Author Topic: Down Imaging (Read 14260 times)

bmft01 · « **on:** December 16, 2010, 09:46:46 AM »

Hi HB Staff,
I have not been able to ascertain if the HB Down Image is formed by unique soundings or is made of a composite of side imaging data represented in the format/view of a down image. In which case no new information is obtained!? Can someone educate me?
Frank

Wayne P. · « **Reply #1 on:** December 16, 2010, 10:22:21 AM »

The Down Imaging feature of a Side Imaing unit uses the same frequencies and the same transducer crystals to form the images. The unit just interprets and displays the same data differently.

sonar2000 · « **Reply #2 on:** December 16, 2010, 10:57:33 AM »

Wayne is correct with the crystals and frequency.
Look at a recording of a side image run and paticularly the left side image. Then look at the down imaging display. If you were to rotate the left side image display 90 degrees to the left (in other words stand it up) then you will see an almost exact Down image display.
Humminbird does not explain the down image very clearly with respect to how it is created.
I suspect a lot of influence is from the left transducer.
Chuck

Humminbird_Greg · « **Reply #3 on:** December 16, 2010, 02:20:05 PM »

Chuck,
It is my understanding that it is equal parts of the left and right Si sonar beams. You may be seeing more left Si sonar influence due to the angle of the Si transducer or for some reason the left Si sonar on your unit is stronger.

Bmft01,
Do not get the Di sonar for the Si units confused with the Di sonar from those new for 2011 units that have “Di” in their model names. This Di sonar is taken from a single Di only sonar element and requires a different transducer that comes with the unit. Less coverage area and the inability to change the coverage area like you can with an Si unit but should be a clearer looking image (versus the Wide setting on the Si units).

sonar2000 · « **Reply #4 on:** December 16, 2010, 05:00:35 PM »

Greg, I will play with this more when the weather gets back to normal. Also will check with several of the other units near me and compare to my runs to see if we can figure out the left influence. I know from past runs that a lot of equal distance objects in SI when compared to the DI are visuals from the left beam but missing from the right beam. I dont think it is beam angle as the SI shows the objects where the DI does not.
This is not to say that electronics being what they are could be based on the transducer strength when analyzed by the HB software.
HB does not let us see the algorithoms or code that produces the displays so we can only ASSUME from the visual displays.
HB is not alone in propriatiary code as this exists in all forms of products that use computers.
It would be nice to know though....
Chuck

bmft01 · « **Reply #5 on:** December 17, 2010, 12:27:56 PM »

Great replies, thank you to all. I have a much better understanding of the down imaging software.
Frank

Saint · « **Reply #6 on:** January 19, 2011, 01:20:22 PM »

Almost ready to pull the trigger on the 898. Is the software for the 898 and 998 the same for this downimaging? Anyone get an answer to the left side image being translated to be the down image? I'm starting to doubt buying the side imaging for salmon fishing. We usually fish depths of 90-150 ft. I'm concerned with being to deep for this technology.

Thanks for any input

sonar2000 · « **Reply #7 on:** January 19, 2011, 01:35:33 PM »

If you are looking solely for "fish" image you might be better using the 2D instead of Down Imaging. Particularily at that depth...
Chuck

Saint · « **Reply #8 on:** January 19, 2011, 01:56:20 PM »

I've been wondering the same thing. Having the higher resolution of the 400 and 800 kHz would be nice though. I know I want a Humminbird unit but I don't want to pay for something that won't work with the fishing I'm doing. I'd rather buy a larger unit then waste the money. But... if the down/side imaging will work, I'm excited to pick one up. Seems like the down imaging will work more for what we are doing but then again I've never seen or used one of these units. Obviously the more we can see down there the better. 200/83 sonar just seems so cryptic. It's hard to tell what you might be seeing, seaweed, fish, log, boat, crab traps, bait ball, you get the idea.

Wayne P. · « **Reply #9 on:** January 19, 2011, 04:48:41 PM »

Down Imaging in combination with 2D will let you know what is "down there"

Here is some weeds and the Down Imaging can distinguish the individual weed stems.

Wayne P. · « **Reply #10 on:** January 19, 2011, 04:59:37 PM »

Down Imaging will show predator fish in a group of baitfish and make them stand out when next to a small bush. I caught two of those bass.

RGecy · « **Reply #11 on:** January 19, 2011, 06:25:49 PM »

I have to say, that for fishing, the combination of 2d soanr and Down Imaging is very powerfull. Sometimes the fish will not show up on the 2d sonar under brush or thick grass, but in the DI view show up very clearly.

I think it was a very smart move on HB's part to incorporte the new DI transdcuers in to the lower series units.

Robert

Humminbird_Greg · « **Reply #12 on:** January 22, 2011, 12:39:23 PM »

Just remember though that the Di sonar for the Si units and the new DI sonar for the 2D only units is different:
The Di sonar in the Si units is made up of information from both the left and right Si beams. It can be set to show everything that appears in both beams, only what appears in both beams and a combination of those.
The DI sonar in the new HD DI units is from a separate transducer element. It covers a narrower area than does the Si sonar and works to a deeper water depth (250 feet). It is really just a very narrow (front-to-back) 2D sonar beam.

rnvinc · « **Reply #13 on:** January 22, 2011, 01:32:38 PM »

Quote from: Humminbird_Greg on January 22, 2011, 12:39:23 PM

Just remember though that the Di sonar for the Si units and the new DI sonar for the 2D only units is different:
The Di sonar in the Si units is made up of information from both the left and right Si beams. It can be set to show everything that appears in both beams, only what appears in both beams and a combination of those.
The DI sonar in the new HD DI units is from a separate transducer element. It covers a narrower area than does the Si sonar and works to a deeper water depth (250 feet). It is really just a very narrow (front-to-back) 2D sonar beam.

Greg...for those that may be interested...(including myself)

Please explain which actual DI setting goes with each of your 3 despriptions...

reddog · « **Reply #14 on:** January 22, 2011, 10:03:56 PM »

I believe that there is equal input into the DI image. but in order to confirm, one would have to make your pass over the target equal distances from the left and the right.

This is as close as I have for now.

Humminbird_Greg · « **Reply #15 on:** January 25, 2011, 08:56:48 AM »

Quote from: rnvinc on January 22, 2011, 01:32:38 PM

Greg...for those that may be interested...(including myself)

Please explain which actual DI setting goes with each of your 3 despriptions...

The Narrow setting (Down Imaging Beam Width menu) shows only those things which are in both the left and right Si sonar beams.

The Wide setting shows everything shown in the left and right Si sonar beams.

The Medium setting is somewhere in between these. I have not heard of an understandable explanation for this setting other than it involves algorithms and is somewhere between the other two settings.

troutfanatic · « **Reply #16 on:** January 29, 2011, 10:36:15 PM »

Are any one of these clearer than the others?

Wayne P. · « **Reply #17 on:** January 30, 2011, 07:58:58 AM »

The three choices have the same image clairty.
The way it seems to me with the beams selections is the Narrow is close to the bottom width of the 200 khz cone, the Wide is close to the bottom width of the 83 khz cone, and the Medium is between those two.

felvic · « **Reply #18 on:** March 18, 2011, 05:38:15 AM »

Quote from: Humminbird_Greg on January 25, 2011, 08:56:48 AM

The Narrow setting (Down Imaging Beam Width menu) shows only those things which are in both the left and right Si sonar beams.

The Wide setting shows everything shown in the left and right Si sonar beams.

That's mean the two beams (left and right ) overlaps on 20° cone ( 10° on left, 10° on right )?

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Author Topic: Down Imaging (Read 14260 times)

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