阅读说明：本技术 一种基于声速剖面反演的多波束海底地形校正方法 (Multi-beam submarine topography correction method based on sound velocity profile inversion ) 是由 徐天河 刘杨范 王君婷 江楠 于 2021-06-30 设计创作，主要内容包括：本发明涉及一种海底地形校正方法,具体是一种基于声速剖面反演的多波束海底地形校正方法,基于相邻条带重叠区域多个ping对应波束的测深一致性,构建目标函数；确定初始温度；设置初始解、EOF系数的取值范围及邻域函数；根据前几个特征向量和实测的SVP计算得到EOF时间系数的取值范围,邻域函数应使产生的候选解遍布解空间；利用目标函数的加权平均值判断内循环是否达到“热平衡状态”；构建温度冷却函数；确定外循环终止准则；搜寻最优解；最终校正海底畸变地形；该方法首先利用EOF对SVP进行分解,然后,基于由相邻条带重叠区域的多组ping对应波束的测深一致性构造的代价函数,最后,根据最优时间系数反演SVP,并利用反演的SVP对海底地形畸变进行校正。(The invention relates to a submarine topography correction method, in particular to a multi-beam submarine topography correction method based on sound velocity profile inversion, which is characterized in that a target function is constructed based on the sounding consistency of a plurality of ping corresponding beams in the overlapping area of adjacent strips; determining an initial temperature; setting an initial solution, a value range of an EOF coefficient and a neighborhood function; calculating to obtain the value range of the EOF time coefficient according to the first characteristic vectors and the actually measured SVP, wherein the neighborhood function enables the generated candidate solution to be distributed in a solution space; judging whether the inner circulation reaches a thermal equilibrium state or not by using the weighted average value of the target function; constructing a temperature cooling function; determining an outer loop termination criterion; searching an optimal solution; finally correcting the distorted submarine topography; according to the method, firstly, the SVP is decomposed by using the EOF, then, based on a cost function constructed by the sounding consistency of a plurality of groups of ping corresponding wave beams in an overlapping area of adjacent strips, finally, the SVP is inverted according to an optimal time coefficient, and the inverted SVP is used for correcting the distortion of the submarine topography.)

1. A multi-beam submarine topography correction method based on sound velocity profile inversion is characterized by comprising the following steps:

step one, constructing an objective function;

based on the sounding consistency of multiple ping corresponding beams in the overlapping area of adjacent strips, an objective function is constructed:

determining an initial temperature;

setting an initial solution, a value range of an EOF coefficient and a neighborhood function;

calculating to obtain the value range of the EOF time coefficient according to the first characteristic vectors and the actually measured SVP, wherein the neighborhood function is to enable the generated candidate solution alpha to be distributed in a solution space, and the following neighborhood functions are given:

step four, setting an internal circulation termination criterion;

whether the internal circulation reaches a thermal equilibrium state is judged by utilizing the weighted average value of the target function, and the weighted average value formula of the target function is as follows:

step five, determining a temperature cooling function;

a temperature cooling function was constructed as follows:

T_k+1＝βT_k,β∈[0.5,0.99]；

step six, determining an outer loop termination criterion;

the external circulation termination condition is that no acceptable candidate solution exists at a plurality of continuous temperatures;

step seven, searching an optimal solution;

setting a memory function, storing the minimum value of the target function at each temperature, and finding out the minimum value of the global target function;

step eight, correcting distorted submarine topography;

and (4) performing multi-beam data processing by using the inverted SVP, and correcting the distorted submarine topography.

2. The multi-beam seafloor terrain correction method based on sound velocity profile inversion of claim 1, wherein in the first step, when the objective function reaches the minimum, the optimal EOF time coefficient is obtained, and then the inversion SVP is obtained.

3. The multi-beam seafloor terrain correction method based on sound velocity profile inversion of claim 1, wherein in the fourth step, whenSeveral consecutive steps remained stable indicating that the internal circulation reached a "thermal equilibrium state".

