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    Re: Lewis and Clark, and River Navigation
    From: Frank Reed CT
    Date: 2003 Dec 11, 14:52 EST
    George Huxtable wrote:
    "Yesterday, I asked for algorithms for translating, in both directions,
    between UTM (Universal Transverse Mercator) zone 15, and ellipsoidal lat
    and long, to within, say, a quarter-mile."

    This is not as difficult as it may sound. A quarter-mile is a BIG error, so you don't need the "real" conversion formulae. All you have to do is get two corners with known values in both coordinate systems (e.g. by picking off two known towns and reading off their coordinates from the map) and interpolate. You could implement this easily with a spreadsheet. There are limits: essentially this method treats Missouri as flat, and for the accuracy you require, it is. If you cover a larger area, the errors will grow. This problem can be solved by choosing a maximum distance between corner points consistent with your error bars. But you shouldn't have to worry about that in this case.

    Frank E. Reed
    [ ] Mystic, Connecticut
    [X] Chicago, Illinois
       
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