Calculations and Measurements

Abstract

The lighting designer has to perform lighting calculations in order to arrive at solutions that will satisfy the relevant lighting requirements. Universally-applicable computer programs are available for this purpose. The basic formulas have been described in previous Chapters of this book. In this Chapter the conventions for the number and position of calculation points and the position of the observer will be discussed. Different Standards and Recommendations, such as those of CIE and of the European and American Standards, apply different conventions. It is extremely important that specifications for road-lighting installations clearly specify which convention method has to be followed.

The measurements carried out in connection with road lighting fall into four categories: those to determine the lamp properties, the luminaire properties, the reflection properties of road surfaces and, finally the installation properties. The first three categories mostly concern laboratory measurements. Sometimes road-lighting engineers want to check the spectral lamp properties, especially the S/P ratio of the light source, in the field. The same holds true for the reflection properties of road surfaces where both laboratory measurements from samples and in-situ measurements on the real road with reflectometers can be carried out. Field measurements made on road lighting installations are carried out on new installations to check whether they fulfill the quality specifications, and on installations already longer in use, to reveal whether there is need for maintenance, modification, or perhaps replacement. The principles of both laboratory and field measurements will be discussed here.