Editing Traceability (section)

==Measurement==
The term ''measurement traceability'' or ''metrological traceability'' is used to refer to an unbroken chain of comparisons relating an [[Measuring instrument|instrument]]'s [[measurement]]s to a known [[Standard (metrology)|standard]]. [[Calibration]] to a traceable standard can be used to determine an instrument's bias, [[Accuracy and precision|precision]], and [[accuracy]]. It may also be used to show a [[chain of custody]]—from current interpretation of evidence to the actual evidence in a legal context, or history of handling of any information.

In many countries, national standards for weights and measures are maintained by a National Metrological Institute (NMI) which provides the highest level of standards for the [[calibration]] / measurement traceability infrastructure in that country. Examples of government agencies include the [[National Physical Laboratory, UK]] (NPL) the [[National Institute of Standards and Technology]] (NIST) in the USA, the [[Physikalisch-Technische Bundesanstalt]] (PTB) in Germany, the Instituto Nazionale di Ricerca Metrologica (INRiM) in Italy, and the [[National Research Council of Canada]] (NRC). As defined by NIST, "Traceability of measurement requires the establishment of an unbroken chain of comparisons to stated references each with a stated uncertainty."

A clock providing '''{{visible anchor|traceable time}}''' is traceable to a time standard such as [[Coordinated Universal Time]] or [[International Atomic Time]]. The [[Global Positioning System]] is a source of traceable time.