Fish quantity information display device and fish quantity information display method

Abstract

A fish quantity information display device 1 comprises a transmission processing module 14 which causes a plurality of ultrasonic oscillators 13a in a transducer 13 installed on a ship bottom (S1, fig

Description

Technical Field

[0001] The present invention relates to a fish quantity information display device and fish quantity information display method for displaying information about fish quantity in fish school. Background

[0002] Conventionally, an underwater detection device for detecting a target in underwater is known. The underwater detection device transmits ultrasonic waves to underwater, receives the reflected wave, calculates an echo intensity from each position of underwater, and displays three-dimensional distribution (i.e., echo image) of the echo intensity.

[0003] For example, the underwater detection device transmits a transmission wave from a transducer having a plurality of ultrasonic oscillators, and receives the reflected wave at the transducer. Based on an electric signal output from each ultrasonic oscillator of the transducer by reception of the reflected wave, a plurality of reception beams are formed in the circumferential direction on a conical plane having the transducer as an apex by beam forming. From reception signal generated for each reception beam, an echo image corresponding to a scanning range of the reception beam is generated and displayed. Such underwater detection device is described, for example, in the following Patent Document 1.

[0004] Patent Document 1-Japanese Patent Laid-Open Publication No. 2009-300220 Summary Technical Problem

[0005] In the underwater detection device as described above, a fish quantity index of fish school calculated in the past is displayed on a cruising path of own ship, and a user may grasp the position where fish quantity index was large in the past on the cruising path of own ship.

[0006] However, the fish school is often located far from own ship and moves according to the swimming of the fish constituting fish school. Therefore, the present position of the fish school and fish quantity may not be accurately grasped simply by displaying the past fish quantity index of the fish school on the cruising path of own ship.

[0007] In view of such problems, it is an object of the present invention to provide a fish quantity information display device and a fish quantity information display method capable of more accurately providing the position and fish quantity of the fish school to the user. Solution to Problem

[0008] A first aspect of the present invention relates to a fish quantity information display device. The fish quantity information display device for this aspect is provided with: a transmission processing module which causes the plurality of ultrasonic oscillator included in the transducer installed on a bottom of a ship to transmit ultrasonic waves at transmission timing at predetermined intervals; a data generation module which forms the plurality of reception beam in a scanning range based on electric signal output from the plurality of ultrasonic oscillator during a reception period after transmission timing and generates data related to the echo intensity at each position of the scanning range; a fish school tracking module which tracks the fish school based on the data; a fish quantity index calculation module which calculates the fish quantity index of the fish school based on the data; and an image generation module which generates a display image in which fish quantity information based on the fish quantity index is related to a swimming path of fish school based on the tracking of the fish school and the fish quantity index.

[0009] In the fish quantity information display device, the fish school information is displayed in association with the swimming path of the fish school. Therefore, the user may grasp the present position of the fish school and the future movement of the fish school from the displayed swimming path, and may grasp the size of fish school and the change of fish quantity from fish quantity information associated with the swimming path. Therefore, the user may more accurately grasp the position of the fish school and the fish quantity from the display image.

[0010] In the fish quantity information display device, the fish school tracking module may calculate the movement situation of the fish school based on the tracking result of the fish school, and the image generation module may further relate the movement situation of fish school to the swimming path.

[0011] With this configuration, the user may more smoothly grasp to which position fish school will move from the display of the movement situation of the fish school associated with the swimming path in the display image. Thus, the user may advance own ship to the position and smoothly advance the capture of the fish school.

[0012] In the fish quantity information display device, according to this aspect, the fish quantity information includes a fish quantity image corresponding to the value of fish quantity index, and the image generation module may be configured to associate the fish quantity image with a predetermined position on the swimming path.

[0013] According to this configuration, the user may smoothly grasp fish quantity at each position on the swimming path.

[0014] In this configuration, the fish quantity image may be a circle composed of at least one of a diameter and a color corresponding to the value of fish quantity index.

[0015] According to this configuration, the user may intuitively grasp fish quantity at each position on the swimming path.

[0016] Alternatively, the fish quantity image may be a band composed of at least one of a width and a color corresponding to the value of fish quantity index.

[0017] According to this configuration, the user may intuitively grasp fish quantity at each position on the swimming path.

[0018] In the configuration, the transparency of fish quantity image may be adjusted so as to increase with the passage of time.

[0019] According to this configuration, the faster fish school moves, the longer fish quantity image is displayed. Thus, the user may intuitively grasp the speed of fish school movement from the length of the tail of the fish quantity image. In addition, the fish quantity image is displayed so as to become darker closer to the present position of the fish school. Thus, the user may intuitively grasp the “direction” of movement of fish school from the “direction in which the shading changes”.

[0020] In the fish quantity information display device, according to this aspect, the fish quantity information includes the value of fish quantity index, and the image generation module may be configured to display the value of fish quantity index at the predetermined position on the swimming path.

[0021] According to this configuration, the user may accurately grasp fish quantity at a position on the swimming path as a numerical value.

[0022] In the fish quantity information display device, according to this aspect, the image generation module may be configured to display the fish quantity information when the value of fish quantity index is equal to or greater than a predetermined threshold value.

[0023] According to this configuration, since the display of fish quantity information whose fish quantity index is less than the threshold value is omitted, the user may smoothly grasp the position on the swimming path where a large fish quantity larger than the threshold value has occurred.

[0024] In the fish quantity information display device, according to this aspect, the fish school tracking module may be configured to update the tracking area for tracking fish school based on the data and navigation data related to the movement of ship where the transducer is installed, and to determine whether or not to use the data based on fish school echo in the tracking area for updating the tracking area based on the determination of whether or not an index value indicating how large the echo intensity of the whole tracking area is relative to the echo intensity around the tracking area is equal to or greater than the predetermined threshold value.

[0025] When the index value is small, then the degree to which reverberation echo, which is stronger than or equal to fish school echo, is distributed over a wide range including the tracking area is high. Under such circumstances, the fish school echo is confused with reverberation echo and fish school echo is difficult to be distinguished from the reverberation echo. Therefore, if the data based on the fish school echo is used for updating the tracking area in this state, then the tracking area after the update is greatly influenced by the reverberation echo, and the tracking area may not be properly updated. On the other hand, according to the underwater detection device, according to this aspect, it is avoided that data based on fish school echo is used for updating the tracking area under such a situation. Therefore, the tracking area may be properly updated.

[0026] In this configuration, the fish school tracking module may be configured to update the tracking area based on the data based on the fish school echo and the navigation data when the index value is equal to or greater than threshold value, and to update the tracking area based on the navigation data without using the data based on fish school echo when the index value is less than threshold value.

[0027] In this configuration, when the index value is equal to or greater than the predetermined threshold value, that is, when the influence of reverberation echo on fish school echo in the tracking area is small, then the tracking area is updated based on the data based on fish school echo and the navigation data. Therefore, the tracking area may be properly updated. On the other hand, when the index value is less than the predetermined threshold value, that is, when the influence of reverberation echo on fish school echo in the tracking area is large, then the tracking area is updated based on the navigation data without using the data based on fish school echo. Therefore, until the influence of reverberation echo decreases, the tracking area including fish school to be tracked may be smoothly set based on the navigation data.

[0028] In this configuration, the fish school tracking module may be configured to calculate, as the index value, a reverberation contrast indicating the degree to which reverberation echo having the echo intensity equal to or greater than the echo intensity in the tracking area is distributed over a wide range including the tracking area, and to make the determination based on the reverberation contrast.

[0029] According to this configuration, the influence of reverberation echo on fish school echo may be evaluated by reverberation contrast, and based on this evaluation, whether or not the data based on fish school echo should be used for updating the tracking area may be determined.

[0030] In this configuration, the reverberation contrast may be calculated by the first average value of the data in the tracking area and the second average value of the data around the tracking area.

[0031] Thus, the echo intensity of the entire tracking area may be acquired by the first average value, and the echo intensity around the tracking area may be acquired by the second average value.

[0032] In this case, the reverberation contrast may be calculated by dividing the first average value by the second average value.

[0033] Thus, whether or not reverberation echo which is stronger than or equal to the fish school echo is distributed over a wide range including the tracking area may be appropriately evaluated by the reverberation contrast.

[0034] In the above configuration, the reverberation contrast may be calculated so as to become smaller as the degree of the distribution is higher.

[0035] In this case, the fish school tracking module may set reverberation threshold compared with reverberation contrast as a threshold value, and when reverberation contrast is greater than or equal to reverberation threshold, then the tracking area to be applied at the next transmission timing is set based on the data based on fish school echo and the navigation data, and when the reverberation contrast is less than reverberation threshold, then the tracking area to be applied at the next transmission timing is set based on the navigation data without using the data based on fish school echo.

[0036] According to this configuration, when the reverberation contrast is greater than or equal to reverberation threshold, that is, when the degree to which reverberation echo, which is stronger than or equal to fish school echo, is distributed over a wide range including the tracking area is low, then the tracking area to be applied at the next transmission timing is set based on the data based on fish school echo and the navigation data. Therefore, the tracking area to properly track fish school echo may be set based on the amplitude data. On the other hand, when reverberation contrast is less than reverberation threshold, that is, when the degree to which reverberation echo, which is stronger than or equal to the fish school echo, is distributed over a wide range including the tracking area is high, then the tracking area to be applied at the next transmission timing is set based on the navigation data without using the data based on fish school echo. Therefore, the tracking area after update may be avoided from being greatly affected by reverberation echo, and the tracking area to the track fish school echo may be smoothly set based on the navigation data until the influence of reverberation echo is reduced.

[0037] In the underwater detection device, according to this aspect, the fish school tracking module may be configured such that fish school area, which is the area of fish school echo, is estimated based on the data in the tracking area, and when the index value is equal to or greater than the threshold value, the fish school area is enlarged by a predetermined magnification to constitute a new tracking area, the new tracking area is set to the tracking area to be applied at the next transmission timing by correcting the position with reference to the position of the transducer at the next transmission timing based on the navigation data, and when the index value is less than the threshold value, the current tracking area is set to the tracking area to be applied at the next transmission timing by correcting the position with reference to the position of the transducer at the next transmission timing based on the navigation data.

[0038] According to this configuration, according to the movement of the ship, the tracking area is corrected to a position based on the position of the transducer after the movement. Therefore, the tracking area may be properly applied at each transmission timing.

[0039] In this configuration, the fish school tracking module may be configured to change the magnification used to enlarge the fish school area so that the magnification increases as the index value increases.

[0040] According to this configuration, the width of the new tracking area may be properly adjusted according to the distribution state of reverberation echo.

[0041] In this configuration, the fish school tracking module calculates a fish school contrast indicating certainty including fish school echo in the tracking area based on the data in the tracking area and the data around the tracking area, and the image generation module associates fish quantity information based on the fish quantity index acquired this time with the swimming path of fish school when fish school contrast is equal to or greater than a predetermined fish school threshold, and associates fish quantity information based on the previous fish quantity index with the swimming path of fish school instead of fish quantity index acquired this time when fish school contrast is less than fish school threshold.

[0042] According to this configuration, the display of fish quantity information based on the fish quantity index with low accuracy may be suppressed.

[0043] In this configuration, the fish school tracking module may be configured to calculate fish school contrast based on the maximum value of the data in the tracking area and the median value of the data around the tracking area.

[0044] According to this configuration, the fish school contrast indicating certainty including fish school echo distinguishable from reverberation echo in the tracking area may be properly calculated.

[0045] The fish quantity information display device according to this aspect further includes a radar device for detecting the surrounding target by receiving the reflected wave of the transmission wave transmitted in the air, and the image generation module may be configured to include target existing near the swimming path in the display image based on the detection result of the radar device.

[0046] According to this configuration, other ship, flocks of birds and the like existing near own ship may be further displayed. Thus, the user may judge whether or not it is possible to advance to the moving position of fish school without interference with other ship, and may smoothly advance the capture of fish school.

