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    Distance on ellipsoid
    From: Jim Easton
    Date: 1996 Oct 30, 12:51 EST

    It is not clear to me what all of the fuss is about regarding distance. I would
    hope that anyone trained in navigation could calculate great circle distances.
    I believe that there are numerous references to calculating distances
    on a sphere. I personally usually go back to the ITT Radio engineers
    handbook for their formulas.
    A more interesting issue is distance on a reference ellipsoid -- which is
    theoretically what one should really be doing. The precise formula
    involves elliptic integrals -- not just trigonometric functions. I have not
    kept up with the new editions, but Bowditch used to have formulas approximating
    the exact calculations.
    One needs to be a little cautious implementing these formulas on a computer
    since there may be ambiguities due to the multiple valuedness of inverse
    trig functions & some of the formulas blow up or become less accurate
    under certain input values.
    If anyone is interested, I will try to find the "real" formulas.
    Jim Easton
    4364 Bonita Rd., No. 166
    Bonita, CA, 91902-1421
    Tel: (619) 548-0138
    FAX: (619) 470-8616

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