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    Re: The length of a meter, was:Timing Lunars with a Rock
    From: Richard B. Langley
    Date: 2005 Jul 20, 09:33 -0300

    See also .
    -- Richard Langley
    On Tue, 19 Jul 2005, Jared Sherman wrote:
    > latitude in degrees and minutes, all one has to do is divide the northing
    >reference by 1852, then by 60, to come up with the right answer, but this is
    >not the case. >
    > I think the key word is "theoretically".
    >AS  I understand it, UTM is based on a perfect cylinder, a Mercator
    >Projection, for the bulk of the world (outside the polar areas) and given
    >that distorted projection, your theoretical conversion works perfectly well.
    >But from the references online it seems that the system is NOT designed to
    >be converted that way. Rather, the linear mileage (meterage?) is marked off
    >on each topo quad, and you are supposed to either draw on the quad or use an
    >overlay on it. The primary purpose is military, i.e. artillery, where maps
    >will be distributed and the only question is how to tell the big guns
    >exactly where you are on the map that you were given. UTM works very well
    >for that, or for anything else where you are using paper quads.
    >See http://erg.usgs.gov/isb/pubs/factsheets/fs07701.html
    >and http://ask.usgs.gov/ where the USGS provides PHONE and email contacts
    >for folks to ask questions.
    >I know there are conversion utilities for computer use, but I suspect they
    >are either referencing offset tables, or counting distance and accounting
    >for the distorted globe. Not something you'd want to do by hand.
    >I'll let you ask the prime authority directly--I know UTM has become popular
    >with hikers, but I can work with degrees and have had no need or use for
     Richard B. Langley                            E-mail: lang@unb.ca
     Geodetic Research Laboratory                  Web: http://www.unb.ca/GGE/
     Dept. of Geodesy and Geomatics Engineering    Phone:    +1 506 453-5142
     University of New Brunswick                   Fax:      +1 506 453-4943
     Fredericton, N.B., Canada  E3B 5A3
         Fredericton?  Where's that?  See: http://www.city.fredericton.nb.ca/

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