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Subject: LOPs
From: Rick Emerson (rick@XXX.XXX)
Date: Wed Jun 23 1999 - 11:24:50 EDT
kliment@XXX.XXX writes:
> There should be no confusion with the running fix since both original and
> final LOPs are labeled with time on top and bearing angle on the bottom. A
> dashed line showing distance run (D=ST) is constructed parallel to the DR
> course defining how far the original LOP must be advanced. The final LOP is
> labelled with both original and final LOP time. An R FIX is constructed when
> the time difference between original and final LOPs is greated than 20
> minutes otherwise it is treated as a normal FIX.
Adding more lines (i.e., dashed D=ST lines) strikes me as potential
chart clutter. The line's information can always be recovered by
simply measuring the distance between an LOP and its advanced
position. Speed and course should be on the track and similarly the
LOP's should have the times at the start and end of the run. In cases
where this line is needed, at some later time, to substantiate this
information, I suppose it makes sense but I'm hard pressed to think of
such a circumstance.
I also disagree with the 20 minute cutoff on fixes versus running
fixes. At six knots, that's a two mile run. In close-in piloting
(e.g., a radar harbor approach or running a shipping channel) that's a
significant distance, where current and leeway have time to assert
themselves. Conversely, while still several miles off or while
offshore, that's within "noise" limits. I'd leave setting a time
limit as a judgement call based on circumstances.
Rick
S/V One With The Wind, Baba 35
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