Ship systems

Abstract

The present invention provides a ship system capable of preventing damage to one's own vessel from false GNSS signals when other vessels receiving false GNSS signals are present in the vicinity. [Solution] The ship system is characterized in that a first ship 2A and a second ship 2B are connected in a communicative manner, the first ship 2A is equipped with a positioning unit 212A of a GNSS compass 21A that measures its own position based on GNSS signals transmitted from multiple satellites, and an anomaly detection unit 211A of the GNSS compass 21A that detects anomalies in the GNSS signals, and the second ship 2B is able to acquire the position of the first ship 2A measured by the positioning unit 212A of the GNSS compass 21A, and is also able to acquire the fact that an anomaly has been detected by the anomaly detection unit 211A of the GNSS compass 21A.

Description

Technical Field

[0004] , , , ,

[0001] This invention relates to a ship system for reducing damage caused by false GNSS (Global Navigation Satellite System) signals.

Background Art

[0002] An electronic chart information display device (ECDIS: Electronic Chart Display and Information System) installed on a ship displays geographical information from a nautical electronic chart on a screen, and integrates and displays various information from a radar, an automatic identification system (AIS), a depth finder, and NAVigational TEleX (NAVigational TEleX) that mainly receives weather information. In addition, by having a function of outputting an alert when the own ship approaches another ship or approaches a shoal or a quay wall (for example, see Patent Document 1), the safety of navigation is enhanced.

[0003] On the other hand, in GNSS (Global Navigation Satellite System) such as GPS (Global Positioning System) that measures the position of a moving object using GNSS signals transmitted from artificial satellites, in recent years, false GNSS signals (hereinafter also referred to as abnormal signals) are transmitted from transmission sources such as artificial satellites and ground stations, and damage has occurred in which a GNSS receiver that has received this abnormal signal is caused to measure an incorrect position. In order to prevent such damage, technologies for determining whether the received GNSS signal is an abnormal signal (for example, see Patent Documents 2 and 3) and technologies for outputting an alarm message indicating that the received GNSS signal is an abnormal signal (for example, see Patent Document 4) have been developed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] Incidentally, if a GNSS receiver on a certain vessel X receives a false GNSS signal and calculates an incorrect position from that false GNSS signal, the AIS on vessel X will adopt the incorrect position calculated from that false GNSS signal as its own position and transmit it to other vessels as its own position information. In that case, vessels navigating around vessel X will see the incorrect position of vessel X, as well as the speed and course based on that incorrect position, displayed on their ECDIS, or the ECDIS may output a false collision warning based on the incorrect position of vessel X, thus hindering safe navigation. Therefore, as automation of ships through manpower reduction and remote control from land progresses, there is a need to develop a system that can mitigate the damage caused by false GNSS signals.

[0006] Therefore, the present invention aims to provide a ship system that can prevent damage caused by false GNSS signals when there are ships in the vicinity receiving false GNSS signals. [Means for solving the problem]

[0007] To solve the above problems, the invention described in claim 1 is a ship system characterized in that a first ship and a second ship are connected in a communicative manner, the first ship comprises a position measuring means for measuring its own position based on GNSS signals transmitted from a plurality of satellites, and anomaly detection means for detecting anomalies in the GNSS signals, and the second ship is capable of acquiring the position of the first ship measured by the position measuring means, and is also capable of acquiring the fact that an anomaly has been detected by the anomaly detection means.

[0008] The invention described in claim 2 is a ship system described in claim 1, wherein the second ship is equipped with a position information utilization calculation means that performs calculations using the position of the first ship measured by the position measuring means, and when it is determined that an abnormality has been detected in the first ship, the position information utilization calculation means invalidates the position of the first ship measured by the position measuring means, or proposes to the user that it be invalidated. [Effects of the Invention]

[0009] According to the invention of claim 1, the second vessel can be notified when an anomaly in the GNSS signal is detected on the first vessel, thereby preventing damage to its own vessel caused by false GNSS signals and improving navigational safety.

