Two-dimensional range error analysis method and system for synthetic aperture sonar imaging model

Abstract

The invention discloses a two-dimensional distance error analysis method and system for a synthetic aperture sonar imaging model, and relates to the technical field of image processing. The two-dimensional distance error analysis method comprises the following steps: determining the distance of a target according to an equidistant sampling method in the distance direction; determining the synthetic aperture length corresponding to the farthest distance target and the coordinates of the target in the azimuth direction according to the beam width in the azimuth direction; calculating the two-way slant range history experienced by the movement of the synthetic aperture sonar receiving and transmitting array elements according to the precise propagation time of the synthetic aperture sonar; calculating the distance error for the approximate slant range history of the imaging model to be evaluated; adding the influence of the array element directivity function on the basis of the distance error; averaging the calculated distance error; and calculating the distance error for all targets and all receiving array elements to obtain the two-dimensional distance error.

Description

Technical Field

[0001] The present invention relates to the technical field of image processing, and in particular to a two-dimensional distance error analysis method and system for a synthetic aperture sonar imaging model. Background Art

[0002] Synthetic aperture sonar technology can obtain underwater acoustic images comparable to optics, which can greatly support the application of underwater engineering such as seabed mapping, underwater archaeology, and small target detection. At present, synthetic aperture sonar uses a linear array composed of one transmitting array element and multiple receiving array elements, which can achieve large mapping swaths and high resolution at the same time, greatly promoting the practical application of synthetic aperture.

[0003] The use of multiple receiving arrays makes synthetic aperture sonar imaging extremely complex, because traditional fast imaging algorithms are mainly for synthetic aperture sonars with co-transmitters and receivers. Therefore, it is necessary to improve traditional imaging algorithms before they can be applied to synthetic aperture sonars with multiple receiving arrays. In order to develop a fast imaging algorithm for multiple receiving arrays, the usual practice is to perform Taylor series approximation on the two-way slant range of the transmitter-receiver split mode. The second-order Taylor series approximation method, the third-order Taylor series approximation method, the fourth-order Taylor series approximation method, the fourth-order Legendre polynomial approximation method, and the fourth-order Chebyshev polynomial approximation method have all been applied to sonar imaging by scholars in the field of synthetic aperture imaging. The approximate processing of these imaging models will bring about approximation errors. Generally speaking, an approximation error exceeding one-eighth of the wavelength will significantly affect the imaging quality. The evaluation conclusion of the imaging model can be drawn only after the phase error compensation function required for each step in the imaging algorithm is derived based on the imaging model, the imaging program is written, the imaging program is verified using simulation data, and the azimuth profile, azimuth resolution, peak sidelobe ratio and integrated sidelobe ratio of the simulation results are analyzed. The whole process is cumbersome and time-consuming, and easily leads to waste of manpower and material resources. Summary of the invention

[0004] In view of the problems that the evaluation of the quality of traditional synthetic aperture sonar imaging models is not intuitive and time-consuming, resulting in waste of manpower and material costs, the present invention proposes a two-dimensional distance error analysis method for synthetic aperture sonar imaging models. In the two-dimensional distance error analysis method of the present invention, the proposed two-dimensional distance error analysis method can directly and quantitatively calculate the distance error of the synthetic aperture sonar imaging model, and directly evaluate the quality of the imaging model based on the error, which greatly improves the efficiency.

[0005] The present invention adopts a technical solution to solve the technical problem: the two-dimensional distance error analysis method first determines the distance of the target according to the equal-space sampling method in the distance direction, determines the synthetic aperture length corresponding to the farthest distance target and the coordinates of the target in the azimuth direction according to the beam width in the azimuth direction, then calculates the two-way slant range history experienced by the synthetic aperture sonar movement according to the precise propagation time of the synthetic aperture sonar, calculates the distance error for the approximate slant range history of the imaging model to be evaluated, adds the influence of the array element directivity function on the basis of the distance error, and averages the calculated distance error, and finally calculates the distance error for all targets to obtain a two-dimensional distance error that only depends on the distance and the array element. The two-dimensional distance error analysis method of the present invention mainly comprises the following steps:

[0006] (1) Determine the distance of the target by sampling at equal intervals in the distance direction;

[0007] (2) Determine the synthetic aperture length corresponding to the farthest target and the coordinates of the target in azimuth based on the beam width in azimuth;

[0008] (3) Based on the precise propagation time of synthetic aperture sonar, calculate the two-way slant range history of the synthetic aperture sonar receiving and transmitting array elements;

[0009] (4) Calculate the range error based on the approximate slant range history of the imaging model to be evaluated;

[0010] (5) The impact of adding the array element directivity function to the distance error;

[0011] (6) averaging the calculated distance errors;

[0012] (7) For all targets and all receiving array elements, the distance error is calculated to obtain the two-dimensional distance error.

