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    Re: Beginner
    From: George Huxtable
    Date: 2005 Sep 10, 23:04 +0100

    Geoffrey Kolbe wrote-
    
    >At 18:13 10/09/2005, Willem Piccer wrote:
    >
    >>I was just re-reading the discussion on the problems Asbjorn had and I
    >>wonder if the whole problem is not caused by the gps position used.
    >>Especially because he states that the observation height is always less
    >>than the calculated height.
    >>I have the feeling that the chart datum chosen plays a role
    >>
    >>Willem Piccer
    >
    >
    >The latitude and longitude which Asbjorn's GPS deduces for Trondheim (where
    >Asbjorn says he took the sights) agree with that given in various atlas's
    >and gazetteers that I have to less than a minute. A glance at the atlas
    >shows that a position five miles North and East of Trondheim (where Asbjorn
    >would have to be to get an observed altitude 5 minutes less than
    >calculated) would put him in Trondheims Fjord....!
    >
    >Asbjorn would appear to be where he thinks he is.
    
    Response from George-
    
    Not necessarily so. He would not have to be at the place that Geoffrey has
    specified, to get an observed altitude 5 minutes less than calculated.
    Anywhere on a position line passing through that point, and perpendicular
    to the Sun's azimuth, would fit his observation. So he would not have to be
    in Trondheim's Fjord. Still, it would be useful if Asbjorn would confirm
    (or not) whether that GPS position corresponds well to his place of
    observation.
    
    There remains something of a mystery about Asbjorn's big discrepancy, in
    what should be a very accurate observation. Perhaps he will repeat his
    measurement, next time the Sun shines in Trondheim, and before it gets too
    low to observe well from his Northerly latitude.
    
    And I would like to welcome Willem Piccer's first contribution to this
    list, from Zeeland, Holland.
    
    George.
    
    
    ===============================================================
    Contact George at george@huxtable.u-net.com ,or by phone +44 1865 820222,
    or from within UK 01865 820222.
    Or by post- George Huxtable, 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13
    5HX, UK.
    
    
    

       
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