Abstract. The problem of georeferencing building information modelling (BIM) models is complex and in need of a comprehensive solution. We focus on the open BIM data format Industry Foundation Classes (IFC) and its georeferencing implementation. The requirements voiced by the domain experts during recent years have been collected and analysed. While IFC already covers some of the concepts, we propose an extension to the IFC schema to handle the inadequacy. Our proposal composes of two new entities: one supports geographic coordinate reference systems (CRSs) and the other enables a rigid transformation of BIM geometries. We showcase the possibilities with three examples, one for each of the required scenarios. The improvements assure much-needed semantically clear definitions of the georeferencing concept within the IFC data model. As such, the interpretation of IFC data content is unambiguous for stakeholders and software implementers.

The open data exchange standard Industry Foundation Classes (IFC) has been recently significantly extended to also cover infrastructure facilities such as roads and railways. The results of these activities form part of version 4.3 of the standard. Linear placement of objects is one of the most important concepts in infrastructure asset modelling. As such, Release Candidate 1 of IFC 4.3 has been critically analysed. In this paper, we address several issues that were identified together with the participants of the IFC Infrastructure Extension Deployment and IFC Rail Phase 2 projects. We present an improved model removing unnecessary doubling of concepts and reusing many already established entities. We showcase the new model on two example scenarios from one of the projects and determine better adherence with the IFC legacy. The proposed improvements have been adopted in Release Candidate 2 of the IFC 4.3.