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    Re: New inovation in astro navigation?
    From: Gary LaPook
    Date: 2010 Aug 04, 00:34 +0200

    I would ask the question a different way, "why wouldn't you keep
    celestial navigation as a backup navigation method?" It is proven,
    simple, requires only a sextant and a watch and some simple tables (or a
    flat Bygrave and eight pages making up a long term almanac) that take up
    little space. It's not rocket science. A good sextant can be purchased
    on eBay for a couple of hundred bucks but even cheaper sextants would be
    good enough for a backup, there are a number of Davis instruments on
    eBay right now in the $50 ~ 60 range.  And my three, $17.00 digital
    watches are still ticking away with very stable rates.
    Douglas Denny wrote:
    > Jim Wilson says:
    > "Natural catastrophes occur not only on earth but in space as well,
    > and a gigantic solar flare is one of those. None has occurred since
    > we've been monitoring them, but they are lurking. And a single one
    > could knock out all satellites!"
    > -------------
    > If there is a solar flare _that_ big it would have serious
    > repercussions on all communications systems and on Earth too.
    > Satellites are protected against EMP and solar flares. They are
    > designed to resist EMP of upper atmospheric nuclear explosions. The
    > solar flares are more likely to disrupt the ionosphere to give large
    > variability of propagation affecting position rather than killing the
    > satellites.
    > More likely in probability terms is 'selective availability' being a
    > problem: It is entirely possible for the Americans to have the
    > satellites switch off as they pass over selected parts of the globe,
    > or degrade the signals (as they used to do) to reduce positional
    > accuracy, or even move the parameters entirely for position, which
    > would make good sense if you knew a missile was coming your way which
    > was using GPS in a wartime scenario.
    > It is for this reason that the Europeans want their own satellite
    > navigation system independent of GPS with 'Galilleo', and the Russians
    > keep 'Glonas'. Even other nations want their own independent systems
    > despite the Americans declaring GPS would be inviolate from now on.
    > I think there should be an internationally controlled satellite
    > positional system where every country contributes to an international
    > funding for it through the United Nations, but control would be by the
    > UN. This would remove the duplication and huge costs for each system.
    > However .. I agree with you actually about the very valid point of
    > having an independent method available to find position; (as the
    > governments want too). There is no disagreement there. In my opinion
    > it would be foolish not to.
    > I personally would never venture offshore without the equipment for
    > astro-navigation at my fingertips.
    > Douglas Denny.
    > Chichester. England.
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