Unlocking Pseudolabel Potential and Alignment for Unpaired Cross-Modality Adaptation in Remote Sensing Image Segmentation

With the growth of multisource sensor technology, multimodal learning has become pivotal in remote sensing (RS) image segmentation. Despite its potential, current methods face challenges in acquiring large-scale paired samples. When annotated optical images are available, but synthetic aperture radar (SAR) images lack annotations, learning discriminative features for SAR images from optical images becomes difficult. Unsupervised domain adaptation (UDA) offers a potential solution to this challenge, which we refer to as unpaired cross-modality UDA. In this article, we propose unlocking pseudolabel potential and alignment (ULPA) for unpaired cross-modality adaptation in RS image segmentation, a novel one-stage adaptation framework designed to enhance cross-modality knowledge transfer. Our approach employs a prototypical multidomain alignment (PMDA) strategy, which reduces the modality gap through contrastive learning between features and prototypes of identical classes across different modalities. In addition, we introduce the unreliable-sample-guided feature contrast (UFC) loss to address the underutilization of unreliable pixels during training. This strategy separates reliable and unreliable pixels based on prediction confidence, assigning unreliable pixels to a category-wise queue of negative samples, thus ensuring all candidate pixels contribute to the training process. Extensive experiments show that the integration of PMDA and UFC loss can lead to more effective cross-modality domain alignment and substantially boost the model's generalization capability.