ANSI/IES LM-72-20

Approved Method: Directional Positioning of Photometric Data

It is important to note that this document assigns specific, standard meaning to certain words; thus, some users might need to adjust their vocabulary. Most should find a positioning system compatible with their normal patterns and experience. This document does not show a preference for any system, but rather describes each of the three systems and then explains how to convert between them. In applying CN or CCE, four types of angular “rotation” are defined (Orient, Tilt, Roll, and Spin), and each shall be preformed in the defined order. Any or all of the rotation angles may be zero. Each subsequent rotation is applied to the axis system as previously rotated (the local axes), not the original axis system (the global axes). Orientation, Tilt, Roll, and Spin can be described using X, Y, and Z axes, but the CN system and CCE system are described separately, and separate drawings of the coordinate system are needed.