Date: Thu, 02 May 2002 14:49:27 -0400

Author: "James R. Frysinger"

Subject: Re: units of measurement

Post:

Good questions, Paul!

I doubt very much that any level of government has pockets deep enough
to go out and move mile-stone markers any time soon, even if there was a
desire or need to do so. (By the way, they didn't come even close to
setting those up "all over the country" -- not by a country kilometer.)
I grew up in northwest Ohio and there, too, political and property
boundaries were laid out on the basis of old surveying plats. A township
is 36 square miles, a square mile is 640 acres, and all that.

A funny thing happened in 1959, though. At that time the U.S. and the
U.K. changed the size of their respective yards, setting them equal to
each other by defining both of them as being exactly 0.9144 m. The
British yard became larger and the American yard (defined as 3600/3937 m
in 1893) became smaller as a result. But the U.S. Coast and Geodetic
survey started hearing a lot of beefs from surveyors, tax assessors, and
the like about changing the size of the mile, chain, pole (or rod),
fathom, and foot as a result of changing the base unit, the yard.
(Surveyors subdivide the foot into hundredths, not into inches.) As a
result, and because the USCGS was doing all national mapping in meters
at the time (though rescaling and printing the maps in miles), the USCGS
decided not to pay to change all those old records (by rescaling the
numbers), so they kept the old units and called them the survey foot and
the survey mile, for example. This was covered by a statute so that's
how "statute mile" came to be in the U.S. (The British statute mile
arose from a statute passed by Parliament in the time of Elizabeth I.)
The relative difference between the statute and the "international" mile
is about 2 mm/km, not a very big number!

The GPS system and the geoids it works with are all metric. There is
"universal" system used today to give exact locations in the U.S., which
matches up with GPS, and that is all metric. So, if you use your old
county maps, you can give your address in perches, chains, and miles.
Or, you can turn on your GPS and give it metrically -- all without
setting foot off your front porch. Check your topographic maps to see

I've got a brother named William but we call him Bill. Two names, same
guy. You've got two addresses, same place. (If it was surveyed after
1893, the miles used were defined in meters so you can rescale it if you
wish to.) Sit tight, if it's yours.

Jim

Paul Nord wrote:
>
> I suppose so. Do tell me one thing, though... I live in the country. My
> address is 862N 200W; a grid location on the country map -- which was laid
> out and surveyed a hundred years ago by the USGS. I live on a road that's
> 2 miles west of the county courthouse, my house is 8.62 miles north of it.
> Does your metrication plan include money to move all the roads? Or do I
> become 1380N 320W?
>
> In fact, the USGS set survey markers in every square mile of the country.
> They mark the location in degrees (I think) and elevation in feet. Are
> you planning to move those, too?
....

--
James R. Frysinger University/College of Charleston
10 Captiva Row Dept. of Physics and Astronomy
Charleston, SC 29407 66 George Street
843.225.0805 Charleston, SC 29424
http://www.cofc.edu/~frysingj frysingerj@cofc.edu