[0013] According to one aspect of the present invention, the present invention provides a two-dimensional range error analysis method for a synthetic aperture sonar imaging model, wherein the two-dimensional range error analysis method comprises the following steps:

[0014] S1, determine the distance of the target by sampling in an equidistant manner in the distance upward;

[0015] S2, determining the synthetic aperture length corresponding to the farthest target and the coordinates of the target in azimuth according to the beam width in azimuth;

[0016] S3, based on the precise propagation time of synthetic aperture sonar, calculate the two-way slant range history experienced by the movement of synthetic aperture sonar receiving and transmitting array elements;

[0017] S4, calculating the range error for the approximate slant range history of the imaging model to be evaluated;

[0018] S5, the effect of adding the array element directivity function on the basis of the distance error;

[0019] S6, averaging the calculated distance errors;

[0020] S7, calculating the distance error for all targets and all receiving array elements to obtain a two-dimensional distance error.

[0021] As a further improvement of the technical solution of the present invention, in step S1, the calculation formula for determining the distance of the target in the distance upward according to the equal-spaced sampling method is: ,in Indicates the target distance, subscript Indicates that the data are taken at equal intervals within the surveying band. The distances of different targets, and all distances are arranged in order from small to large, the first distance value Greater than the minimum distance of the survey band, the last distance value Less than the maximum distance of the survey swath.

[0022] As a further improvement of the technical solution of the present invention, in step 2, the synthetic aperture length corresponding to the farthest distance target and the coordinates of the target in azimuth are determined according to the beam width in azimuth. Synthetic aperture length at position The calculation formula is: ,in Indicates the distance to the farthest target. represents the synthetic aperture length corresponding to the target at the farthest distance, It represents the negative 3 dB beam width of the transmitting element, so the azimuth coordinate value corresponding to the farthest target cannot be less than Considering the non-spatial nature of the azimuth of the positive side-looking synthetic aperture sonar, the Location The azimuth coordinates of each target are uniformly taken as: ,in Indicates that the distance is upward Location The common azimuth coordinates of the targets.

[0023] As a further improvement of the technical solution of the present invention, in step S3, the calculation formula for calculating the two-way slant range history experienced by the movement of the synthetic aperture sonar receiving and transmitting array elements is: , where the subscript Indicates The first receiving array element and the transmitting array element are composed of subsystems, Indicates the coordinates of the target in the range direction, Indicates that the distance is upward Location The common azimuth coordinates of the targets, Indicates the slow time in azimuth. Indicates The first receiving array element and the transmitting array element are composed of The distance between the transmitting and receiving elements in a subsystem satisfies , Indicates the total number of receiving array elements, Indicates the speed of the sonar platform in azimuth. Represents the speed of sound underwater.

[0024] As a further improvement of the technical solution of the present invention, in step S4, the calculation formula for calculating the distance error for the approximate slant range history of the imaging model to be evaluated is: ,in Indicates that for The receiving array element is calculated at The distance to the target at position, Indicates that the imaging model to be evaluated is for The receiving array element is calculated at The distance to the target at position, represents the wavelength corresponding to the center frequency of the transmitted signal, Depends on the azimuth slow time , Target distance , Transceiver array element spacing distance error.

[0025] As a further improvement of the technical solution of the present invention, in step S5, the calculation formula for adding the influence of the array element directivity function on the basis of the distance error is: ,in Indicates that it is located The angle of the target at the position relative to the transmitting array element is calculated as: ,in Indicates the calculation of inverse tangent. represents the binary directivity function of the transmitting array element, if ,but The value of is 1 if ,but The value of is 0, represents the distance error considering the array element directivity function, which depends on the azimuth slow time , Target distance , Transceiver array element spacing .

[0026] As a further improvement of the technical solution of the present invention, in step 6, the calculation formula for averaging the calculated distance errors is: ,in It means to find the maximum value. Indicates the minimum value processing. Represents the average processed error, which depends on the target distance , Transceiver array element spacing .

[0027] As a further improvement of the technical solution of the present invention, in step 7, for different target distances and Receive array elements and calculate the corresponding distance error .

