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    Re: Refraction at the horizon.
    From: Frank Reed
    Date: 2008 Mar 16, 00:30 -0400

    Marcel, you wrote:
    "The practical problem is very likely that you don't have the atmospheric
    data from 50 to 150 miles out of to sea. When calculating refraction
    numerically one deals "generally" with an atmospheric model assuming that
    the atmosphere is horizontally homogeneous, i.e. an air layer at a certain
    height has everywhere the same temperature and pressure independent of the
    distance from the observer."
    I agree. This might be fun to explore. The standard approach to calculating
    refraction assumes no variation in the atmosphere in the horizontal
    direction. That is, the vertical temperature profile is the same at all
    points across the surface of the (spherical) Earth. However, it's not really
    a big deal to do a more sophisticated integration. Rather than working with
    an integration method like Auer-Standish, what's required is a complete
    ray-tracing system for a continuous medium. That would cover all
    possibilities. I wouldn't be at all surprised if there's software that does
    that already for purposes of digital landscape simulation.
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