Project Summary

The Angle Metrology project has been granted funding under the European Metrology Research Program (EMRP) with the project number and acronym of SIB58 ANGLES. The project started in September 2013 and will continue for the following 3 years.

You may also reach the information given below from the publishable summary of the project maintained in the EURAMET website :



The aim of the JRP is to ensure the realisation and dissemination of the SI angle unit ‘radian’ according to the demands from different levels - from high level scientific work carried out in synchrotron radiation and FEL centres to industrial applications. This JRP will result in significant progress beyond the state of the art in the following areas:



Angle metrology is a key enabling technology for scientific and industrial areas of high value in which the EU is globally competitive. Many application areas exist, including: the precision form measurement of optical surfaces (e.g., beam-shaping optics in synchrotron radiation beamlines and Free Electron Lasers – FEL – and flatness standards for interferometer calibration); precision engineering, (e.g., the measurement of machine geometries – straightness, flatness, and parallelism); industrial applications (e.g., in automobiles, airplanes, and industrial robots), and a range of scientific applications (e.g., the measurement of the gravitational constant G and the angular stabilisation of x-ray optical components). New angle measuring devices have been developed which pose challenges such as the precise characterization and calibration of autocollimators and angular encoders with lower uncertainties and the development of small angle generators with nrad uncertainty is required for ensuring the traceability.


Need for the project

The need for traceable high precision angle metrology exists in most industrial sectors and high level scientific applications. For instance, most measurement equipment used in geodesy, long distance measurement, and large volume metrology (e.g. laser trackers, theodolites) is fitted with angle measuring devices such as angular encoders; the same holds true for robots and machine tools used in industry. The accuracy of these devices depends on the capabilities of their in-built angle encoders and they are subsequently determining manufacturing accuracy. Increasing demands on manufacturing accuracy from production industry raise the need for improvements in angle encoders and their calibration.

The need for advanced angle metrology is continually increasing at synchrotron radiation beamlines and FEL centres. Due to the stringent demands on the form measurement of highly curved optical surfaces, synchrotron / FEL metrology laboratories worldwide have been developing a new generation of highly accurate angle-based surface profilometers. Currently, the form measurement limits the fabrication of these optical surfaces. Therefore, the development of XUV optics for the next generation of synchrotrons and FEL X-ray light sources necessitates the further improvement of the angle metrology with autocollimators in the profilometer set-up (target for FEL optics: 0.01 arcsec rms / 0.05 µrad rms slope deviation, corresponding to 0.5 nm rms form deviation). This requires further research for improvement of autocollimator performance at small apertures and improvement of the algorithms for the sub-pixel image location on the CCD detector as well as regular in-situ checks of the performance of autocollimators using portable precise small angle generators.

The need for this research extends beyond the metrology community as state of the art demands rise from various applications ranging from industrial applications to high level scientific applications such as basic sciences, mechatronics, mechanical engineering, civil engineering, energy production research, advanced medical research, materials research, automotive and aerospace industries, nuclear research, measurement, and medical device manufacturers. This list stresses the significance of angle metrology as an enabling technology for industrial production.


Expected results and potential impact

This JRP aims to give more weight to stakeholder needs with respect to the improved dissemination of the SI angle unit ‘radian’ which is currently demanded by the most challenging applications at the forefront of angle metrology. Specifically, it aims to enable traceability of the measurand ‘angle’ with lower uncertainty (less than 50 nrad). A range of angle measuring devices, applications, and challenging measuring conditions will be addressed. Therefore, in addition to angle metrology, we expect that progress in this JRP will affect other areas such as form measurement, the measurement of long distances, angle measuring methods for nrad level rotation and tilt control, and industrial production.


Environmental impact: Research carried out at synchrotron & FEL centres impacts broadly on medical, material, and energy sectors, facilitating a better environment and sustainable energy sources.


Financial impact: Around 60 synchrotrons centres worldwide rely on angle metrology for form measurement of precision optics and alignment of the facilities. Angle metrology is an enabling technology for a broad range of measuring and manufacturing equipment in almost all sectors of industry.


Social impact: Sectors using angle metrology are important to the employment and wealth of the EU. Advanced particle beam therapies and beams from synchrotron sources have applications in healthcare provision – 2009 & 2012 Nobel Prizes in chemistry.