README

SonarGridder: A utility for georeferencing consumer-grade, recreational side-scan sonar files.
© 2021 Jim Birch (AngularFish.net)

╔══════════════════════════════════════════════════════════════════════════════╗
║ Table of Contents (text files in the root directory)                         ║
╟──────────────────────────────────────────────────────────────────────────────╢
║ README:  This file, basics on running the program                            ║
║ BUILDING:Information on how to compile and install the program. Information  ║
║          on how to modify the program to run under different conditions or   ║
║          with different sonar units.                                         ║
║ RUN:     Information on command line options for running the program.        ║
║          Basics for GIS import of files and tips on how to run a survey.     ║
║ LICENSE: The GNU GPL version 2.                                              ║
╟──────────────────────────────────────────────────────────────────────────────╢
║ EXPERIMENTAL: Information on building experimental analyses.                 ║
╚══════════════════════════════════════════════════════════════════════════════╝

A C++ utility for simple georeferencing of Humminbird side scan sonar files. Intended for visual substrate classification using side scan sonar records and a GIS program of your choice. Outputs (regular) TIFF files with world files indicating how to stretch and rotate them onto the map. Corrects cross-track distance and poor gps resolution. Tested with the Humminbird 698ci HD, will likely work with other units of the same generation but may require some modification to the header to adjust the sonar header length and the offsets of particular important sonar header values. TIFF files import into QGIS without difficulty, I have not tested them with any other software.

The approach is to divide the boat's track into segments where the heading is relatively constant, correct the across track distances, write a TIFF file containing the data within each segment, and then write a world file (TFW) describing how to stretch and rotate the image to a map. This approach improves legibility over gridding methods dependent on (GPS-derived) boat heading and radiometric correction at the expense of some spatial accuracy.

This software is a hobby project that I've made available under the GNU GPL version 2.0. It is provided WITHOUT WARRANTY and is probably absolutely loaded with potentially dangerous bugs (I am a biologist after all). Feel free to copy, distribute, or modify the code to your own ends under the terms of the version 2.0 of the GNU GPL. Please see the attached LICENSE file for more information. If you use this software in your own work, please drop me a citation:

  Jim Birch (2021). SonarGridder: A utility for georeferencing consumer-grade, recreational side-scan sonar files. AngularFish.net. URL https://www.angularfish.net/.
  
###############################################################################

Have an idea for an improvement or want to tell me about a bug? Feel free to use the tools provided in the repository, or shoot me an email at jim[ãt]jdbirch.com

###############################################################################
###############################################################################
###############################################################################

Some notes on how this software works:

My study involved surveying an inland waterway with a Humminbird 698ci HD fishfinder. This unit was chosen largely because it is side scanning (side imaging to borrow the manufacturer's parlance) and was the smallest available unit at the time (it was often portaged or run through rapids on a canoe or small aluminum boat, weight mattered). Depth and range are calculated in this unit using data hard-coded into the firmware allowing the user to select seawater or fresh water. The speed of sound for fresh water used by the manufacturer is (I believe) 1436 m/s. Per the manufacturer's specifications, the true RMS power output is 500 watts and the transducer package contains 2 455 khz "side-imaging" transducers (one per side), 1 200 khz high resolution "down-imaging" transducer, and 1 83 khz traditional fish finder transducer. I have configured this software to work with this specific unit in fresh water, but documentation on how to change to additional units is included in the file BUILDING.md.


Updates:

2021-09-17 
-Added path variables to change the output folders. Currently unused.
-Bug fixes: fixed problem with the break point alogrithm, fewer breakpoints are calculated now.