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    Hello (+ a few questions)
    From: R.H. van Gent
    Date: 1999 Feb 08, 4:50 AM

    Hello, my name is Robert van Gent and I am a new member to this list. I
    am interested in the history of astronomy and its application in related
    fields such as calendars and navigation.
    I joined this list in the hope that questions relating to the history of
    navigational sciences and techniques would also be discussed on this
    platform, but if I am seriously mistaken, I would be grateful if someone
    on this list could set me on the correct path (or should I say course?).
    I have two questions which I hope someone on this list can help me with.
    1) I am trying to locate an obscure reference cited in Bowditch�s
    _American Practical Navigator: An Epitome of Navigation_ (p. 423, 1958
    edition; vol. II, p. 546, 1977/81 edition) to a study performed by the
    Carnegie Institute of Washington on the application of the standard
    formula for the correction for dip:
      dip (minutes of arc) = 0.97 sqrt(h[ft])
    with 'h' denoting the height of the observer�s eye above sea level in
    The constant 0.97 in the above relation depends on the local atmospheric
    conditions and the quoted value applies to average weather conditions.
    The studies by the Carnegie Institute appear to have been made to verify
    how well this relation stands up to varying weather conditions and how
    large the deviations can be in extreme cases.
    I would be most grateful if someone on this list can provide me with a
    more complete reference to this study.
    2) My second question is of a more cartographical nature. After
    inspecting several 20th-century atlases I noticed that in each source
    the International Date Line (IDL) is drawn along a slightly path and
    that no two atlases agree completely. Is there such a thing as an
    Internationally agreed Date Line? If so, who decides on these matters?
    And what do countries who straddle the IDL have to say in this matter?
    As everyone probably already knows the issue has become more complicated
    since 1995 when the island Republic of Kiribati decided to shift the
    IDL, which bisected the country, to follow its eastern boundaries. Which
    leads to another question again: what are the internationally recognized
    borders of Kiribati? Again different recent atlases represent them
    slightly differently.
    I measured a set of approximate co-ordinates for the corner points
    defining the eastern boundary of Kiribati from the _National Geographic
    Atlas of the World_ (6th ed., 1992). Rounded to the nearest degree, I
    found the following latitudes and longitudes (positive in eastern
    Does anyone on this list know how to obtain more accurate figures?
    Happy sailing to all.
    * Robert H. van Gent * Tel/Fax:  00-31-30-2720269              *
    * Zaagmolenkade 50   * E-mail:   r.h.vangent@astro.uu.nl       *
    * 3515 AE Utrecht    * Home page (under construction):         *
    * The Netherlands    *           http://www.fys.ruu.nl/~vgent/ *
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