[0010] According to the invention of claim 2, the second vessel is configured in a position information utilization calculation means that performs calculations using the position of the first vessel, and it is suggested to the user that the erroneous position of the first vessel measured based on false GNSS signals be invalidated. This makes it possible to more reliably prevent damage caused by false GNSS signals from affecting the vessel itself and to improve navigational safety. [Brief explanation of the drawing]

[0011] [Figure 1] This is a block diagram showing the schematic configuration of a ship system according to an embodiment. [Figure 2]Figure 1 is a block diagram showing the schematic configuration of a GNSS compass. [Figure 3] Figure 1 is a flowchart showing the operation of the ship's system. [Figure 4] This is a schematic diagram illustrating the positional relationship between the first and second vessels as shown in the ECDIS in Figure 1. [Modes for carrying out the invention]

[0012] The present invention will be described below based on the illustrated embodiments.

[0013] Figure 1 is a block diagram showing the schematic configuration of a ship system 1 according to an embodiment of the present invention. The ship system 1 according to this embodiment mainly comprises a first ship 2A, a second ship 2B, and a land server 3. Here, the first ship 2A and the second ship 2B are connected to each other via AIS, which will be described later. Furthermore, the first ship 2A, the second ship 2B, and the land server 3 are connected to each other via a communication satellite 4 such as an Inmarsat® satellite.

[0014] The first vessel 2A is mainly equipped with a GNSS compass (position measurement means, anomaly detection means) 21A, an AIS 22A, and a control unit 23A, while the second vessel 2B is mainly equipped with an AIS 22B, a control unit 23B, and an ECDIS (position information utilization calculation means) 24B. The first vessel 2A may also be equipped with an ECDIS, and the second vessel 2B may also be equipped with a GNSS compass. Here, the AIS 22A of the first vessel 2A and the AIS 22B of the second vessel 2B are connected in a way that allows communication via international VHF (VHF radio waves), as will be described later. Components with the same number are, in principle, equipped with the same function and configuration, and the codes "A" and "B" following the number are used to distinguish whether the component belongs to the first vessel 2A or the second vessel 2B.

[0015] Figure 2 is a block diagram showing the schematic configuration of the GNSS compass 21A shown in Figure 1.

[0016] The GNSS compass 21A provided in the first ship 2A receives satellite signals / positioning signals (referred to as "GNSS signals") transmitted from each of a plurality of satellites used in GNSS (referred to as "GNSS satellites"), and has a function of detecting abnormalities in the GNSS signals, which are received signals in GNSS, and a function of calculating the position of the own ship, etc. It mainly includes a control unit, a GNSS antenna 213A, a GNSS receiver 214A, an abnormality detection unit (abnormality detection means) 211A, and a positioning unit (position measurement means) 212A. Each part constituting the GNSS compass 21A is connected so that signals can be transmitted and received via a bus and information can be transmitted to each other.

[0017] Examples of GNSS include GPS (abbreviation for Global Positioning System, Global Positioning Satellite; Global Positioning System), GLONASS (abbreviation for GLObal Navigation Satellite System), Galileo, and BDS (abbreviation for BeiDou navigation satellite System; Beidou satellite navigation system).

[0018] Each of the plurality of GNSS satellites transmits a GNSS signal including ephemeris, which is data indicating the current position of the GNSS satellite itself, as a radio wave. The GNSS signals transmitted from each of the plurality of GNSS satellites also include information indicating the time when the GNSS satellite transmitted the GNSS signal as a radio wave.

[0019] The control unit has a function of controlling the operations of each part constituting the GNSS compass 21A, and is configured as a device having a central processing unit (CPU: abbreviation for Central Processing Unit) that performs arithmetic processing involved in, for example, detecting abnormalities in GNSS signals and calculating the position of the GNSS compass 21A, etc.

[0020] The control unit also serves as a storage area for storing programs, various types of information, and data that the central processing unit (CPU) uses when performing arithmetic operations involved in detecting anomalies in GNSS signals and calculating the position of the GNSS compass 21A, etc., or as a working area for temporarily storing data, information, etc. generated when the central processing unit (CPU) performs the arithmetic operations. For example, it is configured as a device having at least one of a read-only memory device ROM (abbreviation for Read Only Memory), a read-write memory device RAM (abbreviation for Random Access Memory), and a hard disk.

[0021] The control unit controls the start, content, and end of the processing of each part constituting the GNSS compass 21A according to a control program by causing the central processing unit (CPU) to execute a program for controlling the operation of the GNSS compass 21A (referred to as the "control program").

