GIS-BASED VIEWSHED ANALYSIS ON THE CONSERVATION PLANNING OF HISTORIC TOWNS: THE CASE STUDY OF XINCHANG, SHANGHAI

Abstract. This paper discuss an application of the GIS software to analysis the visual effect from specific observation points in the historic towns. The viewshed tool in GIS platforms, including ArcGIS and QGIS, are applied in order to generate observation points and viewshed maps. Dozens of key nodes are selected in Xinchang Ancient Town, such as the protected buildings, the historic bridges, and the historic street intersections, as the observation points of viewshed analysis. The result of the analysis is to generate the viewshed map from each observation point. Subsequently, the observation points are merged and the result of the viewshed analysis of the whole ancient town is created. Based on the viewshed analysis results, the characteristics of the visual effect in the town with gentle terrain and dense building is discussed. The features of the ancient town remind elements that need attention in conservation planning, and guides the building regulation within and outside the set boarder of the protected area.