Ship positioning system, ship positioning method, and ship positioning program

Abstract

Even in environments where GPS accuracy cannot be obtained within harbors, this system improves the positioning accuracy of vessels within harbors, contributing to safe navigation of ships. [Solution] The ship-side system comprises a plurality of first devices 1 installed in port P, whose own positions are identified, and a second device 2 installed on ship B. Based on the bidirectional transmission and reception times of information or signals between each of the plurality of first devices 1 and the second device 2, the distance between each of the plurality of first devices 1 and the second device 2 is calculated. Based on the calculated distance between each of the first devices 1 and the second device 2, and the position information of each of the first devices 1, the position of the second device 2 (ship B) is identified.

Description

Technical Field

[0001] The present invention relates to a ship positioning system, a ship positioning method, and a ship positioning program capable of identifying the position of a ship entering a port in real time.

Background Art

[0002] The current ship berthing operation in a port is carried out manually. The crew estimates the distance between the position of their own ship and the berthing position and relies on their intuition to approach the ship to the berthing position. Therefore, berthing operations under poor visibility conditions are difficult. Conventionally, a system has been developed that confirms the position of the own ship based on the position information obtained by GNSS (or GPS), which is the mainstream in the positioning of moving objects, and adjusts the propulsion force based on this position of the own ship to approach the shore (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the position information obtained by GNSS may have an error of several meters compared with the actual position information, and it is known that the accuracy is affected by weather (signal delay and scattering in the atmosphere, etc.) and sea conditions (reflection on the sea surface, etc.). Although it is possible to compensate for this depending on the skill and experience of the ship's officer, if the skill and experience of the ship's officer are not sufficient, the possibility of collisions between ships in the port and collisions between ships and port facilities increases. In addition, due to the influence of weather and sea currents, the ship may deviate significantly from the planned berthing position, and there is also a risk of losing the accurate berthing position. Therefore, there is a need for the development of technology that can accurately and in real time determine the current location in complex port environments. This invention has been made in view of the above circumstances, and its main objective is to provide a ship positioning system, a ship positioning method, and a ship positioning program that can improve the accuracy of ship positioning within harbors and contribute to the safe navigation of ships within harbors. [Means for solving the problem]

[0005] To achieve the above objectives, the ship positioning system according to the present invention is A ship positioning system that determines the position of a ship using a plurality of first devices installed in a port and whose own position is identified, and a second device installed on the ship, Distance calculation means for calculating the distance between each of the multiple first devices and the second device based on the bidirectional transmission and reception times of information or signals between each of the multiple first devices and the second device, A ship positioning means that identifies the position of the second device based on the distance between the first device and the second device calculated by the distance calculation means, and the position information of the first device. It is characterized by having [this feature].

[0006] Here, "its own position is identified" includes not only cases where the position of the first device itself is identified, but also cases where the location of the place where it is installed, the structure, etc., is identified. Furthermore, "its own position is identified" includes not only cases where the position of the first device is identified in advance, but also cases where it is identified afterward by some means. In addition, the identified position information of the first device may be stored in a readable format in its own memory, or it may be stored in a database in another storage device. The position information of the first device can be 2D since the vessel being positioned never leaves the sea surface. However, if it is necessary to determine the position of specific locations within the vessel, not just the vessel's position, then 3D position information may be used. Furthermore, the installation method of the first device is not particularly limited; it may be installed on the surface of equipment or buildings located in a port, or it may be embedded in the surface.

[0007] Installing the second device on a ship includes not only fixing the second device to a surface of the ship where radio waves can easily reach or inside the ship's cabin, but also attaching it to the ship's hull walls or the surface of devices installed on the ship, or incorporating it into the ship. Alternatively, it also includes having a crew member on board wear it or having a crew member carry it in their personal belongings. Furthermore, the second device may be replaced by a smartphone or computer on board by installing the application of this system on a smartphone or computer owned by a crew member.

[0008] Therefore, the distance calculation means calculates the distance between each of the multiple first devices and the second device installed on the ship, and the ship position identification means makes it possible to identify the position of the second device, i.e., the position of the ship, based on the distance between each of the multiple first devices and the second device, and the position information of each of the first devices.

[0009] Here, the distance calculation means is: The difference between the time on the first device's clock when it transmits information or signals and the time on the second device's clock when it receives the information or signals transmitted from the first device. The difference between the time on the second device's clock when it transmits information or signals and the time on the first device's clock when it receives the information or signals transmitted from the second device, Based on this, the propagation time of information or signals between the first device and the second device may be calculated, and the distance between the first device and the second device may be calculated based on this propagation time. In this way, by calculating the distance between the first and second devices based on the transmission and reception times of information or signals in both directions between the first and second devices, it becomes possible to accurately calculate the propagation time of information or signals between the first and second devices, even if time synchronization is not maintained between the first and second devices.

