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    Re: Puzzled by Kaplan's 'Motion of the Observer in Celestial Navigation'
    From: Peter Hakel
    Date: 2011 Jun 20, 21:47 -0700
    Richard,

    This trick does not employ the intercept method of St. Hilaire, so the Hc and Zn don't get to be used.  Instead, the author defers to Reference [5] for the direct calculation of the "two-body fix" by two intersecting circular LOPs.  The "running fix" is achieved here by shifting the center of one of these LOPs (Eq. 3), which effectively accounts for the motion of the vessel.  The solution is then found according to Reference [5]; or, e.g. see Section 1 in:

    http://www.navigation-spreadsheets.com/lops.html

    and references therein (James A. Van Allen, John Karl).


    Peter Hakel


    From: Richard <cnav{at}barsoom.plus.com>
    To: NavList@fer3.com
    Sent: Sunday, June 19, 2011 7:36 PM
    Subject: [NavList] Puzzled by Kaplan's 'Motion of the Observer in Celestial Navigation'

    Hi,
    I wonder if anyone here could help me. I have just read George Kaplan's paper 'The Motion of the Observer in Celestial Navigation', and have found something that puzzles me.
    In the section 'Adjustment of Celestial Coordinates', he presents an equation to obtain a new GP that, when fed into a sight reduction process for the new AP, will produce the original altitude and azimuth.
    I don't understand the purpose of this - why run a new sight reduction that is (by design) just going to produce the same Hc and Zn ?
    Thanks,
    Richard
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