## 2 Literature Review
### Integration of Integrated Hybrid 3D Modeling and Information Modeling (BIM) Platform  
As mentioned above, there are a number of techniques that can be used independently to create 3D scenes of historical architectural and cultural heritage. High-tech tools, such as the 3D-GIS digital city model, BIM technology, point-cloud scanning, and UAV (unmanned aerial vehicle) aerial photography, have been widely discussed and used in the field of conservation and the reproduction of historical buildings [2; 22]. However, as these technologies complement each other, no single technology can fulfill all requirements, thus, integrated hybrid modeling technology should be adopted to overcome the various limitations [23]. GIS and BIM were developed to meet the needs of specific fields, as different areas require different levels of model fineness and quality. BIM supports architecture at a more detailed scale, while GIS supports urban planning at a more macro scale, thus, the integration of BIM and GIS is becoming more common in the AEC industry. The use of parameterized models is very different from GIS in that they have different information sources and differ in scale [24]. Recent studies have also attempted to integrate GIS data with BIM data. BIM focuses on information related to individual buildings, while GISfocuses on topological spatial information and has broader spatial analysis and processing capability [25]. Therefore, the integration of 3D-GIS and BIM 3D city models can assist each other in the performance and control of different scales. In the case of Henrietta Street [1], the entire historical street was built through point-cloud scanning, and the historical building information model was imported into the BIM platform ArchiCAD to generate the final historical building information model. In the final stage, the model was transformed by CityGML, and using an interoperable format that can share data, it was imported into GIS for further analysis, which is very important for historical modeling. In the case of the Jeddah district [16], [PERSON] combined the BIM model with GIS data, and regarded it as the next stage of future research, as such integration can optimize BIM and 3D-GIS analysis of historical buildings and cultural heritage sites throughout the district. At present, the principles of 2D-GIS have been applied to 3D-GIS spatial data for more complex analysis, such as disaster management and cultural heritage information preservation. However, as only simple geometric elements are allowed in the GIS platform, it cannot create high-quality 3D models; therefore, the advantages of BIM and GIS should be combined [26]. However, the two models have different details, which will lead to the failure of interoperability in data exchange. Despite these incompatibilities, in order to overcome the specific weaknesses of BIM and GIS, many studies have tried various approaches and ensured that more stable and acceptable integrated hybrid modeling technology can be widely adopted [25]. In the case of Kursunlu Khan in Turkey [14], [PERSON] et al. mentioned that although databases could be built on GIS, GIS was still limited in terms of its 3D editing function. To solve this problem, they used Autodesk AutoCAD for 2D drawing, and SketchUp and Autodesk 3 DS Max for 3D modeling, and then, imported them into the GIS environment, where property sheets were created and connected to relevant building elements. The resulting database allows architects or professionals to search or navigate through the 3D models. While further data integration can be achieved in a GIS environment to provide users with a better understanding of the characteristics of historical buildings and cultural heritage sites, some information may be lost in the format conversion. In the case of Sant'Apollinare Nuovo, [PERSON] et al. also mentioned [26] that, in order to make the database structure more comprehensive and perfect, a perfect 3D model was required.