NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: No Two-Body Fix Problems
From: Peter Hakel
Date: 2009 Nov 5, 17:50 -0800
From: John Karl <jhkarl@att.net>
To: NavList <navlist@fer3.com>
Sent: Thu, November 5, 2009 9:35:51 AM
Subject: [NavList 10464] No Two-Body Fix Problems
I'm starting a new thread (I think it's called) because the "Two Body
Fix Caveat" seems to have gotten off topic.
As I posted on the other thread, It seems to me that if the computer
code simply calculates the answers for the two possibles fixes, using A
+B and A-B in Eq. 7.5d, and then lets the navigator pick the closest
fix, all possible combinations of the locations of the GPs and ship
are covered.
And I don't see any problem with the ship being on, or near, GP1's
meridian. This is a well defined problem with no ambiguity in the
equations, and the navigator doesn't need to know his position
relative to the meridian.
Computing both fixes makes the program's inputs and outputs very
logical and straightforward. After all, there are two fixes in the
solution and the navigator must, indeed, select the proper one.
Those interested might want to check this out to see if I'm right,
John
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From: Peter Hakel
Date: 2009 Nov 5, 17:50 -0800
This is my thinking exactly, please see the attached spreadsheet.
There are some highly specialized arrangements with which it can have problems,
but it should work fine for any "normal" case.
The preloaded case is rotated 90 degrees from W to S with respect to my original illustration example.
Thus it has the GP1, GP2, and the ship on the same meridian, with osculating LOPs.
Peter Hakel
There are some highly specialized arrangements with which it can have problems,
but it should work fine for any "normal" case.
The preloaded case is rotated 90 degrees from W to S with respect to my original illustration example.
Thus it has the GP1, GP2, and the ship on the same meridian, with osculating LOPs.
Peter Hakel
From: John Karl <jhkarl@att.net>
To: NavList <navlist@fer3.com>
Sent: Thu, November 5, 2009 9:35:51 AM
Subject: [NavList 10464] No Two-Body Fix Problems
I'm starting a new thread (I think it's called) because the "Two Body
Fix Caveat" seems to have gotten off topic.
As I posted on the other thread, It seems to me that if the computer
code simply calculates the answers for the two possibles fixes, using A
+B and A-B in Eq. 7.5d, and then lets the navigator pick the closest
fix, all possible combinations of the locations of the GPs and ship
are covered.
And I don't see any problem with the ship being on, or near, GP1's
meridian. This is a well defined problem with no ambiguity in the
equations, and the navigator doesn't need to know his position
relative to the meridian.
Computing both fixes makes the program's inputs and outputs very
logical and straightforward. After all, there are two fixes in the
solution and the navigator must, indeed, select the proper one.
Those interested might want to check this out to see if I'm right,
John
--~--~---------~--~----~------------~-------~--~----~
NavList message boards: www.fer3.com/arc
Or post by email to: NavList@fer3.com
To , email NavList+@fer3.com
-~----------~----~----~----~------~----~------~--~---
File: 110467.two_body_fix.xls
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