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    Re: horizon visibility puzzle
    From: Hal Mueller
    Date: 2001 Jun 20, 2:25 PM

    At 12:17 PM -0700 6/20/01, Paul Hirose wrote:
    >You are ashore, 777 meters above sea level, looking toward the ocean.
    Horizon distance is 58.4 nm from your location, or 108.2 km.  There's
    a point out on the ocean, call it A, which is on the line containing
    your position and the hilltop.  "A" is the farthest point on that
    line that you can see (and it's the farthest point that someone at
    sea level can see you).
    >In your line of sight, 35 kilometers away, is a hill 401 meters high.
    Horizon distance is 42.0 nm from this hilltop, or 77.8 km.
    >Can you see the ocean over the top of this hill?
    Point A is
    (108.2 - 35) km from the hilltop, or 73.2 km.  You can see the
    hilltop from Point A.  Thus, the hilltop blocks your view from your
    ashore location.
    Hal Mueller                hal@mobilegeographics.com
    Mobile Geographics LLC     http://www.mobilegeographics.com/
    Seattle, Washington        (206) 297-9575
    Get CelestNav 2.2.2!  http://www.mobilegeographics.com/celestnav/

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