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    Re: Wobbly Prime Meridian
    From: Peter Fogg
    Date: 2010 Nov 23, 12:31 +1100
    To address belatedly Scott's specific question:
    "How far off is this in nautical miles?"
    Well a minute of arc at the earth's surface, or a nautical mile, is defined as 1,852 metres, so 0.088 of that is about 163 metres but guess what?  This ain't accurate either!  

    One problem is that the surface of the world is somewhat lumpy so the length of a minute of arc varies in practice.  Another issue is that of oblateness; the poles are somewhat squashed while the equator bulges out.  Plus the surface level of different oceans, even one side of an ocean compared with the other side, varies too.  And so on...

    Apache Runner wrote:
    Sort of like quoting the right ascension of Polaris.....

    On Mon, Nov 22, 2010 at 4:55 PM, Peter Fogg <piterr11@gmail.com> wrote:
    There is a moral in this tale and it is this:
    Nothing, but nothing in the real world, is quite accurate.  T'aint possible.  No can do.
    Perfect accuracy belongs to the conceptual or imaginary universe; that of ideas and definitions.
    So endeth the lesson.

    Scott O'Connor wrote:

    I recently stood astride the Prime Meridian at Greenwich and fired up my Garmin Nuvi GPS. The coordinates read N 51 28.674' W 000 00.088'. Why the error? Is this due to nutation wobble? If so, when would it read exactly zero? How far off is this in nautical miles? It would appear to be far too minimal to consider for celestial nav work with a sextant, but is this a consideration? thanks very much.

    Keeping up with the grind

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