Sky view factor measurement by using a spherical camera

Sky view factor (SVF) is a ratio of sky in upper hemisphere and is an important index for many environmental studies. Frequently used method for measuring SVF is taking fisheye image of upper hemisphere by a camera with fisheye lens (Nikon FC-E8 and FC-E9). In this study, we devised the usage of a spherical camera (RICOH Theta 5), which can takes a picture with 360 degrees field of view (FOV), for SVF measurement. Applicability of the spherical camera to the measurement of SVF is tested by comparing with conventional fisheye cameras. The result showed that it can take the same quality of fisheye images as conventional fisheye camera and can be applied to the measurement of SVF. Accuracy and causes of errors are considered and as a conclusion, the spherical camera has enough performance for the replacement of conventional cameras. The algorithm of making fisheye images of different projection methods and of calculating SVF are written as programs in R.