowed date. ZDA is checked as a calendar date, and its local offset never changes the supplied UTC time.
- No navigation decision
- No-fix and invalid-data flags remain diagnostics. The numerical coordinates are not a datum transformation; the receiver may use a configured datum. GGA altitude is not automatically an ellipsoidal height.
- Finite log fragments
- Input is limited to 1 MiB and 5,000 non-empty lines. Either whole-input limit stops the run. A line above 4,096 characters gets its own diagnostic while the rest of the batch is processed.
- No reconstruction or device access
- GSV fragments remain separate; the tool does not infer a satellite epoch, draw tracks, repair checksums or contact a receiver. Copy and download preserve all diagnostic records rather than extracting apparently valid coordinates.
NMEA parser questions
How are NMEA coordinates converted to decimal degrees?
Split off the final two digits before the decimal point as minutes, then add minutes divided by 60 to the degrees. S and W make the value negative. The raw field remains visible for checking the conversion.
What does GPGGA identify?
GP is the talker identifier and GGA is the position-data layout. GN can indicate combined satellite systems. The decoder selects the layout by the last three letters of a standard address and preserves the actual talker.
How does checksum verification work?
The NMEA checksum is an XOR of payload character codes, including commas but excluding the start marker and asterisk. Compare the calculated two-digit hexadecimal value with the suffix; a match cannot prove position accuracy.
Which sentence types can be read?
GGA, RMC, GLL, GSA, GSV, VTG and ZDA have named fields. Other types, including proprietary sentences, still appear in the report with their address and numbered original fields when the envelope can be split.
Why do some sentences show only a time?
GGA and GLL provide a UTC time without a date. This tool deliberately keeps that distinction. RMC exposes its two-digit year without a century guess; ZDA can supply an explicit four-digit calendar date.
Did a field surprise you?
Check another log fragment
Return to the NMEA parser with the next capture. Compare a reported problem against the numbered original fields before changing receiver settings.