Information processing device, information processing method, and information processing program

Abstract

To provide an information processing device capable of calculating a distance interval which can suppress an overall error of an indicator calculated by sound wave propagation calculation within an acceptable tolerance, an information processing method, and an information processing program.SOLUTION: An information processing device for calculating a distance interval when calculating an indicator through sound wave propagation calculation comprises: an evaluation indicator calculation unit which calculates an evaluation indicator in each combination of a plurality of environmental conditions and a plurality of evaluation distance intervals which are a plurality of distance intervals serving as an object to be evaluated; an error calculation unit which calculates an evaluation error on the basis of a difference between the evaluation indicator and a reference indicator in each combination of the plurality of environmental conditions and the plurality of evaluation distance intervals; a candidate calculation unit which calculates a plurality of candidate distance intervals serving as a distance interval candidate on the basis of comparison results between an evaluation error and an allowable error of each of the plurality of evaluation distance intervals and stores the calculated plurality of candidate distance intervals in a storage device; and a distance interval determination unit which determines the candidate distance interval corresponding to the given environmental conditions as the distance interval from the plurality of candidate distance intervals stored in the storage device.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an information processing device, an information processing method, and an information processing program for calculating a distance interval when calculating an index by sound wave propagation calculation. [Background technology]

[0002] Conventionally, devices such as sonars are known that detect the presence of underwater objects, such as marine organisms, by receiving sound waves emitted from the objects. Sound waves emitted from the object propagate through the ocean while repeatedly being reflected and refracted, and reach a receiver such as a sonar. The propagation path is not constant because it depends on the sound speed distribution in the ocean, and the position where sound waves from the sound source can be received with an appropriate sound pressure level is also not constant. Therefore, the amount of sound pressure reduction during sound wave propagation from the sound source to the receiver is calculated in advance using the sound speed distribution in the target ocean area. This reduction in sound pressure is called propagation loss and is calculated using various sound propagation models. Non-Patent Documents 1 and 2 disclose the use of a parabolic equation model (hereinafter referred to as the "PE model") as a sound propagation model. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Jensen et al., “Chapter 6. Parabolic Equations,” in Computational Ocean Acoustics Second edition, 2011 [Non-patent document 2] Collins, “A split-step Pade solution for the parabolic equation method”, J. Acoust. Soc. Am. 93(4), Pt. 1 1993 Summary of the Invention [Problem to be solved by the invention]

[0004] Generally, when calculating propagation loss, an error occurs between the calculated propagation loss and the actual propagation loss due to the difference between the sub-bottom sound speed and the underwater sound speed. The error between the calculated propagation loss and the actual propagation loss becomes smaller as the distance interval used to calculate the envelope sound pressure becomes smaller. On the other hand, since the calculation amount increases as the distance interval used to calculate the envelope sound pressure becomes smaller, it is considered important to set a maximum allowable distance interval. However, according to the methods disclosed in Non-Patent Documents 1 and 2, the maximum distance interval required to suppress the error to within a tolerable value is calculated based on the error in the propagation loss calculated based only on the sub-bottom sound speed when calculating the envelope sound pressure at only one distance interval at a certain depth. For this reason, conventional propagation loss calculation devices may not be able to calculate a distance interval that suppresses the overall error in the propagation loss to within a tolerable value.

[0005] The present invention has been made to solve the above-mentioned problems, and aims to provide an information processing device, an information processing method, and an information processing program that can calculate a distance interval that keeps the overall error of the index calculated by sound wave propagation calculation within an acceptable value. [Means for solving the problem]

[0006] The information processing device of the present invention is an information processing device that calculates distance intervals when calculating an index by sound wave propagation calculation, and is equipped with an evaluation index calculation unit that calculates an evaluation index for each combination of multiple environmental conditions and multiple evaluation distance intervals that are multiple distance intervals to be evaluated, an error calculation unit that calculates an evaluation error based on the difference between the evaluation index and a reference index for each combination of multiple environmental conditions and multiple evaluation distance intervals, a candidate calculation unit that calculates multiple candidate distance intervals to be candidates for distance intervals based on the results of comparing the evaluation error of each of the multiple evaluation distance intervals with the allowable error for each of the multiple environmental conditions and stores the calculated candidate distance intervals in a storage device, and a distance interval determination unit that determines the candidate distance interval that corresponds to the given environmental condition from the multiple candidate distance intervals stored in the storage device as the distance interval.

[0007] The information processing method of the present invention is an information processing method for an information processing device that calculates a distance interval when calculating an index by sound wave propagation calculation, and includes an evaluation index calculation step that calculates an evaluation index for each combination of a plurality of environmental conditions and a plurality of evaluation distance intervals that are a plurality of distance intervals to be evaluated; an error calculation step that calculates an evaluation error based on the difference between the evaluation index and a reference index for each combination of a plurality of environmental conditions and a plurality of evaluation distance intervals; a candidate calculation step that calculates a plurality of candidate distance intervals that are distance interval candidates based on the results of comparing the evaluation error of each of the plurality of evaluation distance intervals with the allowable error for each of the plurality of environmental conditions, and stores the candidate distance intervals in a storage device; and a distance interval determination step that determines, from the plurality of candidate distance intervals stored in the storage device, a candidate distance interval that corresponds to the given environmental condition as the distance interval.

