JP7740679B2 - Echo sounding system - Google Patents

Description

The present invention relates to an echo sounding system that uses ultrasonic waves to measure the distance to the seabed, for example, and visualizes and displays information about the seabed, etc.

A fish finder is known as one type of underwater information visualization device. As shown in Figure 1, a fish finder emits ultrasonic waves into the water and displays reflected signals from underwater objects (such as fish or floating objects) and the seabed on a color LCD display or similar device. Patent Document 1 also describes a bottom sediment detection device that can detect a wide range of water depths and detect bottom sediments on the seabed.

As described in Patent Document 1, single-beam and multi-beam sounders are conventionally known as depth sounders for detecting shallowness and depth. As shown in Figure 1, a single-beam sounder transmits ultrasonic pulse signals directly downward from a transducer and receives the ultrasonic signals reflected from the seabed directly below, thereby obtaining water depth data at that point. A multi-beam sounder simultaneously transmits ultrasonic pulse signals within a predetermined angular range toward the seabed, forming multiple receiving beams with different detection directions within this predetermined angular range, thereby obtaining water depth data for each area of the seabed surface corresponding to the predetermined angular range. While single-beam sounding measures the seabed depth information directly below the transducer using a line, multi-beam sounding can measure detailed seabed topography across a surface.

In the multi-beam system, the width of the area (swath) that can be irradiated with multiple ultrasonic beams at one time, for example 256 beams, is called the swath width, and the angle between the beams at both ends is called the swath angle. For example, the swath angle is set in the range of 90° to 120°. Compared to the multi-beam system, the single-beam system has a larger beam irradiation angle, so the irradiation area on the target (hereinafter referred to as the footprint) is larger, and the width of this footprint is detected.

Multi-beam sounders require large hardware and software, making them expensive. On the other hand, single-beam sounders are inexpensive, but can only measure one point at a time, resulting in poor measurement efficiency and the ability to obtain only rough three-dimensional data on the seabed topography. Furthermore, conventional bathymetry requires both compensation for the motion of the observation vessel and compensation for tide levels. Motion compensation requires devices such as an acceleration sensor to detect motion.

Japanese Patent Application Laid-Open No. 2006-162294

In terms of cost, the single-beam method is more advantageous than the multi-beam method. However, although single-beam sounders are inexpensive, they can only measure one point at a time, making them less efficient at measuring, and they can only obtain three-dimensional data on rough seabed topography. Furthermore, conventional bathymetry requires both compensation for the motion of the observation vessel and for tide levels. Motion compensation requires devices such as an acceleration sensor to detect motion.

Therefore, the object of the present invention is to provide an acoustic depth sounding system that can generate seabed information comparable to that of a multi-beam depth sounder using a single beam system, and can simultaneously perform motion compensation and tide level compensation.

The present invention provides an echo sounding system having a first echo sounding device and a second echo sounding device provided on a ship,
Each of the first echo sounding device and the second echo sounding device comprises:
A plurality of receivers of a satellite positioning system arranged on an axis having an inclination at an installation angle with respect to a z-axis of a three-dimensional coordinate system;
and a single-beam depth sounder arranged on an axis, emitting an ultrasonic beam in the extension direction of the axis, receiving the ultrasonic waves reflected from the bottom of the water and returning, thereby measuring the distance to the bottom of the water;
The water depth at the water bottom position is measured by correcting the distance using the positioning results of each of the multiple receivers ;
This is an echo sounding system in which the installation angles of the first echo sounding device and the second echo sounding device are different from each other .

According to the present invention, a single-beam system can be used to generate seabed information comparable to that of a multi-beam sounder. Because it is a single-beam system, costs can be lower than with a multi-beam system. Furthermore, since motion correction and tide level correction can be performed simultaneously, the effort required for sounding can be significantly reduced. Note that the effects described here are not necessarily limited to those described herein, and any of the effects described in this specification may be used.

