Abstract: A method of obtaining information about radiation arising from within an environment includes providing a directionally sensitive radiation detector which has a field of view and providing a visual image capturing device which has an area of vision. The radiation for a field of view is measured, the field of view including a part of the environment. The measurement of radiation is recorded together with an indication of the space or position of the respective field of view relative to the detector. A visual image of an area of vision is obtained, the area of vision including the part of the environment within the field of view. The image is recorded together with an indication of the spatial position of that field of view relative to the detector. Selecting the set of data from the measurement of radiation according to a criteria set after completion of the measurements of radiation. The information is overlaid from one or more of the measurements of radiation with one of the visual images.