A Combinatorial Registration Method for Forward-Looking Sonar Image

In this article, we present a novel and robust registration method for autonomous underwater vehicles (AUV) using the forward-looking sonar (FLS). Due to the sparsity and repeatability of the underwater environment, and the loss of elevation angle, the FLS is difficult to consistently provide reliable information. The feature extraction and matching are the main difficulties encountered in registrations. This motivates us to propose a method to deal with various underwater environments and provide reliable information to improve the robustness and accuracy of the registration. First, the sonar images are preprocessed to highlight the region of interest and transformed. Next, a sonar image sequence is used for preliminary registration. Last, a combinatorial method including a feature-based region selection and a region-based registration is proposed. The validation is based on datasets and real-world experiments. Comparison studies verify the effectiveness of the proposed method.