Quote Originally Posted by Sovran View Post
I know that the cone on DI is wide(side to side) but narrow front to back. The question is how do you tell if what is displayed on screen is directly under you or off to one side?
On a DI ... you pretty much don't.

Best guess scenario is to know how wide a spread (angle) your DI beam is, according to whether you're using 455kHz or 800kHz, and understand that whatever is showing on your screen just went through the beam, somewhere.
800kHz = 45deg total angle .... @ 0.8 x water depth
455kHz = 75deg total angle .... @ 1.5 x water depth

I use 800kHz most all the time, and approximate that if I'm in 20ft of water ... then my DI beam is 16ft wide ... or 8ft wide to either side of the transducer. That's why I run 14' rods out in front of me, and shorter rods (8-10') out to the sides. That keeps most of my baits within the confines of the DI beam. I also know that whatever shows on the screen HAS TO be inside that beam, but I can only approximate its location within the width of it.

... cp