There is an ongoing debate about including Angle as a dimension of its own, see for instance

• On the dimension of angles and their units , Peter J Mohr et all, in Metrologia
• Angles are inherently neither length ratios nor dimensionless, Paul Quincey et all, in Metrologia

This module adds an Angle dimension to the SI system. To use dimensionless angles, see Data.Units.SI.