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    Re: Averaging sights on commercial vessels
    From: Trevor Kenchington
    Date: 2004 Oct 7, 21:22 +0000

    Alexandre,
    
    Stacy has given a better date for the introduction of SatNav than I
    could have done. (I suspect that I first encountered a receiver in about
    1979. It was certainly not new technology for the ship's officers at
    that point.)
    
    
    As to other ocean navigation systems: LORAN-C has a range of a few
    hundred miles from the transmitters, which are necessarily on land. The
    range at night, using skywaves, is often longer than by day. I think
    LORAN-A had a longer range though much lower precision.
    
    There were other systems of similar vintage and similar range to
    LORAN-A: CONSOL for one. (Back in the 1970s, I sailed with yachtsmen who
    used CONSOL for navigation off the English coast. It didn't need any
    receiver more sophisticated than an ordinary AM transistor radio.) All
    of those systems had their origins in aids to wartime (1939-45) air
    navigation.
    
    To the best of my knowledge, the only civilian non-statellite electronic
    navigation system which could reach to mid-ocean was Omega, which was
    relatively low precision (though maybe not much worse than celestial). I
    have never seen an Omega receiver, and only once an Omega lattice chart,
    and I don't know how widely it was ever used. The system was either in
    place by 1975 or was being constructed then. (What other systems the
    military had, or the Soviet Bloc had, I do not know.)
    
    There was, of course, RDF which could provide mid-ocean radio bearings
    by the 1940s and maybe much earlier. I think its precision was well
    below that of celestial.
    
    
    None of which concerns the proper theme of NAVIGATION-L, except as
    markers for the decline of celestial methods in everyday use.
    
    
    Trevor Kenchington
    
    
    You wrote:
    
    > Trevor,
    > Thank you very much for your explanation.
    > I forgot about Sat Nav indeed.
    > Do you know when approximately did they start using it?
    > (I suppose, not earlier than late 70-s).
    > The manuals I cited were written in the 60-s when
    > no Sat Nav existed.
    > I am just trying to understand when CelNav was replaced
    > by various satellite-based systems as a main tool of finding
    > position on commercial and navy ships.
    > Alex.
    >
    > P.S. LORAN only works near a shore, correct?
    > The only precise means available in the middle of an ocean
    > are CelNav and satellite-based systems, correct?
    > A
    
    
    --
    Trevor J. Kenchington PhD                         Gadus{at}iStar.ca
    Gadus Associates,                                 Office(902) 889-9250
    R.R.#1, Musquodoboit Harbour,                     Fax   (902) 889-9251
    Nova Scotia  B0J 2L0, CANADA                      Home  (902) 889-3555
    
                         Science Serving the Fisheries
                          http://home.istar.ca/~gadus
    
    
    

       
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