[0008] The information processing program of the present invention is an information processing program for calculating distance intervals when calculating an index by sound wave propagation calculation, and causes a processor of an information processing device to execute the following steps: an evaluation index calculation step for calculating an evaluation index for each combination of multiple environmental conditions and multiple evaluation distance intervals, which are multiple distance intervals to be evaluated; an error calculation step for calculating an evaluation error based on the difference between the evaluation index and a reference index for each combination of multiple environmental conditions and multiple evaluation distance intervals; a candidate calculation step for calculating multiple candidate distance intervals to be candidates for distance intervals based on the results of comparing the evaluation error of each of the multiple evaluation distance intervals with the allowable error for each of the multiple environmental conditions, and storing the candidate distance intervals in a storage device; and a distance interval determination step for determining, as the distance interval, a candidate distance interval corresponding to a given environmental condition from the multiple candidate distance intervals stored in the storage device. [Effects of the Invention]

[0009] According to the present invention, a plurality of candidate distance intervals that are candidates for the distance interval to be calculated are calculated based on the results of comparing the evaluation error of each of a plurality of evaluation distance intervals with the allowable error under each of a plurality of environmental conditions. Therefore, the information processing device, information processing method, and information processing program can calculate a distance interval that limits the overall error of the index calculated by the sound wave propagation calculation to the allowable value. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a block diagram showing a conventional propagation loss calculation device. [Figure 2] FIG. 1 is a schematic diagram showing a distance-dependent environment where the seafloor has a constant slope. [Figure 3] Schematic diagram showing two distance-dependent environments with different seafloor slopes. [Figure 4] 1 is a block diagram showing a propagation loss calculation device according to a first embodiment. [Figure 5] 4 is a flowchart showing a propagation loss calculation method according to the first embodiment. [Figure 6] FIG. 10 is a diagram for explaining how to calculate the difference between the evaluated propagation loss other than the minimum evaluation distance interval and the reference propagation loss according to the first embodiment. [Figure 7] FIG. 4 is a diagram for explaining a method of calculating a candidate distance interval according to the first embodiment. [Figure 8] FIG. 2 is a diagram for explaining an interpolation method according to the first embodiment. [Figure 9] FIG. 10 is a diagram illustrating a method for dividing the section from the sound source to the receiver into sections with a constant seabed slope, according to a modification of the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments, and various modifications are possible without departing from the spirit of the present invention. Furthermore, the present invention includes all possible combinations of the configurations shown in the following embodiments. In addition, in each drawing, components with the same reference numerals are the same or equivalent, and this is common throughout the entire specification.

[0012] Embodiment 1 Before describing the first embodiment, a conventional information processing device 9, which is a prerequisite for the information processing device 1 according to the first embodiment, will be described with reference to FIG. 1. FIG. 1 is a block diagram showing the conventional information processing device 9. The information processing device 9 is a device for calculating in advance, by sound wave propagation calculation, a decrease in sound pressure (propagation loss) that occurs during sound wave propagation from the object that serves as the sound source to a receiver that receives the sound waves emitted from the sound source, when detecting the presence of an underwater object using a sonar or the like by receiving sound waves emitted from the object. The information processing device 9 includes, as functional units, a distance interval calculation unit 91 and a propagation loss calculation unit 92. The information processing device 9 is configured by an arithmetic unit such as a microcomputer that realizes each functional unit by a processor reading and executing a program stored in a memory, or hardware such as a circuit device corresponding to each functional unit.

[0013] First, a method for calculating distance intervals and propagation loss in a conventional information processing device 9 will be described, assuming that the conventional information processing device 9 uses a PE model. The PE model is a representative sound wave propagation model, and calculates propagation loss in a distance-dependent environment where the sound speed profile (depth characteristics of sound speed) between the sound source and the receiver and the water depth change with distance. In the PE model, the sound pressure p(r,z) relative to the horizontal distance r from the sound source to the receiver (hereinafter referred to as distance) and the receiver depth z satisfies the Helmholtz equation in formula (1).

[0014]

number

[0015] Here, k = ω / c(r,z) (wave number) for the angular frequency of the sound wave ω, distance r, and sound speed c(r,z) at depth z. The solution p(r,z) to equation (1) is the sound pressure p0 at a point 1 m away from the sound source normalized to |p0| = 1, and the propagation loss TL(r,z) can be calculated from the sound pressure p(r,z) using equation (2).

[0016]

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[0017] The sound pressure p(r,z) is expressed in the form of equation (3).

[0018]

number

[0019] where k0 is the reference sound speed c (0) wave number (=ω / c (0) ) and H0 (1) (·) is the zeroth-order Hankel function of the first kind. The reference sound speed is given as a typical sound speed in water (for example, 1500 m / s) or the average sound speed. Below, ψ(r,z) is called the envelope sound pressure. By substituting equation (3) into equation (1) and ignoring the backward wave propagating backward (from the receiver to the sound source), we obtain the equation for the forward wave expressed as equation (4).

[0020]

number

[0021] Here, n(r,z) is the refractive index (=c (0) / c(r,z)). The solution ψ of this equation satisfies the relationship of equation (5) with respect to the distance Δr.

[0022]

number

[0023] Here, if we assume that the integrand on the right-hand side does not depend on the distance r', then equation (5) can be transformed into equation (6).

[0024]

number

[0025] Given an envelope sound pressure ψ(r0,z) at a distance r0, the distance characteristic of the envelope sound pressure ψ(r0+jΔr,z), j=1,2,...,J can be sequentially obtained using equation (6), and the distance characteristic of the sound pressure can be obtained using equation (3), and the distance characteristic of the propagation loss can be obtained using equation (2).

[0026] Incidentally, in transforming equation (5) into equation (6), it was assumed that the integrand does not depend on distance between distance r and distance r + Δr. According to Non-Patent Document 1, the error between the envelope sound pressure ψ(r + Δr,z) at distance r + Δr calculated under this assumption and the actual envelope sound pressure is given in proportion to the envelope sound pressure ψ(r,z) at distance r, and the magnitude of the proportionality coefficient E is given by equation (7).

