Abstract
The multibeam echo sounders (MBES) can acquire accurate positional but low-resolution seabed terrain and images, whereas side scan sonars (SSS) can only acquire inaccurate positional but high-resolution seabed images. In this study, a new method for superimposing corrected-positional SSS images on multibeam bathymetric terrain is proposed to obtain high-resolution and accurate-positional seabed topography using traditional MBES and SSS. Three steps, including the normalization by the z-score, sediment classification by the k-means++ algorithm, and denoising processing using morphological operations, are processed for both MBES and SSS images to obtain the corresponding sediment images. Next, a segmented matching method is given based on the common sediment distributions and features of MBES and SSS sediment images. The two kinds of sediment images are matched segmentally using the speeded up robust features algorithm and random sample consensus algorithm. Then, the positions of SSS images are corrected segmentally using thin plate splines based on matching points. Finally, the corrected SSS image is superimposed on MBES bathymetric terrain, based on positional relationship. The proposed method was verified through experiments, and high image resolution and high position accuracy seabed topography were obtained. Moreover, the performances of the method are discussed, and some conclusions are drawn according to the experiments and discussions.
Highlights
Multibeam echo sounders (MBES) and side scan sonars (SSS) have wide applications in remote sensing of seabed topography or morphology [1,2,3,4,5]
Inaccurate positional problem, which limits the applications of SSS image, can be solved, and high-resolution and accurate positional seabed topography is obtained with the results of traditional MBES and SSS
(4) Seabed textures: Similar to seabed targets, seabed textures, such as sand ripple, which appear in MBES and SSS images, and their sediment images can be used as the common features in the matching [11,20,21]
Summary
Multibeam echo sounders (MBES) and side scan sonars (SSS) have wide applications in remote sensing of seabed topography or morphology [1,2,3,4,5]. The complementarity of SSS and MBES data implies another method to obtain high-resolution and accurate positional seabed topography through the superimposition of two-dimensional (2D) SSS images on three-dimensional (3D) MBES terrain. Modern MBESs can record time-sequence backscatter strength (BS) data (i.e., snippet) and resolutions of snippet images are higher than those of the images formed by traditional average beam BS Both MBES and SSS images are formed using BSs, and can reflect similar seabed textures, targets on the seabed, and distributions and variations of seabed sediments. This study proposes a new method for the superimposition of SSS images and MBES terrain based on the matching of the two types of sonar images. Inaccurate positional problem, which limits the applications of SSS image, can be solved, and high-resolution and accurate positional seabed topography is obtained with the results of traditional MBES and SSS.
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