Topic: down imaging readout question

[JSI]

Hello everyone,  finding all the help on this site is very helpful.  Thanks to all for the help and advice!  I am trying to figure out the DI imaging.  If it records in 2d charting then how is there objects to be seen below what would be the bottom of the lake on a conventional 2d sonar?  I assume it is because of the side imaging transducer doing the down imaging but not certain.  Also, how do you know where that object is in relation to boat.  I am a little confused on this feature.  Any help would be very appreciated!  Joe

[rnvinc]

The DI images in the HB SI units is computer generated from the data received in the SI piezoes ...

Just as objects show in an SI image over the bottom detail ...also can objects show below the bottom depth in the DI image ...because this DI image (in a SI unit) is an SI image turned sideways - sort of...
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The DI images in the HB DI units is data received from a dedicated "down pointing" piezo ...

Which do you have ... ??

Rickie

[JSI]

Thanks for response Rickie.  Just bought the Helix 5 SI.  Have not been on the water with it yet. (  kind of tough on boat  to drive on the ice) but soon.  Hopefully!   Just looking at manual and other pictures trying to figure out the concepts of it all.  This is my 1st SI/DI unit and certainly different from what I am use to.  How do you know location of items in relation to boat when this occurs in DI mode?  So if you drive directly over the object it would appear on bottom line but if object outside direct DI cone it will show below the bottom line?  Will the images show below bottom line for both sides of boat and if so how do you know location?  Sorry about all the questions but trying to wrap my head around this unit and its features but this is a great place to do it!  Thanks again .   Joe

[rnvinc]

The DI image in a HB SI unit is definitely a concept that takes some getting used to understand what the DI image is telling you ...

The point on the DI image (In the HB SI unit) where the water column meets the bottom detail is the distance from the xducer to where the bottom is first detected in SI emitted pulse ...

Remember the DI image is the SI data turned sideways-sort of ... So the "start of the bottom detail" in the DI image is the same "start of the bottom detail" in the SI image ...

Any echoes that are closer to the xducer than this "start of the bottom detail" ...will be painted in the water column of the DI image ...just like the echoes in the water column of the SI image ...

Any echoes that are farther away from the xducer than this "start of the bottom detail" ...will be painted "overlaying" the bottom detail ...

Discerning echo position in the DI image ("DI from SI" or "Dedicated DI") cannot be determined ... Because sonar only knows return signal strength and distance ... It does not know direction ...

Just like aiming a wide beam flashlight at a certain target ...that target can be anywhere in the flashlight beam and still be illuminated ... Only your "physical aiming"'the flashlight at that target will put that target into the strongest part of the flashlight beam ...

In sonar ... Only SI can determine direction ...and that's not because SI is smarter ... It's because HB physically "aims" the piezoes to the side ...such that the unit can discern if echo targets are in the "left pointing" SI beam or the "right pointing" SI beam ... Therefore the unit knows whether to paint those echo targets in the the left side of the SI image or the right side of the SI image ...

With SI available in your Helix ...if you see an echo target in the DI view ... The "depth lines" in the DI image will tell you how far that target was from the xducer ...but not direction to that target under the boat ...

Switch to SI to see that same target and the SI image will tell you if that target is left or right of the boat ...

Better yet ... Make "Visible" the DI/SI split view and study the echo targets that enter the display at the right of the DI image and the top of the SI image at the same time ... They are the same target ...

It's just the DI image will tell you distance but not direction ...this is SI's advantage ...

Rickie

[JSI]

Rickie,  That was a great explanation and very appreciated!  It is very helpful.  Without this type of knowledge the learning curve would be much larger.   Did you learn these things from use or otherwise?  Hopefully once I start using unit I will become proficient too!  One other question of you please.  I dont understand all the programs for the computer review of your recordings.  Doesnt HB have a "stock"program  or do you have to find one?  Which do you recommend?  Looks like another entire facet of learning!  Thanks again.  Very nice of you to help me.  Joe

[rnvinc]

There's nary a question I didn't ask myself when I 1st started learning ...

Robert, Chuck, Greg and others here probably thought I was the ultimate OCD aggrivator ...
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HB does not offer any type of viewing programs for the HB data ... They feel the added feature that the unit itself provides suffices for this ... And no need in paying programmers to deal with this ...

Humviewer is probably the most widely used for HB recordings ... I can help you with that if needed ...

There are other viewers like SI View and Yellowfin but I have no experience with them ...

Here is info for the 3rd party software forums ...
http://forums.sideimagingsoft.com/index.php?board=17.0

You can post questions in those specific forums or anywhere in the forum ... Most of us check just about all the forums for new questions needing answered ...

Rickie

[ckd022]

In addition to underwater mapping and waypoint management, the latest version of ReefMaster software also includes a sonar viewer:

http://reefmaster.com.au/

They provide a free 14 day demo of the software if you want to try it out.

Kevin