FIG. 1 is a schematic diagram used to explain the conventional multi-beam system and single-beam system. FIG. 2A is a schematic diagram showing measurement points acquired by the multi-beam method, and FIG. 2B is a schematic diagram showing measurement points acquired by the single-beam method. FIG. 3 is a schematic diagram used to explain the relationship between water depth and measurement position. Figure 4A is a schematic diagram showing measurement points obtained using the single-beam method, Figure 4B is a schematic diagram showing measurement points obtained using the single-beam staggered method, and Figure 4C is a schematic diagram showing water depth data formed by point cloud super-resolution. FIG. 5 is a block diagram showing the system configuration of the single beam staggered system. FIG. 6 is a schematic diagram showing a schematic configuration of a single beam staggered system. FIG. 7 is a schematic diagram showing the arrangement of two Michibiki receivers and a single-beam echo sounder transducer. FIG. 8 is a block diagram showing the system configuration of the single beam staggered system. FIG. 9 is a block diagram illustrating an example of the configuration of the transmitting/receiving unit. FIG. 10 is a schematic diagram used to explain the calculation of the water depth at the position where the beam of the depth sounder hits. FIG. 11 is a schematic diagram for explaining the positional relationship when the ship is tilted. FIG. 12 is a graph showing an example of observation data of vertical movement obtained by a Michibiki receiver. FIG. 13 is a schematic diagram used to explain a measurement method using the single beam staggered method. FIG. 14 is a schematic diagram used to explain a measurement example using the single-beam staggered method. FIG. 15 is a schematic diagram used to explain the relationship between the radiation angle and the measurement position. Figure 16A is a schematic diagram showing the measurement position when the depth sounder transducer is installed at an angle of 10°, and Figure 16B is a schematic diagram showing the swath width when the depth sounder transducer is installed at an angle of 15°. FIG. 17A is a schematic diagram showing a bathymetry operation using a multi-beam method, and FIG. 17B is a schematic diagram showing a bathymetry operation according to one embodiment of the present invention. FIG. 18 is a schematic diagram used to explain a measurement method according to one embodiment of the present invention. FIG. 19 is a schematic diagram showing measurement positions in another embodiment of the present invention in which depth sounder transducers are installed at an angle on both sides of an observation vessel. FIG. 20A is a schematic diagram showing a bathymetry operation using a multi-beam method, and FIG. 20B is a schematic diagram showing a bathymetry operation according to another embodiment of the present invention. FIG. 21 is a schematic diagram used to explain a measurement method according to another embodiment of the present invention.

Embodiments of the present invention are described below. Note that the embodiments described below are preferred specific examples of the present invention and are subject to various technically desirable limitations. However, the scope of the present invention is not limited to these embodiments unless otherwise specified in the following description to the effect that the present invention is limited.

Prior to explaining the present invention, a conventional bathymetry method will be described with reference to Figures 2A and 2B. Figure 2A shows a multi-beam bathymetry method. A ship sails in the direction indicated by the arrows, acquiring bathymetry data at multiple positions within the swath width. The positions where this water depth is measured are called measurement points. The footprint of the measurement points is smallest directly below the ship and becomes larger as it approaches both sides of the swath width. On the other hand, with the single-beam method, the measurement points follow the ship's wake, as shown in Figure 2B. The size of the footprint of the measurement points varies depending on the depth. With the single-beam method, the measurement points are linear, so in order to increase the density of measurement points in the direction perpendicular to the sailing direction, it is necessary to sail in a crisscross pattern, as indicated by the arrows.

Figure 3 shows the relationship between beam irradiation angle and irradiation range in the single beam system. As an example, if the water depth is 2000m, if the beam irradiation angle is 1°, the irradiation range will be approximately 35m, and if the beam irradiation angle is 5°, the irradiation range will be approximately 175m.

Figure 4A shows the trajectory of measurement points for the single-beam method, and Figure 4B shows the trajectory of measurement points for the single-beam staggered method. The single-beam staggered method, which will be described in detail later, involves a ship being equipped with multiple satellite positioning system receivers arranged in the z-axis direction of a three-dimensional coordinate system, and a single-beam depth sounder with depth sounder transducers arranged in the z-axis direction. The ship's tilt is determined from the discrepancy in the positioning results of the multiple receivers, and the tilt of the depth sounder beam from vertical downwards is corrected to measure the seabed depth in an oblique direction. The single-beam staggered method allows for an expanded measurement range compared to the single-beam method.

The bathymetry data of the original measurement points obtained using the single-beam staggered method is fed into a machine learning model, and noise removal and point cloud super-resolution are performed using machine learning, resulting in measurement points with higher resolution than the original, as shown in Figure 4C. In Figure 4C, X represents a measurement point obtained using the machine learning model. 3D data of the seafloor topography is generated using the bathymetry data of the measurement points shown in Figure 4C.

