Underwater detection device, fish shoal tracking method and program

Abstract

To provide an underwater detection device, fish shoal tracking method and program that can stably track echos of a fish shoal even under a condition subject to an impact of reverberation echos such as a sea surface reflection and the like.SOLUTION: An underwater detection device 10 comprises: a data generation unit 11a that forms a plurality of reception beams in a scan range on the basis of an electric signal output from a plurality of ultrasonic transducers 13a during a wave reception period after wave transmission timing, and generates data on echo intensity in each position of the scan range; and a fish shoal tracking unit 11b that updates a tracking area of a fish shoal on the basis of the data and sailing data on a movement of a vessel having an echo sounder transceiver 11 installed. The fish shoal tracking unit 11b is configured to determine whether data based on a fish shoal echo within the tracking area is used in updating the tracking area on the basis of a determination of whether an index value indicating how large echo intensity of an entire tracking area is relative to echo intensity around the tracking area is equal to or more than a prescribed threshold, or not.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an underwater detection device, a fish school tracking method in an underwater detection device, and a program for causing a computer to execute a function of tracking a school of fish. [Background technology]

[0002] Underwater detection devices that detect underwater targets are known in the art. These types of underwater detection devices transmit ultrasonic waves into the water, receive the reflected waves, calculate the echo intensity from each position in the water, and display a three-dimensional distribution of the echo intensity (echo image) on a screen.

[0003] For example, an underwater detection device transmits a wave from a transducer having multiple ultrasonic transducers and receives the reflected wave with the transducer. From the electrical signals output from each ultrasonic transducer of the transducer in response to the reception of the reflected wave, multiple reception beams are formed by beamforming, arranged in the circumferential direction on a cone surface with the position of the transducer as the apex. From the reception signals generated for each reception beam, an echo image according to the scanning range of the reception beam is generated and displayed.

[0004] The following Patent Document 1 describes a target image tracking device and a target image tracking method that are applied to a scanning sonar, a fish finder, or a radar device. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5303284 Summary of the Invention [Problem to be solved by the invention]

[0006] The method of Patent Document 1 can be applied to tracking a mass of fish (single school) with clear boundaries. However, when an underwater detection device detects a single school near the sea surface from a distance, the detection range is one with a tilt angle of about 0°. For this reason, reverberation echoes such as waves reflected from the sea surface (sea surface reflection) may be distributed over a wide range that includes the range of echoes from the single school (single school echoes).

[0007] Under such conditions, the boundary between the single echo and the reverberation echo may become unclear, or the reverberation echo may cover the single echo. The target tracking method described in the above Patent Document 1 does not take into account the influence of reverberation echoes such as sea surface reflection.

[0008] In view of such problems, the present invention aims to provide an underwater detection device, a fish tracking method, and a program that are capable of stably tracking fish school echoes even under conditions affected by reverberation echoes such as sea surface reflections. [Means for solving the problem]

[0009] The first aspect of the present invention relates to an underwater detection device. The underwater detection device according to this aspect includes a transmission processing unit that transmits ultrasonic waves at a transmission timing at a predetermined interval to a plurality of ultrasonic transducers included in a transducer installed on the bottom of a ship, a data generating unit that forms a plurality of reception beams in a scanning range based on electric signals output from the plurality of ultrasonic transducers during a reception period after the transmission timing, and generates data on the echo intensity at each position in the scanning range, and a fish school tracking unit that updates a tracking area of ​​a school of fish based on the data and navigation data on the movement of a ship on which the transducer is installed. The fish school tracking unit determines whether or not to use the data based on the fish school echoes in the tracking area for updating the tracking area based on whether or not an index value indicating how large the echo intensity of the entire tracking area is relative to the echo intensity around the tracking area is equal to or larger than a predetermined threshold value.

[0010] When the index value is small, there is a high probability that reverberation echoes that are as strong as or stronger than the echoes of the school of fish are distributed over a wide area including the tracking area. In such a situation, the echoes of the school of fish blend in with the reverberation echoes and are difficult to distinguish from the reverberation echoes. Therefore, if data based on the echoes of the school of fish is used to update the tracking area in this state, the updated tracking area will be significantly affected by the reverberation echoes, making it difficult to update the tracking area properly. In contrast, the underwater detection device of this embodiment avoids using data based on the echoes of the school of fish to update the tracking area in such a situation. Therefore, the tracking area can be updated properly.

[0011] In the underwater detection device of the present embodiment, the fish school tracking unit may be configured to update the tracking area based on the data based on the fish school echoes and the navigation data when the index value is greater than or equal to the threshold value, and to update the tracking area based on the navigation data without using the data based on the fish school echoes when the index value is less than the threshold value.

[0012] According to this configuration, when the index value is equal to or greater than a predetermined threshold, i.e., when the influence of reverberation echo on the fish school echo within the tracking area is small, the tracking area is updated based on the data based on the fish school echo and the navigation data. Therefore, the tracking area can be updated appropriately. On the other hand, when the index value is less than the predetermined threshold, i.e., when the influence of reverberation echo on the fish school echo within the tracking area is large, the tracking area is updated based on the navigation data without using the data based on the fish school echo. Therefore, the tracking area including the school of fish to be tracked can be smoothly set based on the navigation data until the influence of reverberation echo decreases.

[0013] In the underwater detection device of the present embodiment, the fish school tracking unit can be configured to calculate, as the index value, a reverberation contrast indicating the degree to which reverberation echoes having an echo intensity equal to or greater than the echo intensity within the tracking area are distributed over a wide area including the tracking area, and to make the judgment based on the reverberation contrast.

[0014] According to this configuration, the influence of reverberation echoes on fish school echoes can be evaluated by the reverberation contrast, and based on this evaluation, it can be determined whether or not data based on the fish school echoes should be used to update the tracking area.

[0015] In this configuration, the reverberation contrast may be calculated by a first average value of the data within the tracking region and a second average value of the data around the tracking region.

[0016] This allows the echo intensity of the entire tracking area to be obtained as a first average value, and the echo intensity around the tracking area to be obtained as a second average value.

[0017] In this case, the reverberation contrast may be calculated by dividing the first average value by the second average value.

[0018] This makes it possible to appropriately evaluate, by using the reverberation contrast, whether reverberation echoes that are as strong as or stronger than the fish school echoes are distributed over a wide area including the tracking area.

[0019] In the aforementioned configuration, the reverberation contrast can be calculated so as to be smaller as the degree of the distribution is higher.

[0020] In this case, the fish school tracking unit can be configured to set a reverberation threshold to be compared with the reverberation contrast as the threshold, and if the reverberation contrast is greater than or equal to the reverberation threshold, to set the tracking area to be applied at the next transmission timing based on the data based on the fish school echoes and the navigation data, and if the reverberation contrast is less than the reverberation threshold, to set the tracking area to be applied at the next transmission timing based on the navigation data without using the data based on the fish school echoes.

[0021] According to this configuration, when the reverberation contrast is equal to or greater than the reverberation threshold, i.e., when the reverberation echoes that are as strong as or stronger than the fish school echoes are distributed over a wide area including the tracking area to a low extent, the tracking area to be applied to the next wave transmission timing is set based on the data based on the fish school echoes and the navigation data. Therefore, the tracking area to track the fish school echoes can be set appropriately based on the amplitude data. On the other hand, when the reverberation contrast is less than the reverberation threshold, i.e., when the reverberation echoes that are as strong as or stronger than the fish school echoes are distributed over a wide area including the tracking area to a high extent, the tracking area to be applied to the next wave transmission timing is set based on the navigation data without using the data based on the fish school echoes. Therefore, it is possible to prevent the updated tracking area from being significantly affected by the reverberation echoes, and it is possible to smoothly set the tracking area to track the fish school echoes based on the navigation data until the influence of the reverberation echoes decreases.

[0022] In the underwater detection device of this embodiment, the fish school tracking unit can be configured to estimate the fish school area, which is the area of ​​the fish school echo, based on the data within the tracking area, and if the index value is greater than or equal to the threshold value, expand the fish school area by a predetermined magnification to form a new tracking area, correct the new tracking area to a position based on the position of the transducer at the next wave transmission timing based on the navigation data, and set it as the tracking area to be applied at the next wave transmission timing, and if the index value is less than the threshold value, correct the current tracking area to a position based on the position of the transducer at the next wave transmission timing based on the navigation data, and set it as the tracking area to be applied at the next wave transmission timing.

[0023] According to this configuration, the tracking area is corrected to a position based on the position of the transducer after the movement according to the movement of the ship, so that the tracking area can be appropriately applied at each transmission timing.

[0024] In this configuration, the fish school tracking unit may be configured to change the magnification used to enlarge the fish school area so that the magnification becomes larger as the index value becomes larger.

[0025] According to this configuration, the size of the new tracking region can be appropriately adjusted according to the distribution state of the reverberation echo.

[0026] In addition, the underwater detection device of this embodiment may be configured to include a fish quantity index calculation unit that calculates a fish quantity index based on the data within the fish school area, and an image generation unit that generates a display image including information regarding the fish quantity index.

[0027] According to this configuration, the fish quantity index of the school of fish tracked by the school of fish tracking unit can be updated and displayed as needed, allowing the user to smoothly grasp the fish quantity index of the school of fish being tracked.

[0028] In the underwater detection device of this embodiment, the fish school tracking unit can be configured to calculate a fish school contrast indicating the likelihood that a fish school echo is contained within the tracking area based on the data within the tracking area and the data around the tracking area, and if the fish school contrast is greater than or equal to a predetermined fish school threshold, to perform an update process of the tracking area based on the index value, and if the fish school contrast is less than the fish school threshold, to set the tracking area to be applied at the next transmission timing based on the navigation data without performing an update process of the tracking area based on the index value.

