NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Andrés Ruiz
Date: 2008 Jun 12, 15:03 +0200
(in another format for
the pic)
In fact I have used
tree different criterions
over time:
·
0 <= L <= 360º (W to E)
·
-180º(W) <= L <= +180º(E)
·
-180º(E) <= L <= +180º(W)
and I prefer the –W/+E convention.
The equation for LHA becomes: LHA = GHA+L or LHA = GHA-L
Why I prefer the –W/+E convention, because I use a Cartesian and
spherical coordinate
System:
|
|
One can uses a time based convention or takes a Right-handed
reference frame or another…
I have books from
Also the IAU has changed its criterion recently.
Obviously, the convention of signs must be in accordance
with the equations.
The world of conventions. Why in some countries people
drive in left lane?
I don’t know what a ºF, a yard, a pound is? I know
what a pint is because I like beer :-), I have in my mind the international
system of units, … conventions, more or less successful, but conventions.
Andrés
-----Mensaje original-----
De: NavList@fer3.com [mailto:NavList@fer3.com]
En nombre de George Huxtable
Enviado el: miércoles, 11 de junio de 2008 15:30
Para: NavList@fer3.com
Asunto: [NavList 5399] Re: 3-Star Fix - "Canned Survival Problem"
Additionally (and this is a separate
matter) Andres' program appears to
treat all longitudes as Easterly, so
that a
negative. To me, this seems somewhat
perverse, though I am aware that many
programs (particularly for astronomy) do
so. We navigators work in hour
angles (GHA and LHA) for our positions
of bodies in the sky, and those hour
angles are always measured Westwards, so
that they always increase with
time. An hour angle is nothing else but
the longitude of the body, measured
longitudes exactly the same way, so that
we simply difference the longitudes
to get local hour angle? Meeus is an
astronomer who sets us a sensible
example. It seems madness to measure
hour-angles as positive Westwards, and
longitudes as positive Eastwards. Can
anyone really justify it?
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