4. The multi-beam seafloor terrain correction method based on sound velocity profile inversion of claim 1, wherein in the fourth step, when the thermal equilibrium state is difficult to achieve at high temperature, the maximum iteration number K of the inner loop needs to be set, and the maximum iteration number K can be set by observing the iteration number needed to achieve the thermal equilibrium state at a plurality of temperatures.

5. The multi-beam seafloor terrain correction method based on sound velocity profile inversion of claim 3, wherein in the eighth step, EOF is used for representing SVP, an SVP inversion process is converted into an EOF coefficient optimization process, then SA is used for searching an optimal EOF coefficient to obtain an inverted SVP, and further seafloor distortion terrain is corrected.

Technical Field

The invention relates to a submarine topography correction method, in particular to a multi-beam submarine topography correction method based on sound velocity profile inversion.

Background

SVP is a major factor affecting multibeam sounding, and its representative error causes distortion of the seafloor topography.

Although the existing method can effectively reduce the underwater terrain distortion caused by SVP representation errors. However, various problems exist. And the influence of the sound speed error on the water depth data is weakened in a manual intervention mode. Manual intervention is not only lack of mathematical basis, but also reduces the processing efficiency of multi-beam data. And (3) constructing the sound velocity field of the region by using the existing SVP so as to correct the submarine topography distortion. However, this approach requires more historical SVP and the obtained SVP deviates from the actual SVP, especially in high dynamic environments. And constructing an objective function by using the principle that the 45-degree beam pointing angle is insensitive to SVP errors, and correcting the submarine topography distortion. This method requires accurate knowledge of the ocean surface acoustic velocity and is only applicable to absolutely flat terrain. And constructing a fitness function by taking the terrain distortion degree caused by imperfect multi-beam measurement sound velocity correction as a basis to realize SVP inversion and correct the seabed distortion terrain. The method has low accuracy of correcting the submarine topography and is not suitable for inclined submarine topography.

Disclosure of Invention

The invention aims to provide a multi-beam submarine topography correction method based on sound velocity profile inversion, so as to solve the problems in the background technology.

In order to achieve the purpose, the invention provides the following technical scheme:

a multi-beam submarine topography correction method based on sound velocity profile inversion comprises the following steps:

step one, constructing an objective function;

based on the sounding consistency of multiple ping corresponding beams in the overlapping area of adjacent strips, an objective function is constructed:

determining an initial temperature;

setting an initial solution, a value range of an EOF coefficient and a neighborhood function;

calculating to obtain the value range of the EOF time coefficient according to the first characteristic vectors and the actually measured SVP, wherein the neighborhood function is to enable the generated candidate solution alpha to be distributed in a solution space, and the following neighborhood functions are given:

step four, setting an internal circulation termination criterion;

whether the internal circulation reaches a thermal equilibrium state is judged by utilizing the weighted average value of the target function, and the weighted average value formula of the target function is as follows:

step five, determining a temperature cooling function;

a temperature cooling function was constructed as follows:

T_k+1＝βT_k,β∈[0.5,0.99]；

step six, determining an outer loop termination criterion;

the external circulation termination condition is that no acceptable candidate solution exists at a plurality of continuous temperatures;

step seven, searching an optimal solution;

setting a memory function, storing the minimum value of the target function at each temperature, and finding out the minimum value of the global target function;

step eight, correcting distorted submarine topography;

and (4) performing multi-beam data processing by using the inverted SVP, and correcting the distorted submarine topography.

As a further scheme of the invention: in the first step, when the target function reaches the minimum, the optimal EOF time coefficient is obtained, and then the inversion SVP is obtained.

As a still further scheme of the invention: in the fourth step, when the E (a) keeps stable for a plurality of continuous steps, the internal circulation reaches the heat balance state.

As a still further scheme of the invention: in the fourth step, when the thermal equilibrium state is difficult to reach under the high temperature condition, the maximum iteration number K of the internal loop needs to be set, and the maximum iteration number K can be set by observing the iteration number needed for reaching the thermal equilibrium state under a plurality of temperatures.

As a still further scheme of the invention: in the eighth step, EOF is adopted to represent SVP, an SVP inversion process is converted into an EOF coefficient optimizing process, then the SA is used for searching for the optimal EOF coefficient to obtain the inverted SVP, and further the distorted terrain of the sea bottom is corrected.

