Community Research and Development Information Service - CORDIS


The determination of the refractivity of air is of great importance for a number of measurement tasks. It is of particular concern when length is precisely determined in the free atmosphere using interferometry. In order to maintain the highest accuracy in interferometric length measurement it is essential to determine a value for the refractivity of the ambient air. The refractivity of air may be determined by calculation in an equation or by direct measurement. The calculated refractivity may be inaccurate due to errors in any of the atmospheric measurements required for the equation or changes in the composition of the air. The extent and causes of refractivity differences have been assessed using a refractometer instrumentation package in industrial environments where interferometers are used to calibrate a wide variety of engineering artefacts. In addition, measurement sensors used in industrial environments to determine air refractivity have been compared and an error analysis undertaken.

Additional information

Authors: BIRCH K P, NPL, Teddington (GB);WARD R E, NPL, Teddington (GB);WILKENING G, Physikalisch-Technische Bundesanstalt, Braunschweig (DE);REINBOTH F, Physikalisch-Technische Bundesanstalt, Braunschweig (DE)
Bibliographic Reference: EUR 14103 EN (1992) 59 pp., MF, ECU 4, blow-up copy ECU 9
Availability: (2)
Record Number: 199210596 / Last updated on: 1994-12-02
Original language: en
Available languages: en