Thanks for your help. I'm trying to understand what and where I'm seeing on my graph. The two links provided seem to give quite different information. Kozmo's photo gives a formula: At 800kHz: it says the width of the cone is .83 x depth. That would indicate to me that at ten feet, I would see an image on the graph that is 8.3 feet wide. Bassfisher1's depth chart shows that at 10', There is actually three zones being covered. The side coverage is 19', the Down Image is 9' and total coverage is 47'. The only number that seem to jive is the 9' down image number. Is it correct to assume that at 10' I'm looking at a field that is just slightly less wide than the depth? Also, if the front to back cone is only 3 degree or so. What I'm seeing is pretty much directly beneath the back of the boat. So if I wanted to throw a marker of float to mark a spot identified on the DSI unit, I would want to toss it overboard just as it appears on the monitor on the left side of the screen.