So in States that passed the International foot legislatively, NGS is issuing product that uses the International foot for horizontal coordinates, and Survey feet for vertical coordinates? That's just great. (But it makes a great argument for just going metric.)
________________________________ From: James R. Frysinger <[email protected]> To: U.S. Metric Association <[email protected]> Sent: Thu, April 22, 2010 12:45:37 PM Subject: [USMA:47236] The survey foot and the statute mile 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
