## 4 Experimentation on the Case Study
### Photogrammetric and Scanning 3D Reconstruction
Regardless of the terrain's complexity, GCPs ensure that the aerial data collected are accurate and reliable, particularly important when mapping urban areas. Before the actual flight, an in-depth evaluation of actual conditions (i.e., temperature, wind speeds, humidity, and chance of rain) was conducted to establish an effective and efficient flight trajectory. Initial planning included the appropriate altitude, speed, and image overlap to guarantee thorough coverage and data precision. A series of pre-flight checks (Figure 8c) were carried out to ensure that the UAS was performing as anticipated, confirming that all its systems were operational and working correctly. To enable spatial registration of thermal data, corresponding Red-Green-Blue (RGB) imagery is utilized. Three-dimensional reconstruction is achieved through Structure-from-Motion (SfM) photogrammetry, a process that leverages feature point correspondence across multiple images to determine camera pose and generate a dense 3D point cloud representing the building's geometry [29]. The UAS was equipped with a suitable camera, ensuring it was securely attached and properly calibrated, namely an integrated RGB camera for image/video capture, and a FLIR VUE PRO R640 camera (manufactured by Teledyne FLIR LLC, Wilsonville, OR, USA) for thermal assessment. While the orthophotography provides detailed imagery, the Digital Elevation Models (DEMs) offer essential elevation data. Together, they deliver a more complete and multi-dimensional understanding of a geographic area. An orthophoto (Figure 9) is a geometrically corrected aerial photograph that combines the image characteristics of a photograph with the geometric qualities of a map, and shows ground features in their true positions, allowing for accurate measurements of distance, angles, and areas. Orthophotos serve as a base layer in Geographic Information Systems (GIS) to overlay additional spatial data, analyse changes over time, and support decision-making processes. Figure 8: Equipment setup and calibration. A DEM (Figure 10) provides a representation of a terrain, showing elevation values over a geographic area. It is a 3D model of the terrain's surface, excluding trees. DEMs are used in topography, hydrology, geology, and other fields to model water flow, perform terrain analysis, calculate slope and aspect, and for simulations in environmental and engineering applications. While an orthophoto provides a 2D representation of the surveyed surface with accurate spatial and visual information, a DEM offers a 3D representation of it, with a focus on elevation. Furthermore, orthophotos show vegetation, buildings, and other features as they appear from above, while DEMs represent the terrain's elevation and do not include details like colours or textures of the surface features. Orthophotos and DEMs complement each other, providing detailed visual context about the land surface (orthophoto) and a quantitative understanding of the terrain's shape and elevation (DEM). Integration of orthophotos and DEMs in GIS enables better decision-making, aiding in infrastructure development, risk assessment, and environmental conservation. Using the UAS equipped with thermal camera (i.e., FLIR VUE PRO R640), the thermal efficiency assessment of three student dormitories (i.e., C6 and C8 presented in Figure 11, C22 presented in Figure 12 and G24 presented in Figure 13) was performed to identify  
Figure 10: Digital Elevation Model (DEM) of the studied area (Politehnica students’ accommodations: C6, C8, C22 and G24). Figure 9: Orthophoto of the studied area (Politehnica students’ accommodations: C6, C8, C22 and G24). potential areas of energy loss and opportunities for insulation enhancement. The aerial perspective offered a great overview [30], allowing the detection of the thermal profiles of the dormitories, which might be overlooked otherwise. The analysis will serve as a guide for future initiatives aimed at ensuring the sustainability of buildings and comfort for their occupants.