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    Re: Artificial Horizon
    From: Richard M Pisko
    Date: 2011 Jul 24, 20:16 -0600

    On Wed, 13 Jul 2011 06:08:37 -0600, G Becker 
    wrote:
    
    > The plane table is a lost art, what are you mapping? How are you
    > transferring the north information from the sextant to the location of
    > the table?
    
    I did not see an answer to your question, possibly because it was a
    private communication or possibly my server did not pick it up.
    
    At any rate, my best guess for the use of a sextant would be for
    determining differences of elevation between objects of known distance,
    although an Abney level would be more convenient.  For traditionalists,
    the Indian pattern Clinometer has an angle scale and a tangent scale.
    More accuracy, both in reading the vertical angles and in sighting the
    objects, may be had from various telescopic alidades, most of which will
    have tangent scales or Beaman stadia arc scales in addition to the
    vertical angle and accompanying vernier scales.
    
    The table may be roughly oriented by a compass and a line on the sheet
    pointing to magnetic north (allowing for magnetic variation), and more
    accurately by a Solar compass sheet, knowledge of Latitude and Longitude,
    and an accurate watch; but the table is most easily oriented by trial and
    error as a three point resection problem (if suitable known points are
    already plotted on the sheet).
    
    --
    Richard . . .
    
    Using Opera since the"Dog" died
    
    
    
    

       
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