## 5 Conclusions  
Reliable wireless communication links and systems are vital during natural disasters and/or man-made disasters, which can be a matter of life and death. Thus, drones could offer a wide range of services in a robust and cost-effective manner, including evaluating damage zones, coordinating rescue teams' activities, saving people's lives, accounting for missing people, and delivering good-quality signals in disaster areas. This paper has presented both software and hardware work to build a drone equipped with a thermal camera besides its communication payload to fly over disastrous zones to help identify lost people as part of robust and efficient search-and-rescue operations. The proposed modified Hata-Davidson empirical propagation model is introduced using the least squares tuning algorithm, and it shows outstanding performance in comparison to other empirical models using RME for validation. Moreover, the modified Hata-Davidson model is a noticeable contribution for calculating the path loss not only due to its consideration of the elevation angle in relation \(\theta\) to calculate the distance d that suits the drone's nature as a space-based system, but also to its enhancement of the Hata-Davidson model's outcomes using the least squares tuning algorithm. This adaptation yields improved coverage footprint, LoS connectivity, and RSS results from the receiver side. The Hata-Davidson model propagation model was selected as a representative of its empirical type, along with its main parameters of coverage distance, transmitter antenna height, receiver antenna height, and high range of frequency bands. The model exhibits better performance across different terrains, as well as some correction factors that yield high prediction accuracy in relation to other models. The complexity of Hata-Davidson model is its only downside. The experimental results show that up to 15 m of altitude, the drone with its current capabilities was able to identify a missing person via thermal imaging, besides detecting their GPS location. Therefore, this work can help governments, emergency centers, or civil defense organizations to carry out search-and rescue-operations in a timely and efficient fashion, especially when accessing rugged areas and finding missing persons. To provide more details about the proposed model's advantages in relation to existing models, Table 5 is presented. Further work can be elaborated in four possible directions to enhance these results. 1--Despite the high cost, a more powerful thermal camera would enhance thermal imaging quality. 2--Using a radio frequency identification (RFID) sensor, which can detect the signals of electronic devices, would offer the further element of detecting lost persons who do not appear on thermal camera images. 3--Using solar panels on larger drones would enhance the flying time. 4--Considering high-frequency bands, such as 12 GHz or higher. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Model** & **PL (dB)** & **RSS (dB)** & **SINR (dB)** & **T (mb/S)** & **Distance (km)** & **RMSE (dB)** \\ \hline SUI & \(-158.49\) & \(148.49\) & \(17.89\) & \(8.77\) & \(1.5\) & \(11\) \\ Cost-231 Hata & \(-161.35\) & \(151.35\) & \(19.02\) & \(9.24\) & \(1.6\) & \(12\) \\ [PERSON] & \(-159.48\) & \(149.48\) & \(17.63\) & \(8.65\) & \(1.5\) & \(9\) \\ Hata-Davidson & \(-150.72\) & \(140.72\) & \(15.79\) & \(10.19\) & \(1.3\) & \(7\) \\ Tuned Hata-Davidson & \(-135.3\) & \(125.3\) & \(14.68\) & \(11.43\) & \(1.6\) & \(3\) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Validation results of the modified Hata-Davidson model against other propagation models. **Author Contributions:** Conceptualization, methodology, software, formal analysis, investigation, writing--original draft preparation, writing--review and editing, supervision, project administration, funding acquisition F.A.A. Validation, resources, data curation, visualization B.O.S. All authors have read and agreed to the published version of the manuscript.