[0027]

number

[0028] where ∂ 2 / ∂z 2 was ignored as the change in distance was small. Equation (7) shows that the error increases as the distance interval Δr increases, and the error increases as the change in refractive index over distance, i.e., the change in sound speed over distance, increases. When calculating over the same distance range, a larger Δr reduces the amount of calculation required compared to a smaller Δr. In particular, since the PE model performs calculations by advancing the distance in increments of Δr, a method is needed to set as large a distance interval Δr as possible while allowing for a certain degree of error.

[0029] For simplicity's sake, consider a distance-dependent environment where the seabed has a constant slope θ. Figure 2 is a schematic diagram showing a distance-dependent environment where the seabed has a constant slope θ. The water depth at distance 0 is d, and the depth of the seabed surface increases with distance at a slope θ. Assuming that the change in the speed of sound in water with respect to distance is negligibly small compared to the difference between the speed of sound below the seabed and the speed of sound in water, an error from equation (7) will occur when the seabed is located between point (r,z) and point (r+Δr,z). Therefore, the approximation formula shown in equation (8) is applied.

[0030]

number

[0031] where c (W) is the speed of sound in water, and c (B) is the speed of sound below the seafloor. Substituting equation (8) into equation (7) gives equation (9).

[0032]

number

[0033] Here, the tolerance for error E is E max Then, equation (10) is shown.

[0034]

number

[0035] The distance Δr that satisfies equation (10) is given by equation (11).

[0036]

number

[0037] The maximum distance that satisfies Equation (11) is Δr (max) Then, equation (12) is obtained.

[0038]

number

[0039] In this way, the error tolerance E max The maximum distance Δr to be kept below (max) Equation (12) can be used to determine the tolerance E max The smaller the distance Δr (max) must also be small, and the speed of sound below the seafloor, c (B) The speed of sound in water, c (W) The larger the difference, the greater the distance Δr (max) This indicates that the value must be reduced.

[0040] The distance calculation unit 91 calculates the error tolerance E according to equation (12). max , underwater sound speed c (W) , and the speed of sound under the seafloor c (B) Using the distance interval Δr (max) The propagation loss calculation unit 922 calculates the distance interval Δr calculated by the distance interval calculation unit 91 according to the formulas (2), (3) and (6). (max) The conventional information processing device 9 calculates the propagation loss TL(r,z) by using the distance interval Δr (max) , the speed of sound below the seafloor, c (B) and the speed of sound in water, c (W) It is characterized by the fact that it is determined based on the difference between

[0041] (Problems with conventional information processing devices 9) The error expressed by equation (7) is the error that occurs when the distance advances by Δr at a certain depth, and does not represent the error included in the finally calculated propagation loss TL(r,z). Therefore, even if the error expressed by equation (7) is kept below the allowable value, it may not be possible to keep the error in the finally calculated propagation loss TL(r,z) below the allowable value. Also, the factor that affects the error included in the propagation loss TL(r,z) is the speed of sound below the seafloor c (B) But that's not all. Other factors that affect the error are explained below.

[0042] One of the factors that influences the error in the propagation loss TL(r,z) is the magnitude of the seabed slope. Figure 3 shows a schematic diagram of two distance-dependent environments with different seabed slopes. The seabed slope in Figure 3(b) is larger than that in Figure 3(a), and the depth range where the seabed surface is located between distance r and distance r + Δr is larger in Figure 3(b). The "region where an error occurs across the seabed surface" in Figure 3 is the depth range where the error shown in Equation (7) occurs when calculating the envelope sound pressure at distance r + Δr from the envelope sound pressure at distance r using Equation (6). Comparing Figures 3(a) and 3(b), it can be seen that the greater the seabed slope, the wider the depth range. In particular, in the "region where calculations are based on sound pressure with error" in Figure 3, the calculation of the envelope sound pressure up to distance r already crosses the seabed at some distance. Therefore, the envelope sound pressure at distance r contains an error due to the difference between the speed of sound below the seafloor and the speed of sound in water, as already shown in equation (7), and this error continues to propagate over subsequent distances.

[0043] In this way, the greater the bottom slope, the more opportunities there are for errors in equation (7) to occur, and the greater the impact of the error spreading to other depths, so the error contained in the finally calculated propagation loss TL(r,z) also becomes larger. For this reason, the distance interval Δr (max) However, the equation (12) in the conventional information processing device 9 does not include the seabed slope θ, and the larger the seabed slope θ, the smaller the distance interval Δr (max) cannot be made smaller.

[0044] In addition, one of the factors that affect the error in the propagation loss TL(r,z) is the water depth. The calculation of the envelope sound pressure ψ(r+Δr,z) based on the envelope sound pressure ψ(r,z) using Equation (6) is not independent of the depth z, but is dependent on ∂ 2 / (∂z 2), the error in equation (7) spreads to other depths and is affected by the error in equation (7) that occurs at other depths. Therefore, the propagation loss TL(r,z) not only includes the error caused by crossing the seafloor, but also propagates to other depths in a complex manner.

[0045] In this way, the error contained in the propagation loss TL(r,z) varies depending on the water depth due to the influence of spreading to other depths. For example, the shallower the water depth, the larger the error, since the depth-wise spread of the error generated at the seabed is repeatedly reflected by the sea surface and seabed and is superimposed on the underwater propagation loss. On the other hand, the deeper the water depth, the fewer times the error spreads in the depth direction and is reflected by the sea surface and seabed, so the smaller the error superimposed on the underwater propagation loss. Therefore, the shallower the water depth, the smaller the distance interval Δr (max) The deeper the water, the smaller the distance interval Δr (max) However, the water depth d is not included in the equation (12) in the conventional information processing device 9, and the distance interval Δr (max) cannot be changed.

