Design and development of silhouette analysis module for three dimensional city models

3D city models are digital representations of objects such as terrain surfaces, sites, buildings, vegetation, infrastructure and landscape elements belonging to urban areas. 3D city models are used in presentation, exploration, analysis, and management tasks for a large number of different applications including urban planning, disaster management, facility management, logistics, security, telecommunication, location-based services, real estate portals as well as being used for computer games and educational purposes. Silhouette analysis, one of 3D spatial analyses, is important for urban area designing and landscape planning. Silhouette analysis is used to protect the silhouette of important buildings that have become landmark especially in urban areas. ArcGIS is one of the most popular software in Geographical Information Systems (GIS) market. It has "3D Analyst Tools" providing functions enabling many analyses including construct sight lines, intervisibility, line of sight, observer points, sun shadow volume, viewshed, visibility, skyline, skyline barrier and skyline graph. However, the 3D Analyst Tools does not have a function to create a silhouette view of buildings. In this study, a silhouette analysis module was developed using the Python programming language for the ArcGIS software and a toolbar was designed to use this module. Silhouette analysis module can produce a silhouette view of buildings in a certain field of view from the observation point and can track changes on silhouette when new buildings planned to be built in the same area. In addition, the use of the new silhouette analysis module can determine whether a newly built building has distorted the urban silhouette and calculates the maximum height and floor number of new buildings. Thus, important contribution was provided in solving the distortion problems of urban silhouette encountered in the urban planning process and in the implementation of the development plans.