Visual impact assessment of urban developments around heritage landmarks using ULVIA method: (The case of Ark-e-Alishah monument in Tabriz)

Urban intensification and erection of high-rise buildings can affect the visibility of urban landmarks and pedestrians' viewshed toward important monuments. Current 2D and 3D Isovist techniques use static rather than dynamic and cumulative view sheds to analyze visibility. The purpose of this research is to develop a method called ULVIA(1) to assess the average visibility degree of urban landmarks in urban design process. Several factors such as observer and environmental characteristics as well as the concept of cumulative viewshed (using Nurbs data and ray casting in Grasshopper) have been considered to develop this method. Ark-e-Alishah Mosque in Tabriz was selected as a case study and three alternative 3D urban models were reproduced based on data and aerial photos of the monument and its urban context in 2003, 2020 and a proposed model. The ULVIA is executed in sequential steps. The findings reveal that the 2003 urban fabric creates visibility with normal intensity and distribution in all paths, the 2020 option does not have this balance, and the difference between riding and pedestrian mode is higher. The final proposed alternative has a higher visibility intensity and better distribution in both pedestrian and rider modes than other alternatives and therefore UlVIA has the potential to be integrated into urban design process to assess various development alternatives to achieve the best results in terms of historical landmarks' visibility from surrounding environments.