# Real-Time Object Detection Based on UAV Remote Sensing: A Systematic Literature Review
## 4 Results
### Application Scenarios and Tasks of Real-Time Object Detection  
As UAV usability expands across diverse applications, the research focus has shifted towards real-time object detection using UAV remote sensing. This literature review encompasses the scope of real-time object detection scenarios, targets, and task categorizations, as depicted in Figure 5.  
We have summarized the seven major scenarios of UAV real-time detection. Figure 5 visually illustrates the specifics of detection targets and tasks. Furthermore, papers focused on algorithmic aspects have been categorized under the 'Other' category [33; 37; 38; 39; 40; 41; 42; 43; 44]. Emergency scenarios appear 20 times within the selection, directly correlated with the imperative for real-time responsiveness during critical situations. The traffic diagram depicted in Figure 5 underscores that in emergency scenarios, the primary detected targets encompass humans [45; 46; 47; 48; 49; 50; 51; 52], natural disasters [53; 54; 55; 56; 57], and abnormal crowd events [31; 58], all of which necessitate swift responses to avoid casualties. An additional subset of detection targets comprises vehicles [28; 59] and ships [60], both of which are susceptible to dangerous conditions. In this regard, UAV real-time object detection emerges as a viable solution for addressing these challenges. In particular, providing emergency services during a crisis event is vital for rescue missions [45]. The second prominent application scenario revolves around agriculture, involving a review of seventeen relevant papers. Precision agriculture emphasizes the fast and accurate detection of crop stress, including crop diseases [61; 62; 63], pests [64], and surrounding  
Figure 5: This Sankey diagram of the selected literature illustrates the connectivity among real-time detection scenarios, detection targets, and tasks. Proceeding from left to right, the diagram categorizes and summarizes application scenarios present in the selected literature, the diverse detection targets within varying application contexts, and the tasks executed for each specific target. The width of the flow between nodes signifies the amount of literature pertaining to each node. Fixed-wing UAVs possess immobile wings that rely on forward airspeed for lift generation [98]. Nonetheless, they lack backward movement, hovering, or rotation capabilities [99] and necessitate demanding take-off and landing conditions [21]. Our review distinctly highlights that a mere two studies harnessed fixed-wing UAVs for real-time object detection applications: emergencies [28] and agriculture [76]. In contrast, the domain of real-time detection applications is notably governed by multi-rotor UAVs [85; 93; 94], which is primarily attributed to their economical manufacturing advantages [99]. An overwhelming majority of investigations gravitate toward this classification. Multi-rotor UAVs ingeniously employ multiple rotors for lift generation [98], facilitating attributes such as vertical landing, agile maneuvers, and swift takeoffs. Furthermore, due to the inherent hovering capability of multi-rotor UAVs, they are especially well-suited for aerial photography [4]. Fixed-wing UAVs require sensors equipped with fast shutters to counteract motion blur resulting from the absence of forward-motion compensation. The third UAV category encompasses hybrid-wing UAVs, merging fixed-wing and multi-rotor technologies. These hybrids utilize multi-rotors for vertical take-off and landing, while the fixed-wing component serves extended linear coverage. Our review reveals infrequent utilization of hybrid-wing UAVs; they are observed solely in one real-time traffic scenario for asset detection [80]. The sensors of remote sensing employed in real-time object detection encompass RGB[53; 64; 71; 73], multi-spectral [74], hyperspectral [96], thermal infrared [48; 84], and the fusion of multiple sensors [50; 60]. As evidenced in Figure 5(b), the RGB sensor stands as the predominant sensor type for real-time object detection tasks within UAV-based remote sensing.