[0029] According to this configuration, when the fish school contrast is less than the fish school threshold, i.e., when the reverberation echoes that are as strong as or stronger than the fish school echoes are highly likely to be distributed over a wide area including the tracking area, the update process of the tracking area based on the index value is omitted, and the tracking area to be applied at the next wave transmission timing is set from the navigation data. Therefore, the process is simplified and the tracking area can be appropriately updated.

[0030] In this configuration, the fish school tracking unit may be configured to calculate the fish school contrast based on the maximum value of the data within the tracking area and the median value of the data surrounding the tracking area.

[0031] With this configuration, it is possible to properly calculate the fish school contrast, which indicates the likelihood that the tracking area contains fish school echoes that can be distinguished from reverberation echoes.

[0032] In addition, in this configuration, when the fish school contrast is less than a predetermined fish school threshold, the image generation unit may be configured to continue displaying the information regarding the fish quantity index that was displayed at the previous transmission timing without updating the information regarding the fish quantity index.

[0033] This configuration makes it possible to prevent information about low-precision fish quantity indexes calculated in a state where reverberation echoes that are as strong as or stronger than the fish school echoes are distributed over a wide area including the tracking area from being displayed and presented to the user, thereby improving the reliability of the information about fish quantity indexes visually recognized by the user.

[0034] A second aspect of the present invention relates to a method for tracking a school of fish in an underwater detection device, which includes the steps of: transmitting ultrasonic waves at a predetermined interval from a plurality of ultrasonic transducers included in a transducer installed on the bottom of a ship; forming a plurality of receiving beams in a scanning range based on electric signals output from the plurality of ultrasonic transducers during a receiving period after the transmitting timing, and generating data on echo intensity at each position in the scanning range; and updating a tracking area of ​​a school of fish based on the data and navigation data on the movement of a ship on which the transducer is installed. The step of updating the tracking area includes a step of determining whether or not to use the data based on the echoes of the school of fish in the tracking area for updating the tracking area based on whether or not an index value indicating how large the echo intensity of the entire tracking area is relative to the echo intensity around the tracking area is equal to or larger than a predetermined threshold value.

[0035] The fish school tracking method according to this aspect has the same effects as the first aspect.

[0036] A third aspect of the present invention is a program for causing a computer of an underwater detection device to execute a predetermined function. The program according to this aspect causes the computer to execute the following functions: transmit ultrasonic waves at a predetermined interval to a plurality of ultrasonic transducers included in a transducer installed on the bottom of a ship; form a plurality of receiving beams in a scanning range based on electric signals output from the plurality of ultrasonic transducers during a receiving period after the transmission timing, generate data on echo intensity at each position in the scanning range; and update a tracking area of ​​a school of fish based on the data and navigation data on the movement of a ship on which the transducer is installed. The function of updating the tracking area includes a function of determining whether or not to use the data based on the echoes of the school of fish within the tracking area for updating the tracking area based on whether or not an index value indicating how large the echo intensity of the entire tracking area is relative to the echo intensity around the tracking area is equal to or larger than a predetermined threshold value.

[0037] According to the program of this aspect, the same effects as those of the first aspect can be achieved. Effect of the Invention

[0038] As described above, according to the present invention, it is possible to provide an underwater detection device, a fish tracking method, and a program that are capable of stably tracking fish school echoes even under conditions affected by reverberation echoes such as sea surface reflections.

[0039] The effects and significance of the present invention will become clearer from the following description of the embodiment. However, the embodiment described below is merely an example of how the present invention can be put into practice, and the present invention is not limited to the embodiment described below. [Brief description of the drawings]

[0040] [Figure 1] FIG. 1 is a diagram showing a schematic view of underwater exploration by an underwater detection device according to an embodiment. [Diagram 2]FIG. 2 is a diagram showing a schematic view of underwater exploration by an underwater detection device according to an embodiment. [Diagram 3] FIG. 3 is a block diagram showing the configuration of an underwater detection device according to an embodiment. [Figure 4] FIG. 4 is a diagram for explaining a method for calculating a fish quantity index according to an embodiment. [Diagram 5] FIG. 5 is a diagram illustrating an example of an echo image displayed on a display unit according to the embodiment. [Figure 6] FIG. 6 is a flowchart showing a process for generating data regarding echo intensity according to the embodiment. [Figure 7] FIG. 7 is a flowchart showing a fish school tracking process according to the embodiment. [Figure 8] FIG. 8 is a diagram showing a method for setting a fish school region according to an embodiment. [Figure 9] FIG. 9 is a diagram showing an example of setting a fish school area relative to a tracking area (actual measurement) according to the embodiment. [Figure 10] FIG. 10 is a diagram illustrating a method for calculating a reverberation contrast according to an embodiment. [Figure 11] FIG. 11 is a diagram showing a distribution state of volume scattering intensity when the reverberation contrast is relatively large according to the embodiment. [Figure 12] FIG. 12 is a diagram showing a distribution state of volume scattering intensity when the reverberation contrast is relatively small according to the embodiment. [Figure 13] FIG. 13 is a diagram showing an example of a display image including information related to the fish quantity index according to the embodiment. [Figure 14] FIG. 14 is a graph showing an example of a method for setting an enlargement magnification when a fish school area is enlarged to form a new tracking area according to an embodiment. [Figure 15] FIG. 15 is a flowchart showing a fish school tracking process according to the first modified example. [Figure 16] FIG. 16 is a flowchart showing a display process for information related to fish quantity indexes according to the first modified example. [Figure 17]FIG. 17 is a flowchart showing a fish school tracking process according to the second modified example. [Figure 18] FIG. 18 is a flowchart showing a tracking process for another school of fish according to the second modification. [Figure 19] FIG. 19 is a diagram showing an example of a display image including information related to the fish quantity index according to another modified example. [Figure 20] FIG. 20 is a diagram showing an example of a display image including information related to the fish quantity index according to another modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0041] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. For convenience, the drawings appropriately include X, Y, and Z axes that are perpendicular to each other. The X-axis and Y-axis directions are horizontal, and the Z-axis direction is vertical. The positive X-axis direction is the direction in which the ship advances.

[0042] 1 and 2 are diagrams that show a schematic diagram of underwater searching by an underwater detection device 10. FIG.

[0043] In FIG. 1 and FIG. 2, θ is the azimuth angle centered on the transducer 13 installed on the bottom of the ship S1, and φ is the tilt angle of a scanning plane SP1 (to be described later) with respect to the horizontal plane (XY plane).

[0044] The underwater detection device 10 includes a transducer 13 installed on the bottom of a ship S1 such as a fishing boat. The underwater detection device 10 transmits a pulse of sound waves (transmission pulse) from the transducer 13, and receives sound waves (echoes) reflected (backscattered) by objects such as fish present in the water by the same transducer 13. The underwater detection device 10 detects objects present in the water based on the echoes received by the transducer 13.

[0045] The transducer 13 is equipped with a large number of ultrasonic transducers. When transmitting, each ultrasonic transducer converts an input electrical signal into a sound wave and emits it, and when receiving, it converts the incident sound wave into an electrical signal and outputs it. Typically, the transducer 13 is cylindrical, with several hundred ultrasonic transducers regularly arranged on its side.

[0046] Here, the area to be detected by the underwater detection device 10 is a conical surface. The axis of this conical surface coincides with the central axis (here, the Z-axis) of the transducer 13. This conical surface is called the scanning surface SP1, and the apex and axis of this scanning surface SP1 are called the origin and the scanning axis, respectively. The origin coincides with the position of the transducer 13, and the scanning axis extends vertically downward from this origin. Here, the scanning axis coincides with the Z-axis. The angle that the scanning surface SP1 makes with the horizontal plane (XY plane) is the tilt angle φ described above.

[0047] As shown in Fig. 1, the underwater sounding device 10 transmits a transmission beam TB1 having maximum intensity on the scanning plane SP1 over the entire circumference during transmission. This transmission beam TB1 has an intensity distribution symmetrical with respect to the scanning axis (Z-axis in Fig. 1), and its width in the vertical direction is relatively narrow.

[0048] 2, the underwater detection device 10 forms multiple reception beams RB1 with maximum sensitivity on the scanning plane SP1 during wave reception. The reception beam RB1 is formed by performing beamforming processing on the electrical signals output from multiple ultrasonic transducers arranged in the transducer 13.

[0049] Each receiving beam RB1 is a pencil beam that is narrow in both the vertical and horizontal directions and has the same directivity. A straight line that passes through the origin and faces the direction in which the sensitivity of the receiving beam RB1 is maximum is the beam axis of each receiving beam RB1. Multiple receiving beams RB1 are formed side by side at regular angular intervals (azimuth angle resolution) in the azimuth angle θ direction all around the scanning plane SP1. The underwater detection device 10 converts the strength of the sound waves received by each receiving beam RB1 into color and displays it as an image (echo image).

[0050] FIG. 3 is a block diagram showing the configuration of the underwater detection device 10. As shown in FIG.

[0051] The underwater detection device 10 comprises a control unit 11, a memory unit 12, a transducer 13, a transmission processing unit 14, a reception processing unit 15, a transmission / reception switching unit 16, a display unit 17, a display processing unit 18, an input unit 19, and an input processing unit 20. The transducer 13 is installed on the bottom of the ship S1 as described above, and the other components such as the control unit 11 are installed in the wheelhouse or the like of the ship S1.

