.sl3 is the newer sonar log format of Lowrance, Simrad and B&G fish finders. It works like
.sl2 (one frame per ping, with the GPS position, depth, speed and water temperature), but with a
larger frame header and room for more kinds of sonar, including 3D. This viewer reads it directly
and turns it into pictures and files.
How to open an SL3 file
- Copy the
.sl3file from the fish finder's memory card. - Upload it and press Open.
- Look through the sonar pictures, the depth map and the depth profile on the page, and download what you need: the pictures, a GPX track, a KML file for Google Earth and a CSV of every ping.
What is drawn
- 2D sonar, and a second 2D channel when the unit logged one.
- Down scan below the boat.
- Side scan, left and right of the boat's path.
Each gets its own pictures, split into parts of up to 2,400 pings, with a depth or range scale and time and distance marks.
Things specific to SL3 logs
- 3D sonar frames are read past but not drawn. The summary says when a log has them; the other channels of the same log are drawn as usual.
- Diagnostic channels. Some units, especially in debug or calibration logs, add channels that hold no picture. They are listed in the log details and left out of the pictures.
- Date and time. SL3 logs usually store the date and time at the start (in UTC), even in logs with 3D sonar, where it sits in the first 3D frame. The pictures and the GPX then carry real clock times.
- Size. SL3 logs with side scan grow quickly. Very long logs combine neighbouring pings, keeping the strongest echo, so that each channel fits into 24 pictures; the result says when this happened.
If a log was damaged when it was copied, the readable parts are drawn and the result says how much was skipped.
More about what this tool reads and writes: Sonar Log Viewer.