Figure 5 shows the configuration of a single-beam staggered sounding system. A single-beam staggered sounder is installed on a ship. Sounding data obtained by the ship's sounding is transmitted to a receiving server 202 via wireless communication, for example, a mobile communication network 201. The receiving server 202 is a program and computer for receiving sounding data from the ship. The original sounding data received by the receiving server 202 is stored in an original sounding database 203.

Using the bathymetry data stored in the original bathymetry database 208, artificial intelligence 204 performs machine learning, noise removal, and point cloud super-resolution processing. As a result of the processing in artificial intelligence 204, AI-corrected bathymetry data is obtained, and the AI-corrected bathymetry data is stored in database 205. A detailed bathymetry map automatic generation system 206 uses the corrected bathymetry data to create a detailed bathymetry map.

The created bathymetric map is stored on the web server 207. When a pre-registered user accesses the web server 207 using, for example, a smartphone 208, the web server 207 provides the user with the desired bathymetric map data. The web server 207 is a program and computer for providing users with bathymetric map data.

The following describes the single-beam staggered echo sounding device described above. As shown in Figures 6 and 7, this type of echo sounding device is an acoustic sounding device that includes two high-precision GNSS (Global Navigation Satellite System) receivers 101 and 102 and a single-beam echo sounder 110. GNSS is a general term for satellite positioning systems such as GPS (Global Positioning System) and QZSS (Quasi-Zenith Satellite System). Positioning systems using GNSS receivers (e.g., QZSS, hereafter referred to as "Michibiki receivers") 101 and 102 can perform extremely high-precision positioning compared to conventional positioning systems that use only GPS. Each Michibiki receiver acquires three-dimensional coordinate positioning data.

Two Michibiki receivers 101 and 102 are installed on the observation vessel 100, and each Michibiki receiver receives radio waves from multiple satellites (four or more, for example six), and determines its own position by simultaneously learning the distance from these satellites. The distance from a satellite is calculated from the time it takes for the radio waves emitted from the satellite to reach the receiver. Positioning radio waves are received from the satellite at a cycle of, for example, 1/20 of a second.

As shown in Figure 7, the Michibiki receivers 101 and 102 are placed a predetermined distance Δr1 apart in the z-axis direction (up and down). The z-axis corresponds to a direction perpendicular to the altitude reference plane (mean sea level of Tokyo Bay). At the same position as the Michibiki receivers 101 and 102, below their extension, a single-beam echo sounder transducer 110 is placed a predetermined distance Δr2 away from the Michibiki receiver 101. The echo sounder transducer 110 is attached, for example, to one side or the bottom of the observation vessel 100, to transmit ultrasonic transmission signals into the sea and receive ultrasonic reception signals reflected by the seabed. The ultrasonic waves are reflected by the seabed and scattered, returning towards the sea surface. An existing transducer can be used as the single-beam echo sounder transducer 110.

Figure 8 shows the configuration when the above-mentioned depth sounding device is mounted on a research vessel 100. Position data obtained by the Michibiki receiver 101 and position data obtained by the Michibiki receiver 102 are supplied to the depth data generation unit 112. A transmitter/receiver unit 111 is connected to the depth sounder transducer 110, and a transmission signal is supplied from the transmitter/receiver unit 111 to the ultrasonic transmitter of the depth sounder transducer 110, and a received signal from the ultrasonic receiver of the depth sounder transducer 110 is supplied to the transmitter/receiver unit 111. The transmitter/receiver unit 111 obtains depth data using a single-beam depth sounder.

The depth data calculated by the depth data generation unit 112 is supplied to the depth data processing unit 113. The two-dimensional or three-dimensional image data generated by the depth data processing unit 113 is supplied to the storage device 114 and display device 115. The display device 115 is a display device such as a color LCD, and displays a two-dimensional or three-dimensional image representing, for example, the shape of the seabed. As explained with reference to Figure 5, the depth data processing unit 113, storage device 114, and display device 115 do not need to be installed on the observation vessel 100, but can be installed at land-based facilities, and the depth data obtained by the depth data generation unit 112 is transmitted to the depth data processing unit 113 via wireless communication.