[0022] The GNSS reception unit 214A is a device for receiving GNSS signals transmitted from a plurality of GNSS satellites S_i (where i is a unique number for each satellite for distinguishing the plurality of GNSS satellites from each other), and is composed of at least two GNSS receivers each having a GNSS antenna 213A. In this embodiment, the GNSS reception unit 214A is composed of three GNSS receivers 214AX, 214AY, and 214AZ. The GNSS receiver 214AX has a GNSS antenna 213AX, the GNSS receiver 214AY has a GNSS antenna 213AY, and the GNSS receiver 214AZ has a GNSS antenna 213AZ.

[0023] Each of the GNSS receivers 214AX, 214AY, and 214AZ receives the GNSS signals transmitted from each GNSS satellite S_i via the GNSS antennas 213AX, 213AY, and 213AZ, converts them into electrical signals (specifically, digital signals), and outputs them.

[0024] The GNSS signal is superimposed on a carrier wave and transmitted sequentially from the GNSS satellite S_i as radio waves (referred to as "GNSS radio waves"). Each GNSS receiver 214AX, 214AY, and 214AZ receives the GNSS radio waves, demodulates them, and extracts the GNSS signal. The GNSS signal is then output from the GNSS receiver unit 214A.

[0025] The anomaly detection unit 211A is a device for detecting anomalies in the GNSS signal output from the GNSS receiver unit 214A and outputting the detection result. In this embodiment, it detects anomalies in the GNSS signal on the first vessel.

[0026] The method for detecting abnormalities in the received signal in the abnormality detection unit 211A is not particularly limited, but may include, for example, a method of receiving GNSS signals transmitted from multiple GNSS satellites S_i via multiple GNSS antennas 213AX, 213AY, and 213AZ and determining whether the transmission time of the GNSS signal is normal based on a comparison of the transmission time of the GNSS signal contained in the GNSS signal with a predetermined reference transmission time (detection of transmission time abnormality); a method of determining whether the pseudo-distance ρ_i of the GNSS satellite S_i is normal based on a comparison of the pseudo-distance ρ_i of the GNSS satellite S_i that transmitted the GNSS signal with the pseudo-distance ρr of a predetermined reference satellite Sr (detection of pseudo-distance abnormality); or a method of determining whether the direction of arrival of the GNSS signal is normal based on an index representing the difference in paths from the GNSS satellite S_i that transmitted the GNSS signal to each of the multiple GNSS antennas 213AX, 213AY, and 213AZ (detection of path difference abnormality). Details of each of the above detection methods are described in Japanese Patent Application Publication No. 2023-155130 (Patent Document 3) by the present applicant.

[0027] The positioning unit 212A is a device for calculating and outputting positioning information based on the GNSS signal output from the GNSS receiving unit 214A, and in this embodiment, it measures the position of the first vessel. The positioning information calculated by the positioning unit 212A includes, for example, the position, bearing, and attitude of the vessel (e.g., rolling, pitching, rotation rate (ROT)). The calculation process of positioning information by the positioning unit 212A can be performed using well-known techniques, and this invention is not limited to specific items or methods, so a detailed explanation is omitted.

[0028] Here, if the positioning unit 212A uses a GNSS signal (a false GNSS signal) transmitted from a GNSS satellite S_i that is classified as abnormal for the calculation of positioning information, it is predicted that the position of the first vessel 2A output from the positioning unit 212A will indicate an incorrect position.

[0029] The AIS (Automatic Identification System) 22A and 22B are devices that use international VHF (VHF radio waves) to automatically identify the movements of ships. Their basic configuration is the same as existing AIS systems that are required to be installed on ships that meet certain standards under the SOLAS Convention (International Convention for the Safety of Life at Sea).

[0030] The AIS22B of the second vessel 2B is connected to the AIS22A of the first vessel 2A via international VHF (VHF radio waves) and receives information about the first vessel 2A from the AIS22A (specifically, information such as the vessel's identification number (MMSI number), name, position, course, speed, and destination, hereinafter also referred to as "AIS information"). The position information included in the AIS information of the first vessel 2A is the position of the first vessel 2A measured by the positioning unit 212A of the GNSS compass 21A installed on the first vessel 2A. In other words, the second vessel 2B can obtain the position of the first vessel 2A measured by the positioning unit 212A of the GNSS compass 21A via the AIS22A and AIS22B. Therefore, if the first vessel 2A receives a false GNSS signal, the position included in the AIS information of the first vessel 2A, as well as the course and speed calculated based on that position, are expected to be incorrect.

