IES LM-72-20 PDF Download

The IES LM-72-20 standard aims to establish a standardized set of terms for the angular positioning of photometric data. This document is primarily intended for lighting software providers and users to ensure consistent and unambiguous specifications for rotating photometric data.

The standard identifies two common positioning systems that have been in use for many years - the "Clockwise from North" (CN) system and the "Counter-Clockwise from East" (CCE) system. The CN system involves rotating the luminaire photometric data in a clockwise direction from the northern direction, while the CCE system rotates the data counterclockwise from the eastern direction. These two positioning methods are fundamentally different and cannot be reconciled.

Additionally, the standard discusses another positioning method called "aiming luminaire at a point." This method has also been in use for years and is further elaborated on within the document.