Mapping between BIM and 3D GIS in different levels of detail using schema mediation and instance comparison

• Developed and validated bidirectional mapping between IFC and CityGML.
• Generated mapping rules on entities and representations using instance-based method.
• Developed a reference ontology for seamless data integration between BIM and GIS.
• Developed level of detail harmonization in CityGML.

The Building Information Modeling (BIM) domain and the Geographic Information System (GIS) domain share a mutual need for information from each other. Information from GIS can facilitate BIM applications such as site selection and onsite material layout, while BIM models could help generate detailed models in GIS and achieve better utility management. The mapping between the key schemas in the BIM domain and the GIS domain is the most critical step towards interoperability between the two domains. In this study, Industry Foundation Classes (IFC) and City Geography Markup Language (CityGML) were chosen as the key schemas due to their wide applications in the BIM domain and the GIS domain, respectively. We used an instance-based method to generate the mapping rules between IFC and CityGML based on the inspection of entities representing the same component in the same model. It ensures accurate mapping between the two schemas. The transformation of coordinate systems and geometry are two major issues addressed in the instance-based method. Considering the difference in schema structure and information richness between the two schemas, a reference ontology called Semantic City Model was developed and an instance-based method was adopted. The Semantic City Model captures all the relevant information from BIM models and GIS models during the mapping process. Since CityGML is defined in five levels of detail (LoD), the harmonization among LoDs in CityGML was also developed in order to complete the mapping. The test results show that the developed framework can achieve automatic data mapping between IFC and CityGML in different LoDs. Furthermore, the developed Semantic City Model is extensible and can be the basis for other schema mappings between the BIM domain and the GIS domain.