Free online NMEA to KML converter

GPS receivers, marine instruments, and navigation software often record position fixes as NMEA text, while Google Earth and many mapping systems expect KML. Converting the log creates a map-ready track that can be viewed, shared, edited, or archived with geographic context.

What the NMEA format is

NMEA 0183 is a line-based text format consisting of sentences such as $GPGGA, $GPRMC, and $GPGSA. These sentences can contain latitude, longitude, UTC time, altitude, speed, course, satellite count, and fix-quality information.

GPS receivers, chartplotters, surveying devices, vehicle trackers, and navigation programs create NMEA logs. Files commonly use .nmea, .log, or .txt extensions, although the extension alone does not identify the contents. A usable track normally requires repeated position sentences containing valid latitude and longitude values.

What the KML format is

KML is an XML-based geographic format used by Google Earth, Google Earth Pro, GIS applications, and web-mapping tools. It can store points, line tracks, placemarks, timestamps, names, descriptions, styles, and altitude information.

An NMEA log converted to KML usually becomes a LineString representing the recorded route, optionally accompanied by placemarks or time data. KML is useful when the recipient needs to inspect the route visually rather than parse raw navigation sentences.

How to convert NMEA to KML

Using GPSBabel on a computer

1. Install GPSBabel for your operating system.
2. Keep the original NMEA log unchanged and identify the file containing the sentences.
3. Run this command in a terminal or command prompt:
   gpsbabel -i nmea -f input.nmea -o kml -F output.kml
4. Open output.kml in Google Earth, Google Earth Pro, or another KML-compatible program.

Replace input.nmea and output.kml with the actual paths. GPSBabel reads supported NMEA position sentences and writes the coordinates as KML geographic features.

Using the online converter

You can convert the file for free on the 101convert.com website without installing software: open the NMEA-to-KML converter, upload the NMEA file, start the conversion, and download the resulting .kml file. Do not upload logs containing sensitive routes or location data unless the service’s privacy terms are acceptable.

Quality and compatibility limits

The conversion cannot recover information that was never recorded. Lines may contain gaps when the receiver lost its fix, and invalid or incomplete sentences may be skipped. If the source contains only speed, satellite, or status sentences without coordinates, it cannot produce a geographic track.

Latitude and longitude are normally converted from NMEA degrees-and-decimal-minutes notation into decimal degrees required by KML. Check the result in a map, especially when the log crosses the equator or prime meridian, because incorrect hemisphere fields such as N/S or E/W can place the track on the wrong side of the Earth.

Altitude behavior depends on the source sentences and converter. GPS altitude may be missing or less accurate than horizontal position, and some KML viewers display tracks clamped to the ground unless altitude mode is set appropriately. KML uses WGS 84 longitude, latitude, and optional altitude coordinates; projected survey coordinates must be converted to geographic coordinates before export.