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    Re: Why Not To Teach Running Fixes yes
    From: Rob M
    Date: 2009 Dec 14, 09:13 -0800

    there is always disparity between the classroom (where this discussion
    started) and practical application of concepts.
    
    the RFIX is taught to get a set of concepts established in a students'
    head in isolation so they may then be used in situ with other concepts
    to accurately establish a position (as accurately as possible under
    the circumstances, which may preclude a real FIX established by
    simultaneous LOPs).
    
    for a time-separated set of navigation LOPs one can establish an RFIX
    and an EP. Neither are FIXes. seeing the two one can understand the
    injected estimate of set and drift which may be of interest to the
    navigator.
    
    the plotting of RFIXes also allows a navigator to look back and
    understand possible errors in previous plotting or challenge
    assumptions in the estimate of set and drift, etc which are of value.
    
    the navigator must remember that the RFIX is not a FIX, nor an EP
    (even when plotted to equal the position of an EP). the two are
    different and must be evaluated differently.
    
    a FIX is clearly superior to an EP, DR or RFIX, however in the absence
    of a FIX the RFIX, DR and EP have different values to the navigator.
    The RFIX and associated concepts, which allow some off the vessel
    observations to be incorporated into the calculation of position are
    of greater value to the navigator than just a DR or EP, which are
    entirely based on assumptions.
    
    In complete classroom plotting exercises I regularly teach the
    plotting of a set of a FIX, then a DR, EP and RFIX an hour later, and
    then a new FIX an hour further on, and the review the lot forward and
    back to enable students to see the value in the review and evaluation
    of the 4 different concepts and how they can each independently inform
    the navigator. most find this a worthwhile exercise.
    
    Rob
    
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