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# Measurement system

This article has been reviewed by the following Topic Editor: Peter Saundry

A measurement system, also a system of units, is a consistent system of measurement units in which to express physical quantities.

The most commonly used scientific measurement system is the SI system, the Système International d'Unités, which is based on the fundamental units meter (m) for length, kilogram (kg) for mass, and second (s) for time.

All other units (with few exceptions) are based on these fundamental units, e.g., velocity is measured in the unit meters per second, or m/s. Units can be enlarged or reduced according to need: e.g., the unit of electrostatic capacity is the farad, named after Michael Faraday, but typical capacitors are measured in nanofarads (nF) or even picofarads (pF). Already the kilogram is such a scaled unit: a thousand grams.

Another metric system is the centimetre-gram-second system CGS or cgs system which is based on the fundamental units centimetre (cm) for length, gram (g) for mass, and second (s) for time.

The Imperial system is based on the fundamental units of foot (ft) for length, pound (lb) for mass, and second (s) for time. The Imperial system is widely used for certain purposes (e.g., miles for distance, miles/hour for speed, pounds for the weight of food stuffs) in the United States, United Kingdom, India, Canada and several other countries.

The science which studies the operational realization of measurement units is called metrology.

## Citation

Martin Vermeer (Lead Author);Peter Saundry (Topic Editor) "Measurement system". In: Encyclopedia of Earth. Eds. Cutler J. Cleveland (Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment). [First published in the Encyclopedia of Earth August 24, 2009; Last revised Date August 24, 2009; Retrieved May 23, 2013 <http://www.eoearth.org/article/Measurement_system>

## The Author

Martin Vermeer (born 1953 in The Netherlands) is since 2000 Professor of Geodesy at TKK's Surveying Department. Before that he made his career in the Finnish Geodetic Institute, main interests being the study of the Earth's gravity field and precise geodetic GPS, including permanent networks. Since 1994 he is a foreign member of the Finnish Academy of Sciences and Letters. He is and has been internationally active in the International Association of Geodesy, the Nordic Geodetic Commission and ... (Full Bio)