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    Re: Advancing LOPs for precision fixes
    From: Andrés Ruiz
    Date: 2010 Feb 18, 12:01 +0100

    At my web page my article:
    "Celestial Fix Nautical Almanac Sight Reduction algorithm for n LoPs", gives a 
    detailed information of the algorithm.
    Originally the references are:
    * Optimal Estimation of a Multi-Star Fix, C. De Wit. NAVIGATION, Vol.21 , No. 4, Winter 1974-
    75, pp 320-325
    * Compact Data for Navigation and Astronomy for the Years 1991-1995, Cambridge University
    Press ISBN 0-521-38731-0. Yallop B. D. and Hohenkerk C. Y. (1991).
    * The Nautical Almanac. USNO
    Also the free program "CelestialFix.exe" implements the method, see pic.
    Andrés Ruiz
    Navigational Algorithms
    -----Mensaje original-----
    De: navlist-bounce@fer3.com [mailto:navlist-bounce@fer3.com] En nombre de Gary LaPook
    Enviado el: jueves, 18 de febrero de 2010 11:41
    Para: NavList@fer3.com
    Asunto: [NavList] Re: Advancing LOPs for precision fixes
    Have you tried using the method in the N.A. to which you refer? I may be 
    missing something but I don't see anywhere in the given formulas where 
    you input course and speed which would be necessary if the method was 
    allowing for advancing the LOPs to a common time.
    P H wrote:
    > As John Karl writes in his book:
    > "The Nautical Almanac gives an iterative procedure for calculating a 
    > fix from several intercepts and azimuths determined from their St. 
    > Hilaire sight reductions."
    > I would add that this procedure does take the vessel motion (assumed 
    > to be constant during the round of observations) into account.  I am 
    > confident that I am simply restating a fact that is well-known among 
    > NavList members.  Also, I think it is not unreasonable to assume that 
    > the content of the Nautical Almanac reflects common (standard, 
    > recommended, accepted, etc.) practice.
    > Peter Hakel
    > ------------------------------------------------------------------------
    > *From:* hch 
    > *To:* NavList@fer3.com
    > *Sent:* Tue, February 16, 2010 8:20:41 AM
    > *Subject:* [NavList] Re: Advancing LOPs for precision fixes
    > Gary,
    > You said ... "It is common practice to ignore the movement of the ship 
    > during the time period needed to take a round of sights ...", and I 
    > am unable to dispute this assertion in the light of today's "it's good 
    > enough" approach to Celestial Navigation. I can, however, state in no 
    > uncertain terms that this was not the traditional approach - LOPs 
    > generated in a round of sights were always advanced or retarted to a 
    > common time, so long as the distance run between individual sights was 
    > measurable, if for no other reason than professional pride.
    > Regards,
    > Henry


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