[0052] The control unit 11 includes an arithmetic processing circuit (computer) such as a CPU (Central Processing Unit), and executes the control processing described below according to a program stored in the storage unit 12. The storage unit 12 includes storage media such as a ROM (Read Only Memory), a RAM (Random Access Memory), and a hard disk. The storage unit 12 stores programs for the control unit 11 to execute the control processing.

[0053] As described above, the transducer 13 includes a plurality of ultrasonic transducers 13a. In each transmission and reception period (ping), the transducer 13 transmits an ultrasonic wave as the transmission beam TB1 in FIG. 1, and receives the reflected wave by each ultrasonic transducer.

[0054] The transmission processing unit 14 outputs a transmission signal for transmitting ultrasonic waves to the transducer 13 via the transmission / reception switching unit 16 in response to control from the control unit 11. The transmission signal is a signal that vibrates at a predetermined amplitude for a fixed period of time, as shown in FIG. 3. During one transmission of the transmission beam TB1, this transmission signal is supplied to each ultrasonic transducer 13a of the transducer 13 via the transmission / reception switching unit 16. As a result, ultrasonic waves corresponding to the transmission signal are transmitted from each ultrasonic transducer 13a, as shown in FIG. 3. The ultrasonic pulse transmitted during one transmission is called a transmission pulse.

[0055] The reception processing unit 15 receives the electrical signals output by the ultrasonic transducers 13a of the transducer 13 upon receiving the reflected ultrasonic waves via the transmission / reception switching unit 16, and performs amplification and noise removal (band pass filter) processing on the received electrical signals. The reception processing unit 15 outputs the electrical signals that have been subjected to these processes to the control unit 11.

[0056] When transmitting the transmission beam TB1, the transmit / receive switching unit 16 outputs the transmission signal output from the transmission processing unit 14 to the transmitter / receiver 13 (ultrasonic transducer 13a), and outputs the electrical signal output from the transmitter / receiver 13 (ultrasonic transducer 13a) to the reception processing unit 15 for a certain period of time from the timing when the transmission of the transmission beam TB1 is completed.

[0057] 3, one each of the transmission processing unit 14 and the reception processing unit 15 is illustrated, but the above-mentioned processing in the transmission processing unit 14 and the reception processing unit 15 is performed for each individual ultrasonic transducer 13a arranged in the transducer 13. Therefore, the electrical signals output from each ultrasonic transducer 13a are amplified and subjected to noise removal processing, and the electrical signals are individually input to the control unit 11. When these electrical signals are input to the control unit 11, they are converted by an A / D converter into digital signals with a predetermined sampling period.

[0058] The display unit 17 includes a display such as a liquid crystal display. The display processing unit 18 causes the display unit 17 to display a predetermined image in response to control from the control unit 11. The input unit 19 includes input means such as operation keys and a mouse. The input processing unit 20 outputs a signal corresponding to an operation on the input unit 19 to the control unit 11 in response to control from the control unit 11. The display unit 17 and the input unit 19 may be configured by a liquid crystal panel in which a touch panel is superimposed on a liquid crystal display.

[0059] In this embodiment, the program stored in the storage unit 12 provides the control unit 11 with the functions of a data generation unit 11a, a fish school tracking unit 11b, a fish quantity index calculation unit 11c, and an image generation unit 11d.

[0060] The data generating unit 11a performs beamforming on the electric signals (digital signals) output from each ultrasonic transducer 13a to form the receiving beam RB1 in Fig. 2, and generates receiving signals corresponding to sound waves incident on the transducer 13 from the beam axis direction (the direction of a predetermined azimuth angle θ and tilt angle φ) of each receiving beam RB1. Furthermore, the data generating unit 11a performs band limiting and envelope detection processing on the receiving signals in each beam axis direction to obtain envelope signals in each beam axis direction.

[0061] Here, the band limiting process is a process for extracting frequency components of the transmission signal output from the transmission processing unit 14. This process is performed when the transmission signal output from the transmission processing unit 14 is a signal with a constant frequency (CW signal).

[0062] On the other hand, when the transmission signal output from the transmission processing unit 14 is not a constant frequency signal (CW signal) but a frequency modulated chirp signal (FM signal), the data generating unit 11a performs matched filter processing on the received signal in each beam axis direction instead of band limiting processing.Then, the data generating unit 11a performs envelope detection processing on the signal after the matched filter processing to obtain the envelope signal in each beam axis direction.

[0063] The envelope signal thus acquired is a signal indicating echo intensity (sound wave strength) that changes according to the time elapsed from the transmission timing of the transmission beam TB1 (ultrasound wave). Here, the time elapsed from the transmission timing corresponds to the distance from the transducer 13 in each beam axis direction. The control unit 11 acquires the echo intensity from each distance position in each beam axis direction from the echo signal of each reception beam RB1 by associating the time elapsed from the transmission timing with the distance. The echo intensity is acquired with a predetermined distance resolution according to the sampling period. The data generation unit 11a acquires digital data (non-negative real number) according to the amplitude of the envelope signal at each sampling timing (distance) as amplitude data.

[0064] The data generator 11a executes the above-mentioned process during the reception period after the transmission of the ultrasonic waves to generate a series of amplitude data. The operation of transmitting an ultrasonic wave and receiving the echo generated by the transmission during the reception period thereafter is called a ping. A series of amplitude data is generated for each ping.

[0065] The fish school tracking unit 11b tracks the school of fish based on the amplitude data generated by the data generating unit 11a. More specifically, the fish school tracking unit 11b updates the initial tracking area set by the user for each ping based on the amplitude data and navigation data (ship speed, heading) from the navigation equipment.

[0066] If the user finds an echo of a school of fish that the user wants to track (single school echo) on the echo image displayed on the display unit 17, the user specifies the area via the input unit 19. For example, the user specifies the center position of the single school echo on the echo image. This sets an area of ​​a predetermined size centered on this center position as the initial tracking area. However, the method of setting the initial tracking area is not limited to this.

[0067] The fish school tracking unit 11b updates the initial tracking area thus set based on the amplitude data and navigation data (ship speed, ship heading) of the current ping so as to track the school of fish, and sets the updated tracking area in the next ping. In the next ping, the updated tracking area is further updated based on the amplitude data and navigation data (ship speed, ship heading) of the next ping. In this way, the fish school tracking unit 11b updates the tracking area for each ping.

[0068] Furthermore, the fish school tracking unit 11b estimates the fish school area in which the fish school exists from the amplitude data within the tracking area for each ping. The fish school tracking unit 11b then sets the tracking area for the next ping based on an area obtained by enlarging the estimated fish school area by a predetermined magnification. The fish school tracking process will be described later with reference to FIG. 7. Furthermore, the method of setting the fish school area will be described later with reference to FIG. 8.

[0069] The fish quantity index calculation unit 11c calculates a fish quantity index that can be an index of the total weight of fish contained in the fish school area based on the amplitude data in the fish school area. Various methods can be used to calculate the fish quantity index. For example, the fish quantity index may be calculated by the calculation method described in Japanese Patent Application No. 2023-116287 previously filed by the applicant. In this case, the fish quantity index Q is calculated by the following formula.

[0070]

number

[0071] FIG. 4 is a diagram for explaining a method for calculating the fish quantity index Q based on the above formula (1).

[0072] Here, an orthogonal coordinate system is defined in which the horizontal axis represents the beam number and the vertical axis represents the sample number.

[0073] The beam number is a number assigned to the receiving beam RB1. For example, the beam number j of the receiving beam RB1 facing the stern direction in a plan view is assigned 0, and further, the beam number j of each receiving beam RB1 is assigned 1, 2, 3, ... in order of increasing angle between the stern direction (reference direction) and the beam axis direction, with the clockwise direction in a plan view being positive. In this case, if the total number of receiving beams RB1 is 128, the beam numbers j of the receiving beams RB1 facing the port direction, bow direction, and starboard direction are 32, 64, and 96, respectively.

[0074] Moreover, the sample number indicates the order in which the envelope signal corresponding to each receive beam is sampled. The sample number corresponds to the distance from the origin (the position of the transducer 13). A sample number n is assigned to each sampling time of the envelope signal in chronological order. The start time of transmission of the transmission beam TB1, i.e., the moment when the leading edge of the transmission pulse is emitted from the transducer 13, is set as the reference time, and the sample number n at this time is set to 0.

[0075] In equation (1), A(j,n) is the amplitude data at the position of beam number j and sample number n. r0 is the unit distance and is defined as 1 m. n is the time t when the nth amplitude data is sampled. n is the distance from the origin of the position corresponding to (unit: m). α is the absorption coefficient (attenuation of sound wave per unit distance, unit: dB / m).

[0076] When the fish school area A1 is set in a Cartesian coordinate system as shown in FIG. 4, the calculations in the parentheses of formula (1) are performed for the group of amplitude data A(j,n) included in this fish school area A1, and the sum of these calculation results is calculated. Then, C0, C cor , 1 / V unit is multiplied to calculate the fish abundance index Q.

[0077] Coefficient V unit is called the point spread coefficient. When there is one target on the scan plane SP1, normalized amplitude data A'(j,n) caused by this target occurs behind the target (upper side in FIG. 4) in the Cartesian coordinate system of FIG. 4. The normalized amplitude data A'(j,n) is expressed by the following equation. In the following equation, I0 is the intensity of the transmitted pulse (unit: micropascal squared).

