Measuring objects


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Observer TI

Kurt Bieri


In street lighting, the glare rating assumes a predefined viewing angle for the vehicle driver. The percentage TI (threshold increment) determined for this is used as an evaluation parameter for the physiological glare and is limited by the corresponding standards (e.g. EN 13201).

Glare rating with the TI method

To calculate the TI value, it is necessary to have a reference measuring surface in order to take the ambient luminance into account. To add a new TI observer, go to “Insert/Measuring object/TI“.

With your first click on the floor plan or the 3D view you select the observer's position, and with the second click you specify the observer's viewing direction. The observer is placed at a standard

height of 1.5 metres (EN13201 for car drivers) and takes the nearest vertical measuring surface as the reference measuring surface. The new TI observer is inserted underneath this reference

measuring surface in the scene tree.

TI observer beneath the reference measuring surface

The reference measuring surface can be changed at a subsequent point in time by pulling the TI observer node to a new measuring surface in the scene tree with the Drag&Drop function.

The following parameters can be set for the TI observer:

  • Number of steps and step increment of the observer.
  • Masking angle
  • Inclination: shows the inclination of the observer's line of sight, with a negative angle, the observer is looking downward. (Default = -1°)
  • Observer's age: age of the observer in years.
  • Correction factor: this is the factor for adjusting the luminance. (e.g. DB Guidelines 0.1)
  • Rho: reflectance of the ground beneath the observer in percent.

Please note: If the reflectance of the ground is adjusted, this value must also be changed accordingly.
Please note: For more precise information, the corresponding guidelines must be consulted, e.g. EN13201 or the DB guidelines!

If a TI observer is selected, the observer tools appear in the ribbon bar. The observer's field of vision can be checked here with an animation. To do this, you should open the 3D view (F3 key)

and click on the Start button. The different viewing angles will now be shown successively in the 3D view. The speed of the animation can be changed using the controller in the ribbon bar.

If the TI observer is to be positioned according to the DB guidelines, the DB Guidelines button can be clicked.

Observer tools

After calculating the scene, the output for the TI value can be opened via the output tree under "Calculation results/glare rating".

The maximum TI value is also documented on the results overview of the reference measuring surface.