EXTENDING CITYGML 3.0 TO SUPPORT 3D UNDERGROUND LAND ADMINISTRATION

Abstract. Rapid development of underground space necessitates the efficient management of underground areas. Data modelling plays an underpinning role in integrating and managing underground physical and legal data. The physical data refers to semantic and spatial data of underground assets such as utilities, tunnels, and basements, while the legal data comprises the ownership information and the extent of underground legal spaces and the semantic and spatial relationships between legal spaces. Current Underground Land Administration (ULA) practices mainly focus on representing only either legal spaces or the physical reality of subsurface objects using fragmented and isolated 2D drawings, leading to ineffective ULA. A complete and accurate 3D representation of underground legal spaces integrated with the 3D model of their physical counterparts can support different use cases of ULA beyond underground land registration, such as planning, design and construction of underground assets (e.g. tunnels and train stations), utility management and excavation. CityGML is a prominent semantic data model to represent 3D urban objects at a city scale, making it a good choice for underground because underground assets such as tunnels and utilities are often modelled at city scales. However, CityGML, in its current version, does not support legal information. This research aims to develop an Application Domain Extension (ADE) for CityGML to support 3D ULA based on the requirements defined in the Victorian state of Australia. These requirements include primary underground parcels and secondary underground interests. This work extends CityGML 3.0, which is the new version of this model. In CityGML 3.0, UML conceptual models as platform-independent models are suggested to express ADEs. Thus, the ADE proposed in this study will be based on UML. The findings of this study show that extending CityGML to support legal information can be a viable solution to meet the requirements of a 3D integrated model for ULA. The CityGML ADE proposed in this study can potentially provide a new solution for 3D digital management of underground ownership rights in Victoria, and it can be used to implement an integrated 3D digital data environment for ULA.