I have been using my fishfinder to locate structures on the bottom such as holes and ledges. My question is, how far back behind the boat is the stucture that the screen is showing? When I anchor I always wonder if the hole I am seeing on the screen is right behind the boat, or 20 or 30 feet behind the boat. So even though I've found a ledge or hole, I don't really know if my lure or bait is really over it. I assume that most brands and models would show about the same distance behind the boat -- mine is a Raymarine L-470, and the owners manual doesn't say anything about how far behind the boat that the screen image is.