[0028] According to another aspect of the present invention, the present invention further provides a two-dimensional range error analysis system for a synthetic aperture sonar imaging model, comprising:

[0029] A first determination unit is used to determine the distance of the target according to an equidistant sampling method in the distance direction;

[0030] A second determination unit is used to determine the synthetic aperture length corresponding to the farthest distance target and the coordinates of the target in the azimuth direction according to the beam width in the azimuth direction;

[0031] The first calculation unit is used to calculate the two-way slant range history experienced by the movement of the synthetic aperture sonar receiving and transmitting array elements according to the precise propagation time of the synthetic aperture sonar;

[0032] A second calculation unit is used to calculate the range error for the approximate slant range history of the imaging model to be evaluated;

[0033] An adding unit is used to add the influence of the array element directivity function on the basis of the distance error;

[0034] An averaging processing unit, used for averaging the calculated distance errors;

[0035] The third calculation unit is used to calculate the distance error for all targets and all receiving array elements to obtain a two-dimensional distance error.

[0036] As a further improvement of the technical solution of the present invention, the calculation formula for determining the distance of the target by the first determination unit in the distance direction according to the equal-spaced sampling method is: ,

[0037] in Indicates the target distance, subscript Indicates that the data are taken at equal intervals within the surveying band. The distances of different targets, and all distances are arranged in order from small to large, the first distance value Greater than the minimum distance of the survey band, the last distance value Less than the maximum distance of the survey swath.

[0038] Compared with the prior art, the present invention has at least the following beneficial effects: in the two-dimensional distance error analysis method of the present invention, the proposed two-dimensional distance error analysis method can directly and quantitatively calculate the distance error of the synthetic aperture sonar imaging model, and directly evaluate the quality of the imaging model based on the error, thereby greatly improving the efficiency.

[0039] Other beneficial effects of the present invention will be further disclosed in the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 The present invention provides a calculation process for a two-dimensional distance error analysis method.

[0041] Figure 2 Two-dimensional imaging geometry for a synthetic aperture sonar subsystem with separate transmitter and receiver subsystems.

[0042] Figure 3 The azimuth profiles of the imaging results, where (a) is the azimuth profile of the target at a distance of 30m, and (b) is the azimuth profile of the target at a distance of 200m.

[0043] Figure 4 Error map calculated for the present invention.

[0044] Figure 5 The figure is a flow chart of a two-dimensional distance error analysis method according to a preferred embodiment of the present invention.

[0045] Figure 6 The figure is a block diagram of a two-dimensional distance error analysis system according to a preferred embodiment of the present invention.

[0046] Figure 7 A block diagram of a computing device according to a preferred embodiment of the present invention is shown.

[0047] In the figure:

[0048] 600, two-dimensional distance error analysis system; 610, first determination unit; 620, second determination unit; 630, first calculation unit; 640, second calculation unit; 650, adding unit; 660, average processing unit; 670, third calculation unit;

[0049] 700, computing device; 710, memory; 720, processor; 730, input device; 740, output device. DETAILED DESCRIPTION

[0050] Before describing in detail any embodiment of the present invention, it should be understood that the present invention is not limited in its application to the construction and arrangement details of the components described below or illustrated in the following figures. The present invention can have other embodiments and can be practiced or carried out in various ways. In addition, it should be understood that the words and terms used here are for descriptive purposes and should not be considered restrictive. The use of "including" or "having" and its variations herein is intended to cover the items and their equivalents and additional items displayed below. Unless otherwise specified or limited, the terms "install", "connect", "support" and "couple" and their variations are widely used and cover direct installation and indirect installation, connection, support and connection. In addition, "connect" and "couple" are not limited to physical or mechanical connections or connections.

[0051] Furthermore, on the first aspect, in the disclosure of the present invention, the orientation or positional relationship indicated by terms such as "longitudinal", "transverse", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" are based on the orientation or positional relationship shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore the above terms cannot be understood as limitations on the present invention; on the second aspect, the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element may be one, while in another embodiment, the number of the element may be multiple, and the term "one" cannot be understood as a limitation on the quantity.

[0052] Attached Figure 1 The calculation process of a two-dimensional distance error analysis method of the present invention is shown. Figure 2 The two-dimensional imaging geometry of multi-array SAS (multi-array synthetic aperture sonar) is given, where the horizontal direction is the range direction and the vertical direction is the azimuth direction. Assume that the sonar platform speed is , the speed of sound underwater is , the transmitting signal of the transmitting array is modulated frequency Chirp signal, then The echo signal received by a receiving array element can be expressed as: ,in and They represent the fast time in distance and the slow time in azimuth respectively. Indicates the transmitted Chirp signal, is the carrier wavelength.

[0053] To consider the two-way slant distance history of the "stop-go-stop" approximation, Indicates the distance of the point target, represents the distance between the transmitting and receiving array elements, and the joint directivity function of the transmitting and receiving array elements is ignored. It indicates the distance that the receiving element moves in azimuth during the transmission and reception of signals. Indicates that the transmitting array element transmits the signal to the The precise propagation time of the signal during the process of receiving the echo by the receiving array element is expressed as:

[0054] .

