NavList:

[NavList 1437] Re: Navigator's Newsletter, and other forums.
James R. Van Zandt wrote:

The sight reduction methods I have seen require an estimated position

[1], or give no error estimate [2], or both [3].

-----Mensaje original-----
De: NavList@fer3.com [mailto:NavList@fer3.com] En nombre de Paul Hirose
Enviado el: miércoles, 18 de octubre de 2006 21:19
Para: NavList@fer3.com
Asunto: [NavList 1442] Re: Navigator's Newsletter, and other forums.

I don't believe that requiring an assumed position for a sight reduction

is a significant problem in practice. And I suspect proficient

navigators will pay little attention to a computer's error estimate.

They will rely on their experience and intuition, based on the observing

conditions and the way the LOPs look on the chart.

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Indeed using the “DeWit/USNO/Compac Data”, least squares algorithm for reduction of n sights, you can suppose any assumed position far away from the real position. Because it do an iterative find of the fix, if a solution exist, after few iterations it is found.

If the assumed position is near the estimated one, DR, or the celestial position, only one or two iterations are required.

Try it with the software available at my web page: n LOPs Fix (SR_LS.zip)

The algorithm is described in the Nautical Almanac and at [n LOPs Fix] :

Andrés

http://www.geocities.com/andresruizgonzalez