CIPM MRA COMPARISON REPORTS
CCL-K3.n01
Angle standards : optical polygon
Published on 20/02/2026 - © 2026 B.J. Eves et al
Citation B.J. Eves et al 2026 CIPM MRA Comparison reports
Authors
https://orcid.org/0000-0003-2481-0334 Wang Shihua National Metrology Centre, Agency for Science, Technology and Research (NMC, A*STAR) Singapore 
M del Mar Perez Hernandez Centro Español de Metrología (CEM) Spain
Francisco Huerta Yshikawa Centro Nacional de Metrologia (CENAM) Mexico
Luiz Henrique Brum Vieira Instituto Nacional de Metrologia, Qualidade e Tecnologia (INMETRO) Brazil
Milena Astrua Istituto Nazionale di Ricerca Metrologica (INRIM) Italy
Yae Yong Lee Korea Research Institute of Standards and Science (KRISS) Korea, Republic of
Zi Xue National Institute of Metrology (NIM) China
Tsukasa Watanabe National Metrology Institute of Japan (NMIJ AIST) Japan
Tanfer Yandayan TÜBITAK Ulusal Metroloji Enstitüsü (UME) Türkiye
Abstract
At its meeting in 2014, the Consultative Committee for Length (CCL) WG-MRA decided upon a key comparison on the measurement of angle standards. Initially the comparison was to include both optical polygons and angle encoders, however, the comparison was eventually scaled back to only include optical polygons. The comparison was also delayed due to a change in pilot laboratory, and artifact circulation was started in April 2023 and completed in September 2025. Two optical polygons by different manufacturers were circulated: a 12-sided polygon similar to one used in the EURAMET.L-K3.n01 comparison, and a 10-sided polygon similar to the polygon used in the SIM.L-K3-2019 comparison. Unfortunately, the 12-sided polygon was not stable for the duration of the comparison and an additional artifact stability term was added in quadrature to the participants 12-sided polygon reported uncertainties. The vast majority of participants successfully supported their uncertainty claims.