[0031] The position of the first vessel 2A, obtained by the second vessel 2B's AIS22B from the first vessel 2A's AIS22A, is displayed on the display unit 241B of the ECDIS24B (described later) and is also used in the calculation process for alarm output in the alarm output unit 242B.

[0032] The control unit 23A of the first vessel 2A is a device that primarily controls the GNSS compass 21A and the AIS 22A, and the control unit 23B of the second vessel 2B is a device that primarily controls the AIS 22B and the ECDIS 24B.

[0033] The ECDIS (Electronic Chart Display and Information System) 24B installed on the second vessel 2B integrates geographical information from nautical electronic charts, positional information such as the ship's position, bearing, and speed, and information from various devices installed on the ship, and displays it on a screen. It also has a function to output a warning when the ship approaches another ship or approaches a shoal or quay. Its basic configuration is the same as existing ECDIS that are required to be installed on ships that meet certain standards under the SOLAS Convention.

[0034] The ECDIS24B used in this embodiment is a device that performs calculations using the position of the first vessel 2A, and mainly comprises a display unit 241B and an alarm output unit 242B.

[0035] The display unit 241B is a device for displaying various information, and specifically, as shown in Figure 4, it displays the position of the second vessel 2B (own vessel) and the position of the first vessel 2A (other vessel). Here, the position of the second vessel 2B (own vessel) is the position obtained from AIS22B, and if the second vessel 2B is equipped with a GNSS compass, it may be the position measured by its positioning unit. The position of the first vessel 2A (other vessel) is the position of the first vessel 2A obtained by AIS22B from AIS22A, and is the position measured by the positioning unit 212A of the GNSS compass 21A of the first vessel 2A.

[0036] In other words, the display unit 241B of the ECDIS24B displays the position of the first vessel 2A measured by the positioning unit 212A of the GNSS compass 21A. Therefore, if the positioning unit 212A of the GNSS compass 21A calculates the position of the first vessel 2A based on a false GNSS signal, the display unit 241B of the ECDIS24B will display the incorrect position of the first vessel 2A (Figure 4, "AIS position of the first vessel 2A (incorrect)"). For this reason, as will be described later, if the second vessel 2B receives information via the land server 3 that an anomaly has been detected in the GNSS signal of the first vessel 2A, the AIS22B will receive the information of the first vessel 2A obtained from the AIS22A. The position of the first vessel 2A, which is at position A and measured by the positioning unit 212A of the GNSS compass 21A, is to be disabled on the display unit 241B (this is suggested to the user), that is, not to be displayed on the display unit 241B (this is suggested to the user). In this case, the second vessel 2B may also be configured not to display on the display unit 241B not only the position of the first vessel 2A, but also all other AIS information (speed, heading, etc.) related to the first vessel 2A obtained from the AIS 22A (this is suggested to the user).

[0037] The alarm output unit 242B is a device for outputting an alarm to warn of the risk of collision with a ship or the like. Specifically, it determines whether there is a risk of collision between the two ships based on the position of the second ship 2B (own ship) and the position of the first ship 2A (other ship), and outputs an alarm. Here, the position of the second ship 2B (own ship) is the position obtained from AIS22B, and may also be the position measured by the positioning unit of the GNSS compass if the second ship 2B is equipped with one. The position of the first ship 2A (other ship) is the position of the first ship 2A obtained by AIS22B from AIS22A, and is the position measured by the positioning unit 212A of the GNSS compass 21A of the first ship 2A.

[0038] In other words, the alarm output unit 242B of the ECDIS24B outputs an alarm using the position of the first vessel 2A measured by the positioning unit 212A of the GNSS compass 21A. Therefore, if the positioning unit 212A of the GNSS compass 21A calculates the position of the first vessel 2A based on a false GNSS signal, the determination of whether or not there is a risk of collision between the two vessels will be made based on the incorrect position of the first vessel 2A. As a result, there is a risk of false alarms being issued, as the system may determine that a collision is imminent even though the two vessels are not actually approaching each other (and therefore do not need to avoid it) (see Figure 4). Therefore, as will be described later, if the second vessel 2B receives information via the land server 3 that an anomaly has been detected in the GNSS signal of the first vessel 2A, it proposes to the user that the position of the first vessel 2A obtained by AIS 22B from AIS 22A, and the position of the first vessel 2A measured by the positioning unit 212A of the GNSS compass 21A, be invalidated in the alarm output determination process by the alarm output unit 242B, that is, that it will not be used in the collision prediction calculation. In this case, the alarm output unit 242B may also propose to the user that not only the position of the first vessel 2A, but also all other AIS information (speed, heading, etc.) related to the first vessel 2A obtained from AIS 22A be used in the collision prediction calculation.

