Comparative Analysis of Two Angle Normalization Approaches for SAR Backscatter: Simulation and Satellite Observation-Based Evaluation in Soil Moisture Retrieval

Local incidence angle (LIA) normalization is an important method to improve the accuracy of active microwave remote sensing-based soil moisture retrieval in mountainous areas. In this study, the differences between two commonly used synthetic aperture radar (SAR) backscatter LIA normalization methods, cosine-based and liner-based, were compared using simulated and Sentinel-1 SAR data. The influence of two backscatter normalization methods on soil moisture retrieval in the dual-temporal dual-channel (DTDC) algorithm is analyzed. The results show that the difference between the normalized backscatter by the two methods is less than 0.3 dB in most cases. Despite the simplicity of the methods, both angle normalization techniques can rectify variations in backscattering induced by the LIA effect and improve the accuracy of soil moisture retrieval.