Yes, another DI question

Printable View

02-08-2011, 09:14 PM
filletfetish

Yes, another DI question

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
02-08-2011, 10:45 PM
rnvinc

Quote:

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...
02-09-2011, 07:21 AM
talltimber

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.
02-09-2011, 12:01 PM
T Mike

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
02-09-2011, 12:36 PM
filletfetish

I'll just buy one and figure it out myself. I don't think my thinking is translating very well.
02-09-2011, 12:56 PM
Stymie

Quote:

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.
02-09-2011, 01:15 PM
Allan

Quote:

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.
02-09-2011, 01:53 PM
Fish Assassin

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.
02-09-2011, 02:16 PM
filletfetish

Quote:

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?
02-09-2011, 02:24 PM
filletfetish

Quote:

Originally Posted by T Mike

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 know it won't SHOW which side it's on. I'm talking about using deductive reasoning.

DI doesn't work "just like" 2d sonar. The sonar path is much different, that's why I asked about DI...Not SI or regular sonar.

How can my simple mind be some confusing?
02-09-2011, 02:43 PM
Fish Assassin

Fillet I get your point. That reasoning does make sense that it should work. Because your transducer is going to cover the same area may just not be exactly perpendicular to the line of travel. I don't get why it wouldn't work.
02-09-2011, 02:50 PM
T Mike

I think you misunderstood. What I meant to say is it's DI and Sonar are alike in the fact that you can't tell what side of the boat a tree or fish is on.
02-09-2011, 04:32 PM
rescue.tech

Quote:

Originally Posted by filletfetish

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?

I think in theory this would sound plaseable if it wasnt out side (too far left of right) or on the edge of the TD signal. I dont know how slowy you would have to move the TM, it might be slow enough that you would have moved past (in the boat) the item.

But then again I dont even have one yet but I will, and I have been doing as much research as I can.

Clint
02-10-2011, 02:03 AM
rnvinc

Quote:

Originally Posted by filletfetish

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

I like that statement...

Wonder if I could use that on my wife....?? :)
02-10-2011, 02:56 AM
rnvinc

Quote:

Originally Posted by filletfetish

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?

I agree that you have to use some deductive reasoning here...

And I also think that your statement above would be correct...

The experiment in question here is ..."Using DI and Determining where an object is in relation to the xducer IF the xducer is on the TM and able to rotate"....

Look at the pics of the DI/SI sonar beam here....
Understanding Side Imaging - From HB Manual

Remember the DI/SI sonar beam is very wide left to right BUT very thin front to back....

Point 1...If an object is showing on the screen with the xducer orientation pointing forward...then that object is either....90 degrees right of the xducer, 90 degrees left of the xducer, or directly under the xducer....(in that fan shape sonar beam)

Now if you rotate the xducer perpendicular to it's original orientation and that object is STILL showing on the screen...then that object has to be directly (within reason) under the xducer....because....

The portion of the DI beam directly under the xducer is the ONLY common factor between the fan shape sonar beam perpendicular to the xducer AND the fan shape sonar beam in line with the xducer.....

Point 2...(take the same statement as I mentioned above)...
If an object is showing on the screen with the xducer pointing forward...then that object is either....90 degrees right of the xducer, 90 degrees left of the xducer, or directly under the xducer....(in that fan shape sonar beam)

Now, if you rotate the xducer perpendicular to it's original orientation and that object is NO LONGER showing on the screen...then that object has to be either 90 degrees right of the xducer or 90 left of the xducer...and cannot be directly under the xducer ...because....the common factor between the 2 orientation positions of the xducer does not show the image any more....

Then, if you return the xducer to it's original orientation in line and the object returns on the screen....you know that object is definately NOT under the boat but 90 degrees either left or right of the xducer....

Which side...???? I agree with Tmike....That's why you need buy a SI unit.....it will tell you....:)
02-10-2011, 04:31 AM
T Mike

rvinc, nailed it.....
02-10-2011, 10:01 AM
lowe rider

Wonder if I could use that on my wife....?? :)

MAYBE ONCE !!!
02-10-2011, 01:47 PM
Humminbird_Greg

Quote:

Originally Posted by filletfetish

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?

filletfetish,
I understood your original post and will say that: Yes, if you showed a tree in the DI sonar as you passed it and rotated your trolling motor to the right slowly enough and it showed up again, that the tree was to the right of the boat. Since you have already moved past the tree it would have to be either directly behind the transducer, back to the left or back to the right of the transducer. Rotating the transducer to the right would show or eliminate one or more of these possibilities.

I like the Chinese fan analogy. :)
02-10-2011, 04:29 PM
rnvinc

Quote:

Originally Posted by Humminbird_Greg

filletfetish,
I understood your original post and will say that: Yes, if you showed a tree in the DI sonar as you passed it and rotated your trolling motor to the right slowly enough and it showed up again, that the tree was to the right of the boat. Since you have already moved past the tree it would have to be either directly behind the transducer, back to the left or back to the right of the transducer. Rotating the transducer to the right would show or eliminate one or more of these possibilities.

I like the Chinese fan analogy. :)

That's not fair Greg..You can explain it in 1 paragraph where it takes me a page and a half....:D:D

I need to take some of that training that you've been giving at HB...