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.