NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: The term AP
From: Tom Sult
Date: 2015 Jan 21, 19:01 -0600
From: Tom Sult
Date: 2015 Jan 21, 19:01 -0600
I have not been following this closely, so sorry for a redundant comment. The AP is necessary to solve for the CN triangle. Once solved you compare the result to the observed and get your correction… This is St Hilaire Without some sort of an AP, DR or other you cant solve the triangle. I must have missed something because all of you know this better than me. Perhaps the discussion is about the reason for the name AP… it is an unfortunate choice but I have interpreted the Assumed, not as I assume I am hear but as in… lets just assume we are here for the purpose of this calculation.
On Jan 21, 2015, at 6:11 PM, John Karl <NoReply_JohnKarl@fer3.com> wrote:Gary L & All,
Yes, most (perhaps every) CN book that I've seen either does not clearly, or accurately, describe the role of the AP in the intercept method. Many alude to it being an approximation of some type, or even saying that "it's an approximation we wish to correct, or adjust in accuracy." Some say the AP is an approximation surrounded by uncertainty. Of course, that's true for the DR, but not for the AP. Also, some time ago when St. Hilaire was discussed at length on the NavList, a well-know member discribed it an an iterative calculation. Even my two editions of Bowditch only precriptively instruct performing the St. Hilare sight deduction with no discussion of why the AP is used.
J Karl
