Can someone please explain what exactly is happening inside that usually dark center line on the SI return? Be as technical as you want in the reply.
Dont have alot of time right now.
but, the dark area is exactly the same thing as you see in 2D sonar. It is the water column turned on its side in relation to the boat instead of being verticle. The same fish show up in the SI water column (and more) as do in conventional sonar.