[0010] Using the ship positioning information obtained from the above system, the following system can be constructed. For example, it includes a port information database that stores map information and facility information for ports. A route determination means that determines the route from the position of the second device, identified by the ship position identification means, to a predetermined location in the port by referring to a port information database, A system may be constructed that further includes a ship guidance means for guiding a ship to the predetermined position according to a route determined by a route determination means.

[0011] With such a system, a vessel equipped with the second device will be guided from its current position to a predetermined position by the vessel guidance means based on the route determined by the route determination means. By designating the predetermined position as the berthing position, proper berthing navigation becomes possible.

[0012] Furthermore, this system may be applied to multiple vessels, using a vessel positioning means to identify the position information of multiple vessels entering and leaving a port, and a route determination means to determine a route so that the distance between vessels does not fall below a predetermined value. In this way, it becomes possible to safely navigate within a port while avoiding collisions between vessels. [Effects of the Invention]

[0013] As described above, according to the ship positioning system, ship positioning method, and ship positioning program of the present invention, the distance between each of the multiple first devices installed in a port and the second device installed on the ship is calculated based on the bidirectional transmission and reception times of information or signals between each of the multiple first devices installed in a port and the second device installed on the ship. From the calculated distance between each of the multiple first devices and the second device, and the position information of each first device, the position of the ship on which the second device is installed is determined. Therefore, even in environments where GPS accuracy cannot be obtained, it is possible to obtain the position of a ship in a port with high accuracy, and this can contribute to the safe navigation of ships in a port. [Brief explanation of the drawing]

[0014] [Figure 1] It is a diagram showing an installation example of a first device and a second device of a ship positioning system according to the present invention. [Figure 2] It is a diagram showing a configuration example of a ship positioning system according to the present invention. [Figure 3] It is a block diagram showing a configuration example of the first device. [Figure 4] It is a block diagram showing a configuration example of the second device. [Figure 5] It is a block diagram showing the configuration of the server device. [Figure 6] It is a flowchart showing distance calculation processing. [Figure 7] It is a flowchart showing position identification processing. [Figure 8] It is a flowchart showing an example of route setting processing for setting a route to a target point in the harbor using the ship position obtained by the position identification processing. [Figure 9] It is a flowchart showing an example of processing for controlling the ship speed using the ship position obtained by the position identification processing. [Figure 10] It is a flowchart showing an example of processing for controlling the ship azimuth using the ship position obtained by the position identification processing. [Figure 11] It is a flowchart showing an example of processing for coping with the influence of natural environmental factors using the ship position obtained by the position identification processing.

Embodiments for Carrying Out the Invention

[0015] Hereinafter, embodiments according to the present invention will be described while referring to the accompanying drawings.

[0016] In FIGS. 1 and 2, a ship positioning system S includes a first device 1 installed at intervals in a harbor P, a second device 2 installed on a ship B that has entered the harbor or is scheduled to enter the harbor, and a server device 3. The first device 1 is a fixed object located within the port area and port district, and is installed on port facilities or immovable natural objects (trees, rocks, etc.) in a location suitable for transmitting and receiving radio waves. The port facilities to which the first device is attached may be fixed facilities on land, such as lighthouses F1, port utility poles and port lighting equipment F2, radio towers F3, terminal buildings F4, and management offices F5, or fixed facilities on piers in the water (e.g., mooring posts and lighting fixtures) F6, etc. Alternatively, it may be a mounting pole or the like specifically provided for attaching the first device 1. This first device 1 may be fixed to the surface of the installation location or object by appropriate means such as screws, adhesive, or brackets, or it may be attached by embedding it in the installation location or object. Furthermore, each first device 1 needs to have its own two-dimensional or three-dimensional position information measured and identified (for ships, since the position information identifies the position while floating on the sea surface, two-dimensional position information is often sufficient). The location information (2D or 3D location information) of the first device 1 may be predetermined and stored readably inside the first device 1, or it may be determined retrospectively by some means after the system has been started. Furthermore, the location information of the first device 1 may be stored in a database in the storage unit (storage unit 33, described later) of the server device 3. Here, the location information may be expressed, for example, by latitude, longitude, and optionally ellipsoidal height in the WGS84 coordinate system, or it may be expressed by a unique two-dimensional or three-dimensional coordinate system established in the port area.

[0017] The first device 1 and the second device 2 can communicate directly with each other. Furthermore, the first device 1 can be connected to the server device 3 via the communication network 4, and the second device 2 can also be connected to the server device 3 via the communication network 4.

[0018] Each of the first device 1 and second device 2 has an internal clock, which can be synchronized to a reference time using a method described later. By synchronizing them, it is possible to obtain accurate positional information of multiple second devices at the same time.

