Re: Watching for surface traffic (was: Submarine Movie? or TV?)

[Michael B Holt <michaelbholt@juno.com>]

The device I had in mind was quite simple.   

The final version of it (rendered before I went to meet Lynn -- never
mind
those details -- one adolescent summer) had four microphones.   All were
mounted horizontally in the same plane, facing 90 degrees apart.   Each
one had a LED sound level meter.  

To use it, the operator just looked at the flashing bars of LEDs and
decided which two reported the nearest outboard. 

On Sun, 4 Jul 1999 15:28:09 -0700 (MST) John Brownlee writes:
>	With regard to automation, this sort of thing -IS- possible. A
lot
>of it comes down to how smart the frequency analysis has to be in order
to
>correlate the rate of change of the power spectrum with an incoming or
>outgoing boat. I would think the only cases you would care about would 
>be incoming and outgoing in close proximity, which means the Doppler 
>shift you are looking for should be noticeable to spectrum analysis.
Also (and 
>any of you subbers who are also IFR pilots will immediately recognize
this 
>fact) you need to consider depth as a constraint on the system, as
Doppler 
>gives you only slant-velocity information, so you are less likely to
detect 
>the presence of Joe Drunk Weekend Skipper at depth than near the
surface. 
>A lot of the basic physics is on your side, but the technology is 
>non-trivial.

All good, but a bit more complex than I had in mind then or now.   All I
was
looking for is the general direction of the boats above.

Think "late 60s Radio Shack technology" and you have the level of
complexity
I expected to face.

>	Probably cheaper to bribe a friend with gas/food/beer/greenbacks
to
>stand watch and shoo away the ooglers. 

Yeah, but then he'd want to submerge next.   Guess we gotta look for
bored
boat-owning buddies with claustrophobia.


Cheers,


Mike Holt
-- 

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