# Integrating BIM and GIS for an Existing Infrastructure
## 1 Introduction  
The integration of building information modelling (BIM) and geographic information systems (GIS) is one of the topics to be addressed in the digitalisation of the architecture, engineering, construction, and operation (AECO) sector. These two technological approaches are based on the organisation and analysis of information. However, their character is different. BIM works on specific infrastructure, while GIS covers large areas of land [1]. Digital transformation has enabled a greater volume and analysis of information that is available during the life cycle of an asset (LCA). This is where BIM-GIS integration becomes relevant, making it possible to understand the behaviour of an infrastructure in its environment. Both BIM and GIS are used in the whole life cycle of the built environment, from the design and planning phase through to the management and maintenance of the infrastructure [2; 3]. Thus, the combination of these two approaches can improve the decision-making process in all phases. This integration can be applied in the building sector, where an individual building is positioned within its location in the city, and in road infrastructure, where geospatial data is linked to the specific site [4]. The use of these technologies during the operation and maintenance (O&M) phase combines the information, thus enabling more reliable decision-making, allowing infrastructure managers to optimise the available resources [5; 6]. However, BIM and GIS employ different approaches, leading to the technology and standards associated with them being different. The best example of this divergence is the standardisation, which is fundamental in both environments to facilitate collaboration among all project stakeholders, promoting interoperability and information exchange. This article discusses how each of these two technologies is getting closer to standardisation, and specifically how standardisation could be an approach to a reliable BIM-GIS integration. Some of the main formats and international standards of each technologywill be identified. The flow of information from GIS to BIM and from BIM to GIS is also discussed. This flow has been the subject of most of the recently published literature, focusing especially on the use of the standard IFC and CityGML formats for BIM and GIS, respectively. However, some authors have highlighted the complexity of the information transformation process between both formats [1; 7]. Furthermore, success in the development of a model that includes the benefits of each technology involves the application of new enabling technologies that analyse information, i.e., the digital transformation of the AECO sector. Technologies based on big data, such as the Internet of Things (IoT) or artificial intelligence (AI) will be key in smart construction [5; 8; 9; 10; 11; 12]. BIM and GIS are complementary technologies that together with enabling technologies will allow the development of digital twins (DTs) of infrastructure [7; 13; 14; 15; 16; 17]. The use of proprietary applications focused on specific infrastructure requirements facilitates access to information, which is essential in the digitization of infrastructure. These applications allow not only access to the 3D model, regardless of the application used to develop it, but also access to the database (DB) and its analytics from adapted and intuitive interfaces [17; 18; 19; 20]. It is therefore crucial to establish a quick and efficient information flow in order to extend the application of BIM-GIS integration in the AECO sector. Lastly, a case study is presented that proposes a facility management (FM) system for an existing road. This is Madrid Calle 30, one of the main highways serving the city of Madrid (Spain). The O&M of this road is nowadays carried out using GIS technology supported by an external database The size of this urban infrastructure, more than 30 km long, demands a constant optimization of the resources available for its O&M. Therefore, BIM-GIS integration could be an option.