[0078]

number

[0079] Here, the target strength T s is 1, the maximum value of the normalized amplitude data A'(j,n) caused by this target is 1. The sum of the squared values ​​of the normalized amplitude data A'(j,n) is the point spread coefficient V unit It is.

[0080] The coefficient C0 is calculated by the target strength Ts and weight W of a single fish, the intensity of the transmitted pulse I0, and the receiving sensitivity k of the device, as follows: W / (2I0·k 2 T s ) for a representative fish.s and the design values ​​of I0 and k for the underwater detection device 10, or it may be a value calculated in advance so that the fish abundance index Q closely matches the catch amount estimated by the fishermen or the actual catch amount.

[0081] Coefficient C cor is the fish volume correction coefficient. This fish volume correction coefficient C cor The fish quantity correction factor C is reflected by a fish quantity correction factor input by a user such as a fisherman. Until the fish quantity correction factor is input for the first time, the fish quantity index calculation unit 11c uses the fish quantity correction factor C cor The fish quantity index calculation unit 11c sets the initial value of 1 to the fish quantity correction coefficient C cor The value of is updated according to the following formula:

[0082] “New C cor ” = “Fish amount correction magnification” × “Old C cor "

[0083] That is, the fish quantity index calculation unit 11c calculates the fish quantity correction coefficient C immediately before the correction magnification is input. cor The new fish volume correction coefficient C is calculated by multiplying the fish volume correction factor by cor The fish abundance index Q is calculated as follows.

[0084] In order to reduce the difference between the displayed fish quantity index Q and the amount of fish actually caught, the user inputs a fish quantity correction factor via the input unit 19. In this way, the fish quantity correction factor input by the user is used as the fish quantity correction coefficient C cor By reflecting the fish quantity index Q in the calculation formula (1), the fish quantity index Q can be corrected to approach the actual catch amount based on the input fish quantity correction factor. Therefore, by repeatedly inputting the fish quantity correction factor, the fish quantity index Q can be brought closer to the fish quantity according to the user's rough estimate. Therefore, the fish quantity index Q according to the user's fishing ground, fish species, and season can be displayed smoothly and appropriately on the display unit 17.

[0085] The method of calculating the fish quantity index is not limited to the above, and for example, the method described in JP 2009-300220 A may be used.

[0086] Returning to Fig. 3, the image generator 11d generates an echo image that displays the echo intensity from each distance position in each beam axis direction on a predetermined color scale. The image generator 11d sequentially outputs the echo images generated for each ping to the display processor 18. As a result, the echo images updated for each ping are displayed on the display unit 17. In addition, the image generator 11d generates a display image including information on the fish quantity index, as described below.

[0087] FIG. 5 is a diagram showing a schematic example of an echo image displayed on the display unit 17. As shown in FIG.

[0088] In the mode for displaying echo images, the screen of the display unit 17 is divided into regions A11 and A12 on the left and right. Of these, an echo image P10 is displayed in region A11. Here, the echo image P10 is displayed as an image of the ship S1 as viewed from directly above. An image P11 of the ship S1 is placed in the center of the echo image P10, and further, a track P12 of the ship S1 thus far is shown. Also, a straight line P13 indicating the bow direction of the ship is included in the echo image P10.

[0089] Furthermore, in the echo image P10, a range at a certain distance from the position of the ship (image P11) is indicated by circular boundaries P14, P15, and P16. The diameters of the boundaries P14, P15, and P16 are, for example, 200 m, 400 m, and 600 m. In the echo image P10, the above-mentioned echo intensity is displayed using a predetermined color scale. For convenience, the range where the echo intensity is high is hatched in FIG. 5. For example, the hatched range P17 is the range where the echo intensity is high. The hatched range is the range where a school of fish may exist.

[0090] Area A12 is divided vertically into a number of areas, and each divided area displays information indicating the current position of ship S1 (longitude, latitude), the water temperature at the current position, and a graph showing the change in water temperature over time. Additionally, information relating to the fish quantity index calculated by fish quantity index calculation unit 11c is displayed in one of the divided areas of area A12. This information is updated for each ping. For the sake of convenience, the display of these images in area A12 has been omitted in FIG. 5.

[0091] FIG. 6 is a flowchart showing a process for generating data regarding echo intensity.

[0092] The process of Fig. 6 is executed by the control unit 11 mainly by the function of the data generating unit 11a. The process of one ping is shown in Fig. 6. The control unit 11 executes the process of Fig. 6 for each ping.

[0093] The control unit 11 causes the multiple ultrasonic transducers 13a included in the transducer 13 to transmit ultrasonic waves at a transmission timing at a predetermined interval (S11). The control unit 11 forms multiple reception beams RB1 in a scanning range (scanning plane SP1) with the position of the transducer 13 as the origin based on electrical signals output from the multiple ultrasonic transducers 13a during a reception period after the transmission timing, and generates data on echo intensity at each position (position defined by the azimuth angle of each reception beam RB1 and the distance from the origin) of the scanning range (scanning plane SP1) (S12). Here, as data on echo intensity, amplitude data is generated as described above.

[0094] FIG. 7 is a flowchart showing the processing for tracking a school of fish.

[0095] 7, the processes of steps S102, S103, and S105 to S110 are executed by the function of the fish school tracking unit 11b, and the process of step S104 is executed by the function of the fish quantity index calculation unit 11c. In the following, the description will be given on the assumption that the control unit 11 executes each process by these functions.

[0096] When the user specifies the area of ​​the school of fish to be tracked (initial tracking area) on the echo image P10 shown in Fig. 5 via the input unit 19 and performs an operation to start tracking, the control unit 11 judges whether the current ping is the first ping after tracking has started (S101). If the current ping is the first ping (S101: YES), the control unit 11 sets the initial tracking area A0 (S102), and further sets the school of fish area A1 from the amplitude data within the set initial tracking area A0.

[0097] FIG. 8 is a diagram showing a method for setting the fish school area A1.

[0098] The tracking area A0 is expanded in the Cartesian coordinate system of Fig. 8. This Cartesian coordinate system is similar to the Cartesian coordinate system of Fig. 4. The tracking area A0 is defined by the parameters of a width W01 parallel to the horizontal axis, a width W02 parallel to the vertical axis, and a center point C01. The width W01 corresponds to the angular width in the azimuth direction, and the width W02 corresponds to the length in the range direction.

[0099] The control unit 11 calculates the volume scattering strength SV for each amplitude data included in the tracking area A0. Sound waves attenuate according to distance due to spherical diffusion and absorption. Due to this attenuation, the amplitude data also decreases according to distance. The volume scattering strength SV is the reflectance per unit volume of the echo source (fish school or plankton school), and is obtained by correcting the amplitude data to compensate for this attenuation.

[0100] The control unit 11 adds up the volume scattering intensities SV within the width W02 for each column of the beam number j included in the width W01 to obtain a sum S of the volume scattering intensities SV. θ In FIG. 8, below the tracking area A0, the sum S obtained for each beam number j is calculated. θ An example of (j) is shown in the waveform. The straight line below the waveform represents the sum S θ (j) indicates the level of 0. Strictly speaking, the sum S θ (j) will be scattered, but for convenience, we will use the sum of these S θ A waveform is shown by connecting the plots in (j) with a curve.

[0101] The control unit 11 adds up the volume scattering intensities SV within the width W01 for each row of sample number n included in the width W02 to obtain a sum S of the volume scattering intensities SV. r In FIG. 8, the sum S(n) obtained for each sample number n is calculated on the right side of the tracking area A0. r An example of (n) is shown in the waveform. The straight line to the right of the waveform is the sum S r (n) indicates the level of 0. Strictly speaking, the sum S for each sample number n r (n) will be scattered, but for convenience, we will use the sum of these S r A waveform is shown by connecting the plots of (n) with a curve.

[0102] The control unit 11 calculates the sum S θ The control unit 11 extracts the maximum value MAX1 of (j) and sets the value obtained by multiplying the maximum value MAX1 by a predetermined magnification (for example, 0.1) as the threshold value TH1. r The maximum value MAX2 of (n) is extracted, and the value obtained by multiplying this maximum value MAX2 by a predetermined magnification (for example, 0.1) is set as the threshold value TH2. Here, the magnification is set to a value that allows the volume scattering intensity SV from the school of fish to be extracted while being distinguished from noise, etc. The magnification is set to an appropriate value based on actual measurement.

[0103] Of the waveform shown below tracking area A0, the portion that continuously takes values ​​equal to or greater than threshold TH1 is called a peak, and of the waveform shown to the right of tracking area A0, the portion that continuously takes values ​​equal to or greater than threshold TH2 is called a peak.

[0104] The control unit 11 sets the horizontal width range of the waveform of the crest including the maximum value MAX1 among the crests on the waveform shown below the tracking area A0 to the width W11 in the horizontal axis direction (azimuth direction) of the fish school area A1. More specifically, the range between the beam number j closest to one boundary of this horizontal width range and the beam number j closest to the other boundary is set to the width W11 in the horizontal axis direction (azimuth direction) of the fish school area A1. In this case, if there is a crest waveform outside the range of the crest waveform including the maximum value MAX1, the horizontal width range including the crest waveform from the crest waveform including the maximum value MAX1 to a predetermined number may be set to the width W11 in the horizontal axis direction (azimuth direction) of the fish school area A1. In this case, the range between the beam numbers j closest to the two boundaries of this horizontal width range is set to the width W11 in the horizontal axis direction (azimuth direction) of the fish school area A1.

