# Graphic Applications of Unmanned Aerial Vehicles (UAVs) in the Study of Industrial Heritage Assets
## 3 Methodology for the UAV Use in Graphic Application
It is important to highlight that this proposed methodology can be applied to the use of UAVs in heritage research, the generation of 3D asset models using photogrammetry techniques, the study of energy efficiency as well as to other actions on the assets. This only requires adapting the methodology of information processing and data analysis. For 3D assets models using photogrammetry, during flight execution different apps can be employed to take photographs (i.e., Pix4D Capture, Mission Planner, etc.) where the image captures are distributed around the asset area. In addition, different photogrammetry software packages can be employed to process the different images and generate the assets 3D model (Pix4D, Drone2 map, Agisoft Metashape, etc.). On the other hand, referring to asset energy efficiency analysis, thermographic images can be taken using a special camera mounted on the UAV, and the captured images can be processed using different software (testo IRSoft, FLIR Tools, etc.). This general methodology has been applied to generate aerial images in the case of the San Joaquin sugar cane factory and the Aguila aquduct, located in Nerja (Spain). The main reasons to select these  
Figure 2: Methodology for the UAV use in graphic applications. assets are that, in this area, different sugar cane factories were installed in the second half of the 20 th century, and both assets are related due to the aqueduct that supplied water to the factory. Google Maps was employed for the asset location analysis. The geographical coordinates of the aqueduct (36 deg45'29.24'' N 3 deg50'59.70'' W) and the factory (36 deg45'36.26'' N 3 deg51'13.54'' W) have been obtained and the distance between both assets has been measured (398 m). Moreover, the environment around the assets has been analysed. The third party damage risk is reduced due to the location of the assets on agricultural land and the lack of pedestrian access around the area. In spite of this, a road with normal vehicle traffic separates the aqueduct and the factory and so, special attention is needed when the UAV flies over the road. Restricted flight area maps of the national authority have been consulted, not finding any restrictions. In this case, no governmental authorization is required. The assets were visited prior to the flight operation. Different interesting elements to photograph (chimney, irrigation pond, etc.) were selected and possible obstacles to flight operation (electrical wiring, bridge, etc.) were identified. A multirotor UAV has been selected for the flight operation. A MAVIC pro platinum model has been employed (Figure 3). The main UAV technical characteristics are listed in Table 2.  
Once the environmental and the information of the assets of interest were collected, a flight plan was developed. This plan list different actions to be carried out and the materials required. Furthermore, these actions were divided into three flight operations considering the UAV's 15 min of artery life. The flight operations were carried out with the UAV according to the flight plan. In addition, different references were measured in the assets to obtain indirect measurements that would be very complex or too expensive to carry out directly (chimney diameter, chimney height, irrigation water \begin{table}
\begin{tabular}{c c} \hline \hline
**Weight (Including Battery and Propellers)** & **734 g** \\ \hline Satellite positioning system & GPS/GLONASS \\ Camera sensor & 1/2.3 (CMOS). 12.71 Mpx \\ Focal distance & 35 mm \\ Image size & \(4000\times 3000\) \\ Video mode & C4K, 4K, FHD, HD \\ Battery capacity & 3830 mAh \\ Battery weight & 240 g \\ \hline \hline \end{tabular}
\end{table} 
Table 2: MAVIC pro platinum technical characteristics. Figure 3: MAVIC pro platinum model UAV. pond area, etc.). The photographs and video generated were processed and analysed. In addition, different indirect measurements were obtained. Finally, a comparison between the use of conventional imaging systems (video or photograph camera) and UAVs have been made.