Derek Weston wrote:

... electronic means to
automatically detect vessels ... are of great value to us.

We have a radar with a watch facility which is great, except it
draws 30-odd watts, more that we can afford ...

In general your solutions appear to be a bit more complex than is absolutely
necessary. Just my point of view, of course.

For example, my small Furuno "watches" on a scheduled basis and draws very
little. You might want to consider a more energy-efficient radar.

... Our radar detector works well, but ships often
have their radars switched off.

Are you sure of this, and if so, how? You are suggesting that these
commercial vessels are operating illegally (which of course is possible,
but, en masse, unlikely).

1) Nav light detectors
... [details snipped] ...

I am not an electronics designer, but this setup seems beyond the financial
and maintenance abilities of a typical small boat sailor.

2) Hydrophone systems
Perhaps a ships prop or other ship noise can be detected
electronically.

This leaves out vessels not propelled by machinery. In any case a small
sonar seems like a good possibility compared to the optical device above.

--
Good luck and good sailing.
s/v Kerry Deare of Barnegat
http://kerrydeare.tripod.com

On 17 Aug 2003 00:41:30 -0700, (Derek Weston)
wrote:

We shorthand frequently on our sailboat, and electronic means to
automatically detect vessels in our area are of great value to us.

We have a radar with a watch facility which is great, except it draws
30-odd watts, more that we can afford as we're primarily solar panel
powered. Our radar detector works well, but ships often have their
radars switched off.

Two ideas I've been mulling over to which others may be able to
contribute useful ideas:

1) Nav light detectors
I think it may be possible to devise an electronic system which can
detect red and green coloured lights, and distinguish these from the
moon and the stars.
I'm imagining a rotating system with a cylindrical lens and both
red-filtered and green-filtered detectors, and triggering an alarm on
the basis of the magnitude of the difference between the two sensor
outputs. With appropriate relative gain settings, the moon and the
stars could give a near null result, while coloured nav lights may
give a greater output sufficient for the alarm trigger.
This may be close to the limits of present technology. I can imagine
the sensors may need to be cooled (with consequent condensation
problems).

How are you going to filter out white light from the stars? It
contains red and green, too. What about power boats only displaying
white and red or white and green unless they are headed straight for
you? What about coming up on the stern of that 950' containership at
anchor? Better stick with the radar and get a shaft alternator or
wind bugger, instead.....please?

2) Hydrophone systems
Perhaps a ships prop or other ship noise can be detected
electronically.

US Navy has gotten so good they can tell you WHO the ship is from the
sonar signature. Not sure they can tell what underwear the captain
and first mate are wearing, yet, but they're working on it at MIT.

You'll have to listen, as I have, to the passive sonar in a Trident
nuclear sub and see how much equipment is necessary to do what you're
thinking. It sure won't run on 30 watts off a solar panel, though.
Oh, did I mention the shaft alternator and windbugger work at
NIGHT?...(c;

Any thoughts, previous work, intelligent comments....

Derek Weston
Talking Marine Instruments
http://www.alphalink.com.au/~derekw/mit/apps.htm

I don't know what Oz's admiralty thinks about it but here in the
States the rules say you must "maintain a lookout", whatever that
means. Yeah, there are idiots sailing Around The World Alone sleeping
in their bunks. Amazing how they survive as long as they do. Lucky
for them it's a big ocean.


Larry

Extremely intelligent life must exist in the universe.
You can tell because they never tried to contact us.

For one thing when you sail alone you have alarms set on the radar, wind,
depth, and gps. You're only cat napping for a few minutes at a time unlike
sleeping for 8 hours. The only idiots I know that do this are the Volvo
Ocean Racers, which is a sanctioned race.

Sea or admiralty law states if your boat is equipped with radar and your not
using it when you have an accident your at 50%fault. This includes being
struck by other vessels.

Jack's two cents


"Larry" wrote in message
...
On 17 Aug 2003 00:41:30 -0700, (Derek Weston)
wrote:

We shorthand frequently on our sailboat, and electronic means to
automatically detect vessels in our area are of great value to us.

We have a radar with a watch facility which is great, except it draws
30-odd watts, more that we can afford as we're primarily solar panel
powered. Our radar detector works well, but ships often have their
radars switched off.

