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Mapping a light source, any light source, is of broad interest to accident reconstructionists, human factors professionals and lighting experts. Such mappings are useful for a variety of purposes, including determining the effectiveness and appropriateness of lighting installations, and performing visibility analyses for accident case studies. Currently, mapping a light source can be achieved with several different methods. One such method is to use an illuminance meter and physically measure each point of interest on the roadway. Another method utilizes a goniometer to measure the luminous intensity distribution, this is a near-field measurement. Both methods require significant time and the goniometric method requires extensive equipment in a lab. A third method measures illumination distribution in the far-field using a colorimeter or photometer.

Retroreflection occurs when a light ray incident on a surface is reflected back towards the light source. The performance of a retroreflective material is of interest to accident reconstructionist, human factors professionals, lighting professionals, and roadway design professionals. The retroreflective effect of a material can be defined by the coefficient of retroreflection, which is a function of the light’s entrance angle and the viewer’s observation angle. The coefficient of retroreflection of a material is typically measured in a laboratory environment or in the field with a retroreflectometer. Often the material in question cannot be taken to a laboratory for testing and commercially available portable retroreflectometers are limited to entrance angles of 45 degrees or less and may be cost prohibitive in some cases.