NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Andrés Ruiz
Date: 2009 Dec 16, 09:06 +0100
In celestial navigation two motions are involved:
- The relative motion
of the observed celestial body
- The motion of the observer
At sea there are some uncertainties, in navigation –coastal
or celestial– in order to get a fix:
- Initial position of
the observer
- Course and speed
and are interrelated. In CelestialFix.exe the process
for obtaining a running fix is iterative and based in two rotations to move the
CoP. But when using Kaplan’s method the motion of the observer is part of
the calculation, like in a lot of engineering models.
The traditional Running Fix treatment is an approximation
of the whole problem, but enough for practical purposes. Is the one a navigator
always must know. “RFix animation.ppt” by Lu Abel is very
didactical. Thanks. Yes, I say: “Teach Running Fixes”
In an astronomy course, the speaker comparing the
stars with lighthouses in the sky and this gave me the idea to write the
article: “Fundamentos de la Navegacion Astronomica.pdf” to explain
what is a celestial fix.
A good review is available online http://aa.usno.navy.mil/publications/docs/reports: "The Motion of the Observer in Celestial
Navigation". Kaplan, G. H. (1996), Navigator's
Newsletter, Issue 51 (Spring 1996), pp. 10-14. PDF (113K) or PostScript
(100K).
Andrés Ruiz
Navigational Algorithms
http://www.geocities.com/andresruizgonzalez
-----Mensaje original-----
De: navlist@fer3.com [mailto:navlist@fer3.com] En nombre de John
Karl
Enviado el: domingo, 13 de diciembre de 2009 17:25
Para: NavList@fer3.com
Asunto: [NavList 11116] Why Not To Teach Running Fixes
Ah, the traditions of the sea.
For all the talk on how to teach running fixes, here's
my 2 cents
worth on why to not teach them at all -- they make no
sense whatsoever.
The figure below shows that they operate under
extremely ridiculous
assumptions: They assume that the estimated DR track
perpendicular to
LOP1 is completely accurate and that the DR component
parallel to LOP1
is completely without value. Can anyone on the List
justify these two
assumptions??
I recommend using the Estimated Position (EP) concept
shown in the
figure. It fully honors the new LOP2 while retaining
the information
in the DR that is not contradicted by LOP2.
JK
NavList message boards: www.fer3.com/arc
Or post by email to: NavList@fer3.com
To , email NavList+@fer3.com
NavList message boards: www.fer3.com/arc
Or post by email to: NavList@fer3.com
To , email NavList+@fer3.com