Two ideas I've been mulling over to which others may be able to
contribute useful ideas:

1) Nav light detectors
I think it may be possible to devise an electronic system which can
detect red and green coloured lights, and distinguish these from the
moon and the stars.
I'm imagining a rotating system with a cylindrical lens and both
red-filtered and green-filtered detectors, and triggering an alarm on
the basis of the magnitude of the difference between the two sensor
outputs. With appropriate relative gain settings, the moon and the
stars could give a near null result, while coloured nav lights may
give a greater output sufficient for the alarm trigger.
This may be close to the limits of present technology. I can imagine
the sensors may need to be cooled (with consequent condensation
problems).

How are you going to filter out white light from the stars? It
contains red and green, too. What about power boats only displaying
white and red or white and green unless they are headed straight for
you? What about coming up on the stern of that 950' containership at
anchor? Better stick with the radar and get a shaft alternator or
wind bugger, instead.....please?

2) Hydrophone systems
Perhaps a ships prop or other ship noise can be detected
electronically.

US Navy has gotten so good they can tell you WHO the ship is from the
sonar signature. Not sure they can tell what underwear the captain
and first mate are wearing, yet, but they're working on it at MIT.

You'll have to listen, as I have, to the passive sonar in a Trident
nuclear sub and see how much equipment is necessary to do what you're
thinking. It sure won't run on 30 watts off a solar panel, though.
Oh, did I mention the shaft alternator and windbugger work at
NIGHT?...(c;

Any thoughts, previous work, intelligent comments....

Derek Weston
Talking Marine Instruments
http://www.alphalink.com.au/~derekw/mit/apps.htm

I don't know what Oz's admiralty thinks about it but here in the
States the rules say you must "maintain a lookout", whatever that
means. Yeah, there are idiots sailing Around The World Alone sleeping
in their bunks. Amazing how they survive as long as they do. Lucky
for them it's a big ocean.


Larry

Extremely intelligent life must exist in the universe.
You can tell because they never tried to contact us.

Derek Weston wrote:

We shorthand frequently on our sailboat, and electronic means to
automatically detect vessels in our area are of great value to us.

We have a radar with a watch facility which is great, except it draws
30-odd watts, more that we can afford as we're primarily solar panel
powered. Our radar detector works well, but ships often have their
radars switched off.

Two ideas I've been mulling over to which others may be able to
contribute useful ideas:

1) Nav light detectors
I think it may be possible to devise an electronic system which can
detect red and green coloured lights, and distinguish these from the
moon and the stars.
I'm imagining a rotating system with a cylindrical lens and both
red-filtered and green-filtered detectors, and triggering an alarm on
the basis of the magnitude of the difference between the two sensor
outputs. With appropriate relative gain settings, the moon and the
stars could give a near null result, while coloured nav lights may
give a greater output sufficient for the alarm trigger.
This may be close to the limits of present technology. I can imagine
the sensors may need to be cooled (with consequent condensation
problems).

2) Hydrophone systems
Perhaps a ships prop or other ship noise can be detected
electronically.

Any thoughts, previous work, intelligent comments....

Derek Weston
Talking Marine Instruments
http://www.alphalink.com.au/~derekw/mit/apps.htm

Years ago a marine publication recommended buying a standard traffic radar
detector. Seems that they are so broadband that they will pick up nearly
everything in the radar band. Owing to philosophical objections to the
practice, I've never owned one, but it might be worth testing.

I should think that anything of 'size' at night would be equipped with, and
using, radar.

Subject: Vessel detectors
From: Chuck Bollinger

Years ago a marine publication recommended buying a standard traffic radar
detector. Seems that they are so broadband that they will pick up nearly
everything in the radar band. Owing to philosophical objections to the
practice, I've never owned one, but it might be worth testing.

"Philosophical objections" to owning a radar detector to pick up ships radar!?

OK Chuck, I got to hear this one.

Capt. Bill

(Larry) wrote in message ...
How are you going to filter out white light from the stars? It
contains red and green, too.

I was imagining determining the difference in magnitude between the
red and green signals, 'though there are other possibilities for
differentiating between starlight spectra and nav light spectra.

What about coming up on the stern of that 950' containership at
anchor?

Unlikely mid ocean :-)

Better stick with the radar and get a shaft alternator or
wind bugger, instead.....please?

Well maybe, but what I've learned from this thread, my own
observations and others remarks is that nothing (including radar and
an alert watchkeeper) will detect everything which may cause a
problem.

