## 5 Conclusions  
The use of UAVs is becoming more frequent in applications related to architecture and urbanism. The revolution in unmanned aerial vehicles offers new opportunities in different applications due to the reduction of risks and lower costs involved in this type of platform. This paper has provided a critical review of the literature surrounding the applications of UAVs in architecture and urbanism identifying hot topics and weak points that needs to be developed. For this purpose, a scientometric analysis of a base of 235 academic articles was carried out, from which the appropriate structure was obtained to perform a bibliometric analysis afterwards. This research has demonstrated the feasibility of conducting scientific mapping using the bibliographic database ScopusTM and the scientometric software VOSviewerTM in a large body of literature to provide interesting information and identify important trends. The scientometric analysis carried out prior to the literature review allowed for the analysis of factors such as the most prolific authors, countries and documents in this area of knowledge. After carrying out several co-authoring, citation and bibliographic coupling analyses of each unit of analysis, different results were obtained based on the number \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Field of Application** & **Common UAV Payload** & **Application of UAV** & **References in Text** \\ \hline \multirow{6}{*}{**Green cluster:**************} & GPS-RTK module for geo-referencing images, camera gimbal, vision stereo cameras, RGB-D digital cameras, laser scanning sensors (LiDAR) & 3D Terrain digital reconstruction & [1, 4, 52, 53, 57] \\ \cline{2-4}  & GPS-RTK module for geo-referencing images, camera gimbal, vision stereo cameras, RGB-D digital cameras, laser scanning sensors (LiDAR) & 3D Cultural heritage modelling & [54, 88, 89, 90, 91] \\ \hline \multirow{6}{*}{**Red cluster:**********} & GPS, camera gimbal, RGB digital cameras, video-based cameras, laser scanning sensors (LiDAR) & Construction site monitoring in combination with Building Information Model (BIM) & [12, 46, 60, 63] \\ \cline{2-4}  & & Safety on construction & [64, 65] \\ \hline \multirow{6}{*}{**Blue cluster:********} & GPS, camera gimbal, RGB digital cameras, laser scanning sensors (LiDAR) & Building damage mapping & [43, 44, 67, 68, 69, 77] \\ \cline{2-4}  & Urban damage in emergency situations & [66, 83, 84, 85, 86] \\ \hline \multirow{6}{*}{**Yellow cluster:**********} & GPS, camera gimbal, RGB digital cameras, thermal imaging infrared cameras & Building energy inspection & [99, 103, 104, 105, 106, 120] \\ \cline{2-4}  & & Photovoltaic panels inspection & [107, 108] \\ \hline \multirow{6}{*}{**Orange cluster:********} & GPS, camera gimbal, RGB digital cameras, video-based cameras, laser scanning sensors (LiDAR), thermal imaging infrared cameras & 3D City digital reconstruction & [95, 96] \\ \cline{2-4}  & Urban thermal monitoring & [111, 112, 113, 114, 115, 116, 117, 121] \\ \cline{2-4}  & Urban energy system inspection & [110] \\ \cline{2-4}  & Air quality control & [122, 123, 124] \\ \cline{2-4}  & Smart city & [6, 50, 125, 126, 127] \\ \cline{2-4}  & Cadastral mapping & [92] \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Summary of main UAV applications and common UAV payload by cluster. of documents and the number of citations. For example, authors with more published documents do not accumulate more citations and vice versa. However, a relationship was observed between the number of citations and the average year of publication. The most cited papers were published in very early stages, making them a source of guidance and reference for other researchers. European countries proved to be the pioneers in researching the applications of UAVs in architecture and urbanism due to their high number of citations, although other Asian and American countries have shown greater productivity and exceeded their numbers in recent years.