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    Re: Compass Checks at Sea
    From: George Huxtable
    Date: 2008 May 23, 09:57 +0100

    Jeremy's mailings have provided several interesting surprises, to me.
    
    One is the frequency of checks made on the gyrocompass, once per watch.
    Presumably, there's much cautious overkill in those arrangements. Otherwise,
    how would ithe navigation cope with a prolonged period of cloudy weather,
    when no such checks are possible? Does the navigator get uneasy under such
    conditions, and if so, after how long? Might he then revert to
    cross-checking against the magnetic compass, with all its known
    deficiencies?
    
    Another surprise, at first sight, was the use of Polaris for checking
    azimuths. In our waters, we would never even consider that, Polaris being 50
    degrees up in the air. But for denizens of the Northern tropics, of course,
    Polaris is a nice low star for such purposes, always in place.
    
    Another surprise, in the first exercise, was his mention of a vessel
    drifting. To me, merchant vessels are either travelling purposefully, under
    way on passage from A to B, or they are in harbour, never adrift. That led
    me to suggest that the exercises might be, to some extent, contrived ones,
    and it was refreshing to be assured that no, they would be real-life.
    
    George.
    
    contact George Huxtable at george@huxtable.u-net.com
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    
    
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