[0019] Furthermore, the first device 1 can also function as the first device 1 for multiple second devices 2, and when multiple second devices 2 exist, each of these second devices 2 may be configured to function as the first device for multiple other second devices. In other words, if the precise location of a second device can be determined, the distance between that second device and other second devices can be calculated and used to determine the location of the other second devices. In this embodiment, we will describe a case where only the first device is used to locate the second device.

[0020] (Regarding the first device) As shown in Figure 3, the first device 1 comprises a control unit 11, an RF chip 12, and an oscillator 13, each connected by a bus. It also includes a RAM 14 and a storage unit 15, each connected to the control unit 11 by a bus.

[0021] The control unit 11 consists of a CPU and ROM, and executes programs stored in ROM to control the first device 1. The RF chip 12 is equipped with at least a clock 16, but may also be equipped with a phase detector. The RF chip 12 also has the function of processing the transmission and reception of wireless signals, and the data received by the RF chip 12 is subject to calculation processing by the control unit 11. The RAM 14 is the work area of ​​the control unit 11, and the storage unit 15 is a storage area for saving programs, data, etc.

[0022] The oscillator 13 oscillates at a predetermined frequency and outputs a signal to provide the operating timing for each part of the device. A crystal oscillator or an atomic oscillator can be used as the oscillator 13. The clock 16 keeps time using the output signal of the oscillator 13 as the source oscillation and outputs the time. The time kept by the clock 16 is controlled by the control unit 11 to be transmitted to the second device 2 via the RF chip 12. If a phase detector is also provided, it detects the phase of the carrier wave that constitutes the information received from the second device 2, and also detects the phase of the signal transmitted by the oscillator 13 of the first device 1.

[0023] The RF chip 12 is capable of sending and receiving data with other computer devices. Data received by the RF chip 12 is stored in the RAM 14 or storage unit 15 and is subject to calculation processing by the control unit 11. When the 3D position information of the first device 1 is received via the RF chip 12, it is stored in the RAM 14 or storage unit 15 and controlled by the control unit 11 to be transmitted to the second device 2 via the RF chip 12.

[0024] In this ship positioning system S, the installation location of the first device 1 is not particularly limited, but since it is used to determine the position of ships within a port, it is preferable to install it at the highest possible position in a port facility (a stationary facility located within the port area and port district) or natural object that offers a clear view of the entire port. The location should be appropriately selected depending on the conditions of the port facility using the ship positioning system S.

[0025] To obtain positional information of vessels within a harbor, the first device 1 does not need to be installed on the same plane, and adjacent first devices 1 may be installed at different heights. For example, even when the first device 1 is attached to harbor equipment, the mounting height of the first device may be varied for each piece of equipment, the mounting height of the first device 1 may be managed, and the mounting location of the first device 1 may be recognized as three-dimensional positional information.

[0026] Furthermore, it is desirable that the first device 1 be installed comprehensively within the harbor, and that it be appropriately arranged so that at least three of the first devices 1 can transmit and receive information between the second device 2 and the vessel, regardless of the vessel's position within the harbor.

[0027] Furthermore, the location information of the installation site of the first device 1 may be stored in its own storage unit 15 in association with identification information that can identify the first device 1, or it may be stored in the storage unit 33 of the server device 3 described later, or it may be available via the communication network 4 from another management server that manages location information.

[0028] (Regarding the second device) Next, the second device 2 will be described. This second device 2 is to be installed on all vessels that are docked in the harbor, and may be integrated with ship equipment, fixed to the surface of the ship by appropriate means, or embedded in the ship. Alternatively, the application of this system may be installed on a smartphone carried by a ship's crew member or on the ship's computer, and this smartphone or computer may be used as a substitute for the second device. The manner in which the second device 2 is installed may be by attaching it directly to the ship, or by attaching it to equipment, fixtures, accessories, or ancillary items that move with the ship.

[0029] As shown in Figure 4, the second device 2 comprises a control unit 21, an RF chip 22, and an oscillator 23, each connected by a bus. It also includes a RAM 24, a storage unit 25, and a display unit 27, each connected to the control unit 21 by a bus.

[0030] The RF chip 22 includes at least a clock 26, but may also include a phase detector if necessary.

[0031] The control unit 21 is configured with a CPU and ROM, and executes programs stored in the storage unit 25 to control the second device 2. The RAM 24 is the work area of ​​the control unit 21, and the storage unit 25 is a memory area for saving programs and data. The display unit 27 displays information such as the ship's position and route information to the target point, which will be described later, in a visually recognizable manner. The control unit 21 performs calculation processing based on programs and data read from the RAM 24 and storage unit 25, as well as data input from an input unit (not shown).

