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    What is a degree of latitude?
    From: Lu Abel
    Date: 2008 Mar 23, 11:17 -0700

    This seems quite silly, but I realize that I don't know the "official"
    definition of a degree of latitude.
    I'm sure most on this list know that the earth is an oblate spheroid --
    it's fatter than it is tall.   This means if I cut the earth in half
    through its poles, the resulting cross-section looks like an ellipse,
    wider than it is tall, rather than a perfect circle.   And this
    elliptical cross-section can lead to two possible definitions of a
    degree of latitude.
    If take a cross-section of the earth and draw an angle one degree up
    from the equator, is the place where this line intersects the surface of
    the earth the first (degree) parallel?   Or is the first parallel one
    ninetieth of the way from the equator to the pole?
    Years ago I took an offshore navigation course that taught the various
    "sailings," including use of the Meridional Parts table from Bowditch to
    determine a rhumb line course when traversing long distances (especially
    those with dramatic north-south differences).   (Meridional Parts give
    the "stretch" in the latitude scale required at various latitudes to
    create a Mercator chart).   As I recollect, the meridional parts down
    near the equator are actually slightly less than 1.00000, which would
    indicate that the first of my two definitions is the correct one.
    I know there are some experts in cartography on the list, I'm sure this
    is trivial for them.
    Lu Abel
    Navigation List archive: www.fer3.com/arc
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