Down Imaging Unit?

[papajoe222]

I've been saving up my gift cards from Christmas and my recent birthday and have enough for an entry level down imaging unit.

My question centers around shallow water use.  My favorite lake's maximum depth is only 12ft. and the average depth is somewhere between six and seven ft. I've read that down imaging units don't work well in shallower water.

Can anyone explain why they don't,and which brand or model works better than others in shallow water situations? Also, as I already have an LCD graph mounted on my counsole and is readable from the front deck, is a graph/down imaging  unit worth the extra bucks?  Thanks 

 

[Wayne P.]

Down Imaging or Down Scan units work just as well as 2D sonar in shallow water.

You just don't have enough depth to display a lot of bottom at any one time with either.

If you know where stuff is, you will get a good look at it. Otherwise you have to do a lot of searching to find stuff.

 

Humminbird DI units and Lowrance DSI units have the same two imaging frequencies. If you want that technolgy in a low end "enty level" unit, the Lowrance DSI units do not have 2D sonar like the Humminbird DI units do.

 

Side Imaging or Structure Scan is the deal in shallow water due to the coverage.

Side Imaging is better though since it has more horizontal coverage for shallow conditions.

[BassnChris]

If you go out to http://www.humminbird.com/ or http://www.lowrance.com/en-US/ they have some pretty good images and explanations of how their sonar works.......just pay particular attention to the depths they are using for a given image.

[Sun Fish]

It really all depends what your looking to spend and what you want.  Down Imaging works fine in shallow water but as Wayne said you will not cover much bottom in shallow water due to the nature of the cone.  If you have enough for a lower end Side Imaging/Down Imaging/GPS unit I would go for that in a heart beat, you can find one for around $700. 

I assume you plan on mounting it on the bow.  If so I think it's a nice benefit to be able to see under your TM as well as under the back of the boat from your console unit all at once.

[Wayne P.]

I have posted this image a few times. The transducer is on the trolling motor. I am following a creek channel (on the right side) looking for fish. There is no way I could know where it was using DI or 2D sonar unless I was above it and scaring any fish I may pass over.

There is a school of small baitfish about 1/2 down the image in the creek (gray blob). Above the baitfish in the creek are some white streaks (those are bass). I caught some of them.

Note the displayed water depth where the boat is and the range I have the unit set to display (numbers on the top right and left). There is 100' of lake bottom from left to right being displayed.

The dark area in the image on each side of the vertical centerline is the water column under the transducer. That is all 2D or DI would be showing at that depth.