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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.

gl

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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