## 1 Introduction
### Previous BIM-GIS Integration  
Despite the differences in the semantic and domains, BIM and GIS have been integrated for many applications. IFC standards represent and standardize BIM models, while CityGML is the standard and widely used schema for the GIS-based models. BIM domains are mainly focused on new design construction projects that contain very detailed information about each object, while the GIS domain mainly focuses on the existing assets at different stages of the project, supporting accurate geographic coordinate systems and geospatial analysis. The main advantage of BIM over GIS is the representation and management of comprehensive and detailed information; however, it lacks geospatial analysis support. On the other hand, GIS has an advantage over BIM in support of geospatial capabilities and the management of geospatial territory information about assets; however, the asset details are less. Initially, these two technologies were developed for different fields of application. The integration of the two technologies can be highly beneficial for the AEC industry and can hugely contribute to sustainable infrastructure practices [20]. The two systems have been integrated into the three methods in the literature: (1) BIM to GIS integration, (2) GIS into BIM integration, and (3) integration of both BIM and GIS into a new system. The existing literature mainly focuses to integrate BIM data into GIS for different applications. Some of the application areas where BIM data are integrated into GIS includes urban development, site selection, indoor and outdoor emergency response management, and pedestrian pathway planning. Usually, GIS is used in urban management fields such as urban development, site selection, and fire response management; however, such tasks also require geometric and semantic information that can be provided by BIM. In this context, BIM data of the 3D semantic building model was integrated into GIS that was achieved by mapping the IFC data model into the CityGML data model for urban development [21]. In another example, three software components were developed to integrate BIM into GIS for site selection and fire response management by developing [22]. In the case of pedestrian route planning and emergency response management, the indoor and outdoor geospatial information is needed; however, achieving indoor information is very difficult and time-consuming. Therefore, using BIM to GIS data mapping, researchers developed a multi-purpose geometric network model (MGNM) to connect indoor and outdoor network and use them for emergency response and pedestrian route planning [17]. The results indicated that the BIM model providing indoor information and its integration with GIS links the outdoor information that can be used by practitioners for multiple purposes. In another study, a framework was developed on the basis of an ontology that collects information from a BIM model and integrates with GIS existing information for safe route planning to school in urban areas [23]. Moreover, in [24], the IFC-based BIM model was developed and integrated with ArcGIS using an interoperability tool to support indoor spatial analysis. It can be seen from the previous studies that most of the researchers used data mapping technique (IFC to CityGML mapping) for integration to enhance the application of existing GIS contextual information. Some of the studies used existing IFC and CityGML data models and commercial tools, such as [22; 23; 24; 25], while many researchers have developed new tools and extensions [17; 21; 26]. In [27], a CityGML extension was developed called GeoBIM, which supports semantic IFC information transfer into CityGML. The above-mentioned studies discuss the integration of BIM data into GIS for various applications, providing effective tools and methods. The other possible method to integrate these two systems is to transfer GIS data into BIM. This kind of integration is also achieved in many application areas such as environmental analysis and construction management.