Decouple and weight semi-supervised semantic segmentation of remote sensing images

Semantic understanding of high-resolution remote sensing (RS) images is of great value in Earth observation, however, it heavily depends on numerous pixel-wise manually-labeled data, which is laborious and thereby limits its practical application. Semi-supervised semantic segmentation (SSS) of RS images would be a promising solution, which uses both limited labeled data and dominant unlabeled data to train segmentation models, significantly mitigating the annotation burden. The current mainstream methods of remote sensing semi-supervised semantic segmentation (RS-SSS) utilize the hard or soft pseudo-labels of unlabeled data for model training and achieve excellent performance. Nevertheless, their performance is bottlenecked because of two inherent problems: irreversible wrong pseudo-labels and long-tailed distribution among classes. Aiming at them, we propose a decoupled weighting learning (DWL) framework for RS-SSS in this study, which consists of two novel modules, decoupled learning and ranking weighting, corresponding to the above two problems, respectively. During training, the decoupled learning module separates the predictions of the labeled and unlabeled data to decrease the negative impact of the self-training of the wrongly pseudo-labeled unlabeled data on the supervised training of the labeled data. Furthermore, the ranking weighting module tries to adaptively weight each pseudo-label of the unlabeled data according to its relative confidence ranking in its pseudo-class to alleviate model bias to majority classes as a result of the long-tailed distribution. To verify the effectiveness of the proposed DWL framework, extensive experiments are conducted on three widely- used RS semantic segmentation datasets in the semi-supervised setting. The experimental results demonstrate the superiority of our method to some state-of-the-art SSS methods. Our code will be available at https: //github.com/zhu-xlab/RS-DWL.