抄録
Viewshed analysis based on digital elevation model is one of the most common operation in GIS. The viewshed or visible area is naturally defined using a sightline between a observation point and a target point, but its calculation is computationally intensive. In this paper, formal definitions on visibility are provided by using sightplane as well as sightline, and their equivalence is proved. To form the sightplane as a covering plane, three points including the observation point are selected. As these point can be selected in distance base order, redundant check of invisibility becomes evitable. On this basis, an efficient and simple algorithm is proposed and demonstrated for its superiority to the sightline algorithm.
