Midwest

[James A. Landau]

In a message dated 02/22/2002 8:41:14 PM Eastern Standard Time,
Hixmaddog at AOL.COM writes:

> I recall a survey done (among college-students) by geographers a few years
>  ago, asking "where is the center of the Midwest ?"  Kansas and Missouri
came
>  in as the #1 and #2 answers, I believe: except in North Dakota, where
"North
>  Dakota" was by far the #1 answer.

Aha! A chance to bore everybody:

The center of the United States is in Kansas, specifically at a point a
little west of Topeka known as "Mead's Ranch".  There is a monument there
marking the exact geographical center of the United States.  (More precisely,
of the "lower 48".  If you add in Alaska, the geographic center of the US is
somewhere in the Dakotas.)

And the significance of Mead's Ranch?  All latitudes and longitudes in the
United States are measured from that point.

Why?

Don't you remember that the earth is pear-shaped?  Unfortunately there are no
usable mathematical formulae for pears, just for spheroids.  Therefore US
maps are based on the "Clarke spheroid of 1866", which is designed so that it
coincides with the real earth at Mead's Ranch.  The further you get from the
point where the real and the mathematical earth coincide, the greater the
discrepancy.  In the best democratic tradition, by placing the point at the
geographical center (actually, I think the proper term is "geodetic center")
of the US, both coasts suffer from equal errors.  What could be fairer?

To give you an idea of the importance of these geodetic considerations:
England's equivalent of Mead's Ranch is of course the Greenwich observatory,
from which all those ill-tempered verdant sorceresses broadcast Mean Green
Witch Time.  (No, Greenwich is not the geographical center of Great Britain,
but it is still the point from which latitude and longitude is computed.
Also, those green witches have been replaced by Africans, which is why we now
refer to "Zulu time".)

Back in the Victorian era, a survey was made of all of Great Britain, and
those working on the survey were puzzled to find numerous errors which, to
their great bafflement, were always equal to nineteen feet.  Eventually the
puzzle was solved.  It seems that generations earlier the staff at Greenwich
had thoughtlessly moved the Prime Meridian marker from one building to
another that was nineteen feet away in an east-west direction.  Well, you
can't blame them too much, as it did take well over a century before anyone
noticed.

Germany and probably much of the rest of Europe uses the Bessel Spheroid of
1840, which coincides with the real earth at Potsdam (that being the
observatory at which Bessel was working.)  During World War II the Allies had
to convert all of their maps of Germany from the Bessel Spheroid to the
Greenwich Spheroid so that bombers doing "precision bombing" by radio beam
would be on target.

To find the difference between Bessel and Greenwich, a radio-guided bombing
mission was sent against a German installation in coastal Europe and the
Resistance was then sent in to map the exact location of each bomb crater on
the Bessel map, which could then be matched against the bomb-dropping
locations, known from the Greenwich map.

My father once was writing an article on measuring the earth, and discovered
that the one person in town who was an expert in the field was my mother, who
had worked during World War II on converting Bessel to Greenwich.

    James A. Landau (systems engineer and second-generation mathematician)