# L5 IN: Overview of an Indoor Navigation Pilot Project
## 2 L5 IN Project Overview
### Building Information Model  
A BIM is used to support indoor navigation within LSIN project. The underlying approaches for the decision are described in the following. The advantage of working with BIMs is that different information about a building can be collected centrally within a data set. Information that otherwise comes from different sources (such as drawings, tables, presentations, and charts) can be bundled within a BIM. The fact that working with BIMs allows the use of a combination of semantic, geometric, and topological attributes is one reason for their growing usage in different cases [13; 14]. Wherever possible, open data formats will be used in the L5 IN project. The data format of the Industry Foundation Classes (IFC) from buildingSmart is one of the most widely used formats. Even if not all software manufacturers have implemented the current IFC 4 schema yet, it will be used in the project due to its actuality. Further information on the schema can be found in the documentation provided by buildingSmart [15]. The use of the IFC schema can also be found in various other projects for purposes of geometric representation, routing, etc. [13; 16; 17]. Note that the IFC STEP Physical File (IFC SPF) is not the only way to export BIMs from the native data formats of the modeling software. Besides the IFC SPF, there are also export options in the form of data tree structures such as JSON or XML [18]. In contrast to the IFC SPF, these offer a more user-friendly and human-readable form and are therefore used in various other projects [13; 14] and will be in the L5 IN project as well. The BIM will be stored in a database for use in the L5 IN project; therefore, it should be considered that BIMs, in their function as a single source of information, have several features that are not required for indoor positioning and navigation. Like other projects, the model will be decomposed into geometrical, semantic, and topological dimensions, whereby the range of features will be reduced accordingly before they can be mapped in a suitable database framework [13; 19; 20; 21; 22]. The use of BIMs in the context of the presented project is shown below for subarea navigation and positioning separately. In the area of navigation, the project team expects added value from the use of a BIM for map creation and display, as well as for the generation of routing graphs. Due to the already mentioned role of the model as a single source of information for relevant building information, it makes sense to generate the required maps directly from the model. A distinction must be made whether the modeled 3D geometries of the BIM should be used directly for a navigation application [17] or if they should be abstracted from the 3D geometries and used as a 2D map [13; 19]. The existing geometry of the models are the basis for creating 2D maps. It will be investigated how a corresponding approach can be made using the data format IFC JSON, which is not yet officially published. Current algorithms for the conversion of IFC SPF into IFC JSON [23] are available from members of the technical room [24] of buildingSmart. This schema will be used to generate map data with the necessary details and information. Here, the model-based approach comes into play, so that both the semantic information (e.g., the occupancy, type of use, and accessibility of rooms) [19] and the topological information (e.g., door belongs to wall and wall is connected to room) [16] are used. For positioning tasks, the project is currently looking at various approaches that are intended to support the determination of the user's position, such as the provision of material information for the evaluation of the received signal strength, the provision of object information within the scope of map matching, and the modeling of landmarks to support positioning algorithms. To support the determination of the position based on the received 5G signals, information about the material properties of the surrounding components can be provided to the algorithm.