Towards integration of 3D legal and physical objects in cadastral data models

• Current cadastral data models are not sufficiently supporting the requirements of 3D cadastres.
• 3D physical objects as well as 3D legal objects are important in 3D cadastres.
• We proposed 3DCDM model as a 3D cadastral data model to improve the current cadastral data models.
• The 3DCDM model has two hierarchies, legal and physical, which are linked in the model.

Digital 3D cadastres are often envisaged as the visualisation of 3D property rights (legal objects) and to some extent, their physical counterparts (physical objects) such as buildings and utility networks on, above and under the surface. They facilitate registration and management of 3D properties and reduction of boundary disputes. They also enable a wide variety of applications that in turn identify detailed and integrated 3D legal and physical objects for property management and city space management (3D land use management).Efficient delivery and implementation of these applications require many elements to support a digital 3D cadastre, such as existing 3D property registration laws, appropriate 3D data acquisition methods, 3D spatial database management systems, and functional 3D visualisation platforms. In addition, an appropriate 3D cadastral data model can also play a key role to ensure successful development of the 3D cadastre.A 3D cadastral data model needs to reflect the complexity and interrelations of 3D legal objects and their physical counterparts. Many jurisdictions have defined their own cadastral data models for legal purposes and have neglected the third dimension, integration of physical counterparts and semantic aspects.To address these problems, this paper aims to investigate why existing cadastral data models do not facilitate effective representation and analysis of 3D data, integration of 3D legal objects with their physical counterparts, and semantics. Then, a 3D cadastral data model (3DCDM) is proposed as a solution to improve the current cadastral data models. The data model is developed based on the ISO standards. UML modelling language is used to specify the data model. The results of this research can be used by cadastral data modellers to improve existing or develop new cadastral data models to support the requirements of 3D cadastres.