A timing signal indicating the timing at which the Michibiki receivers 101 and 102 receive position data is supplied to the transmitter/receiver 111, and the timing of receiving the position data and the timing of emitting the ultrasonic transmission signal from the depth sounder transducer 110 are synchronized between these Michibiki receivers 101 and 102. The timing signal of one of the Michibiki receivers 101 and 102 may be used for synchronization. Furthermore, delay times in signal processing may be corrected. In short, the timing at which the Michibiki receivers 101 and 102 acquire position data and the timing at which the depth sounder acquires water depth data are synchronized.

As an example, if the period T at which the Michibiki receivers 101 and 102 acquire position data is set to, say, 1/20 of a second = 0.05 seconds, then the depth sounder must also be able to obtain depth data at the period T. Conventional depth sounders transmit short pulses, which propagate through the ocean, and the echoes reflected from the seabed are displayed on the screen as a line for each transmission, with a color proportional to the magnitude of the reflected signal. Because the transmission period was such that the next transmission was made after the echo reflected from the seabed returned, it could not be shorter than the time obtained by dividing the round-trip distance to the seabed by the speed of sound in water. For example, at a seabed 150 meters deep, the transmission period could not be shorter than 0.2 seconds, which is the round-trip distance of 300 meters divided by the speed of sound in water, 1500 m/s.

In one embodiment, a depth sounding device that solves this problem and can transmit at a short period such as the aforementioned 0.05 seconds is used. Figure 9 shows an example configuration of the transmitter/receiver unit 111. The pulse generator 1 is supplied with a timing signal indicating the timing at which the Michibiki receivers 101 and 102 receive position data, and generates a transmission trigger pulse of a pulse signal with a fixed period synchronized with this timing signal.

A transmission trigger pulse is supplied to the transmission signal generator 2. The transmission signal generator 2 generates a pseudo-noise sequence signal, such as a Gold code, as a transmission pulse, and digitally modulates the transmission pulse using pulse modulation, such as BPSK (Binary Phase Shift Keying). The carrier frequency is set to a few kHz to a few hundred kHz.

The transmission signal generated by the transmission signal generator 2 is supplied to the transmitter 3, where it is amplified and processed. The output signal from the transmitter 3 is supplied to the wave transmitter of the depth sounder transducer 110. Ultrasonic waves are transmitted from the wave transmitter into the ocean. Echoes of the emitted underwater ultrasonic waves are received by the wave receiver of the depth sounder transducer 110.

Received wave data from the receiver of the depth sounder transducer 110 is supplied to the receiving amplifier 5, where it is amplified and processed before being supplied to the received signal processing unit 6. The received signal processing unit 6 performs correlation processing on the received signal using a pseudo-noise series signal. When the pseudo-noise series signals of the transmitted signal and the received signal match, a signal with a large value is generated. This large signal is the received signal that corresponds to the transmitted signal. The received signal processing unit 6 also performs processing such as A/D conversion of the water depth data obtained after the correlation processing.

As an example, in pulse modulation, one bit consists of four periods, and each period is digitized with eight samples. Therefore, if the Gold code has 127 bits, one received echo signal will be (127 x 4 x 8 = 4064 bits). Correlation is detected by matching this received signal with 127 Gold code replicas (each replica has 4064 bits). The output of the received signal processing unit 6 is supplied to the water depth data generation unit 112. A transmission trigger pulse is also supplied to the water depth data generation unit 112. Here, the period of the transmission signal (transmission pulse) can be set to (2D/Vu) or less, where Vu is the speed of sound waves in water and D is the distance to the measurement target.

The processing of the depth data generation unit 112 in the depth sounding device will be explained with reference to Figures 10 and 11. When the observation vessel 100 is not rocking at all, the Michibiki receivers 101 and 102 and the depth sounder transducer 110 are aligned on the z-axis, and the position data obtained by each of the Michibiki receivers 101 and 102 is identical. In this case, the depth data obtained by the depth sounder including the depth sounder transducer 110 accurately represents the depth to the seabed.

On the other hand, if the observation vessel 100 rolls due to waves or other factors, as shown in Figures 10 and 11, the observation vessel 100 tilts at an angle of θ, causing the echo from the depth sounder transducer 110 to be sent obliquely toward the seabed, and the echo from the seabed to be received along an oblique path. Therefore, in this case, the water depth data r obtained by the depth sounder including the depth sounder transducer 110 will differ from the accurate water depth D (m) to the seabed. However, with the single-beam staggered method, accurate water depth data can be obtained by performing correction processing using the position data acquired by the Michibiki receivers 101 and 102, as described below.

