I can chime in as another long time sidescan sonar operator. Started with the old double helix/revolving drum wet paper recorders, and the last one I used was the EG&G digital version. Also used Klein, Edo, Wesmar, Dowty, O.R.E. and GeoAcoustics systems. mostly 100 kHz, but also some of the 500 kHz systems, too. 40 years of finding and mapping and tracking stuff in the ocean. I was an employee of EG&G for 10 years, with O.R.E. 19 years, and did a lot of consulting as well. I've found lots of boats, cars, aircraft, anchors and military hardware
. Lots of route survey
work, pipeline inspection
, too much to list it all.
can be really good if your wreck is a good reflector and is sitting in an area without a lot of other good reflectors. Just about any pile of debris on a smooth sand bottom will stick out like a sore thumb. But if the bottom is really rocky, it starts to get a little more difficult. If you're looking for a boat in an area of boulders, it starts getting hit or miss. Sidescans cannot tell you anything about the material, only their reflectivity. Things with air in them work really well as acoustic reflectors. Any time acoustic energy passes through the interface between two materials with different sound velocities, some of that energy is reflected.
Interpreting sidescan data can be difficult under some conditions. When it's easy, it's REAL easy, but when it's not it's frustrating.
It might be easier to start the survey
with a towed magnetometer if you have the route
mapped out. Almost any boat will have some significant ferrous material in it. Anchors, engine
blocks, things that will give you a hit on a maggie. Then go back and either dive those locations, or rent an ROV and fly that down for a look.
If you're looking for someone who runs sidescans for a freelance living these days, Gary Kozak from Klein is still active and one of the best. I was just reading about him finding a submarine recently.