On Wed, 28 Jun 2017 17:04:54 -0500, Wayne.B
wrote:

On Wed, 28 Jun 2017 17:17:52 -0400, "Mr. Luddite"
wrote:

I am saying that according to the regs, it's up to the give way vessel
to do whatever is necessary to avoid a collision.

===

The wording of the COLREGS is interesting. Actually it is the
responsibility of both vessels to avoid a collision. That's why the
final report usually assigns some blame to each, with the burdened
vessel getting the lions share.

Other interesting factoids: The destroyer was almost certainly not
broadcasting an AIS position, at least not on civillian frequencies.
That's why we are seeing tracks of the freighter's course but not the
destroyer's. There is a world wide network of AIS receiving stations
that forward their position plots to central servers. One of the best
known is www.marinetraffic.com. Our own experience on the water with
military/USCG/Law Enforcement indicates that they rarely broadcast
their AIS position. That may have contributed to the confusion (if
any) of the freighter. It might have also have been a factor on the
destroyer if the navy doesn't train with AIS plotting and
interpretation. Relying on RADAR only does not tell the whole story.
We've found AIS to be invaluable when sorting out complex situations,
especially at night.

Another interesting bit with regard to observing constant bearings as
an indicator of a collision course: With large vessels it is
important to take bearings on both the bow and stern of the
approaching vessel. We have seen situations (with large ships), where
we have a changing bearing with the bow but a constant bearing
somewhere aft (or vice versa). That's just how the geometry works at
close quarters and larger scale.

These destroyers have fire control systems on board that will compute
all sorts of things about course and speed of the target but at 0130
they may not have been doing that up in CIC. Even in the puddle pirate
Navy we did plots on every target we saw but where we were most of the
time, they were few and far between. It was an event to track a
target.
I don't know what it is like in coastal Japan in 2017 but our rule of
thumb in 1965 with the electronics we had on board was anything at sea
within 10 miles was considered a collision risk until we were sure we
would miss it ... by 10 miles if possible.