Compared with the prior art, the invention has the beneficial effects that: according to the method, firstly, the SVP is decomposed by using the EOF, and the inversion process of the SVP is converted into the time coefficient optimization process of the EOF. Then, based on a cost function constructed by the sounding consistency of multiple groups of ping corresponding beams in the overlapping area of adjacent strips, the SA is adopted to optimize the time coefficient. And finally, inverting the SVP according to the optimal time coefficient, and correcting the distortion of the submarine topography by using the inverted SVP. The method can obviously improve the multi-beam sounding precision and can effectively correct the distortion of various submarine terrains.

Drawings

Fig. 1 is a flow chart of a multi-beam seafloor terrain correction method based on sound velocity profile inversion.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

According to the multi-beam sounding principle, if a certain SVP is given and the propagation time and the beam angle of a certain ping are known, the water depth value of each beam in the ping can be calculated according to a constant gradient sound ray tracking model. If the SVP is the same as the actually measured SVP, the depth measurement result of the corresponding beam of the repeated coverage area of the ping adjacent strip is consistent, otherwise, deviation exists.

Referring to fig. 1, in an embodiment of the present invention, a multi-beam seafloor terrain correction method based on sound velocity profile inversion includes the following steps:

step one, constructing an objective function;

based on the sounding consistency of multiple ping corresponding beams in the overlapping area of adjacent strips, an objective function is constructed:

where n denotes the number of ping groups, m denotes the number of beams in the repeat coverage area of the adjacent band, H_ijIndicating the depth value, H, of the jth beam of the ith group ping_i′_jIs represented by the formula_ijCorresponding water depth value;

in this method, ping selection is very important; selecting ping according to the actually measured sound wave propagation time, wherein the selected ping has larger difference in the corresponding propagation time; in addition, the number of selected pings is positively correlated with the difference between the actually measured sound wave propagation times; however, the number of pings must not be too large, otherwise the efficiency of the experiment is significantly reduced;

determining an initial temperature;

the initial temperature is to enable the receiving probability of each state to be close to 1, the higher the initial temperature is, the higher the probability of obtaining the optimal solution is, but the calculation time is also obviously increased; the initial temperature should balance the accuracy of the results and the experimental efficiency; the initial temperature is determined by adopting an initial temperature method provided by Ben-Ameur W;

the specific calculation method is as follows:

wherein, s is a sample set, t is a sample in s, E_maxtIs the maximum value of the target function in the sample set s, E_mintThe minimum value of an objective function in a sample set is s, and n is the iteration frequency;

setting an initial solution, a value range of an EOF coefficient and a neighborhood function;

calculating to obtain the value range of the EOF time coefficient according to the first characteristic vectors and the actually measured SVP, wherein the neighborhood function is to enable the generated candidate solution alpha to be distributed in a solution space, and the following neighborhood functions are given:

where n is the number of selected first order eigenvectors, β_nIs the nth scale factor;

step four, setting an internal circulation termination criterion;

whether the internal circulation reaches a thermal equilibrium state is judged by utilizing the weighted average value of the target function, and the weighted average value formula of the target function is as follows:

step five, determining a temperature cooling function;

the method for constructing the temperature cooling function by adopting the geometric schedule method comprises the following specific functions:

T_k+1＝βT_k,β∈[0.5,0.99]；

step six, determining an outer loop termination criterion;

the external circulation termination condition is that no acceptable candidate solution exists at a plurality of continuous temperatures;

step seven, searching an optimal solution;

setting a memory function, storing the minimum value of the target function at each temperature, and finding out the minimum value of the global target function;

step eight, correcting distorted submarine topography;

and (4) performing multi-beam data processing by using the inverted SVP, and correcting the distorted submarine topography.

As an embodiment of the present invention, in the first step, when the objective function reaches the minimum, the optimal EOF time coefficient is obtained, and then the inversion SVP is obtained.

In the fourth step, when the successive steps of E (a) are kept stable, it is indicated that the internal circulation reaches the "thermal equilibrium state".

