## 3 Results
### PHASE 1--Modeling
#### 3.1.2 Stage 2--Creation of the BIM Model (Civil Engineering School)  
In step 1, _Previous Information and Data Collection_, all information was collected, including available plans in both paper and digital formats (*.dwg and *.pdf), along with data obtained from 3D laser scanning and architectural photogrammetry. Thus, the positioning work was carried out with a _Leica TS13, 5'_ robotic total topographic station, performing a total of 10 parking positions on the exterior of the building. For laser scanning inside the building, a _Leica-geosystem BLK360_ model was used (Figure 9a). For the georeferencing of the scans, 6'' circular targets were used (Figure 9b). Given the characteristics of the scanner and the building, 48 scans were considered adequate. For the processing of the data obtained by laser scanner, _Leica's Reality capture software_ was used, specifically the _register360_ and _cyclone3 DR_ tools, generating a total of 79 links (Figure 9c). The 48 scans were linked \"cloud to cloud\", obtaining a joint cloud. The joint cloud was also registered in the Project reference system. Figure 8: A 3D environment model. (**a**) A 3D environment in LoD 1 with ArcGIS Pro 2.7. (**b**) A 3D built environment of “Las Llamas” Campus LoD 2 with university buildings in LoD 3. Figure 7: Terrain definition. (**a**) The point cloud from the 2012 LiDAR flight of the PNOA is displayed over an orthophoto of Santander. This combination allowed for a detailed visualization of the terrain and building features, enhancing the understanding of the geographical landscape and facilitating further analysis in GIS applications. (**b**) Textured digital terrain model (DTM) of Santander. To generate the photogrammetric model of the building (Figure 10), a Canon EOS 5 DS R digital camera with 50.6 megapixels and fixed focal length lenses (28 mm, 35 mm, and 50 mm) was used. A total of 948 images were captured. The software used for this task was _Agisoft Metashape Pro_, version 1.8. Consequently, the 948 images of the project were oriented, achieving a ground sample distance (GSD) of 3.6 mm. This work generated several point cloud models and multiple mesh models. The _creation of the geometric model_ (step 2) has been developed in two ways, one using existing plans as a template and the other using point clouds obtained by 3D laser scanner or photogrammetry. In the case of the model from existing plans, it was generated in Autodesk _Revit 2019_ software from 2D digital plans (_dug_ and _pdf_) and on-site measurements (Figure 11). For the most part, the libraries of existing elements in the software were used, both for its architecture and installations, except for the construction of the facades that had to be modeled with the \"_mass_\" tool due to the non-existence of standard families of this unique building (Figure 12). On the other hand, the modeling from the point clouds obtained by laser scanning and photogrammetry was developed for the lower levels of the building. For this purpose, the elements of the model created from plans were readjusted in _Revit 2019_, importing and using the referenced point clouds as a reference. The reason for doing so was to avoid recreating all the building elements from scratch, thus optimizing the modeling process. Although the point cloud was properly referenced, it was necessary to set certain parameters in _Revit 2019_, such as the location of the project, the elevation, and the actual north of the project with respect to the north of the BIM software drawing space. Next, the  
Figure 10: Screenshot in Metashape Pro software, version 1.8. Textured photogrammetric mesh. Figure 9: (**a**) Laser scanner Leica-geosystem BLK360. (**b**) Circular targets used in the laser scans visualized in linked point clouds. (**c**) General approach to the processing of the point cloud obtained from the first floor of the Civil Engineering School.