## 3 Results
### Analysis of the Global Scientific Collaboration Network: Formation of a Dual-Core Structure
#### 3.2.2 Institutional Cooperation  
Studies reveal that UAV-RS research is highly dependent on a tripartite collaboration mechanism involving universities, research institutes, and government agencies. Among the top 15 institutions by publication volume, the Chinese Academy of Sciences leads with 310 publications, underscoring its dominant role in fundamental theory development and system integration. Institutions such as the Ministry of Agriculture and Rural Affairs of China (148 papers), Chinese Academy of Agricultural Sciences (83 papers), and Nanjing Agricultural University (53 papers) are also highly productive, reflecting China's strategic deployment in agricultural and ecological remote sensing. The U.S. Department of Agriculture (USDA) ranks fourth, with 120 papers, focusing primarily on precision agriculture and forestry management. The University of California system (96 papers) and the Texas A&M University system (54 papers) continue to contribute significantly in remote sensing method innovation and platform integration. A noteworthy and concerning observation is the relatively weak direct collaboration between the two dominant research powers--China and the United States. Despite their enormous academic output, the intensity and quantity of direct collaborative links (represented by line thickness and connection count) are disproportionately low. This fragmented cooperation pattern may hinder the exchange of knowledge and data required to address global challenges such as climate change and food security, and may exacerbate barriers to technology transfer. In addition, European research institutions--including the Helmholtz Association in Germany, the French National Centre for Scientific Research (CNRS), and the Italian National Research Council (CNR)--have made significant academic contributions in LiDAR-based 3D modeling, cultural heritage preservation, and urban remote sensing. Through an in-depth analysis of institutional collaboration and research domains in the field of UAV-RS (Figure 4, Table 2), several key patterns emerge. In China, the Chinese Academy of Sciences (CAS) and Wuhan University are the top two institutions in terms of publication volume. These institutions maintain close partnerships with various domestic organizations and have also established links with U.S. universities and institutions in several European countries. The CAS plays a central role in UAV-RS research, engaging in extensive collaboration both domestically and internationally. Its research domains span foundational theories of UAV-RS, UAV system design and applications, as well as remote sensing data processing and analysis. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Rank**} & **Countries/ Regions** & **Number of Publications** & **Typical Research Areas** \\ \hline \multirow{4}{*}{14} & \multirow{4}{*}{Portugal} & \multirow{4}{*}{89} & Agricultural applications [117], Environmental Monitoring [118], Biodiversity Conservation [119], Urban Management [120], Land Use [121], Disaster Monitoring [122], Forest monitoring [123] \\ \cline{2-4}  & & & Agricultural applications [124], Environmental Monitoring [125], Urban Plan [126], Snow monitoring [127] \\ \hline \multirow{2}{*}{15} & \multirow{2}{*}{Finland} & \multirow{2}{*}{86} & Agricultural applications [128], Environmental Monitoring [129], Archeology [130], Forest monitoring [131] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._Figure 4: Main UAV-RS research institutions and their links. Note: Figure 4 visually illustrates two major research clusters: one centered around the Chinese Academy of Sciences (CAS) and the other around the USDA and the University of California system. While internal linkages within each cluster are dense, strong inter-cluster connections are sparse, providing quantitative support for the diagnosis of a \"strong hubs, weak bridges\" collaboration pattern.