A Unified Building Model for 3D Urban GIS

Abstract

Several tasks in urban and architectural design are today undertaken in a geospatial context. Building Information Models (BIM) and geospatial technologies offer 3D data models that provide information about buildings and the surrounding environment. The Industry Foundation Classes (IFC) and CityGML are today the two most prominent semantic models for representation of BIM and geospatial models respectively. CityGML has emerged as a standard for modeling city models while IFC has been developed as a reference model for building objects and sites. Current CAD and geospatial software provide tools that allow the conversion of information from one format to the other. These tools are however fairly limited in their capabilities, often resulting in data and information losses in the transformations. This paper describes a new approach for data integration based on a unified building model (UBM) which encapsulates both the CityGML and IFC models, thus avoiding translations between the models and loss of information. To build the UBM, all classes and related concepts were initially collected from both models, overlapping concepts were merged, new objects were created to ensure the capturing of both indoor and outdoor objects, and finally, spatial relationships between the objects were redefined. Unified Modeling Language (UML) notations were used for representing its objects and relationships between them. There are two use-case scenarios, both set in a hospital: "evacuation" and "allocating spaces for patient wards" were developed to validate and test the proposed UBM data model. Based on these two scenarios, four validation queries were defined in order to validate the appropriateness of the proposed unified building model. It has been validated, through the case scenarios and four queries, that the UBM being developed is able to integrate CityGML data as well as IFC data in an apparently seamless way. Constraints and enrichment functions are used for populating empty database tables and fields. The motivation scenarios also show the needs and benefits of having an integrated approach to the modeling of indoor and outdoor spatial features.

Applications of 3D City Models: State of the Art Review

“…• Recent advances in augmented reality [392] and virtual reality [393]; developments in the fusion of computer graphics, GIS and BIM (e.g., [394][395][396][397][398][399]); and advances in procedural modelling [21,22,[400][401][402] appear as promising catalysts that will contribute to providing 3D city models to practitioners.…”

Processing BIM and GIS Models in Practice: Experiences and Recommendations from a GeoBIM Project in The Netherlands

“…El-Mekawy et al [2] and El-Mekawy et al [3] propose to combine information from both domains and create a unified model in which all the semantic properties of IFC and CityGML are present, and they propose using bidirectional mappings for all the semantic classes relevant to IFC and CityGML. Amirebrahimi et al [4] extends the data model of GML (and not CityGML) to create a unified model supporting two specific applications (visualisation and flood damage assessment to specific buildings).…”

“…Even as researchers and practitioners have studied how to best share information between BIM and GIS and how to address all the differences from different perspectives (Section 2.2), it is still very hard (if not impossible) to share 3D information among different users throughout the life cycle of urban and environmental processes, i.e., from plan, design and construction to maintenance-especially when trying to do so using open standards. Moreover, most of the research conducted so far has focused on the high-level and semantic aspects of GIS-BIM integration (e.g., conceptually mapping equivalent types) [2][3][4][5], mostly avoiding the more complex tasks involving geometric processing (e.g., conversions, geometric validation and automated tests using said geometries in a manner that is consistent with how geometries are represented in both domains). Without a domain-aware geometry conversion/integration, it it not possible to use the resulting datasets as input in the existing software packages used in the BIM and the GIS communities.…”

GIS-Based Planning and Modeling for Renewable Energy: Challenges and Future Research Avenues

“…This means that GIS-based approaches are combined with building information modeling (BIM) based methods in energy system modeling and analysis [96]. Currently, we are witnessing the fast rise of the usage of 3D building models for the calculation of solar potential using faç ade visibility.…”