NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: The term AP
From: Stan K
Date: 2015 Jan 20, 19:07 -0500
From: Stan K
Date: 2015 Jan 20, 19:07 -0500
Perhaps the difficulty comes from the difference between an assumed position like the DR position and the assumed position determined by the rules of methods like Pub. 229, which force values appropriate to the method (whole degrees of latitude closest to the DR latitude, longitude to get whole degrees of LHA, etc.). I like John's term "assigned point" for the latter.
Stan
-----Original Message-----
From: Gary LaPook <NoReply_LaPook@fer3.com>
To: slk1000 <slk1000@aol.com>
Sent: Tue, Jan 20, 2015 6:37 pm
Subject: [NavList] Re: The term AP
From: John Karl <NoReply_JohnKarl@fer3.com>
To: garylapook---.net
Sent: Tuesday, January 20, 2015 9:36 AM
Subject: [NavList] Re: The term AP
From: Gary LaPook <NoReply_LaPook@fer3.com>
To: slk1000 <slk1000@aol.com>
Sent: Tue, Jan 20, 2015 6:37 pm
Subject: [NavList] Re: The term AP
"Assuming, just for ease of computation, I were here.." You are assuming that position just for that purpose, obviously nobody believes he is actually there. Why get so upset about the "AP" terminology? Have you ever met anyone who was confused by that concept and label?
gl
From: John Karl <NoReply_JohnKarl@fer3.com>
To: garylapook---.net
Sent: Tuesday, January 20, 2015 9:36 AM
Subject: [NavList] Re: The term AP
Doug &
all,
I don't like the term "trial position" for the same reason I don't like "assumed position." In the St. Hilaire sight reduction we are not trying, experimenting, or assuming anything. Knowing the body's GP and Ho we can compute the entire exact circular LOP. St. Hilaire gives us the azumuth, and great circle distance, to the nearest point (a PLOP) from the AP to the LOP. Knowing this azimuth, we can appoximate the LOP (at the PLOP) with a straight line perpendicular to the intercept. It's the most efficient method of extracting, from only two equations, a very useful approximation to the LOP.
J. Karl
