Vigil

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gareth evans

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Aug 30, 2021, 2:48:09 PMAug 30
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Not sure in which group to pose this question ...

After watching the first episode of Vigil last night, I
wonder what are the multiple waterfall displays shown
in the submarine's control room?

Are they audio frequency spectra?

If so, why so many similar displays?

Unknown

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Aug 30, 2021, 4:00:06 PMAug 30
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gareth evans used his keyboard to write :
> Are they audio frequency spectra?

Yes! They identify other sub models by the noise signature they make.

Scott Lurndal

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Aug 30, 2021, 6:15:30 PMAug 30
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gareth evans <headst...@yahoo.com> writes:
>Not sure in which group to pose this question ...
>
>After watching the first episode of Vigil last night, I
>wonder what are the multiple waterfall displays shown
>in the submarine's control room?
>
>Are they audio frequency spectra?

SONAR.

>
>If so, why so many similar displays?

I could tell you, but then...

Cursitor Doom

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Aug 30, 2021, 7:37:36 PMAug 30
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Not just other models, but often individual subs within a number of
identical models. This kind of precise discrimination is a real
concern for the Trident subs given their critical role and the fact
there are only 4 of them in total!
--

"In short, the Communists everywhere support every revolutionary movement
against the existing social and political order of things. In all of these
movements, they bring to the front, as a leading question, the issue of
private property ownership."

- Marx and Engels, The Communist Manifesto

newshound

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Aug 31, 2021, 7:22:06 AMAug 31
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You often see images, sometimes a bit blurred, in submarine
documentaries. I'd love to have an explanation of what they are actually
showing.

I think that type of display has been around for a long time, presumably
they rely on the human ability to do quite extraordinary pattern
recognition, and sifting signals from noise. I guess these days with
real time processing power plus AI there will be electronic systems
operating in parallel

I'm amazed how well music tuner apps in smartphones perform, also there
is an app that records birdsong, does an FFT (presumably) on a sample,
and goes off somewhere and gets an ID.

As one of the commentators noted, the days of the simple "optical path"
periscopes are long gone.

Ahem A Rivet's Shot

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Aug 31, 2021, 9:00:03 AMAug 31
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On Tue, 31 Aug 2021 12:22:03 +0100
newshound <news...@stevejqr.plus.com> wrote:

> As one of the commentators noted, the days of the simple "optical path"
> periscopes are long gone.

See periscope, point laser sighted rifle at it, don't bother firing.

--
Steve O'Hara-Smith | Directable Mirror Arrays
C:\>WIN | A better way to focus the sun
The computer obeys and wins. | licences available see
You lose and Bill collects. | http://www.sohara.org/

Dennis Boone

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Aug 31, 2021, 11:16:42 AMAug 31
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> Are they audio frequency spectra?

For a submarine, (some of?) the interesting variables are time,
frequency, direction. In common waterfall displays, e.g. those used in
radio, the typical axes are frequency and time, with color coding for
signal strength. This sort is useful for identification of a noise
source. But it's easy to imagine, and I have seen in movies (with the
usual "Hollywood" errors), angle as one of the axes.

Obviously in passive sonar, distance has to be estimated based on other
knowledge -- water characteristics, the sound profile of the source,
etc. If you have good enough data, you can make distance one of the
axes.

De

Niklas Karlsson

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Aug 31, 2021, 2:39:56 PMAug 31
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On 2021-08-31, Dennis Boone <d...@ihatespam.msu.edu> wrote:
>
> Obviously in passive sonar, distance has to be estimated based on other
> knowledge -- water characteristics, the sound profile of the source,
> etc. If you have good enough data, you can make distance one of the
> axes.

I have it on good authority (a former sonarman) that submarines do not
determine distance directly from sonar. They perform TMA (Target Motion
Analysis). You can determine speed from propeller noise and can then
figure out how far away a target is by how it moves.

Niklas
--
When being picked up against their will by larger creatures, cats and human
children share not only the ability to temporarily sprout extra limbs and
perform incredible acts of contortionism, but also to temporarily increase their
weight.

Peter Flass

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Aug 31, 2021, 3:14:28 PMAug 31
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Niklas Karlsson <nikke.k...@gmail.com> wrote:
> On 2021-08-31, Dennis Boone <d...@ihatespam.msu.edu> wrote:
>>
>> Obviously in passive sonar, distance has to be estimated based on other
>> knowledge -- water characteristics, the sound profile of the source,
>> etc. If you have good enough data, you can make distance one of the
>> axes.
>
> I have it on good authority (a former sonarman) that submarines do not
> determine distance directly from sonar. They perform TMA (Target Motion
> Analysis). You can determine speed from propeller noise and can then
> figure out how far away a target is by how it moves.

Interesting. This is the opposite of how I would expect it to work. These
days I would expect a lot of analysis is computerized, it seems like a good
application.

--
Pete

J. Clarke

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Aug 31, 2021, 4:00:27 PMAug 31
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Target motion analysis was in use during WWII. Google "is-was
submarine" and you'll find a lot of information.

Fredxx

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Sep 1, 2021, 4:55:07 AMSep 1
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On 30/08/2021 23:15, Scott Lurndal wrote:
> gareth evans <headst...@yahoo.com> writes:
>> Not sure in which group to pose this question ...
>>
>> After watching the first episode of Vigil last night, I
>> wonder what are the multiple waterfall displays shown
>> in the submarine's control room?
>>
>> Are they audio frequency spectra?
>
> SONAR.

No, they will be passive listening devices. Frequency in the x
direction, amplitude set by brightness, and over time as it falls down
the screen.

>>
>> If so, why so many similar displays?
>
> I could tell you, but then...

To provide directional information?


Niklas Karlsson

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Sep 1, 2021, 5:34:10 AMSep 1
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On 2021-08-31, Peter Flass <peter...@yahoo.com> wrote:
> Niklas Karlsson <nikke.k...@gmail.com> wrote:
>>
>> I have it on good authority (a former sonarman) that submarines do not
>> determine distance directly from sonar. They perform TMA (Target Motion
>> Analysis). You can determine speed from propeller noise and can then
>> figure out how far away a target is by how it moves.
>
> Interesting. This is the opposite of how I would expect it to work. These
> days I would expect a lot of analysis is computerized, it seems like a good
> application.

Yes, there's a lot of computerization, but they still do a lot of manual
work as well. If nothing else, to keep up the skill in case the
automatic systems fail.

Niklas
--
I was commenting to a co-worker just yesterday that I find the last 20% of
projects the most interesting and a former manager, the first 20% of projects,
so we would always compromise and work on the middle 60% of the project and
both of us would be miserable. -- Russ Allbery

Niklas Karlsson

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Sep 1, 2021, 5:35:02 AMSep 1
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On 2021-09-01, Fredxx <fre...@nospam.co.uk> wrote:
> On 30/08/2021 23:15, Scott Lurndal wrote:
>> gareth evans <headst...@yahoo.com> writes:
>>> Not sure in which group to pose this question ...
>>>
>>> After watching the first episode of Vigil last night, I
>>> wonder what are the multiple waterfall displays shown
>>> in the submarine's control room?
>>>
>>> Are they audio frequency spectra?
>>
>> SONAR.
>
> No, they will be passive listening devices. Frequency in the x
> direction, amplitude set by brightness, and over time as it falls down
> the screen.

Passive sonar is also sonar.

Niklas
--
When you need a helpline for breakfast cereals, it's time to start
thinking about tearing down civilisation and giving the ants a go.
-- Chris King in asr
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