[0032] The RF chip 22 is capable of sending and receiving data with other computer devices. The data received by the RF chip 22 is loaded into the RAM 24 and subjected to calculation processing by the control unit 21.

[0033] The oscillator 23 oscillates at a predetermined frequency and outputs a signal to provide the operating timing for each part of the device. A crystal oscillator or an atomic oscillator can be used as the oscillator 23. The clock 26 keeps time using the output signal of the oscillator 23 as the source oscillation and outputs the time. The time kept by the clock is controlled by the control unit 21 to be transmitted to the first device 1 via the RF chip 22. If a phase detector is also present, it detects the phase of the carrier wave that constitutes the information received from the first device 1, and also detects the phase of the signal oscillated by the oscillator 23 of the second device 2.

[0034] (Regarding server equipment) Next, the server device 3 of the present invention will be described. The server device 3 can acquire location information from the second device 2.

[0035] The acquired location information is stored in server device 3 as the location information of the vessel (second device 2). The location information of the vessel (second device 2) is transmitted from second device 2 to server device 3, for example, by associating identification information that can identify second device 2 with the time the location information was determined. Server device 3 may also be able to communicate with first device 1 and second device 2 via smart meters installed in port facilities.

[0036] Figure 5 is a block diagram showing the configuration of a server device 3 according to an embodiment of the present invention. The server device 3 comprises at least a control unit 31, a RAM 32, a storage unit 33, and a communication interface 34, each connected by an internal bus. It also includes a database 35 for storing information received from the first device 1 and the second device 2. The location information of the first device 1 may also be stored in this database 35 after being compiled into the database.

[0037] The control unit 31 consists of a CPU, ROM, etc., and executes programs stored in the storage unit 33 to control the server device 3. The control unit 31 also has an internal timer for measuring time. The RAM 32 is the work area of ​​the control unit 31. The storage unit 33 is a storage area for saving programs and data. The control unit 31 reads programs and data from the storage unit 33 and RAM 32, and, based on information received from the first device 1 or the second device 2, executes various control processes in the control unit according to the program.

[0038] (Distance calculation process) Using the above configuration, the process for calculating the distance between the first device 1 and the second device 2 will now be described.

[0039] This distance calculation process calculates the distance between each of the first devices 1 and the second device 2, based on the propagation time Tp of the information or signal between each of the first devices 1 and the second device 2, provided that the first devices 1 and the second device 2 are within a distance range that allows them to mutually send and receive information or signals.

[0040] The distance calculation process is performed at predetermined time intervals (for example, every minute) or whenever predetermined conditions are met, and the process is carried out in steps S1 to S16 as shown in Figure 6. For convenience, here we will explain the case of calculating the distance between one first device 1 and one second device 2.

[0041] First, information or a signal is transmitted from the first device 1 to the second device 2 (step S1). The information or signal transmitted from the first device 1 to the second device 2 is not particularly limited.

[0042] In the first device 1, the time (T11) when information or a signal is transmitted in step S1 is recorded (step S2), and this recorded time is stored in the memory or storage unit 15 within the control unit 11 (step S3).

[0043] Subsequently, the second device 2 receives the information or signal from the first device 1 (step S4). The second device 2 records the time (T21) when the information or signal was received in step S4 (step S5). The recorded time (including the measured phase, if one is measured) is then stored in the memory or storage unit 25 of the control unit 21 (step S6).

[0044] Next, the second device 2 transmits information or a signal to the first device 1 (step S7). The information or signal transmitted from the second device 2 to the first device 1 is not particularly limited. The second device 2 records the time (T22) when the information or signal was transmitted in step S7 (step S8). Then, the recorded time is stored in the memory or storage unit 25 of the control unit 21 (step S9).

[0045] The first device 1 receives the information or signal transmitted in step S7 (step S10). The first device 1 records the time (T12) when it received the information or signal in step S10 (step S11). The recorded time (including the measured phase if the phase is measured) is then stored in the memory or storage unit 15 of the control unit 11 (step S12).

[0046] Subsequently, the first device 1 transmits to the second device 2 via its RF chip 12 the information stored in step S3 regarding the time (T11) when the signal was transmitted in step S1, and the information stored in step S12 regarding the time (T12) when the signal was received in step S10 (step S13). At this time, the position information of the first device 1 is also transmitted to the second device 2.

[0047] Then, in step S1, the second device 2 receives information regarding the time (T11) when the first device 1 transmitted information or a signal, and information regarding the time (T12) when the first device received information or a signal in step S10 (step S14).

[0048] Next, the distance between the first device 1 and the second device 2 is calculated using the second device 2 (step S15). This distance is calculated in the following manner.