.... Lucky for them it's a big ocean.

Indeed. But it really is a big ocean - I can recall three two week
stretches at sea when we saw absolutely no other vessels.

In article ,
says...
(Larry) wrote in message ...
How are you going to filter out white light from the stars? It
contains red and green, too.

I was imagining determining the difference in magnitude between the
red and green signals, 'though there are other possibilities for
differentiating between starlight spectra and nav light spectra.


If your boat is moving, you could well be on a collision course that
would allow you to see only the red or only the green light. That
makes the problem more difficult.

Furthermore, on a moonlight night, you will have to contend with
reflections off the wave tops. Those will have transient levels
of red and green that will complicate the detection problem.

Overall, it looks like this type of sensor would require quite a bit of
spectral discrimination and tracking intelligence.
What about coming up on the stern of that 950' containership at
anchor?

Unlikely mid ocean :-)

Better stick with the radar and get a shaft alternator or
wind bugger, instead.....please?

Well maybe, but what I've learned from this thread, my own
observations and others remarks is that nothing (including radar and
an alert watchkeeper) will detect everything which may cause a
problem.

.... Lucky for them it's a big ocean.

Indeed. But it really is a big ocean - I can recall three two week
stretches at sea when we saw absolutely no other vessels.


IIRC, on one crossing from Tahiti to LA, we saw no other vessels
at all. I suppose some may have popped up on radar, though, that
I didn't know about. Our radar had quite good range, too. But then
I was aboard a 400' missile range tracking ship at the time!

Mark Borgerson

"Armond Perretta" wrote in message ...
Derek Weston wrote:

... electronic means to
automatically detect vessels ... are of great value to us.

We have a radar with a watch facility which is great, except it
draws 30-odd watts, more that we can afford ...

In general your solutions appear to be a bit more complex than is absolutely
necessary. Just my point of view, of course.

For example, my small Furuno "watches" on a scheduled basis and draws very
little. You might want to consider a more energy-efficient radar.

I don't think there is one, but would certainly be happy to be
corrected. From what I have determined, 30W is typical for keeping the
magnetron "alight" between periodic scans.


... Our radar detector works well, but ships often
have their radars switched off.

Are you sure of this, and if so, how? You are suggesting that these
commercial vessels are operating illegally (which of course is possible,
but, en masse, unlikely).

Yup, quite sure of it. We have a radar detector on board.
Others have found the same:
"It's also interesting to note that during the transatlantic, an
alarming number of vessel's contacted to evaluate our radar return,
responded willingly but said, "please wait while I turn on the radar!"
from http://www.ussailing.org/safety/Stud...arenhancer.htm

2) Hydrophone systems
Perhaps a ships prop or other ship noise can be detected
electronically.

This leaves out vessels not propelled by machinery.

True.

Terry Spragg wrote in message
I seem to recall some one devising an 'all around' lens that
focuses on a colour ccd camera. Any red or green light and it's
bearing would be detected in logic, and no scanning mirrors would
be required.

Right. Thanks for the info and comments.
I'm discouraged by my observation that night capable CCDs all seem to
have peltier cooled sensors.

If you have ever heard powerboat engine and prop noise
transmitted through the water and hull while enjoying a quiet
sail, you would think it possible to detect approaching ships
like submariners and antisubmariners do. Speech recognition logic
can recognise any sound it is trained to. As it can be sensitive
to specific voices, it could be attuned to high speed or heavy
props, or both, along with whales, which talk and blow a lot,
seemingly, and slop sounds from semi submerged containers of
certain volume and exhibiting audible resonances, etc. Three
hydrophones should be able to determine bearings of noise
sources, if not their source noise echos near shore. A high rate
repetiton sonar pinger and interleaved range gating logic may be
able to catch repeated MTI type returns, as opposed to wave face
clutter in deep waters. There is no reason why sophisticated
analysis engines could not be mass produced on microchips except
cost, which depends on scale of production. In the meantime,
logic development might have to do. What more engrossing passtime
could a long distance sailor wish for?

Indeed. I think I may do some experiments along this line.
Wouldn't help detecting other yachts, but none of the options
(including a good human lookout) is perfect.

Armond Perretta wrote:

In any case a small sonar seems like a good possibility ...

Sound waves bend downward creating a blind zone near the surface.