Quantification of twilight landscapes

－Focusing on the regional revitalization of the Western Tenpoku region－

Abstract

The appearance of Sunset and Twilight in your daily life differ depending on the area and urban structure. For example, in high latitude areas, the solar altitude is low, and in a city of grid pattern, there are rules in the direction in which the Twilight sky can be seen. Therefore, the paper assesses the importance that the duration of Twilight can be speculated if we know geographical conditions such as latitude and season, and urban conditions such as the direction of the road. Therefore, the main result of this work is that we built a theoretical model to speculate the duration of Twilight and apply the theoretical model to the Western Tenpoku Region located on the northernmost part of Hokkaido. The result showed that the duration of Twilight is longer and the Twilight azimuth is wider in the high latitude areas. The other result of this work showed that the Western Tenpoku Region, which has grid pattern roads and various angles, is a rare region where you can enjoy the scenery of Twilight all year round.