Metrology in the context of Gamma-ray source

The foot (standard symbol: ft) is a unit of length in the British imperial and United States customary systems of measurement. The prime symbol, ′, is commonly used to represent the foot. In both customary and imperial units, one foot comprises 12 inches, and one yard comprises three feet. Since an international agreement in 1959, the foot is defined as equal to exactly 0.3048 meters. The most common plural of foot is feet. However, the singular form may be used like a plural when it is preceded by a number, as in "that man is six foot tall".

Historically, the "foot" was a part of many local systems of units, including the Greek, Roman, Chinese, French, and English systems. It varied in length from country to country, from city to city, and sometimes from trade to trade. Its length was usually between 250 mm (9.8 in) and 335 mm (13.2 in) and was generally, but not always, subdivided into twelve inches or 16 digits.

Measurement is the quantification of attributes of an object or event, which can be used to compare with other objects or events. In other words, measurement is a process of determining how large or small a physical quantity is as compared to a basic reference quantity of the same kind.The scope and application of measurement are dependent on the context and discipline. In natural sciences and engineering, measurements do not apply to nominal properties of objects or events, which is consistent with the guidelines of the International Vocabulary of Metrology (VIM) published by the International Bureau of Weights and Measures (BIPM). However, in other fields such as statistics as well as the social and behavioural sciences, measurements can have multiple levels, which would include nominal, ordinal, interval and ratio scales.

Measurement is a cornerstone of trade, science, technology and quantitative research in many disciplines. Historically, many measurement systems existed for the varied fields of human existence to facilitate comparisons in these fields. Often these were achieved by local agreements between trading partners or collaborators. Since the 18th century, developments progressed towards unifying, widely accepted standards that resulted in the modern International System of Units (SI). This system reduces all physical measurements to a mathematical combination of seven base units. The science of measurement is pursued in the field of metrology.

Uncertainty or incertitude refers to situations involving imperfect or unknown information. It applies to predictions of future events, to physical measurements that are already made, or to the unknown, and is particularly relevant for decision-making. Uncertainty arises in partially observable or stochastic or complex or dynamic environments, as well as due to ignorance, indolence, or both. It arises in any number of fields, including insurance, philosophy, physics, statistics, economics, entrepreneurship, finance, medicine, psychology, sociology, engineering, metrology, meteorology, ecology and information science.

Surveying or land surveying is the technique, profession, art, and science of determining the terrestrial positions of points based on the distances and angles between them. These points are usually on the surface of the Earth, and they are often used to establish maps and boundaries for ownership, locations, such as the designated positions of structural components for construction or the surface location of subsurface features, or other purposes required by government or civil law, such as property sales.

A professional in land surveying is called a land surveyor.Surveyors work with elements of geodesy, geometry, trigonometry, regression analysis, physics, engineering, metrology, programming languages, and the law. They use equipment, such as total stations, robotic total stations, theodolites, GNSS receivers, retroreflectors, 3D scanners, lidar sensors, radios, inclinometer, handheld tablets, optical and digital levels, subsurface locators, drones, GIS, and surveying software.

Interferometry is a technique which uses the interference of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber optics, engineering metrology, optical metrology, oceanography, seismology, spectroscopy (and its applications to chemistry), quantum mechanics, nuclear and particle physics, plasma physics, biomolecular interactions, surface profiling, microfluidics, mechanical stress/strain measurement, velocimetry, optometry, and making holograms.

Interferometers are devices that extract information from interference. They are widely used in science and industry for the measurement of microscopic displacements, refractive index changes and surface irregularities. In the case with most interferometers, light from a single source is split into two beams that travel in different optical paths, which are then combined again to produce interference; two incoherent sources can also be made to interfere under some circumstances. The resulting interference fringes give information about the difference in optical path lengths. In analytical science, interferometers are used to measure lengths and the shape of optical components with nanometer precision; they are the highest-precision length measuring instruments in existence. In Fourier transform spectroscopy they are used to analyze light containing features of absorption or emission associated with a substance or mixture. An astronomical interferometer consists of two or more separate telescopes that combine their signals, offering a resolution equivalent to that of a telescope of diameter equal to the largest separation between its individual elements.

The kilogram (also spelled kilogramme) is the base unit of mass in the International System of Units (SI), equal to one thousand grams. It has the unit symbol kg. The word "kilogram" is formed from the combination of the metric prefix kilo- (meaning one thousand) and gram; it is commonly shortened to "kilo" (plural "kilos").

The kilogram is an SI base unit, defined ultimately in terms of three defining constants of the SI, namely a specific transition frequency of the caesium-133 atom, the speed of light, and the Planck constant. A properly equipped metrology laboratory can calibrate a mass measurement instrument such as a Kibble balance as a primary standard for the kilogram mass.