[0105] Similarly, in the vertical axis direction (distance direction), the control unit 11 sets the width W12 in the vertical axis direction (distance direction) of the fish school area A1 based on the peak waveform on the waveform shown to the right of the tracking area A0.

[0106] Furthermore, the control unit 11 sets the center point C11 of the rectangular fish school area A1 defined by the widths W11 and W12. This completes the setting of the fish school area A1. The fish school area A1 is defined by the parameters of the width W11, width W12, and center point C11. The width W11 corresponds to the angular width in the azimuth direction, and the width W12 corresponds to the length in the distance direction.

[0107] FIG. 9 is a diagram showing an example of setting (actual measurement) of a fish school area A1 relative to a tracking area A0.

[0108] FIG. 9 shows a Cartesian coordinate system with the horizontal axis set to the azimuth angle θ (corresponding to beam number j) and the vertical axis set to the distance r (corresponding to sample number n). The volume scattering intensity SV at each coordinate point is indicated by the color of the scale on the right. In the original scale, the lowest value (-70 dB) is black and the highest value (-30 dB) is red. The intermediate value on the scale is green. The scale goes from the lowest value black through blue, light blue, green, and yellow to the highest value red. For convenience, FIG. 9 shows a grayscale version of the original.

[0109] In Figure 9, the rectangular area surrounded by the two outer vertical lines V01, V02 and the two outer horizontal lines H01, H02 is the tracking area A0, and the rectangular area surrounded by the two inner vertical lines V11, V12 and the two inner horizontal lines H11, H12 is the fish school area A1. The fish school area A1 is included in the tracking area A0 and is smaller than the tracking area A0. The area of ​​the fish school with a high volume scattering strength SV is generally included in the fish school area A1.

[0110] 7, the control unit 11 calculates the fish quantity index based on the amplitude data included in the fish school area A1 (S104). The method of calculating the fish quantity index is as described above.

[0111] Next, the control unit 11 calculates an index value indicating how large the echo intensity of the entire tracking area is relative to the echo intensity around the tracking area (S105). Here, the reverberation contrast is calculated as this index value.

[0112] When the underwater detection device 10 detects a school of fish near the sea surface from a distance, the range detected is one where the tilt angle is around 0°. In this case, reverberation echoes such as waves reflected from the sea surface (sea surface reflection) may be distributed over a wide range including the range of echoes from the school of fish (fish school echoes).

[0113] The reverberation contrast is a parameter that indicates the degree to which reverberation echoes that are as strong as or stronger than the fish school echoes are distributed over a wide area including the tracking area A0. In other words, the reverberation contrast is a parameter that indicates how much the echo in the tracking area A0 is larger than the surrounding areas. Here, the reverberation contrast is calculated so that the reverberation contrast becomes smaller as the degree to which reverberation echoes that are as strong as or stronger than the fish school echoes are distributed over a wide area including the tracking area A0 increases.

[0114] FIG. 10 is a diagram showing a method for calculating the reverberation contrast.

[0115] Here, four reference regions R1 to R4 are defined that are in contact with the four sides of the tracking region A0. The control unit 11 calculates the average value SV a0 , and further, for each of the reference regions R1 to R4, the average value SV a1 ~SV a4 Then, the control unit 11 calculates the average value SV a1 ~SV a4 The maximum value (second average value) of the average value SV a0 The reverberation contrast is calculated by dividing the first average value by the second average value.

[0116] Fig. 11 is a diagram showing the distribution state of the volume scattering strength SV when the reverberation contrast is relatively large, and Fig. 12 is a diagram showing the distribution state of the volume scattering strength SV when the reverberation contrast is relatively small. In Fig. 11 and Fig. 12, the volume scattering strength SV is mapped in the same Cartesian coordinate system as Fig. 9 and at the same scale as Fig. 9. In Fig. 12, the fish school area A1 is approximately the same size as the tracking area A0.

[0117] As shown in Figure 11, when the reverberation contrast is relatively large, the extent to which reverberation echoes that are as strong as or stronger than the fish school echo are distributed over a wide area including the tracking area A0 is small. On the other hand, as shown in Figure 12, when the reverberation contrast is relatively small, strong volume scattering strength SV due to reverberation echoes such as sea surface reflections are widely distributed above, below, and to the right of the tracking area A0, and the extent to which reverberation echoes that are as strong as or stronger than the fish school echo are distributed over a wide area including the tracking area A0 is large. From these actual measurement results, it can be confirmed that the reverberation contrast calculated by the above method is a parameter that indicates the degree to which reverberation echoes that are as strong as or stronger than the fish school echo are distributed over a wide area including the tracking area A0.

[0118] The method of calculating the reverberation contrast is not limited to the method shown in FIG. a1 ~SV a4 The average value of SV a0Alternatively, the reference regions R1 to R4 may be set so that the sum of the areas of the reference regions R1 to R4 is equal to the area of ​​the tracking region A0, and the reverberation contrast may be calculated by dividing the sum of the volume scattering strengths SV of the tracking region A0 by the sum of the volume scattering strengths SV of the reference regions R1 to R4.

[0119] 7, the control unit 11 executes a reverberation contrast test (S106) using the reverberation contrast calculated in step S105. Specifically, the control unit 11 determines whether the reverberation contrast is equal to or greater than a predetermined reverberation threshold value.

[0120] If the reverberation contrast is equal to or greater than the reverberation threshold (S107: YES), the control unit 11 expands the fish school area A1 set in step S103 by a predetermined magnification factor greater than 1 to form a new tracking area A0 (S108). Specifically, the control unit 11 expands the widths W11 and W12 by the above magnification factor while maintaining the center point C11 in Fig. 8 to form a new tracking area A0. The center point of the new tracking area A0 is the same as the center point C11 of the fish school area A1.

[0121] On the other hand, if the reverberation contrast is less than the reverberation threshold (S107: NO), the control unit 11 skips step S108 and maintains the current tracking area A0 as the tracking area for the next ping.

[0122] In step S108, a new tracking area A0 is configured based on the fish school area A1, so that the new tracking area A0 can be positioned at a position shifted from the original tracking area A0 to a position corresponding to the school of fish. Since the new tracking area A0 is an area of ​​the fish school A1 enlarged by a predetermined magnification factor greater than 1, even if the shape of the school of fish itself changes or the school of fish is enlarged and deformed by merging with other small schools of fish, the amplitude data of the enlarged or deformed school of fish is likely to be included in the new tracking area A0. This allows the fish school echo to be tracked smoothly.

[0123] However, if the process of step S108 is repeated in a state where reverberation echoes as strong as or stronger than the fish school echoes are distributed over a wide area including the tracking area A0, the tracking area A0 may continue to expand with each ping due to the influence of surrounding reverberation echoes, and may become several times wider than the original range of the fish school echoes. When this happens, the fish school area A1 cannot be set properly.

[0124] 7, if the reverberation contrast is less than the reverberation threshold (S107: NO), step S108 is skipped and the tracking area using the current tracking area A0 is set as the area for setting the tracking area for the next ping. This prevents the tracking area A0 from being excessively expanded by the processing of step S108 in a state where reverberation echoes as strong as or stronger than the fish school echoes are distributed over a wide range including the tracking area A0.

[0125] From this viewpoint, the reverberation threshold is set under the condition that the fish school area A1 can be set appropriately based on the volume scattering strength SV in the tracking area A0, and a new tracking area A0 can be properly configured based on this fish school area A1. That is, the lower limit of the reverberation contrast that can satisfy this condition is set as the reverberation threshold. In other words, the reverberation contrast when the degree to which reverberation echoes that are as strong as or stronger than the fish school echoes are distributed over a wide range including the tracking area A0 is at the upper limit that can satisfy this condition is set as the reverberation threshold. The reverberation threshold may be set based on actual measurements.

[0126] After that, the control unit 11 judges whether or not a command to end the tracking of the school of fish has been input from the user (S109). If the command to end has been input (S109: YES), the control unit 11 ends the process of Fig. 7. If the command to end has not been input (S109: NO), the control unit 11 returns the process to step S101 and executes the process for the next ping.

[0127] In the next and subsequent pings, the determination in step S101 is NO, so step S110 is executed. In step S110, the position of the tracking area A0 configured for the current ping in the previous ping is corrected based on the navigation data. That is, due to the progress of the ship S1 between the next ping and the current ping, the position of the ship S1 is displaced and the direction (azimuth) of the ship S1 rotates. As a result, the origin of the scanning plane SP1 shifts, and the scanning plane SP1 rotates about the central axis of the transducer 13.

[0128] In step S110, a process is performed to correct (project) the position on the earth of the tracking area A0 configured for the current ping in the previous ping to a position on the scanning plane SP1 in the current ping. Specifically, the control unit 11 projects the center point C01 of the tracking area A0 configured for the current ping in the previous ping to the closest position (coordinate position defined by the sample number and beam number) on the scanning plane SP1 in the current ping. Then, the control unit 11 applies the widths W01 and W02 of the tracking area A0 configured for the current ping to the center point C01 after projection, and sets the corrected tracking area A0 for the current ping.

[0129] The tracking area A0 corrected in step S110 is the tracking area A0 configured in step S108 if the determination in step S107 for the previous ping is YES, and is the tracking area A0 used in the previous ping if the determination in step S107 for the previous ping is NO.

[0130] After correcting the tracking area A0 in this way, the control unit 11 executes the processes in and after step S103. The control unit 11 repeatedly executes the processes in steps S110 and S103 to S108 until an instruction to end the tracking of the school of fish is input from the user (S109: NO). This updates the school of fish area A1 and the fish quantity index, and updates the tracking area A0 for each ping. Thereafter, when an instruction to end the tracking of the school of fish is input from the user (S109: YES), the control unit 11 ends the process according to the flowchart in FIG. 7.

