Shoujun Li

A New Method of Automatic SVP Optimization Based on MOV Algorithm

We applied the maximum offset of sound velocity algorithm to sound velocity profile streamlining and optimization to overcome multibeam survey and data-processing efficiency problems. The impact of sound velocity profile streamlining on sounding data accuracy is evaluated. By automatically optimizing the threshold, the reduction rate of sound velocity profile data can reach over 90% and the standard deviation percentage error of sounding data can be controlled to within 0.1%. The optimized sound velocity profile data improved the operational efficiency of the multi-beam survey and data postprocessing by 3.4 times, indicating that this algorithm has practical value for engineering applications.

The morphotectonics and its evolutionary dynamics of the central Southwest Indian Ridge (49° to 51°E)

The morphotectonic features and their evolution of the central Southwest Indian Ridge (SWIR) are discussed on the base of the high-resolution full-coverage bathymetric data on the ridge between 49°-51°E. A comparative analysis of the topographic features of the axial and flank area indicates that the axial topography is alternated by the ridge and trough with en echelon pattern and evolved under a spatial-temporal migration especially in 49°–50.17°E. It is probably due to the undulation at the top of the mantle asthenosphere, which is propagating with the mantle flow. From 50.17° to 50.7°E, is a topographical high terrain with a crust much thicker than the global average of the oceanic crust thickness. Its origin should be independent of the spreading mechanism of ultra-slow spreading ridges. The large numbers of volcanoes in this area indicate robust magmatic activity and may be related to the Crozet hot spot according to RMBA (residual mantle Bouguer anomaly). The different geomorphological feature between the north and south flanks of the ridge indicates an asymmetric spreading, and leading to the development of the OCC (oceanic core complex). The tectonic activity of the south frank is stronger than the north and is favorable to develop the OCC. The first found active hydrothermal vent in the SWIR at 37°47′S, 49°39′E is thought to be associated with the detachment fault related to the OCC.

Underwater Target Detection and 3D Reconstruction System Based on Binocular Vision

To better solve the problem of target detection in marine environment and to deal with the difficulty of 3D reconstruction of underwater target, a binocular vision-based underwater target detection and 3D reconstruction system is proposed in this paper. Two optical sensors are used as the vision of the system. Firstly, denoising and color restoration are performed on the image sequence acquired by the vision of the system and the underwater target is segmented and extracted according to the image saliency using the super-pixel segmentation method. Secondly, aiming to reduce mismatch, we improve the semi-global stereo matching method by strictly constraining the matching in the valid target area and then optimizing the basic disparity map within each super-pixel area using the least squares fitting interpolation method. Finally, based on the optimized disparity map, triangulation principle is used to calculate the three-dimensional data of the target and the 3D structure and color information of the target can be given by MeshLab. The experimental results show that for a specific size underwater target, the system can achieve higher measurement accuracy and better 3D reconstruction effect within a suitable distance.

A new method to identify the foot of continental slope based on an integrated profile analysis

A new method is proposed to identify automatically the foot of the continental slope (FOS) based on the integrated analysis of topographic profiles. Based on the extremum points of the second derivative and the Douglas–Peucker algorithm, it simplifies the topographic profiles, then calculates the second derivative of the original profiles and the D–P profiles. Seven steps are proposed to simplify the original profiles. Meanwhile, multiple identification methods are proposed to determine the FOS points, including gradient, water depth and second derivative values of data points, as well as the concave and convex, continuity and segmentation of the topographic profiles. This method can comprehensively and intelligently analyze the topographic profiles and their derived slopes, second derivatives and D–P profiles, based on which, it is capable to analyze the essential properties of every single data point in the profile. Furthermore, it is proposed to remove the concave points of the curve and in addition, to implement six FOS judgment criteria.

Methods and procedures to determine the outer limits of the continental shelf beyond 200 nautical miles

This paper establishes techniques and methods to determine a variety of boundaries associated with 200 nautical miles beyond the continental shelf. The methods, based on topography, slope and second-derivative profile integrated analysis, are now able to identify automatically the foot of the continental slope (FOS). By analyzing the sedimentary profile, the points of 1% sediment thickness are recognized. Through the intersection, cut, deletion and mergence calculation of the extrapolated data set of fixed-point series, the method succeeds in generating automatically the extrapolated boundaries, including the FOS+60 M line, the 350 M line, and the 2 500 m+100 M line. In addition, based on the automatic analysis of the topographic profile, it can be applied to determine rapidly the points of maximum water depth. Taking the northern Okinawa Trough (OT) as an example, these methods are used to calculate and examine the boundaries included in the Submission by the People’s Republic of China Concerning the Outer Limits of the Continental Shelf beyond 200 Nautical miles in Part of the East China Sea (ECS); the boundaries thus derived have a solid scientific and rational basis.