NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Wolfgang Köberer
Date: 2010 Oct 24, 20:32 +0200
I’ve read John Karl’s
article with interest, but I have to admit that I do not completely follow his
reasoning:
As I understand he thinks
that dropping a perpendicular from the position DR2 to the LOP2 gives an EP2
which should be preferable to a running fix from advancing LOP1 along the DR
track. What I don’t understand is why the best estimate should be where a
perpendicular from DR2 meets LOP2. Of course an error in measuring the height of
the heavenly object moves LOP2 only along the perpendicular, but that is no sufficient
reason to assume that the best estimate of the position is on the perpendicular
passing through DR2.
Or should we prefer that EP
because it is the closest point on LOP2 – being located on a
perpendicular to it. Why that?
His Figure 3 is rather
suggestive, but it only shows that the running fix may be way off from the EP2;
it does not show, though, where the error lies: is LOP1 wrong, or LOP2 , or is
there a strong current/faulty compass etc.? Or should we just trust DR more
than LOPs?
Have I got something
wrong there? I have to admit that my practical experience as a navigator stems
from rather restricted waters (Baltic, Zuiderzee, Greek archipelago, Turkey,
Western Mediterranean) with little current and no need for astro LOPs. And
crossing the
Wolfgang
Von: navlist-bounce@fer3.com
[mailto:navlist-bounce@fer3.com] Im
Auftrag von Gary LaPook
Gesendet: Samstag, 16. Oktober
2010 02:29
An: NavList@fer3.com
Betreff: [NavList] The Nonsensical
Running Fix
John Karl's article has been published in this month's
Ocean Navigator, attached.
gl