# Assessing Spatiotemporal LST Variations in Urban Landscapes Using Diurnal UAV Thermography
## 3 Methods
### Study Area and Data Acquisition  
This study was conducted on the Harran University Osmanbey Campus--a spatially diverse area featuring multiple LULC types such as lakes, bare soil, built-up areas, grasslands, and roads. Located in Sanlurfa, the campus experiences a hot Mediterranean climate (Koppen-Geiger classification: Csa) with hot, dry summers and mild, wet winters [40; 41; 42]. Its well-defined, urban-like setting makes it an ideal site for investigating diurnal variations in LST across different surface types (Figure 1).  
Figure 1: Study area of Harran University Osmanbey Campus.  
Data collection involved comprehensive thermal data acquisition using a DJI Mavic 3T Thermal quadcopter UAV (manufactured by DJI Technology Co., Ltd. headquartered in Shenzhen, China), which was selected for its advanced dual-camera payload system [43]. This system is equipped with a primary radiometric thermal camera utilizing a 640 \(\times\) 512 pixel microbolometer array and a 40 mm lens with a 61\({}^{\circ}\) diagonal field of view. The thermal imager operates within the long-wave infrared spectral range (8-14 \(\upmu\)m) and features a low noise equivalent temperature difference, enabling the acquisition of high-fidelity temperature measurements across a detection range from \(-\)20 \({}^{\circ}\)C to 150 \({}^{\circ}\)C. The system maintains a temperature measurement accuracy of \(\pm\)2 \({}^{\circ}\)C or \(\pm\)2% of the reading, whichever is greater. Complementing the thermal sensor, a secondary RGB camera, featuring a 4/3 CMOS sensor with a mechanical shutter, captured concurrent visual imagery at a resolution of 20 megapixels (5280 \(\times\) 3956 pixels).  
UAV flights were systematically conducted over the campus area in January 2025 at four distinct diurnal periods: morning (8:00-9:00), afternoon (12:00-13:00), evening (17:00-18:00), and midnight (22:00-23:00). These periods were specifically chosen to capture the key phases of diurnal thermal dynamics, from peak solar radiation to nocturnal cooling (sunrise: 7:30, sunset: 17:46). Photogrammetric UAV flights were executed following a standardized flight plan at a height of 40 m, with 80% transverse and longitudinal overlap ratios, yielding 1524 thermal aerial images per flight at a ground sample resolution of 5.66 cm/pix. Concurrent with thermal data acquisition, ambient air temperature measurements were recorded using a standard digital thermometer positioned at the UAV launch location. Temperature readings were taken at the beginning and end of each flight period (morning, afternoon, evening, and midnight) at approximately 1.5 m above ground level to provide contextual reference data for the thermal imagery analysis. It should be noted that these ambient temperature measurements were collected primarily to establish general atmospheric conditions during the data acquisition periods rather than to characterize the microclimate of specific LULC classes. A single representative temperature value was calculated for each diurnal period by averaging the recorded measurements. These ambient temperature reference points serve as important contextual data for interpreting the relative patterns in the thermal orthophotos, particularly when assessing the differential between air temperature and surface temperature across various LULC types.