Scale of temperature is a methodology of calibrating the physical quantity temperature in metrology. Empirical scales measure temperature in relation to convenient and stable parameters or reference points, such as the freezing and boiling point of water. Absolute temperature is based on thermodynamic principles: using the lowest possible temperature as the zero point, and selecting a convenient incremental unit.

Celsius, Kelvin, and Fahrenheit are common temperature scales. Other scales used throughout history include Rankine, Rømer, Newton, Delisle, Réaumur, Gas mark, Leiden, and Wedgwood.

In arithmetic, a quotient (from Latin: quotiens 'how many times', pronounced /ˈkwoʊʃənt/) is a quantity produced by the division of two numbers. The quotient has widespread use throughout mathematics. It has two definitions: either the integer part of a division (in the case of Euclidean division) or a fraction or ratio (in the case of a general division). For example, when dividing 20 (the dividend) by 3 (the divisor), the quotient is 6 (with a remainder of 2) in the first sense and ${\displaystyle 6+{\tfrac {2}{3}}=6.66...}$ (a repeating decimal) in the second sense.

In metrology (International System of Quantities and the International System of Units), "quotient" refers to the general case with respect to the units of measurement of physical quantities. Ratios is the special case for dimensionless quotients of two quantities of the same kind.Quotients with a non-trivial dimension and compound units, especially when the divisor is a duration (e.g., "per second"), are known as rates.For example, density (mass divided by volume, in units of kg/m) is said to be a "quotient", whereas mass fraction (mass divided by mass, in kg/kg or in percent) is a "ratio". Specific quantities are intensive quantities resulting from the quotient of a physical quantity by mass, volume, or other measures of the system "size".

In measurement technology and metrology, calibration is the comparison of measurement values delivered by a device under test with those of a calibration standard of known accuracy. Such a standard could be another measurement device of known accuracy, a device generating the quantity to be measured such as a voltage, a sound tone, or a physical artifact, such as a meter ruler.

The outcome of the comparison can result in one of the following:

The International Bureau of Weights and Measures (French: Bureau international des poids et mesures, BIPM) is an intergovernmental organisation, through which its 64 member-states act on measurement standards in areas including chemistry, ionising radiation, physical metrology, as well as the International System of Units (SI) and Coordinated Universal Time (UTC). It is headquartered in the Pavillon de Breteuil in Saint-Cloud, near Paris, France. The organisation has been referred to as IBWM (from its name in English) in older literature.

The United States Coast and Geodetic Survey (abbreviated USC&GS; known as the Survey of the Coast from 1807 to 1836, and as the United States Coast Survey from 1836 until 1878) was the first scientific agency of the United States government. It existed from 1807 to 1970, and throughout its history was responsible for mapping and charting the coast of the United States, and later the coasts of U.S. territories. In 1871, it gained the additional responsibility of surveying the interior of the United States and geodesy became a more important part of its work, leading to it being renamed the U.S. Coast and Geodetic Survey in 1878.

Long the U.S. government's only scientific agency, the Survey accumulated other scientific and technical responsibilities as well, including astronomy, cartography, metrology, meteorology, geology, geophysics, hydrography, navigation, oceanography, exploration, pilotage, tides, and topography. It also was responsible for the standardization of weights and measures throughout the United States from 1836 to 1901. In 1959, it was assigned the responsibility for U.S. government oceanographic studies worldwide.

The National Physical Laboratory (NPL) is the national measurement standards laboratory of the United Kingdom. It sets and maintains physical standards for British industry.

Founded in 1900, the NPL is one of the oldest metrology institutes in the world. Research and development work at the laboratory has contributed to the advancement of many disciplines of science, including the development of early computers in the late 1940s and 1950s, construction of the first accurate atomic clock in 1955, and the invention and first implementation of packet switching in the 1960s, which is today one of the fundamental technologies of the Internet. The former heads of NPL include many individuals who were pillars of the British scientific establishment.

The SI base units are the standard units of measurement defined by the International System of Units (SI) for the seven base quantities of what is now known as the International System of Quantities: they are notably a basic set from which all other SI units can be derived. The units and their physical quantities are the second for time, the metre (sometimes spelled meter) for length or distance, the kilogram for mass, the ampere for electric current, the kelvin for thermodynamic temperature, the mole for amount of substance, and the candela for luminous intensity. The SI base units are a fundamental part of modern metrology, and thus part of the foundation of modern science and technology.

The SI base units form a set of mutually independent dimensions as required by dimensional analysis commonly employed in science and technology.