Thread: Yes, another DI question

Originally Posted by filletfetish

Ok, so this is how I understand it. The sonar beam for DI is more like a thin band vs. an actual circle of a traditional cone. So, lets say we mount the TD on the trolling motor. By rotating the trolling motor, would one be able to better distinguish the structure and even possilby which side of the boat the structure is on?

For example, you're trolling along and a stickup shows up. If you point the trolling motor to the right and the stickup shows back up it wouldn't that mean your structure is on the right side? Does this make any sense? :o

I'm gonna take a shot at this....using your model above that the xducer is mounted on the TM...

This statement takes into account that we are talking about the new DI units that have dedicated crystals for the DI image....not sure how this relates to the older DI image from the SI sonar beam...

The DI sonar beam is a thin slice of the water eminating 90 degrees out of both sides of the xducer and connecting directly under the xducer...kind of like a chinese folding fan opened up .....90 degrees from the line of the xducer...(and 90 degress to the boat travel)..

If a stickup shows up on your DI...then the stickup is either 90 degrees left of the xducer, 90 degrees right of the xducer. or directly under the xducer.....

Now, if you turn the xducer 90 degrees from it's original direction...now that chinese folding fan shaped beam is parallel to the boat travel and eminating straight in front of the boat, straight behind the boat, and connecting under the xducer....

If that stickup still shows on the DI screen...then that stickup has to be directly under the xducer...because ...this portion of the DI beam's folding fan shape is the only common point to the folding fan shaped beam 90 degrees to the boat travel AND in line with the boat travel...

There has been guys doing what you're thinking, with traditional cone ff's, for a long while. They mount a tranducer, for a second bow ff, on the front side of the tm shaft and turn it up to shoot forward. You can then turn the tm to "look" for the next stump, etc. I thought about doing it too, for fishing RF but never did. I think this was what generated the idea behind the wide side and side scan, then eventually the side imaging.
Like rnvinc, I don't think it will work with DI as you can't "point" the beam. You have a slice off both sides and below. You have no way, that I know of, of directing a pointing beam with DI. Now, you could go to 2d/traditional cone and do it, but you would have to have a second transducer with a switch (or maybe not, just select your 2d transducer on the unit?) to do your searching.

DI can NOT show what side of the boat a tree or object is on. The wide beam of DI is larger than the 83khz beam which is 60 degrees and at 30ft it shows 30ft of the bottom. I don't know the exact beam degree with of wide beam DI but if I had to stab it's 75 degrees and quite possibly 50 to 60ft span at 30ft depth? Guesses here tho.... Di shows a tree just like sonar does and sonar isn't capable of showing what side of the boat a tree is on either. This is what makes Side Imaging so powerful. You can not only tell what side of the boat it is on with SI but you can get a good idea of distance as well.

Mike

I'll just buy one and figure it out myself. I don't think my thinking is translating very well.

Originally Posted by T Mike

This is what makes Side Imaging so powerful. You can not only tell what side of the boat it is on with SI but you can get a good idea of distance as well.

Mike

I agree. I have SI on trolling motor. Have been on some fish and the bite turn off. Rotated the trolling motor so SI could find if/where they moved. Sitting still, you don't get a nice picture, but you can tell when it hits the school of fish and know where they are in relation to you.

Originally Posted by Stymie

I agree. I have SI on trolling motor. Have been on some fish and the bite turn off. Rotated the trolling motor so SI to find if where they moved. Sitting still, you don't get a nice picture, but you can tell when it hits the school of fish and know where they are in relation to you.

I do the same thing and put chart speed on 1 or 2.

I thought I understood down imaging to this post came up. Now I can officially say I am thoroughly confused. Thanks rnvinc!!!!!!!!!! But you have a PM!! Thanks.

Originally Posted by rnvinc

I'm gonna take a shot at this....using your model above that the xducer is mounted on the TM...

This statement takes into account that we are talking about the new DI units that have dedicated crystals for the DI image....not sure how this relates to the older DI image from the SI sonar beam...

The DI sonar beam is a thin slice of the water eminating 90 degrees out of both sides of the xducer and connecting directly under the xducer...kind of like a chinese folding fan opened up .....90 degrees from the line of the xducer...(and 90 degress to the boat travel)..

If a stickup shows up on your DI...then the stickup is either 90 degrees left of the xducer, 90 degrees right of the xducer. or directly under the xducer.....

Now, if you turn the xducer 90 degrees from it's original direction...now that chinese folding fan shaped beam is parallel to the boat travel and eminating straight in front of the boat, straight behind the boat, and connecting under the xducer....

If that stickup still shows on the DI screen...then that stickup has to be directly under the xducer...because ...this portion of the DI beam's folding fan shape is the only common point to the folding fan shaped beam 90 degrees to the boat travel AND in line with the boat travel...

I think you're talking about a quick turn at 90 degrees. I'm with you and your fan. If something was on the outer right edge you pick it up. As you go past it, it's no longer in view. If you SLOWLY turn the TD wouldn't it show back up? Wouldn't the fan be coming back acrossed it?