Investigation of CityGML 3.0 for Modelling Temporal Aspects in Underground Land Administration

Rapid urbanisation and limited land availability have led to increased consideration of underground spaces. This increased utilisation of subterranean space has created a rise in its value, highlighting the significance of ownership of underground areas. Afully-integrated digital model that effectively represents underground space ownership is vital for communicating rights, restrictions, and responsibilities (RRRs) in underground spaces. Underground assets are often built and developed vertically at different time slots, resulting in changes to the legal ownership of underground spaces. Therefore, underground RRRs change over time due to factors such as new subdivisions, consolidations, boundary reconstructions, and land acquisitions. Current practices use 2D survey plans and property base maps to manage and communicate underground RRRs, with some textual notations as well as attributes providing temporal information. However, these methods have limitations, and studies have explored the use of 3D models to address these issues, though they often neglect the temporal aspects. Some studies have investigated 4D cadastre (3D cadastre + time) in different jurisdictions, but these studies mainly remain at a conceptual level for above-ground parcels and buildings. CityGML 3.0 is a data model that provides 3D geometries, topologies, semantics, and entities for modelling temporal aspects such as representing dynamic data and time series and maintaining spatial objects' history and versions. This paper explores the temporal aspects of underground land administration (ULA) and investigates CityGML 3.0 entities for modelling these temporal aspects, with a synthetic prototype implemented as a proof of concept to demonstrate the applicability of a 4D ULA model. The result indicates that considering the temporal aspects of ULA using CityGML 3.0 entities can improve the functionality and capability of a land administration model in managing and communicating ownership information in underground areas.