Welcome to the NavList Message Boards.


A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Add Images & Files
    Re: Eprf Vs, Trf
    From: Rob M
    Date: 2009 Dec 18, 08:41 -0800

    I think that a navigator may indeed choose to use your method as
    That does not mean that the RFIX is dead or should in all cases be
    It seems to me that the quality of, and the navigators' confidence in
    the orginal EP is the question.
    EPs have explicit assumptions built into them. The value in the RFIX
    (in my opinion) lies in its utility in questioning the assumptions,
    and giving the navigator a means and technique to revisit them. This
    technique has enhanced practical utility in being widely used and
    understood, so it is easy to have others review the work and assist in
    the exercise.
    In the example you give here a navigator may choose the EP2, the RFIX,
    or some other point as the actual best estimate of position when
    exercising judgment on the preceding navigation and LOPs. If there is
    a reasonable level of confidence in the LOP2, that point would be
    somewhere on LOP2. If there is a high level of confidence in the
    estimate of Track Made Good, your outcome EP2 may indeed be the
    selected 'position'.
    When navigating solely by means of RFIXes over an extended period,
    most navigators would question the outcome should their RFIXes and EPs
    continue to diverge at an increasing rate over an extending period of
    time. Imagine your drawn example repeating over a series of LOPs with
    increasing divergence in each successive EP3, EP4, EP5, EPn . . . --
    What would you suggested course of action be then?
    Should my navigation reveal a plot such as you have drawn, I would be
    very very very interested in a re-examination of the vector components
    of the original EP and the track made good estimate, seeking a very
    good explanation (or at the least rationalization) of the widely
    divergent RFIX and EP2 positions. The RFIX would be one set of data
    used in such an examination. It may assist in revealing a systemic
    error in one of the inputs of the Track Made Good (compass error, mis-
    estimation of set and drift, mis-estimation of vessel speed, etc.). I
    would not blindly follow the RFIX or EP, but rather seek to reconcile
    and explain their divergence before selecting any position as my EP.
    The FIX, EP, DR, and RFIX all have a place in the navigators'
    conceptual toolbox, and can all serve to assist in determining the
    safe passage of your vessel. A navigator should not be a slave to any
    one of them as all are fraught with peril should they be used in
    isolation from the others.
    The RFIX, a hybrid of a FIX and a DR, is useful, but one should not be
    a slave to it. Your EPRF, a hybrid of a FIX and an EP is indeed useful
    as well but would serve a navigator poorly if relied on without access
    to other traditional methods.
    NavList message boards: www.fer3.com/arc
    Or post by email to: NavList@fer3.com
    To unsubscribe, email NavList+unsubscribe@fer3.com

    Browse Files

    Drop Files


    What is NavList?

    Join NavList

    (please, no nicknames or handles)
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.

    Email Settings

    Posting Code:

    Custom Index

    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site