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    Re: Great Circle Course via calculator & HO 208
    From: Bill B
    Date: 2016 Oct 5, 01:33 -0400

    On 10/4/2016 11:38 PM, David Fleming wrote:
    > In any event the path connecting ponts 1 degree of longitude at 41N are
    > not significantly different fron a great circle path.
    Seriously? The small circle at parallel 41 is "not significantly
    different fron a great circle path?"
    "A great circle, also known as an orthodrome or Riemannian circle, of a
    sphere is the intersection of the sphere and a plane that passes through
    the center point of the sphere. This partial case of a circle of a
    sphere is opposed to a small circle, the intersection of the sphere and
    a plane that does not pass through the center. Any diameter of any great
    circle coincides with a diameter of the sphere, and therefore all great
    circles have the same circumference as each other, and have the same
    center as the sphere. A great circle is the largest circle that can be
    drawn on any given sphere. Every circle in Euclidean 3-space is a great
    circle of exactly one sphere." --Wikipedia
    "A great circle is the largest possible circle that can be drawn around
    a sphere. All spheres have great circles. If you cut a sphere at one of
    its great circles, you'd cut it exactly in half. A great circle has the
    same circumference, or outer boundary, and the same center point as its
    sphere. The geometry of spheres is useful for mapping the Earth and
    other planets. The Earth is not a perfect sphere, but it maintains the
    general shape. All the meridians on Earth are great circles. Meridians,
    including the prime meridian, are the north-south lines we use to help
    describe exactly where we are on the Earth. All these lines of longitude
    meet at the poles, cutting the Earth neatly in half. The Equator is
    another of the Earth's great circles. If you were to cut into the Earth
    right on its Equator, you'd have two equal halves: the Northern and
    Southern Hemispheres. The Equator is the only east-west line that is a
    great circle. All other parallels (lines of latitude) get smaller as you
    get near the poles. Great circles can be found on spheres as big as
    planets and as small as oranges. If you cut an orange exactly in half,
    the line you cut is the orange's great circle. And until you eat one or
    both halves, you have two equal hemispheres of the same orange. Great
    circles are also useful in planning routes. The shortest path between
    two points on the surface of a sphere is always a segment of a great
    circle. Plotting great circles comes in very handy for airplane pilots
    trying to fly the shortest distance between two points. For example, if
    you flew from Atlanta, Georgia, to Athens, Greece, you could fly roughly
    along the path of one of Earth's great circles, which would be the
    shortest distance between those two points. When planning routes,
    however, pilots have to take other factors into account, such as air
    currents and weather. Great circles are just general paths to
    follow."--National Geopraphic

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