# Integration of BIM and GIS for the Digitization of the Built Environment
## 1 Introduction
### Literature Review  
Several studies have been conducted in the field of BIM-GIS integration, with the objective of examining the potential benefits of combining these two technologies [34]. [PERSON] et al. [35] identify three use-case scenarios for this integration. Firstly, the examination of the 3D Industry Foundation Classes (IFC) model of a building or structure is conducted in comparison with the existing physical environment, which is represented by a 3D city model and in comparison with the specific type of zoning in the area. This process entails the generation of a continuously updated 3D city model. Furthermore, they investigate the use of urban area information and data in BIM, such as geospatial data, in the early design phase, particularly for infrastructure projects. This approach aims to provide a continuous flow of information that would eventually be combined with BIM data and used for maintenance purposes. Finally, the following research considers the integration of subsurface data in the initial BIM design phase. [PERSON] et al. [36] develop a multiscale approach based on a bi-directional integration between the two information systems, relating them appropriately and allowing easy switching between the databases of the two systems, mainly using open source (OS) tools (QGIS 3.20.3 and Dynamo 3.0.3). [PERSON] et al. [37] present a new method to integrate scanning data with BIM in a three-dimensional GIS. Using point cloud data from airborne laser scanning, detailed building information is automatically generated in the GIS. This approach offers benefits for urban planning, facilitating the management of buildings and improving visualization and analysis. The proposed process is flexible and algorithmic, with prototypes demonstrating its effectiveness in automatically generating BIM on three-dimensional GIS platforms, reducing manual effort. [PERSON] et al. [38] focus on developing a strategy for combining different data sources, including the use of BIM in CityGML within an existing GIS system. The process of converting BIM files into CityGML and transferring the data to the GIS software is analyzed. According to [38], the growing demand for digital tools in the field of spatial and urban analysis is highlighted, suggesting prospects for improving spatial data integration through the use of OS programs. [PERSON] et al. [39] analyze, through a systematic review, the capabilities of BIM-GIS integration in post-disaster prevention, response and recovery, to improve urban disaster management. Data acquisition, interoperability, data use and analysis are examined, and future directions of integrated BIM-GIS use are discussed. [PERSON] et al. [40]propose a decision framework that combines a GIS-based routing model and a genetic algorithm in a BIM environment to improve the planning of sporting events. They develop a framework that evaluates environmental variables in GIS routing models to consider the urban impact of sporting events and which allows route selection priorities to be modified according to user needs. By integrating data into BIM, models can be created and analyzed to assess urban impacts. [PERSON] et al. highlight the current phase of development and expansion of BIM-GIS integration, attributing this growth to the constant exploration and research in the field [41; 42]. The aim of this study is to provide an innovative strategy that can be applied in any BIM-GIS integration process, regardless of the specific requirements or intended uses. For this reason, two different methodologies are developed: one in the open-source environment (OSE), characterized by the possibility of access to the source code and the possibility of customization and modification by the developers, and the other in the closed-source environment (CSE), which requires the purchase of licenses to obtain a single shared environment that can host both building data and spatial data. In the OSE, interoperability between the two systems will be examined through the use of QGIS software.