Self-supervised Multisensor Change Detection

Multimodal and multisensor data analysis is a long-standing goal in machine learning research. In this paper we revisit multisensor analysis in context of self-supervised change detection in bi-temporal satellite images. Most change detection methods assume that pre-change and post-change images are acquired by the same sensor. However, in many real-life scenarios, e.g., natural disaster, it is more practical to use the latest available images before and after the occurrence of incidence, which may be acquired using different sensors. In particular, we are interested in the combination of the images acquired by optical and Synthetic Aperture Radar (SAR) sensors. While optical images are like the natural images dealt in computer vision, SAR images appear vastly different even when capturing the same scene. Adding to this, change detection methods are often constrained to use only target image-pair, no labeled data, and no additional unlabeled data. Such constraints limit the scope of traditional supervised machine learning and unsupervised generative approaches for multi-sensor change detection. Recent rapid development of self-supervised learning methods has shown that some of them can even work with only few images. Motivated by this, in this work we propose a method for multi-sensor change detection using only the unlabeled target bi-temporal images that are used for training a network in self-supervised fashion by using deep clustering and contrastive learning. The trained network is evaluated on multi-modal satellite data showing change and the benefits of our self-supervised approach are demonstrated.