[0049] Information regarding the time of the first device's clock (T11) is transmitted to the second device 2 via radio waves. The difference between this time and the time of the second device 2's clock (T21) when the second device 2 receives this information is recorded as ΔTa on the second device 2 side. In other words, if we define the time of the first device's clock when it transmits information or a signal from the first device 1 to the second device 2 as T11, and the time of the second device's clock when it receives the information or signal transmitted from the first device 1 and sets time as T21, and the difference between them as ΔTa, then this ΔTa (the difference in transmission and reception times when information or a signal is transmitted from the first device 1 to the second device 2) is the difference between the time of the first device 1's clock and the second device 2's clock (time difference: T20-T10) plus the propagation time (propagation delay) Tp, resulting in the relationship shown in Equation 1. This time difference (T20-T10) would be zero if the clocks of the first device 1 and the second device 2 were synchronized, but here we assume that a time difference (T20-T10) exists (they are not synchronized). [Formula 1] ΔTa=T21-T11=(T20-T10)+Tp

[0050] To determine this propagation time Tp, the second device 2 also sends information about the time of this clock (T22) to the first device 1, and the difference between this time and the time of the first device 1's clock (T12) when the first device 1 receives it is recorded as ΔTb on the first device side. That is, if we define the time of the second device's clock when the second device 2 transmits information or a signal to the first device 1 as T22, and the time of the first device 1's clock when it receives the information or signal transmitted from the second device 2 as T12, and the difference between them as ΔTb, then this ΔTb (the difference in transmission and reception times when the second device 2 transmits information or a signal to the first device 1) is the difference between the time of the first device 1's clock and the second device 2's clock (time difference: T10-T20) plus the propagation time (propagation delay) Tp, resulting in the relationship shown in Equation 2. Here, the time difference (T10-T20) would be zero if the clocks of the first device 1 and the second device 2 were synchronized, but here we assume that a time difference (T10-T20) exists (they are not synchronized). [Formula 2] ΔTb=T12−T22=(T10−T20)+Tp

[0051] The time differences between the two clocks, (T20-T10) and (T10-T20), are added when transmitting from the first device to the second device, and the same amount of time difference is subtracted when transmitting from the second device to the first device. Therefore, to find the propagation time Tp, we add equations 1 and 2, which cancels out the terms for the time differences (T20-T10) and (T10-T20), resulting in the relationship in equation 3. [Formula 3] Tp=(ΔTa+ΔTb) / 2 =((T21-T11)+(T12-T22)) / 2

[0052] Therefore, the propagation time Tp can be calculated based only on the time read by the clock of the first device 1 and the time read by the clock of the second device 2.

[0053] Incidentally, the time difference (T10-T20) between the clock of the first device 1 and the clock of the second device 2 is given by the relationship in Equation 4, obtained by [Equation 1] - [Equation 2]. [Formula 4] (T10-T20)=(ΔTa−ΔTb) / 2

[0054] Subsequently, the distance between the first device 1 and the second device 2 is calculated by multiplying the propagation time calculated using Equation 3 by the propagation speed of the information or signal (e.g., high speed) (step S15).

[0055] Then, the distance between the first device 1 and the second device 2 calculated in step S15 is stored in the memory or storage unit 25 of the control unit 21 (step S16). By executing step S16, the distance calculation process is completed.

[0056] Therefore, since equation (3) for calculating the propagation time Tp does not include a term for the time difference (time difference: T20-T10) between the clocks of the first device 1 and the second device 2, the propagation time for information or signals to propagate between the first device 1 and the second device 2 can be calculated regardless of whether there is a time difference between the clocks of the first device 1 and the second device 2 (independent of the time difference (time difference: T10-T20) between the clocks of the first device 1 and the second device 2).

[0057] [Location identification process] Next, we will explain the process for determining the position of the vessel to which the second device 2 is installed. This position determination process determines the position of the second device 2 based on the distances calculated in the distance calculation process between each of the multiple first devices 1 and the second device 2. Since the second device 2 is installed on a vessel, this can be said to be a process for determining the position of the vessel.

[0058] This positioning process should preferably be performed immediately after the distance calculation process is completed. Furthermore, in order to determine the position of the second device 2, it is assumed that the distance calculation device has calculated the distance to each of the multiple first devices 1 for each of the second devices 2.

[0059] In other words, when obtaining two-dimensional positional information of a vessel within a harbor (to obtain x and y coordinates), the position of the second device 2 can be determined by a well-known multi-point surveying calculation method based on the distance between one second device 2 and at least three first devices 1, and the positional information of each of the three first devices 1 used to calculate this distance. Therefore, since this system can determine the two-dimensional position of the second device 2 if three or more distance data points are available between the first device 1 and the second device 2, it is advisable to appropriately distribute the first devices so that the second device 2 can send and receive information or signals with at least three first devices 1 even if the second device 2 moves. In particular, in locations where positional accuracy is required, it is necessary to pre-adjust the number and two-dimensional position of the first device 1 to achieve the required accuracy.

