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post #37 of Old 12-04-2012
PCP
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Re: Follow the ARC

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Originally Posted by JonEisberg View Post
You've certainly got that right... Mark has asserted that this close encounter "clearly" would have been averted had only both boats been equipped AIS and transponders, and mocks us wankers who might still rely on such a hopelessly outdated tool as a hand-bearing compass in such a situation...

However, with the sea state and conditions as described, and the courses being steered by both at the time fluctuating constantly and markedly, the utility of a technology as accurate and precise as AIS will be greatly diminished... The information displayed will be fluctuating wildly, between showing a collision course, and a safe crossing, or no crossing at all... And, of course, the effort to interpret the information displayed, and "average it out" in order to determine the proper course of action, will necessarily involve an inordinate amount of time staring at an AIS display screen, rather than across the water, as the situation is developing...

In this particular situation, I think a well-dampened hand bearing compass - used in conjunction with a pair of trusty old Mark I eyeballs, by a wanker who fully appreciates the danger of a "Constant Bearing, Decreasing Range" target at sea, at night - might have still have been the most useful tool for either crew to have had at their disposal...
A radar with MARPA would have been the best tool in my opinion, in conjunction with the eyes and the constant bearing. It would not only have showed you if it was a collision course but also the other boat speed and eventually the time for the collision. At night it is difficult to calculate distances but not with a radar. I had MARPA on the radar on my previous boat and not on this one. That reduces greatly the radar's efficiency as a navigation tool.

Regards

Paulo
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