UGR method - Unified Glare Rating
Modified on: Fri, 27 May, 2022 at 11:48 AM
What is the UGR method in DIALux?
The UGR value is a measure of glare. The greater the value, the more glare the light source causes. The UGR observer is at a height of 1.2 metres as standard. Its viewing direction is in DIALux (cos(α), sin(α), 0), where α is the angle to the x-axis.
UGR values are calculated in DIALux using the following formula (see CIE 117).
Luminance [cd / m2]
Distance of the luminaire to the observer [m]
Luminous intensity [cd]
projected area of the luminous parts [m2]
Solid angle of the luminous parts [sr]
Ap / r2
Position index of the LEO
indirect illuminance at the observer's eye [lux]
Background luminance [cd / m2]
Eind / π
Number of LEOs in the scene
The position index is determined as follows:
First, the R, T and H coordinates of the luminaires are determined with respect to the observer. Then the position index is calculated from the table by means of interpolation. Luminaires with a position index outside the validity range of the table are not considered in the UGR calculation. This is the case, for example, in H/R > 2.
What are UGR tables?
With UGR tables, rooms of the dimensions (2H, 2H),...(12H, 8H) are equipped with luminaire fields. H is always 2m for UGR tables. The distance between the luminaires is determined by the "Space To Height Ratio" (SHR). Permissible values are 0.25 and 1, so with SHR = 1 the luminaire spacing is 2m, with SHR = 0.25 it is 0.5m. The observer is always in the middle of the wall at a height of 1.2m (see sketches). Furthermore, there is the arrangement viewing direction transverse to the lamp axis and viewing direction longitudinal to the lamp axis.
Please have also a look at the following article on our DIAL website: No glare from artificial light. What is behind the UGR method?
and the tutorial about UGR calculation on our YouTube channel: UGR calculation in evo
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