## 3 Results
### Documents  
In this section, articles from the database were analysed according to the citation and bibliographic coupling networks. These networks make possible a better understanding of the theoretical foundations of the most cited documents. The two analyses were performed using the documents unit of the downloaded data to create a map by selecting a threshold with a minimum of 10 citations per document, which led to the 113 most cited articles in the database. Each article is represented by a node whose size depends on the number of citations and the colour depends on the year of publication (Figure 6). The most cited articles are shown in Table 4 along with more information from the analyses such as the field of application of the UAVs in the research, the average year of publication, the link strength and the total link strength. The link strength and the total link strength are calculated on the basis of the connections between the 113 documents. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Source Journal** & **Area** & **H Index** & **Publications** & **Citations** & **Year** & **Citation 1** & **Bibliographic Coupling 1** \\ \hline Automation in construction & Building and construction & 107 & 37 & 1180 & 2017 & 20 & 443 \\ \hline Remote sensing & Earth and planetary sciences & 99 & 16 & 205 & 2018 & 13 & 390 \\ \hline IEEE Access & Engineering & 86 & 9 & 193 & 2019 & 6 & 112 \\ \hline ISPRS International journal of geo-information & Earth and planetary sciences & 35 & 6 & 63 & 2018 & 12 & 163 \\ \hline Sensors & Engineering & 153 & 5 & 47 & 2018 & 1 & 63 \\ \hline Computer-aided civil and infrastructure engineering & Computer science & 76 & 4 & 109 & 2019 & 2 & 107 \\ \hline Renewable and sustainable energy & Renewable energy & 258 & 4 & 102 & 2017 & 2 & 38 \\ \hline Journal of archaeological science: reports & Arts and humanities & 21 & 4 & 96 & 2017 & 5 & 66 \\ \hline Journal of intelligent and robotic systems: theory and applications & Computer science & 69 & 4 & 95 & 2015 & 0 & 24 \\ \hline Sustainable cities and society & Renewable energy & 43 & 4 & 35 & 2019 & 0 & 19 \\ \hline Energies & Engineering & 78 & 4 & 22 & 2018 & 0 & 15 \\ \hline Natural hazards and earth system sciences & Earth and planetary sciences & 90 & 3 & 108 & 2017 & 12 & 77 \\ \hline Building and environment & Building and construction & 138 & 3 & 71 & 2018 & 3 & 70 \\ \hline IEEE Communications magazine & Engineering & 231 & 2 & 252 & 2017 & 6 & 12 \\ \hline \hline \end{tabular} \({}^{1}\) Total Link Strength.  
\end{table} 
Table 3: Summary of network analyses. Source journals with the highest number of publications and citations. According to the number of citations, the most frequently cited documents are: Mobile 3D mapping for surveying earthwork projects using an Unmanned Aerial Vehicle (UAV) system by [PERSON]. (356 citations) [1], followed by UAV-Enabled intelligent transportation systems for the smart city: Applications and challenges by [PERSON]. (219) [50], Visual monitoring of civil infrastructure systems via camera-equipped Unmanned Aerial Vehicles (UAVs): a review of related works by [PERSON]. (172) [12], A review of rotorcraft Unmanned Aerial Vehicle (UAV) developments and applications in civil engineering by [PERSON]. (128) [22] and UAV-based urban structural damage assessment using object-based image analysis and semantic reasoning by [PERSON]. [41] with 101 citations (Table 4). They are dated between 2014 and 2017, becoming the pioneering researches about the use of UAVs in architecture and urbanism. Figure 6: Documents network analysis. (**A**) Citation network, (**B**) Bibliographic coupling network.