Care must be taken not to confound the "statute mile" established by
Queen Elizabeth and the "statute mile" used in the United States. The
former established a hierarchy of subdivisions which remains: miles,
furlongs, rods (or poles or perches), yards, feet. The U.S. statute mile
differs in size from the statute mile used in Queen Eliazbeth's time.
Today, the U.S. statute mile is 5280 survey feet; the survey foot is
defined as (1200/3937) meters. Queen Elizabeth did not have the meter at
her disposal so her statute mile was of a different size than ours since
her foot was of a different size. We did, however, retain her ratios for
the "English" subdivisions mentioned.
The survey foot was established by announcement in the Federal Register
in 1959 (F.R. Doc. 59-5442). Two places in which this can be read are
http://www.ngs.noaa.gov/PUBS_LIB/FedRegister/FRdoc59-5442.pdf
http://lamar.colostate.edu/~hillger/laws/sp447-app5.pdf
The U.S. statute mile equals 5280 survey feet as defined in this document.
Concerning the issue of North American Datum of 1983 (NAD 83) adoption
by the states, as mentioned by John Steele in USMA:47228, one might wish
to read this Federal Register announcement:
http://edocket.access.gpo.gov/2007/07-6026.htm (2007)
This follows the policy statement
http://www.ngs.noaa.gov/INFO/Policy/st_plane.html (1991)
It is clear that at the time this document was published confusion
lingered among the states and users of survey data when trying to deal
with geodetic data in feet. Fortunately, NAD 83 and State Plane
Coordinates (SPCs) are intrinsically metric. All data in feet are
calculated from that metric basis, whether correctly or incorrectly
done. Further information is found at the recent document
http://www.ngs.noaa.gov/faq.shtml#Feet (2010)
It states that the National Geodetic Survey uses the meter. Now,
according to this document, 24 states legislated using the survey foot
conversion factor, 8 states the international foot conversion factor,
and 18 states have no specified conversion factor. But currently the NGS
publishes only 7 states' SPCs using the survey foot to add tick marks in
that scale, 1 using the international foot to add tick marks, and 42
states' SPCs are published only in meters (no foot tick marks added).
From that documemt, I extracted this:
"So, NGS does NOT have an "official" conversion factor. NGS works in
meters ONLY. NGS only uses feet to publish SPCs, and those are
converted from meters using the conversion factor as defined by the
individual states who have requested that we publish SPCs in feet."
Elevations are worked in meters by NGS as well, and there the survey
foot is used for the conversion to a foot scale. A name and email
address are included in this last document for further inquiries.
Since ocean depths are "elevations", the U.S. fathom is based on the
survey foot.
Since the U.S. gallon and the U.S. bushel are based on the size of the
official U.S. inch, which is now the international inch (1/12 of an
international foot), or 25.4 cm exactly they, too, shrank in size when
the U.S. foot shrank in size. The latter was about 2 parts in a million,
making the shrinkage of the gallon and the bushel in 1959 about 6 parts
in a million.
Let us recall that the first survey commissioned by the United States,
that of its east coast, was done in terms of the meter. The U.S. Coast
and Geodetic Survey, later the National Geodetic Survey, have continued
doing their base calculations in terms of the meter.
Jim Frysinger, LCAMS
--
James R. Frysinger
632 Stony Point Mountain Road
Doyle, TN 38559-3030
(C) 931.212.0267
(H) 931.657.3107
(F) 931.657.3108
