Subject:
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Re: Sonar question
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Newsgroups:
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lugnet.off-topic.geek
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Date:
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Wed, 20 Oct 2004 21:26:51 GMT
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Viewed:
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1564 times
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In lugnet.build.military, Dave Schuler wrote:
> Can sonar "see" around objects? Can it detect, for example, a sub hiding on
> the other side of a reef or similar underwater obstacle?
Only if there are sufficient holes in the obstacle to allow the sonar to read
objects through them. You should be able to read another object through a
chain-link fence, but not a privacy fence with overlapping boards.
> Here's why I'm asking: The kitchenette in my office is around the corner and
> down a hall, so I can't see when someone's getting coffee. But my pal Brian
> just sneezed mightily in that room, and I heard him clearly.
Sound waves bounce around off other objects, and you could conceivably get some
false readings from echos, so I'd have to guess that the receiver system has
some way of determining when that happens and discarding such readings. Perhaps
it compares the time it took for the return signal with the strength, thus
allowing it to discard anything that was too weak to have been sent with the
most recent ping, or to have been returned from a single object.
> If not sonar, then do we have other sound-based technology that can do this
> kind of thing?
The only way to get accurate readings around objects would be to use some sort
of stereo-sonar, and since sonar systems mounted at opposite ends of a ship
would be effectively receiving the same readings from objects located on or near
their shared axis, you'd need a minimum of three sonar systems (using different
frequencies or coded signals for active sonar so they don't get confused with
each other) in a non-linear layout that are able to receive a return signal from
a given object, so you'd probably need to have a large number of them all over
the ship, and a powerful computer to interpret the various signals into one
combined readout.
> I plan to put sonar on all my spaceships, so I'm eager to learn of its
> limitations.
Well, the most significant limitation in this instance is that sonar, being
sound-based, doesn't work at all in a vacuum. Sound waves are the result of
molecules acting ripples in a pond after you throw a stone in. The more
concentrated the molecules are, the more likely each one is to knock a few
others flying. The less concentrated they are, the more likely it is that none
will be affected at all. It probably doesn't even work very well on land (at
the very least, radar is a vastly superior alternative), which is why the two
most well-known instances of sonar usage are naval warfare (particularly
submarines) and fish-finders.
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Message has 1 Reply:
 | | Re: Sonar question
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| (...) ***snip*** (...) Good info--thanks. It started out as an idle curiosity, but then I really got to wondering about it. (...) That's what I get for leaving out the 8^) You'll probably poo-poo my plan to install a screen door on the airlock, too. (...) (20 years ago, 20-Oct-04, to lugnet.off-topic.geek)
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Message is in Reply To:
| | Sonar question
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| Can sonar "see" around objects? Can it detect, for example, a sub hiding on the other side of a reef or similar underwater obstacle? Here's why I'm asking: The kitchenette in my office is around the corner and down a hall, so I can't see when (...) (20 years ago, 20-Oct-04, to lugnet.build.military, lugnet.boats, lugnet.off-topic.geek)
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