Quote Originally Posted by fastfish View Post
I checked out the Helix 5 DI...sounds pretty good actually!!..hmm..maybe can talk wife into one for birthday in September!! The echo will show me huge piles of grass on the bottom..but most of the time everything seems to be flat..I'm not sure if it's the lake or the finder....I'm pretty sure the depths are right on with it..so until I get a new one I'll just have to take clues from the shoreline s as to cover and fish the drops that do seem to be clear on the echo.
You just have to understand how much water column your 2d cone is showing, and how much bottom real estate is being shown. A 20deg cone will show a circle of bottom approx. 1/3 the width in feet as the depth in feet .... or a 7ft wide circle in 21ft of water. A wide beam 60deg cone is a 1:1 factor ... or a 10ft wide circle in 10ft of water. BUT .... in either case the sonar ping beam is still in a cone shape, so the water column shown is narrow at the top and gets wider with depth.

A DI unit uses a fan shaped sonar ping, approx. 45deg or 75deg angle, but only a few degrees thick. It fans out to the sides of the transducer at right angles, so if it's mounted on your trolling motor ... you must be aware of "where" your trolling motor is pointing, to know what swath of water you're seeing on your screen.

Having had 2d sonar units since the early 1970's, up until just a few years ago, when I got a Lowrance Elite 5 DSI, I pretty much just used them to see depth, drops, and the occasional "blob" that was likely indicating cover of some type. Since having the Down Image unit (no 2d capabilities) I can now pretty much tell exactly what I'm seeing below me, since the unit will show me a near picture quality image of what I'm going over. No fish "symbols" or "blobs" of pixels to interpret (or misinterpret), just a on screen image that leaves little to the imagination or necessity of interpretation. Like this :

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You might want to compare the Lowrance Elite 4x Chirp or 4x HDI to any other unit you have your eye on. And if you don't really want color screen images, look at the Mark series Lowrance units.

... cp