Hectare - History

History

The metric system of measure was first given a legal basis in 1795 by the French Revolutionary government. The law of 18 Germinal, Year III (7 April 1795) defined five units of measure:

• The metre for length
• The are (100 m2) for area
• The stère (1 m3) for volume of stacked firewood
• The litre (1 dm3) for volumes of liquid
• The gram for mass

Although the law defined the length of the metre, there was no practical way of accurately measuring the metre (and hence the are) until 1799 when the first standard metre was manufactured and adopted.

The standard metre remained in the custody of successive French governments until 1875 when, under the Convention of the Metre, its supervision passed into international control under the auspices of the General Conference on Weights and Measures (CGPM). At the first meeting of the CGPM in 1889 when a new standard metre, manufactured by Johnson Matthey & Co of London was adopted, the are and hectare were automatically redefined.

In 1960, when the metric system was updated as the International System of Units (SI), the are did not receive international recognition. The International Committee for Weights and Measures (CIPM) makes no mention of the are in the current (2006) definition of the SI, but classifies the hectare as a "Non-SI unit accepted for use with the International System of Units"

In 1972, the European Economic Community (EEC) 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 (and implicitly the hectare) whose use was limited to the measurement of land.