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    Re: Q: how to calculate refraction at higher altitudes on land?
    From: Dov Kruger
    Date: 2002 Feb 28, 14:26 -0500

    Craig wrote:
    >If you can see the top of a nearby mountain, measure the angle above (or
    >below) horizontal, use the topographic map for mountain top coordinates,
    >waypoint mountain top and your position, obtain distance (easy with GPS),
    >use trigonometry for difference in opposite side, which is difference
    >between your height and mountain top, simple math, and voila!
    This is an interesting idea, but you don't know your own altitude, and
    you therefore don't know the difference in altitude.
    You can use the current uncertain altitude as a starting point and
    iterate perhaps.
    If GPSs display the straight line distance between two points including
    altitude, then I am unaware of it. I do not even know if I can enter the
    altitude of a waypoint on my GPS.
    I don't think this is quite so easy as Craig says ;-)

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