# Space-Ground Remote Sensor Network for Monitoring Suspended Sediments in the Yellow River Basin
## 4 Discussion  
### Strengths and Limitations of Space-Air-Ground Integrated Remote Sensor Network  
In response to the diversity of water and sediment monitoring content and the inadequacy of traditional monitoring methods, the integrated remote sensing monitoring network supported by advanced ground observation technology can provide efficient monitoring methods for water and sediment in the Yellow River. Its main technologies include satellite remote sensing, drone remote sensing, and ground-based wireless automatic monitoring networks, with the following main advantages and disadvantages.  
(1) Satellite remote sensing: Virtual high-resolution optical satellite constellations such as HJ, GF, Landsat, Sentinel-2, and PRISMA from China, the United States, and the European Union can achieve high-frequency observations multiple times per day, providing synchronous water and sediment topographic information over a large spatial range and first-hand information for disaster areas with transportation difficulties [34; 36; 38]. Its  
Figure 9: The SSC during the water and sediment regulation period of the Yellow River before the flood in 2023 (from 21 June 2023 to 11 July 2023). (**–g**), the SSC at Xiaolangdi reservoir and downstream areas; (**–k**) the SSC at the Yellow River estuary.  
shortcomings include the inability to work at night; in cloudy and rainy weather conditions, cloud cover over the target area renders optical remote sensing satellite monitoring ineffective. Microwave can work in all weather conditions and can be used to identify water bodies but cannot calculate sediment concentration within them.  
(2) Drone remote sensing: With flexible maneuverability, route-planning adjustments, and rapid response capabilities [42], drones and networked observations can provide ultra-high-resolution spatial information on water and sediment disasters; high-endurance drones can provide water and sediment information over a large spatial range. However, drones cannot provide water and sediment information at night; the accuracy of drone remote sensing is greatly affected by cloudy and rainy weather, and corresponding inversion algorithms need further development. Additionally, the observation area and flight paths of drones are subject to local airspace regulations. The flight altitude and speed must be adjusted based on the specific conditions of the observation site to ensure the safety of both personnel and the drone.  
(3) Ground-based in situ hyperspectral sensing network: Deploying a wireless automatic monitoring network at critical water body sections can provide real-time water and sediment information during the day, enabling real-time field data for the routine monitoring of water and sediment and disaster warning. Conventional contact automatic monitoring stations suffer from high losses, instability, and maintenance difficulties. Automatic in situ hyperspectral sensors based on near-ground remote sensing principles have the advantages of non-contact, environmental friendliness, and low maintenance costs, but they are easily affected by changes in lighting conditions and cannot operate at night [28; 29]. Further research is needed on corresponding technologies, including active light source monitoring for night operations.