Foot (unit)

The Roman foot

The foot in France

The foot of Saint Lambert

The foot of Holy Lambert ( wa: pi d' Sint Lambiet) is an old measuring unit which had course in the Principauté of Liege, and whose value was of approximately 291,8 Misters.

This foot is quasi-identical to, which is perhaps explained by the fact why several Prince-bishop S of Liege resulted families from Bavaria. Moreover, with Hanover in Germany, one also had course.

The ratio between the foot of Saint Lambert - respectively the foot of Bavaria - and the bent of Nippour is of 18: 32, i.e. bent of Nippour, a tradition pluri- Millénaire was regarded as a double-foot and was divided consequently initially by two then by sixteen. 518,6 mm/32 = 16,2 (0625) Misters Of this finger of a little more 16,2 mm was created - as often in old times - a pygme of 18-fingers. 16,20625 X 18 = 291,7 (125) Misters C' is the foot of Saint Lambert.

Like all the feet of the the Middle Ages, it was divided into 12 inches or 144 lines.

After the creation of the metric system in France - more precisely between the Congress of Vienna of 1815 and the signature of the Convention of the Meter by the Belgium in 1875 - the Engineer S of the Civil engineering of the area of Liege, in particular with the Highways Departments, started to use a foot of St Lambert décimalisé : 1 foot = 10 pôces = 100 royes.

The Roman foot itself and bent of Nippour maintains a ratio 16: 28. It follows that the relation between the Roman foot and the foot of St Lambert is of 63: 64.

The Anglo-Saxon foot

The foot (in English: foot in the singular and feet in the plural) symbol: ft or ′, for example, 30 ' 6" what means 30 feet and 6 inches, is a unit of length of the system of units of many Anglo-Saxon countries of which, in particular, the United States, where it is the official system (as well as IF, legally), like in the United Kingdom, although this last adopted the decimal metric system in 1995.

The English foot of the imperial Système of unit is a measuring unit directly deducted from the systems of Antiquity. The English foot is worth - at least in theory - exactly the 16/28 of a measurement known in Antiquity called “pechys basilikos”. That corresponds to the 36/35 of the Roman foot or to the 15/16 of the French foot.

According to the official figure of the year 1922, the English foot was a little shorter than today: 304,799 472 Misters the American foot of the United States was definite slightly larger than in the United Kingdom, namely exactly 1200/3937 m for U.S. Survey foot (a convertion rate adopted into 1866: (Kasson) Metric Act, Public Law 39-183). This American foot is sometimes still of use because of the difficulty of conversion of the old charts and land registers. Since the difference between these two definitions was very tiny, the Anglo-Saxon countries adopted in 1959 a foot of compromise by international treaty. Since:

1 ft = 0,3048 m

The foot is divisible in 12 inches (English inch ''). There are three feet in a Yard (in French: “rod”, official term with the Canada). This definition of the twentieth century currently official and is respected.

There existed, formerly, of the definitions length of the standards the most varied according to the countries, even the areas of the same country, in addition to the times. The British imperial foot also varied slightly with the wire of progress of geodesy. Nevertheless, these differences are generally in the Order of magnitude of some hundred-thousandth, even millionth, therefore not very significant. They go back very to a time when the English foot did not have yet a joint definition, internationally recognized, expressed in meters. These local definitions - just like foot U.S. Survey itself - gropings constituted to make this definition exactly.

Like examples, one can quote:

≈ 1,000 002 current English foot: the foot of the Geometrician S of the the United States (1866), in English U.S. Survey foot, equalizes 1 200/3 937 Mr.

≈ 1,000 040 2 current English foot: the foot of Michigan or “modified American foot” (“modified American foot”), for certain old women charts of this State, being worth 1,000 038 2 U.S. Survey feet.

≈ 0,999 991 current English foot: the “foot of the Cape” (Cape foot) or “foot of Clarke” (Clarke' S foot) uses the definition, given by A.R. Clarke in 1858 or 1865 : 1 ft = 0,304 797 265 4 Mr. It was used in South Africa, Australia and with the the Antilles (Jamaica, the Trinity-and-Tobago).

≈ 0,999 999 1 current English foot: The foot of Benoit (1895) who evaluates the meter with 39,370 113 Po, which gives a foot of 0,304 799 73 m; this value was especially used in Western Malaysia.

≈ 0,999 998 3 current English foot: The foot of Sear (1922) which evaluates the meter with 39,370 147 Po, a foot of 0,304 799 47 m; this value was especially used in Eastern Malaysia and New Zealand.

≈ 0,999 998 4 current English foot: Lastly, the “Indian foot ” (Indian foot) was initially fixed at 0,999 995 66 feet of 0,304 800 837 m and were worth thus 0,304 799 51 Mr. It will be revised in 1937, 1962 and 1975.

With share for some geodesists and highly specialized cartographers, these differences have today hardly practical interest.

The foot in the contemporary world

In the scientific world, including in the United States, the decimal metric system (IF) is the frame of reference today.

In the technical and industrial world, the measurements in inches and feet are still omnipresent, sometimes even in pseudo. Thus the Disquette S PC were conceived by their creators Japan board - country having adopted the metric system for a long time - with a size of 90 mm exactly. However, they are called " 3 ½ " in the whole world, with an error of a little less than one millimetre.

Currently, in England for example, the foot is very much used for the everyday usages. The majority lengths ranging between 50 cm and 500 m are expressed in this unit. It is the case for the size of the people, dimensions of a part, a boat or indication, on a panel, distance to be traversed with foot (the road panels are written in miles or fraction of mile).

In aeronautics, in the whole world, except in the countries of the ex- Soviet Union and in China, altitudes remain expressed in Anglo-Saxon feet. The levels of flight are given in hundreds of feet: FL180 = 18 000 ft.

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