[0047] A second aspect of the present invention relates to a fish quantity information display method. The fish quantity information display method, according to the second aspect, causes transmitting, by the transmission processing module, ultrasonic waves to the plurality of ultrasonic oscillator included in the transducer installed at the bottom of the ship to transmit ultrasonic waves at transmission timing at predetermined intervals, forming, by the data generation module, the plurality of reception beam in the scanning range based on electric signal output from the plurality of ultrasonic oscillator in reception period after transmission timing, and generating data related to echo intensity at each position of the scanning range, tracking, by the fish school tracking module, fish school based on the data, calculating, by the fish quantity index calculation module, the fish quantity index of fish school based on the data, and generating, by the image generation module, the display image in which fish quantity information based on the fish quantity index is related to the swimming path of fish school based on the tracking of fish school and the fish quantity index.

[0048] According to a fish school tracking method, according to this aspect, the same effect as the first aspect may be achieved. Advantageous Effects of Invention

[0049] As described above, according to the present invention, it is possible to provide the fish quantity information display device and the fish quantity information display method capable of providing the image capable of more accurately estimating the position of fish school with a large fish quantity to the user.

[0050] The effect or significance of the present invention will be further clarified by the description of the following embodiments. However, the following embodiments are merely examples of the present invention, and the present invention is not limited in any way to those described in the following embodiments. Brief Description of Drawings

[0051] FIG. 1 is a diagram schematically showing how underwater is searched by an underwater detection device according to an embodiment 1 of the present invention. FIG. 2 is a diagram schematically showing how underwater is searched by the underwater detection device according to the embodiment 1 of the present invention. FIG. 3 is a block diagram showing the configuration of the underwater detection device according to the embodiment 1 of the present invention. FIG. 4 is a diagram for explaining a method of calculating fish quantity index according to the embodiment 1 of the present invention. FIG. 5 is a diagram schematically showing an example of an echo image displayed on a display unit according to the embodiment 1 of the present invention. FIG. 6 is a flowchart showing the processing of generating data related to echo intensity according to the embodiment 1 of the present invention. FIG. 7 is a flowchart showing fish school tracking processing according to the embodiment 1 of the present invention. FIG. 8 is a diagram showing a setting method of fish school area according to the embodiment 1 of the present invention. FIG. 9 is a diagram showing the setting example (actual measurement) of fish school area for the tracking area according to the embodiment 1 of the present invention. FIG. 10 is a diagram showing the calculation method of reverberation contrast according to the embodiment 1 of the present invention. FIG. 11 is a diagram showing the distribution state of the volume scattering intensity when reverberation contrast is relatively large according to the embodiment 1 of the present invention. FIG. 12 is a diagram showing the distribution state of the volume scattering intensity when reverberation contrast is relatively small according to the embodiment 1 of the present invention. FIG. 13 is a flowchart showing a process for generating the display image including fish quantity information according to the embodiment 1 of the present invention. FIG. 14 is a diagram showing a method for calculating the movement status of fish school according to the embodiment 1 of the present invention. FIG. 15 is a diagram schematically showing an example of the display image including fish quantity information based on fish quantity index according to the embodiment 1 of the present invention. FIG. 16 is a diagram schematically showing an example of the display image according to another display method 1 and according to the embodiment 1 of the present invention. FIG. 17 is a diagram schematically showing an example of the display image according to another display method 2 and according to the embodiment 1 of the present invention. FIG. 18 is a diagram schematically showing an example of the display image according to another display method 3 and according to the embodiment 1 of the present invention. FIG. 19 is a diagram schematically showing an example of the display image according to another display method 4 and according to the embodiment 1 of the present invention. FIG. 20 is a diagram schematically showing an example of the display image according to another display method 5 and according to the embodiment 1 of the present invention. FIG. 21 is a graph showing an example of a method for setting the magnification when fish school area is enlarged to constitute a new tracking area according to Modification Example 1 and according to the embodiment 1 of the present invention. FIG. 22 is a flowchart showing fish school tracking processing according to Modification Example 2 and according to the embodiment 1 of the present invention. FIG. 23 is a diagram showing the configuration of a fish quantity information display device according to the embodiment 2 of the present invention. FIG. 24 is a diagram showing the configuration of the display image displayed on a plotter device according to the embodiment 2 of the present invention. FIG. 25 is a diagram showing the configuration of the fish quantity information display device according to the embodiment 3 of the present invention. FIG. 26 is a diagram showing the configuration of the display image displayed on the plotter device according to the embodiment 3 of the present invention. Description of Embodiments

[0052] Embodiments of the present invention will be described below with reference to the drawings. For convenience, XYZ axes orthogonal to each other are appropriately added to the drawings. 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 ship travels. Embodiment 1

[0053] In the embodiment 1, an underwater detection device 10 corresponds to a fish quantity image display device described in the claims. However, this correspondence does not specifically limit the invention described in the claims.

[0054] FIGS. 1 and 2 are diagrams schematically showing how underwater is searched by the underwater detection device 10, according to an embodiment 1 of the present invention.

[0055] In FIGS. 1 and 2, 9 is an azimuth angle about a transducer 13 installed on a bottom of ship SI, and (p is atilt angle of a scanning plane SP1 to be described later with respect to a horizontal plane (X-Y plane).

[0056] The underwater detection device 10 includes the transducer 13 installed on the bottom of the ship SI such as a fishing boat. The underwater detection device 10 transmits a pulse (i.e., transmission pulse) of sound waves from the transducer 13, and receives a sound wave (i.e., echo) reflected (backscattered) by an object such as a fish present in underwater by the same transducer 13. The underwater detection device 10 detects the object present in underwater based on the echo received by the transducer 13.

[0057] The transducer 13 includes a plurality of ultrasonic oscillators (i.e., a number of ultrasonic oscillators). Each ultrasonic oscillator converts an input electric signal into the sound wave and radiates it during transmission, and converts an incident sound wave into an electric signal and outputs it during reception. Typically, the transducer 13 has a cylindrical shape, and hundreds of ultrasonic oscillators are regularly arranged on its side.

[0058] Here, 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. The conical surface is referred to as the scanning plane SP1, and the apex and axis of this scanning plane SP1 are referred to as the origin and the scanning axis, respectively. The origin coincides with the position of the transducer 13, and the scanning axis extends from this origin to direction just below. Here, the scanning axis coincides with the Z-axis. The angle formed by the scanning plane SP1 with the horizontal plane (X-Y plane) is the tilt angle (p described above.

[0059] As shown in FIG. 1, the underwater detection device 10 transmits a transmission beam TB1 having the maximum intensity on the scanning plane SP1 over its entire circumference during transmission. This transmission beam TB1 has an axial intensity distribution with respect to scanning axis (Z-axis in FIG. 1), and its width in the vertical direction is relatively narrow.

[0060] As shown in FIG. 2, the underwater detection device 10 forms a large number of reception beams RBI having the maximum sensitivity on the scanning plane SP1 during reception. The reception beams RB1 are formed by applying beam forming to electric signal output from the plurality of ultrasonic oscillators disposed in the transducer 13. [0061 ] Each reception beam RB lisa pencil beam with narrow width in both vertical and horizontal directions, and has the same directivity. A straight line passing through the origin and facing the direction in which the sensitivity of the reception beam RBI is maximized is the beam axis of each reception beam RB 1. A plurality of reception beams RB 1 are formed side by side in the direction of azimuth angle 0 over the entire circumference of the scanning plane SP1 at a fixed angular interval (azimuth resolution). The underwater detection device 10 converts the intensity of sound waves received in each reception beam RBI into a color and displays it as an image (i.e., echo image).

[0062] FIG. 3 is a block diagram showing the configuration of the underwater detection device 10, according to the embodiment 1 of the present invention.

[0063] The underwater detection device 10 includes a control unit 11, storage unit 12, the transducer 13, transmission processing module 14, reception processing module 15, transmission / reception switching unit 16, display unit 17, display processing module 18, input unit 19, and input processing module 20. The transducer 13 is installed in the bottom of ship SI as described above, and other components such as the control unit 11 are installed in a wheelhouse or the like of ship S1.

[0064] The control unit 11 includes an arithmetic processing circuit (i.e., computer) such as a central processing unit (CPU), and executes control processing described later by a program stored in the storage unit 12. The storage unit 12 includes a storage medium such as Read Only Memory (ROM), Random Access Memory (RAM), and hard disk. The storage unit 12 stores a program for the control unit 11 to execute control processing.

[0065] The transducer 13 includes a plurality of ultrasonic oscillators 13a as described above. During each ping (i.e., transmission / reception period), the transducer 13 transmits ultrasonic waves as the transmission beam TB1 shown in FIG. 1, and receives the reflected waves at each ultrasonic oscillator.

[0066] In response to the control from the control unit 11, the transmission processing module 14 outputs a transmission signal to transmits the ultrasonic waves to the transducer 13 via the transmission / reception switching unit 16. As shown in FIG. 3, the transmission signal is a signal that oscillates at a predetermined amplitude for a fixed period. At one transmission time of the transmission beam TB1, the transmission signal is supplied to each ultrasonic oscillator 13a of the transducer 13 via the transmission / reception switching unit 16. As a result, as shown in FIG. 3, ultrasonic waves corresponding to the transmission signal are transmitted from each ultrasonic oscillator 13a. The pulse of ultrasonic waves transmitted at one transmission time is called transmission pulse.

[0067] The reception processing module 15 receives electric signal output by reception of the reflected ultrasonic waves from each ultrasonic oscillator 13a of the transducer 13 via the transmission / reception switching unit 16, and applies amplification and noise removal (i.e., bandpass filter) processing to the received electric signal. The reception processing module 15 outputs electric signal to which these processes have been applied to the control unit 11.

[0068] The transmission / reception switching unit 16 outputs the transmission signal output from the transmission processing module 14 to the transducer 13 (i.e., ultrasonic oscillator 13a) at the time of transmission of the transmission beam TB1, and outputs electric signal output from the transducer 13 (ultrasonic oscillator 13a) to the reception processing module 15 during a fixed period from the timing when transmission of the transmission beam TB1 is completed.

[0069] Although the transmission processing module 14 and the reception processing module 15 are illustrated one by one in FIG. 3, the above-described processing in the transmission processing module 14 and the reception processing module 15 is performed for each ultrasonic oscillator 13a arranged in the transducer 13. Therefore, electric signals, which are amplified and denoised in electric signal output from each ultrasonic oscillator 13 a, are individually input to the control unit 11. When these electric signal signals are input to the control unit 11, they are converted into digital signals with a predetermined sampling period by an A / D converter.

[0070] The display unit 17 includes a display device such as a liquid crystal display. The display processing module 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 an operation key or a mouse. The input processing module 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 comprise a liquid crystal panel in which a touch panel is superimposed on the liquid crystal display.

[0071] In this embodiment, the functions of a data generation module Ila, fish school tracking module 11b, fish quantity index calculation module 11c and an image generation module lid are given to the control unit 11 by the program stored in the storage unit 12.

[0072] The data generation module 1 la beamforms electric signal (i.e., digital signal) output from each ultrasonic oscillator 13a to form the reception beam RBI shown in FIG. 2, and generates the reception signal corresponding to the sound wave incident on the transducer 13 from the beam axis direction (the direction of a predetermined azimuth angle 0 and tilt angle (p) of each reception beam RBI. Furthermore, the data generation module Ila applies bandwidth limitation and envelope detection processing to the reception signal in each beam axis direction to obtain the envelope signal in each beam axis direction.

[0073] A band limiting process is a process for extracting the frequency component of the transmission signal output from the transmission processing module 14. This process is performed when the transmission signal output from the transmission processing module 14 is a constant frequency signal (CW signal).

[0074] On the other hand, when the transmission signal output from the transmission processing module 14 is not a constant frequency signal (CW signal) but a frequency-modulated chirp signal (FM signal), then the data generation module Ila applies matched filter processing to the reception signal in each beam axis direction instead of the band limiting process. Then, the data generation module Ila applies envelope detection processing to the signal after the matched filter processing to obtain envelope signals in each beam axis direction.

[0075] The envelope signals thus obtained are signals indicating the echo intensity (i.e., intensity of sound waves) that changes according to the elapsed time from transmission timing of the transmission beam TB1 (i.e., ultrasonic wave). Here, the elapsed time from transmission timing corresponds to the distance from the transducer 13 in each beam axis direction. The control unit 11 acquires the echo intensity from the position of each distance in each beam axis direction from the echo signals of each reception beam RBI by associating the elapsed time from transmission timing with the distance. The echo intensity is acquired at a predetermined distance resolution according to the sampling period. The data generation module Ila acquires digital data (i.e., non-negative real numbers) corresponding to the amplitude of the envelope signal at each sampling timing (distance) as amplitude data.

