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Re: Z vs Zn
From: Gary LaPook
Date: 2012 Dec 5, 09:40 -0800

Interesting, you're right, you don't actually need to make that last math error, er, conversion to Zn in order to plot the LOP. Well, you do, at least in your head, because the roses on charts and plotting sheets do not have the proper scales for Z. Now if somebody made an aircraft plotter with a second scale running counter clockwise (actually, clockwise because the scale on an aircraft plotter already runs counter clockwise because how it is used) then it would be simple to just use Z.

gl

--- On Wed, 12/5/12, Paul Hirose <cfuhb-acdgw@earthlink.net> wrote:

From: Paul Hirose <cfuhb-acdgw@earthlink.net>
Subject: [NavList] Re: Z vs Zn
To: NavList@fer3.com
Date: Wednesday, December 5, 2012, 9:26 AM

N624MA wrote:
> I understand that Zn is referenced to True North (000T) but what is "Z" referenced to, and why can't I just us it as azimuth increasing clockwise from 000T?

Z is referenced to the "elevated pole". That would be the north pole if your assumed position is in the northern hemisphere. Angles Z and Zn are identical if the north pole is the elevated pole, and the body is not west of the meridian.

Most traditional sight reduction methods yield Z, which the navigator must convert to Zn. Well, actually the conversion is not required. In fact, I have found it easier to plot the line of position directly from Z. A glance at the LHA tells you whether to measure east or west from the elevated pole.

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