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    LOPs
    From: Rick Emerson
    Date: 1999 Jun 23, 11:24 EDT

    kliment{at}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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