The position measured by the Michibiki receiver 101 is represented as P1 (x1, y1, z1), and the position measured by the Michibiki receiver 102 is represented as P2 (x2, y2, z2). The differences Δx and Δy between these positions are expressed by equations (1) and (2).

As shown in Figure 10, when the observation vessel 100 tilts, the sounder beam measures the seabed that is shifted by θ from the z-axis, rather than directly below the vessel (directly below the sounder transducer 110). Figure 11 shows the relative positions of the Michibiki receivers 101 and 102 and the sounder transducer 110 when the observation vessel 100 tilts by θ. The relationship between the true measurement depth D and the measurement position Pi (xi, yi, zi) at this time is expressed by equations (3), (4), and (5).

The tilt θ, angle φ, dx, and dy are expressed by the following equations (6), (7), (8), and (9).

Figure 12 also shows an example of the change in the z-axis component (altitude) of the position (coordinate) obtained by the Michibiki receiver 101 when the observation vessel 100 moves up and down. An altitude of 0 is the mean sea level of Tokyo Bay. The white circles in Figure 12 represent measurement points whose positions are obtained by the Michibiki receivers 101 and 102 and from which the water depth D can be calculated. The true water depth zi can be calculated by correcting the elevation value z1 obtained by the Michibiki receiver 101 and the water depth D calculated as described above as shown in equation (10). This correction makes it unnecessary to correct for the effects of the motion of the observation vessel 100 and fluctuations in tide level.

As mentioned above, by making the measurement interval (e.g., 1/20 seconds) of the Michibiki receivers 101 and 102 equal to and synchronizing the transmission interval of the single-beam depth sounder, the true water depth zi can be accurately determined.

Figure 13 shows an overview of the depth measurement operation using the single-beam staggered echo sounder described above, showing the trajectory of the position reached by the ultrasonic beam from the depth sounder transducer 110 mounted on the research vessel 100. As an example, when the water depth is 30 m, a swing of +/- 5° corresponds to a range of +/- 5.2 m on the seabed. Figure 14 shows an example of a 3D display of the seabed on the display device 115. The dotted line represents the trajectory of the research vessel 100. Differences in water depth are distinguishable by display color. Displays other than those shown in Figure 14 (such as displaying contour lines) are also possible. Note that the water depth that can be obtained is a discrete value, but corrected bathymetry data can be obtained by using machine learning to remove noise and perform point cloud super-resolution processing.

Using the single-beam staggered method described above, two Michibiki receivers and one single-beam echo sounder can be combined to simultaneously correct for motion and tide levels, creating an inexpensive pseudo-multi-beam echo sounder. For example, a wider survey area can be covered by using ten single-beam staggered echo sounders compared to the area that can be surveyed with one multi-beam echo sounder. Furthermore, by simultaneously correcting for motion and tide levels, the effort required for shallow depth surveys can be significantly reduced.

As mentioned above, the single-beam staggered method allows for the construction of a sounding device at a much lower cost than the multi-beam method, and allows the use of smaller survey vessels. However, the measurement range of the single-beam staggered method is wider than that of the single-beam method, but narrower than that of the multi-beam method. The present invention aims to improve this point.

In other words, in this invention, a ship is equipped with multiple receivers from a satellite positioning system aligned along an axis tilted relative to the z-axis of a three-dimensional coordinate system, and a single-beam depth sounder with a depth sounder transducer. Even when the ship's inclination is 0°, an ultrasonic beam is emitted along an axis tilted relative to the z-axis, and the ultrasonic waves that return after being reflected and scattered on the seabed are received. The ship's inclination is calculated from the discrepancy in the positioning results from the multiple receivers, and the inclination of the depth sounder transducer added to the inclination of the ship is used as a correction amount. The seabed depth is measured using this correction amount. In other words, in the above explanation of the single-beam staggered method, the angle θ is the sum of the inclination of the depth sounder transducer and the inclination of the ship.

In the following explanation, the direction in which ultrasound is emitted will be referred to as the radiation angle. A radiation angle of 0° indicates that the offset is 0 and the direction of ultrasound radiation is aligned with the z-axis. The degree of tilt of the depth sounder transducer will be referred to as the installation angle. In this invention, the depth sounder is installed so that the radiation angle of the ultrasonic beam emitted from the depth sounder transducer when the observation vessel is not tilted (i.e., θ = 0°) is offset from the z-axis by a specified angle.

