NMEA 0183 — Bad Checksum and Truncated Sentence
A 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.
$GPGGA,120000.00,4703.8414,N,01228.9205,W,1,08,0.9,12.1,M,49.0,M,,*4D
$GPRMC,120000.00,A,4703.8414,N,01228.9205,W,3.20,41.0,010126,,,A*41
$GPGSA,A,3,03,07,11,18,22,25,29,31,,,,,1.8,0.9,1.5*35
$GPVTG,41.0,T,,M,3.20,N,5.93,K,A*36
$GPGSV,3,1,11,03,72,132,42,07,45,215,39,11,33,058,35,18,25,301,31*74
$GPGSV,3,2,11,22,64,275,44,25,18,142,28,29,52,047,40,31,11,320,22*00
$GPGSV,3,3,11,08,07,198,19,,,,,,,,*4E
$GPGGA,120015.00,4703.9709,N,01228.6852,W,1,08,0.9,18.9,M,49.0,M,,*42
$GPRMC,120015.00,A,4703.9709,N,01228.6852,W,3.25,41.4,010126,,,A*4D
$GPGSA,A,3,03,07,11,18,22,25,29,31,,,,,1.8,0.9,1.5*35
$GPVTG,41.4,T,,M,3.25,N,6.02,K,A*3C
$GPGGA,120030.00,4704.0978,N,01228.4512,W,1,08,0.9,24.8,M,49.0,M,,*46
$GPGGA,120200.00,4703.8400,N,01228.9200
Specifications
- Format
- NMEA 0183
- Talker
- GP (GPS)
- Crs
- WGS 84 (EPSG:4326)
- Encoding
- ASCII
- Checksum Algorithm
- XOR of bytes between $ and *
- Date
- 2026-01-01
- Seed
- 20260807
- Sentences
- 13
- Invalid Checksums
- 1
- Truncated Sentences
- 1
- Valid Sentences
- 11
- Line Endings
- CRLF (per NMEA 0183)
- Defect
- one corrupted checksum plus one sentence cut off mid-transmission
Testing contract
Expected to recover- Scenario
- Parse the log with checksum verification enabled.
- Expected result
- The corrupted and truncated sentences are rejected and counted; the remaining sentences still parse, so one bad byte does not discard the whole log.
What is a .nmea file?
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 this 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.
How to use this file for testing
“NMEA 0183 — Bad Checksum and Truncated Sentence” is a deterministic Novus Examples fixture for Geospatial, Error handling, Data import. GeoJSON, GPX, and KML files with points, lines, polygons, and tracks — for testing map tools, route parsers, and geo importers.
Documented properties for this file: seed 20260807 · ASCII · CRLF (per NMEA 0183). Compare results against paired or grouped companions on this page when present (clean↔damaged, searchable↔scanned, or format twins) so scores stay reproducible across runs.
Download the file once, keep the path stable in CI or local scripts, and treat the spec table as the contract: dimensions, seeds, field lists, and roles are intentional. Corrupt or invalid samples are labelled as such — expect parsers to fail loudly rather than silently accept them.
Geospatial fixtures publish one invented territory across formats, with the coordinate reference system and feature counts documented in specs. Convert or reproject and diff against the twin in the same group; edge-case geometries state exactly which assumption they are built to break.
Related files
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- osmOSM XML — Intentionally Invalid: Way and Relation With Dangling ReferencesIntentionally invalid: a way referencing node -9 and a relation referencing way -999, neither of which is in the file. This is the normal state of a bounding-box extract, where objects are clipped at the boundary — so a reader has to decide between rejecting the file and building partial geometry, and must say which.
- geojsonGeoJSON — Antimeridian Line Split per RFC 7946The same transect cut at the 180th meridian into a two-part MultiLineString, which is what RFC 7946 section 3.1.9 recommends. The split latitude is the linear interpolation of the unsplit twin, so the two files describe the same ground path.
- geojsonGeoJSON — Antimeridian Polygon Split into a MultiPolygonThe straddling block cut at 180 into two polygons that share an edge on the meridian — the interoperable form. Use it as the expected output when testing an antimeridian-splitting routine against the unsplit twin.
- geojsonGeoJSON — Bare Geometry Object (no Feature)A top-level Geometry object with no Feature or FeatureCollection around it. This is legal GeoJSON and is what PostGIS `ST_AsGeoJSON` returns, but a surprising number of importers only accept a FeatureCollection.
- geojsonGeoJSON — Clockwise Exterior Ring (right-hand rule violated)Both rings of the Mill Court parcel are wound the wrong way round: the exterior clockwise, the interior counter-clockwise. RFC 7946 mandates the right-hand rule, and consumers that rely on winding to tell holes from shells will read this polygon inside out.
Generated by generation/geospatial.py. Free for any use, no attribution required — license.