Thread: Sonar and DI Dont Show Same Thing?

2d is a cone so some of what you're seeing is in front of the unit while the di is flat and what you are seeing is in the rear view mirror? Depending on which unit you have the 2d cone may differ in size, hugely. 2d is often in 83/200 khz which means 60/20 degree beams but the di units seem to only have 2d in 200/455 khz which means 20/16 degree beams. The SI units seem to have 200/83 2d sonar, have di as well so why not the di? I'm considering some of these same issues so thanks for the post. What unit do you have?

(DI is a thin beam but at 75 degree angle so it's wider than the 60 degree 2d, way wider than the 20 degree 2d)

Another thing to consider is that in the cone shaped 2d format the object is getting pinged multiple times as it moves through the wider cone while in the thin fan shaped DI mode the object gets far fewer pings so the image may not display with the same bulk.