Unsupervised Multimodal Remote Sensing Image Registration via Domain Adaptation

Registration of multimodal remote sensing images with geometric distortions is one of the fundamental applications, but it remains difficult since multimodal remote sensing images have significant differences in both radiometric and geometric features. One of the challenges is the disregarding of modality-specific information, which hinders the model from focusing on the content information of structure and texture due to differences in radiometric features. In this article, an unsupervised content-focused hierarchical alignment network (CHA-Net) is proposed, which is constructed based on the theory of domain adaptation. The kernel idea of CHA-Net is to weaken the style differences among different modal images and achieve nonrigid multimodal remote sensing image registration. CHA-Net is a hierarchical refinement model, where different scales of features are aligned, respectively, by utilizing the field calibration module (FCM) and gradually generating the registration field. To be specific, CHA-Net consists of two structures: the Siamese feature decoupling (SFD) structure and the hierarchical refinement alignment (HRA) structure. The SFD aims at reducing the style differences caused by cross-modal differences and developing a shared-weight Siamese network to map images to content feature space. The HRA enhances the ability of the network by capturing global distortions based on the transformer model. Experiments on public datasets indicate that compared with other methods, CHA-Net performs better when geometric and radiometric distortions appear.