An Information Flow Switching-Based Despeckling Network Under Real Dual-Polarization SAR Conditions

Polarimetric synthetic aperture radar (SAR) can capture rich polarization information of targets, but it is inherently affected by speckle. Learning-based methods have demonstrated superior speckle suppression potential. Most existing methods use optical images to simulate SAR noise for model training. Because of the significant differences in the imaging mechanisms between optical and SAR images, the data characteristics of these two types differ significantly, resulting in poor generalization performance. To this end, an Information Flow Switching-based Despeckling Network (IFSDN) is proposed for dual-polarization SAR image. By using the long time series data, the first dual-polarization SAR real dataset is constructed. The hybrid feature extraction module (HFEM) is constructed to independently extract and integrate features from both the diagonal and nondiagonal elements of the covariance matrix. Additionally, the multihierarchical residual attention despeckling (MRAD) module performs despeckling on feature maps from low to high levels. On this basis, the information flow switching mechanism facilitates the interaction of dominant features before and after despeckling, injecting spatial details into the despeckled results, reducing speckle noise, and preserving polarization information. By considering temporal changes, an adaptive joint loss function is, furthermore, constructed to guide the network training process, achieving high-fidelity despeckling while maintaining spatial-polarization information. Experiments show that IFSDN outperforms existing state-of-the-art methods in the speckle removal task for real dual-polarization SAR images, which can effectively preserve spatial and polarization information while suppressing speckles. Besides, generalization experiments demonstrate that the proposed model can be effectively applied to diverse datasets across various climate zones, showcasing its strong robustness.