[0046] As described above, in the conventional information processing device 9, when the calculation of the envelope sound pressure by Equation (6) is advanced by one distance interval Δr, the sub-bottom sound speed c (B) The error E depends only on the distance interval Δr (max) For this reason, the conventional information processing device 9 has a function to calculate the speed of sound under the seafloor, c (B) In addition, the distance interval Δr is set to keep the overall error of the propagation loss TL(r,z), which changes depending on the seabed slope θ and water depth d, within the allowable value. (max) There was a problem in that it was not possible to determine

[0047] (Information processing device 1) An information processing device according to a first embodiment will be described. FIG. 4 is a block diagram showing the information processing device according to the first embodiment. Similar to a conventional information processing device 9, the information processing device 1 is a device for calculating in advance the propagation loss occurring during sound wave propagation from a sound source to a receiver as an index to be calculated by sound wave propagation calculation. The information processing device 1 includes, as functional units, an evaluation index calculation unit 11, an error calculation unit 12, a candidate calculation unit 13, a distance interval determination unit 14, and an index calculation unit 15. The information processing device 1 is configured by a calculation device such as a microcomputer that realizes each functional unit by a processor reading and executing a program stored in a memory, or hardware such as a circuit device corresponding to each functional unit. The information processing device also has a storage device in which a distance interval table, which will be described later, is stored. The storage device is configured by an auxiliary storage device such as an SSD or HDD. The program stored in the memory corresponds to the "information processing program" of the present disclosure.

[0048] Before describing the configuration of the information processing device of the first embodiment, the concept of a method for calculating propagation loss (hereinafter simply referred to as an "information processing method") performed by the information processing device will be described. In the information processing method of the first embodiment, a distance interval Δr is set so as to suppress an error in propagation loss TL(r,z) within an allowable range. (max) is determined. Here, the propagation loss is calculated in advance using each of a plurality of distance intervals, and the propagation loss error is calculated from the result. The propagation loss for a plurality of distance intervals calculated in advance will be referred to as the evaluated propagation loss, and the error in the evaluated propagation loss will be referred to as the evaluation error. Furthermore, the plurality of distance intervals used to calculate the evaluated propagation loss will be referred to as the evaluation distance interval. The larger the evaluation distance interval, the larger the corresponding evaluation error, and from this relationship, it is possible to obtain a distance interval that keeps the propagation loss error within an acceptable range. Note that the propagation loss corresponds to an "index" calculated by the acoustic wave propagation calculation of the present disclosure, and the evaluated propagation loss corresponds to an "evaluation index" that is the evaluation target of the present disclosure.

[0049] In addition, in the first embodiment, three factors are considered to affect the error in propagation loss: seabed slope, sub-bottom sound speed, and water depth. The relationship between the evaluation distance interval and the evaluation error changes depending on the combination of these factors. Therefore, multiple values ​​are set within the possible ranges of seabed slope, sub-bottom sound speed, and water depth, and the evaluated propagation loss is calculated for each combination, and the evaluation error is calculated based on this. The multiple values ​​set within the possible ranges of seabed slope, sub-bottom sound speed, and water depth will be referred to as the evaluated seabed slope, evaluated sub-bottom sound speed, and evaluated water depth, respectively, hereinafter.

[0050] At this stage, the relationship between the evaluation distance interval and the evaluation error is obtained for each combination of the estimated seabed slope, estimated sub-sound speed, and estimated water depth. This makes it possible to obtain a distance interval that keeps the error within an acceptable range for each combination of the estimated seabed slope, estimated sub-sound speed, and estimated water depth. Hereinafter, the distance interval obtained in this manner will be referred to as the candidate distance interval. Also, below, the relationship between the candidate distance interval and the estimated seabed slope, estimated sub-sound speed, and estimated water depth will be referred to as the distance interval table.

[0051] Once the distance interval table is created, it becomes possible to calculate the propagation loss for any seabed slope, sub-bottom sound speed, and water depth. Specifically, by interpolating the relationship between the candidate distance intervals and the estimated seabed slope, sub-bottom sound speed, and estimated water depth stored in the distance interval table, a distance interval for any seabed slope, sub-bottom sound speed, and water depth can be obtained, and the propagation loss can be calculated using this.

[0052] The evaluation index calculation unit 11 calculates an evaluation propagation loss as an evaluation index under each of a plurality of environmental conditions. Specifically, the evaluation index calculation unit 11 calculates an evaluation seabed slope θ k ,k=1,2,…,K and the estimated sub-bottom sound speed c l ,l=1,2,…,L and the evaluation water depth d m ,m=1,2,…,M, and then define the environmental conditions by combining them. Then, the evaluation distance interval ΔR s = sΔR1, s = 1, 2, ..., S are used to evaluate the propagation loss TL klm (s)(r0+jΔR s ,z n ), j=1,2,…,J s ,n=1,2,...,N is calculated. Here, the estimated seabed slope θ k ,k=1,2,…,K,Evaluation sub-bottom sound speed c l ,l=1,2,…,L, and evaluation water depth d m ,m=1,2,…,M are the values ​​that can be taken in the range of the seabed slope, the sub-bottom sound speed, and the water depth, respectively. s is the estimated propagation loss TL klm (s) (r0+jΔR s ,z n ), j=1,2,…,J s is the distance number, and for s = 2, 3, ..., S, J1ΔR1 ≥ J s ΔR s =J s sΔR1, i.e., J1 ≥ J s The maximum J that satisfies s s The evaluation distance interval ΔR s =sΔR1, s=1, 2, . . . , S are the targets of evaluation in the error calculation unit 12, that is, the targets of calculation of the evaluation error.