Figure 15 shows the measurement positions when one depth sounder transducer is installed on the observation vessel 100 and the radiation angle is set to 0°, 10°, 20°, 30°, 45°, and 60°. Figure 15 shows the measurement positions when the water depth is set to 1.

As shown in Figure 16A, when a single echo sounder transducer is attached to one side or bottom of the observation vessel 100 with an installation angle (radiation angle) = 10°, the ultrasonic beam (direction angle = 5°) spreads over a range of (7.5° to 12.5°) when the observation vessel 100 is not tilted. If the water depth at the position of the observation vessel 100 is 1, a footprint with a diameter of (0.132 to 0.222) is formed at the arrival plane of the ultrasonic beam.

When the observation vessel 100 tilts, the sway angle is assumed to be approximately (5° to 8°). For example, when the sway angle is 8°, the radiation angle of the depth sounder transducer changes within a range of (2° to 18°). Therefore, by tilting the depth sounder transducer on the observation vessel at a specified installation angle, the measurement position can be expanded compared to when the depth sounder transducer is installed without tilting. Figure 16B shows the spread of the ultrasonic beam emitted, for example, when (sway angle = 5° and installation angle = 15°). In this example, if the water depth at the position of the observation vessel 100 is 1, a footprint with a diameter of (0.222 to 0.315) is formed at the arrival plane of the ultrasonic beam.

Figures 17A and 17B show schematic diagrams of measurement points during depth measurement using a conventional multi-beam depth sounder and a single-beam staggered depth sounder. Multi-beam depth sounders densely distribute measurement points (footprints) horizontally on both sides of the wake, each measuring half the water depth. These measurement points are acquired simultaneously. As mentioned above, if a single-beam staggered depth sounder transducer is installed tilted to one side of the ship, such as the starboard side (installation angle = 15°), the outermost position of the measurement range will be approximately one-third of the water depth. Therefore, as shown in Figure 17B, depth data can be acquired at measurement points up to one-third of the water depth on one side of the wake. Although Figure 17B shows a footprint of multiple measurement points horizontally, because it is a single beam, depth data can only be acquired at one measurement point. This is also true for Figures 18, 20, and 21, which will be described later. On the other hand, in the vertical direction, the ultrasonic transmission interval can be shortened, allowing for a denser measurement point density compared to the multi-beam method.

Furthermore, the observation vessel 100 traces a track as shown in Figure 18 to measure the depth. That is, the observation vessel 100 travels in a straight line on the sea surface from bottom to top of the figure, taking depth measurements while it travels a predetermined distance, then turns almost at a right angle to the right, and travels from top to bottom of the figure, tracing a track parallel to the previous track, taking depth measurements while it travels. The distance between the previous track and the current track is set to twice (1/3 of the water depth).

The observation vessel 100 sails from top to bottom, drawing a wake of the same length as the previous wake, then makes a sharp turn and draws the next wake (a wake going from bottom to top). After the observation vessel 100 makes the sharp turn, it sails from bottom to top while taking bathymetry. From then on, the observation vessel 100 sails in the same way, drawing a lattice-shaped wake. The observation vessel 100 makes sharp turns to minimize blank areas where there are no measurement points. In blank areas where there are no measurement points, water depth data can be generated using point cloud super-resolution.

In the embodiment described above, a depth sounder transducer is installed on one side of the observation vessel. In contrast, in another embodiment of the present invention, as shown in Figure 19, depth sounder transducers 110a and 110b are installed at an angle on both sides of the observation vessel 100. The installation angles of the depth sounder transducers 110a and 110b are approximately equal but in different directions (polarities). In Figure 19, the installation angle of the depth sounder transducer 110a is -10°, and the installation angle of the depth sounder transducer 110b is +10°. The example shown in Figure 19 shows the range that the depth sounder transducers 110a and 110b can measure when the observation vessel 100 is tilted. If the water depth is D, a measurement range of (0.728 x D) can be achieved.

