## 3 Results  
### Temporal Evolution  
The annual publication volume of literature serves as a key indicator for evaluating the level of activity and developmental stage of a research field. UAV-RS technology has undergone a long evolutionary process, transitioning from exclusive military use to widespread civilian adoption. Its scientific evolution vividly reflects the technological advancements and integration across multiple domains, including aerospace, sensor technology, information processing, and artificial intelligence. This evolution is not only evident in the performance enhancement of UAV platforms themselves, but also in innovations in sensor technology, the increasing intelligence of data processing and analysis methods, and the continuous expansion and deepening of application areas. In its early stages, UAV-RS was primarily used for military reconnaissance, leveraging its advantages such as pilotless operation and the ability to access high-risk areas, thereby playing a vital role in intelligence gathering. Entering the 21 st century, with the maturation of technology and a significant reduction in costs, UAV-RS began to penetrate civilian sectors, demonstrating enormous potential in industries such as agriculture, forestry, environmental monitoring, disaster response, and surveying and mapping. In particular, the emergence of lightweight and compact UAVs has significantly lowered the threshold for UAV-RS, enabling more enterprises and individuals to use this technology for data collection and analysis. For instance, the release of the DJI Phantom 1 in 2012 by China's DJI company marked a milestone. With its user-friendly design and relatively low cost, it quickly captured the consumer market and facilitated the use of UAV-RS in crowdsourced geographic data acquisition [43]. This shift signifies the transition of UAV-RS from a specialized, high-cost military application to a more democratized, low-cost civilian service. Its scientific evolution path thus exhibits distinctive characteristics of multi-technology integration and cross-sectoral penetration. The annual publication trend is shown in Figure 2.  
(1) Initial Stage (Before 2000): During this period, the number of UAV-RS-related publications was extremely limited, with annual outputs generally in the single digits. Research was primarily driven by early explorations in military and aerospace engineering contexts, and both the application scenarios and technical capabilities of UAVs remained in an experimental phase. (2) Slow Growth Stage (2000-2014): With the proliferation of GPS navigation, inertial measurement units (IMUs), and lightweight flight platforms, UAVs gradually began to enter scientific and commercial domains. Around 2010, the annual number of publications surpassed 20, reaching 84 by 2014. Representative studies during this period were largely focused on agricultural remote sensing, disaster monitoring, and photogrammetry applications. Although recognition of UAV-RS steadily increased, progress remained relatively slow due to limitations in cost, platform stability, and data processing capacity. (3) Rapid Development Stage (2015-2019): After 2015, civilian UAV technologies advanced rapidly. In particular, commercial aerial platforms--led by companies like DJI in China--significantly lowered technical barriers and improved operability, offering low-cost and high-quality data acquisition solutions for researchers. Annual publication volume exceeded 100 papers for the first time in 2016 and surged to 470 by 2019, with an average annual growth rate of over 30%. During this phase, UAV-RS technologies achieved widespread deployment in agriculture, forestry, ecology, hydrology, and more. Research themes shifted from \"whether UAVs can be used\" to \"how to use them effectively.\"  
(4) High-Activity Stage (2020-Present): Since 2020, UAV-RS has maintained a high-growth momentum, with annual publications consistently exceeding 600.