[0055] The distance to the target is determined by sampling at equal intervals in the distance direction. The calculation formula is as follows: ,in Indicates the target distance, subscript Indicates that the mapping is done at equal intervals within the mapping zone. Taken The distances of different targets, and all distances are arranged in order from small to large, that is, , the first distance value Greater than the minimum distance of the survey band, the last distance value Less than the maximum distance of the survey swath.

[0056] In azimuth, the synthetic aperture length corresponding to the farthest target and the coordinates of the target in azimuth are determined according to the beam width. The synthetic aperture length of the target at position The calculation formula is as follows: ,in Indicates the distance to the farthest target. represents the synthetic aperture length corresponding to the target at the farthest distance, It represents the negative 3 dB beam width of the transmitting element, so the azimuth coordinate value corresponding to the farthest target cannot be less than Considering the non-spatial nature of the azimuth of the positive side-looking synthetic aperture sonar, the Location The azimuth coordinates of each target are uniformly taken as: ,in Indicates that the distance is upward Location The common azimuth coordinates of the targets.

[0057] According to the precise propagation time of synthetic aperture sonar, the two-way slant range course experienced by the synthetic aperture sonar receiving and transmitting array elements is calculated. The calculation formula is as follows: , where the subscript Indicates The first receiving array element and the transmitting array element are composed of subsystems, Indicates the coordinates of the target in the range direction, Indicates that the distance is upward Location The common azimuth coordinates of the targets, Indicates the slow time in azimuth. Indicates The first receiving array element and the transmitting array element are composed of The distance between the transmitting and receiving elements in a subsystem satisfies , Indicates the total number of receiving array elements, Indicates the speed of the sonar platform in azimuth. Represents the speed of sound underwater.

[0058] In his academic paper “Study on Multi-array SAS Line-by-Line Imaging Algorithm” published in the Journal of Harbin Engineering University in 2009, Wang Haitao derived an approximate slant range history based on the second-order order approximation method, which is expressed as:

[0059] , where the subscript Indicates The first receiving array element and the transmitting array element are composed of subsystems, Indicates the coordinates of the target in the range direction, Indicates that the distance is upward Location The common azimuth coordinates of the targets, Indicates the slow time in azimuth. Indicates The first receiving array element and the transmitting array element are composed of The distance between the transmitting and receiving elements in a subsystem satisfies , Indicates the total number of receiving array elements, Indicates the speed of the sonar platform in azimuth. Represents the speed of sound underwater.

[0060] The distance error is calculated based on the approximate slant range history obtained by Wang Haitao. The calculation formula is: ,in Indicates that for The receiving array element is calculated at The distance to the target at position, Indicates that the imaging model to be evaluated is for The receiving array element is calculated at The distance to the target at position, represents the wavelength corresponding to the center frequency of the transmitted signal, Depends on the azimuth slow time , Target distance , Transceiver array element spacing distance error.

[0061] Adding the influence of the array element directivity function to the distance error, the calculation formula is: ,in Indicates that it is located The angle of the target at the position relative to the transmitting array element is calculated as: ,in Indicates the calculation of inverse tangent. represents the binary directivity function of the transmitting array element, if ,but The value of is 1 if ,but The value of is 0, represents the distance error considering the array element directivity function, which depends on the azimuth slow time , Target distance , Transceiver array element spacing .

[0062] The calculation formula for averaging the calculated distance errors is: ,in It means to find the maximum value. Indicates the minimum value processing. Represents the average processed error, which depends on the target distance , Transceiver array element spacing .

[0063] For all targets and all receiving array elements, the calculated distance error becomes a two-dimensional distance error, which is processed as follows: for different target distances and The receiving element calculates the corresponding distance error according to the above steps Similarly, for all targets and all receiving array elements in the distance upward, the corresponding distance error can be calculated according to the above steps. , the phase error at this time It is simply a function of distance and the spacing between the receiving elements.

[0064] Assume that the carrier frequency is 150kHz, the length of the transmitting array element along the track is 0.08m, the length of a single receiving array element along the track is 0.04m, and there are 30 receiving array elements in total. The bandwidth of the transmitted linear frequency modulation signal is 20kHz, the pulse repetition period is 0.3s, and the sonar towing speed is 2m / s. Within the surveying band, the minimum target distance is 30m and the maximum target distance is 200m in the range direction. Considering these two targets, the azimuth profile after imaging is obtained by using the method in the academic paper "Research on Line-by-Line Imaging Algorithm of Multi-Subarray SAS" published by Wang Haitao in the "Journal of Harbin Engineering University" in 2009. Figure 3 As shown, Figure 3 (a) is the azimuth profile of the target at a distance of 30m. Figure 3 (b) is the azimuth profile of the target at a distance of 200m. Figure 3 The statistical peak sidelobe ratio, integrated sidelobe ratio, and azimuth resolution are shown in Table 1.

