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The Level-of-Detail (LOD) 2 building models defined in CityGML are used widely in three-dimensional (3D) city applications. Many of these applications demand valid solid-based geometry (closed 2-manifold), which is crucial for analytical and computational purposes. However, this condition is often violated in practice because of the way LOD2 models are constructed and exchanged. Examples of the resulting errors include missing surfaces, intersecting building parts, and superfluous interior geometry. In this study, we present a heuristic shrink-wrapping algorithm for reconstructing valid solid-based LOD2 buildings by repairing and generalizing invalid input models. A single building model is first decomposed as intersection-free and reassembled by constrained tetrahedralization. The bounding membrane is then shrunk by incrementally carving the selected boundary tetrahedra and wrapping the expected shape of the building. In the algorithm, combinations of heuristics are proposed to guide the carving process. Topological and geometrical constraints are proposed to ensure the validity and exactness of the output model. The semantics of the input geometry are preserved and missing semantics are deduced based on pragmatic rules. We evaluated the performance of the algorithm using 3D building models, including CityGML datasets. The results showed that our method achieved state-of-the-art performance at repairing 3D building models.

To support building permit issuing with automatic digital tools, the reuse of models produced by designers would make the process quicker and more objective. However, current studies and pilots often leave a gap with respect to the models as actually provided by architects, having varying quality and content. In this study, rather than taking a top down approach, we started from the available data and made the necessary inferences, which gave the opportunity to tackle basic and common issues often preventing smooth automatic processing. Specific characteristics of the IFC models were outlined and a tool was developed to extract the necessary information from them to check representative regulations. While the case study is specific in location, regulations and input models, the type of issues encountered are a generally applicable example for automated code compliance checking. This represents a solid base for future works towards the automation of building permits issuing., Comment: Author version of the manuscript, published by Automation in construction

Integrating updates from timely sources such as volunteered geographic information (VGI) into the spatial data maintained at official agencies is becoming a more demanding requirement but presents many challenges. This paper proposes an approach to addressing the technical challenge of propagating updates from timely sources (e.g. OpenStreetMap) to spatial data maintained at separate map scales. The main idea is to establish a multiple representation database (MRDB) for datasets at different scales and time to facilitate incremental update, where linkages between corresponding objects at different datasets are made explicit. First, two ways in which the timely sources can be integrated into official data for incremental update are discussed. To derive the linkages between different datasets, a data matching procedure based on computer vision is presented and fine-tuned to match data in different scale ranges. Furthermore, the generalization history used to produce smaller scale data from the larger ones in official data is inferred based on the linkages, and is then used to guide the update propagation. Finally, a framework for incremental generalization in MRDBs is proposed, where crucial issues like strategies for update propagation, cartographic generalization, and the so-called ‘chain reaction’ are addressed. The framework is implemented as a fully automated process where operators like simplification, enlargement, compression, displacement and typification are incorporated into the incremental update process. By testing the framework against real world data sets (i.e. OpenStreetMap and official data at 1:10k, 1:50k and 1:100k), we show that the updates are integrated consistently into existing data in terms of spatial relations and cartographic quality. Our work suggests that making use of timely sources by official mapping agencies and companies in a continuous or event-driven data update is technically feasible, with further improvement and extensions discussed.

Spatial Data Infrastructures (SDIs) aim at making spatial (geographical) data and thus content available for the benefit of the economy and of the society. Agreement and sharing of vocabularies within the SDI are vital for interoperability. But there is a limitation: many vocabularies have been defined within domains while other domains have not been taken into account. Therefore, little harmonisation has been achieved and data sharing between domains within the SDI is problematic. This paper presents a methodology and tools for non-automatic, community driven ontology matching that we developed to harmonise the definition of concepts in domain models that are already being defined and used in operational use cases. Besides the methodology and tools that we developed, we describe our experiences and lessons learned as well as future work.

The level of detail in 3D city modelling, despite its usefulness and importance, is still an ambiguous and undefined term. It is used for the communication of how thoroughly real-world features have been acquired and modelled, as we demonstrate in this paper. Its definitions vary greatly between practitioners, standards and institutions. We fundamentally discuss the concept, and we provide a formal and consistent framework to define discrete and continuous levels of detail (LODs), by determining six metrics that constitute it, and by discussing their quantification and their relations. The resulting LODs are discretisations of functions of metrics that can be specified in an acquisition–modelling specification form that we introduce. The advantages of this approach over existing paradigms are formalisation, consistency, continuity, and finer specification of LODs. As an example of the realisation of the framework, we derive a series of 10 discrete LODs. We give a proposal for the integration of the framework within the OGC standard CityGML (through the Application Domain Extension).

