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: Peter Hakel
Date: 2010 Feb 18, 11:04 -0800
From: Peter Hakel
Date: 2010 Feb 18, 11:04 -0800
Yes, I implemented the method in this spreadsheet:
http://www.navigation-spreadsheets.com/lops.html#many_body_fix
I am now glad ;-) that I am not the only one who found this section of the N.A. not so clearly written. It indeed requires a little bit of detective work from the reader. It does not explicitly state that this method employs the dead-reckoning formulae from the preceding subsection. Fortunately the associated example is worked out in detail and its description refers to a common time for the fix and the individual times for the sights.
Peter Hakel
From: Gary LaPook <glapook@pacbell.net>
To: NavList@fer3.com
Sent: Thu, February 18, 2010 2:41:00 AM
Subject: [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
I am now glad ;-) that I am not the only one who found this section of the N.A. not so clearly written. It indeed requires a little bit of detective work from the reader. It does not explicitly state that this method employs the dead-reckoning formulae from the preceding subsection. Fortunately the associated example is worked out in detail and its description refers to a common time for the fix and the individual times for the sights.
Peter Hakel
From: Gary LaPook <glapook@pacbell.net>
To: NavList@fer3.com
Sent: Thu, February 18, 2010 2:41:00 AM
Subject: [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