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Convert SL2 to GPX: Sonar Log Track with Depths (Beta)

Turn the track of a .sl2, .sl3 or .slg sonar log into a GPX file with the depth and water temperature at every point.

Opens: SL2, SL3, SLG
Saves: JPEG, PNG, GPX, KML, CSV

Open

Sonar log
Choose a file… or drop it here
.sl2, .sl3, .slg · up to 200 MB
    Replace file

    The .sl2, .sl3 or .slg file the fish finder recorded, copied from its memory card. One log at a time.

    Options
    Colours

    How echo strength is shown, from weak to strong.

    Units

    Automatic uses feet and miles for logs recorded in or near the United States, and metres elsewhere.

    More options
    Picture format

    JPEG pictures are several times smaller; PNG keeps every pixel exactly.

    Contrast

    Automatic stretches each channel's echo strengths over the whole colour scale, so faint fish and structure show. “As recorded” draws the values the unit stored.

    More pings per pixel give shorter pictures and fewer of them; each pixel keeps the strongest echo of its pings. Very long logs are combined anyway, so that each channel fits into 24 pictures.

    Your files are deleted after processing.

    Every ping in a Lowrance, Simrad or B&G sonar log carries the boat's GPS position. This tool takes those positions out of a .sl2, .sl3 or .slg log and writes them as a GPX track, the format almost every mapping app, GPS program and fitness site reads.

    What the GPX file holds

    • The track, about one point a second, as a single trk. Where the log has a gap (logging paused for over a minute) or the GPS jumped, a new track segment starts, so no straight line is drawn across the lake.
    • Depth and water temperature at every point, plus speed and course, in Garmin's TrackPointExtension (depth in metres, temperature in °C, speed in metres per second, as that extension defines them). Apps that don't know the extension simply ignore it and show the track.
    • Times in UTC, when the log stores the date and time. Older logs and .slg logs don't, and their points have no time.

    Positions are converted from Navico's own map projection to latitude and longitude with seven decimals, which is finer than any fish finder's GPS.

    How to convert

    1. Upload the log and press Open.
    2. Download the .gpx file. The same job also gives the sonar pictures, a KML file for Google Earth, a depth map and a CSV with every ping.

    Good to know

    • GPS glitches. A position that jumps further than a boat can travel is left out of the track; the result says how many were.
    • Depth values are those the unit measured, below the transducer. The 2D sonar's readings are used where the log has them, because side-scan channels often store none.
    • No positions at all? Logs recorded without a GPS fix hold no positions, and then no track can be made; the sonar pictures still work.
    • Waypoints and routes are not in sonar logs; they are in the unit's .usr or .adm files.

    More about what this tool reads and writes: Sonar Log Viewer.

    More with Sonar Log Viewer