Sonar Quiz #18

[rnvinc]

Which way does this xducer need adjusting ...??

What clue(s) in the image gives it away ...??



Rickie

[kosmo]

That's the way that I run my transducer

[cache22]

Pointed forward.... front half of arches are truncated. To get true arches raise back end of TD a little. BTW didn't see the answer to that last quiz.

[Redge]

Pointed forward.... front half of arches are truncated. To get true arches raise back end of TD a little. BTW didn't see the answer to that last quiz.

X2!

[rnvinc]

BTW didn't see the answer to that last quiz.

I'm letting Quiz #17 ride for a while ...

Someone may have input for discussion yet ...

Rickie

[slabbacks]

Interesting I would have thought the back of the transducer was lifted giving longer arches on the front end. Learn something new every day with you guys

[Humminbird_Greg]

I think you are right slabbacks but it all depends on what you are calling the “front end” of the arch. Is that the leading (left side of the arch) or the trailing (right side of the arch) side?
Remember that the sonar updates left to right so the left side of the arch is the leading edge and the right side is the trailing edge.
With the back end of the transducer higher (transducer is pointed backwards); you would see a shorter leading edge and a longer or more pronounced trailing edge which is what is being shown in the picture.

[rnvinc]

I pulled this diagram out of a Lowrance installation manual...



Revisiting the image in the OP below ... We see that the echoes are consistantly only showing the right half of the arch (trailing off to the right)...



So this is an indication that the xducer is riding "tail high" ....
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Now...to get a better understanding of how and why this takes place....let's take a look at the math involved in this scenario....(we all love math now don't we ...??)

We know that echos painted on the display are a representation of the "Range" from the xducer to the target...

It is the difference in this "Range" to the target as it passes thru the sonar cone that gives us the "arch" we see on the 2d image display...

In the diagrams below I have divided the fish passing thru the sonar beam into 3 separate diagrams...:

(The sonar cone is drawn as green to represent a "tail high" orientation of the xducer mounting)...

Diagram 1 is the fish entering the sonar cone ...
Diagram 2 is the fish centered in the sonar cone ...
Diagram 3 is the fish leaving the sonar cone....

(The displayed 2d image is depicted in the lower right of each diagram...to show the rendering of the target echo's arch into the 2d image as the fish passes thru the sonar cone)


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Rickie

[kosmo]

That's good stuff rickie, thanks.

[arkcrappie]

This is so much more interesting than school ever was. I actually don't mind sitting and reading this stuff (unlike history). Good stuff guys!