[0060] Figure 7 shows a flowchart of the location identification process according to an embodiment of the present invention. This location identification process can be performed on any of the first device 1, second device 2, or server device 3. When the location identification process is performed on the first device 1 or server device 3, the distance between each of the multiple first devices 1 and the second device 2, as well as the location information of the first device 1, can be associated with the identification information of the second device 2, transmitted to the first device 1 or server device 3, and used. This section describes an example of performing location determination processing in the second device 2.

[0061] First, the position determination process requires that distance information for at least three different first devices 1 and second devices 2 be obtained at the same time or close together (when obtaining three-dimensional position information). Here, close together means that the time at which the distances of the three first devices 1 and second devices 2 used to determine the position of second device 2 are calculated is within a range that does not hinder the capture of the movement of second device 2. If the distances are not calculated at the same time or close together (for example, calculated when the time at which the propagation time of information or signals between each of the multiple first devices 1 and second device 2 is measured is the same time or close together), it becomes difficult to accurately determine the position of second device 2 (the ship) assuming that it is moving.

[0062] Therefore, first, it is determined whether or not three or more data points of the distance between the first device 1 and the second device 2 have been acquired within a predetermined time range (step S21).

[0063] If three or more distance data points between the first device 1 and the second device 2 are not obtained within a predetermined time range, accurate two-dimensional positional information cannot be obtained using this positioning method. Therefore, the system waits until three or more distance data points are obtained within the predetermined time range. In contrast, if three or more distance data points between the first device 1 and the second device 2 can be acquired within a predetermined time range, two-dimensional position information can be obtained with high accuracy using a position determination method that utilizes wireless bidirectional time comparison. Therefore, the current position of the second device 2 is determined using the multi-point surveying calculation method described above (step S22), and display processing is performed on the display unit 27, such as displaying the current position of the vessel (second device 2) (step 23). At the same time, the calculated position information of the vessel (second device 2) is stored in the storage unit 33 of the server device 3 along with the calculation time for use in subsequent processing.

[0064] Therefore, if there are three or more first devices 1 that can transmit and receive data from a second device 2 installed on a ship in the harbor, the two-dimensional position of the second device 2 is determined by a position determination process based on the distance between each first device 1 and the second device 2 calculated by the distance calculation process, and the position information of each first device 1 used in this distance calculation. As the ship on which the second device 2 is installed moves, the three first devices 1 that can calculate the distance are switched sequentially, making it possible to continuously capture the position of the second device 2 (the position of the ship). Thus, if there are three or more first devices 1 capable of calculating distance, the two-dimensional position of the second device 2 can be determined. By adjusting the locations where the first devices are attached and appropriately distributing them, the position of the displaced second device can be captured in real time.

[0065] In conventional methods for calculating propagation time based on the difference between the transmission time of a transmitter (corresponding to the first device) and the reception time of a receiver (corresponding to the second device), even if multiple transmitters are time-synchronized, the time synchronization between the transmitter and receiver is not maintained. Therefore, if there is a time difference between the two devices, the calculated propagation time will differ from the actual propagation time. In other words, if the receiver is different, the calculated propagation time may differ. In contrast, this system calculates the propagation time based on the transmission and reception times in both directions between the first device 1 and the second device 2, and then calculates the distance between the first device 1 and the second device 2. Therefore, even if there is a time difference between the first device 1 and the second device 2, there is no inconvenience in that the calculated propagation time will differ.

[0066] Furthermore, if the second device 2 installed on each vessel is not time-synchronized, the position information of all vessels in the harbor at a given time, recorded on the server side, will become inaccurate (a discrepancy will occur between the position known on the server side at a given time and the actual position at that time), potentially leading to the transmission of incorrect guidance or information to each vessel within the harbor. Also, considering that multiple vessels are navigating within the harbor, if the position information of vessels at the same time is inaccurate, setting a travel route based on this information would increase the risk of collisions between vessels. For this reason, in order to accurately determine the position of each vessel at the same time, both the first device 1 and the second device must be time-synchronized.

[0067] Therefore, by synchronizing the time of the second device 2 with the time of the first device 1 based on the time difference in equation (4), and by synchronizing the time of multiple first devices 1 and server devices 3 at predetermined timings, it becomes possible to synchronize the time of all devices (server device 3, first device 1, second device 2). This makes it possible to collect accurate positional information of all vessels in the harbor at the same time, and enables accurate positional tracking of each vessel on the server side.

