NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Formulas to Compute LHA
From: Lu Abel
Date: 2009 Jun 28, 09:04 -0700
From: Lu Abel
Date: 2009 Jun 28, 09:04 -0700
Hmm, never thought of NP vs SP "up" in a time diagram, but I realize the time diagrams I am used to using are NP up. Problem with NP up is that angles go in the "wrong" direction. From everything from high school math to compass roses, we are used to angles increasing clockwise. But in a NP up time diagram angles increase CCW. Looks like SP up is/was an attempt to "correct" that. Sort of like the US Navy correcting Benjamin Franklin's error in saying that electrical current flows from positive to negative; my dad served time in the US Navy as an electrician and all his textbooks had current flowing from negative to positive (and right-hand rules being replaced with left-hand rules). Fun reading years ago for a nascent electrical engineer (yours truly). For what it's worth, Bowditch uses a NP up time diagram (see Fig 1525b in Chapt 15) Lu Abel waldendand@YAHOO.COM wrote: > I find it necessary to be very cautious reading "time diagrams". Very reputable sources find themselves "poles apart" on the NP up vs SP up issue. (Why is this?) > > > > > --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---