[0076] The data generation module Ila executes the above-described processing in reception period after transmission of the ultrasonic wave to generate a series of amplitude data. The operation of transmitting the ultrasonic wave and receiving the echo generated by this transmission in the subsequent reception period is called ping. A series of amplitude data is generated for each ping.

[0077] The fish school tracking module 1 lb tracks the fish school based on the amplitude data generated by the data generation module Ila. More specifically, the fish school tracking module 1 lb updates the initial tracking area set by the user for each ping based on the amplitude data and navigation data (i.e., ship speed, heading) from the navigation instrument.

[0078] If there is an echo of fish school (i.e., single group echo) to be tracked on the echo image displayed on the display unit 17, then the user specifies area via the input unit 19. For example, the user specifies a center position of the single group echo on the echo image. Thus, an area of a predetermined width centering on the center position is set as the initial tracking area. However, a method of setting the initial tracking area is not limited to this.

[0079] The fish school tracking module 1 lb updates the initial tracking area thus set so as to track fish school based on the amplitude data and navigation data (i.e., ship speed, heading) at the current ping, and sets the updated tracking area at the next ping. At the next ping, the updated tracking area is further updated based on the amplitude data and navigation data (i.e., ship speed, heading) at the next ping. Thus, the fish school tracking module 1 lb updates the tracking area for each ping.

[0080] Furthermore, in each ping, the fish school tracking module 1 lb estimates the fish school area where fish school exists from the amplitude data in the tracking area. Then, the fish school tracking module 1 lb sets the tracking area for the next ping based on area obtained by enlarging the estimated fish school area by a predetermined magnification. The fish school tracking processing will be described later with reference to FIG. 7. A setting method of fish school area will be described later with reference to FIG. 8.

[0081] Furthermore, the fish school tracking module 1 lb calculates the moving direction of the fish school based on the tracking result of fish school. More specifically, it calculates the latest moving state (i.e., direction and speed of movement) of the fish school based on the center position of fish school area in the current and past fixed period. The calculation method of the moving state of the fish school will be described later with reference to FIG. 14.

[0082] The fish quantity index calculation module 11c calculates the fish quantity index which may be an index of the total weight of fish contained in the fish school area based on the amplitude data in fish school area. Various methods may be used for calculating 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 filed by the applicant. In this case, a fish quantity index Q is calculated by the following equation.

[0083] FIG. 4 is a diagram for explaining a method of calculating the fish quantity index Q based on the above equation (1), according to the embodiment 1 of the present invention.

[0084] Here, a rectangular coordinate system is defined in which the beam number is the horizontal axis and the sample number is the vertical axis.

[0085] The beam number is a number assigned to the reception beam RBI. For example, in plan view, 0 is assigned to beam number (j) of the reception beam RBI facing the stern direction, and 1, 2, 3, ... are assigned to beam number (j) of the reception beam RBI in the order of increasing angle between the stern direction (i.e., reference direction) and the beam axis direction with the clockwise direction being positive in plan view. In this case, if the total number of reception beam RBI is 128, then the beam numbers (j) of the reception beam RBI facing the port, bow, and starboard directions are 32, 64, and 96, respectively.

[0086] The sample number indicates the order in which envelope signals corresponding to each reception beam RBI are sampled. The sample number corresponds to the distance from the origin (i.e., position of the transducer 13). A sample number (n) is assigned to each sampling time of the envelope signal in the order of time. The reference time is transmission start time of the transmission beam TB1, that is, the moment when the leading edge of transmission pulse is emitted from the transducer 13, and the sample number (n) at this time is set to 0.

[0087] A(j, n) in equation (1) is amplitude data at the positions of beam number (j) and sample number (n). ro is unit distance and defined as 1 m. rn is the distance (unit: m) from the origin of the position corresponding to the time tn at which the nth amplitude data is sampled, a is the absorption coefficient (Attenuation of sound waves per unit distance, unit: dB / m).

[0088] When a fish school area Al is set in the rectangular coordinate system as shown in FIG. 4, then the group of amplitude data A(j, n) included in this fish school area Al is calculated in the parentheses of equation (1), and the sum of these calculation results is obtained. The obtained sum is then multiplied by Co, Ccor, and l / VUnit to calculate the fish quantity index Q.

[0089] The coefficient Vunit is referred to as point spread coefficient. When there is one target on the scanning plane SP1, in the rectangular coordinate system shown in FIG. 4, then the normalized amplitude data A'(j, n) due to this target is generated behind this target (upper side in FIG. 4). The normalized amplitude data A'(j, n) is expressed by the following equation. Io in the following equation is transmission pulse strength (unit: micropascal squared). A'(j,n) = io+o1^1a( / -,n) -(2) v      v                  y

[0090] If a target strength Ts of the target is 1, then the maximum value of the normalized amplitude data A'(j, n) caused by the target is 1. The sum of the squared values of the normalized amplitude data A'(j, n) is point spread coefficient Vunit.

[0091] A coefficient Co is obtained as an approximate number of W / (2Io • k2 • Ts) from the target strength Ts and weight W of the single fish, a strength Io of transmission pulse and reception sensitivity k of the device. The approximate number may be a value obtained by substituting the values of W and Ts for the representative fish and the design values of Io and k for the underwater detection device 10, or it may be a value obtained in advance so that the catch estimated by fisherman or the actual catch agrees well with the fish quantity index Q.

[0092] A coefficient Ccor is fish quantity correction coefficient. This fish quantity correction coefficient Ccor reflects fish quantity correction magnification input from the user such as fisherman. The fish quantity index calculation module 11c calculates the fish quantity index Q by setting the fish quantity correction coefficient Ccor to an initial value of 1 until the fish quantity correction magnification is first input. Each time fish quantity correction magnification is input, the fish quantity index calculation module 11c updates the value of the fish quantity correction coefficient Ccor by the following equation.

[0093] "New Ccor" = "fish quantity correction magnification" x "Old Ccor"

[0094] That is, the fish quantity index calculation module 11c calculates the fish quantity index Q by using the value obtained by multiplying the fish quantity correction coefficient Ccor immediately before correction magnification is input by the fish quantity correction magnification as a new fish quantity correction coefficient Ccor.

[0095] In order to suppress the difference between the displayed the fish quantity index Q and the actually captured fish quantity, the user inputs the fish quantity correction magnification via the input unit 19. In this way, the fish quantity correction magnification input from the user is reflected in the fish quantity correction coefficient Ccor, and calculation formula (1) of the fish quantity index Q may 15 be corrected so as to approach the actual capture quantity based on the input fish quantity correction magnification. Therefore, by repeating the input of fish quantity correction magnification, the fish quantity index Q may be brought closer to the fish quantity corresponding to the approximate value of the user. Thus, the fish quantity index Q corresponding to the user's fishing ground, species of fish, and season may be smoothly and properly displayed on the display unit 17.

[0096] A method for calculating fish quantity index is not limited to the above, and for example, the method described in Japanese Patent Application Laid-Open Publication No. 2009-300220 may be used.

[0097] Referring back to FIG. 3, the image generation module lid generates the echo image for displaying the echo intensity from each distance position in each beam axis direction on a predetermined color scale. The image generation module lid sequentially outputs the echo image generated for each ping to the display processing module 18. As a result, the echo image updated every ping is displayed on the display unit 17. In addition, the image generation module 1 Id generates a display image including information based on the fish quantity index, as described later.

[0098] FIG. 5 is a diagram schematically showing an example of an echo image displayed on the display unit 17, according to the embodiment 1 of the present invention.

[0099] In the mode for displaying the echo image, the screen of the display unit 17 is divided into area All and A12. Among them, an echo image P10 is displayed on the area All. Here, the echo image P10 is displayed as an image when the ship SI is viewed from directly above. An image Pl 1 of the ship SI is arranged in the center of the echo image P10, and furthermore, a track P12 of the ship SI so far is shown. A straight line P13 indicating the bow direction of the ship SI is included in the echo image P10.

[0100] Further, in the echo image P10, a certain distance range from the position of own ship (i.e., image Pll) is shown by circular boundary lines P14, P15, and P16. The diameters of the boundary lines P14, P15, and P16 are, for example, 200 m, 400 m, and 600 m. In the echo image P10, the above-described echo intensity is displayed in the predetermined color scale. In FIG. 5, hatching is applied to the area where the echo intensity is high. For example, a hatched area P17 is the area where the echo intensity is high. The hatched area is the area where fish school may exist.

[0101] The area A12 is divided into a plurality of upper and lower sections, and information showing present position of the ship SI (i.e., Longitude, Latitude), water temperature in present position, and a graph showing the temporal change of water temperature are displayed on each divided area. In FIG. 5, the display of these images on the area A12 is omitted for convenience.

[0102] FIG. 6 is a flowchart showing the processing of generating data related to echo intensity, according to the embodiment 1 of the present invention.

[0103] The process shown in FIG. 6 is executed by the control unit 11 mainly by the function of the data generation module Ila. FIG. 6 shows the process in 1 ping. The control unit 11 executes the process shown in FIG. 6 for each ping.

[0104] The control unit 11 causes the plurality of ultrasonic oscillators 13a included in the transducer 13 to transmit ultrasonic waves at transmission timing at predetermined intervals (Sil). Based on electric signal output from the plurality of ultrasonic oscillator 13a during the reception period after transmission timing, the control unit 11 forms the plurality of reception beams RB 1 in the scanning plane SP1 (i.e., scanning range) having the position of the transducer 13 as the origin, and generates data on echo intensity at each position of the scanning plane SP1 (i.e., scanning range) (a position defined by the azimuth angle of each reception beam RB 1 and the distance from the origin) (S12). Here, amplitude data is generated as data on echo intensity as described above.

[0105] FIG. 7 is a flowchart showing the fish school tracking processing, according to the embodiment 1 of the present invention.

[0106] In the flowchart of FIG. 7, the processing of steps S102, S103, S105 to SI 10 is performed by the function of the fish school tracking module 1 lb, and the processing of step SI 04 is performed by the function of the fish quantity index calculation module 11c. In the following description, it is assumed that the control unit 11 performs each processing by these functions.

[0107] With respect to the echo image P10 shown in FIG. 5, when the user designates the area of fish school (i.e., initial tracking area) to be tracked via the input unit 19 and performs a tracking start operation, then the control unit 11 determines whether the current ping is the first ping after the tracking start (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 fish school area Al from the amplitude data in the set initial tracking area A0.

[0108] FIG. 8 is a diagram showing the setting method of the fish school area Al, according to the embodiment 1 of the present invention.

[0109] The tracking area A0 is developed in the rectangular coordinate system of FIG. 8. This rectangular coordinate system is similar to the rectangular coordinate system shown in FIG. 4. The tracking area A0 is defined by the following parameters: width W01 parallel to the horizontal axis, width W02 parallel to the vertical axis, and center point C01. The width W01 corresponds to an angular width in the azimuthal direction, and the width W02 corresponds to a length in the distance direction.

[0110] The control unit 11 calculates a volume scattering intensity SV for each amplitude data included in the tracking area A0. Sound waves attenuate with distance due to spherical diffusion and absorption. Due to this attenuation, the amplitude data also decreases with distance. The volume scattering intensity SV is the reflectance per unit volume of the echo source (i.e., fish school or plankton group), and is obtained by correcting the amplitude data to compensate for these attenuation.

[0111] The control unit 11 calculates the sum Se(j) of the volume scattering intensity SV by adding the volume scattering intensity SV within width W02 for each column of beam number (j) included in width W01. In FIG. 8, an example of the sum Se(j) obtained for each beam number (j) is shown in waveform below the tracking area AO. A straight line below the waveform indicates a level where the sum Se(j) is 0. Strictly speaking, the sum Se(j) is scattered for each beam number (j), but here, for convenience, a waveform is shown in which these plots of the sum Se(j) are connected by a curve.

[0112] The control unit 11 calculates the sum Sr(n) of the volume scattering intensity SV by adding the volume scattering intensity SV within the width W01 for each row of sample number (n) included in width W02. In FIG. 8, an example of the sum Sr(n) obtained for each sample number (n) is shown in waveform on the right side of the tracking area A0. A straight line to the right of the waveform indicates a level where the sum Sr(n) is 0. Strictly speaking, the sum Sr(n) is scattered for each sample number n, but here, for convenience, a waveform is shown in which these plots of the sum Sr(n) are connected by a curve.

[0113] The control unit 11 extracts a maximum value MAXI of the sum Se(j), and sets the value obtained by multiplying this maximum value MAXI by a predetermined magnification (For example, 0.1) to threshold value TH1. Similarly, the control unit 11 extracts a maximum value MAX2 of the sum Sr(n), and sets the value obtained by multiplying this maximum value MAX2 by a predetermined magnification (For example, 0.1) to threshold value TH2. Here, the magnification is set to a value that may extract the volume scattering intensity SV from the fish school by distinguishing it from noise and the like. The magnification is set to an appropriate value based on the actual measurement.

[0114] Among the waveforms shown below the tracking area A0, the portion where the value of threshold value TH1 or more is taken continuously is called a mountain, and among the waveforms shown to the right of the tracking area A0, the portion where the value of threshold value TH2 or more is taken continuously is called a mountain.

[0115] The control unit 11 sets the horizontal width range of the mountain waveform including the maximum value MAXI among the mountain waveforms on the waveforms shown below the tracking area A0 to the width Wil in the horizontal axis direction (i.e., azimuthal direction) of the fish school area Al. More specifically, the range between the beam number (j) closest to one boundary and the beam number (j) closest to the other boundary of this horizontal width range is set to the width Wil in the horizontal axis direction (i.e., azimuthal direction) of the fish school area Al. In this case, if there is also a mountain waveform outside the range of the mountain waveform including the maximum value MAXI, then the horizontal width range including the prescribed mountain waveform from the mountain waveform including the maximum value MAXI may be set to the width W11 in the horizontal axis direction (i.e., azimuthal direction) of the fish school area Al. Also in this case, the range between the beam number (j) closest to the two boundaries of this horizontal width range is set to the width Wil in the horizontal axis direction (i.e., azimuthal direction) of the fish school area Al.

[0116] Similarly, in the vertical axis direction (i.e., distance direction), the control unit 11 sets the width W12 in the vertical axis direction (i.e., distance direction) of the fish school area Al based on the mountain waveform on the waveform shown to the right of the tracking area AO.

[0117] Furthermore, the control unit 11 sets a center point Cl 1 of the rectangular fish school area Al defined by the widths W11 and W12. Thus, the setting of fish school area Al is completed. The fish school area Al is defined by the parameters of the width Wil, the width W12, and the center point C11. The width Wil corresponds to the angular width in the azimuthal direction, and the width W12 corresponds to the length in the distance direction.

[0118] FIG. 9 is a diagram showing a setting example (actual measurement) of the fish school area Al for the tracking area A0, according to the embodiment 1 of the present invention.

[0119] Figure 9 shows a rectangular coordinate system with the horizontal axis set to azimuth 9 (i.e., corresponding to beam number (j)) and the vertical axis set to 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 (-70dB) is black and the highest value (-30dB) is red. The middle value of the scale is green. The scale goes from the lowest value of black to blue, light blue, green, and yellow to the highest value of red. For convenience, FIG. 9 shows a grayscale version of the original figure.

[0120] In FIG. 9, a rectangular area surrounded by two outer vertical lines V01 and V02 and two outer horizontal lines H01 and H02 is the tracking area A0, and a rectangular area surrounded by two inner vertical lines VI1 and V12 and two inner horizontal lines Hl 1 and H12 is the fish school area Al. The fish school area Al is included in the tracking area A0 and is smaller than the tracking area A0. The area Al of fish school, which has a high volume scattering intensity SV, is generally included in fish school area Al.

[0121] Returning to FIG. 7, the control unit 11 calculates the fish quantity index Q based on the amplitude data included in the fish school area Al (S104). The method of calculating fish quantity index Q is as described above.

[0122] Next, the control unit 11 calculates an index value indicating how much the echo intensity of the entire tracking area A0 is greater than the echo intensity around the tracking area A0 (SI 05). Here, the reverberation contrast is calculated as the index value.

[0123] When the underwater detection device 10 detects the fish school near the sea surface from the distance, it detects a range where the tilt angle is about 0°. In this case, reverberation echo such as reflected wave from the sea surface (i.e., sea surface reflection) may be distributed over a wide range including the range of echo from the fish school (i.e., fish school echo).

[0124] The reverberation contrast is a parameter indicating the degree to which reverberation echo, which is stronger than or equal to the fish school echo, is distributed over a wide range including the tracking area A0. The reverberation contrast may be said to be a parameter indicating the degree to which the echo of the tracking area A0 is larger than that of the surrounding area. Here, the reverberation contrast is calculated such that the higher the degree of distribution of the reverberation echo, which is as strong as or stronger than fish school echo, over a wide range including the tracking area A0, the smaller reverberation contrast.

[0125] FIG. 10 is a diagram showing the calculation method of the reverberation contrast, according to the embodiment 1 of the present invention.

[0126] Here, four reference area RI to R4 are defined which touch each of the four sides of the tracking area A0. The control unit 11 calculates average value SVao of the volume scattering intensity SV in the tracking area A0, and further calculates average value SVai to SVa4 of the volume scattering intensity SV for each of the reference area RI to R4. Then, the control unit 11 calculates the value obtained by dividing average value SVao (i.e., first average value) by the maximum value of average value SVai to SVa4 (i.e., second average value) as the reverberation contrast.

[0127] FIG. 11 is a diagram showing the distribution state of the volume scattering intensity SV when the reverberation contrast is relatively large, according to the embodiment 1 of the present invention and FIG. 12 is a diagram showing the distribution state of the volume scattering intensity SV when the reverberation contrast is relatively small, according to the embodiment 1 of the present invention. In FIGS. 11 and 12, the volume scattering intensity SV is mapped on the same rectangular coordinate system as in FIG. 9 on the same scale as in FIG. 9. In FIG. 12, the fish school area Al is approximately as wide as the tracking area A0.

[0128] As shown in FIG. 11, when the reverberation contrast is relatively large, an extent to which the reverberation echo which is as strong as or stronger than the fish school echo is distributed over a wide range including the tracking area A0 is small. On the other hand, as shown in FIG. 12, when the reverberation contrast is relatively small, the strong volume scattering intensity SV based on the reverberation echo such as sea surface reflection is widely distributed above and below and to the right of the tracking area A0, and the degree to which the reverberation echo which is as strong as or stronger than fish school echo is distributed over a wide range including the tracking area A0 is large. From these actual measurement results, it may be confirmed that the reverberation contrast calculated by the above method is a parameter indicating the degree to which the reverberation echo which is as strong as or stronger than the fish school echo is distributed over a wide range including the tracking area AO.

[0129] Note that the method of calculating the reverberation contrast is not limited to the method shown in FIG. 10. For example, the value obtained by dividing average value SVao by average value of average value SVai to SVa4 may be used as the reverberation contrast. Alternatively, the reference area RI to R4 may be set so that the total area of the reference area RI to R4 is equal to the area of the tracking area A0, and the value obtained by dividing the total volume scattering intensity SV of the tracking area A0 by the total volume scattering intensity SV of the reference area RI to R4 may be calculated as reverberation contrast.

[0130] Referring back to FIG. 7, the control unit 11 executes the reverberation contrast test using the reverberation contrast calculated in step SI05 (SI06). Specifically, the control unit 11 determines whether the reverberation contrast is equal to or greater than a predetermined reverberation threshold.

[0131] If the reverberation contrast is equal to or greater than the reverberation threshold (SI07: YES), the control unit 11 enlarges the fish school area Al set in step SI03 by a predetermined magnification greater than 1 to constitute a new tracking area A0 (SI08). Specifically, while maintaining the center point C11 in FIG. 8, the control unit 11 enlarges the widths W11 and W12 by the above-mentioned magnification to constitute the 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 Al.

[0132] On the other hand, if the reverberation contrast is less than the reverberation threshold (SI07: NO), the control unit 11 skips step SI08 and maintains the current tracking area A0 as the tracking area A0 of the next ping.

[0133] In step S108, by configuring the new tracking area A0 based on the fish school area Al, the new tracking area A0 may be positioned at a position shifted from the original tracking area A0 to a position corresponding to fish school. In addition, since the new tracking area A0 is an enlarged fish school area Al at a predetermined magnification greater than 1, even if the shape of fish school itself changes or fish school is enlarged and deformed by integrating other small fish school, the amplitude data of the enlarged or deformed fish school may be easily included in the new tracking area A0. Thus, the fish school echo may be smoothly tracked.

[0134] However, if the process of step SI08 is repeated in a state where the reverberation echoes as strong as or more than the fish school echoes are distributed over a wide range including the tracking area A0, then the tracking area A0 may continue to be enlarged with each ping due to the influence of the surrounding reverberation echoes and become a range several stages wider than the original fish school echo range. If this occurs, the fish school area Al may not be properly set.

[0135] Therefore, in the process of FIG. 7, if the reverberation contrast is less than the reverberation threshold (SI07: NO), step SI08 is skipped, and the tracking area A0 using the current tracking area A0 is set as area for setting the tracking area A0 of the next ping. Thus, in a state where the reverberation echoes which are as strong as or stronger than fish school echo are distributed over a wide range including the tracking area A0, excessive expansion of the tracking area A0 by the process of step 108 is suppressed.

[0136] From this viewpoint, the reverberation threshold is set on the condition that the fish school area Al may be properly set by the volume scattering intensity SV in the tracking area A0, and that the new tracking area A0 may be properly configured based on this fish school area Al. That is, the lower limit of the reverberation contrast which may satisfy this condition is set to reverberation threshold. In other words, the reverberation contrast when the degree to which the reverberation echo which is stronger than or equal to the fish school echo is distributed over a wide range including the tracking area A0 is at the upper limit which may satisfy this condition is set to the reverberation threshold. The reverberation threshold may be set based on actual measurement.

[0137] Subsequently, the control unit 11 determines whether or not an instruction to end tracking of the fish school has been input from the user (S109). If an end instruction has been input (S109: YES), the control unit 11 ends the process of FIG. 7. If no end instruction is input (S109: NO), the control unit 11 returns the process to step S101 and executes the process for the next ping.

[0138] Since the determination in step S101 is NO for the next and subsequent pings, step SI 10 is executed. In step SI 10, 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 SI between the previous ping and the current ping, the position of ship SI is displaced and the direction (i.e., azimuth) of the ship SI is rotated. As a result, the origin of the scanning plane SP1 is shifted and the scanning plane SP1 is rotated about the center axis of the transducer 13.

[0139] In step SI 10, processing is performed to correct (i.e., project) the position on the earth of tracking area A0 configured for the current ping in the previous ping to the 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 (i.e., coordinate position specified by 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 with the center point C01 after projection to set the tracking area A0 after correction for the current ping.

[0140] The tracking area AO corrected in step SI 10 is tracking area AO configured in step S108 if the determination in step SI07 in the previous ping is YES, and the tracking area AO used in the previous ping if the determination in step SI 07 in the previous ping is NO.

[0141] After correcting the tracking area AO in this way, the control unit 11 executes processing from step SI03 onwards. The control unit 11 repeatedly executes the processes of steps SI 10 and S103 to S108 until an instruction to terminate the tracking of fish school is input from the user (S109: NO). Thus, the fish school area Al and the fish quantity index Q and the tracking area A0 are updated for each ping. After that, when an instruction to terminate the tracking of fish school is input from the user (S109: YES), the control unit 11 terminates the process according to the flowchart of FIG. 7.

[0142] In parallel with the process of FIG. 7, the control unit 11 (i.e., image generation module lid) executes the process of generating the display image in which the information based on the fish quantity index Q calculated in step S104 is associated with the swimming path of the fish school. This display image is displayed on area Al 1 in FIG. 5, for example, by the user's screen switching operation. The screen including this display image may be displayed superimposed on the screen of the echo image P10 of area All.

[0143] FIG. 13 is a flowchart showing the process of generating a display image including fish quantity information, according to the embodiment 1 of the present invention.

[0144] Among the processes in FIG. 13, the process in step S25 is performed by the function of the fish school tracking module 1 lb, and the other processes are performed by the function of the image generation module lid. In the following description, it is assumed that the control unit 11 performs the process in FIG. 13 using these functions.

[0145] When the 1-ping operation is completed (S21: YES), the control unit 11 links the fish quantity index Q calculated in step SI 04 in FIG. 7 with the center point Cl 1 of the fish school area Al from which the fish quantity index Q was obtained, and stores them in the storage unit 12 (S22). Next, the control unit 11 acquires the position of own ship (i.e., Longitude, Latitude) from the navigation instruments, stores it in the storage unit 12, and updates the cruising path of own ship (track) on the display image based on the history of the current position of own ship and the previous positions of own ship (S23). Furthermore, the control unit 11 updates the swimming path of fish school on the display image based on the history of the current center point Cl 1 of fish school area Al and the previous center point Cl 1 (S24).

[0146] Furthermore, the control unit 11 calculates the current movement state of fish school (i.e., direction and speed of movement) from the history of the current center point Cl 1 of the fish school area Al and the previous center point Cl 1 (S25), and updates the display of the movement state of the fish school (i.e., direction and speed of movement) on the display image (S26).

[0147] FIG. 14 is a diagram showing a method for calculating the movement status of the fish school, according to the embodiment 1 of the present invention.

[0148] In FIG. 14, the center point Cl 1 of the fish school area Al is plotted on the x-y coordinate plane corresponding to the X-Y plane of FIG. 1. Here, the movement direction of the fish school is calculated using the center point Cl 1 obtained in the current ping and the pings up to 5 times before this. The timing corresponding to the current ping is indicated by tl, and the timing corresponding to the pings 5 times before this is indicated by t2

[0149] For example, a regression line LI is calculated for a plot on the x-y coordinate plane by the least square method. On this regression line LI, a point Pl having the same x value (xl) as the plot at timing tl and a point P2 having the same x value (x2) as the plot at timing t2 are set, and the direction from point P2 to point Pl is obtained as the movement direction of the fish school. The distance between points Pl and P2 is calculated based on the three-square theorem from the difference Ax in the x-axis direction between points Pl and P2 and the difference Ay in the y-axis direction between points Pl and P2. Then, the calculated distance is divided by the time difference between the timings tl and t2 to calculate the moving speed of the fish school. Thus, the current moving state of the fish school (i.e., direction and speed of movement) is calculated.

[0150] Note that the moving state of the fish school may not necessarily include both the moving direction and the moving speed. For example, the moving state of the fish school may include only the moving direction. The method for calculating the moving state of the fish school is not limited to the method shown in FIG. 14, and the moving state of the fish school may be calculated using other methods.

[0151] Referring back to FIG. 13, the control unit 11 determines whether or not the center point Cl 1 of the fish school acquired in the current ping (i.e., present position of fish school) corresponds to the new display position of fish quantity information based on the fish quantity index Q (S27). If present position of the fish school corresponds to the new display position (S27: YES), the control unit 11 updates the display image so that the fish quantity information based on the fish quantity index Q is associated with present position of the fish school on the swimming path (S28).

[0152] Here, the display position is set at a fixed distance interval, for example, on the swimming path of fish school. If the user may change the magnification (scale) of the display image, the distance interval may be changed according to the magnification (scale). Alternatively, the display position may be set at a fixed time interval (i.e., time interval corresponding to a fixed number of pings). In this case, the time interval may also be changed according to the magnification of the display image. The distance interval and the time interval may be adjusted so that the fish quantity information is displayed at an interval that is easy to see on the display image.

[0153] The fish quantity information displayed at each display position is generated so as to reflect the value of fish quantity index stored in association with the center point Cl 1 corresponding to each display position in the storage unit 12. Alternatively, the fish quantity information may be generated from the value of fish quantity index stored in association with the center point Cl 1 corresponding to each display position and the center point Cl 1 in the vicinity thereof.

[0154] In this case, for example, from the value of fish quantity index at the display position of the object and the values of a plurality of fish quantity indices linked to a position on the swimming path (i.e., center point Cll) included in a distance range smaller than the distance interval in the longitudinal direction of the swimming path with respect to the display position of the object, then a representative value (i.e., average value, median or mode, etc.) of these values is calculated, and the fish quantity information of the display position is generated so as to reflect the representative value. Here, the distance range may be set to, for example, about half of the distance interval.

[0155] Alternatively, instead of this method, for example, from the value of the fish quantity index at the display position of the object (i.e., center point Cll) and the value of the fish quantity index linked to a position on the swimming path between the display position of the object and the immediately preceding display position (i.e., center point Cll), then the representative value (i.e., average value, median or mode, etc.) of these values is calculated, and the fish quantity information of the display position may be generated so as to reflect the representative value.

[0156] In these two fish quantity information generation methods, the integrated value of the fish quantity index values may be calculated instead of the representative value, and the fish quantity information of the display position may be generated so as to reflect the integrated value.

[0157] The control unit 11 repeatedly executes the process of steps S21 to S28 until the underwater detection device 10 terminates the display operation of the fish quantity information (S29: NO). Thus, while the position and the cruising path of own ship and the swimming path and movement status of the fish school are updated, the fish quantity information is displayed in association with each updated display position on the swimming path.

[0158] The start and end of the display operation of the fish quantity information are instructed by the user via, for example, the input unit 19. The control unit 11 starts the process shown in FIG. 13 in response to the instruction to start the display operation of the fish quantity information, and ends the process shown in FIG. 13 in response to the instruction to end the display operation of the fish quantity information (step S29: YES). Alternatively, the start and end of the underwater detection device 10 may be the start and end of the display operation of the fish quantity information. When the user designates a plurality of fish school to be tracked, the processes shown in FIGS. 7 and 13 may be executed for each designated fish school. In this case, the display image includes the cruising path of own ship, the swimming path for each fish school, the movement status of fish school, and the fish quantity information.

[0159] FIG. 15 is a diagram schematically showing an example of a display image 100 including fish quantity information based on fish quantity index, according to the embodiment 1 of the present invention.

[0160] In response to the display instruction of the display image 100 via the input unit 19, the display image 100 of a predetermined area generated by the image generation module 1 Id is displayed on the display unit 17 of the underwater detection device 10. As described above, the user may be able to change the magnification (i.e., scale) of the display image 100 via the input unit 19. In this case, area displayed on the display unit 17 changes according to the change of the magnification.

[0161] The display image 100 includes a cruising path 110 to present position in own ship, a plot 111 showing present position in own ship, and a swimming path 120 in the fish school. As described above, the swimming path 120 is the moving trajectory of the center point Cll of the fish school projected on the X-Y plane. By the process shown in FIG. 13, the cruising path 110 and the plot 111 (i.e., present position plot 111) and the swimming path 120 are updated every ping.

[0162] Furthermore, an arrow 130 indicating the moving state of the fish school (i.e., direction and speed of movement) is added to the tip of the swimming path 120. The direction of the arrow 130 indicates the moving direction of fish school, and the length of the arrow 130 indicates the moving speed of the fish school. The length of the arrow 130 increases as the moving speed increases. A numerical value indicating the moving speed may be added next to the arrow 130.

[0163] In addition, the fish quantity information based on the fish quantity index is sequentially displayed at each display position on the swimming path 120. Here, a fish quantity image 141-143 is superimposed on each display position as the fish quantity information. As described above, the interval between each display position may be changed according to the magnification of the display image 100. By the process shown in FIG. 13, the arrow 130 and the fish quantity image 141-143 fish quantity information (i.e. fish quantity information,) are updated every ping.

[0164] In the example of FIG. 15, the fish quantity image 141-143 is composed of a circle whose diameter and color correspond to the value of fish quantity index. The larger the value of the fish quantity index, the larger the diameter of the circle. In FIG. 15, for convenience, the difference in color of the fish quantity image 141-143 is indicated by the difference in hatching. For example, the fish quantity image 141 is colored red, the fish quantity image 142 is colored yellow, and the fish quantity image 143 is colored blue.

[0165] For example, the diameter of the circle is set in three stages using three threshold value Thl to Th3 (Thl<Th2<Th3). When the value of the fish quantity index is threshold value Thl or more and less than threshold value Th2, the diameter DI is used, when the value of the fish quantity index is threshold value Th2 or more and less than threshold value Th3, the diameter D2 is used, and when the value of the fish quantity index is threshold value Th3 or more, the diameter D3 is used (D1<D2<D3). The threshold value Thl to Th3 may be arbitrarily set by the user.

[0166] However, the method of setting the diameter is not limited to this, for example, the diameter may be set in four stages or more, and the diameter may change linearly according to the change of the value of the fish quantity index. When the diameter changes linearly in this way, the color of fish quantity image may change by a color scale whose hue continuously changes according to the change of the value of fish quantity index.

[0167] The user may grasp the movement path of fish school so far from the swimming path 120 included in the display image 100, and the current movement state of fish school from the arrow 130. The user may grasp fish quantity in the swimming path 120 and its change from the fish quantity image 141-143. Furthermore, the user may grasp the positional relationship between the own ship and the fish school from the cruising path 110 and the swimming path 120.

[0168] The user may judge whether the fish school should be captured from the fish quantity image 141-143, and may predict the moving position of fish school from the swimming path 120 and the arrow 130. The user may grasp the position to advance own ship when capturing fish school from the positional relationship between the swimming path 120 and the plot 111. Therefore, the user may smoothly capture the fish school.

[0171] In the example of FIG. 15, the fish quantity image 141-143 is a circular image whose diameter and color differ from each other, but the fish quantity image 141-143 may be a circular image whose diameter only differs from each other, or the circular image whose color only differs from each other. The user may grasp fish quantity on the swimming path 120 of the fish school from the fish quantity image 141-143 by these display modes.

[0169] The display image 100 of FIG. 15 may be superimposed on the echo image P10 in the screen of FIG. 5, or may be arranged on any of the divided area of area A12 in the screen of FIG. 5. Another Display Method of fish quantity Information

[0170] In the display image 100 of FIG. 15, the fish quantity information was displayed by the fish quantity image 141-143, but the display method of the fish quantity information is not limited thereto.

[0171] For example, as in another display method 1 shown in FIG. 16, a fish quantity image 144-146 may be composed of bands having width (i.e., width in the direction perpendicular to the swimming path 120) and color according to the value of fish quantity index. In FIG. 16, as in the case of FIG. 15, the difference in color is indicated by the difference in hatching.

[0172] In the example of FIG. 16, as in the example of FIG. 15, the width of fish quantity image 144-146 is set to three stages according to the relationship between the value of fish quantity index and threshold value Thl to Th3. In the example of FIG. 16, the fish quantity images 144- 146 of a series of display positions having the same width are integrated and displayed as one band. As in the example of FIG. 15, the width of fish quantity image does not have to be three stages, and may change linearly according to the change in the value of fish quantity index.

[0173] With the display image 100 of FIG. 16, the fish quantity at each position on the swimming path 120 of the fish school may be grasped from the fish quantity image 144-146 included in the display image 100. Therefore, the user may smoothly judge whether the displayed fish school should be captured.

[0174] In the example of FIG. 16, the fish quantity image 144-146 is a band image whose width and color differ from each other, but the fish quantity image 144-146 may be a band image whose width only differs from each other, or may be a band image whose color only differs from each other. The user may grasp the fish quantity on the swimming path 120 of the fish school from the fish quantity image 144-146 with these display modes.

[0175] In addition, like another display method 2 shown in FIG. 17, the transparency of fish quantity image 141-143 may be increased with the passage of time in the display method of FIG. 15. That is, compared with the fish quantity image 141-143 near present position of the fish school, the fish quantity image 141-143 far from the present position of the fish school may be lightened in color to increase transparency. Similarly, like another display method 3 shown in FIG. 18, in the display method of FIG. 16, the transparency of the fish quantity image 144-146 may be increased as time passes. For convenience, in FIGS. 17 and 18, the transparency is expressed by the density of hatches.

[0176] According to this display method, the faster fish school moves, the longer fish quantity images 141-143 and 144-146 are displayed. Thus, the user may intuitively grasp the speed of fish school's movement from the length of the tail in the fish quantity image. In addition, the fish quantity images 141-143 and 144-146 are displayed so that the closer they are to the present position of the fish school, the darker they become. Thus, the user may intuitively grasp the direction of fish school's movement from the direction in which the shading changes.

[0177] In addition, as shown in another display method 4 of FIG. 19, a value 147 of the fish quantity index may be displayed at the position (here, one display position) on the swimming path 120. In this case, for the position on the swimming path 120 specified by the user (indicated by X in FIG. 19), the value 147 of the fish quantity index (unit: ton) at that position is appended. In addition, the circular fish quantity image 141 corresponding to this position is highlighted.

[0178] According to this display method, the user may accurately grasp fish quantity at the position on the swimming path 120 as a numerical value.

[0179] In the example of FIG. 19, when the user designates an arbitrary display position on the swimming path 120, the value 147 of the fish quantity index at that position is displayed. However, the value 147 of the fish quantity index at that position may be displayed in response to the user designating the arbitrary position on the swimming path 120.

[0180] The value of fish quantity index need not necessarily be displayed in response to the user's designation. For example, the control unit 11 (i.e., image generation module lid) may display the value 147 of the fish quantity index at a display position where the value of the fish quantity index is equal to or greater than the predetermined threshold value (For example, threshold value Th3). In addition, instead of the fish quantity image 141-143, the value 147 of the fish quantity index may be displayed at each display position.

[0181] Alternatively, in a state where the fish quantity image 141-143 is omitted from the display image 100 of FIG. 15, when the user designates the desired position on the swimming path 120, then the value 147 of the fish quantity index at that position may be displayed. Similarly, in a state where the fish quantity image 141-143 is omitted from the display image 100 of FIG. 15, when the user designates the desired position on the swimming path 120, then the fish quantity image 141-143 or the fish quantity image 144-146 corresponding to the value of fish quantity index at that position may be displayed, and the value 147 of fish quantity index at that position may be displayed together with the fish quantity image.

[0182] In addition, as shown in another display method 5 of FIG. 20, when the value of fish quantity index is equal to or greater than the predetermined threshold value, the fish quantity information may be displayed. Here, the fish quantity images 141 and 142 (i.e., fish quantity information) are displayed at the display position on the swimming path 120 where the value of fish quantity index is equal to or greater than threshold value Th2.

[0183] According to this display method, the display of fish quantity information where the fish quantity index is less than the predetermined threshold value is omitted from the display image 100. Therefore, the user may smoothly grasp the position on the swimming path 120 where the fish quantity larger than threshold value has occurred.

[0184] In another display method 5, the threshold value for displaying the fish quantity information may be arbitrarily set by the user. In another display method 5, as in another display method 4, the value 147 of the fish quantity index may be displayed together with the fish quantity images 141 and 142, or the value 147 of the fish quantity index may be displayed instead of the fish quantity images 141 and 142. Effects of Embodiments

[0185] According to the above embodiment, the following effects may be achieved.

[0186] As shown in FIG. 3, the underwater detection device 10 (i.e., fish quantity information display device) is provided with the transmission processing module 14 which causes the plurality of ultrasonic oscillator 13a included in the transducer 13 installed on the bottom of the ship to transmit ultrasonic waves at transmission timings at predetermined intervals, the data generation module Ila which forms the plurality of reception beams in the scanning range based on electric signal output from the plurality of ultrasonic oscillators 13a during the reception period after transmission timing and generates data on the echo intensity at each position of the scanning range, the fish school tracking module 1 lb which tracks the fish school based on the data, the fish quantity index calculation module 11c which calculates the fish quantity index of fish school based on the data, and the image generation module lid which generates the display image 100 in which the fish quantity information (i.e., fish quantity image 141-143) based on fish quantity index is associated with the swimming path 120 of fish school based on the tracking of fish school and the fish quantity index.

[0187] According to this configuration, as shown in FIG. 15, the fish school information (i.e., fish quantity image 141-143) is displayed in association with the swimming path 120 of fish school. Therefore, the user may grasp the present position of the fish school and the future movement of the fish school from the displayed swimming path 120, and the size of fish school and the change of the fish quantity from fish quantity information associated with the swimming path 120. Therefore, the user may more accurately grasp the position of the fish school and the fish quantity from the displayed image 100.

[0188] As described with reference to FIG. 14, the fish school tracking module 1 lb calculates the movement state (i.e., direction and speed of movement) of the fish school based on the tracking result of the fish school, and the image generation module lid further associates the movement state (arrow 130) of the fish school with the swimming path 120, as shown in FIG. 15.

[0189] With this configuration, the user may more smoothly grasp the position to which the fish school will move from the display of the movement state of the fish school (i.e., arrow 130) associated with the swimming path 120 in the displayed image 100. Thus, the user may advance own ship to that position and smoothly proceed to capture fish school.

[0190] As shown in FIGS. 15 to 20, the fish quantity information includes the fish quantity images 141-143 and 144-146 corresponding to the value of fish quantity index, and the image generation module lid associates the fish quantity images 141-143 and 144-146 with the predetermined position (i.e., display position) on the swimming path 120.

[0191] According to this configuration, the user may smoothly grasp the fish quantity at each position on the swimming path 120.

[0192] As shown in FIG. 15, the fish quantity image 141-143 may be a circle composed of at least one of a diameter and a color corresponding to the value of fish quantity index.

[0193] According to this configuration, the user may intuitively grasp the fish quantity at each position on the swimming path 120.

[0194] Alternatively, as shown in FIG. 16, the fish quantity image 144-146 may be a band composed of at least one of a width and a color corresponding to the value of fish quantity index.

[0195] According to this configuration, the user may intuitively grasp the fish quantity at each position on the swimming path 120.

[0196] Also, as shown in FIGS. 17 and 18, the transparency of the fish quantity images 141-143 and 144-146 may be adjusted so as to increase over time.

[0197] According to this configuration, the faster fish school moves, the longer fish quantity images 141-143 and 144-146 are displayed. Thus, the user may intuitively grasp the speed of fish school's movement from the length of the tail of fish quantity images 141-143 and 144-146. In addition, the fish quantity images 141-143 and 144-146 are displayed so that the closer they are to the present position of fish school, the darker they become. Thus, the user may intuitively grasp the “direction” of the movement of fish school from the “direction in which the shading changes”.

[0198] Further, as shown in FIG. 19, the fish quantity information may include the value 147 of fish quantity index, and the image generation module lid may display the value 147 of the fish quantity index at the predetermined position on the swimming path 120.

[0199] According to this configuration, the user may accurately grasp the fish quantity at a position on the swimming path 120 as a numerical value.

[0200] Furthermore, as shown in FIG. 20, the image generation module lid may display the fish quantity information (here, fish quantity images 141 and 142) when the value of fish quantity index is equal to or greater than the predetermined threshold value.

[0201] According to this configuration, since the display of fish quantity information whose fish quantity index is less than threshold value is omitted, the user may smoothly grasp the position on the swimming path 120 where a large fish quantity larger than the threshold value occurred.

[0202] As shown in FIGS. 7 and 10, the control unit 11 (i.e., fish school tracking module 11b) updates the tracking area A0 for tracking the fish school based on data based on fish school echo and navigation data related to the movement of ship where the transducer 13 is installed, and determines whether or not the data based on the fish school echo in the tracking area A0 is used for updating the tracking area A0 (SI 08) based on a determination of whether or not the index value (i.e., reverberation contrast) indicating how large the echo intensity (i.e., volume scattering intensity SV) of the entire tracking area AO relative to the echo intensity (i.e., volume scattering intensity SV) around the tracking area AO is equal to or greater than the predetermined threshold value (i.e., reverberation threshold) (SI06, SI07).

[0203] Under a situation where the index value (i.e., reverberation contrast) is small and the degree of distribution of the reverberation echo, which is stronger than or equal to fish school echo, over a wide area including the tracking area A0 is high, the fish school echo is confused with the reverberation echo and the fish school echo is difficult to be distinguished from the reverberation echo. Under such a situation, when the tracking area A0 is updated (S108, SI 10) using the data (i.e., volume scattering intensity SV) based on the fish school echo, the tracking area A0 after the update is greatly affected by the reverberation echo, and the tracking area A0 is difficult to be updated properly. On the other hand, according to the above configuration, it is possible to avoid using fish school echo data (i.e., volume scattering intensity SV) for updating the tracking area A0 under such a situation. Therefore, the tracking area A0 may be properly updated.

[0204] As shown in FIG. 7, when the index value (i.e., reverberation contrast) is equal to or greater than the threshold value (i.e., reverberation threshold) (S107: YES), the control unit 11 (i.e., fish school tracking module 1 lb) updates the tracking area A0 based on the data (i.e., volume scattering intensity SV) based on the fish school echo and the navigation data (SI08, SI 10), and when the index value (i.e., reverberation contrast) is less than the threshold value (i.e., reverberation threshold), updates the tracking area A0 based on the navigation data without using the data (i.e., volume scattering intensity SV) based on the fish school echo (SI 10).

[0205] According to this configuration, when the index value (i.e., reverberation contrast) is equal to or greater than the predetermined threshold value (i.e., reverberation threshold), that is, when the influence 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 may be properly updated. On the other hand, when the index value (i.e., reverberation contrast) is less than the predetermined threshold value (i.e., reverberation threshold), that is, when the influence of the reverberation echo on the fish school echo in the tracking area A0 is large, the tracking area A0 is updated based on the navigation data without using the data based on the fish school echo (i.e., volume scattering intensity SV). Therefore, until the influence of the reverberation echo decreases, the tracking area A0 including the fish school to be tracked may be smoothly set based on the navigation data.

[0206] As shown in FIGS. 7 and 10, the control unit 11 (i.e., fish school tracking module 11b) calculates, as the index value, the reverberation contrast indicating the degree to which the reverberation echo having the same or stronger echo intensity as the echo intensity in the tracking area AO is distributed over a wide range including the tracking area AO (SI05), and determines, based on the reverberation contrast, by a reverberation contrast test (SI06, SI07).

[0207] According to this configuration, the influence of the reverberation echo on the fish school echo may be evaluated by the reverberation contrast, and based on this evaluation, whether or not the data based on the fish school echo should be used for updating the tracking area A0 may be determined.

[0208] As shown in FIG. 10, the reverberation contrast is calculated by the first average value of the data (i.e., volume scattering intensity SV) in the tracking area A0 and the second average value of the data (i.e., volume scattering intensity SV) in the reference area RI to R4 around the tracking area A0.

[0209] Thus, the echo intensity of the entire tracking area A0 may be obtained by the first average value, and the echo intensity around the tracking area A0 may be obtained by the second average value.

[0210] Here, the reverberation contrast is calculated by dividing the first average value by the second average value.

[0211] Thus, it is possible to appropriately evaluate whether or not the reverberation echo, which is as strong as or stronger than the fish school echo, is distributed over a wide range including the tracking area A0 by the reverberation contrast.

[0212] As described above, the reverberation contrast is calculated so as to become smaller as the degree of distribution of the reverberation echo, which is as strong as or stronger than the fish school echo, over a wide range including the tracking area A0 increases.

[0213] Then, the control unit 11 (i.e., fish school tracking module 1 lb) sets reverberation threshold to be compared with the reverberation contrast, and in the process of FIG. 7, when the reverberation contrast is equal to or greater than the reverberation threshold (SI07: YES), the tracking area A0 to be applied at the next transmission timing (i.e., next ping) is set based on the data (i.e., volume scattering intensity SV) based on the fish school echo and the navigation data (SI08, SI 10), and when the reverberation contrast is less than the reverberation threshold (SI07: NO), the tracking area A0 to be applied at the next transmission timing (i.e., next ping) is set based on the navigation data (SI 10) without using the data of fish school echo.

[0214] According to this configuration, when the reverberation contrast is equal to or greater than the reverberation threshold, that is, when the degree of distribution of the reverberation echo, which is equal to or greater than the fish school echo, over a wide range including the tracking area A0 is low, the tracking area A0 to be applied at the next transmission timing is set based on the data based on fish school echo and the navigation data. Therefore, the tracking area AO to properly track the fish school echo may be set based on the amplitude data. On the other hand, when the reverberation contrast is less than the reverberation threshold, that is, when the reverberation echo which is stronger than or equal to the fish school echo is highly distributed over a wide range including the tracking area AO, then the tracking area AO to be applied to the next transmission timing is set based on the navigation data without using the data based on fish school echo. Therefore, the tracking area AO after the update may be avoided to be greatly affected by the reverberation echo, and the tracking area AO to track the fish school echo may be set smoothly based on the navigation data until the influence of reverberation echo decreases.

[0215] As shown in FIGS. 7 and 8, the control unit 11 (i.e., fish school tracking module 11b) estimates the fish school area Al, which is area of the fish school echo, based on the data (i.e., volumetric scattering intensity SV) in the tracking area AO (S103), and if the index value (i.e., reverberation contrast) is equal to or greater than the threshold value (i.e., reverberation threshold) (SI07: YES), the fish school area Al is enlarged by the predetermined magnification to constitute a new tracking area (SI08), the new tracking area is corrected to a position with reference to the origin at the next transmission timing (i.e., next ping) based on the navigation data (SI 10), and sets the tracking area A0 to be applied at the next transmission timing, and if the index value (i.e., reverberation contrast) is less than the threshold value (i.e., reverberation threshold) (S107: NO), the current tracking area A0 is corrected to a position with reference to the origin at the next transmission timing based on the navigation data (SI 10), and sets the tracking area A0 to be applied at the next transmission timing.

[0216] According to this configuration, according to the movement of the ship S1, the tracking area A0 is corrected to the position with the origin as a reference after the movement. Therefore, the tracking area A0 may be properly applied at each transmission timing. Modification Example 1

[0217] The magnification applied in step SI08 of FIG. 7 does not necessarily have to be a fixed value. For example, the magnification may be set so that the magnification increases as the reverberation contrast increases. In other words, the magnification used for enlarging fish school area Al may be changed so that the magnification increases as the reverberation contrast (i.e., index value) increases.

[0218] FIG. 21 is a graph showing an example of a method for setting the magnification when the fish school area Al is enlarged to constitute a new tracking area A0 in step S108 of FIG. 7, according to modification example 1 and according to the embodiment 1 of the present invention.

[0219] In this setting method, a constant magnification is set in the range of reverberation contrast from the reverberation threshold to the value Cl, and the constant magnification larger than the constant magnification of the range up to the Cl is set in the range of reverberation contrast greater than the value C2 on which the reverberation contrast is greater than the value Cl. In addition, the magnification setting method is set so that the range between the values Cl and C2 increases linearly in accordance with the increase in the reverberation contrast.

[0220] By setting the magnification in this way, under a situation where the degree of distribution of the reverberation echo, which is as strong as or stronger than the fish school echo, over a wide area including the tracking area A0 is relatively high, the excessive expansion of the new tracking area A0 relative to the fish school area Al is suppressed, and under the situation where the degree of distribution of the reverberation echo, which is as strong as or stronger than the fish school echo, over a wide area including the tracking area A0 is low, the expansion of the new tracking area A0 relative to fish school area Al is promoted. Therefore, the width of the new tracking area A0 may be appropriately adjusted according to the distribution of the reverberation echo.

[0221] Note that the method of setting the magnification is not limited to this. For example, in the range where the reverberation contrast is greater than the value Cl, the magnification may be set so as to increase linearly with an increase in the reverberation contrast. Alternatively, the magnification may be set so as to increase linearly in accordance with an increase in the reverberation contrast from the reverberation threshold. In addition, the magnification which increases with an increase in the reverberation contrast need not change linearly, for example, it may gradually increase along a predetermined curve. Modification Example 2

[0222] FIG. 22 is a flowchart showing fish school tracking processing, according to modification example 2 and according to the embodiment 1 of the present invention

[0223] In the flowchart of FIG. 22, steps SI 11 to SI 13 are added compared with the flowchart of FIG. 7. The processing in the other steps of FIG. 22 is the same as the processing in the corresponding steps of FIG. 7. The processing in steps SllltoS113is performed by the control unit 11 according to the function of the fish school tracking module 1 lb.

[0224] In step Sill, based on the amplitude data in the tracking area A0 and the amplitude data in the reference area R1-R4 of FIG. 10, the control unit 11 calculates the fish school contrast indicating certainty (i.e., degree) in which fish school echo distinguishable from the reverberation echo is included in the tracking area A0. More specifically, the control unit 11 calculates average value SVao max for the volume scattering intensity SV in the range of several percent (e.g., 5%) from the largest volume scattering intensity SV among the volume scattering intensity SVs included in the tracking area AO, and further calculates the median values SVci to SVC4 of the volume scattering intensity SV for each of the reference area R1-R4. Then, the control unit 11 calculates the value obtained by dividing average value SVao max by the maximum value among the median values SVci to SVC4 as the fish school contrast.

[0225] The average value SVao max obtained from the tracking area AO corresponds to the echo intensity of the core of fish school echo in the tracking area AO. The higher the echo intensity of the core portion is than that of the surrounding reference area R1-R4, the more clearly the fish school in the tracking area AO is demarcated, and the higher certainty in which the fish school echo is included in the tracking area AO. Therefore, by calculating the fish school contrast as described above, the larger fish school contrast, the higher certainty in which the fish school echo is included in the tracking area AO.

[0226] In addition, by using average value of the volume scattering intensity SV in the range from the largest to several percent (for example, 5%) as average value SVao max, the representative value of the fish school echo may be properly evaluated regardless of area width of the tracking area A0. If average value SVao max is average value of all the volume scattering intensity SV in the tracking area A0, the presence of fish school echo is hardly reflected in the value of average value under the situation where weak reverberation echo (i.e., sea surface reflection) is distributed throughout the wide tracking area A0 and strong fish school echo exists in a part of narrow area. Note that the several percent here are not limited to 5%, and may be changed to other appropriate value as long as the above evaluation may be properly performed.

[0227] In addition, by using the median value of the volume scattering intensity SV rather than average value for the reference area RI to R4, the representative value of the reverberation echo (i.e., sea surface reflection) may be properly evaluated even if a relatively small fish school echo other than the tracking object exists in the reference area RI to R4.

[0228] The control unit 11 executes a fish school contrast test using the fish school contrast calculated in step Sill (SI 12). Specifically, the control unit 11 determines whether or not the fish school contrast is equal to or greater than a predetermined fish school threshold.

[0229] If the fish school contrast is equal to or greater than the fish school threshold (SI 13: YES), the control unit 11 advances the process to step SI 05. On the other hand, if the fish school contrast is less than the fish school threshold (SI 13: NO), the control unit 11 skips steps S105 to S108 and advances the process to step SI09.

[0230] Here, the fish school threshold is threshold value for evaluating the accuracy of the fish quantity index calculated from the amplitude data in the fish school area Al in step SI04. That is, the fish school threshold defines a boundary between whether or not the fish quantity index has accuracy suitable for display. The fish school threshold may be set based on actual measurements.

[0231] Here, the acceptance criterion of step SI 13 is lower than the acceptance criterion of step SI 07. That is, even if the judgment in step SI 07 fails, there may be a case where the judgment in step SI 13 passes, but if the judgment in step SI 13 fails, the judgment in step S107 usually fails. Therefore, if the judgment in step SI 13 is NO, the processing proceeds to step S109 without performing the processing of steps S105 to S108.

[0232] If the judgment in the fish school contrast test passes in step SI 13, the control unit 11 (i.e., image generation module lid) associates fish quantity index acquired in the current ping with the center point Cl 1 offish school area Al in the current ping and stores it in the storage unit 12 in step S22 of FIG. 13. On the other hand, if the judgment in the fish school contrast test fails in step SI 13, the control unit 11 (i.e., image generation module lid) associates, in place of the fish quantity index acquired in the current ping, the fish quantity index in the previous ping with the center point Cl 1 of the fish school area Al in the current ping and stores it in the storage unit 12 in step S22 of FIG. 13. Thus, it is possible to suppress the display of fish quantity information based on the fish quantity index with low accuracy.

[0233] In this case, the control unit 11 may add a predetermined warning display to the display of the fish quantity information based on the corresponding fish quantity index when fish school contrast test fails continuously a predetermined number of times (For example, set from a few to a dozen times) including the failure of the current ping. Effect of Modification Example 2

[0234] As shown in FIG. 22, the control unit 11 (i.e., fish school tracking module 1 lb) calculates, based on the data (i.e., volumetric scattering intensity SV) in the tracking area A0 and the data (i.e., volumetric scattering intensity SV) in the reference area RI to R4 around the tracking area A0, the fish school contrast indicating certainty including fish school echo in the tracking area A0 (Sill), and if the fish school contrast is equal to or greater than the predetermined fish school threshold (SI 13: YES), executes the updating process (S105 to S108) of the tracking area A0 based on the index value (i.e., reverberation contrast), and if the fish school contrast is less than the fish school threshold (SI 13: NO), sets the tracking area A0 to be applied at the next transmission timing based on the navigation data (SI 10) without executing the updating process of the tracking area A0 based on the index value (i.e., reverberation contrast) (S105 to S108).

[0235] According to this configuration, when the fish school contrast is less than the fish school threshold, that is, when the degree of distribution of the reverberation echo, which is as strong as or stronger than the fish school echo, over a wide range including the tracking area A0 is considerably high, the update processing of the tracking area AO based on the index value (i.e., reverberation contrast) is omitted, and the tracking area AO to be applied to the next transmission timing is set from the navigation data. Thus, the update of the tracking area AO may be properly performed while simplifying the processing.

[0236] As described above, the control unit 11 (i.e., fish school tracking module 11b) may be configured to calculate the fish school contrast based on the maximum value of the data (i.e., volumetric scattering intensity SV) in the tracking area AO and the median value of the data surrounding the tracking area AO.

[0237] According to this configuration, the fish school contrast indicating certainty including the fish school echo distinguishable from the reverberation echo in the tracking area A0 may be properly calculated. Embodiment 2

[0238] In the embodiment 1, the underwater detection device 10 displays the display image 100 including the fish quantity information, but in the embodiment 2, a plotter device 30 displays the display image 100 including the fish quantity information.

[0239] FIG. 23 is a diagram showing the configuration of a fish quantity information display device 1, according to the embodiment 2 of the present invention.

[0240] The fish quantity information display device 1 includes the underwater detection device 10 and the plotter device 30. The underwater detection device 10 does not have the function for displaying the display image 100 described above, and this function has been transferred to the plotter device 30. The configuration and functions of the plotter device 30 are the same as those of the well-known marine plotter device except for the configuration and functions for displaying the fish quantity information.

[0241] The underwater detection device 10 acquires the center point Cll of the fish school calculated by the fish school tracking module 1 lb and the fish quantity index calculated by the fish quantity index calculation module 11c for each ping by the process shown in FIG. 7, and transmits the acquired information to the plotter device 30 for each ping. The plotter device 30 executes the process shown in FIG. 13 using the center point Cll and the fish quantity index value received for each ping to generate the display image 100 in which the swimming path 120 and fish quantity information are superimposed on a plotter image. That is, the plotter device 30 has the function of generating the plotter image and the function of the image generation module lid shown in FIG. 3. Step S21 of FIG. 13 is changed to the process of receiving the center point Cl 1 of the fish school and the fish quantity index from the underwater detection device 10 for each ping.

[0242] The plotter device 30 obtains the position of own ship through a Global Positioning System (GPS) antenna 30a. That is, the plotter device 30 receives the radio wave transmitted from the GPS satellite through the GPS antenna 30a to obtain the position of own ship on the earth. The plotter device 30 uses the position of own ship thus obtained in step 23 of FIG. 13.

[0243] FIG. 24 is a diagram showing the configuration of a display image 200 displayed on the plotter device 30, according to the embodiment 2 of the present invention.

[0244] The display image 200 includes a land image 210 corresponding to the land and a sea image 220 corresponding to the sea area. Although the land image 210 and the sea image 220 are displayed in different colors, the land image 210 is hatched here to distinguish the land image 210 and the sea image 220. The sea image 220 includes an isobath line 221 indicated by a dashed line and a water depth indication 222 appended to the isobath line 221.

[0245] In the display image 200, the same image as in FIG. 15 is superimposed on the land image 210 and the sea image 220. In the example of FIG. 24, according to another display method 2 of FIG. 17, the display image 200 includes the cruising path 110 of own ship, the plot 111 showing present position of own ship 111, the swimming path 120 of fish school, the arrow 130 showing the movement state of fish school 130, and the fish quantity image 141-143. Here, as in FIG. 17, the transparency of the fish quantity image 141-143 increases with the passage of time. The display method of the fish quantity image 141-143 may be replaced by any of the display methods of FIG. 15, FIG. 16, and FIGS. 18 to 20. The same effect as in Embodiment 1 may be achieved by Embodiment 2. Embodiment 3

[0246] FIG. 25 is a diagram showing the configuration of the fish quantity information display device 1, according to the embodiment 3 of the present invention.

[0247] As shown in FIG. 25, the fish quantity information display device 1 according to Embodiment 3 includes a radar device 50 compared with the configuration shown in FIG. 23. The radar device 50 includes a radar antenna 50a, and transmits a transmission wave (i.e., microwave) from the radar antenna 50a around own ship (i.e., in the air). The radar device 50 uses the radar antenna 50a to receive the reflected wave of the transmitted transmission wave, and detects target (i.e., ship, land, birds, etc.) existing around own ship.

[0248] The radar antenna 50a is installed, for example, on the top surface of the wheelhouse and rotates in the horizontal direction. The traveling direction of the transmission wave traveling straight from the radar antenna 50a in the horizontal direction rotates with the turning of the radar antenna 50a. By receiving the reflected wave at each turning position (i.e., bearing), the presence or absence of target at each turning position (i.e., bearing), the distance to target, and the intensity (i.e., echo intensity) of the reflected wave from target are detected. The radar device 50 is a radar device of well- known configuration used for ships. The radar device 50 successively transmits the distance to target and the echo intensity at each bearing to the plotter device 30.

[0249] The plotter device 30 superimposes the display of the present target on the display image 200 based on the azimuth, the distance to target, and the echo intensity received from the radar device 50.

[0250] FIG. 26 is a diagram showing the configuration of the display image 200 displayed on the plotter device 30, according to the embodiment 3 of the present invention

[0251] The display image 200 of FIG. 26 includes a target image 235 based on information from the radar device 50 in comparison with the display image 200 of FIG. 24. Here, two target images 235 correspond to other ship. From these target images 235, the user may understand that other ship is currently in the vicinity of own ship. Thus, the user may judge whether or not it is possible to advance to the moving position of the fish school without interference with other ship, and the capture of fish school may proceed smoothly. Other Modification Example

[0252] In Embodiment 1, the volume scattering intensity SV obtained from the amplitude data was used for the processing in FIGS. 7 and 22, but other data derived from the amplitude data may be used for the fish school tracking processing. For example, if the width in the distance direction of the tracking area A0 is smaller than the distance from the transducer 13 to the tracking area A0, then the attenuation degree of sound waves due to spherical divergence and absorption is almost constant in the tracking area A0, and therefore the amplitude data itself may be used for the processing in FIGS. 7 and 22.

[0253] In embodiment 1, the value obtained by dividing average value (i.e., first average value) of the data (i.e., volume scattering intensity SV) included in the tracking area A0 by average value (i.e., second average value) obtained from the data (i.e., volume scattering intensity SV) of the reference area RI to R4 is calculated as reverberation contrast, but the value obtained by dividing the second average value by the first average value may be calculated as the reverberation contrast. In this case, the determination in step SI07 of FIG. 7 is YES when the reverberation contrast is equal to or less than the reverberation threshold, and NO when the reverberation contrast is greater than the reverberation threshold.

[0254] In the above-described Embodiment 1, the data generation module 1 la generated amplitude data, but the data generation module Ila may further generate the volume scattering intensity SV based on the amplitude data.

[0255] The magnification shown on the vertical axis in FIG. 21 is an example, and other magnifications may be assigned.

[0256] Moreover, the processing of detecting and tracking the fish school is not limited to the processing shown in the above-described Embodiment 1, and other well-known methods may be used. However, by using the method described in the above-described Embodiment 1, the echo of fish school may be stably tracked even under conditions where the reverberation echo affects such as sea 5 surface reflection.

[0257] In the above-described embodiment 1, the fish quantity index calculation module 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 functions 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 consist of a 10 field-programmable gate array (FPGA) or hardware with integrated logic circuits.

[0258] The configuration of the underwater detection device 10 is not limited to the configuration shown in the above-described embodiment 1—3, but may be any other configuration as long as it forms the plurality of reception beams in the scanning range and generates data on the echo intensity at each position in the scanning range. 15

[0259] In addition, the embodiment of the present invention may be modified as appropriate within the scope of claims. Reference Signs List 1 Fish quantity information display device 10 Underwater detection device 11 Control unit 1 la Data generation module 1 lb Fish school tracking module 11c Fish quantity index calculation module lid Image generation module 12 Storage unit 13 Transducer 13a Plurality of ultrasonic oscillators / ultrasonic oscillator / number of ultrasonic oscillators 14 Transmission processing module 15 Reception processing module 16 Transmission / reception switching unit 17 Display unit 18 Display processing module 19 Input unit 20 Input processing module 30 Plotter device 30a GPS antenna 50 Radar device 50a Radar antenna 100, 200 Display image 110 Cruising path 111 Plot 120 Swimming path 130 Arrow 141-143 and 144- 146 Fish quantity image 147 Value 210 Land image 220 Sea image 221 Isobath line 222 Water depth indication 235 Target image SI Ship SP1 Scanning plane TB1 Transmission beam RB1 Reception beam Q Fish quantity index Al Fish school area All, Al2 Area PIO Echo image Pl 1 Image P12 Track P13 Straight line P14, P15, andP16 Circular boundary lines P17 Hatched area AO Tracking area W01, W02, W11, W12 Width C01, Cll Center point V01 and V02 Outer vertical lines HOI and H02 Outer horizontal lines VI1 and V12 Inner vertical lines Hl 1 and Hl2 Inner horizontal lines RI to R4 Reference area Pl and P2 Points

Claims

1. A fish quantity information display device (1), comprising:a transmission processing module (14) configured to cause a plurality of ultrasonic oscillators (13a) included in a transducer (13) installed on a bottom of a ship (SI) to transmit ultrasonic waves at transmission timing at predetermined intervals;a data generation module (Ila) configured to form a plurality of reception beams (RBI) in a scanning range based on electric signal output from the plurality of ultrasonic oscillator (13 a) in a reception period after the transmission timing, and generate data related to an echo intensity at each position of the scanning range;a fish school tracking module (1 lb) configured to track fish school based on the data;a fish quantity index calculation module (11c) configured to calculate a fish quantity index of the fish school based on the data; andan image generation module (lid) configured to generate a display image in which fish quantity information based on the fish quantity index is related to a swimming path (120) of the fish school based on tracking of the fish school and the fish quantity index.

2. The fish quantity information display device (1) according to claim 1, whereinthe fish school tracking module (1 lb) calculates a movement state of the fish school based on tracking result of the fish school, andthe image generation module (lid) further relates the movement state of the fish school to the swimming path (120).

3. The fish quantity information display device (1) according to claim 1, whereinthe fish quantity information includes a fish quantity image corresponding to a value of the fish quantity index, andthe image generation module (lid) relates the fish quantity image to a predetermined position on the swimming path (120).

4. The fish quantity information display device (1) according to claim 3, whereinthe fish quantity image is a circle composed of at least one of a diameter and a color corresponding to the value of the fish quantity index.

5. The fish quantity information display device (1) according to claim 3, whereinthe fish quantity image is a band composed of at least one of a width and a color corresponding to the value of the fish quantity index.

6. The fish quantity information display device (1) according to claim 3, wherein a transparency of the fish quantity image is adjusted so as to increase over time.

7. The fish quantity information display device (1) according to claim 1, wherein the fish quantity information includes a value of the fish quantity index, and the image generation module (lid) relates the value of the fish quantity index to a predetermined position on the swimming path (120).

8. The fish quantity information display device (1) according to claim 1, wherein: the image generation module (lid) displays the fish quantity information when a value of the fish quantity index is equal to or greater than a predetermined threshold value.

9. The fish quantity information display device (1) according to any one of claims 1 to 8, wherein the fish school tracking module (1 lb) updates a tracking area (AO) for tracking the fish school based on the data and navigation data related to a movement of the ship (SI) in which the transducer (13) is installed, anddecides whether or not to use the data based on fish school echo in the tracking area (AO) for updating the tracking area (AO) based on a determination whether or not an index value indicating how high the echo intensity of the whole tracking area (AO) is relative to the echo intensity around the tracking area (AO) is equal to or greater than a predetermined threshold value.

10. The fish quantity information display device (1) according to claim 9, wherein the fish school tracking module (1 lb) when the index value is equal to or greater than the threshold value, updates the tracking area (A0) based on the data based on the fish school echo and the navigation data, andwhen the index value is less than the threshold value, updates the tracking area (A0) based on the navigation data without using the data based on the fish school echo.

11. The fish quantity information display device (1) according to claim 9, whereinthe fish school tracking module (1 lb) calculates, as the index value, a reverberation contrast indicating a degree to which a reverberation echo having the echo intensity equal to or higherthan the echo intensity in the tracking area (AO) is distributed over a wide range including the tracking area (AO), and the determination is made based on the reverberation contrast.

12. The fish quantity information display device (1) according to claim 11, whereinthe reverberation contrast is calculated by a first average value of the data in the tracking area (AO) and a second average value of the data around the tracking area (AO).

13. The fish quantity information display device (1) according to claim 12, whereinthe reverberation contrast is calculated by dividing the first average value by the second average value.

14. The fish quantity information display device (1) according to claim 11, whereinthe reverberation contrast is calculated so as to become smaller as the degree of the distribution increases.

15. The fish quantity information display device (1) according to claim 14,wherein the fish school tracking module (1 lb) sets a reverberation threshold to be compared with the reverberation contrast as the threshold value,when the reverberation contrast is greater than the reverberation threshold, sets the tracking area (AO) to be applied at the next transmission timing based on the data based on the fish school echo and the navigation data, andwhen the reverberation contrast is less than the reverberation threshold, sets the tracking area (AO) to be applied at the next transmission timing based on the navigation data without using the data based on the fish school echo.

16. The fish quantity information display device (1) according to claim 9,wherein the fish school tracking module (1 lb) estimates a fish school area (Al) which is area of the fish school echo based on the data in the tracking area (AO),when the index value is equal to or greater than the threshold value, enlarges the fish school area (Al) by a predetermined magnification to constitute a new tracking area, corrects the new tracking area to a position based on a position of the transducer (13) at the next transmission timing based on the navigation data, and sets to the tracking area to be applied at the next transmission timing, andwhen the index value is less than the threshold value, corrects the current tracking area to a position based on a position of the transducer (13) at the next transmission timing based on the navigation data, and sets to the tracking area to be applied at the next transmission timing.

17. The fish quantity information display device (1) according to claim 16, whereinthe fish school tracking module (1 lb) changes the magnification used for enlarging the fish school area (Al) so that the magnification increases as the index value increases.

18. The fish quantity information display device (1) according to claim 9, whereinthe fish school tracking module (11b) calculates a fish school contrast indicating certainty including the fish school echo in the tracking area (AO) based on the data in the tracking area and the data around the tracking area (AO),the image generation module (lid)when the fish school contrast is equal to or greater than a predetermined fish school threshold, associates fish quantity information based on fish quantity index acquired this time with the swimming path (120) of the fish school, andwhen the fish school contrast is less than the fish school threshold, associates fish quantity information based on, instead of fish quantity index acquired this time, fish quantity index acquired previous time with the swimming path (120) of the fish school.

19. The fish quantity information display device (1) according to claim 18, whereinthe fish school tracking module (1 lb) calculates the fish school contrast based on a maximum value of the data in the tracking area (A0) and a median value of the data around the tracking area.

20. The fish quantity information display device (1) according to claim 1, further comprising:a radar device (50) configured to detect a surrounding target by receiving a reflected wave of a transmission wave transmitted in the air; whereinthe image generation module (lid) includes, in the display image, target existing in a vicinity of the swimming path (120), based on a detection result of the radar device (50).

21. A fish quantity information display method, comprising:transmitting, by a transmission processing module (14), ultrasonic waves to a plurality of ultrasonic oscillators (13a) included in a transducer (13) installed on a bottom of a ship (SI) at transmission timings at predetermined intervals;forming, by a data generation module (Ila), a plurality of reception beams (RBI) in a 5 scanning range based on electric signal output from the plurality of ultrasonic oscillator (13 a) in reception period after transmission timing, and generating data on echo intensity at each position of the scanning range;tracking, by a fish school tracking module (1 lb), fish school based on the data;calculating, by a fish quantity index calculation module (11c), a fish quantity index of the 10 fish school based on the data; andgenerating, by an image generation module (lid), a display image in which fish quantity information based on the fish quantity index is related to a swimming path (120) of the fish school based on the tracking of fish school and the fish quantity index.T +44(0)30 0300 2000A

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