[0053] The minimum evaluation distance interval ΔR1 is the S evaluation distance intervals ΔR s , s=1,2,…,S, the smallest value among them, and the evaluation path loss TL for the minimum evaluation distance interval ΔR1 klm (1) (r0+jΔR1,z n ), j=1, 2, ..., J1 will be used as a reference for calculating the evaluation error later. Hereinafter, this may be referred to as the reference path loss. The reference path loss corresponds to the "reference index" in this disclosure.

[0054] The error calculation unit 12 calculates the reference propagation loss, that is, the estimated propagation loss TL for s=1, for all combinations of the index k=1, 2, ..., K of the estimated seabed slope, the index l=1, 2, ..., L of the estimated sub-seabed sound speed, and the index m=1, 2, ..., M of the estimated water depth. klm (1) (r0+jΔR1,z n), j=1,2,…,J1,n=1,2,…,N as the basis for the evaluated propagation loss TL klm (s) (r0+jΔR s ,z n ), j=1,2,…,J s ,n=1,2,…,N evaluation error ε klm (ΔR s ), s=1,2,…,S is calculated.

[0055] The candidate calculation unit 13 calculates candidate distance intervals Δr for all combinations of index k=1, 2, ..., K of the evaluated seabed slope, index l=1, 2, ..., L of the evaluated sub-seabed sound speed, and index m=1, 2, ..., M of the evaluated water depth. klm Specifically, the candidate calculation unit 13 calculates the evaluation distance interval ΔR for all combinations of the index k=1, 2, ..., K of the evaluated seabed slope, the index l=1, 2, ..., L of the evaluated sub-seabed sound speed, and the index m=1, 2, ..., M of the evaluated water depth. s and the evaluation error ε klm (ΔR s ) and the candidate distance interval Δr from the predetermined tolerance ε klm The allowable error ε is set to a range in which the error between the propagation loss calculated using a certain distance interval and the actual propagation loss is allowable. The estimated seabed slope θ obtained in this way is k ,k=1,2,…,K and the estimated sub-bottom sound speed c l ,l=1,2,…,L and the evaluation water depth d m ,m=1,2,…,M and candidate distance interval Δr klm The relationship between the distance and the distance is called the distance interval table. k ,c l ,d m ,Δr klm ), k=1,2,…,K, l=1,2,…,L, m=1,2,…,M.

[0056] The distance interval determination unit 14 determines the distance between the seabed and the ocean floor based on the given seabed slope θ and the sub-seabed sound speed c (B) , and water depth d, and distance interval table (θ k ,c l ,d m,Δr klm ), k=1,2,…,K, l=1,2,…,L, m=1,2,…,M from the distance interval Δr (max) Determine.

[0057] The index calculation unit 2 calculates the propagation loss as an index calculated by sound wave propagation calculation. Specifically, the index calculation unit 2 calculates the propagation loss as an index calculated by sound wave propagation calculation. (B) and the propagation loss TL(r,z) for the water depth d is calculated by dividing the distance Δr (max) Calculate using:

[0058] The storage device 21 stores a distance interval table (θ k ,c l ,d m ,Δr klm ),k=1,2,…,K,l=1,2,…,L,m=1,2,…,M.

[0059] (Information processing method) Next, the information processing method by the information processing device 1 of the first embodiment will be described in detail with reference to Fig. 5. Fig. 5 is a flowchart showing the information processing method according to the first embodiment. First, the evaluation index calculation unit 11 calculates an evaluation seabed slope θ k , k=1,2,…,K and the estimated sub-bottom sound speed c l , l=1,2,…,L and the evaluation water depth d m , m = 1, 2, ..., M, the evaluation distance interval ΔR s For each of =sΔR1, s=1, 2, …, S, the estimated path loss TL klm (s) (r0+jΔR s ,z n ), j=1,2,…,J s , n=1, 2, ..., N is calculated (step S1). klm (s) (r0+jΔR s ,z n ), j=1,2,…,J s ,n=1,2,...,N is calculated according to equations (6), (3) and (2).

[0060] Here, the evaluation propagation loss TL for the minimum evaluation distance interval ΔR1 klm (1) (r0+jΔR1,z n ), j=1,2,...,J1,n=1,2,...,N are the reference propagation losses that will be used as the basis for calculating the evaluation error later, and the distance interval ΔR1 is set to a value that is small enough that the error contained in the propagation loss can be ignored. For example, in Non-Patent Document 2, in order to verify the accuracy of the sound wave propagation model, the result when the distance interval is set to 1 / 6 of the wavelength is used as the reference. Also, ΔR s , s=2, 3, ..., S are set to ΔR so that the difference in propagation loss over the same distance can be calculated in the subsequent calculation of the evaluation error in the error calculation unit 12. s =sΔR1, that is, an integer multiple of ΔR1.

[0061] Next, the error calculation unit 12 calculates an evaluation error ε klm (ΔR s ), s=1, 2, ..., S is calculated (step S2). Here, the evaluation error ε klm (ΔR1) is set to 0. Also, the evaluation error ε for s=2,3,…,S klm (ΔR s ) is calculated using the following method:

[0062] FIG. 6 is a diagram for explaining how to calculate the difference between the evaluation path loss other than the minimum evaluation distance interval and the reference path loss according to the first embodiment. Note that FIG. 6 shows the case where s=4. First, as shown in FIG. 6, the evaluation error ε klm (ΔR s ), s=2, 3, ..., S, the reference path loss TL for s=1 is calculated. klm (1) (r0+jΔR1,z n ), j=1,2,…,J1, the distance r0+jΔR according to the evaluation distance interval s=2,3,…,S s =r0+jsΔR1,j=1,2,…,J s Reference path loss TL atklm (1) (r0+jsΔR1,z n ), j=1,2,…,J s ,n=1,2,...,N are extracted. Then, the extracted reference path loss TL klm (1) (r0+jsΔR1,z n ), j=1,2,…,J s ,n=1,2,…,N and s=2,3,…,S for the estimated path loss TL klm (s) (r0+jΔR s ,z n ), j=1,2,…,J s ,n=1,2,...,N, and take the difference between the same distances.