Figures 20A and 20B show schematic diagrams of the distribution of measurement points during depth measurement using a conventional multi-beam depth sounding device and another embodiment of the present invention. With a multi-beam depth sounding device, measurement points (footprints) are densely distributed across a width of half the water depth in the horizontal direction on both sides of the wake. As mentioned above, if single-beam staggered depth sounder transducers are installed on both sides at an angle, for example (installation angle = 15°), the measurement range will be approximately one-third of the water depth. Therefore, as shown in Figure 20B, water depth data can be obtained at one measurement point within a measurement range of one-third of the water depth on both sides of the wake. Meanwhile, in the vertical direction, the ultrasonic transmission interval can be shortened, allowing for a denser density of measurement points compared to the multi-beam method.

Furthermore, Figure 21 shows an example of the track of a research vessel 100 when performing bathymetry measurements using another embodiment of the present invention. That is, the research vessel 100 sails in a straight line on the sea surface from bottom to top of the figure, taking depth measurements while doing so. In Figure 21, measurement points obtained on the port side of the research vessel 100 are omitted due to the limited drawing area. After sailing a predetermined distance, the research vessel 100 turns almost at a right angle to the right and sails from top to bottom of the figure, tracing a track parallel to the previous track, taking depth measurements while doing so. The distance between the previous track and the current track is twice the measurement range (1/3 of the water depth). Note that the measurement ranges may partially overlap.

When the observation vessel 100 sails from top to bottom and draws a track of the same length as the previous track, the observation vessel 100 turns left to draw the next track (a track going from bottom to top). In this case, since water depth data can be obtained from one of the measurement points on the port side in the track drawn from top to bottom, there is no need to make a sharp turn to draw the next track. Another advantage is that there are no blank areas where no measurement points exist.

Although the above provides a detailed description of an embodiment of the present invention, the present invention is not limited to the above-described embodiment, and various modifications based on the technical concept of the present invention are possible. For example, the configurations, methods, processes, shapes, materials, and values described in the above-described embodiment are merely examples, and different configurations, methods, processes, shapes, materials, and values may be used as necessary. For example, the present invention may be applied to a depth sounder in a bottom sediment detection device that detects seabed reflection intensity data and measures the seabed sediment. Furthermore, rather than arranging the two receivers on the z-axis of the three-dimensional coordinate system of the satellite positioning system, the two receivers may be arranged with a predetermined offset, or the depth sounder transducer may be arranged with a predetermined offset relative to the z-axis. Furthermore, a satellite positioning system other than the system described in the embodiment may be used, and three or more Michibiki receivers may be used.

101, 102: Michibiki receiver, 110: sounder transducer, 111: transmitter/receiver, 112: water depth data generator, 115: display device

Claims (5)

1. An echo sounding system having a first echo sounder and a second echo sounder mounted on a ship,
Each of the first echo sounding device and the second echo sounding device comprises:
A plurality of receivers of a satellite positioning system arranged on an axis having an inclination at an installation angle with respect to a z-axis of a three-dimensional coordinate system;
a single-beam depth sounder arranged on the axis, emitting an ultrasonic beam in the extension direction of the axis, receiving ultrasonic waves reflected from the bottom of the water and returning, and measuring the distance to the bottom of the water;
the water depth at the position of the water bottom is measured by correcting the distance using the positioning results of each of the plurality of receivers;
An echo sounding system, wherein the installation angles of the first echo sounding device and the second echo sounding device are different from each other. 2. The echo sounding system of claim 1 , wherein the installation angles between the first echo sounder and the second echo sounder are approximately equal in value but of different polarities. 3. The echo sounding system according to claim 1 , wherein the water depth is corrected using a position in the z-axis direction obtained by one of the plurality of receivers. The echo sounding system according to any one of claims 1 to 3 , wherein machine learning using artificial intelligence is performed on the measurement data to perform point cloud super-resolution processing. The single beam echo sounder is
a transmission signal generating unit having a pseudo-noise sequence generating circuit for generating a pseudo-noise sequence signal and a modulation circuit for modulating a carrier signal by the pseudo-noise sequence signal at a transmission timing to form a transmission signal;
a transmitting unit that transmits the transmission signal as an ultrasonic wave into water;
a receiving unit that receives echoes of ultrasonic waves;
a reception signal processing unit that performs correlation processing of the echo with the pseudo-noise sequence signal to determine the echo corresponding to the transmission signal,
5. The acoustic depth sounding system according to claim 1 , wherein the period of the transmission signal is equal to or less than (2D/Vu), where Vu is the speed of sound waves in water and D is the distance to the seabed.