[0065] Table 1 Evaluation results of azimuth focusing performance of traditional methods

[0066]

[0067] It is not difficult to see that the traditional method requires imaging before evaluating the imaging performance indicators such as the peak sidelobe ratio, the integrated sidelobe ratio, and the azimuth resolution according to the azimuth profile statistics. The whole process is very time-consuming and is not conducive to the rapid evaluation of the imaging model performance. The error diagram obtained by the two-dimensional distance error analysis method of the present invention is as follows: Figure 4 As shown, based on Figure 4 The imaging model can be directly evaluated quantitatively, avoiding the need for traditional methods to use imaging models for imaging processing, which can greatly improve the evaluation efficiency.

[0068] Attached Figure 5 A two-dimensional distance error analysis method according to a preferred embodiment of the present invention is shown, which is used to directly and quantitatively calculate the distance error of a synthetic aperture sonar imaging model and directly evaluate the quality of the imaging model based on the error, wherein the two-dimensional distance error analysis method comprises the following steps:

[0069] S1, determine the distance of the target by sampling in an equidistant manner in the distance upward;

[0070] S2, determining the synthetic aperture length corresponding to the farthest target and the coordinates of the target in azimuth according to the beam width in azimuth;

[0071] S3, based on the precise propagation time of synthetic aperture sonar, calculate the two-way slant range history experienced by the movement of synthetic aperture sonar receiving and transmitting array elements;

[0072] S4, calculating the range error for the approximate slant range history of the imaging model to be evaluated;

[0073] S5, the effect of adding the array element directivity function on the basis of the distance error;

[0074] S6, averaging the calculated distance errors;

[0075] S7, calculating the distance error for all targets and all receiving array elements to obtain a two-dimensional distance error.

[0076] In a specific example of the two-dimensional distance error analysis method of the present invention, in step S1, the calculation formula for determining the distance of the target in the distance direction according to the equal-spaced sampling method is: ,in Indicates the target distance, subscript Indicates that the data are taken at equal intervals within the surveying band. The distances of different targets, and all distances are arranged in order from small to large, the first distance value Greater than the minimum distance of the survey band, the last distance value Less than the maximum distance of the survey swath.

[0077] In a specific example of the two-dimensional range error analysis method of the present invention, in step 2, the synthetic aperture length corresponding to the farthest distance target and the coordinates of the target in azimuth are determined according to the beam width in azimuth. Synthetic aperture length at position The calculation formula is: ,in Indicates the distance to the farthest target. represents the synthetic aperture length corresponding to the target at the farthest distance, It represents the negative 3 dB beam width of the transmitting element, so the azimuth coordinate value corresponding to the farthest target cannot be less than Considering the non-spatial nature of the azimuth of the positive side-looking synthetic aperture sonar, the Location The azimuth coordinates of each target are uniformly taken as: ,in Indicates that the distance is upward Location The common azimuth coordinates of the targets.

[0078] In a specific example of the two-dimensional range error analysis method of the present invention, in step S3, the calculation formula for calculating the two-way slant range history experienced by the movement of the synthetic aperture sonar receiving and transmitting array elements is: ,

[0079] The subscript Indicates The first receiving array element and the transmitting array element are composed of subsystems, Indicates the coordinates of the target in the range direction, Indicates that the distance is upward Location The common azimuth coordinates of the targets, Indicates the slow time in azimuth. Indicates The first receiving array element and the transmitting array element are composed of The distance between the transmitting and receiving elements in a subsystem satisfies , Indicates the total number of receiving array elements, Indicates the speed of the sonar platform in azimuth. Represents the speed of sound underwater.

[0080] In a specific example of the two-dimensional distance error analysis method of the present invention, in step S4, the calculation formula for calculating the distance error for the approximate slant range history of the imaging model to be evaluated is: ,in Indicates that for The receiving array element is calculated at The distance to the target at position, Indicates that the imaging model to be evaluated is for The receiving array element is calculated at The distance to the target at position, represents the wavelength corresponding to the center frequency of the transmitted signal, Depends on the azimuth slow time , Target distance , Transceiver array element spacing distance error.

[0081] In a specific example of the two-dimensional distance error analysis method of the present invention, in step S5, the calculation formula for adding the influence of the array element directivity function on the distance error is: ,in Indicates that it is located The angle of the target at the position relative to the transmitting array element is calculated as: ,in Indicates the calculation of inverse tangent. represents the binary directivity function of the transmitting array element, if ,but The value of is 1 if ,but The value of is 0, represents the distance error considering the array element directivity function, which depends on the azimuth slow time , Target distance , Transceiver array element spacing .

