Ali Aien

Visualization requirements for 3D cadastral systems

Abstract In Australia, the cadastre stores and represents land ownership information in subdivision plans on paper and in digital documents (PDF). For a building subdivision, ownership boundaries are commonly drawn on floor plans, with cross-sections or isometric diagrams used to represent the 3D property rights. This method has significant shortcomings for representing property interests, especially in complex multi-level developments. The bounded 3D character of these developments requires numerous plans and sections which are difficult to interpret. It is also not possible to interact with such plans, modifications are not easy or efficient, and searching and measurement can only be done manually. In order to efficiently represent and work with land ownership and related information, this paper proposes a set of requirements (features) for interactive 3D cadastral visualization systems. In our methodology, important features, classified into three categories, have been identified by a review of the literature and also through a consultative workshop with industry partners. The first category includes features specific to visualization of the cadastre in 3D such as underground view and cross-section view. Second are those features that pertain to visualization systems generally such as interactivity and visual representation. Third are additional features that define how a 3D visualization system must behave such as usability and interoperability. A number of existing 3D visualization systems were evaluated against the identified features. Following this analysis, a prototype 3D visualization system was designed and implemented. Then, a case study was conducted to evaluate the performance of the developed system and this was presented to industry representatives through a workshop. Not all needs were met; for example, those involved in land registry sought greater support for validation of 3D spatial units. However most agreed that the prototype system is able to facilitate understanding of ownership boundaries. Using this feedback, our proposed features were reviewed according to the tasks and requirements of different users.

Utilising data modelling to understand the structure of 3D cadastres

No jurisdiction currently maintains a fully functioning 3D cadastre. Lack of legal support, guidelines, and available technologies for acquiring and visualising 3D cadastral objects provide reasons. Additionally, the scope of 3D cadastres is wide and ambiguous with no firm agreement on the necessity and structure of 3D cadastres. Without a clear scope and vision, implementation of 3D cadastres is difficult. This paper builds from this premise. It is argued that developing a 3D cadastral data model is an effective methodology to identify and understand the scope and nature of 3D cadastres. This paper proposes a 3D cadastral data model (3DCDM). The 3DCDM provides a practical framework to model layered legal objects of survey plans and their physical counterparts using architectural and engineering plans. The data model is based on the requirements of 3D cadastre and it provides a resilient starting point for developing a 3D cadastral database.

Design and development of a web-based 3D cadastral visualisation prototype

Three-dimensional (3D) developments of land, such as complex high-rises, put enormous pressure on current land administration systems that have ad hoc approaches to 3D property management. These approaches are unable to support effective 3D storage, analysis and visualisation of property information. Effective visualisation is one of the essential components in realisation of a truly 3D cadastre. Currently, several 3D visualisation applications and cadastral prototypes have been developed around the world. However, they do not effectively represent ownership information in 3D because they have not been developed based on 3D cadastral visualisation requirements. After candidate 3D visualisation solutions were compared with user-derived visualisation criteria, a web-based 3D visualisation prototype was designed and developed. The functionality, usability and efficiency of the prototype were evaluated by potential users involved in the registration and management of property. While there was a high level of enthusiasm for the features of the prototype, the results also suggest further directions for development of 3D cadastral visualisation.

Integrating Legal and Physical Dimensions of Urban Environments

Building Information Models (e.g., IFC) and virtual 3D city models (e.g., CityGML) are revolutionising the way we manage information about our cities. However, the main focus of these models is on the physical and functional characteristics of urban properties and facilities, which neglects the legal and ownership aspects. In contrast, cadastral data models, such as the Land Administration Domain Model (LADM), have been developed for legal information management purposes and model legal objects such as ownership boundaries without providing correspondence to the object’s physical attributes. Integration of legal and physical objects in the virtual 3D city and cadastral models would maximise their utility and flexibility to support different applications that require an integrated resource of both legal and physical information, such as urban space management and land development processes. The aim of this paper is to propose a data model that supports both legal and physical information of urban environments. The methodology to develop this data model is to extend the core cadastral data model and integrate urban features into the data model. The outcome of the research can be utilised to extend the current data models to increases their usability for different applications that require both legal and physical information.

Review and Assessment of Current Cadastral Data Models for 3D Cadastral Applications

Three-dimensional (3D) cadastres are often described as the 3D digital representation of real property rights, restrictions, and responsibilities (legal objects). They can also contain physical counterparts (physical objects) of legal objects such as buildings and utility networks, on, above or under the surface. Implementation of 3D cadastres requires many elements 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. Many jurisdictions have defined their own cadastral data models. However, none of them can fully support the requirements of 3D cadastres. This paper aims to explore the theories and concepts of the most common existing cadastral data models and investigate how they manage 3D legal and physical data. The result 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.