[0131] 7, the control unit 11 executes a process for displaying information related to the fish quantity index calculated in step S104. Every time the control unit 11 calculates the fish quantity index in step S104, it updates the fish quantity index to be displayed in area A12 of FIG.

[0132] The control unit 11 may cause the display unit 17 to display a display image 110 shown in FIG. 13 as a screen for displaying information related to the fish quantity index.

[0133] Display image 110 includes current fish quantity index value 111 calculated by the function of fish quantity index calculation unit 11c in step S104 of Fig. 7, and a time series graph 112 of fish quantity indexes calculated so far. Current fish quantity index value 111 may be the current fish quantity index value itself, or may be the average value of fish quantity index values ​​calculated over a fixed period of time from the present. The fish quantity index value at each time in graph 112 is similar to this.

[0134] The horizontal and vertical axes of graph 112 are time (units: minutes) and fish quantity index (units: tons), respectively. The current time is set at the right end of the horizontal axis, and the further to the left the time goes back in time. Here, graph 112 shows the transition of the value of the fish quantity index from the present up to 20 minutes ago.

[0135] The user can grasp the fish quantity at the current position from the fish quantity index value 111 included in the display image 110, and can further grasp the transition of the fish quantity on the ship's route so far from the graph 112. Thus, the user can smoothly grasp the state of the school of fish and the position where the fish should be caught.

[0136] The display image 110 of Fig. 13 may be arranged in any of the divided areas of the area A12 on the screen of Fig. 5. Alternatively, the display image 110 of Fig. 13 may be displayed overlapping the echo image P10 on the screen of Fig. 5 so as not to overlap the echo image P10 as much as possible. In this case, the display image 110 may be switched between display and erasure in response to an operation from the user.

[0137] Furthermore, the magnification applied in step S108 does not have to be a fixed value, and may be set, for example, so that the magnification increases with an increase in reverberation contrast.

[0138] FIG. 14 is a graph showing an example of a method for setting an enlargement magnification when the fish school area A1 is enlarged to form a new tracking area A0 in step S108 of FIG.

[0139] In this setting method, a constant magnification is set when the reverberation contrast is in the range from the reverberation threshold to a value C1, and when the reverberation contrast is in the range of a value C2 or more that is larger than the value C1, a constant magnification is set that is larger than the magnification in the range up to the value C1. In addition, for the range between the values ​​C1 and C2, the magnification is set to increase linearly as the reverberation contrast increases.

[0140] By setting the magnification in this way, in a situation where the reverberation echoes as strong as or stronger than the fish school echoes are distributed over a wide area including the tracking area A0 to a comparatively high extent, the new tracking area A0 is prevented from expanding excessively with respect to the fish school area A1, and in a situation where the reverberation echoes as strong as or stronger than the fish school echoes are distributed over a wide area including the tracking area A0 to a comparatively low extent, the expansion of the new tracking area A0 with respect to the fish school area A1 is promoted. Therefore, the size of the new tracking area A0 can be appropriately adjusted according to the distribution of the reverberation echoes.

[0141] However, the method of setting the magnification is not limited to this. For example, in a range where the reverberation contrast is greater than the value C1, the magnification may be set so as to increase linearly as the reverberation contrast increases. Alternatively, the magnification may be set so as to increase linearly from the reverberation threshold as the reverberation contrast increases. Also, the magnification that increases as the reverberation contrast increases does not have to change linearly, and may, for example, increase gradually along a predetermined curve.

[0142] <Effects of the embodiment> According to the above embodiment, the following effects can be achieved.

[0143] As shown in Figures 7 and 10, the control unit 11 (fish school tracking unit 11b) decides whether or not to use data based on the school of fish echoes within the tracking area A0 to update the tracking area (S108) based on a judgment (S106, S107) of whether an index value (reverberation contrast) indicating how much greater the echo intensity (volume scattering intensity SV) of the entire tracking area A0 is compared to the echo intensity (volume scattering intensity SV) around the tracking area A0.

[0144] In a situation where the index value (reverberation contrast) is small and reverberation echoes as strong as or stronger than the fish school echoes are highly distributed over a wide area including the tracking area A0, the fish school echoes blend in with the reverberation echoes and are difficult to distinguish from the reverberation echoes. If the tracking area A0 is updated (S108, S110) using data based on the fish school echoes (volume scattering intensity SV) under such circumstances, the updated tracking area A0 will be significantly affected by the reverberation echoes, making it difficult to update the tracking area A0 properly. In contrast, the above configuration makes it possible to avoid using the fish school echo data (volume scattering intensity SV) to update the tracking area A0 under such circumstances. Therefore, the tracking area A0 can be updated properly.

[0145] As shown in Figure 7, if the index value (reverberation contrast) is greater than or equal to the threshold (reverberation threshold) (S107: YES), the control unit 11 (fish school tracking unit 11b) updates the tracking area based on the data based on the fish school echo (volume scattering intensity SV) and the navigation data (S108, S110), and if the index value (reverberation contrast) is less than the threshold (reverberation threshold), it updates the tracking area based on the navigation data without using the data based on the fish school echo (volume scattering intensity SV) (S110).

[0146] According to this configuration, when the index value (reverberation contrast) is equal to or greater than a predetermined threshold (reverberation threshold), i.e., when the effect of reverberation echo on the fish school echo in the tracking area A0 is small, the tracking area A0 is updated based on the data based on the fish school echo and the navigation data. Therefore, the tracking area A0 can be updated appropriately. On the other hand, when the index value (reverberation contrast) is less than the predetermined threshold (reverberation threshold), i.e., when the effect of reverberation echo on the fish school echo in the tracking area is large, the tracking area is updated based on the navigation data without using the data based on the fish school echo (volume scattering strength SV). Therefore, until the effect of reverberation echo decreases, the tracking area including the school of fish to be tracked can be smoothly set based on the navigation data.

[0147] As shown in Figures 7 and 10, the control unit 11 (fish school tracking unit 11b) calculates, as the index value, a reverberation contrast that indicates the degree to which reverberation echoes having an echo intensity that is equal to or stronger than the echo intensity within the tracking area A0 are distributed over a wide area including the tracking area A0 (S105), and performs a judgment by a reverberation contrast test based on the reverberation contrast (S106, S107).

[0148] According to this configuration, the influence of reverberation echoes on fish school echoes can be evaluated by the reverberation contrast, and based on this evaluation, it can be determined whether or not data based on the fish school echoes should be used to update the tracking area A0.

[0149] As shown in FIG. 10, the reverberation contrast is calculated from a first average value of data (volume scattering intensity SV) within the tracking region A0 and a second average value of data (volume scattering intensity SV) within reference regions R1 to R4 surrounding the tracking region A0.

[0150] This allows the echo intensity of the entire tracking area A0 to be obtained as a first average value, and the echo intensity around the tracking area A0 to be obtained as a second average value.

[0151] Here, the reverberation contrast is calculated by dividing the first average value by the second average value.

[0152] This makes it possible to appropriately evaluate, by using the reverberation contrast, whether reverberation echoes that are as strong as or stronger than the fish school echoes are distributed over a wide area including the tracking area.

[0153] As described above, the reverberation contrast is calculated so as to be smaller as the degree to which reverberation echoes that are as strong as or stronger than the fish school echoes are distributed over a wide range including the tracking area increases.

[0154] Then, the control unit 11 (fish school tracking unit 11b) sets a reverberation threshold to be compared with the reverberation contrast, and in the processing of Figure 7, if the reverberation contrast is equal to or greater than the reverberation threshold (S107: YES), it sets a tracking area to be applied at the next transmission timing (next ping) based on the data based on the fish school echo (volume scattering intensity SV) and the navigation data (S108, S110), and if the reverberation contrast is less than the reverberation threshold (S107: NO), it sets a tracking area A0 to be applied at the next transmission timing (next ping) based on the navigation data (S110) without using the fish school echo data.

[0155] According to this configuration, when the reverberation contrast is equal to or greater than the reverberation threshold, i.e., when the reverberation echoes that are as strong as or stronger than the fish school echoes are distributed over a wide area including the tracking area to a low extent, the tracking area to be applied to the next wave transmission timing is set based on the data based on the fish school echoes and the navigation data. Therefore, the tracking area to track the fish school echoes can be set appropriately based on the amplitude data. On the other hand, when the reverberation contrast is less than the reverberation threshold, i.e., when the reverberation echoes that are as strong as or stronger than the fish school echoes are distributed over a wide area including the tracking area to a high extent, the tracking area to be applied to the next wave transmission timing is set based on the navigation data without using the data based on the fish school echoes. Therefore, it is possible to prevent the updated tracking area from being significantly affected by the reverberation echoes, and it is possible to smoothly set the tracking area to track the fish school echoes based on the navigation data until the influence of the reverberation echoes decreases.

[0156] As shown in Figures 7 and 8, the control unit 11 (fish school tracking unit 11b) estimates the fish school area A1, which is the area of ​​the fish school echo, based on the data (volume scattering intensity SV) within the tracking area A0 (S103), and if the index value (reverberation contrast) is greater than or equal to the threshold (reverberation threshold) (S107: YES), it expands the fish school area A1 by a predetermined magnification to form a new tracking area (S108), and corrects the new tracking area to a position based on the origin at the next wave transmission timing (next ping) based on the navigation data (S110) and sets it as the tracking area A0 to be applied at the next wave transmission timing, and if the index value (reverberation contrast) is less than the threshold (reverberation threshold) (S107: NO), it corrects the current tracking area A0 to a position based on the origin at the next wave transmission timing based on the navigation data (S110), and sets it as the tracking area A0 to be applied at the next wave transmission timing.

