© 2013 Dr. Ali Aien ; The need for more ‘space’ resulting from population growth, urbanisation and industrialisation has increased the pressure on land-use planning and development. As a result, space above and below ground level is increasingly used. Examples include underground developments, infrastructure facilities, high-rise buildings, and apartments. To extend the use and functionality of the land, complex infrastructures are being built, both vertically and horizontally, layered and stacked. These three-dimensional (3D) developments affect the interests attached to the underlying land. 3D cadastres will assist in managing the effects of 3D development and increase the functionality of a multipurpose cadastre. 3D cadastres are digital representations of real property ownership rights, restrictions, and responsibilities (legal objects) and their corresponding physical objects such as buildings, utilities, on, above or under the ground surface. They are equipped with 3D data storage, 3D visualisation, and 3D spatial analysis functions. They facilitate management of property rights; registration of strata plans; and reduction of boundary disputes between owners and Owners Corporations. They also enable a wide variety of applications, which in turn create a demand for detailed and integrated 3D legal and physical objects. To successfully implement the 3D cadastre and efficiently deliver the above-mentioned objectives, many elements must support a digital 3D cadastre, such as existing 3D property registration laws, appropriate 3D data collection 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 and physical objects. Many jurisdictions, organisations and software developers have developed their own cadastral data model. Examples of data-modelling ...