Thread: If it ain't broke, don't fix it

Dock ??? What dock ?? All I see are trees and a ball of fish

(or are those "match" shaped images the dock supports/posts ?? And if so, why do they not go all the way up to the prop wash strip ??)

... cp

Originally Posted by CrappiePappy

(or are those "match" shaped images the dock supports/posts ?? And if so, why do they not go all the way up to the prop wash strip ??)

... cp

I would guess those are indeed the dock posts starting in the left water column at about the 18ft SI Range line ...

This would mean the dock was a little over 18ft from the xducer before the sound pulse actually 1st contacted the dock posts ...

Echoes of a vertical structure all the way to the centerline would mean the xducer would be right up against the dock posts = shorter distance to xducer ...

Rickie

Thanks for bailing me out, Rickie.. Gene usually has to do that..

Originally Posted by rnvinc

I would guess those are indeed the dock posts starting in the left water column at about the 18ft SI Range line ...

This would mean the dock was a little over 18ft from the xducer before the sound pulse actually 1st contacted the dock posts ...

Echoes of a vertical structure all the way to the centerline would mean the xducer would be right up against the dock posts = shorter distance to xducer ...

Rickie

OK ... I can grasp that. But, why would the fish or trees show up "above" the dock posts ?? If the SI signal is 90deg/side, why wouldn't it show a solid object (that rises above the water's surface) reaching all the way to the center line/prop wash image ?? Don has the range set at 50' ... so if the dock is around 20' away from the transducer, it would seem that it should show the posts going all the way to the surface (or at least a image above the ball of fish).

Had I only seen the screenshot, and not been told of a dock being there, I would never have suspected there being a dock in the image ... and probably figured the "matchsticks" images to be tree trunks or posts from a dock that no longer exists.

... cp

Those are nice shots Don, but you do know if those fish ever find out you are not running the latest depth finder, they will not bite.

CP,IT IS NOT UNUSAL TO GO BY A BRIDGE SUPPORT THAT COMES OUT OF THE WATER AND SEE FISH OVER TOP OF BRIDGE SUPPORT ON SCREEN IN SI,DI OR 2D. IF THE FISH IS 8 FEET FROM DUCER UNDER BOAT OR TO THAT SIDE IN 2 FEET F WATER,AND U ARE 12 FEET FROM SUPPORT WHEN U GO BY IT WITH DUCER IT SHOW THE FISH 8 FEET DOWN AND PILLOW AT TOP OF WATER TOPPING OUT AT 12 FEET,U HAVE TO UNDERSTAND IT MEASURES DISTANT,I LEARN THIS BY GOING BY BRIDGE MANNY TIMES TO HELP ME UNDERSTAND WHAT IT WAS TELLING ME.IT IS ACCURATE BUT OUR UNDERSTANDING SOMETIMES IS NOT,HOPE THIS DO NOT CONFUSE U TOO MUCH

Originally Posted by CrappiePappy

OK ... I can grasp that. But, why would the fish or trees show up "above" the dock posts ?? If the SI signal is 90deg/side, why wouldn't it show a solid object (that rises above the water's surface) reaching all the way to the center line/prop wash image ?? Don has the range set at 50' ... so if the dock is around 20' away from the transducer, it would seem that it should show the posts going all the way to the surface (or at least a image above the ball of fish).

Had I only seen the screenshot, and not been told of a dock being there, I would never have suspected there being a dock in the image ... and probably figured the "matchsticks" images to be tree trunks or posts from a dock that no longer exists.

... cp

The dock posts are approx. 18ft from the xducer ... Therefore painting the structure as starting approx. 18ft to left of the center line ...

As the left SI sound pulse is traveling toward the dock posts ... The first 18ft of its travel is merely thru water with no reflected echo ...therefore black (no data) between the centerline and the Left SI 18ft Range line ...

It's not until the sound pulse has traveled 18ft from the xducer that the sound pulse 1st contacts the dock posts ... Then starts painting the dock post reflection ...

The fish school is more rounded ...

Some of the individual fish (of the rounded school) are closer to the xducer than the dock posts are ...

The individual fish (of the rounded school) that are closest to the xducer would be painted closer to the centerline ...

I agree ... Vertical posts are difficult to discern in an SI image ...

Rickie

Originally Posted by rnvinc

The dock posts are approx. 18ft from the xducer ... Therefore painting the structure as starting approx. 18ft to left of the center line ...

As the left SI sound pulse is traveling toward the dock posts ... The first 18ft of its travel is merely thru water with no reflected echo ...therefore black (no data) between the centerline and the Left SI 18ft Range line ...

It's not until the sound pulse has traveled 18ft from the xducer that the sound pulse 1st contacts the dock posts ... Then starts painting the dock post reflection ...

The fish school is more rounded ...

Some of the individual fish (of the rounded school) are closer to the xducer than the dock posts are ...

The individual fish (of the rounded school) that are closest to the xducer would be painted closer to the centerline ...

I agree ... Vertical posts are difficult to discern in an SI image ...

Rickie

Rickie, I hope you are keeping a book on SI/DI questions & answers. If you are, please save me a copy..