[0039] The alarm output by the alarm output unit 242B may be displayed on the display unit 241B as a message or code, or it may be output as a sound such as a buzzer.

[0040] The land-based server 3 is a device that is communicatively connected to the first vessel 2A and the second vessel 2B via a communication satellite 4, and is installed in a land-based management computer or the like. The land-based server 3 receives various information uploaded from devices installed on the first vessel 2A and the second vessel 2B, and based on the received information, transmits necessary information to the devices installed on the first vessel 2A and the second vessel 2B, and performs management.

[0041] In this embodiment, the land-based server 3, in particular, when information indicating that an anomaly in the GNSS signal has been detected by the first vessel 2A is uploaded, uplinks this information to the communication satellite 4 along with the MMSI number of the first vessel 2A, enabling the second vessel 2B to downlink the MMSI number of the first vessel 2A and the information indicating that an anomaly in the GNSS signal has been detected by the first vessel 2A from the communication satellite 4. That is, the second vessel 2B can obtain, via the land-based server 3, that an anomaly in the GNSS signal has been detected by the anomaly detection unit 211A of the first vessel 2A. The land-based server 3 may directly uplink information to the communication satellite 4 and downlink information from the communication satellite 4, or it may do so via a maritime station (a radio station installed on land to communicate with vessels at sea) that is connected to the land-based server 3 via a public network.

[0042] Next, the operation and function of the ship system 1 of this embodiment will be explained based on Figure 3.

[0043] First, when the anomaly detection unit 211A of the GNSS compass 21A installed on the first vessel 2A detects an anomaly in the GNSS signal (step S1), the first vessel 2A uploads the information that "an anomaly in the GNSS signal has been detected" and its own MMSI number to the land server 3 via the communication satellite 4 (step S2). More specifically, step S2 is performed by the first vessel 2A uplinking the information that "an anomaly in the GNSS signal has been detected" and the MMSI number to the communication satellite 4, and the land server 3 downlinking them from the communication satellite 4. Alternatively, as a method of conveying the information that "an anomaly in the GNSS signal has been detected," for example, it may be agreed that the "anomaly signal detection flag" will be set to 1 if an anomaly in the GNSS signal is detected, and to 0 (zero) if no anomaly in the GNSS signal is detected, and the information will be conveyed by setting the "anomaly signal detection flag" to 1 when an anomaly in the GNSS signal is detected.

[0044] Next, the land-based server 3 uplinks information that the first vessel 2A has detected an anomaly in the GNSS signal (e.g., "anomaly signal detection flag" 1) and the MMSI number of the first vessel 2A to the communication satellite 4 (step S3), and the second vessel 2B downlinks them from the communication satellite 4 (step S4). In other words, the second vessel 2B downloads information that the first vessel 2A has detected an anomaly in the GNSS signal (e.g., "anomaly signal detection flag" 1) and the MMSI number of the first vessel 2A from the land-based server 3 via the communication satellite 4 (steps S3, S4). In this way, the second vessel 2B obtains the information that an anomaly in the GNSS signal has been detected on the first vessel 2A.

[0045] Meanwhile, the first vessel 2A measures its own position using the positioning unit 212A of the GNSS compass 21A (step S5). The position of the first vessel 2A measured here is based on the GNSS signal in which an anomaly was detected, so it is expected to show an incorrect position.

[0046] Next, the AIS22A of the first vessel 2A transmits the position of its vessel, as measured in this manner, to the AIS22B of the second vessel 2B via international VHF (VHF radio waves) (step S6). In other words, the second vessel 2B obtains the position of the first vessel 2A via the AIS22A and AIS22B (step S6).

[0047] Next, the second vessel 2B, based on the information about the first vessel 2A downloaded from the land server 3 (information indicating the detection of an anomaly in the GNSS signal), determines that the position of the first vessel 2A obtained by AIS22B is incorrect, and proposes to the user that the position of the first vessel 2A be disabled in ECDIS24B (step S7). Specifically, "disable" means that the display unit 241B of ECDIS24B does not display the incorrect position of the first vessel 2A, and that the alarm output unit 242B does not use the incorrect position of the first vessel 2A when determining the risk of collision between the first vessel 2A and the second vessel 2B. This reduces damage caused by false GNSS signals. The second vessel 2B may also disable (not display or use) all other AIS information (speed, heading, etc.) about the first vessel 2A obtained from AIS22A in ECDIS24B, in addition to the position of the first vessel 2A.

