Down Imaging Question???

[iceintheveins]

Does down imaging see as far out as a traditional 20 degree or so sonar cone? Or is it only right below the boat, and do I need traditional sonar as well to accompany it?

[papajoe222]

My understanding is that you will get an image at whatever depth as long as you have the depth range set that deep or deeper, or on auto. As long as a signal is being returned to the transducer, you'll get a bottom reading.

Most units are dual units in that they have the capability to show either a normal graph type image, a down image 'picture, or both at the same time. The advantage to this is it's much easier for you to interpret a traditional sonar image when you have the other below or next to it. I don't know if a down imaging unit displays in real time, and that would be the only reason to really 'need' traditional sonar as far as I can determine.

I've been looking into adding one of he Lowrance units to my trolling motor, so I'm a little inquisitive about this myself.

[Jig Man]

The way it was explained to me is down scan shows slices in the water instead of a cone like 2d sonar does. I know that it reaches out to the side some but have never been told how far because fishing on bluffs it will show ledges that actually aren't under the boat but out to the side.

I have been running hds units for a couple of years and have gotten to the point that I don't run 2d sonar except when I am driving the boat at plane speeds. I have to do this as the stern down scan ducer comes out of the water and I wouldn't get a reading.

Here is a school of white bass I saw last winter on Bull Shoals.

[Wayne P.]

Humminbird Down Imaging with a Side Imaging unit has three selectable widths. The widest setting is about what the 83 kHz 2D pulse covers.

The narrowest setting is about what the 200 kHz covers, and the medium setting is about midway of the two.

Humminbird Down Imaging units have 75 degees of coverage with 455 kHz and 45 degrees of coverage wth the 800 kHz for the Down Imaging function.

For the 2D sonar they have a 25 degree cone with the 200 kHz and a 16 degrees cone with 455 kHz.

A Down Scan only unit is basically worthless for fishing, it is a good search tool though and makes a good companion for a 2D sonar unit.

[Wayne P.]

My understanding is that you will get an image at whatever depth as long as you have the depth range set that deep or deeper, or on auto. As long as a signal is being returned to the transducer, you'll get a bottom reading.

Most units are dual units in that they have the capability to show either a normal graph type image, a down image 'picture, or both at the same time. The advantage to this is it's much easier for you to interpret a traditional sonar image when you have the other below or next to it. I don't know if a down imaging unit displays in real time, and that would be the only reason to really 'need' traditional sonar as far as I can determine.

I've been looking into adding one of he Lowrance units to my trolling motor, so I'm a little inquisitive about this myself.

Whether imaging sonar or traditional sonar, both are recorded images on the display with the first row of screen pixels being current data and the rest is history. The imaging technology does not use a camera, it uses a sonar transducer.