I have been asked to investigate if Lowrance SL2 (side-scan sonar) format can be put into maps for reports.

As I understand it the SL2 format comprises 3 "bands" left-down-right and is more of a video than raster. If the sonar log file has been captured previously can it be opened and converted to a raster and then viewed - prefer with georeference?

The current thoughts are to screen-shot the log using the sonar log viewer and then georeference but having seen the contents of these files I don't like the chances of getting similarity enough to georeference.

  • Disclaimer: I'm out of my depth (ha!) so just offering suggestions for information. Did you see this page on decoding the sl2 format? A quick search came up with a few software/service options, such as the one Ray suggests. Did you see this other question on sonar data? – Chris W Jul 3 '14 at 5:50
  • Thank you for the links @ChrisW. I'm on holidays now and will look into them when I get back to work. Sonar isn't my thing either... I hadn't thought about it until I got asked. I'm kind of keen to get good bathymetry around my fishing spots though; if I am helpful they might use one of my fishing spots as a test area. – Michael Stimson Jul 4 '14 at 4:31

What type of habitats need to be typed? BioBase (www.cibiobase.com) generates GIS grid (kriging) outputs (depth, submerged vegetation, and bottom hardness) for the downlooking 200 khz broadband channel which is often recorded in .sl2 files.

If the investigator can navigate over the area of interest, BioBase will automate the processing of high resolution maps.


  • Thank you Ray, from the sounds of it the data needs to be uploaded to the cloud and then mapped from there.. is there an option for local data and if not is the data still private on the cloud? Some of the areas we map may be sensitive and general public access of the data prior to the report would breach privacy arrangements with our client(s) and leave us open for litigation. Do you know what the price of a single license is likely to be? – Michael Stimson Jul 2 '14 at 21:55

Reefmaster software allows you to import several .SL2 Files, and merge them. You can then export to kml and other GIS compatible formats.

  • Answer in more detailed. – BBG_GIS Nov 19 '17 at 17:53

Likely an answer waaay to late to help the OP but in case anyone else stumbles across this in search of an SL2 reader there's now a standalone app : https://gitlab.com/hrbrmstr/sl2json (requires compilation) : and an R package : https://gitlab.com/hrbrmstr/arabia : for reading SL2 files.

The app streams out nsjson records and the R package returns a data frame.

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