Visibility Evaluation of Historical Landmark Building Using Photographic Survey Coupled with Isovist and Viewshed Analysis

Abstract

One of the fundamental indicators for evaluating visual continuity in the preservation of historical landscapes is the visual experience gained through sequential views in urban space. Controlling the valuable visual qualities is essential to maintain the precious sequential view of the historical landscape. The visual perspective of pedestrians and the wayfinding roles of urban landmarks are central issues in the visual experience of historical cities. The evaluation of visibility analysis is performed using the scene-capturing method via photographic survey. This method is combined with 2D isovist and 3D viewshed analysis as a computational approach applied to five historical landmarks in Malang, Indonesia. The scene-capturing methodology examines the sequential view series of each landmark from various approaching paths by extracting the landmark's silhouette and segmenting the visibly distinct areas of the scene. Subsequently, 2D isovist and 3D viewshed analyses investigate the pattern of the visual field spectrum along each route. As a result, the best visibility rate at the closest observation distance is achieved by the Frateran School Building at 9.58%, while the best visibility at the farthest observation distance is observed at the Kayutangan Church Building at 0.97%. The range of observation distances with a significant percentage of visual sightings is from 75m - 100m, with the closest observation distance ranging from 50 - 75 meters. Combining sequential photo mapping and isovist analysis provides a powerful tool for managing and enhancing the visual experience, which can inform decisions on urban planning, architectural design, and historical preservation.