Applications of thermal fisheye imagery in urban canyons

The sky-view factor is a commonly used parameter in urban climatology; but to date, no completely satisfactory technique has yet been developed for its calculation. This letter investigates the potential of a prototype thermal fisheye camera, originally developed for use in the CLOUDMAP2 project, to produce fisheye imagery suitable for sky-view factor analysis. The camera distinguishes between the fraction of cold-space background and warm obstructions (e.g., buildings, trees, and cloud) from which the sky-view factor can be calculated. Early results are promising with excellent segmentation results obtained under clear skies, although the techniques are currently less reliable when clouds are visible in the field of view. However, this is demonstrated to be an advantage as the camera can also be used to simultaneously measure other parameters such as solar-tracks and "local" cloud fractions. The preliminary results indicate potential for the use of the camera for modeling studies in urban environments.