[0082] In a specific example of the two-dimensional distance error analysis method of the present invention, in step 6, the calculation formula for averaging the calculated distance errors is: ,in It means to find the maximum value. Indicates the minimum value processing. Represents the average processed error, which depends on the target distance , Transceiver array element spacing .

[0083] In a specific example of the two-dimensional distance error analysis method of the present invention, in step 7, for different target distances and Receive array elements and calculate the corresponding distance error .

[0084] Attached Figure 6 A two-dimensional distance error analysis system 600 according to a preferred embodiment of the present invention is shown, which is used to directly and quantitatively calculate the distance error of a synthetic aperture sonar imaging model and directly evaluate the quality of the imaging model based on the error, wherein the two-dimensional distance error analysis system 600 includes a first determination unit 610, a second determination unit 620, a first calculation unit 630, a second calculation unit 640, an adding unit 650, an averaging processing unit 660 and a third calculation unit 670.

[0085] Specifically, the first determination unit 610 is used to determine the distance of the target according to the equal-space sampling method in the distance direction;

[0086] The second determination unit 620 is used to determine the synthetic aperture length corresponding to the farthest target and the coordinates of the target in azimuth according to the beam width in azimuth; the first calculation unit 630 is used to calculate the two-way slant range history experienced by the movement of the synthetic aperture sonar receiving and transmitting array elements according to the precise propagation time of the synthetic aperture sonar; the second calculation unit 640 is used to calculate the distance error for the approximate slant range history of the imaging model to be evaluated; the adding unit 650 is used to add the influence of the array element directivity function on the basis of the distance error; the averaging processing unit 660 is used to average the calculated distance error; the third calculation unit 670 is used to calculate the distance error for all targets and all receiving array elements to obtain a two-dimensional distance error.

[0087] The calculation formula for determining the distance of the target by the first determining unit 610 in the distance direction according to the equal-spaced sampling method is: ,in Indicates the target distance, subscript Indicates that the data are taken at equal intervals within the surveying band. The distances of different targets, and all distances are arranged in order from small to large, the first distance value Greater than the minimum distance of the survey band, the last distance value Less than the maximum distance of the survey swath.

[0088] The second determination unit 620 determines the synthetic aperture length corresponding to the farthest distance target and the coordinates of the target in the azimuth direction according to the beam width in the azimuth direction. Synthetic aperture length at position The calculation formula is: ,in Indicates the distance to the farthest target. represents the synthetic aperture length corresponding to the target at the farthest distance, It represents the negative 3 dB beam width of the transmitting element, so the azimuth coordinate value corresponding to the farthest target cannot be less than Considering the non-spatial nature of the azimuth of the positive side-looking synthetic aperture sonar, the Location The azimuth coordinates of each target are uniformly taken as: ,in Indicates that the distance is upward Location The common azimuth coordinates of the targets.

[0089] The calculation formula for calculating the two-way slant range history of the synthetic aperture sonar receiving and transmitting array element movement by the first calculation unit 630 is: , where the subscript Indicates The first receiving array element and the transmitting array element are composed of subsystems, Indicates the coordinates of the target in the range direction, Indicates that the distance is upward Location The common azimuth coordinates of the targets, Indicates the slow time in azimuth. Indicates The first receiving array element and the transmitting array element are composed of The distance between the transmitting and receiving elements in a subsystem satisfies , Indicates the total number of receiving array elements, Indicates the speed of the sonar platform in azimuth. Represents the speed of sound underwater.

[0090] The calculation formula for calculating the distance error by the second calculation unit 640 for the approximate slant range history of the imaging model to be evaluated is: ,in Indicates that for The receiving array element is calculated at The distance to the target at position, Indicates that the imaging model to be evaluated is for The receiving array element is calculated at The distance to the target at position, represents the wavelength corresponding to the center frequency of the transmitted signal, Depends on the azimuth slow time , Target distance , Transceiver array element spacing distance error.

[0091] The calculation formula of the effect of adding the array element directivity function on the distance error by the adding unit 650 is: ,in Indicates that it is located The angle of the target at the position relative to the transmitting array element is calculated as: ,in Indicates the calculation of inverse tangent. represents the binary directivity function of the transmitting array element, if ,but The value of is 1 if ,but The value of is 0, represents the distance error considering the array element directivity function, which depends on the azimuth slow time , Target distance , Transceiver array element spacing .

[0092] The calculation formula for averaging the distance errors calculated by the averaging processing unit 660 is: ,in It means to find the maximum value. Indicates the minimum value processing. Represents the average processed error, which depends on the target distance , Transceiver array element spacing .

