Thread: Yes, another DI question

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.

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

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....??

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....

rvinc, nailed it.....

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

MAYBE ONCE !!!

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.