So far there are 3 different types of files from Lowrance, SL2, SL3 and SLG. They are similar, bordering to identical.
Much kudos to openstreetmap.org project and their SL2 documentation page http://wiki.openstreetmap.org/wiki/SL2
Some hints and info about slg can be found at http://www.geotech1.com/forums/showthread.php?11159-Lowrance-MCC-saved-data-structure
Some information found in https://www.memotech.franken.de/FileFormats/Navico_SLG_Format.pdf
THE DOCUMENTATION IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
- https://github.com/kmpm/node-sl2format
- https://github.com/Seva-coder/FindFish
- https://github.com/risty/SonarLogApi
- https://github.com/Chris78/sl2decode
- https://github.com/opensounder/python-sllib
| type | definition |
|---|---|
| byte | UInt8 |
| short | UInt16LE |
| int | Int32LE |
| uint | UInt32LE |
| float | FloatLE (32 bits IEEE 754 floating point number) |
| flags | UInt16LE |
8 byte header, then a series of blocks/frames as described below.
| offset | bytes | type | description |
|---|---|---|---|
| 0 | 2 | short | format[1] |
| 2 | 2 | short | version[2] |
| 4 | 2 | short | blocksize[3] |
| 6 | 2 | short | unknown/always 0 |
-
format[1] 1 = slg, 2 = sl2, 3 = sl3
-
version[2] 0= ex HDS 7, 1= ex. Elite 4 CHIP
-
blocksize[3] 1970=Downscan #b207, 3200=Sidescan #800c
-
Format 1 format-1.md
-
Format 2 format-2.md
-
Format 3 format-3.md