Abstract
This paper proposes two analytical methods to evaluate urban nightscape from a given viewpoint. The first method measures the solid angle of the urban area to capture the size of the nightscape. The second one computes the ratio of visible roads to total road length to understand the intensity of the linear elements (e.g. streetlamps). Based on these two methods, we analyzed a hill-top view of the urban nightscape in Hakodate from 1975 to 2000 at five-yearly intervals. We show that the top of Hakodate-Yama was the good location in terms of maximizing the solid angle. Second we demonstrate that urban growth produces more Urayakai spots. Finally we also show that disaster prevention policies contribute greatly to road visibility.