[0063] Evaluation error ε klm (ΔR s ), s=2, 3, ..., S may be calculated, for example, as the average of the differences expressed by equation (13) or as the root mean square of the differences expressed by equation (14). The average of the differences and the bisection mean error of the differences correspond to the "statistics" of the differences in this disclosure.

[0064]

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[0065]

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[0066] The error calculation unit 12 calculates the reference propagation loss TL for the minimum evaluation distance interval ΔR1. klm (1) (r0+jsΔR1,z n ), j=1,2,…,J s ,n=1,2,…,N and s=2,3,…,S for the estimated path loss TL klm (s) (r0+jΔR s ,z n ), j=1,2,…,J s ,n=1,2,…,N and the evaluation error ε klm (ΔRs ) may be calculated.

[0067] Next, returning to FIG. 5, the candidate calculation unit 13 calculates the evaluation error ε klm (ΔR s ), s=1,2,...,S, and the candidate distance interval Δr is calculated from the predetermined tolerance ε using the following method. klm is calculated and a distance interval table is created (step S3).

[0068] 7 is a diagram for explaining a method for calculating candidate distance intervals according to the first embodiment. As shown in FIG. 7, the evaluation error ε klm (ΔR s ) and the tolerance ε. Then, first ε klm (ΔR s When s^ is the value for which )>ε, the evaluation error ε klm The maximum candidate distance interval Δr for which is less than the tolerance ε klm In the figures showing the following formulas, when a character with a "^" above it is explained in the text, it will be expressed by writing a "^" after the character, such as "s^".

[0069]

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[0070] In addition, equation (15) is ΔR s^-1 ≦ΔR≦ΔR s^ For ΔR that satisfies klm This is linear interpolation assuming that (ΔR) changes linearly, but any interpolation method that satisfies the required interpolation accuracy may be used.

[0071] The candidate distance interval Δr calculated by the candidate calculation unit 13 klm,k=1,2,…,K,l=1,2,…,L,m=1,2,…,M are the corresponding estimated seabed slopes θ k ,k=1,2,…,K,Evaluation sub-bottom sound speed c l ,l=1,2,…,L, and evaluation water depth d m ,m=1,2,...,M is linked to the distance interval table (θ k ,c l ,d m ,Δr klm ), k=1, 2, . . . , K, l=1, 2, . . . , L, and m=1, 2, . . . , M, and are stored in the storage device 21.

[0072] The above process is the next process, which is to calculate the seabed slope θ and the sub-seabed sound speed c (B) This is done before the process of calculating the propagation loss for the seabed slope θ, the speed of sound below the seabed c, and the water depth d. (B) , and the water depth d are given, the propagation loss is calculated by the process described below.

[0073] Returning to FIG. 5, the distance determination unit 14 determines the distance between the seabed and the seabed by calculating the given seabed slope θ and the sub-seabed sound speed c (B) , the distance interval table (θ k ,c l ,d m ,Δr klm ), k = 1, 2, ..., K, l = 1, 2, ..., L, m = 1, 2, ..., M, and the distance interval Δr (max) Specifically, the distance interval Δr is determined by the following method (step S4). (max) Determine.

[0074] First, starting from k=1, evaluate the seabed slope θ k and the seabed slope θ, and first k The k for which θ is greater than 1 is called k^. Similarly, starting from l=1, the sub-bottom sound speed c l and the speed of sound below the seafloor, c (B) Compare with and first c l >c (B) Let l^ be the l that is obtained. Similarly, starting from m=1, the evaluation depth d m Compare with the water depth d, and first m Let m^ be the m that becomes >d.

[0075] Next, θ k^-1 , θ k^ , c l^-1 , c l^ , d m^-1 , d m^ and the candidate distance interval Δr( k^-1 , l^-1 , m^-1 ), Δr( k^ , l^-1 , m^-1 ), Δr( k^-1 , l^ , m^-1 ), Δr( k^-1 , l^-1 , m^ ), Δr( k^ , l^ , m^-1 ), Δr( k^ , l^-1 , m^ ), Δr( k^-1 , l^ , m^ ), Δr( k^l^m^ ) and the distance interval Δr by interpolation (max) Determine.

[0076] Specifically, the three-stage interpolation performed in the first embodiment will be described with reference to Fig. 8. Fig. 8 is a diagram for explaining the interpolation method according to the first embodiment. The rectangular parallelepiped shown in Fig. 8 has eight vertices whose coordinates are the estimated seabed slope θ k^-1 and estimated seabed slope θ k^ , evaluated seafloor sound speed c l^-1 and estimated seafloor sound speed c l^ , and evaluation water depth d m^-1 and evaluation depth d m^ In other words, the dip of the bottom of the two vertices on the axis of the dip of the bottom of the sea is θ k^-1 and θ k^ The sub-bottom sound speed at the two vertices on the axis is c l^-1 and c l^ and the depths of the two vertices on the depth axis are d m^-1 and d m^ The points marked with an x ​​are the distance interval Δr (max) The point (θ,c(B) ,d).

[0077] In the first step shown in Figure 8(a), linear interpolation is performed on the seabed slope θ according to equations (16), (17), (18), and (19). The results calculated using equations (16), (17), (18), and (19) correspond to the four black dots shown in Figure 8(a).

