Cost-Sensitive Latent Space Learning for Imbalanced PolSAR Image Classification

Land cover classification is an important application for polarimetric synthetic aperture radar (PolSAR) image interpretation. The classification performance of a promising parametric feature and classifier learning-based algorithm is limited when the amounts of pixels from different classes vary greatly. PolSAR data from minority classes is difficult to recognize correctly owing to a strong learning bias toward the majority classes, resulting in under-performing features for minority classes. To address this issue, a cost-sensitive latent space learning network based on the feature and classifier learning framework is proposed to reduce the learning bias for supporting the classification of imbalanced data in PolSAR images. First, a new cost-sensitive method is developed by adaptively computing the cost coefficient from predicted labels in the optimization process. Thus, the imbalanced distribution of PolSAR data can be obtained for both the labeled and unlabeled pixels rather than a predefined misclassifying matrix for labeled pixels. Second, latent space learning is used as an auxiliary task to assist the main task of classifier learning. By weighting the distance between the learned feature and the basis of the latent space with a different cost-sensitive coefficient, pixels in minority and majority classes are promoted to be more separable. Thus, the strong bias to majority classes is reduced from both the feature learning and classification process. Finally, the proposed method is studied through experiments on three different PolSAR images with several existing state-of-the-art methods. The experiments validate the effectiveness of the proposed method for balanced and imbalanced PolSAR land cover classification.