In the fourth step, when the "thermal equilibrium state" is difficult to be reached at high temperature, the maximum number of iterations K of the inner loop needs to be set, and K can be set by observing the number of iterations required to reach the "thermal equilibrium state" at a plurality of temperatures.

In the eighth step, EOF is used to represent SVP, the SVP inversion process is converted into an EOF coefficient optimization process, and then SA is used to search for an optimal EOF coefficient to obtain an inverted SVP, so as to correct distorted submarine topography.

The invention relates to a method for correcting submarine topography distortion by inverting SVP (singular value decomposition) under a complex and changeable marine environment according to the existing historical SVP and combining the existing measured sound wave propagation time, belonging to the inversion category of the marine environment.

The multi-beam sounding technology is an important means for marine surveying and is widely applied to various high-precision marine terrain detection activities. The technology has the characteristics of full coverage, no leakage, high precision, high efficiency and the like. The multi-beam sounding accuracy is influenced by various factors, wherein errors related to SVP (singular value decomposition) including sound velocity errors, sound ray bending errors and the like have large influence on the multi-beam sounding accuracy and are difficult to eliminate. Depending on the propagation characteristics of the acoustic waves under water, in multi-beam sounding, a small error in SVP may result in a large error in water depth measurement, and increases significantly with increasing beam angle. The SVP can be directly measured by an SVP instrument or measured by a thermohaline depth velocimeter to obtain temperature, salinity and pressure data, and then calculated by the existing sound velocity empirical formula. This point-by-point measurement of SVP in the vertical direction is a very time consuming process. In addition, SVP is affected by marine environmental factors such as temperature, salinity and pressure, and changes rapidly with time and space. It is difficult to obtain an SVP accurately in real time. The most recent SVP in the time-space domain is generally adopted for substitution. And because the SVP has time-varying property and space-varying property, the substituted SVP has SVP representative error, and the distortion of the submarine topography can be caused by the SVP to carry out multi-beam sounding.

How to eliminate the distortion of the submarine topography caused by SVP errors is a hot spot problem in multi-beam sounding. Therefore, a method for accurately estimating the water depth through the propagation time measured by the multi-beam bathymeter is provided. By utilizing the overlapping area between the adjacent strips, the water depth measurement error caused by SVP error can be eliminated; in addition, a detection method based on the mixing of long waves and short waves of the underwater topography is also provided, and the method can effectively reduce the distortion of the underwater topography; on the basis of analyzing the influence of the SVP representative error on the underwater topography, the SVP is inverted by using a genetic algorithm, and the underwater topography distortion is corrected; the underwater terrain distortion is corrected by using the principle that the 45-degree beam pointing angle is insensitive to SVP errors, and the underwater terrain calculated by the method is closer to the real underwater terrain. In addition, a new depth sounding refraction correction algorithm based on an average velocity model is provided, the algorithm utilizes a simple linear regression model to estimate the average velocity value and the depth of each grid unit, and the estimation and correction of each depth sounding refraction error can be realized. Based on the redundancy of multi-beam measurement data, the inaccurate SVP-influenced water depth measurement data is corrected by adopting two optimization methods, namely Difference Evolution (DE) and Gauss-Newton (GN). And (3) using the underwater terrain trend line constructed by the central beams of the adjacent strips as prior information, and then correcting the depth sounding error caused by the SVP representative error by using Kalman filtering.

Aiming at the limitations of the existing method, the novel multi-beam underwater terrain distortion correction method based on SVP inversion is provided by combining the multi-beam sounding practice. The method utilizes the detection consistency of a plurality of ping corresponding beams in the overlapping area of adjacent wave bands to invert the SVP. We describe in detail how points are selected to construct the cost function. Considering that the SVP contains a large number of inversion parameters, the method effectively reduces the parameters of the SVP by using EOF. In addition, since the SVP inversion cannot establish an accurate observation model like the underwater sound positioning, the method adopts SA (SA) to optimize the SVP inversion result. Then, SA and EOF parameters are reasonably set, and the SVP is inverted. And finally, correcting the distortion of the underwater terrain by using the inverted SVP. The method can obviously improve the multi-beam sounding precision and effectively correct the distortion of various underwater terrains.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.

Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.