# Innovative System for BIM/GIS Integration in the Context of Urban Sustainability
## 2 Background  
In the literature, interoperability problems between BIM and GIS models are of particular interest, and in recent years, it has become possible to find numerous contributions focusing on applications where the connection between the two environments is necessary. Some interesting solutions have been achieved recently: [PERSON] et al. (2016) [18] explored an alternative method to generate a digital model of the site terrain morphology, where remote sensing data are applied in GIS studies. [PERSON] et al. (2008) [19] explored the suitability of BIM in a geospatial context to enhance data control in site selection and fire response management processes. Having a three-dimensional representation of the structure and its environs would therefore allow for managers to efficiently design a site layout and identify optimal locations for temporary structures. [PERSON] and [PERSON] (2012) [20] presented an original approach for integrating GIS and BIM that allows for executives to examine a 3D depiction of tower cranes in their optimal positions. As known, transferring data from BIM to GIS or vice versa poses challenges, having the necessity to consider both the format and the meaning of the data present in the two technologies. Current cutting-edge BIM (or GIS) tools facilitate data interchange between systems using a standardized data format [21]. For this reason, to fully integrate GIS and BIM, it is necessary to provide interoperability at the semantic level and many studies are proceeding in this direction [22]. Moreover, an additional option that is currently being investigated takes a realistic approach to overcome this constraint by using the original IFC and CityGML schemas inside a single database known as the Integrated BIM-GIS Database (BIGI-D). According to this conceptual paradigm, the phrase \"integrated database\" does not refer to a single, uniform database, but rather to a coherent technical environment that permits the use of data from both sources in various applications [23]. From an exclusively visualization point of view, the problem could be tackled in a completely separate way, using virtual reality techniques that, while solving the various problems still present today in the BIM/GIS integration, remain always virtual systems with all the limitations they bring with them. In this regard, it is noted that the use of virtual/augmented/mixed reality (VR/AR/MR) apps in the context of UP offers numerous advantages and opportunities [24; 25]. In the scientific literature, the use of these emerging technologies in UP and in the creation of so-called smart cities is widely discussed; in fact, the capabilities of VR/AR/MR are presented in facing the current challenges in the creation, modeling, and visualization of smart cities through the modeling of materials and the simulation of light in a VR environment [26]. Such studies can aid planners, stakeholders, and communities to better understand the role of planning policies in the development of an intelligent and sustainable city, particularly in the early design phases (but also in the monitoring phases [27]). The significant roles of tools, such as VR/AR/MR, in meeting the real-time simulation and visualization requirements for smart cities are emphasized in the literature [28; 29; 30; 31]. Others emerging tools in the field are web-based platforms like Cesium [32; 33]. Whether examining satellite photos, topographical data, or point cloud information, Cesium provides the performance and versatility required to handle a wide range of geospatial datasets. Moreover, users may include dynamic or real-time data (very important in the context of UP) into their applications thanks to Cesium's flexibility and possibility to integrate several data sources and services in a unique environment. This makes it possible to create dynamic, current geospatial visualizations and simulations that are accessible and shareable across many devices.