Building 3D CityGML Model and Digital Management of a Vernacular Architecture

The aim of the paper is to discuss the Levels Of Details (LODs) of 3D city models in order to assess the constructive and semantic characteristics that distinguish each of them. The standard approach used in order to build the 3D model is the CityGML 3.0 Conceptual Model. A key role for the development of the CityGML Conceptual Model is to provide a common definition of the basic entities, attributes, and relations of a semantically rich 3D city model. This approach is important with respect to the cost-effective sustainable maintenance of 3D city models, allowing the reuse of the same data in different application fields. In this context, we have developed a method to build a 3D CityGML model using SketchUP software and some of the tools implemented in it. In addition, the constructed model was displayed and validated by using an open source software (FZK viewer). The building taken into consideration is a vernacular dwelling structure called “trullo” (plural “trulli”) and present in the Apulia region, Italy. “Trulli” are extraordinary examples of dry stone construction with conical or pyramidshaped roof made with slabs, a technique dating back to prehistoric times and still in use today in Apulia. Before building the 3D model, it was necessary to perform the 3D survey of the building; this task was carried out by using Terrestrial Laser Scanner (TLS) that allowed a realistic and detailed reconstruction of the structures. From the point cloud, a special procedure was developed in order to build CityGML models in several LODs.