[0048] The second vessel 2B may resume using the AIS information for the first vessel 2A in ECDIS24B if it downloads information from the land server 3 via the communications satellite 4 that the first vessel 2A "does not detect any abnormalities in the GNSS signal" (for example, an "abnormal signal detection flag" of 0).

[0049] Furthermore, if the second vessel 2B downloads information from the land server 3 via the communication satellite 4 that the first vessel 2A has detected an anomaly in the GNSS signal (for example, "anomaly signal detection flag" 1), it may output a screen pop-up, buzzer, alert, etc., to notify the user that it may have received AIS information containing incorrect information about the first vessel 2A.

[0050] As explained above, according to the ship system 1 of this embodiment, the second ship 2B can be notified when an abnormality in the GNSS signal is detected by the first ship 2A, thereby preventing damage to its own ship due to false GNSS signals and improving navigational safety.

[0051] Furthermore, the second vessel 2B, in the display unit 241B and alarm output unit 242B of the ECDIS 24B which performs calculations using the position of the first vessel 2A, is configured not to display or use (or to suggest to the user) the incorrect position of the first vessel 2A measured based on false GNSS signals. This makes it possible to more reliably prevent damage caused by false GNSS signals from affecting the vessel itself and improve navigational safety.

[0052] Although embodiments of this invention have been described above, the specific configuration is not limited to the embodiments described above, and any design changes, etc., that do not depart from the gist of this invention are also included. For example, in the above embodiments, the positioning unit and anomaly detection unit of a GNSS compass are given as examples of the position measurement means and anomaly detection means, but the position measurement means and anomaly detection means are not limited to the positioning unit and anomaly detection unit of a GNSS compass. For example, a GNSS / inertial navigation system described in Patent Document 2 (Japanese Patent No. 4803862) by the applicant may be used, or the position measurement means and anomaly detection means may be provided in separate devices (for example, a GNSS receiver or navigation device built into an AIS may be used as the position measurement means, and the anomaly detection unit of a GNSS compass may be used as the anomaly detection means). Furthermore, in the above embodiments, ECDIS is given as an example of the position information utilization calculation means, but any device other than ECDIS may be used as long as it performs calculations using the position of the first ship measured based on the GNSS signal. Furthermore, although the above embodiment assumes two vessels, the first vessel 2A and the second vessel 2B, there may be three or more vessels. In that case, a vessel equipped with at least a positioning unit, an anomaly detection unit, AIS, and a control unit may be the first vessel 2A, and a vessel equipped with at least an AIS, a control unit, and ECDIS may be the second vessel 2B. Also, a vessel equipped with a positioning unit, an anomaly detection unit, AIS, a control unit, and ECDIS may be both the first vessel 2A and the second vessel 2B. [Explanation of Symbols]

[0053] 1. Ship Systems 2A First ship 2B The second ship 21A GNSS compass (position measurement means, anomaly detection means) 211A Anomaly detection unit (anomaly detection means) 212A Positioning unit (position measurement means) 213A GNSS antenna 214A GNSS receiver 22A, 22B AIS 23A, 23B Control Unit 24B ECDIS (location information calculation means) 241B Display section (calculation means using position information) 242B Alarm output section (calculation means using position information) 3. Land-based servers 4. Communications satellites

Claims

1. The first vessel and the second vessel are connected in a way that enables communication. The first vessel comprises a position measuring means for measuring its own position based on GNSS signals transmitted from multiple satellites, and an anomaly detection means for detecting anomalies in the GNSS signals. The second vessel is capable of acquiring the position of the first vessel measured by the position measuring means, and is also capable of acquiring information if an anomaly is detected by the anomaly detection means. A ship system characterized by the following features.

2. The aforementioned second vessel is The system includes a position information utilization calculation means that performs calculations using the position of the first vessel measured by the position measuring means, If the system receives information that the anomaly has been detected in the first vessel, the position information utilization calculation means will invalidate the position of the first vessel measured by the position measurement means, or will propose to the user that it be invalidated. The ship system according to claim 1.

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