Airy Points are used for precision measurement (metrology) to support a length standard in such a way as to minimise bending or droop. The points are symmetrically arranged around the centre of the length standard and are separated by a distance equal to
or about approximately 5/9ths of the total length of the measuring device.

Airy points are normally identified by inscribed marks or lines. For example, a 450 mm length gauge would have an Airy point separation of 450 mm times 5/9 = 250 mm. A line or pair of lines would be marked onto the gauge 100 mm in from each end. Supporting the artifact at these points ensures that the calibrated length is preserved. If the length gauge is not supported at the Airy points, the measurement uncertainty

Measurement uncertainty

In metrology, measurement uncertainty is a non-negative parameter characterizing the dispersion of the values attributed to a measured quantity. The uncertainty has a probabilistic basis and reflects incomplete knowledge of the quantity. All measurements are subject to uncertainty and a measured...

 is increased.

See also

• George Biddell Airy
  George Biddell Airy
  Sir George Biddell Airy PRS KCB was an English mathematician and astronomer, Astronomer Royal from 1835 to 1881...
  
  
• History of measurement
  History of measurement
  Units of measurement were among the earliest tools invented by humans. Primitive societies needed rudimentary measures for numerous tasks such as: constructing dwellings of an appropriate size and shape, fashioning clothing, or bartering food or raw materials....
  
  
• International Prototype Meter
  International Prototype Meter
  The metre was originally defined as one ten-millionth of the distance between the North Pole and the equator at the longitude of Paris. Because of the difficulty of reproducing this measurement, a platinum bar nominally of that length was constructed in 1799 and housed in the Archives de la...
  
  
• Test method
  Test method
  A test method is a definitive procedure that produces a test result.A test can be considered as technical operation that consists of determination of one or more characteristics of a given product, process or service according to a specified procedure. Often a test is part of an experiment.The test...
  
  
• Units of measurement
  Units of measurement
  A unit of measurement is a definite magnitude of a physical quantity, defined and adopted by convention and/or by law, that is used as a standard for measurement of the same physical quantity. Any other value of the physical quantity can be expressed as a simple multiple of the unit of...
  
  
• Uncertainty
  Uncertainty
  Uncertainty is a term used in subtly different ways in a number of fields, including physics, philosophy, statistics, economics, finance, insurance, psychology, sociology, engineering, and information science...
  
   in measurement
• Weights and measures