LM-Net: A Lightweight Matching Network for Remote Sensing Image Matching and Registration

Deep feature learning methods have shown significant advantages over handcrafted feature-based methods in remote sensing image matching and registration. Existing deep learning methods usually introduce complex modules into the deep convolutional network for more robust feature learning. However, they usually require high computation and memory resources for the computing device and have expensive time costs for image registration. As a basic image-processing task, it is crucial to build a lightweight matching network (LM-Net) for fast and accurate image matching and registration. Unfortunately, the image-matching performance will decrease significantly when we directly compress the deep model to a lightweight one. This article proposes an LM-Net based on the knowledge distillation (KD) learning framework for remote sensing image matching and registration. We first build an LM-Net with three convolutional layers. Then, this article proposes an effective KD approach for network optimization, which transfers the effective knowledge from the deep matching network to LM-Net to improve image-matching performances. Specifically, this article considers the useful information in the instance samples and the relation information between samples. It designs the feature and feature relation distillation learning for LM-Net training. Extensive experimental results and analysis have shown the effectiveness and advantages of the proposed LM-Net. LM-Net can reduce the number of parameters and computational complexity of the matching network. Meanwhile, LM-Net can significantly decrease the time cost and achieve results comparable to those of the deep model. It reduces the average image registration time by 42% on remote sensing image matching and registration. Additionally, LM-Net generalizes well on other multimodal remote sensing images.