[0068] Therefore, by using the above ship positioning system, even when accurate positional information obtained by GNSS cannot be obtained, or when positional accuracy is affected by weather conditions (signal delay or scattering in the atmospheric layer, etc.) or sea conditions (reflection on the sea surface, etc.), the precise position of a ship in a harbor can be determined. This prevents the loss of the ship's mooring position and allows for operations such as docking the ship at the designated location.

[0069] (Examples of using this system) Using the above ship positioning systems, it is possible to construct the following system. First, we will explain a system that uses this system to propose the optimal route to a destination within a port (for example, a target mooring position). In this system, in addition to the configuration shown in Figure 2, the server device 3 is further equipped with a port information database 40 (shown by the dashed line in Figure 5). The port information database 40 stores map information (such as the shape of the port and ship mooring locations) and facility information (such as the shape of the piers) within the port.

[0070] In order to set a route for a ship that has entered a port to its destination, such as a mooring location, using this port information database 40, the server device 3 performs the processing shown in Figure 8, for example. Specifically, server device 3 turns on the power to the second device 2 installed on ship B and determines whether the second device 2 is operational (step S31). If the second device 2 is not powered on and there is no request to obtain the ship's precise location information within the port, the system does not process and remains in standby mode. On the other hand, if there is a request to obtain the ship's precise location information within the port, the power to the second device 2 is turned on and the position of the second device 2 (ship B) is calculated using the process shown in Figures 6 and 7 (step S32). Then, a target location, such as a target berthing point, is set (step S33). This target location may be set in advance or entered each time. Alternatively, when the ship enters the port, the target location, such as a target berthing point, may be automatically obtained based on the port information database 40.

[0071] In response, the server device 3, having also acquired the location information of other vessels, checks whether there are any other vessels nearby (step 34). If there are no other vessels nearby, it refers to the facility information stored in the port information database 40 to generate the shortest route to the target point (target vessel point) (step 35), transmits the generated route to the second device 2, and displays the route on the display unit 27 of the second device 2 to guide the crew (step S36).

[0072] In response to this, if it is determined that another vessel is nearby, a route is generated that ensures a predetermined distance or greater from the other vessel, that is, a route that is safe (ensuring a predetermined distance or greater from the other vessel) and the shortest route to the target point is generated by referring to the facility information stored in the port information database 40 (step S37). This generated safe and shortest route is then displayed on the display unit 27 of the second device 2 to guide the crew (step S36). Based on that route information, the crew can either manually guide the vessel along the route, or the vessel can be set to automatically navigate along that route.

[0073] Therefore, with the above system, even in complex port environments where GPS-based positioning accuracy is insufficient, it becomes possible to collect accurate positional information of vessels within the port in real time. This makes it possible to accurately understand the movements of all vessels within the port and to provide them with the safest and shortest route to their target destination.

[0074] Furthermore, when automatically navigating to a target location, after the precise position of the vessel within the harbor has been calculated, the speed control of the vessel to the target location (target berthing point) may be automatically controlled as follows. Specifically, as shown in Figure 9, the distance between the current position obtained in step S22 and the target anchoring point is calculated, and the current speed of the vessel is confirmed (step S41). Here, the distance between the current position and the target anchoring point is not the straight-line distance, but the distance along the route generated in steps S35 and S37.

[0075] Then, the deceleration rate of the ship is calculated so that the ship's speed becomes zero at the target anchorage (step S42), and based on this calculated deceleration rate, the ship's propulsion system is instructed to decelerate (step S43).

[0076] Alternatively, the angle adjustment of a vessel heading towards its target anchorage may be carried out as follows: Specifically, as shown in Figure 10, the angle between the ship's current position and the target anchorage point (target angle) is calculated. This target angle can be determined, for example, by setting true north as zero degrees and calculating the angle from there. The ship's current direction of travel is also confirmed (step S51). Then, a correction angle is calculated to change the current direction of travel to the target angle (step S52), and based on this correction angle, the rudder of the ship is adjusted to correct the direction of travel (step S53).

[0077] Furthermore, the direction and speed of the vessel may be adjusted to take into account environmental factors such as wind and currents. Environmental factors such as wind and currents have a considerable influence on the direction and speed of a vessel. Therefore, The wind direction and speed, as well as the direction and speed of the ocean currents, are measured (step S61). If the wind is pushing the vessel in a certain direction, the rudder and speed are finely adjusted to move the vessel in the opposite direction to counteract the wind's effect. Similarly, if the ocean currents are altering the vessel's speed, the vessel's speed is finely adjusted to counteract the effect of the ocean currents (step S62).

[0078] Therefore, with the above system, accurate location information of vessels in a port can be collected in real time, regardless of port conditions or GPS accuracy degradation, making it possible to accurately navigate vessels to their target locations. Furthermore, each of the methods described above can also be provided in the form of a program for executing each step.

