NMEA Log Viewer
Upload an NMEA 0183 log file to plot the track on an interactive map, view statistics such as fix count, duration and altitude range, and see the satellite side of the log: sky plot, C/N0 per constellation, DOP and the receiver's own accuracy estimate.
Drop an NMEA log file here or browse
.nmea, .txt, .log
NMEA Sentence Parsing
This tool reads GGA (fix data) and RMC (recommended minimum) sentences from your log file. Sentences from any GNSS talker ID are supported — GP (GPS), GN (multi-constellation), GL (GLONASS), GA (Galileo) and GB (BeiDou).
GGA and RMC sentences from the same epoch are merged automatically, combining altitude and satellite count from GGA with date, speed and course from RMC into a single fix.
Satellite sentences fill in what the fixes leave out: GSV (satellites in view — elevation, azimuth and C/N0) drives the sky plot and the C/N0 chart, GSA (satellites used in the fix, PDOP/HDOP/VDOP) the DOP chart and which satellites are highlighted, and GST the receiver's 1σ north/east/up error estimate. GSV and GSA carry no time of their own, so each is stamped with the time of the surrounding fix.
Checksum verification is performed when present. Lines with invalid checksums are silently discarded, while lines without a checksum are accepted.
Track Statistics
After parsing, the viewer displays the number of valid fixes, time span, average satellite count, altitude range and geographic bounding box. All values are computed from the parsed fixes only — no external data is used.
Related Tools
- Quality Control — analyze RINEX observation files with signal and satellite charts
- Coordinate Converter — convert coordinates and compute distances between points
- NTRIP Client — connect to GNSS correction streams in real time
- Signal Spectrum — interactive PSD chart of all GNSS L-band signals
NMEA FAQ
- What is NMEA 0183?
- NMEA 0183 is a standard protocol for communication between marine electronics and GNSS receivers. It defines ASCII sentence formats that carry position, time, satellite and navigation data over serial links.
- What is a GGA sentence?
- GGA (Global Positioning System Fix Data) is an NMEA sentence that reports time, latitude, longitude, fix quality, number of satellites, HDOP and altitude for each epoch. It is the most common sentence for position fixes.
- What is an RMC sentence?
- RMC (Recommended Minimum Specific GNSS Data) is an NMEA sentence that provides time, date, position, speed over ground and course over ground. It is the minimum data recommended for navigation.
- What NMEA sentences does this tool parse?
- This tool parses GGA and RMC sentences from any talker ID (GP, GN, GL, GA, GB). It merges GGA and RMC data from the same epoch to produce a combined fix with altitude, satellite count, speed and course. It also reads the satellite sentences: GSV (satellites in view with elevation, azimuth and C/N0, including NMEA 4.10 signal IDs), GSA (satellites used in the fix and PDOP/HDOP/VDOP, including NMEA 4.11 system IDs) and GST (the receiver’s own 1-sigma position error estimate).
- What is fix quality in GGA?
- Fix quality indicates the type of positioning solution: 0 = no fix, 1 = standalone GPS, 2 = DGPS, 4 = RTK fixed, 5 = RTK float, 6 = dead reckoning. Higher values generally indicate better accuracy.
- How do I get an NMEA log file?
- Most GNSS receivers can output NMEA sentences over a serial or USB connection. You can log these to a text file using a terminal program or dedicated logging software. Many smartphone apps also export NMEA logs.