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.

Vito wrote:
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.

Quite, but the sound waves generated by the target vessel do themselves
propagate in a uniform direction from the source, so they _will_ be picked
up.

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

"Armond Perretta" wrote in message ...
Vito wrote:
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.

Quite, but the sound waves generated by the target vessel do themselves
propagate in a uniform direction from the source, so they _will_ be picked
up.

The trouble is that the original poster was concerned about power consumption
on his radar. I can't imagine that a sonar solution could get away with anything
less than a fairly powerful PC running to do the signal processing, you need to
filter out all the false stuff including noises from your own vessel. Even so, for
boats with the power to keep it running, it would be very interesting technology.
The obvious use is for single-handers but, even for crews maintaining a 24
hour watch, humans can get tired and have lapses of concentration so an extra
"safety net" would be very useful.

- Julian.

Julian wrote:
"Armond Perretta" wrote ...

... the sound waves generated by the target vessel do
themselves propagate in a uniform direction from the source, so
they _will_ be picked up.

... for boats
with the power to keep it running, it would be very interesting
technology. The obvious use is for single-handers but, even for
crews maintaining a 24 hour watch, humans can get tired and have
lapses of concentration so an extra "safety net" would be very
useful.

I have many times, in clear conditions and with "unlimited" visibility, had
the radar pick up targets that I probably would have missed using only
binoculars and a steady hand (even assuming that I was at the time being
diligent). I am not suggesting that one should rely _only_ on electronic
aids, but if they can be supported financially, maintenance-wise, and
power-wise, I think the decision gets fairly obvious.

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