[0093] The third calculation unit 670 calculates the target distance according to different and Receive array elements and calculate the corresponding distance error .

[0094] Attached Figure 7 A computing device 700 according to a preferred embodiment of the present invention is shown, wherein the computing device 700 includes a memory 710 and a processor 720 coupled to the memory 710, wherein the memory 710 is used to store computer program instructions, and when the computer program instructions are executed in the processor 720, the processor 720 executes a two-dimensional distance error analysis method, wherein the two-dimensional distance error analysis method includes the following steps: determining the distance of the target in the distance direction according to the method of equally spaced sampling; determining the synthetic aperture length corresponding to the farthest distance target and the coordinates of the target in the azimuth direction according to the beam width in the azimuth direction; calculating the two-way slant range history experienced by the movement of the synthetic aperture sonar receiving and transmitting array elements according to the precise propagation time of the synthetic aperture sonar; calculating the distance error for the approximate slant range history of the imaging model to be evaluated; adding the influence of the array element directivity function on the basis of the distance error; averaging the calculated distance error; and calculating the distance error for all targets and all receiving array elements to obtain a two-dimensional distance error.

[0095] In one embodiment of the computing device 700 of the present invention, the memory 710 may include one or more computer program products, and the computer program product may include various forms of computer-readable storage media, such as volatile memory and / or non-volatile memory. The volatile memory may include, for example, a random access memory (RAM) and / or a cache memory (cache), etc. The non-volatile memory may include, for example, a read-only memory (ROM), a hard disk, a flash memory, etc. One or more computer program instructions may be stored on the computer-readable storage medium, and the processor 720 may run the program instructions to implement the functions of the two-dimensional distance error analysis method of the present invention described above.

[0096] In one embodiment of the computing device 700 of the present invention, the processor 720 can be a central processing unit (CPU) or other forms of processing units with data processing capabilities and / or instruction execution capabilities, which can run the program instructions stored on the computer-readable storage medium to implement the functions of the one-dimensional error analysis method of the present invention described above.

[0097] In one embodiment of the computing device 700 of the present invention, the computing device 700 may also include an input device 730 and an output device 740. The input device 730 may be, but is not limited to, a keyboard or a mouse. The output device 740 may be, but is not limited to, a display, a speaker, or a printer. The input device 730 and the output device 740 may be connected to the processor 720 via a bus system.

[0098] It should be understood by those skilled in the art that the embodiments of the present invention described above and shown in the accompanying drawings are only examples and do not limit the present invention. The purpose of the present invention has been fully and effectively achieved. The functional and structural principles of the present invention have been demonstrated and explained in the embodiments, and the embodiments of the present invention may be modified or altered in any way without departing from the principles.

Claims

1. A two-dimensional range error analysis method for a synthetic aperture sonar imaging model, characterized in that: The two-dimensional distance error analysis method comprises the following steps: S1, determine the distance of the target by sampling in an equidistant manner in the distance upward; S2, determining the synthetic aperture length corresponding to the farthest target and the coordinates of the target in azimuth according to the beam width in azimuth; S3, based on the precise propagation time of synthetic aperture sonar, calculate the two-way slant range history experienced by the movement of synthetic aperture sonar receiving and transmitting array elements; S4, calculating the range error for the approximate slant range history of the imaging model to be evaluated; S5, the effect of adding the array element directivity function on the basis of the distance error; S6, averaging the calculated distance errors; S7, calculating the distance error for all targets and all receiving array elements to obtain a two-dimensional distance error; In step S4, the distance error is calculated by the formula for calculating the approximate slant range history of the imaging model to be evaluated: , in Indicates that for The receiving array element is calculated at The distance to the target at position, Indicates that the imaging model to be evaluated is for The receiving array element is calculated at The distance to the target at position, represents the wavelength corresponding to the center frequency of the transmitted signal, Depends on the azimuth slow time , Target distance , Transceiver array element spacing The distance error; In step S5, the calculation formula for adding the influence of the array element directivity function on the basis of the distance error is: , in Indicates that it is located The angle of the target at the position relative to the transmitting array element is calculated as: , in Indicates the calculation of inverse tangent. represents the binary directivity function of the transmitting array element, if ,but The value of is 1 if ,but The value of is 0, represents the distance error considering the array element directivity function, which depends on the azimuth slow time , Target distance , Transceiver array element spacing ,in Indicates the speed of the sonar platform in azimuth. Indicates that the distance is upward Location The common azimuth coordinates of the targets, subscript Indicates that the data are taken at equal intervals within the surveying band. The distances of different targets, and all distances are arranged in order from small to large, the first distance value Greater than the minimum distance of the survey band, the last distance value Less than the maximum distance of the survey swath.

