## 3 Materials and Methods
### Electronic Instruments, Thermal Cameras, and UAS  
The pieces of electronic equipment used for the measurement of temperature were the following:  
1. A Hobo data logger (model U12, Onset, MA, US) (with 4 \(\times\) ext. channels) for measuring the AAT inside the wine cellars. It presents a 0.03 \({}^{\circ}\)C resolution and a +0.35 \({}^{\circ}\)C accuracy.
2. Two Hobo data loggers (model U23-001 Pro v2) for measuring both indoor and outdoor ambient conditions (AAT and Relative Humidity (RH)). They present a 0.02 \({}^{\circ}\)C resolution with a +0.21 \({}^{\circ}\)C accuracy for AAT, and a 0.03% resolution and a +2.5% accuracy for RH.
3. An XS Temp 7 portable thermometer (XS Instruments, Carpi, IT) equipped with a PT56C contact temperature probe to obtain ST measurements for cross-checking the thermal images radiometric measurements. The accuracy of this device is +0.15 \({}^{\circ}\)C (120 s).  
The locations of the data loggers and the temperature probes will be presented below. Two radiometric thermal imaging cameras from FLIR(tm) Systems, USA were used for the non-contact measurement of the Surface Temperature (SF) of the walls in the wine cellar. The first, called FLIR Vue Pro-R 640, is lightweight and compact, designed to be installed on board a UAS. The second, the FLIR B335, is a conventional handheld camera. The former presents a resolution of 640 \(\times\) 512 px, the maximum resolution that most UAS cameras allow without interpolation. The latter has a resolution of 320 \(\times\) 240 px. The focal length of both cameras is 19 mm; pictures of both devices are shown in Figure 3.  
Two methods were used to record the images of the cellar walls. Firstly, the FLIR VUE Pro R camera was installed on a UAS called Quasar(tm), manufactured by the company Dronetools(tm)-Sevilla. This 4-rotor aircraft has an autonomy of approximately 1 h carrying a payload of 1.2 kg. The thermal camera was installed together with a Sony(tm) mirrorless RGB camera, ILCE \(\alpha\)6000(tm), of 24 MPx. Both were mounted on a gimbal that kept them stabilised. The shots from the two cameras were synchronised, and the video transmitter installed on board allowed real-time video streaming to a monitor on the ground. Although the UAS  
Figure 3: Thermal cameras used during the study.  
always remained within the line of sight (LOS), the above system provided real-time video streaming as if the flight were being carried out in first-person view (FPV), ensuring in this way that the region of interest (ROI) was correctly captured. The second procedure, much simpler than the previous one, consisted of using a telescopic tool composed of three parts: the first was a telescopic lifting mast built with lightweight materials and a maximum working length of 7 m. This mast was employed to raise the FLIR B335 ground camera. At the extreme of the mast, the second part was attached: a ball-head mount locked the camera solidly in the desired position. Finally, the ground control unit (GCU) also included FPV glasses and a shoot button, which were commercial devices directly wired to the camera. The GCU was designed to be operated by only one person. Figures 4 and 5 show the UAS and the manual system respectively. The use of UAS and ground cameras allowed the study to be carried out redundantly by comparing the results obtained using both cameras.