The Metrology Working Group for Length in SIM, MWG 4, supports SIM and its member NMIs/DIs in meeting the obligations under the CIPM MRA in the field of length. The MWG4 develops the discussion of technical issues related to length metrology. The technical areas are important to support industry and researchers.

MWG4 focuses on

  • Realization of the SI units of length.
  • Radiations of the Mise en Pratique: Laser Radiations, Lamp Radiations.
  • Linear Dimensions: Length Instruments, End Standards, Line Standards, Diameter Standards, Standards of 1D Dimensions.
  • Angle: Angle by Circle Dividers, Small-Angle Generators, 3.2.1 sine (bar, table) cylinder spacing; angle 3.3 Angle Instruments, Angle Artifacts, Angle Prisms.
  • Form: Flatness Standards, Roundness Standards, Straightness Standards, Cylindricity Standards, Optical Standards.
  • Complex geometry: Surface Texture Standards, Screw Standards, Gear Standards, CMM Artifacts, 2-D and 3-D Instruments, Hardness.
  • Various Dimensional: Hand Instruments, Pressure Artifacts, Long Distance, Reference Materials, Layer thickness, Index of Refraction.


Parts of the activities carried out in the group are;

  • Organize regional key and supplementary comparisons as well as pilot studies in the field of length, and links these SIM activities to the Consultative Committee for length (CCL) of the CIPM and to its counterparts in other Regional Metrology Organizations (RMOs).
  • Facilitates cooperation in preparing, publishing and maintaining calibration and
  • measurement capability claims (CMCs) of member economies and of American
  • laboratories new to international metrology.
  • Facilitates technical cooperation among its members and guests through meetings,
  • workshops and training opportunities at various NMIs/DIs.
  • Seeks harmonization among its members through sustainable networking.
  • Welcomes cooperation with other communities to promote and to share advanced technology.


Lic. Karina Bastida, INTI, Argentina

[email protected]


  • Contacts [should hyperlink to SIM]


IADB SIM Research Engagement Opportunity (ongoing projects):

  • Improvement and updating of interferometric systems for traceable dimensional nanometrology at SIM.
  • Large-scale dimensional metrology.
  • Calibration of standard reference material for use in calibrating the magnification or scale of optical microscopy and scanning electron microscopy.

Events & Meetings

  • MWG4 Meeting, Gramado, Brasil, 2014
  • Dimensional Metrology Hands-on Workshop, and Dimensional metrology for advanced manufacturing technologies conferences, NIST, Gaithersburg, EEUU, 2016.
  • MWG4 Meeting, NIST, Gaithersburg, EEUU, 2016.
  • Workshop, on CMCs and comparison and conference on emerging technologies presentation, INTI, Buenos Aires, Argentina, 2018.
  • MWG4 Meeting, INTI, Buenos Aires, Argentina, 2018.



International metrology in the field of Length

Recommended values of standard frequencies

List of Key Comparison Database (KCDB) for Length (Appendix B)  

CCL Key comparison portfolio

International Measurement Comparisons for Laser Frequency

International Measurement Comparisons for Dimensional Metrology

Calibration and Measurement Capabilities (CMCs; Appendix C) in Length

CMC classification scheme for length services

CCL Publications and Bibliography