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[0079]

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[0080]

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[0081]

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[0082] In the second stage shown in Figure 8(b), the sub-bottom sound speed c is calculated using equations (20) and (21). (B) The results calculated using equations (20) and (21) correspond to the two black dots shown in Figure 8(b).

[0083]

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[0085] In the third step, the water depth d is linearly interpolated using equation (22) to obtain the distance interval Δr (max)The result calculated by equation (22) corresponds to the point marked with an x ​​in Figure 8.

[0086]

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[0087] The linear interpolation of the above steps may be performed in a different order. For example, first the interpolation for the water depth d, then the sub-bottom sound speed c (B) The distance interval Δr can also be obtained by interpolating the distance θ and the seabed slope θ. (max) Furthermore, equations (16) to (22) are used to calculate the point (θ k ,c l ,d m ), but any interpolation method in multidimensional space that satisfies the required interpolation accuracy may be used.

[0088] Returning to FIG. 5, finally, the index calculation unit 15 calculates the distance interval Δr (max) Using the arbitrary seabed slope θ and sub-bottom sound speed c (B) The propagation loss TL(r,z) for the condition of water depth d is calculated according to equations (6), (3) and (2) (step S5).

[0089] As described above, according to the first embodiment, a plurality of candidate distance intervals that are candidates for the distance interval to be calculated are calculated based on the comparison result between the evaluation error of each of a plurality of evaluation distance intervals and the allowable error under each of a plurality of environmental conditions. Therefore, the information processing device 1, the information processing method, and the information processing program can calculate a distance interval that limits the overall error of the index calculated by the sound wave propagation calculation to the allowable value.

[0090] Although the first embodiment of the present invention has been described above, the present invention is not limited to the first embodiment described above, and various modifications and applications are possible within the scope of the gist of the present invention. For example, in the first embodiment, the distance interval determining unit 14 determines the seabed slope θ, the sub-sea sound speed c (B), and water depth d, distance intervals were determined. Here, if the section from the sound source to the receiver does not have a constant seabed slope, the distance interval determination unit 14 may divide the distance into sections that can be considered to have a constant seabed slope, and determine a distance interval for each of these distance sections. Figure 9 is a diagram illustrating a method of dividing the section from the sound source to the receiver into sections with a constant seabed slope, according to a modification of the first embodiment. As shown in Figure 9, a method can be adopted in which any seabed topography is approximated by straight lines of multiple sections while adding section boundaries one by one.

[0091] Specifically, as shown in Figure 9(a), when a virtual line IL is drawn between the sound source and the receiver, if there is a point where the depth of the virtual line IL (the dashed line in Figure 9) deviates from the actual depth of the seabed by more than a predetermined distance, it is determined that the section from the sound source to the receiver does not have a constant seabed slope. In this case, as shown in Figure 9(b), a new boundary BO1 of the virtual line is added at the point where the difference between the virtual line IL and the actual depth is greatest. As a result, in Figure 9(b), a virtual line IL1 from the sound source to boundary BO1 and a virtual line IL2 from boundary BO1 to the receiver are generated. The ranges of each virtual line correspond to the distance sections for which the distance intervals are calculated. Then, as shown in Figure 9(c), the virtual line is repeatedly divided until the maximum number of sections is reached or the deviation from the actual depth of the seabed slope for all virtual lines is less than the predetermined distance (i.e., all virtual lines in all distance sections are considered to have a constant seabed slope). In FIG. 9(c), the imaginary line IL1 is further divided by a boundary BO2 to generate imaginary lines IL1-1 and IL-2.

[0092] In addition, in the first embodiment, the "index" calculated by the sound wave propagation calculation is the propagation loss, and the "evaluation index" is the evaluated propagation loss. In other words, the distance interval Δr (max) However, depending on the application of the results of sound wave propagation calculation, it is necessary to determine the distance interval Δr so as to keep the error of sound pressure intensity below the allowable value. (max)Here, the sound pressure intensity is the square of the absolute value of the sound pressure p(r,z) calculated by equation (3), |p(r,z)| 2 In this case, the evaluation path loss TL calculated by the evaluation index calculation unit 11 is klm (s) (r0+jΔR s ,z n ) is evaluated as sound pressure p klm (s) (r0+jΔR s ,z n ), and the evaluation error ε klm (ΔR s ) can be calculated by replacing equations (13) and (14) with the following equations (23) and (24), respectively. 2 The distance interval Δr that suppresses the error of (max) In this example, the sound pressure intensity corresponds to the "index" required for the sound wave propagation calculation of the present disclosure, and the evaluated sound pressure corresponds to the "evaluation index" to be evaluated in the present disclosure.

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[0095] In the first embodiment, the error calculation unit 12 calculates the sum of all the depth indices n=1, 2, ..., N including the depth below the seabed for all the distance indices j=1, 2, ..., Js in the calculation formula (13) or (14) of the evaluation error. However, the PE model is often intended to calculate the underwater propagation loss. Therefore, when calculating the evaluation error with emphasis on the difference in underwater propagation loss, the range of n for which the sum is calculated is set to z. n ≦H j,s,k,m It is also possible to limit the range to where H j,s,k,m is the distance r0+jΔR s is the water depth at the

[0096]

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[0097] Then, for example, equation (13) can be rewritten as equation (26) below.

[0098]

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[0099] where N j,s,k,m is z n ≦H j,s,k,m Similarly, for equations (14), (23), and (24), n = 1, 2, ..., N j,s,k,m By rewriting it to take the sum of the underwater propagation loss, it is possible to calculate the evaluation error with emphasis on the difference in underwater propagation loss.

