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(no email)
Date: Fri Jun 02 2006 - 13:51:57 EDT
I would like to add another comment on containers floating. If there were truly a lot of them floating out there a lot of them would be coming ashore. I fly the beaches of Alaska from Ketchikan to Nome on the down wind side of one the most heavily traveled routes in the world. I have never seen a container on the beach. Granted I havn't seen the coast of the Y K delta for a while which is a really likely area.
A %10 loss in buisness is unsupportable, I would bet that the true figure is a fraction of %1.
HJ
----- Original Message -----
From: Ken James <>
Date: Thursday, June 1, 2006 10:57 pm
Subject: [world-cruising] seeing containers with fwd scan sonar
> The issue of semi-submerged containers does not seem to me to
> really be an
> issue - lets see - containers are 12 feet or so minimum in an
> dimension -
> when containers are really going to be an issue, I would be most
> probably in
> deeper water, thus getting pretty goog forward range - specified
> as AT THE
> SURFACE - but the container is 12 feet down - seems to me I would
> see it
> pretty good!
>
> Reply;
> This is not a correct conclusion. The fact is all the fwd scan
> units depend
> on a depth of water to see fwd, in other words they cannot see the
> surface
> (unless maybe they bounce a beam off the bottom and the reflection
> bounces
> back...). The deep water is needed to see fwd as the beam angles
> out as a
> conical or elliptical beam and the angle makes it spread down as
> it goes
> fwd.
> As far as I know, it is not technicaly possible with sonar to spot
> an object
> right on the surface because as the beam travels to the air water
> interface
> it gets refracted and reflected and so becomes useless.
> I think the container depth of 12 ft would only be see-able if
> the boat was
> very close. By that time it is too late.
>
> Of course if you are a sub looking up it would be different.-Ken
>
>
>
>
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