Modeling Buildings in CityGML LOD1: Building Parts, Terrain Intersection Curve, and Address Features

Abstract

3D city models integrate heterogeneous urban data from multiple sources in a unified geospatial representation, combining both semantics and geometry. Although in past decades they have predominantly been used for visualization, today they are used in a large range of tasks related to exploration, analysis, and management across multiple domains. The complexity of urban processes and the diversity of urban environments bring challenges to the implementation of 3D city models. To address such challenges, this paper presents the development process of a 3D city model of a single neighborhood in the city of Sofia based on the CityGML 2.0 standard. The model represents the buildings in LOD1, focusing on CityGML features, including building parts, the terrain intersection curve, and the address. Similar building models of 18 cities provided as open datasets are explored and compared to extract good modeling practices. As a result, workflows for the generation of 3D building models in LOD1 are elaborated on and improvements in the feature modeling are proposed. Two building model options are examined: (1) the modeling of a building as a single solid with differentiated rooftops and (2) the modeling of a building with separate building parts. The developed 3D building model contains 471 buildings and 198 addresses in both cases of building parts modeling. In addition, the terrain intersection curve (TIC) is modeled and a method for removing the duplicating TIC features is applied. Consequently, the overall count of vertices of the TIC is lowered from 12,112 to 8042. Finally, the possibilities for visualization of the model in popular platforms such as ArcGIS Pro and Cesium Ion are explored.