[0079] In the embodiments described above, we have explained how to safely dock and undock a self-propelled vessel while understanding its own position, orientation, distance, and speed. However, in the case of large vessels that dock and undock using a tugboat, the above system can be used to determine how and where the tugboat should push or pull the large vessel to ensure safe docking and undocking. In other words, it is possible to create a learning model that learns appropriate docking and undocking patterns by operating the tugboat, using the position, orientation, distance, and speed of the vessel obtained from the above system as input information. Using this learning model, it is possible to construct a system that determines an appropriate docking and undocking pattern from necessary information such as the position, orientation, distance, and speed of the large vessel, and issues instructions to the tugboat to obtain that pattern. In particular, in rural areas, the shortage of pilots for docking and undocking large ships is a serious problem. Therefore, the development of the above system can help solve this problem and can also be used to assist pilots. [Explanation of Symbols]

[0080] 1 1st device 2 Second device 3 Server equipment 40 Port Information Database S Ship positioning system P port B Ship

Claims

1. A ship positioning system that determines the position of a ship using a plurality of first devices installed in a port and whose own positions are identified, and a second device installed on the ship, Distance calculation means for calculating the distance between each of the multiple first devices and the second device based on the bidirectional transmission and reception times of information or signals between each of the multiple first devices and the second device, A ship positioning means that identifies the position of the second device based on the distance between each of the first and second devices calculated by the distance calculation means, and the position information of each of the first devices, A ship positioning system characterized by having the following features.

2. The aforementioned port is equipped with a port information database that stores map information and facility information of the port. A route determination means that determines a route from the position of the second device identified by the ship position identification means to a predetermined position in the port by referring to the port information database, A ship guidance means for guiding the ship to the predetermined position according to the route determined by the route determination means, The ship positioning system according to claim 1, further comprising the following:

3. The aforementioned vessel position identification means identifies the position information of multiple vessels entering and leaving the port, and the aforementioned route determination means determines the route such that the distance between vessels does not fall below a predetermined value. The ship positioning system according to claim 2, characterized in that it is the same as described in claim 2.

4. The distance calculation means is The difference between the time on the first device's clock when it transmits information or a signal and the time on the second device's clock when it receives the information or signal transmitted from the first device, The difference between the time on the second device's clock when it transmits information or a signal and the time on the first device's clock when it receives the information or signal transmitted from the second device. The ship positioning system according to claim 1, characterized in that it calculates the propagation time of the information or signal between the first device and the second device based on this propagation time, and calculates the distance between the first device and the second device based on this propagation time.

5. A ship positioning method for determining the position of a ship using a plurality of first devices installed in a port and whose own positions are identified, and a second device installed on the ship, A distance calculation step that calculates the distance between each of the multiple first devices and the second device based on the bidirectional transmission and reception times of information or signals between each of the multiple first devices and the second device, A ship position identification step that identifies the position of the second device based on the distance between each of the first and second devices calculated in the distance calculation step, and the position information of each of the first devices, A ship positioning method characterized by having the following features.

6. The aforementioned port is equipped with a port information database that stores map information and facility information of the port. A route determination step in which the position of the second device identified in the ship position identification step is used as the starting point to determine a route to a predetermined position in the port by referring to the port information database, A ship guidance step in which the ship is guided to the predetermined position according to the route determined in the route determination step, The ship positioning method according to claim 5, further comprising the following:

7. The ship position identification step identifies the position information of multiple ships entering and leaving the port, and the route determination step determines the route such that the distance between ships does not fall below a predetermined value. The ship positioning method according to claim 6, characterized in that it is the same as described in claim 6.

8. A ship positioning program used in a ship positioning system that determines the position of a ship using a plurality of first devices installed in a port and whose own positions are identified, and a second device installed on the ship, On the computer, Distance calculation means for calculating the distance between each of the multiple first devices and the second device based on the bidirectional transmission and reception times of information or signals between each of the multiple first devices and the second device, A ship positioning means that identifies the position of the second device based on the distance between each of the first and second devices calculated by the distance calculation means, and the position information of each of the first devices, A ship positioning program characterized by performing the following actions.

9. The aforementioned port is equipped with a port information database that stores map information and facility information of the port. To the aforementioned computer, A route determination means that determines a route from the position of the second device identified by the ship position identification means to a predetermined position in the port by referring to the port information database, A ship guidance means for guiding the ship to the predetermined position according to the route determined by the route determination means, The ship positioning program according to claim 8, characterized in that it further performs the following:

10. The aforementioned ship position identification means identifies the position information of multiple ships entering and leaving the port, The route determination means determines the route such that the distance between ships does not fall below a predetermined value. The ship positioning program according to claim 9, characterized in that it is a ship positioning program.

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