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From: George Huxtable (no email)
Date: Sat Jun 04 2005 - 03:41:59 EDT
Bill Noyce wrote-
>Perhaps the fact that "longitude by noon sun" comes up so often
>is a good reason that there *should* be a discussion of this
>method, pointing out why it is a bad idea...
>
>Is there any other observation that gives longitude without
>knowing latitude first? Maybe this is part of its appeal.
================
To my mind, finding latitude at noon is a trivial matter that presents a
problem only when the sky is cloudy at noon.
To answer Bill's question, if a time-sight is taken at the moment when the
Sun is due East or due West of the observer, then his latitude isn't needed
at all in calculating local time-by-the-Sun. But that can only happen in
the Summer months.
But why, in this age, does a mariner still ask for separate determinations
of latitude and longitude? It's as if we were still stuck in the early
1800s, and Sumner and St Hilaire had never invented position lines. Why not
just measure two altitudes of the Sun, at any old times, but times which
are well separated so that the Sun's azimuth has changed significantly
between them. Then draw a couple of position lines from some assumed
position, allow for vessel's run in the interval, see where they cross, and
that's where you are, in lat and long. Simple as that. Applies to any sight
of any body at any time: a universal way of doing the job. Who needs
anything different?
George.
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contact George Huxtable by email at , by phone at
01865 820222 (from outside UK, +44 1865 820222), or by mail at 1 Sandy
Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
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