The aim of matching spatial data at different map scales is to find corresponding objects at different levels of detail (LODs) that represent the same real-world phenomena. This is a prerequisite for integrating, evaluating and updating spatial data collected and maintained at various scales. However, matching spatial data is not straightforward due to the ambiguities caused by problems like many-to-many correspondence, non-systematic displacement and different LODs between data sets. This paper proposes an approach to matching areal objects (e.g. buildings) based on relaxation labeling techniques widely applied in pattern recognition and computer vision. The underlying idea is to utilize contextual information (quantified by compatibility coefficient) in an iterative process, where the ambiguities are reduced until a consistent matching is achieved. This paper describes (1) a domain-specific extension to previous relaxation schemes and (2) a new compatibility coefficient that exploits relative relationships between areal object pairs in spatial data. Our approach were validated through extensive experiments using building data sets at 1:10k and 1:50k as an example. Our contextual approach showed superior performance against a non-contextual approach in general and especially in ambiguous situations. The proposed approach can also be applied to matching other areal features and/or for a different scale range.

The ways society use and occupy space occur in multiple dimensions; however, the ways we manage and administer space relies on two-dimensional information representations (2D). The legal ambiguity and administrative limitations inherent in such practices are becoming increasingly pronounced within land administration especially for urban areas. In response, a research domain has emerged – termed by specialists as ‘3D Cadastres’ – to seek greater correspondence between the administration of legal land and property (parcel) boundaries and the reality of physical bounds of structures themselves. Within this corpus of literature, advances in the technical domain are evident. However, other areas of research have not experienced the same degree of attention, with a particular lag in analysis of legal issues: this apparently explains the lack of progress in the realisation of operational 3D cadastres. However, given many countries actually already administer ownership of 3D property within current statutory frameworks, is the continued concentration on legal issues a red herring? Are legal issues significant barriers to implementation, and if not, what other considerations are there? This position paper, comprising two main sections, aims to consider, clarify and reconceptualise the significance of the law as an obstacle to implementation of 3D cadastres. It does this by firstly reviewing the legal issues articulated within the literature and examining the extent of its impact using current practical examples. This leads to the conclusion that finding alternative methods and processes to overcome perceived legal issues actually facilitates progress towards 3D property registration and therefore, 3D cadastre implementation. This challenges the dominant assumption that legal issues are a significant barrier. The paper then proposes to consider the influence of legal issues through an institutional lens, as a way of gaining other insights into how legal issues can influence 3D cadastre implementation. The introduction of institutional theory and a theoretical framework provides a way to reconceptualise the role of legal issues in 3D cadastre implementation. The framework is further used as a sensitising mechanism for discussing broad-based institutional issues that have as yet, not been given significant consideration in the literature. The paper concludes with a response to the main research question and the proposition that significant barriers to 3D cadastre implementation lies not in technological or legal issues, but the more fundamental social and cultural issues that make up the institutional framework underpinning cadastral systems.

This paper presents the design and implementation of the cadastral system extension for registration of 3D rights and restrictions in the Netherlands fitting within the ISO 19152, Land Administration Domain Model (LADM) final draft international standard. The implementation will be conducted in two phases. The first phase of the solution does not require a change of the legal and cadastral frameworks and will be used to gain experience in the challenging domain of 3D cadastre where technical and legal aspects interact. Typical 3D cadastral objects are analysed including their current registration. A procedure to improve the registration is developed that includes an extension of the cadastral system to accept 3D descriptions in 3D pdf format as part of the deed. One of the drawbacks of this solution is that it is not possible to validate the 3D cadastral representations (Are the volumes closed? Are the neighbours non-overlapping?) The second phase is research in progress and comprises the actual inclusion of the 3D data in the registration, enabling complete validation and even better 3D data management and dissemination. Based on experiences to be collected from the first phase and experiences from other countries, the solution for the second phase will be further refined and subsequently implemented in due time.