Traceability enhancement in angle measurements

Traceability of angle measurements is based mainly on the standard of the plane angle - prism (polygon) calibrated at appropriate accuracy. Nevertheless, the standard (etalon) of flat angle - polygon has many restrictions for the transfer of angle unit - radian (rad) and other units of angle. It depends on number of angles formed by the flat sides of the polygon. Here is proposed a possibility to create the standard of the plane angle equal to π rad using the circular scale with the rotation axis of very high accuracy and two opposite placed precision reading instruments with appropriate alignment. Proposed method permits an implementation of π rad as primary standard angle and enables to assure a traceability of flat angle measurements at laboratory environment. Short information about the multipurpose angle measurement test bench developed is presented.