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Convert SL2 and SL3 Sonar Logs to CSV (Beta)

Every ping of a Lowrance sonar log as a row: time, position, depth, speed, course, heading, water temperature and more.

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.

    A sonar log is a long list of pings, and each ping carries a time, a position and the unit's readings. This tool writes them all out as a CSV file that Excel, Numbers, LibreOffice, R or Python read directly, from .sl2, .sl3 and .slg logs of Lowrance, Simrad and B&G units.

    The columns

    One row per ping, in the order the pings are in the log:

    • frame, channel and channel_name (2D sonar, down scan, side scan…), frequency
    • log_time_s: seconds since logging started, and time_utc when the log stores the date
    • latitude and longitude in decimal degrees
    • depth, keel, and the range_top and range_bottom the ping covers
    • gps_speed, water_speed, course_deg, heading_deg
    • water_temp and altitude
    • samples (echo values in the ping) and file_offset (where the ping is in the log)

    The unit is part of each column name, such as depth_m or depth_ft, gps_speed_km_per_h or gps_speed_mph, water_temp_c or water_temp_f. Choose metres or feet on the form; the automatic setting uses feet for logs recorded in or near the United States.

    Working with it

    • Filter by channel. A unit logging 2D sonar, down scan and side scan writes a row for each, interleaved. For a depth profile, keep the rows of the 2D sonar: side-scan pings often have no depth.
    • Empty cells mean the log has no value there: no bottom found, no temperature sensor, or no paddle wheel for water speed.
    • Decimal points. Numbers use a point. In a spreadsheet set to a comma as the decimal separator, import the file with the point as separator instead of opening it by double-click.

    Also in the result

    The same job draws the sonar pictures and writes a GPX track with depths, a KML file for Google Earth and a depth map, so the CSV is there for your own charts and statistics rather than for looking at the sonar.

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

    More with Sonar Log Viewer