Simulation and Validation of Real-Time UAV-Based GNSS-R Altimetry Across Diverse Landforms

Accurate measurement of land surface elevation is essential for applications such as terrain mapping, environmental monitoring, and ecological assessment. However, conventional spaceborne and ground-based techniques face challenges in achieving both high accuracy and real-time performance. To address these limitations, this work proposes a BeiDou-based UAV GNSS-R altimetry system capable of delivering real-time elevation estimates at a 5 Hz sampling rate. The system integrates a compact, low-power receiver with a real-time correction framework, thereby eliminating the need for post-processing. Performance was evaluated through three experiments involving variable flight altitudes (10–110 m), low signal-to-noise ratio (SNR) conditions, and complex terrain scenarios (1300–1550 m). The system achieved an accuracy of 1.5 meters under both low-altitude and low-SNR conditions, and approximately 1.854 meters in complex terrain scenarios. These consistent results across diverse conditions indicate the system's robustness and generalizability. To support realistic signal modeling, a 12.5 m resolution ALOS digital elevation model and the GSS-9000 simulator were employed. Additionally, terrain undulation, vegetation characteristics, and surface roughness were incorporated into the modeling process. The results demonstrate that the system has strong potential for practical use in terrain mapping and disaster monitoring applications.