Different approaches of visibility analyses applied on hilly urban environment

The work reported in this paper is a contribution to the search for reliable visibility evaluation method for the urban environment. We examine three analysis models: 1. Point based visibility graph of street network based on Jiang and Claramunt, (2002), 2. Voxel based volumetric visibility analysis (Fisher-Gewirtzman et. al., 2013) and 3. Line Of Sight (LOS) based visibility analysis (Fisher-Gewirtzman and Elber, 2013). We compare between these models to explore their suitability to a hilly urban spatial configurations. We describe the similarities and differences. In this study we carry out a test comparing the value of visibility degree centrality for street network to the assessments of 3D Voxel and LOS visibility analyses. Our results demonstrate that junctions with similar rankings in all three models were located in a fairly flat topography and all the junctions with different rank were located on the border of a sloping topography. Their visibility was influenced by the changing topography. This preliminary study will be followed by more comprehensive research looking at a variety of urban, architectural and topographic conditions. These findings may provide planners and designers with information about factors that affect the visibility of the urban environment and may put forward new ideas to improve the existing measurement tools.