NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Advancing LOPs for precision fixes
From: Andrés Ruiz
Date: 2010 Feb 18, 12:01 +0100
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. Regards, Andrés Ruiz Navigational Algorithms https://sites.google.com/site/navigationalalgorithms/ -----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. gl 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 > >