[0100] In addition, the error calculation unit 12 of the first embodiment calculates the reference propagation loss, that is, the evaluation propagation loss TL for the minimum evaluation distance interval ΔR1. (1) (r0+jΔR1,z n ), j=1,2,…,J1,n=1,2,…,N as the basis, the evaluation error ε klm (ΔR s However, the estimated propagation loss TL calculated using the PE method (1) (r0+jΔR1,z n ), j=1,2,…,J1,n=1,2,…,N, the propagation loss calculated using a sound wave propagation model other than the PE model is used as the reference propagation loss, and the evaluation error ε klm (ΔR s ) s = 1, 2, ..., S. In this case, the evaluation error ε klm (ΔR s ) is calculated. Also, the evaluation distance interval ΔR0≡0 is newly defined, and the evaluation error for the evaluation distance interval ΔR0 is calculated as ε klm(ΔR0)=0. Then, in the operation of the candidate calculation unit 13 in the first embodiment, the evaluation error ε klm (ΔR s ) and the allowable error ε. klm (ΔR s ) and the tolerance ε.

[0101] In addition, the larger the value of the allowable error ε used in the candidate calculation unit 13 of the first embodiment, the smaller the candidate distance interval Δr klm As a result, the distance interval Δr determined by the distance interval determination unit 14 becomes (max) will also increase, resulting in a larger error in propagation loss but a smaller amount of calculation. Conversely, the smaller the value of the allowable error ε, the smaller the error in propagation loss but the greater the amount of calculation. Therefore, multiple distance interval tables calculated in accordance with multiple different allowable error ε may be created in the storage device 21. In this case, by using multiple distance interval tables appropriately, it becomes possible to adjust the error and amount of calculation depending on the situation in which the sound wave propagation model is used. [Explanation of symbols]

[0102] 1, 9 Information processing device, 11 Evaluation index calculation unit, 12 Error calculation unit, 13 Candidate calculation unit, 14 Distance interval determination unit, 15 Index calculation unit, 21 Storage device, 91 Distance interval calculation unit, 92 Propagation loss calculation unit.

Claims

1. An information processing device that calculates a distance interval when calculating an index by sound wave propagation calculation, an evaluation index calculation unit that calculates an evaluation index for each combination of a plurality of environmental conditions and a plurality of evaluation distance intervals that are the plurality of distance intervals to be evaluated; an error calculation unit that calculates an evaluation error based on a difference between the evaluation index and a reference index for each combination of a plurality of the environmental conditions and a plurality of the evaluation distance intervals; a candidate calculation unit that calculates a plurality of candidate distance intervals to be candidates for the evaluation distance intervals based on a comparison result between the evaluation error and an allowable error for each of the plurality of evaluation distance intervals under each of the plurality of environmental conditions, and stores the candidate distance intervals in a storage device; a distance interval determination unit that determines, as the distance interval, the candidate distance interval that corresponds to the given environmental condition from the plurality of candidate distance intervals stored in the storage device. Information processing device.

2. The error calculation unit uses the evaluation index of the smallest evaluation distance interval among the plurality of evaluation distance intervals as the reference index. The information processing device according to claim 1 .

3. Among the plurality of evaluation distance intervals, the evaluation distance intervals other than the smallest evaluation distance interval are integer multiples of the smallest evaluation distance interval, The error calculation unit calculates the evaluation error based on statistics of the difference between the evaluation index of the evaluation distance interval other than the smallest evaluation distance interval and the evaluation index of the smallest evaluation distance interval obtained by multiplying the evaluation index by an integer. The information processing device according to claim 2 .

4. The candidate calculation unit calculates the maximum evaluation distance interval at which the evaluation error is equal to or smaller than the allowable error as the candidate distance interval.

4. The information processing device according to claim 1.

5. The evaluation index calculation unit calculates the evaluation index under a plurality of environmental conditions determined by a combination of an evaluation seabed slope, an evaluation seabed sound speed, and an evaluation water depth.

4. The information processing device according to claim 1.

6. The index is the propagation loss of the sound wave propagating from the sound source to the receiver.

4. The information processing device according to claim 1.

7. An information processing method of an information processing device that calculates a distance interval when calculating an index by sound wave propagation calculation, an evaluation index calculation step of calculating an evaluation index for each combination of a plurality of environmental conditions and a plurality of evaluation distance intervals, which are the plurality of distance intervals to be evaluated; an error calculation step of calculating an evaluation error based on a difference between the evaluation index and a reference index for each combination of a plurality of the environmental conditions and a plurality of the evaluation distance intervals; a candidate calculation step of calculating a plurality of candidate distance intervals to be candidates for the distance intervals based on a comparison result between the evaluation error and an allowable error for each of the plurality of evaluation distance intervals under each of the plurality of environmental conditions, and storing the candidate distance intervals in a storage device; a distance interval determination step of determining, as the distance interval, the candidate distance interval that corresponds to the given environmental condition from the plurality of candidate distance intervals stored in the storage device. Information processing methods.

8. An information processing program for calculating a distance interval when calculating an index by sound wave propagation calculation, an evaluation index calculation step of calculating an evaluation index for each combination of a plurality of environmental conditions and a plurality of evaluation distance intervals, which are the plurality of distance intervals to be evaluated; an error calculation step of calculating an evaluation error based on a difference between the evaluation index and a reference index for each combination of a plurality of the environmental conditions and a plurality of the evaluation distance intervals; a candidate calculation step of calculating a plurality of candidate distance intervals to be candidates for the distance intervals based on a comparison result between the evaluation error and an allowable error for each of the plurality of evaluation distance intervals under each of the plurality of environmental conditions, and storing the candidate distance intervals in a storage device; a distance interval determination step of determining, as the distance interval, the candidate distance interval that corresponds to the given environmental condition from the plurality of candidate distance intervals stored in the storage device, Information processing program.

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