Exploring the 3rd dimension within public law restrictions: A case study of Victoria, Australia

The urban environment is characterised by increasingly complex relations driven by the needs of modern societies, such as multi-purpose buildings and composite infrastructures. However, the capabilities for extensive vertical exploitation of land provided by construction technology are related to the expansion of public utilities. This results in administrative restrictions on land and developments, known as Public Law Restrictions (PLRs). PLRs impose explicit and implied 3D restrictions, as well as restrictions of non-geometrical characteristics such as noise or groundwater pollution. This paper investigates if and how 3D modelling may contribute to better manage and enforce PLRs in a 3D framework. To this end, the 3D PLRs required for the urban planning approval process in Victoria, Australia are examined. Requirements and guidelines were analysed in order to identify explicit, non-geometrical and implied 3D PLRs. To accomplish this, the spatial structure of two well-known 3D data models, CityGML and Industry Foundation Classes (IFC), were investigated, highlighting the advantages and drawbacks of these models in the management of 3D PLRs. The paper concludes that the implementation of a 3D PLR system requires addressing issues of scale differentiations (building scale or city scale of 3D data models in contrast to extensive, non-parcel-based PLRs), “translation” of qualitative characteristics to specific height, depth or volumetric restrictions, and modelling of invisible, non-material legal spaces.