The glare rating in outdoor projects has been extended in the Calculation manager.
Under Artificial light and the Glare rating tab, new GR and TI glare ratings can be calculated for observers.
The following description explicitly covers the verification required by the German Railway (DB) for overground platforms.
Calculation manager dialog
What is calculated?
The direct light from each individual luminaire is calculated at each observer point.
This value, set out as a ratio to the surrounding luminance, gives the GR or TI value.
The surrounding luminance value is obtained as a function of the defined measurement area, referred to as the reference value.
Although this is an approximation, CIE 112 stipulates that it is a permitted approximation.
GR values stand for stationary observer points and TI values for travelling or moving observer points.
Measuring area and observers
To calculate the GR value and the TI values, the program requires a Reference area for establishing the surrounding luminances.
The Reference area must be allocated a mean Reflectance of the real area that is positioned underneath it.
The program looks for this reflectance automatically.
This procedure, as described, makes it possible to establish the GR / TI for any desired scenes and at different levels.
Note: Try to avoid dissimilar reflections beneath reference surfaces if possible.
If the reflectance of these real surfaces (e.g. the floor) changes, it may be necessary to adjust the reflectance of the reference surface.
Measurement or reference area
In the screenshot above, the observer points arranged like a table represent the waiting passengers next to the railway lines.
The observer points arranged in a row represent the driver of the train that is arriving.
The position and size of the reference area ought always to be selected to suit the requirements (sports ground, station platform...).
In the picture above you can see the reference area shown in red.
Care was taken to ensure that this is lined up in parallel beneath a repeated pattern of positioned luminaires.
The program positions a group of 5x5 observers uniformly in front of the reference area for calculating the GR values.
The observer points for the vehicle driver are positioned in parallel to the reference surface.
The first observer point is at an angle of 20° prior to the first luminaire above the reference surface.
In the transverse direction, it is placed 1.66m alongside the left edge of the measurement field (platform edge).
The number of steps and the distance between them is governed by the length of the measuring surface and the number of measuring points set.
The basic parameters are set in accordance with the German Railway (DB) Guidelines. All the parameters can be adjusted as required.
Note: The observer points are not updated automatically. If the observers have to be realigned due to changes in the luminaire positions or the alignment
of the measurement surface, you must trigger the automatic positioning of the observer points manually. To do this, go to the Calculation Manager
and start DB Guidelines again.
Please note that when GR and TI values are determined for outdoors, all the light reflections are calculated as in the past, but, according to the method
proposed in CIE 112 for determining the mean background luminance, only the reference surface is taken into account. A bright white wall directly in the
observer’s field of vision thus only has an indirect influence on the mean background luminance. As a result, the calculated GR and TI values tend to be
too high (see CIE112). On the other hand, it is not necessary to recreate every 3D detail in outdoor projects.
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|Asked: 9/13/19, 9:23 AM|
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|Last updated: 1/20/20, 12:26 PM|