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In order to solve the problem that the traditional algorithm for multibeam sounding coordinates ignores the significant impact of the difference in the position of the receiving and transmitting transducer on the deep-water sounding, and the new algorithm takes into account the difference in receiving and transmitting but low efficiency, this paper proposes a high-precision and quick algorithm for multibeam sounding coordinates that considers the propagation surface. First, based on the principle of multibeam measurement and sound ray propagation, a beam propagation surface model is proposed. Second, the beams in the sector are divided into interpolation nodes and points to be interpolated. For the former, a method based on iterative search and interpolation is proposed to avoid the establishment of a complete propagation surface. For the latter, using the interpolated node parameters, a method based on polynomial interpolation is proposed to obtain the single-way time, depression angle and azimuth angle of sound ray. Finally, all beam footprints are calculated. Experiments in shallow and medium-deep water areas show that the accuracy of the cross-line inspection method using this paper method is similar to that of Caris, and is better than the traditional algorithm. Compared with the results of Caris, the depth deviations of the same beam footprint in this paper are 0.35‰ depth and 0.11‰ depth, respectively, and the efficiency in this paper has increased by 8% and 35%, respectively.

Several problems affecting the positioning accuracy of the submarine control network are analyzed. It is considered that the ocean sound velocity changes greatly in a short time and the regularity is not strong. Constructing the sound velocity field is an effective way to weaken the representative error of the sound velocity. The influence of sound velocity on the location is also related to the beam incident angle and depth. The impact is significant and cannot be ignored. In the sound-stable waters, when the incident angles are approximately the same, high accuracy can be achieved by differential positioning with observation distance, otherwise the accuracy is difficult to guarantee. The depth or depth difference provided by the pressure sensor is introduced to improve the vertical solution precision of the control network, but the difference of tide height between two control points should be taken into account.

The patch test method based on decoupling principle to determine MBES (multibeam echo sounders)installation biases often results in complex operation and low accuracy due to theoretical imperfections. Therefore, the overall calibration of the biases is proposed. Firstly, MBES sounding terrain is converted into grayscale image. Then, SIFT(scale-invariant feature transform) is used for matching related terrain images and founding matching point pairs. Finally, the inequality-constrained least square adjustment is used for obtaining the MBES installation biases by the matching point pairs coordinates. The experiment verifies the validation of this method in simplifying the implementation and improving the accuracy of determining these biases.

Traditional CUBE (combined uncertainty bathymetry estimation) filter generally fails to estimate the depth of the water accurately, and produces blur terrain feature in underwater slope riprap area by the multi-beam sounding data filtering with poor ability to remove gross error.Based on the sounding data characteristics of slope riprap area, a secondary CUBE filtering algorithm is proposed. The key idea is to estimate the plane position and depth synchronously, taking account of the transfer model of plane and water depth uncertainty related to terrain gradient. It is based on the second depth estimation model which considers geometric gradient and an optimization method of reference depth to accurately estimate the depth of water in underwater riprap areas and to detect gross error automatically.A set of meaningful experiments are also presented. And the experimental results have shown that the proposed method provides an automatic and accurate elimination for gross error. Specifically, the accuracy of the proposed algorithm is a few times higher than that of the traditional CUBE. It also demonstrates that the proposed filter shows superiority in preserving terrain features with better efficiency and robustness.

An adaptive method based on area difference is proposed. Firstly, the relationship between area difference and sound ray tracking bias is studied and the model is built. Then the simplification method and procedure of SVP are provided, which are based on the constraint of sound ray tracking accuracy. Finally, a deep water experiment is conducted to verify the proposed method and the simplification process is easily achieved without manual intervention. It improves the efficiency of bathymetric data processing remarkably to carry out ray-tracing with simplified sound velocity profile.

To solve the problem that traditional underwater control point absolute positioning is time-consuming and laborious with low vertical precision, itis put forward that an accurate method with constraints of depth while taking waves into account to get absolute coordinate of underwater control point. Firstly, studiesarecarried outon the wave impact.And methods are put forward to determine the elevation difference between underwater points and the absolute elevation with GPS vertical values and the elevation difference. On this basis, methods are put forward, such asthe circle navigationwith depth's constraint to get single point's absolute coordinate, 2D free net adjustment with depth's constraint, integrated constraint adjustment,with accurate elevation difference, and 3D combined adjustment with accurate elevation difference. Finally, the experimental results show that the proposed methods can double the efficiency of traditional methods and improveprecision by one order of magnitude.

This paper briefly reviewed the history of seafloor terrain measuring technology,and then detailed the introduced sonar bathymetry based on vessel,airborne laser bathymetry,integrated measurement for coastal topography and three inversion methods for seafloor terrain.That entirely presents the current situation of stereoscopic,efficient,high-accuracy and high-resolution of seafloor topography acquirement.Finally,combined with the future requirements,this paper summarized the core job and development trend in future seafloor terrain measuring field,which includes developing more portable multi-beam system with ultra-wide coverage,high accuracy and resolution,researching more efficient correction model of sound velocity effects,smoothing of bathymetry data and expression of submarine topography.Meanwhile,automatic ship measurement will be an important task mode.Also airborne laser survey,seafloor topography inversion from sonar image and deep-towing measurement has enormous potential in development.

Due to the problem of the existing image segmentation methods applied in side scan sonar (SSS) image often suffered from low efficiency or low accuracy, this paper proposed a novel SSS image thresholding segmentation method based on neutrosophic set (NS) and quantum-behaved particle swarm optimization (QPSO) algorithm. Firstly, the image gray co-occurrence matrix is constructed in NS domain, the fine texture of SSS image is expressed, and this can improve the accuracy of SSS image segmentation. Then, based on the two-dimensional maximum entropy theory, the optimal two-dimensional segmentation threshold vector is quickly and accurately obtained by QPSO algorithm, and this can improve the efficiency and accuracy of SSS image segmentation. Finally, the accurate and high efficient target segmentation of SSS image with high noises is realized. The effectiveness of the algorithm is verified by segmenting SSS image containing different targets.