[0157] According to this configuration, the tracking area A0 is corrected to a position based on the origin after the movement according to the movement of the ship S1. Therefore, the tracking area A0 can be appropriately applied at each wave transmission timing.

[0158] As shown in FIG. 14, the control unit 11 (fish school tracking unit 11b) changes the magnification used to enlarge the fish school area A1 so that the magnification increases as the index value (reverberation contrast) increases.

[0159] According to this configuration, the size of the new tracking area A0 can be appropriately adjusted according to the distribution state of the reverberation echo.

[0160] As shown in Figure 3, the underwater detection device 10 is equipped with a fish quantity index calculation unit 11c that calculates a fish quantity index based on data (amplitude data) within the fish school area A1, and an image generation unit 11d that generates a display image including information regarding the fish quantity index.

[0161] This allows the fish quantity index of the school of fish tracked by the school of fish tracking unit 11b to be updated and displayed as needed, allowing the user to smoothly grasp the fish quantity index of the school of fish being tracked.

[0162] <Change Example 1> FIG. 15 is a flowchart showing a fish school tracking process according to the first modified example.

[0163] In the flowchart of Figure 15, steps S111 to S113 are added compared to the flowchart of Figure 7. The processing in the other steps in Figure 15 is similar to the processing in the corresponding steps in Figure 7. The processing in steps S111 to S113 is performed by the control unit 11 using the function of the fish school tracking unit 11b.

[0164] In step S111, the control unit 11 calculates a fish school contrast indicating the likelihood (degree) that the tracking area A0 contains fish school echoes that can be distinguished from reverberation echoes, based on the amplitude data in the tracking area A0 and the amplitude data in the reference areas R1 to R4 in Fig. 10. More specifically, the control unit 11 calculates an average value SV a0_max , and further, for each of the reference regions R1 to R4, the median value SV c1 ~SV c4 Then, the control unit 11 calculates the median value SV c1 ~SV c4 The maximum value of the average value SV a0_max The value obtained by dividing the above is calculated as the fish school contrast.

[0165] Average value SV obtained from tracking area A0 a0_max corresponds to the echo intensity of the core of the fish school echo in the tracking area A0. The greater the echo intensity of this core is compared to the echo intensity of the surrounding reference areas R1 to R4, the clearer the fish school in the tracking area will be, and the higher the likelihood that the fish school echo is included in the tracking area A0. Therefore, by calculating the fish school contrast as described above, the greater the fish school contrast is, the higher the likelihood that the fish school echo is included in the tracking area A0.

[0166] In addition, the average value SV a0_maxBy using the average value of the volume scattering strength SV within a range of several percent (for example, 5%) from the largest value, the representative value of the fish school echo can be properly evaluated regardless of the width of the tracking area. If the average value SV a0_max If is the average value of all volume scattering strengths SV within the tracking area, then in a situation where weak reverberation echoes (sea surface clutter) are distributed throughout the wide tracking area A0 and strong fish school echoes exist in a small area within that area, the presence of fish school echoes is unlikely to be reflected in this average value. Note that the several percent here is not limited to 5%, and may be changed to another appropriate value as long as the above evaluation can be performed appropriately.

[0167] Furthermore, by using the median rather than the average value of the volume scattering intensity SV for the reference regions R1 to R4, the representative value of the reverberation echo (sea surface reflection) can be appropriately evaluated even if a relatively small fish school echo other than the tracking target is present within the reference regions R1 to R4.

[0168] The control unit 11 executes a fish school contrast test (S112) using the fish school contrast calculated in step S111. Specifically, the control unit 11 determines whether the fish school contrast is equal to or greater than a predetermined fish school threshold value.

[0169] If the fish school contrast is equal to or greater than the fish school threshold (S113: YES), the control unit 11 advances the process to step S105. On the other hand, if the fish school contrast is less than the fish school threshold (S113: NO), the control unit 11 skips steps S105 to S108 and advances the process to step S109.

[0170] Here, the fish school threshold is a threshold for determining whether or not to display the fish quantity index calculated from the amplitude data in the fish school area A1 in step S104. In other words, the fish school threshold defines the boundary for whether or not the fish quantity index has an accuracy suitable for display. The fish school threshold may be set based on actual measurements.

[0171] Here, the pass criterion for step S113 is lower than the pass criterion for step S107. That is, even if the judgment in step S107 is "Fail", the judgment in step S113 may be "Pass", but if the judgment in step S113 is "Fail", the judgment in step S107 will usually also be "Fail". Therefore, if the judgment in step S113 is "NO", the process proceeds to step S109 without performing the processes in steps S105 to S108.

[0172] FIG. 16 is a flowchart showing a display process for information related to fish quantity indexes according to the first modified example.

[0173] The flowchart of Fig. 16 is performed by the control unit 11 using the function of the image generating unit 11d. The control unit 11 executes the process of Fig. 16 for each ping.

[0174] The control unit 11 determines whether the fish school contrast test (steps S112 and S113 in FIG. 15) for the current ping is passed (S201). If the fish school contrast test is passed (S201: YES), the control unit 11 updates the information on the fish quantity index displayed on the display unit 17 based on the fish quantity index calculated for the current ping (step S104 in FIG. 15) (S202).

[0175] On the other hand, if the fish school contrast test is unsuccessful (S201: NO), the control unit 11 does not update the information on the fish quantity index in the current ping, and maintains the display of the information on the fish quantity index from the previous ping (S203).Then, the control unit 11 determines whether the fish school contrast test has been unsuccessful a predetermined number of times (for example, set in a range from several times to a dozen or so times), including the failure in the current ping (S204).

[0176] If the determination in step S204 is NO, the control unit 11 ends the processing for this ping. On the other hand, if the determination in step S204 is YES, the control unit 11 adds a predetermined warning display to the display of the information related to the fish quantity index (S205). For example, as this warning, the control unit 11 displays the information related to the fish quantity index in a color different from normal (for example, red). Alternatively, the control unit 11 may add a mark indicating a warning (for example, an exclamation mark) near the information related to the fish quantity index. This causes the control unit 11 to end the processing for the current ping.

[0177] <Effects of Change Example 1> As shown in Figure 15, the control unit 11 (fish school tracking unit 11b) calculates a fish school contrast indicating the likelihood that a fish school echo is contained within the tracking area A0 based on the data (volume scattering intensity SV) within the tracking area A0 and the data (volume scattering intensity SV) within reference areas R1 to R4 surrounding the tracking area A0 (S111), and if the fish school contrast is greater than or equal to a predetermined fish school threshold (S113: YES), it executes a tracking area update process (S105 to S108) based on the index value (reverberation contrast), and if the fish school contrast is less than the fish school threshold (S113: NO), it sets the tracking area A0 to be applied at the next transmission timing based on the navigation data (S110) without executing the tracking area update process (S105 to S108) based on the index value (reverberation contrast).

[0178] According to this configuration, when the fish school contrast is less than the fish school threshold, i.e., when the reverberation echoes that are as strong as or stronger than the fish school echoes are highly likely to be distributed over a wide area including the tracking area A0, the update process of the tracking area A0 based on the index value (reverberation contrast) is omitted, and the tracking area A0 to be applied to the next wave transmission timing is set from the navigation data. Therefore, the update of the tracking area A0 can be performed appropriately while simplifying the process.

[0179] As described above, the control unit 11 (fish school tracking unit 11b) can be configured to calculate the fish school contrast based on the maximum value of the data (volume scattering intensity SV) within the tracking area A0 and the median value of the data surrounding the tracking area.

[0180] With this configuration, it is possible to properly calculate the fish school contrast, which indicates the likelihood that the tracking area contains fish school echoes that can be distinguished from reverberation echoes.

[0181] As shown in Figure 16, when the fish school contrast is less than a predetermined fish school threshold (S201: NO), the control unit 11 (image generation unit 11d) does not update the information regarding the fish quantity index, and continues to display the information regarding the fish quantity index that was displayed at the previous transmission timing (S203).

[0182] This configuration makes it possible to prevent information about low-precision fish quantity indexes calculated in a state where reverberation echoes that are as strong as or stronger than the fish school echoes are distributed over a wide area including the tracking area from being displayed and presented to the user, thereby increasing the reliability of the information about fish quantity indexes for the user.

[0183] <Change Example 2> In the above embodiment, the fish quantity index is calculated and displayed in addition to the fish tracking process, but the invention can also be extracted from only the tracking process.

[0184] FIG. 17 is a flowchart showing a fish school tracking process according to the second modified example.

[0185] In the flowchart of Fig. 17, the process of step S104 is omitted from the flowchart of Fig. 7. The process of each step in the flowchart of Fig. 17 is the same as the process of the corresponding step in the flowchart of Fig. 7. This process also makes it possible to properly track the echoes of the school of fish, as in the process of Fig. 7.

[0186] FIG. 18 is a flowchart showing a tracking process for another school of fish according to the second modification.

[0187] In the flowchart of Fig. 18, the process of step S104 is omitted from the flowchart of Fig. 15. The process of each step in the flowchart of Fig. 18 is the same as the process of the corresponding step in the flowchart of Fig. 15. This process also makes it possible to properly track the echoes of the school of fish, as in the process of Fig. 15.

