Hectare


The hectare is a non-SI metric unit of area equal to a square with 100-metre sides, that is, 10,000 square metres, and is primarily used in the measurement of land. There [|are] 100 hectares in one square kilometre. An acre is about and thus one hectare is about.
File:St. Enda's GAA ground, Omagh - geograph.org.uk - 556880.jpg|thumb|St. Enda's GAA ground, in Omagh. The playing field used in Gaelic football and hurling is a little over a hectare in size.
In 1795, when the metric system was introduced, the are was defined as 100 square metres, or one square decametre, and the hectare was thus 100 ares or km2. When the metric system was further rationalised in 1960, resulting in the International System of Units, the are was not included as a recognised unit. The hectare, however, remains as a non-SI unit accepted for use with the SI and whose use is "expected to continue indefinitely". Though the dekare/decare daa and are are not officially "accepted for use", they are still used in some contexts.

Description

The hectare, although not a unit of SI, is the only named unit of area that is accepted for use with SI units. The name was coined in French, from the Latin ārea. In practice the hectare is fully derived from the SI, being equivalent to a square hectometre. It is widely used throughout the world for the measurement of large areas of land, and it is the legal unit of measure in domains concerned with land ownership, planning, and management, including law, agriculture, forestry, and town planning throughout the European Union, South Africa, New Zealand, Australia, Canada and the United Kingdom.
However, the United States and Myanmar use the acre instead of the hectare for measuring surface or land area.
In many countries, metrification redefined or clarified existing measures in terms of metric units. The following legacy units of area have been redefined as being equal to one hectare:
In Mexico, land area measurements are commonly given as combinations of hectares, ares, and centiares. These are commonly written separated by a hyphen; for example, 1-21-00.26 ha would mean 1 hectare, 21 are, and 0.26 centiare.

History

The metric system of measurement was first given a legal basis in 1795 by the French Revolutionary government. The law of 18 Germinal, Year III defined five units of measure:
  • The :metre for length
  • The are for area
  • The stère for volume of stacked firewood
  • The :litre for volumes of liquid
  • The gram for mass
In 1960, when the metric system was updated as the International System of Units, the are did not receive international recognition. The International Committee for Weights and Measures makes no mention of the are in the 2019 edition of the SI brochure, but classifies the hectare as a "Non-SI unit accepted for use with the International System of Units".
In 1972, the European Economic Community passed directive 71/354/EEC, which catalogued the units of measure that might be used within the Community. The units that were catalogued replicated the recommendations of the CGPM, supplemented by a few other units including the are whose use was limited to the measurement of land.

Unit family

The names centiare, deciare, decare and hectare are derived by adding the standard metric prefixes to the original base unit of area, the are.

Decimilliare

The decimilliare is are or one square decimetre. Such usage of a double prefix is non-standard. The decimilliare is 2 or roughly a four-inch-by-four-inch square.

Centiare

The centiare is one square metre.

Deciare

The deciare is ten square metres.

Are

The are is a unit of area, equal to 100 square metres, used for measuring land area. It was defined by older forms of the metric system, but is now outside the modern International System of Units. It is still commonly used in speech to measure real estate, in particular in Indonesia, India, and in various European countries.
In Russian and some other languages of the former Soviet Union, the are is called sotka. It is used to describe the size of suburban dacha or allotment garden plots or small city parks where the hectare would be too large. Many Russian dachas are 6 ares in size.

Decare

The decare or dekare is derived from deca and are, and is equal to 10 ares or 1000 square metres. It is used in Norway and in the former Ottoman areas of the Middle East and Bulgaria as a measure of land area. The names of the older land measures of similar size are usually used, redefined as exactly one decare:
The most commonly used units are in bold.
One hectare is also equivalent to:
  • 1 square hectometre
  • 1.008 Tsubo
  • 2.381 feddan
  • 6.25 rai
  • 10 dunam or dönüm
  • 10 stremmata
  • 15 Chinese units of measurement#Area or 0.15 qǐng

    Unicode

The Unicode character, in the CJK Compatibility block, is intended for compatibility with pre-existing East Asian character codes. It is not intended for use in alphabetic contexts.
is a combination of ヘクタール, the Japanese translation of "hectare".