2. The two-dimensional distance error analysis method according to claim 1, characterized in that: In step S1, the calculation formula for determining the distance of the target in the distance direction according to the equal-spaced sampling method is: ,in Indicates the target distance.

3. The two-dimensional distance error analysis method according to claim 1, characterized in that: In step S2, the synthetic aperture length corresponding to the farthest distance target and the coordinates of the target in azimuth are determined according to the beam width in azimuth. Synthetic aperture length at position The calculation formula is: , in It represents the negative 3 dB beam width of the transmitting element, so the azimuth coordinate value corresponding to the farthest target cannot be less than , considering the non-spatial nature of the azimuth of the positive side-looking synthetic aperture sonar, the Location The azimuth coordinates of each target are uniformly taken as: .

4. The two-dimensional distance error analysis method according to claim 1, characterized in that: In step S3, the calculation formula for calculating the two-way slant range history experienced by the synthetic aperture sonar receiving and transmitting array element movement is: , The subscript Indicates The first subsystems, Represents the coordinate of the target in the range direction, Indicates the slow time in azimuth. Indicates The first The distance between the transmitting and receiving elements in a subsystem satisfies , Indicates the total number of receiving array elements, Represents the speed of sound underwater.

5. The two-dimensional distance error analysis method according to claim 1, characterized in that: In step S6, the calculation formula for averaging the calculated distance errors is: , in It means to find the maximum value. Indicates the minimum value processing. Represents the average processed error, which depends on the target distance , Transceiver array element spacing .

6. A two-dimensional range error analysis system for synthetic aperture sonar imaging models, characterized in that: include: A first determination unit is used to determine the distance of the target according to an equidistant sampling method in the distance direction; A second determination unit is used to determine the synthetic aperture length corresponding to the farthest distance target and the coordinates of the target in the azimuth direction according to the beam width in the azimuth direction; The first calculation unit is used to calculate the two-way slant range history experienced by the movement of the synthetic aperture sonar receiving and transmitting array elements according to the precise propagation time of the synthetic aperture sonar; A second calculation unit is used to calculate the range error for the approximate slant range history of the imaging model to be evaluated; An adding unit is used to add the influence of the array element directivity function on the basis of the distance error; An averaging processing unit, used for averaging the calculated distance errors; A third calculation unit is used to calculate the distance error for all targets and all receiving array elements to obtain a two-dimensional distance error; The calculation formula for calculating the distance error by the second calculation unit for the approximate slant range history of the imaging model to be evaluated is: ,in Indicates that for The receiving array element is calculated at The distance to the target at position, Indicates that the imaging model to be evaluated is for The receiving array element is calculated at The distance to the target at position, represents the wavelength corresponding to the center frequency of the transmitted signal, Depends on the azimuth slow time , Target distance , Transceiver array element spacing The distance error; The calculation formula of the effect of adding the array element directivity function based on the distance error by the adding unit is: ,in Indicates that it is located The angle of the target at the position relative to the transmitting array element is calculated as: ,in Indicates the calculation of inverse tangent. represents the binary directivity function of the transmitting array element, if ,but The value of is 1 if ,but The value of is 0, represents the distance error considering the array element directivity function, which depends on the azimuth slow time , Target distance , Transceiver array element spacing ,in Indicates the speed of the sonar platform in azimuth. Indicates that the distance is upward Location The common azimuth coordinates of the targets, subscript Indicates that the data are taken at equal intervals within the surveying band. The distances of different targets, and all distances are arranged in order from small to large, the first distance value Greater than the minimum distance of the survey band, the last distance value Less than the maximum distance of the survey swath.

7. The two-dimensional distance error analysis system according to claim 6, characterized in that: The calculation formula for determining the distance of the target by the first determination unit in the distance direction according to the equal-spaced sampling method is: ,in Indicates the target distance.

8. The two-dimensional distance error analysis system according to claim 6, characterized in that: The second determination unit determines the synthetic aperture length corresponding to the farthest distance target and the coordinates of the target in azimuth according to the beam width in azimuth, Synthetic aperture length at position The calculation formula is: ,in It represents the negative 3 dB beam width of the transmitting element, so the azimuth coordinate value corresponding to the farthest target cannot be less than , considering the non-spatial nature of the azimuth of the positive side-looking synthetic aperture sonar, the Location The azimuth coordinates of each target are uniformly taken as: .

9. The two-dimensional distance error analysis system according to claim 6, characterized in that: The calculation formula for averaging the distance errors calculated by the averaging processing unit is: ,in It means to find the maximum value. Indicates the minimum value processing. Represents the average processed error, which depends on the target distance , Transceiver array element spacing .

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