NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Iterative solution for calculating intersecting LOPs?
From: David C
Date: 2026 Nov 2, 14:30 -0800
From: David C
Date: 2026 Nov 2, 14:30 -0800
Joshua I wondered why your method uses simple arithmetic but Johnson's method uses the A B C tables. This is my explanation (which my be completely wrong).
In the LOP method it is assumed that distances are short and lines are straight. Hence your method of scaling on a plane chart makes sense.
The Johnson method uses factor "C". This is the change in longitude for a 1' error in latitude. Therefore maybe Johnson's method applies to a mercator chart? if so what is the difference in resulting position. I am sure someone could derive a function giving the mercator/plane chart corection factor as a function of latitude.
I have attached copies of two pages from Burton (1947). This goves a more upto date version of Johnson's method.
David C
File:
File:
