GB2576821A

GB2576821A - Echo signal processing device, echo signal processing system, and echo signal processing method

Info

Publication number: GB2576821A
Application number: GB1910086.6A
Authority: GB
Inventors: Hayashi Koji; Hazama Takuto
Original assignee: Furuno Electric Co Ltd
Current assignee: Furuno Electric Co Ltd
Priority date: 2018-07-31
Filing date: 2019-07-15
Publication date: 2020-03-04
Anticipated expiration: 2039-07-15
Also published as: JP2020020621A; CN110780286A; GB2576821B; JP7021025B2; GB201910086D0

Abstract

An echo signal processing device to acquire a status of movements of fish comprising a detecting unit, a correspondence unit and an association unit. The detecting unit detects echoes of fish from echo signals generated by a sonar sensor (3). The correspondence relation identifying unit (17) identifies a correspondence relation between a first fish echo detected at a first time and a second fish echo detected at a second time. The correspondence preferably being determined by using the ship location to determine the position of a centre of the fish generating the signal and comparing the centres in the two signals. An association information generating unit (15) generates association information associating the first and the second fish echoes for which the correspondence relation identified (17) with each other. The association information preferably forming a vector indicating the direction of movement of the detected fish.

Description

ECHO SIGNAL PROCESSING DEVICE, ECHO SIGNAL PROCESSING

SYSTEM, AND ECHO SIGNAL PROCESSING METHOD

TECHNICAL FIELD [0001] The present invention relates to an echo signal processing device, an echo signal processing system including an echo signal processing device, and an echo signal processing method for processing an echo signal generated by a sonar sensor based on reflected waves of transmission waves transmitted in the water.

BACKGROUND OF THE INVENTION [0002] For example, in U.S. Patent Application Publication No. 2017/0242113 Al, an echo signal processing device that processes an echo signal generated by a sonar sensor based on reflective waves of transmission waves transmitted in the water is disclosed. U.S. Patent Application Publication No. 2017/0242113 Al discloses a configuration in that an echo of fish detected by an echo signal processing device is displayed on a display unit such as a display together with a map of the vicinity of a ship in which the sonar sensor is mounted based on data generated by the echo signal processing device.

[0003] According to the configuration disclosed in U.S. Patent Application Publication No. 2017/0242113 Al, the echo of fish displayed on the display unit based on data generated by an echo signal processing device is displayed on the screen of the display unit together with the map of the vicinity of the ship. However, only the echo of fish is displayed together with the map, and thus, it is difficult for a user to perceive movements of the fish from looking at only the screen of the display unit. For this reason, in order to perceive the movements of the fish, the user needs to look at the screen of the display unit for a long time. Accordingly, there is a problem that it is difficult for a user to perceive a status of the movements of the fish easily and quickly.

SUMMARY OF THE INVENTION [0004] The present invention is for solving the problem described above, and an objective thereof is to provide an echo signal processing device, an echo signal processing system, and an echo signal processing method capable of allowing a user to perceive a status of movements of fish easily and quickly.

[0005] (1) In order to solve the problems described above, according to a certain aspect of the present invention, an echo signal processing device is provided to include: a fish echo detecting unit that detects echoes of fish from echo signals generated by a sonar sensor based on reflected waves of transmission waves transmitted into the water; a correspondence relation identifying unit that identifies a correspondence relation between a first fish echo that is an echo of the fish detected at a first timing and a second fish echo that is an echo of the fish detected at a second timing before the first timing; and an association information generating unit that generates association information associating the first fish echo and the second fish echo for which a correspondence relation has been identified by the correspondence relation identifying unit with each other.

[0006] (2) The echo signal processing device described above may further include: a display control unit that performs controls of displaying the echoes of the fish and the association information.

[0007] (3) The echo signal processing device described above may further include: a ship position information acquiring unit that acquires ship position information of a ship where the sonar sensor is mounted; a fish centre relative coordinates calculating unit that calculates relative coordinates of centres of the echoes of the fish with reference to the position of the ship based on the echoes of the fish; and a fish centre absolute coordinates calculating unit that calculates absolute coordinates of the centre of the echo of the fish based on the ship position information and the relative coordinates of the centres of the echoes of the fish, in which the association information generating unit may generate the association information based on the absolute coordinates of the centres of the echoes of the fish.

[0008] (4) The correspondence relation identifying unit may associate the first fish echo with the second fish echo when a centre of the fish echo is present within a predetermined distance from a centre of the second fish echo.

[0009] (5) The display control unit may perform controls of displaying the second fish echo and the first fish echo together with the association information.

[0010] (6) The association information generating unit may generate information of vectors connecting the second fish echo and the first fish echo as the association information, and the display control unit may perform controls of displaying the vectors as segment displays.

[0011] (7) The association information generating unit may generate information including numerical values of vectors connecting the second fish echo and the first fish echo as the association information, and the display control unit may perform controls of displaying the information including the numerical values of the vectors.

[0012] (8) The information including numerical values of the vectors may include orientations and speeds of the fish in a horizontal direction and orientations and speeds of the fish in a vertical direction.

[0013] (9) The association information generating unit, in a case that a plurality of the first fish echoes corresponds to the second fish echo, may generate the association information associating the second fish echo with the plurality of the first fish echoes.

[0014] (10) The association information generating unit, in a case that a plurality of the second fish echoes corresponds to the first fish echo, may generate the association information associating the plurality of the second fish echoes with the first fish echo.

[0015] (11) In addition, in order to solve the problems described above, according to a certain aspect of the present invention, an echo signal processing system is provided to include: a sonar sensor that generates echo signals based on reflected waves of transmission waves transmitted into the water; the above-described echo signal processing device that processes the echo signals; and a display unit that displays an image based on data generated by the echo signal processing device.

[0016] (12) Furthermore, in order to solve the problems described above, according to a certain aspect of the present invention, an echo signal processing method is provided to include: detecting echoes of fish from echo signals generated by a sonar sensor based on reflected waves of transmission waves transmitted into the water; identifying a correspondence relation between a first fish echo that is an echo of the fish detected at a first timing and a second fish echo that is an echo of the fish detected at a second timing before the first timing; and generating association information associating the first fish echo and the second fish echo for which a correspondence relation has been identified with each other.

EFFECT(S) OF THE INVENTION [0017] According to the present invention, an echo signal processing device, an echo signal processing system, and an echo signal processing method capable of allowing a user to perceive a status of movements of fish easily and quickly can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS [0018] The present disclosure is illustrated by way of example and not by way of limitation in the figures of the accompanying drawings, in which the like reference numerals indicate like elements and in which:

FIG. 1 is a block diagram illustrating the configuration of an echo signal processing system according to one embodiment of the present invention.

FIG. 2 is a diagram schematically illustrating a transmission space in which transmission waves are transmitted by a transducer of a sonar sensor and reception spaces in which reflected waves are received by the transducer.

FIG. 3 is a block diagram illustrating the configuration of an echo signal processing device according to one embodiment of the present invention.

FIG. 4 is a diagram illustrating a process of a fish echo detecting unit of an echo signal processing device.

FIG. 5 is a diagram illustrating a process of a correspondence relation identifying unit of an echo signal processing device.

FIG. 6 is a diagram illustrating a process of an association information generating unit of an echo signal processing device.

FIG. 7 is a diagram schematically illustrating one example of a video displayed on a display screen of a display unit.

FIG. 8 is a diagram schematically illustrating one example of a video displayed on a display screen of a display unit.

FIG. 9 is a flowchart illustrating operations of an echo signal processing device and an echo signal processing system.

FIG. 10 is a diagram illustrating the first modified example and is a diagram schematically illustrating one example of a video displayed on a display screen of a display unit.

FIG. 11 is a diagram illustrating the second modified example and is a diagram schematically illustrating one example of a video displayed on a display screen of a display unit.

FIG. 12 is a diagram illustrating the third modified example and is a diagram schematically illustrating one example of a video displayed on a display screen of a display unit.

FIG. 13 is a diagram illustrating the fourth modified example and is a diagram schematically illustrating one example of a video displayed on a display screen of a display unit.

FIG. 14 is a diagram illustrating another modified example and is a diagram schematically illustrating one example of a video displayed on a display screen of a display unit.

DETAILED DESCRIPTION OF THE INVENTION [0019] Hereinafter, an echo signal processing system 1 and an echo signal processing device 2 according to one embodiment of the present invention will be described with reference to the drawings.

[Echo signal processing system] [0020] FIG. 1 is a block diagram illustrating the configuration of an echo signal processing system 1 according to one embodiment of the present invention. The echo signal processing system 1 includes an echo signal processing device 2 according to one embodiment of the present invention. The echo signal processing system 1 and the echo signal processing device 2 according to this embodiment, for example, are used for a ship such as a fishing vessel. Hereinafter, a ship in which the echo signal processing system 1 and the echo signal processing device 2 are disposed will be referred to as a “subject ship.” [0021] The echo signal processing system 1 according to the embodiment, as illustrated in FIG. 1, includes an echo signal processing device 2, a sonar sensor 3, and a display unit 4.

[Sonar sensor] [0022] In this embodiment, the sonar sensor 3 is provides as a scanning sonar and is configured as a sensor that transmits transmission waves as ultrasonic waves in the water and generates an echo signal based on reflected waves of the transmission waves transmitted in the water. The sonar sensor 3 includes a transducer 5 and a transceiver 6. [0023] The transducer 5 has a function of transmitting and receiving ultrasonic waves and is attached to the bottom of the subject ship. For example, as one example, the transducer 5 is formed in a substantially cylindrical shape. More specifically, the transducer 5 includes a casing having a substantially cylindrical shape and ultrasonic vibrators (not shown) as a plurality of transducing elements attached to an outer peripheral face of the casing.

[0024] An ultrasonic vibrator transmits ultrasonic waves to a transmission space in the water as transmission waves, receives reflected waves of the transmission waves with respect to a target in the water, generates an echo signal by converting the received reflected waves into an electrical signal, and outputs the generated echo signal to the transceiver 6. As targets in the water at which the transmission waves transmitted from the transducer 5 are reflected, there are fish, seabed topography, and the like.

[0025] FIG. 2 is a diagram schematically illustrating a transmission space TS in which the transmission waves are transmitted by the transducer 5 and a plurality of reception spaces RS in which reflected waves are received by the transducer 5. The transmission waves transmitted from the transducer 5 mounted on the subject ship S are transmitted together from the transducer 5 in all the directions in the water centred on the subject ship S, and, for example, transmission beams having a conic form are formed. In a case in which transmission beams having a conic form are formed, the transmission space TS where the transmission waves are transmitted is configured as a conical space. In addition, the shape of transmission beams is not limited to a conic form, and the transmission beams may be formed in various different shapes in accordance with the shape of the transducer 5 and the amplitude and the phase of an electrical signal input to each transducing element of the transducer 5.

[0026] In addition, the transducer 5 may form a plurality of reception beams scanning in a circumferential direction (in the direction of an azimuth angle Θ denoted by an arrow in FIG. 2) inside the transmission space TS altogether after transmission of transmission beams. In other words, all the beams are formed at one reception timing according to the transducer 5. Reflected waves reflected by a target such as fish in the water are received in a plurality of reception spaces RS (in other words, each space where reception beams are formed) disposed to be aligned in the circumferential direction of the transmission space TS (in other words, in the direction of the azimuth angle Θ).

[0027] The transceiver 6 includes a transmission/reception switching unit 7, a transmission circuit unit 8, and a reception circuit unit 9.

[0028] The transmission/reception switching unit 7 is used for switching between transmission and reception of signals for the transducer 5. More specifically, when a drive signal used for driving the transducer 5 is transmitted to the transducer 5, the transmission/reception switching unit 7 outputs a drive signal output by the transmission circuit unit 8 to the transducer 5. On the other hand, when an echo signal is received from the transducer 5, the transmission/reception switching unit 7 outputs the echo signal received from the transducer 5 to the reception circuit unit 9.

[0029] The transmission circuit unit 8 generates a drive signal that is a base of transmission waves transmitted from the transducer 5. More specifically, the transmission circuit unit 8 includes a transmission circuit (not illustrated in the drawing) disposed in correspondence with each ultrasonic vibrator, and each transmission circuit generates a drive signal.

[0030] The reception circuit unit 9 is configured to include a reception circuit (not shown) that is disposed in correspondence with each ultrasonic vibrator and processes an echo signal generated from the reflected waves received. Then, the reception circuit unit 9 amplifies an echo signal serving as an electrical signal that is generated from the reflected waves and output by the transducer 5, and eliminates unnecessary frequency components by limiting the bandwidth of the reception circuit unit 9. In addition, the reception circuit unit 9 converts the amplified echo signal into an echo signal as a digital signal and outputs the converted echo signal to the echo signal processing device 2.

[Display unit] [0031] The display unit 4 is configured as a display device such as a display. The display unit 4 displays a video on a display screen based on data (more specifically, display video data to be described later) that is generated by the echo signal processing device 2 and is output from the echo signal processing device 2. The display unit 4, for example, displays an undersea state below the subject ship S as a three-dimensional bird’s eye view. Accordingly, a user of the echo signal processing system 1 can estimate presence/absence and the position of fish below the subject ship S by looking at the display screen.

[overall configuration of echo signal processing device] [0032] FIG. 3 is a block diagram illustrating the configuration of the echo signal processing device 2. Referring to FIGs. 1 and 3, the echo signal processing device 2 performs processes of controls of processing an echo signal output from the reception circuit unit 9 to detect an echo of fish, and generating information associating the echoes of the fish detected at different timings to display the echoes of the fish on the display unit 5 together with the information.

[0033] The echo signal processing device 2 includes a subject ship position information acquiring unit 11, a fish echo detecting unit 12, a fish centre relative coordinates calculating unit 13, a fish centre absolute coordinates calculating unit 14, a correspondence relation identifying unit 17, an association information generating unit 15, a display control unit 16, and the like.

[0034] The echo signal processing device 2 is a device connected to the transceiver 6 of the sonar sensor 3 using a cable or the like and, for example, is configured as a personal computer (PC) as one example. The echo signal processing device 2 includes a hardware processor 10 (for example, a CPU, an FPGA, or the like) and devices such as a non-volatile memory and the like. The hardware processor 10 functions as the subject ship position information acquiring unit 11, the fish echo detecting unit 12, the fish centre relative coordinates calculating unit 13, the fish centre absolute coordinates calculating unit 14, the association information generating unit 15, and the display control unit 16 to be described in detail below. For example, when a CPU reads a program from a non-volatile memory and executes the program, the hardware processor 10 functions as the subject ship position information acquiring unit 11, the fish echo detecting unit 12, the fish centre relative coordinates calculating unit 13, the fish centre absolute coordinates calculating unit 14, the association information generating unit 15, and the display control unit 16.

[Subject ship position information acquiring unit] [0035] The subject ship position information acquiring unit 11 is configured to acquire subject ship position information that is information of a position of the subject ship S in which the sonar sensor 3 is mounted. In addition, in the subject ship S, a GPS antenna (not shown) that receives electromagnetic waves transmitted from positioning satellites and a GPS receiver (not shown) that detects the position of the subject ship S based on positioning signals received from the GPS antenna are mounted. The GPS receiver is connected to the echo signal processing device 2 and is configured to output a detected position of the subject ship S to the echo signal processing device 2. A detection result acquired by the GPS receiver is input to the echo signal processing device 2, and therefore the subject ship position information acquiring unit 11 acquires subject ship position information.

[0036] In addition, the subject ship position information acquiring unit 11 is configured to also acquire information of an azimuth of the subject ship S, in other words, information of the direction of a bow of the subject ship S. Furthermore, in the subject ship S, a gyrocompass (not shown) or a satellite compass (not shown) that detects the azimuth of the subject ship S as an absolute azimuth is mounted. In addition, the satellite compass, for example, is configured to include two GPS antennas mounted in the subject ship S, receive radio waves transmitted from the positioning satellites using two GPS antennas, measure a relative position between the two GPS antennas based on carrier phases of the received radio wave signals, and detect the azimuth of the subject ship S as an absolute azimuth. The gyrocompass or the satellite compass mounted in the subject ship S is connected to the echo signal processing device 2 and is configured to output the detected azimuth of the subject ship S to the echo signal processing device 2. A detection result acquired by the gyrocompass or the satellite compass is input to the echo signal processing device 2, and therefore the subject ship position information acquiring unit 11 acquires information of the azimuth of the subject ship S.

[Fish echo detecting unit] [0037] The fish echo detecting unit 12 is configured to detect echoes of fish from an echo signal generated by the sonar sensor 3 based on the reflected waves of the transmission waves transmitted in the water. FIG. 4 is a diagram illustrating a process of the fish echo detecting unit 12. FIG. 4 schematically illustrates a state in which echoes El and E2 of fish are detected in a detection area DR that is an area where fish are detected, and an echo of the fish is detected and is an area corresponding to a transmission space TS in which transmission waves are transmitted.

[0038] The fish echo detecting unit 12 is configured to perform a beam forming process (more specifically, phase adding) first for each of a plurality of reception spaces RS based on an echo signal received from the reception circuit unit 9 and perform a filter process. In addition, in the beam forming process, the fish echo detecting unit 12 generates a reception beam signal that is equivalent to a signal acquired by a single ultrasonic vibrator having narrow directivity in a specific direction. Then, by repeatedly performing this process while changing a combination of ultrasonic vibrators that are targets for the beaming forming process, the fish echo detecting unit 12 generates many reception beam signals having directivity for each azimuth corresponding to each reception space RS. In addition, the fish echo detecting unit 12 performs a filter process of a band limiting filter, a pulse compression filter, or the like for each reception beam formed in correspondence with each reception space RS. In accordance with such a process, the fish echo detecting unit 12 generates an echo signal for which the beam forming process and the filter process have been performed.

[0039] Then, the fish echo detecting unit 12 detects echoes present above the seabed as echoes of fish based on echo signals for which the beam forming process and the filter process have been performed, the subject ship position information acquired by the subject ship position information acquiring unit 11, and the seabed information including depth information of the seabed. In other words, in a detection area DR centred on the position of the subject ship identified using the subject ship position information, an echo present above the depth of the seabed identified by the seabed information is detected as the echoes of the fish. The seabed information, for example, is acquired from a sea map (chart) stored in a storage medium connected to the echo signal processing device 2. In addition, a sea map of a sea area in which the subject ship S sails may be stored in the echo signal processing device 2 in advance, and the seabed information may be acquired from the stored sea map. Furthermore, there may be a configuration such that a depth measuring instrument measuring a depth of the seabed is mounted in the subject ship S, the echo signal processing device 2 and the depth measuring instrument are connected to each other, and the seabed information is acquired by inputting a result of the measurement acquired by the depth measuring instrument to the echo signal processing device 2. In addition, the depth measuring instrument, for example, may be configured by a fish finder.

[Fish centre relative coordinates calculating unit] [0040] The fish centre relative coordinates calculating unit 13 calculates relative coordinates of the centre of an echo of fish with reference to the position of the subject ship S based on echoes El and E2 of fish detected by the fish echo detecting unit 12. The fish centre relative coordinates calculating unit 13 calculates the relative coordinates of the centre of the echo of each school of fish as three-dimensional coordinates for each of the echoes El and E2 of fish. In other words, in the example illustrated in FIG. 4, the fish centre relative coordinates calculating unit 13 calculates relative coordinates of the position of the centre of the echo El of the fish with respect to the subject ship S and relative coordinates of the position of the centre of the echo E2 of the fish with respect to the subject ship S as three-dimensional coordinates.

[0041] In addition, an arrival azimuth and an arrival distance of a reflected wave corresponding to each of the echoes El and E2 of fish are identified by the fish echo detecting unit 12 as three-dimensional coordinates of a curved coordinates system for each of the echoes El and E2 of the fish. Based on these, the fish centre relative coordinates calculating unit 13 calculates relative coordinates of the centre of each of the echoes El and E2 of the fish with reference to the position of the subject ship S as three-dimensional coordinates of an orthogonal coordinates system. In addition, the position of the centre of each of the echoes El and E2 of the fish, for example, is identified as a position of the area centre of each of the echoes El and E2 of the fish or a position at which a signal intensity level of an echo signal of each of the echoes El and E2 of the fish is the highest.

[Fish centre absolute coordinates calculating unit] [0042] The fish centre absolute coordinates calculating unit 14 calculates absolute coordinates of the centre of the echo of the fish based on the subject ship position information acquired by the subject ship position information acquiring unit 11 and the relative coordinates of the centre of the echo of the fish calculated by the fish centre relative coordinates calculating unit 13. For each of the echoes El and E2 of fish, the fish centre absolute coordinates calculating unit 14 calculates the absolute coordinates of the centre of the echo of the fish as three-dimensional coordinates for each of the echoes El and E2 of fish. In other words, in the example illustrated in FIG. 4, the fish centre absolute coordinates calculating unit 14 calculates the absolute coordinates of the position of the centre of the echo El of the fish and the absolute coordinates of the position of the centre of the echo E2 of the fish as three-dimensional coordinates.

[0043] In addition, as the subject ship position information is acquired by the subject ship position information acquiring unit 11, the position of the subject ship S is identified by the absolute coordinates. Then, the fish centre absolute coordinates calculating unit 14 calculates the absolute coordinates of the centre of each of the echoes El and E2 of the fish by adding the relative coordinates of the position of the centre of each of the echoes

El and E2 of the fish to the coordinates of the position of the subject ship S identified by the absolute coordinates for each of the echoes El and E2 of the fish.

[Correspondence relation identifying and association information generating units] [0044] The correspondence relation identifying unit 17 identifies a correspondence relation between a first fish echo that is an echo of fish detected at a first timing and a second fish echo that is an echo of fish detected at a second timing. Then, the association information generating unit 15 generates association information that associates the first fish echo and the second fish echo for which the correspondence relation has been identified by the correspondence relation identifying unit 17. The first timing, for example, is set as a newest timing (in other words, a latest timing). In addition, the first timing may be set as a timing before the latest timing instead of the latest timing. The second timing is set as a timing before the first timing. Accordingly, the first fish echo is an echo of fish detected by the fish echo detecting unit 12 from an echo signal generated by the sonar sensor 3 at a first timing configured as a latest timing or the like. The second fish echo is an echo of fish detected by the fish echo detecting unit 12 from an echo signal generated by the sonar sensor 3 at a second timing that is set as a timing before the first timing. A correspondence relation between the first fish echo and the second fish echo detected at different timings is identified by the correspondence relation identifying unit 17, and the association information is generated by the association information generating unit 15. In this embodiment, the correspondence relation identifying unit 17 is configured to associate the first fish echo and the second fish echo with each other based on the absolute coordinates of the centres of the echoes of the fish and identify the correspondence relation therebetween. The association information generating unit 15 is configured to generate association information associating the first fish echo and the second fish echo for which a correspondence relation has been identified based on the absolute coordinates of the centres of the echoes of the fish.

[0045] In addition, every time when an echo signal is generated by the sonar sensor 3, an echo of fish is detected by the fish echo detecting unit 12, and the absolute coordinates of the centre of the echo of fish are calculated by the fish centre absolute coordinates calculating unit 14, the correspondence relation identifying unit 17 and the association information generating unit 15 identify a correspondence relation between the first fish echo and the second fish echo and generate the association information associating them. As the second fish echo of which the correspondence relation with the first fish echo is identified, and the association information is generated in association with the first fish echo, for example, an echo of fish detected at a second timing as a timing that is one timing before the first timing at which the first fish echo has been detected is selected. Alternatively, as the second fish echo, an echo of fish detected at the second timing set as a timing that is plurality of timings before the first timing at which the first fish echo is detected may be selected.

[0046] FIG. 5 is a diagram illustrating a process of the correspondence relation identifying unit 17 and is a diagram illustrating a process of identifying a correspondence relation between the first fish echo and the second fish echo. FIG. 5 schematically illustrates a state in which echoes El and E2 of fish are detected in a detection area DR and a state that echoes El’ and E2’ of fish are detected in a detection area DR’. In addition, in FIG. 5, a detection area DR corresponding to a transmission space TS where transmission waves are transmitted at a timing corresponding to the first timing set as a latest timing or the like and outlines of first fish echoes El and E2 that are echoes El and

E2 of fish detected at the first timing in the detection area DR are denoted by solid lines. In FIG. 5, a detection area DR’ corresponding to a transmission space TS where transmission waves are transmitted at a timing corresponding to the second timing that is a timing before the first timing and outlines of second fish echoes El’ and E2’ that are echoes El’ and E2’ of fish detected at the second timing in the detection area DR’ are denoted by dashed lines.

[0047] The correspondence relation identifying unit 17 respectively associates the first fish echoes El and E2 having centres present within a predetermined distance from the centres of the second fish echoes El’ and E2’ with the second fish echoes El’ and E2’. More specifically, in order to identify correspondence relations between first fish echoes El and E2 and second fish echoes El’ and E2’, the association information generating unit 15, first, identifies the first fish echoes El and E2 having centres present within a predetermined distance from the centres of the second fish echoes El’ and E2’. At this time, the correspondence relation identifying unit 17 sets spheres SI and S2 of a predetermined radius R (in other words, a predetermined distance R) for setting ranges where fish can move with the centre positions of the second fish echoes El’ and E2’ set as centres on absolute coordinates. In FIG. 5, the magnitude of the predetermined radius R is denoted by arrows of two-dot dashed lines, and the spheres SI and S2 are denoted by circles of two-dot dashed lines. In addition, a value of the predetermined radius R, for example, is appropriately set based on an input operation from a user. Alternatively, the value of the predetermined radius R is stored in the echo signal processing device 2 as a set value in advance.

[0048] When the spheres SI and S2 having the predetermined radius R with the centre positions of the second fish echoes El’ and E2’ set as centres thereof are set, the correspondence relation identifying unit 17 determines first fish echoes El and E2 having centres present within the spheres SI and S2 on the absolute coordinates. In other words, the first fish echoes El and E2 having centres within a predetermined distance R from the centres of the second fish echoes El’ and E2’ are determined. Then, the second fish echoes El’ and E2’ respectively corresponding to the first fish echoes El and E2 are identified. In this way, the correspondence relation identifying unit 17 identifies such a correspondence relation by respectively associating the first fish echoes El and E2 with the second fish echoes El’ and E2’. In the example illustrated in FIG. 5, the first fish echo El having its centre within the sphere SI having the radius R centred on the second fish echo El’ is determined. In this way, a correspondence relation between the first fish echo El and the second fish echo El’ is identified. In addition, the first fish echo E2 having its centre within the sphere S2 having the radius R centred on the second fish echo E2’ is determined. In this way, a correspondence relation between the first fish echo E2 and the second fish echo E2’ is identified. Accordingly, correspondence relations between the first fish echoes El and E2 corresponding to the same fish and the second fish echoes El’ and E2 are identified.

[0049] In a case that a plurality of second fish echoes El’ and E2’ are not close to each other and the centres of the first fish echoes El and E2 are respectively present inside the spheres S1 and S2 having the predetermined radius R centred on the centre positions of the second fish echoes El’ and E2’, the correspondence relations between the first fish echoes El and E2 and the second fish echoes El’ and E2’ are identified. However, in a case that a plurality of second fish echoes El’ and E2’ are close to each other, and the centres of a plurality of first fish echoes are present inside spheres having the predetermined radius R centred on the centre positions of the second fish echoes, for example, a second fish echo and a first fish echo having a short distance therebetween are associated with each other. Alternatively, in the case described above, a second fish echo and a first fish echo may be associated with each other in order of intensities of echo signals. When the second fish echoes ΕΓ and E2’ respectively corresponding to the first fish echoes El and E2 are identified as described above, the association information generating unit 15 generates association information respectively associating the first fish echoes El and E2 with the second fish echoes El’ and E2’ corresponding thereto. In other words, the association information generating unit 15 generates association information respectively associating the first fish echoes El and E2 and the second fish echoes El’ and E2’ with each other of which the correspondence relations are identified by the correspondence relation identifying unit 17. At this time, the association information generating unit 15 generates the association information based on the absolute coordinates of the centres of the first fish echoes El and E2 and the absolute coordinates of the centres of the second fish echoes El’ and E2’. FIG. 6 is a diagram illustrating a process of the association information generating unit 15 and is a diagram schematically illustrating association information images VI and V2 together with the first fish echoes El and E2, the second fish echoes El’ and E2’ and the detection area DR as an example. The association information images VI and V2 schematically illustrated in FIG. 6 as an example are display images when the association information generated by the association information generating unit 15 is displayed on the display unit 4.

[0050] The association information generating unit 15 generates information of vectors respectively connecting the first fish echoes El and E2 and the second fish echoes El’ and E2’ as the association information associating the first fish echoes El and E2 and the second fish echoes El’ and E2’ with each other of which the correspondence relations are identified. In other words, in the example illustrated in FIG. 6, the association information generating unit 15 generates vector information connecting the first fish echo El and the second fish echo El’ as association information of the first fish echo El and the second fish echo El’. Then, the association information generating unit 15 generates the vector information vector connecting the first fish echo E2 and the second fish echo E2’ as the association information of the first fish echo E2 and the second fish echo E2’. Referring to FIG. 6, the association information image VI is a display image of the vector information connecting the first fish echo El and the second fish echo El’, and the association information image V2 is a display image of vector information connecting the first fish echo E2 and the second fish echo E2’.

[0051] When the association information is generated, in other words, in order to generate the vector information respectively connecting the first fish echoes El and E2 and the second fish echoes El’ and E2’, the association information generating unit 15 generates the vector information respectively connecting the absolute coordinates of the centres of the echoes of the fish.

[0052] More specifically, in order to generate the vector information connecting the first fish echo El and the second fish echo El’, the association information generating unit 15 generates the vector information vector connecting the absolute coordinates of the centre of the second fish echo El’ from the absolute coordinates of the centre of the first fish echo El. In this way, the vector information to which the association information image VI corresponds is generated as the vector information connecting the first fish echo El and the second fish echo El’. In addition, the vector information connecting the first fish echo El and the second fish echo El’ forms information of a velocity vector representing a movement velocity of fish to which the first fish echo El corresponds or information indicating the velocity vector.

[0053] In addition, in order to generate the vector information connecting the first fish echo E2 and the second fish echo E2’, the association information generating unit 15 may generate the vector information connecting the absolute coordinates of the centre of the second fish echo E2’ to the absolute coordinates of the centre of the first fish echo E2. In this way, the vector information to which the association information image V2 corresponds is generated as the vector information connecting the first fish echo E2 and the second fish echo E2’. In addition, the vector information connecting the first fish echo E2 and the second fish echo E2’ forms information of a velocity vector representing a movement velocity of fish to which the first fish echo E2 corresponds or information indicating the velocity vector.

[Display control unit] [0054] The display control unit 16 performs controls of displaying the echoes of the fish and the association information as the vector information generated by the association information generating unit 15 on the display unit 4. More specifically, the display control unit 16 generates display video data used for displaying the echoes of the fish and the association information on the display unit 4 and outputs the display video data on the display unit 4, and thereby, the display control unit 16 performs controls of displaying the echoes of the fish and the association information on the display unit 4. In this embodiment, the display control unit 16 generates the display video data used for displaying second fish echoes El’ and E2’ and first fish echoes El and E2 on the display unit 4 together with association information and outputs the display video data to the display unit 4. In this way, the display control unit 16 performs controls of displaying the second fish echoes El’ and E2’ and the first fish echoes El and E2 on the display unit together with the association information.

[0055] In addition, for example, by performing isosurface processing (in other words, a surface rendering process) or a volume rendering process, the display control unit 16 may generate the display video data including data used for displaying the echoes El, E2, El’, and E2’ of fish as a three-dimensional video. Furthermore, the display control unit 16 generates the display video data including data for displaying the vector information respectively connecting the first fish echoes El and E2 and the second fish echoes El’ and E2’. At this time, in this embodiment, the display control unit 16 generates the display video data including data used for displaying vectors respectively connecting the first fish echoes El and E2 and the second fish echoes El’ and E2’ on the display unit 4 as segment displays, and outputs the generated display video data to the display unit 4. In this way, the display control unit 16 performs controls of displaying the vectors respectively connecting the first fish echoes El and E2 and the second fish echoes El’ and E2’ on the display unit 4 as segment displays.

[0056] In addition, in this embodiment, the display control unit 16 generates display video data also including data used for displaying isobaths representing equal-depth positions of seabed topology based on the seabed information acquired from the sea map on the display unit 4. Furthermore, in this embodiment, the display control unit 16 generates display video data also including data used for displaying a movement history of the detection area DR that moves in accordance with the movement of the subject ship

S.

[0057] The display video data generated by the display control unit 16 is output to the display unit 4 and is displayed on the display screen of the display unit 4. FIG. 7 is a diagram schematically illustrating one example of a video displayed on the display screen of the display unit 4. In addition, in the display example illustrated in FIG. 7, a form in which the display unit 4 displays in a three-dimensional manner an undersea state below the subject ship S as a bird’s eye view is illustrated as an example. As illustrated in FIG. 7, the display unit 4 displays the echoes El, E2, El’, and E2’ of fish and the segment displays of the vectors that serve as the displays of the association information between the first fish echoes El and E2 and the second fish echoes El’ and E2’ based on the display video data generated by the display control unit 16.

[0058] In the display of the echoes El, E2, El’, and E2’ of fish illustrated in FIG. 7 as an example, an area of an echo for which an intensity level of a corresponding echo signal is high is illustrated as an area to which oblique hatching is applied, and an area of an echo for which an intensity level of a corresponding echo signal is low is illustrated as an area to which dot hatching is applied. In the display video data generated by the display control unit 16, information of display colours used at the time of display on the display unit 4 is included. On the display unit 4, for example, an area to which the oblique hatching is applied is represented in red, and an area to which the dot hatching is applied is represented in yellow.

[0059] In addition, as illustrated in FIG. 7 as an example, the association information between the first fish echoes El and E2 and the second fish echoes El’ and E2’ is displayed as the segment displays of vectors respectively connecting the second fish echoes El’ and E2’ and the first fish echoes El and E2. In other words, more specifically, as the association information between the first fish echo El and the second fish echo El’, the association information image VI as a segment display of a vector connecting the second fish echo El’ to the first fish echo El is displayed. As the association information between the first fish echo E2 and the second fish echo E2’, the association information image V2 as a segment display of a vector connecting the second fish echo E2’ to the first fish echo E2 is displayed. On the display unit 4, the association information images VI and V2 are displayed in a colour different from the colours of the echoes El, E2, El’, and E2’ of fish. For example, in a case that the echoes El, E2, El’ and E2’ of fish are displayed in red and yellow, the association information images V1 and V2 may be displayed in black.

[0060] In addition, as illustrated in the display example illustrated in FIG. 7, in this embodiment, the detection area DR where the first fish echoes El and E2 have been detected is also displayed on the display unit 4 together with the echoes El, E2, El’, and E2’ of fish and the association information images VI and V2. Furthermore, as illustrated in the display example illustrated in FIG. 7, in this embodiment, isobaths VL representing equal-depth positions of the seabed topology and the movement history DH of the detection area DR moving in accordance with the movement of the subject ship S are also displayed on the display unit 4 based on the display video data generated by the display control unit 16. In addition, as the movement history DH of the detection area DR displayed on the display unit 4, for example, a history of only an area where the detection area has moved along the surface of the seabed among areas where the detection area DR has moved may be displayed.

[0061] In addition, in the display example illustrated in FIG. 7, although a form in which the display unit 4 displays in a three-dimensional manner an underwater state below the subject ship S as a birds’ eye view has been illustrated as an example, the display unit 4 may display the underwater state in a different display form. In other words, the display unit 4 may display the echoes El, E2, El’, and E2’ of fish and the association information between the first fish echoes El and E2 and the second fish echoes El’ and

E2’ based on the display video data generated by the display control unit 16 in a form different from that of the display example illustrated in FIG. 7. FIG. 8 is a diagram schematically illustrating one example of a video displayed on the display screen of the display unit 4 and is a diagram illustrating another display example different from the display example illustrated in FIG. 7. In the display example illustrated in FIG. 8, the display unit 4 displays an underwater state below the subject ship S as a video that is seen from above in a two-dimensional manner.

[0062] As illustrated in the display example illustrated in FIG. 8, based on the display video data, the display unit 4 may display the echoes El, E2, El’, and E2’ of fish and the association information images VI and V2 ass a video seen from above in a two-dimensional manner together with the detection area DR, the movement history DH of the detection area DR, and the isobaths VL. In addition, switchings between the video in the form illustrated in FIG. 7 and the video in the form illustrated in FIG. 8 may be appropriately performed, for example, based on a user’s operation. For example, as an example, in accordance with a user’s appropriate operation of an operation device (not illustrated in the drawing) such as a keyboard, a pointing device, or the like included in the echo signal processing system 1 according to this embodiment, the video in the form illustrated in FIG. 7 or the video in the form illustrated in FIG. 8 may be displayed on the display unit 4.

[Operation of echo signal processing device and echo signal processing system] [0063] FIG. 9 is a flowchart illustrating operations of the echo signal processing device 2 and the echo signal processing system 1 and is a flowchart illustrating one example of the operations of the echo signal processing device 2 and the echo signal processing system 1.

FIG. 9 illustrates operations in which the transmission waves are transmitted in the water from the transducer 5 of the sonar sensor 3, reflected waves of the transmission waves are received by the transducer 5, and the above-described process using the echo signal processing device 2 is performed, and the video of echoes El, E2, El’, and E2’ of fish and the association information images VI and V2 are displayed on the display unit 4. When the transmission waves are transmitted from the transducer 5 in the water after the video of the echoes El, E2, El’, and E2’ of fish and the like is displayed on the display unit 4, the operations illustrated in the flowchart of FIG. 9 are performed again. As illustrated in FIG. 9, by performing the operations of the echo signal processing device 2, an echo signal processing method according to this embodiment is performed.

[0064] In the operations of the echo signal processing device 2 and the echo signal processing system 1, first, the transmission waves are transmitted from the transducer 5 of the sonar sensor 3 to the transmission space TS in the water. The transmission waves transmitted to the transmission space TS in the water are reflected at targets such as fish and the like in the water and are received by the transducer 5. The transducer 5 receives the reflected waves of the transmission waves at the targets in the water and generates the echo signals based on the received reflected waves (Step S101). When the echo signals are generated, the transducer 5 outputs the generated echo signals to the transceiver 6. In the transceiver 6, the reception circuit unit 9 amplifies the received echo signals, eliminates unnecessary frequency components, converts the echo signals into digital signals, and outputs the converted echo signals to the echo signal processing device 2.

[0065] When echo signals are input from the transceiver 6, the echo signal processing device 2 detects the echoes of the fish by the fish echo detecting unit 12 (Step S102). In other words, the fish echo detecting unit 12, as described above, detects the echoes of the fish from the echo signals generated by the sonar sensor 3 based on the reflected waves of the transmission waves transmitted in the water. When the fish echo detecting unit 12 detects the echoes of the fish, thereafter, the subject ship position information that is information of a position of the subject ship S in which the sonar sensor 3 is mounted is acquired as described above by the subject ship position information acquiring unit 11. In FIG. 9, although a form in which the subject ship position information is acquired by the subject ship position information acquiring unit 11 after the echoes of the fish are detected by the fish echo detecting unit 12 has been illustrated as an example, the form may be changed. A form in which the echoes of the fish are detected by the fish echo detecting unit 12 after the subject ship position information is acquired by the subject ship position information acquiring unit 11 may be employed.

[0066] When the subject ship position information is acquired, and the echoes of the fish are detected, thereafter, the fish centre relative coordinates calculating unit 13, as described above, calculates the relative coordinates of the centres of the echoes of the fish with reference to the position of the subject ship S based on the echoes of the fish (Step S104). When the relative coordinates of the centres of the echoes of fish are calculated, thereafter, the fish centre absolute coordinates calculating unit 14, as described above, calculates absolute coordinates of the centres of the echoes of fish based on the subject ship position information and the relative coordinates of the centres of the echoes of fish (Step S105).

[0067] When the absolute coordinates of the centres of the echoes of fish are calculated, thereafter, the correspondence relation identifying unit 17, as described above, identifies the correspondence relations between first fish echoes El and E2 and second fish echoes El’ and E2’ (Step S106). Then, after the process of identifying a correspondence relation made by the correspondence relation identifying unit 17, the association information generating unit 15, as described above, generates the association information associating the first fish echoes El and E2 and the second fish echoes El’ and E2’ for which the correspondence relation has been identified with each other based on the absolute coordinates of the centres of the echoes of fish (Step S107). As described above, the first fish echoes El and E2 are the echoes El and E2 of fish detected at a first timing set as a latest timing or the like, and the second fish echoes El’ and E2’ are the echoes El’ and E2’ of fish detected at a second timing that is a timing before the first timing. In addition, as described above, the association information generating unit 15 generates the vector information respectively connecting the first fish echoes El and E2 and the second fish echoes El’ and E2’ as the association information between the first fish echoes El and E2 and the second fish echoes El’ and E2’. At a timing at which the echoes of the fish are detected first after the start of the operations of the echo signal processing device 2 and the echo signal processing system 1, for example, a state in which there are only the first fish echoes detected at the first timing set as a latest timing, and no second fish echo is yet present is formed. In this case, generations of the association information are not performed by the association information generating unit 15. Then, at a timing at which the echoes of the fish at the next time and subsequent times are detected, the second fish echoes are present, and accordingly, generations of the association information are performed at each of the times.

[0068] When the association information between the first fish echoes El and E2 and the second fish echoes El’ and E2’ is generated, thereafter, the display control unit 16, as described above, generates the display video data used for displaying the echoes El, E2, El’, and E2’ of fish and the association information on the display unit 4 (Step S108).

Then, the display video data generated by the display control unit 16 is output to the display unit 4 (Step S109). In this way, controls of displaying the echoes El, E2, El’, and E2’ of fish and the association information on the display unit 4 are performed by the display control unit 16. The display unit 4 displays the echoes of the fish and the association information on the display unit 4 based on the input display video data. In other words, as illustrated in FIG. 7 or 8 as an example, the first fish echoes El and E2 and the second fish echoes El’ and E2’ are displayed, and the association information images VI and V2 are displayed on the display unit 4. When the echoes El, E2, El’, and E2’ of fish and the association information images VI and V2 are displayed on the display unit 4, the operations of the echo signal processing device 2 and the echo signal processing system 1 illustrated in FIG. 9 end once. When the operations of the echo signal processing device 2 and the echo signal processing system 1 illustrated in FIG. 9 end once, the transmission waves are transmitted from the transducer 5 to the transmission space TS in the water, and the operation illustrated in FIG. 9 starts again. [Effects] [0069] According to this embodiment, the association information that associates the first fish echo detected at the first timing with the second fish echo that is detected at the second timing, which is a timing before the first timing, of which a correspondence relation with the first fish echo is identified is generated. Then, according to this embodiment, the echoes of the fish and the association information are displayed on the display unit 4 under the controls of the display control unit 16. More specifically, the display control unit 16 generates display video data used for displaying the echoes of the fish and the association information on the display unit 4, and the echoes of the fish and the association information are displayed on the display unit 4 based on the display video data. For this reason, the user can immediately grasp movements of fish from the second timing that is a timing before the first timing to the first timing thereafter only by looking at the echoes of the fish and the association information displayed on the displayer 4. In other words, according to this embodiment, the user can grasp the status of the movements of fish easily and quickly only by looking at the display of the displayer 4.

[0070] Thus, according to this embodiment, the echo signal processing device 2, the echo signal processing system 1, and the echo signal processing method allowing the user to grasp the status of the movements of fish easily and quickly can be provided.

[0071] In addition, according to this embodiment, the display control unit 16 performs the controls of displaying the second fish echoes El’ and E2’ and the first fish echoes El and E2 on the display unit 4 together with the association information, and the display on the display unit 4 is performed based on the controls. For this reason, the user can grasp the positions of the second fish echoes El’ and E2’ and the positions of the first fish echoes El and E2 and the association information at one time only by looking at the display of the display unit 4 and thus can grasp the status of the movements of fish more easily and quickly.

[0072] In addition, according to this embodiment, the association information generating unit 15 generates the vector information respectively connecting the second fish echoes El’ and E2’ and the first fish echoes El and E2 as the association information. Then, the display control unit 16 performs the controls of displaying the vectors on the display unit 4 as the segment displays, and the display on the display unit 4 is performed based on the control. For this reason, the user can grasp the movements of fish more intuitively in accordance with the segment displays of the vectors respectively connecting the second fish echoes El’ and E2’ and the first fish echoes El and E2 and thus can grasp the status of the movements of fish more easily and quickly.

[First modified example] [0073] FIG. 10 is a diagram illustrating the first modified example of the embodiment described above and is a diagram schematically illustrating one example of a video displayed on the display screen of the display unit 4. In the following description, points different from those of the embodiment described above will be described, and the same reference signs will be attached to configuration components similar to or corresponding to those in the embodiment described above in drawings, or the same reference signs will be cited for the configuration components, and thus, duplicate descriptions will be appropriately omitted.

[0074] In the embodiment described above, the second fish echoes El’ and E2’ and the first fish echoes El and E2 are displayed on the display unit 4 together with the association information. In contrast to this, in the first modified example, the second fish echoes El’ and E2’ are not displayed on the display unit 4, and the first fish echoes El and E2 are displayed on the display unit 4 together with the association information.

[0075] As a more specific configuration, in the first modified example, the display control unit 16 generates display video data used for causing the display unit 4 to display the first fish echoes El and E2 together with the association information associating the first fish echoes El and E2 with the second fish echoes El’ and E2’ and outputs the generated display video data to the display unit 4. In this way, the display control unit 16 performs controls of displaying the first fish echoes El and E2 on the display unit 4 together with the association information. Then, the display unit 4, as illustrated in FIG. 10, displays the first fish echoes El and E2 and segment displays of vectors as displays of the association information between the first fish echoes El and E2 and the second fish echoes El’ and E2’ based on the controls of the display control unit 16. In the display example illustrated in FIG. 10, a form in which association information images VI and V2 as the segment displays of vectors that are the displays of the association information between the first fish echoes El and E2 and the second fish echoes El’ and E2’ are displayed as the segment displays of vectors extending from the centre positions of the first fish echoes El and E2 serving as start points is illustrated. In addition, the display is not limited to the display example illustrated in FIG. 10, and the association information images VI and V2 that are the displays of the association information between the first fish echoes El and E2 and the second fish echoes El’ and E2’ may be displayed as the segment displays of vectors extending to the centre positions of the first fish echoes El and E2 as end points.

[0076] As in the first modified example, a form in which the second fish echoes El’ and E2’ are not displayed on the display unit 4, and the first fish echoes El and E2 are displayed on the display unit 4 together with the association information may be employed.

[Second modified example] [0077] FIG. 11 is a diagram illustrating the second modified example of the embodiment described above and is a diagram schematically illustrating one example of a video displayed on the display screen of the display unit 4. In the following description, points different from those of the embodiment described above will be described, and the same reference signs will be attached to configuration components similar to or corresponding to those in the embodiment described above in drawings, or the same reference signs will be cited for the configuration components, and thus, duplicate descriptions will be appropriately omitted. In the embodiment described above, the second fish echoes El’ and E2’ and the first fish echoes El and E2 are displayed on the display unit 4 together with the association information, and the segment displays of vectors as displays of the association information are displayed on the display unit 4. In contrast to this, in the second modified example, the second fish echoes El’ and E2’ are not displayed on the display unit 4, and the first fish echoes El and E2 are displayed on the display unit 4 together with the association information, and information including numerical values of vectors is displayed on the display unit 4 as displays of the association information.

[0078] As a more specific configuration, in the second modified example, the association information generating unit 15 generates the information including the numerical values of vectors respectively connecting the second fish echoes El’ and E2’ and the first fish echoes El and E2 as association information associating the first fish echoes El and E2 with the second fish echoes El’ and E2’. Furthermore, in the second modified example, the association information generating unit 15 generates the information including the numerical values of velocity vectors of fish representing movement velocities of fish to which the first fish echoes El and E2 correspond as the information including the numerical values of vectors respectively connecting the second fish echoes El’ and E2’ and the first fish echoes El and E2. In addition, the information including the numerical values of velocity vectors of fish to which the first fish echoes El and E2 correspond, for example, is calculated based on the absolute coordinates of the centres of the second fish echoes El’ and E2’, the absolute coordinates of the centres of the first fish echoes El and E2, and times when the reflected waves to which the echoes El’, E2’, El, and E2 correspond are received by the sonar sensor 3.

[0079] In addition, the association information generating unit 15 generates information of velocity in the horizontal direction and information of velocity in the vertical direction as the information including the numerical values of a velocity vector of fish to which each of the first fish echoes El and E2 corresponds. In other words, the association information generating unit 15 generates the information including an orientation and a speed of each school of fish in the horizontal direction and an orientation and a speed in the vertical direction as the information including the numerical values of the velocity vector of each school of fish to which each of the first fish echoes El and E2 corresponds. As the information of the velocity in the horizontal direction, information of orientations of a horizontal-direction component of the velocity vectors of fish with respect to the direction of the bow of the subject ship S and information of speeds of the horizontal-direction component of the velocity vectors of the fish are generated. Alternatively, as the information of the velocity in the horizontal direction, information of orientations of a horizontal-direction component of velocity vectors of fish and information of speeds of the horizontal-direction component of the velocity vectors of the fish in the absolute azimuth are generated. As the information of the velocity in the vertical direction, information used for identifying whether the orientation of a vertical-direction component of the velocity vector of the fish is upward or downward and information of velocity of the vertical-direction component of the velocity vector of the fish are generated.

[0080] In addition, the display control unit 16 generates the display video data used for displaying the echoes of the fish and the association information on the display unit 4 based on the association information generated by the association information generating unit 15. In the second modified example, the display control unit 16 generates the display video data including data used for displaying the information including the numerical values of the vectors respectively connecting second fish echoes El’ and E2’ and first fish echoes El and E2 on the display unit 4 as display video data and outputs the generated display video data to the display unit 4. More specifically, in the second modified example, the display control unit 16 generates the display video data used for displaying the information including the numerical values of velocity vectors of fish to which the first fish echoes El and E2 correspond on the display unit 4 as the information including the numerical values of the vectors respectively connecting the second fish echoes El’ and E2’ and the first fish echoes El and E2 and outputs the generated display video data to the display unit 4. In this way, the display control unit 16 performs controls of displaying the information including the numerical values of the vectors respectively connecting the second fish echoes El’ and E2’ and the first fish echoes El and E2 on the display unit 4.

[0081] The display unit 4, as illustrated in FIG. 11 as an example, displays the first fish echoes El and E2 and the information including the numerical values of the velocity vectors of fish as the display of the association information between the first fish echoes El and E2 and the second fish echoes El’ and E2’ based on the controls of the display control unit 16. In addition, on the displayer 4, an echo No. is displayed for each of the first fish echoes El and E2, and the information including the numerical values of the velocity vector of each school of fish to which each of the first fish echoes El and E2 corresponds is displayed for each echo No. In the display example illustrated in FIG. 11, a form in which “No. 1” is displayed for the first fish echo El as the echo No., and “No. 2” is displayed for the first fish echo E2 as the echo No. is illustrated.

[0082] In addition, on the displayer 4, as the information including the numerical values of velocity vectors of fish respectively corresponding to the first fish echoes El and E2 displayed as the association information, the orientation and the speed of the horizontal direction and the orientation and the speed of the vertical direction of the velocity vector of each school of fish are displayed. In the display example illustrated in FIG. 11, a form in which the orientations and the speeds of the horizontal-direction component of the velocity vectors of fish with respect to the direction of the bow of the subject ship S are displayed as the orientation and the speed of the horizontal direction of the velocity vector of each school of fish is illustrated. More specifically, in the display example illustrated in FIG. 11, a form in which numerical values of “-30°” and “1.5 knots” as the orientation and the speed of the horizontal-direction component, and “upward” and “0.5 knots” as the orientation and the speed of the vertical-direction component are displayed as the information including the numerical values of a velocity vector of fish to which the first fish echo El of which the echo No. is “No. 1” corresponds is illustrated. In addition, a form in which numerical values of “40°” and “1.2 knots” as the orientation and the speed of the horizontal-direction component and “downward” and “0.4 knots” as the orientation and the speed of the vertical-direction component and the like are displayed as the information including the numerical values of the velocity vector of fish to which the first fish echo E2 of which the echo No. is “No. 2” corresponds is illustrated. In addition, in the display example illustrated in FIG. 11, although a form in which the orientations and the speeds of the horizontal-direction component of the velocity vectors of fish with respect to the direction of the bow of the subject ship S are displayed as the orientation and the speed in the horizontal direction of the velocity vector of each school of fish is illustrated, the form may be changed. A form in which the orientation and the speed of the horizontal-direction component of the velocity vector of fish in the absolute azimuth are displayed as the orientation and the speed in the horizontal direction of the velocity vector of each school of fish may be employed. In addition, the orientation and the speed in the horizontal direction of the velocity vector of each school of fish displayed on the displayer 4, for example, may be appropriately switched based on a user’s operation. For example, as one example, by the user appropriately operating an operation device (not illustrated in the drawing) such as a pointing device, on the display unit 4, the orientations and the speeds of the horizontal-direction component of the velocity vectors of fish with respect to the direction of the bow of the subject ship S are displayed, or the orientations and the speeds of the horizontal-direction component of the velocity vectors of fish in the absolute azimuth may be displayed as the orientation and the speed in the horizontal direction of the velocity vector of each school of fish.

[0083] According to the second modified example, the association information generating unit 15 generates the information including the numerical values of the vectors respectively connecting the second fish echoes El’ and E2’ and the first fish echoes El and E2 as the association information. Then, the display control unit 16 performs the controls of displaying the information including the numerical values of the vectors on the display unit 4 and performs the displays on the display unit 4 based on the controls. For this reason, the user can grasp the movements of fish more accurately in accordance with the displays of the information including the numerical values of the vectors connecting the second fish echoes El’ and E2’ and the first fish echoes El and E2.

[0084] In addition, according to the second modified example, the information including the numerical values of the velocity vector of each school of fish to which each of the first fish echoes El and E2 corresponds is generated as the information including the numerical values of the vectors respectively connecting the second fish echoes El’ and E2’ and the first fish echoes El and E2. The orientations and the speeds in the horizontal direction orientation of fish and the orientations and the speeds in vertical direction of fish are included in the information including the numerical values of the velocity vectors, and the information including such numerical values is displayed on the display unit 4. For this reason, the user can accurately grasp the orientations and speeds in the horizontal direction and the orientations and the speeds in the vertical direction of fish.

[Third modified example] [0085] FIG. 12 is a diagram illustrating the third modified example of the embodiment described above and is a diagram schematically illustrating one example of a video displayed on the display screen of the display unit 4. In the following description, points different from those of the embodiment described above will be described, and the same reference sign will be attached to a configuration similar to or corresponding to the embodiment described above in drawings, or the same reference sign will be cited for the configuration, and thus, duplicate description will be appropriately omitted.

[0086] In the embodiment described above, in a case that each of the second fish echoes El’ and E2’ and each of the first fish echoes El and E2 have a one-to-one correspondence relation, association information associating one second fish echo with one first fish echo is generated, and the echoes of the fish are displayed on the display unit 4 together with the association information. In contrast to this, in the third modified example, in a case that a plurality of first fish echoes corresponds to one second fish echo, association information associating one second fish echo with the plurality of first fish echoes is generated, and the fish echoes are displayed on the display unit 4 together with the association information.

[0087] As a specific configuration, in the third modified example, in a case that the plurality of first fish echoes correspond to the second fish echo, the association information generating unit 15 generates the association information associating the second fish echo with the plurality of first fish echoes. In other words, in the third modified example, in a case that a correspondence relation between the first fish echoes and the second fish echo is identified in accordance with the association of the plurality of first fish echoes with one second fish echo by the correspondence relation identifying unit 17, the association information generating unit 15 generates the association information associating one second fish echo and the plurality of first fish echoes for which a correspondence relation has been identified with each other. In addition, as the association information associating the second fish echo and the plurality of first fish echoes corresponding thereto, the association information generating unit 15 generates information of vectors connecting the one second fish echo and the plurality of first fish echoes corresponding thereto. Then, the display control unit 16 generates display video data used for displaying the echoes of the fish on the display unit 4 together with the association information associating the second fish echo with the plurality of first fish echoes and outputs the generated display video data to the display unit 4. At this time, the display control unit 16, for example, generates the display video data including data used for displaying the vectors connecting one second fish echo and the plurality of first fish echoes corresponding thereto on the display unit 4 as segment displays and outputs the generated display video data to the display unit 4. In this way, the display control unit 16 performs controls of displaying the vectors connecting one second fish echo and the plurality of first fish echoes corresponding thereto on the display unit 4 as the segment displays. The displayer 4, as illustrated in FIG. 12 as an example, displays the echoes of the fish and the segment displays of the vectors as displays of the association information based on the controls of the display control unit 16.

[0088] In the display example illustrated in FIG. 12, a case that the correspondence relations between a second fish echo E3’ and two first fish echoes E3a and E3b corresponding to the second fish echo E3’ are identified by the correspondence relation identifying unit 17 is illustrated. Referring to FIG. 12, the association information generating unit 15 generates the information of the vectors respectively connecting the second fish echo E3’ and the two first fish echoes E3a and E3b as the association information. In other words, the association information generating unit 15 generates the information of the vector connecting the second fish echo E3’ and the first fish echo E3a and the information of the vector connecting the second fish echo E3’ and the first fish echo E3b as the association information.

[0089] In order to identify the correspondence relations between the second fish echo E3’ and the plurality of first fish echoes E3a and E3b, the correspondence relation identifying unit 17 sets a sphere having a predetermined radius for setting a movable range of fish centred on a centre position of the second fish echo E3’ on the absolute coordinates. When the sphere having the predetermined radius is set centred on the centre position of the second fish echo E3’, the correspondence relation identifying unit 17 determines the plurality of first fish echoes E3a and E3b having centres inside the sphere on the absolute coordinates. Then, the second fish echo E3’ corresponding to the plurality of first fish echoes E3a and E3b is identified. In other words, the plurality of first fish echoes E3a and E3b are associated with one second fish echo E3’, and the correspondence relation therebetween is identified. In this way, even in a case that fish detected as one second fish echo E3’ at a second timing that is a timing before a first timing is divided into a plurality of schools of fish in the way and is detected as the plurality of first fish echoes E3a and E3b at the first timing, the plurality of first fish echoes E3a and E3b and the second fish echo E3’ are associated with each other.

[0090] The display control unit 16 generates the display video data used for displaying the information of the vectors described above as the association information on the display unit 4 together with the second fish echo E3’ and the first fish echoes E3a and E3b, and outputs the generated display video data to the display unit 4. At this time, the display control unit 16 generates the display video data including the data used for displaying the vectors as the segment displays on the display unit 4. In other words, the display control unit 16 generates the display video data including the data used for displaying the vector connecting the second fish echo E3’ and the first fish echo E3a and the vector connecting the second fish echo E3’ and the first fish echo E3b on the display unit 4 as the segment displays, and outputs the generated display video data to the display unit 4. In this way, the display control unit 16 performs the controls of displaying both the vectors described above on the display unit 4 as the segment displays.

[0091] The display unit 4, as illustrated in FIG. 12, displays the second fish echo E3’ the first fish echoes E3a and E3b, and the segment displays of the vectors as the association information between the first fish echoes E3a and E3b and the second fish echo E3’ based on the control of the display control unit 16. In other words, more specifically, the association information images V3a and V3b as the segment displays of the vectors respectively connecting the second fish echo E3’ and two first fish echoes E3a and E3b are displayed on the display unit 4 together with the second fish echo E3’ and the first fish echoes E3a and E3b. Here, the association information image V3a is a segment display of the vector connecting the second fish echo E3’ and the first fish echo E3a, and the association information image V3b is a segment display of the vector connecting the second fish echo E3’ and the first fish echo E3b.

[0092] According to the third modified example, in a case that the plurality of first fish echoes E3a and E3b correspond to one second fish echo E3’, the association information generating unit 15 generates the association information that associates the second fish echo E3’ with the plurality of first fish echoes E3a and E3b. Then, the display control unit 16 performs controls of displaying the association information between the second fish echo E3’ and the plurality of first fish echoes E3a and E3b on the display unit 4, and performs displays on the display unit 4 based on the control. For this reason, even in a case that one school of fish is divided into a plurality of schools of fish in the way, the user can grasp the status of the movements of one school of fish divided into a plurality of schools of fish easily and quickly through the displays of the association information that associates the second fish echo E3’ with the plurality of first fish echoes E3a and E3b.

[Fourth modified example] [0093] FIG. 13 is a diagram illustrating the fourth modified example of the embodiment described above and is a diagram schematically illustrating one example of a video displayed on the display screen of the display unit 4. In the following description, points different from those of the embodiment described above will be described, and the same reference sign will be attached to a configuration similar to or corresponding to the embodiment described above in drawings, or the same reference sign will be cited for the configuration, and thus, duplicate description will be appropriately omitted.

[0094] In the embodiment described above, in a case that each of the first fish echoes El and E2 and each of the second fish echoes El’ and E2’ have a one-to-one correspondence relation, association information associating one second fish echo with one first fish echo is generated, and the echoes of the fish are displayed on the display unit 4 together with the association information. In contrast to this, in the fourth modified example, in a case that a plurality of second fish echoes corresponds to one first fish echo, the association information associating one first fish echo with the plurality of second fish echoes is generated, and the fish echoes are displayed on the display unit 4 together with the association information.

[0095] As a specific configuration, in the fourth modified example, in a case that the plurality of second fish echoes correspond to the first fish echo, the association information generating unit 15 generates the association information associating the plurality of second fish echoes with the first fish echoes. In other words, in the fourth modified example, in a case that a correspondence relation between the first fish echo and the second fish echoes is identified in accordance with associations of the plurality of second fish echoes with one first fish echo by the correspondence relation identifying unit 17, the association information generating unit 15 generates the association information associating one first fish echo and the plurality of second fish echoes for which the correspondence relation has been identified with each other. In addition, as the association information associating the first fish echo and the plurality of second fish echoes corresponding thereto, the association information generating unit 15 generates information of vectors connecting the one first fish echo and the plurality of second fish echoes corresponding thereto. Then, the display control unit 16 generates display video data used for displaying the echoes of the fish on the display unit 4 together with the association information associating the first fish echo with the plurality of second fish echoes, and outputs the generated display video data to the display unit 4. At this time, the display control unit 16, for example, generates the display video data including data used for displaying the vectors connecting the plurality of second fish echoes and one first fish echo corresponding thereto on the display unit 4 as segment displays, and outputs the generated display video data to the display unit 4. In this way, the display control unit 16 performs controls of displaying the vectors connecting the plurality of second fish echoes and one first fish echo corresponding thereto on the displayer 4 as the segment displays. The display unit 4, as illustrated in FIG. 13, displays the echoes of the fish and the segment displays of the vectors as the displays of the association information based on the controls of the display control unit 16.

[0096] In the display example illustrated in FIG. 13, a case that the correspondence relations between two second fish echoes E4’a and E4’b and one first fish echo E4 corresponding to such second fish echoes E4’a and E4’b are identified by the correspondence relation identifying unit 17 is illustrated. Referring to FIG. 13, the association information generating unit 15 generates the information of the vectors respectively connecting the two second fish echoes E4’a and E4’b and the one first fish echo E4 as the association information. In other words, the association information generating unit 15 generates the information of the vector connecting the second fish echo E4’a and the first fish echo E4 and the information of the vector connecting the second fish echo E4’b and the first fish echo E4 as the association information.

[0097] In order to identify the correspondence relations between the plurality of second fish echoes E4’a and E4’b and the first fish echo E4, the correspondence relation identifying unit 17 sets a sphere having a predetermined radius for setting a movable range of fish centred on a centre position of each of the second fish echoes E4’a and E4’b on the absolute coordinates. When the sphere having the predetermined radius is set centred on the centre position of each of the second fish echoes E4’a and E4’b, the correspondence relation identifying unit 17 determines the first fish echo E4 having the centre inside the sphere on the absolute coordinates. Then, the plurality of second fish echoes E4’a and E4’b corresponding to the first fish echo E4 are identified. In other words, one first fish echo E4 and the plurality of second fish echoes E4’a and E4’b are associated with each other, and the correspondence relation therebetween is identified. In this way, even in a case that a plurality of schools of fish detected as the plurality of second fish echoes E4’a and E4’b at a timing before a first timing aggregate into one school of fish in the way, and are detected as one school of first fish echo E4 at the first timing, one first fish echo E4 and the plurality of second fish echoes E4’a and E4’b are associated with each other.

[0098] The display control unit 16 generates the display video data used for displaying the information of the vectors described above as the association information on the display unit 4 together with the plurality of second fish echoes E4’a and E4’b and the first fish echo E4 and outputs the generated display video data to the display unit 4. At this time, the display control unit 16 generates the display video data including the data used for displaying the vectors as the segment displays on the display unit 4. In other words, the display control unit 16 generates the display video data including the data used for displaying the vector connecting the second fish echo E4’a and the first fish echo E4 and the vector connecting the second fish echo E4’b and the first fish echo E4 on the display unit 4 as the segment displays, and outputs the generated display video data to the display unit 4. In this way, the display control unit 16 performs the controls of displaying both the vectors described above on the display unit 4 as the segment displays. [0099] The display unit 4, as illustrated in FIG. 13, displays the second fish echoes E4’a and E4’b, the first fish echo E4 and the segment displays of the vectors as the association information between the first fish echo E4 and the second fish echoes E4’a and E4’b based on the controls of the display control unit 16. In other words, more specifically, the association information images V4a and V4b as the segment displays of the vectors respectively connecting the two second fish echoes E4’a and E’4b and the first fish echo E4 are displayed on the display unit 4 together with the two second fish echoes E4’a and E4’b and the first fish echo E4. Here, the association information image V4a is a segment display of the vector connecting the second fish echo E4’a and the first fish echo E4, and the association information image V4b is a segment display of the vector connecting the second fish echo E4’b and the first fish echo E4.

[0100] According to the fourth modified example, in a case that the plurality of second fish echoes E4’a and E4’b correspond to the first fish echo E4, the association information generating unit 15 generates the association information that associates the plurality of second fish echoes E4’a and E4’b with the first fish echo E4. Then, the display control unit 16 performs the controls of displaying the association information between the plurality of second fish echoes E4’a and E4’b and the first fish echo E4 on the display unit 4, and performs display on the display unit 4 based on the controls. For this reason, even in a case that a plurality of schools of fish aggregate into one school of fish in the way, the user can grasp the status of the movements of a plurality of schools of fish aggregating into one school of fish easily and quickly through the display of the association information that associates the plurality of second fish echoes E4’a and E4’b with the first fish echo E4.

[Other modified examples] [0101] As above, although the embodiment of the present invention and the modified examples thereof have been described, the present invention is not limited to these, and various changes can be made as long as the concept does not depart from the concept of the present invention.

[0102] (1) In the embodiment and the modified examples described above, although the form of the echo signal processing system in which the sonar sensor includes the transducer functioning as a wave transmitter and also functioning as a wave receiver has been described as an example, the form may be changed. For example, a form of the echo signal processing system including a sonar sensor that includes a wave transmitter and a wave receiver separately may be employed.

[0103] (2) In the embodiment and the modified examples described above, although the form of the echo signal processing system including the sonar sensor disposed as a scanning sonar that forms transmission beams in all the directions together in the water, which has the subject ship as its centre, has been described as an example, the form may be changed. For example, a form of the echo signal processing system including a sonar sensor disposed as a search light sonar (PPI sonar) rotating transmission beams and reception beams may be employed.

[0104] (3) In the embodiment and the modified examples described above, although the form in which the association information is displayed as the segment displays of the vectors or the displays of the numerical values and the like of the vectors has been described as an example, the form may be changed. For example, a form in which the displays of the association information are displayed as a display image of a cylinder connecting the second fish echo and the first fish echo or a display image of a cone connecting the second fish echo and the first fish echo may be employed. In addition, in such a case, a display size of the diameter of a circular cross-section of the cylinder in the display image of the cylinder may be determined in accordance with an intensity level of an echo signal to which the second fish echo or the first fish echo corresponds. Furthermore, a display size of the diameter of a circle of the bottom face of the cone in the display image of the cone may be determined in accordance with an intensity level of an echo signal to which the second fish echo or the first fish echo corresponds.

[0105] (4) In the embodiment and the modified examples described above, although the form in which the association information generating unit automatically generates the association information for an echo of detected fish has been described as an example, the form may be changed. A form in which the association information generating unit generates the association information for an echo of fish designated based on a user’s operation in detected fish may be employed.

[0106] (5) In the embodiment and the modified examples described above, although the form in which the association information generating unit 15 generates the association information associating the first fish echo with the second fish echo detected at one second timing before a first timing has been described as an example, the form may be changed, form in which the association information generating unit 15 generates the association information associating the first fish echo with the second fish echoes over a plurality of second timings detected at a plurality of second timings before a first timing may be employed.

[0107] In the case of this modified example, for example, as in the display example illustrated in FIG. 14, the association information may be displayed. FIG. 14 is a diagram illustrating this modified example and is a diagram schematically illustrating one example of a video displayed on the display screen of the display unit 4. In the display example illustrated in FIG. 14, a form in which the first fish echoes E5 and E6, the previous second fish echoes E5’ and E6’ detected at the previous second timing that is a second timing (as a past timing of the previous first timing), and the second fish echoes E5” and E6” before the previous second fish echoes E5’ and E6’ that are detected at the second timing before the previous second timing (as a past timing before the previous second timing) are displayed is illustrated as an example.

[0108] In this modified example, the correspondence relation identifying unit 17 identifies correspondence relations between each of the first fish echoes E5 and E6, the previous second fish echoes E5’ and E6’, and the second fish echoes E5” and E6” before the previous second fish echoes E5’ and E6’. Then, the association information generating unit 15 generates the association information associating each of the first fish echoes E5 and E6, the previous second fish echoes E5’ and E6’, and the second fish echoes E5” and E6” before the previous second fish echoes E5’ and E6’ of which the correspondence relations are identified by the correspondence relation identifying unit 17. For example, as the association information associating each of the first fish echoes E5 and E6, each of the previous second fish echoes E5’ and E6’, and each of the second fish echoes E5” and E6” before the previous second fish echoes E5’ and E6’, the association information generating unit 15 generates the information of the vectors sequentially connecting these. In other words, the association information generating unit 15 generates the information of the vectors sequentially connecting the first fish echo E5, the previous second fish echo E5’, and the second fish echo E5” before the previous second fish echo E5’and the information of the vectors sequentially connecting the first fish echo E6, the previous second fish echo E6’, and the second fish echo E6” before the previous second fish echo E6’. Then, the display control unit 16 generates the display video data used for displaying the first fish echoes E5 and E6 and the second fish echoes E5’, E5’”, E6’, and E6” on the display unit 4 together with the information of the vectors described above and outputs the generated display video data to the display unit 4. In this way, the display control unit 16 performs the controls of displaying the first fish echoes E5 and E6 and the second fish echoes E5’, E5,” E6’, and E6” on the display unit 4 together with the information of the vectors described above.

[0109] The display unit 4, as illustrated in FIG. 14 as an example, displays the information of the vectors as the association information between the second fish echoes E5’, E5,” E6’, and E6” and the first fish echoes E5 and E6 based on the controls of the display control unit 16. In other words, together with each of the second fish echoes E5” and E6,” each of the second fish echoes E5’ and E6’, and each of the first fish echoes E5 and E6, the association information images V5 and V6 as the information of the vectors respectively connecting those are displayed on the displayer 4. Here, the association information image V5 is a display of the vector connecting the second fish echo E5” of two-times before, the second fish echo E5’ of one-time before, and the first fish echo E5, and the association information image V6 is a display of the vector connecting the second fish echo E6” of two-times before, the second fish echo E6’ of one-time before, and the first fish echo E6.

[0110] As in this modified example, a form in which the association information associating the first fish echoes E5 and E6 and the second fish echoes E5’, E5,” E6’, and

E6” over a plurality of second timings detected at a plurality of second timings before the first timing are displayed on the displayer 4 may be employed.

[0111] The present invention can be broadly applied as an echo signal processing device, an echo signal processing system including an echo signal processing device, and an 5 echo signal processing method processing echo signals generated by a sonar sensor based on the reflected waves of the transmission waves transmitted into the water.

[0112] While preferred embodiments of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can 10 be made without departing from the scope of the present invention. Accordingly, the invention is not to be considered as being limited by the foregoing description, and is only limited by the scope of the appended claims.

Claims

1. An echo signal processing device (2), comprising:

a fish echo detecting unit (12) that detects echoes of fish from echo signals generated by a sonar sensor (3) based on reflected waves of transmission waves transmitted into the water;

a correspondence relation identifying unit (17) that identifies a correspondence relation between a first fish echo (El, E2, E3a, E3b, E4, E5, and E6) and a second fish echo (El’, E2’, E3’, E4’a, E4’b, E5’, E5”, E6’, and E6”), wherein the first fish echo is an echo of the fish detected at a first timing and the second fish echo is an echo of the fish detected at a second timing before the first timing; and an association information generating unit (15) that generates association information associating the first fish echo (El, E2, E3a, E3b, E4, E5, and E6) and the second fish echo (El’, E2’, E3’, E4’a, E4’b, E5’, E5”, E6’, and E6”) for which the correspondence relation has been identified with each other by the correspondence relation identifying unit (17).

2. The echo signal processing device (2) according to claim 1, further comprising:

a display control unit (16) that performs controls of displaying the echoes of the fish and the association information.

3. The echo signal processing device (2) according to claim 1 or 2, further comprising:

a ship position information acquiring unit (11) that acquires ship position information of a ship (S) where the sonar sensor (3) is mounted;

a fish centre relative coordinates calculating unit (13) that calculates relative coordinates of centres of the echoes of the fish with reference to the position of the ship (S) based on the echoes of the fish; and a fish centre absolute coordinates calculating unit (14) that calculates absolute coordinates of the centres of the echoes of the fish based on the ship position information and the relative coordinates of the centres of the echoes of the fish, wherein the association information generating unit (15) generates the association information based on the absolute coordinates of the centres of the echoes of the fish.

4. The echo signal processing device (2) according to any one of claims 1 to 3, wherein the correspondence relation identifying unit (17) associates the first fish echo (El, E2, E3a, E3b, E4, E5, and E6) with the second fish echo (El’, E2’, E3’, E4’a, E4’b, E5’, E5”, E6’, and E6”) when a centre of the first fish echo is present within a predetermined distance from a centre of the second fish echo (El’, E2’, E3’, E4’a, E4’b, E5’,E5”, E6’, and E6”).

5. The echo signal processing device (2) according to any one of claims 1 to 4, further comprising:

a display control unit (16) that performs controls of displaying the echoes of the fish and the association information, wherein the display control unit (16) performs controls of displaying the second fish echo (El’, E2’, E3’, E4’a, E4’b, E5’, E5”, E6’, and E6”) and the first fish echo (El, E2, E3a, E3b, E4, E5, and E6) together with the association information.

6. The echo signal processing device (2) according to any one of claims 1 to5, wherein the association information generating unit (15) generates information of vectors connecting the second fish echo (El’, E2’, E3’, E4’a, E4’b, E5’, E5”, E6’, and E6”) and the first fish echo (El, E2, E3a, E3b, E4, E5, and E6) as the association information.

7. The echo signal processing device (2) according to claim 6, further comprising:

a display control unit (16) that performs controls of displaying the echoes of the fish and the association information, wherein the display control unit (16) performs controls of displaying the vectors as segment displays.

8. The echo signal processing device (2) according to any one of claims 1 to 5, wherein the association information generating unit (15) generates information including numerical values of the vectors connecting the second fish echo (El’, E2’, E3’, E4’a, E4’b, E5’, E5”, E6’, and E6”) and the first fish echo (El, E2, E3a, E3b, E4, E5, and E6) as the association information.

9. The echo signal processing device (2) according to claim 8, wherein the information including the numerical values of the vectors includes orientations and speeds of the fish in a horizontal direction and orientations and speeds of the fish in a vertical direction.

10. The echo signal processing device (2) according to claim 8 or 9, further comprising:

a display control unit (16) that performs controls of displaying the echoes of the fish and the association information, wherein the display control unit (16) performs controls of displaying the information including the numerical values of the vectors.

11. The echo signal processing device (2) according to any one of claims 1 to 10, wherein, in a case that a plurality of the first fish echoes (El, E2, E3a, E3b, E4, E5, and E6) corresponds to the second fish echo (El’, E2’, E3’, E4’a, E4’b, E5’, E5”, E6’, and E6”), the association information generating unit (15) generates the association information associating the second fish echo (El’, E2’, E3’, E4’a, E4’b, E5’, E5”, E6’, and E6”) with the plurality of the first fish echoes (El, E2, E3a, E3b, E4, E5, and E6).

12. The echo signal processing device (2) according to any one of claims 1 to 11, wherein, in a case in which a plurality of the second fish echoes (El’, E2’, E3’, E4’a, E4’b, E5’, E5”, E6’, and E6”) corresponds to the first fish echo (El, E2, E3a, E3b, E4, E5, and E6), the association information generating unit (15) generates the association information associating the plurality of the second fish echoes (El’, E2’, E3’, E4’a, E4’b, E5’, E5”, E6’, and E6”) with the first fish echo (El, E2, E3a, E3b, E4, E5, and E6).

13. An echo signal processing system comprising:

a sonar sensor (3) that generates echo signals based on reflected waves of transmission waves transmitted into the water;

the echo signal processing device (2) according to any one of claims 1 to 12 that processes the echo signals; and a display unit (4) that displays an image based on data generated by the echo signal processing device (2).

14. An echo signal processing method comprising:

detecting echoes of fish from echo signals generated by a sonar sensor (3) based on reflected waves of transmission waves transmitted into the water;

identifying a correspondence relation between a first fish echo (El, E2, E3a, E3b,

E4, E5, and E6) and a second fish echo (El’, E2’, E3’, E4’a, E4’b, E5’, E5”, E6’, and

E6”), wherein the first fish echo is an echo of the fish detected at a first timing and the second fish echo (El’, E2’, E3’, E4’a, E4’b, E5’, E5”, E6’, and E6”) is an echo of the 5 fish detected at a second timing before the first timing; and generating association information associating the first fish echo (El, E2, E3a, E3b,

E4, E5, and E6) and the second fish echo (El’, E2’, E3’, E4’a, E4’b, E5’, E5”, E6’, and

E6”) for which a correspondence relation has been identified with each other.