[0188] <Other changes> In the above embodiment, the volume scattering strength SV obtained from the amplitude data was used in the processing of Fig. 7 or Fig. 15, but other data derived from the amplitude data may be used in the processing of tracking the school of fish. For example, when the width of the tracking area A0 in the distance direction is smaller than the distance from the transducer 13 to the tracking area A0, the attenuation of the sound wave due to spherical divergence and absorption is almost constant within the tracking area A0, so the amplitude data itself may be used in the processing of Fig. 7 or Fig. 15.

[0189] In the above embodiment, the reverberation contrast is calculated by dividing the average value (first average value) of the data (volume scattering intensity SV) included in the tracking region A0 by the average value (second average value) obtained from the data (volume scattering intensity SV) of the reference regions R1 to R4, but the reverberation contrast may be calculated by dividing the second average value by the first average value. In this case, the determination in step S107 in Fig. 7 is YES when the reverberation contrast is equal to or less than the reverberation threshold value, and NO when the reverberation contrast is greater than the reverberation.

[0190] Furthermore, in the above embodiment, the data generating unit 11a generates the amplitude data, but the data generating unit 11a may further generate the volume scattering intensity SV based on the amplitude data.

[0191] Furthermore, in the above embodiment, the display image 110 in FIG. 13 is shown as an example of a display image including information related to the fish quantity index, but the display image is not limited to this.

[0192] For example, as shown in Fig. 19, plots P18 may be added at regular intervals on the ship's wake P12 in an echo image P10, and the value of the fish quantity index (unit: tons) at the position (time) of each plot P18 may be added to the right of the plot P18. Alternatively, as shown in Fig. 20, circular marks P19 with a diameter according to the value of the fish quantity index at each position may be superimposed and displayed at regular intervals on the ship's wake P12. In this case, the value of the fish quantity index Q at each point may also be added near each circle.

[0193] These displayed images also allow the user to understand the changes in the amount of fish on the route the ship has taken so far, and therefore the user can smoothly understand the locations where fish should be caught.

[0194] Alternatively, a time series graph may be displayed in which the horizontal axis of FIG. 13 is corrected to the distance traveled (accumulated distance traveled). The speed of a boat during fish search is not necessarily constant. In contrast, if the horizontal axis of the time series graph is the distance traveled (accumulated distance traveled), when a user refers to this graph and wants to return to a location where a promising fish quantity index value was generated, the user can easily estimate that location based on the distance traveled (accumulated distance traveled) on the horizontal axis of the graph.

[0195] Alternatively, as information relating to the fish quantity index, only the fish quantity index itself may be displayed.

[0196] Moreover, the magnifications shown on the vertical axis in FIG. 14 are also just an example, and other magnifications may be assigned.

[0197] In addition, in the above embodiment, the fish quantity index calculation unit 11c and the like are realized as functions of the control unit 11 provided by the program stored in the storage unit 12, but these do not necessarily have to be realized as functions provided by the program stored in the storage unit 12. For example, one or more of these functions may be configured by hardware such as an FPGA (field-programmable gate array) or an integrated logic circuit.

[0198] In addition, the embodiments of the present invention can be modified in various ways as appropriate within the scope of the claims. [Explanation of symbols]

[0199] 10 Underwater detection equipment 11 Control section 11a Data Generation Section 11b Fish tracking section 11c Fish quantity index calculation part 11d Image Generation Unit 12 Storage section 13 Transmitter / Receiver 13a Ultrasonic transducer 14 Transmission processing unit 110 Display images 111 Fish abundance index value

Claims

1. a transmission processing unit that transmits ultrasonic waves at a predetermined interval to a plurality of ultrasonic transducers included in a transducer installed on the bottom of the ship; a data generating unit that forms a plurality of receiving beams in a scanning range based on electrical signals output from the plurality of ultrasonic transducers during a wave receiving period after the wave transmission timing, and generates data regarding echo intensity at each position in the scanning range; a fish school tracking unit that updates a tracking area of ​​a school of fish based on the data and navigation data related to the movement of a ship on which the transducer is installed, The fish school tracking unit includes: determining whether or not to use the data based on the fish school echoes within the tracking area for updating the tracking area based on a judgment of whether or not an index value indicating how large the echo intensity of the entire tracking area is relative to the echo intensity around the tracking area is equal to or larger than a predetermined threshold value; An underwater detection device characterized by:

2. 2. The underwater detection device according to claim 1, The fish school tracking unit includes: If the index value is equal to or greater than the threshold value, the tracking area is updated based on the data based on the fish school echoes and the navigation data; If the index value is less than the threshold value, updating the tracking area based on the navigation data without using the data based on the fish school echoes. An underwater detection device characterized by:

3. 2. The underwater detection device according to claim 1, the fish school tracking unit calculates, as the index value, a reverberation contrast indicating a degree to which reverberation echoes having an echo intensity equal to or greater than an echo intensity within the tracking area are distributed over a wide area including the tracking area, and makes the judgment based on the reverberation contrast; An underwater detection device characterized by:

4. 4. The underwater detection device according to claim 3, The reverberation contrast is calculated by a first average value of the data within the tracking region and a second average value of the data around the tracking region. An underwater detection device characterized by:

5. 5. The underwater detection device according to claim 4, The reverberation contrast is calculated by dividing the first average value by the second average value. An underwater detection device characterized by:

6. 4. The underwater detection device according to claim 3, The reverberation contrast is calculated so as to be smaller as the degree of the distribution is higher. An underwater detection device characterized by:

7. 7. The underwater detection device according to claim 6, The fish school tracking unit includes: setting a reverberation threshold to which the reverberation contrast is compared as the threshold; If the reverberation contrast is equal to or greater than the reverberation threshold, the tracking area to be applied at the next transmission timing is set based on the data based on the fish school echo and the navigation data; If the reverberation contrast is less than the reverberation threshold, the tracking area to be applied at the next transmission timing is set based on the navigation data without using the data based on the fish school echo. An underwater detection device characterized by:

8. 2. The underwater detection device according to claim 1, The fish school tracking unit includes: A fish school area, which is an area of ​​the fish school echo, is estimated based on the data within the tracking area; If the index value is equal to or greater than the threshold value, the fish school area is expanded by a predetermined factor to form a new tracking area, and the new tracking area is corrected to a position based on the position of the transducer at the next wave transmission timing based on the navigation data, and set as the tracking area to be applied at the next wave transmission timing. If the index value is less than the threshold value, the current tracking area is corrected based on the navigation data to a position based on the position of the transducer at the next wave transmission timing, and set as the tracking area to be applied at the next wave transmission timing. An underwater detection device characterized by:

9. 9. The underwater detection device according to claim 8, The fish school tracking unit changes the magnification used to enlarge the fish school area so that the magnification becomes larger as the index value becomes larger. An underwater detection device characterized by:

10. 9. The underwater detection device according to claim 8, A fish quantity index calculation unit that calculates a fish quantity index based on the data within the fish school area; an image generating unit that generates a display image including information about the fish quantity index; Equipped with An underwater detection device characterized by:

11. 2. The underwater detection device according to claim 1, The fish school tracking unit includes: Calculating a fish school contrast indicating a likelihood that a fish school echo is included in the tracking area based on the data within the tracking area and the data around the tracking area; When the fish school contrast is equal to or greater than a predetermined fish school threshold, an update process of the tracking area is performed based on the index value; If the fish school contrast is less than the fish school threshold, the tracking area to be applied at the next wave transmission timing is set based on the navigation data without updating the tracking area based on the index value. An underwater detection device characterized by:

12. 12. The underwater detection device according to claim 11, the fish school tracking unit calculates the fish school contrast based on a maximum value of the data within the tracking area and a median value of the data around the tracking area; An underwater detection device characterized by:

13. 12. The underwater detection device according to claim 11, When the fish school contrast is less than a predetermined fish school threshold, the image generating unit does not update the information on the fish quantity index, and continues to display the information on the fish quantity index displayed at the previous transmission timing. An underwater detection device characterized by:

14. A method for tracking a school of fish in an underwater detection device, comprising: A step of transmitting ultrasonic waves at a predetermined interval from a plurality of ultrasonic transducers included in a transducer installed on the bottom of a ship; forming a plurality of receiving beams in a scanning range based on electrical signals output from the plurality of ultrasonic transducers during a wave receiving period after the wave transmission timing, and generating data regarding echo intensity at each position in the scanning range; and updating a tracking area of ​​the fish school based on the data and on navigation data relating to the movement of the ship on which the transducer is installed; The step of updating the tracking area includes: and determining whether or not to use the data based on the fish school echoes in the tracking area for updating the tracking area based on a judgment of whether or not an index value indicating how large the echo intensity of the entire tracking area is relative to the echo intensity around the tracking area is equal to or larger than a predetermined threshold value. A fish school tracking method comprising:

15. The underwater detection device's computer A function of transmitting ultrasonic waves at a predetermined interval to a plurality of ultrasonic transducers included in a transducer installed on the bottom of the ship; a function of forming a plurality of receiving beams in a scanning range based on electrical signals output from the plurality of ultrasonic transducers during a wave receiving period after the wave transmission timing, and generating data regarding echo intensity at each position in the scanning range; and updating a tracking area of ​​the fish school based on the data and navigation data relating to the movement of the ship on which the transducer is installed. The function of updating the tracking area is A program including a function for determining whether or not to use the data based on the fish school echoes within the tracking area to update the tracking area based on a determination of whether an index value indicating how large the echo intensity of the entire tracking area is relative to the echo intensity around the tracking area is equal to or greater than a predetermined threshold value.

Images