3D modelling of subsurface legal spaces and boundaries for 3D land administration

The increasing trend of urbanization results in various problems regarding enabling the livable cities such as traffic congestion, environmental pollution, and inadequate disaster preparedness. These problems are considerably related to deficiencies in the aboveground usable areas that can be exploited for the development of urban areas. Underground development is one of the strong solutions to cope with the aforementioned problems. The holistic planning of underground space is an important factor in ensuring the efficient use of underground space. Land administration that deals with the cadastral rights, restrictions, and responsibilities (RRRs) on the surface and subsurface is highly significant in the context of planning the underground space. By nature, there is a need for three-dimensional (3D) ownership information below the surface in order to carry out the analyses within planning studies regarding different aspects such as the existing subsurface structure and environmental impacts. This paper therefore enriches the core data model of the CityJSON standard such that it allows for 3D modelling of legal spaces and boundaries in the subsurface. It presents the usability of the proposed extension by visualizing the underground cadastral RRRs in 3D through the created and validated CityJSON file based on this extension. The practical opportunity arising from the use of CityJSON files derived from the developed extension is demonstrated. Different case studies are presented including the compliance checking regarding the designed underground tunnel within building permitting. The results of this study show that integrated 3D land administration including subsurface can contribute to the facilitation of the overarching planning of underground space.