Sea area collision risk evaluation program by OZT and sea area collision risk evaluation system by ozt

Abstract

To evaluate an OZT blockage degree (BCOZT) between ships sailing in a sea area and a probability of evacuation failure based on AIS data.SOLUTION: A sea area collision risk evaluation program causes the computer to execute: an evaluation condition acquisition step of acquiring a sea area and an analysis period as evaluation conditions; an AIS data acquisition step of acquiring AIS data of a ship sailing in the sea area; an own ship data extraction step of defining one of a plurality of ships as the own ship and extracting own data from the AIS data; an other ship data extraction step of defining the other ships than the own ship among the plurality of ships as other ships encountered with the own ship and extracting other ship data from the AIS data; an OZT calculation step of performing an OZT calculation using a pair of the own ship and the other ship at the same time; a repeating step (loop 1, loop 2) of repeating the own ship data extraction step, the other ship data extraction step and the OZT calculation step by defining the other one of the plurality of ships as the next own ship, until the steps are completed for all ships encountered; and an OZT calculation result output step of outputting a result of the OZT calculation.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a marine collision risk assessment program using OZT and a marine collision risk assessment system using OZT. [Background technology]

[0002] A technique for appropriately indicating the risk of collision between moving objects is disclosed.

[0003] A collision warning device that warns of the possibility of collision between ships has been disclosed (Patent Document 1). Using information about the position and speed of other ships, the device calculates a collision risk, which indicates the risk of one ship colliding with another ship in the future, and displays ships that have a collision risk value indicating a predetermined risk or higher, and ships that do not.

[0004] Also, a vessel monitoring system that aims to improve the visibility of the Obstacle Zone by Target (OZT) has been disclosed (Patent Document 2). Based on the position and speed of the first vessel and the position and speed of the second vessel, the system calculates a risk value of collision between the first vessel and the second vessel when it is assumed that the first vessel will change course and reach each point on the predicted course of the second vessel, and displays an area where two or more consecutive points have a risk value above a threshold as a risk region.

[0005] Similarly, a technology for calculating the risk of collision between a first vessel and a second vessel has been disclosed (Patent Document 3). Furthermore, an algorithm for calculating the risk of collision between vessels from AIS (Automatic Identification System) data has been disclosed.

[0006] Also disclosed is a vessel collision prevention warning indicator that detects dangerous vessels, vessels that are potentially dangerous, or vessels that have not been tracked based on radar data, and transmits watch information regarding the type of warning and the position and matching status of dangerous vessels to the helmsman in a synthesized voice (Patent Document 4).Furthermore, a collision avoidance support device has been disclosed that presents the helmsman with predictive information necessary for collision avoidance decisions, and can support the helmsman in taking avoidance maneuvers based on quantitative judgments when there is sufficient time and space (Patent Document 5). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Patent Application Publication No. WO2020 / 003856 Pamphlet [Patent Document 2] International Patent Application Publication No. WO2022 / 085355 Brochure [Patent Document 3] Special table 2018 / 193596 publication [Patent Document 4] Japanese Patent Application Publication No. 07-129872 [Patent Document 5] Japanese Patent Application Publication No. 09-022500 Summary of the Invention [Problem to be solved by the invention]

[0008] There are two ways to estimate the potential collision risk of ships and other objects: a probabilistic approach, which calculates the number, position, and speed of a group of objects, and a deterministic approach, which determines the possibility of collision from the encounter of individual ships. The latter uses various indicators, including OZT, to assess the safety of marine areas. However, there are currently no methods for assessing the probability of failure to avoid collisions or the risk of collision.

[0009] The present invention uses OZT to estimate the probability of a ship navigating in the sea area failing to avoid a collision. The purpose is to properly assess collision risk. [Means for solving the problem]

[0010] One aspect of the present invention is a marine collision risk assessment program that evaluates the collision risk in a marine area where multiple ships are navigating due to an obstruction to navigation zone (OZT), and is characterized by having a computer execute the following steps: an evaluation condition acquisition step that acquires the marine area and an analysis period as evaluation conditions; an AIS data acquisition step that acquires AIS data of the ships navigating the marine area; an own ship data extraction step that defines one of the multiple ships as the own ship and extracts own ship data from the AIS data; an other ship data extraction step that defines other ships of the multiple ships other than the own ship as other ships that the own ship will encounter and extracts other ship data from the AIS data; an OZT calculation step that performs an OZT calculation for the own ship and the other ships at the same time as a pair; a own ship data extraction step that defines another one of the multiple ships as the next own ship; the other ship data extraction step; a repeat step that repeats the OZT calculation step until it is completed for all encountered ships; and an OZT calculation result output step that outputs the results of the OZT calculation.

[0011] Here, when performing the OZT calculation in the OZT calculation step, it is preferable to use a minimum safe passing distance defined by a pre-acquired calculation interval, information about the own ship and the other ship and the distance between the two ships, and a pre-acquired fixed value or a variable distance calculated from the information about the own ship and the other ship.

[0012] It is also preferable to obtain track data for each of the ships based on the acquired AIS data, and use the synchronized track data as the AIS data at any time.

[0013] In addition, it is preferable that the OZT calculation for the pair of the own ship and the other ship in the OZT calculation step is repeated for each other ship that encounters the own ship until the calculation is completed for all other ships that are encountered.

[0014] It is also preferable to further execute an OZT data acquisition step for acquiring OZT data for any of the own ships from the results of the OZT calculation output in the OZT calculation result output step, a time-specific OZT data extraction step for sorting the OZT data in chronological order and extracting all OZT data by time, a lattice ID acquisition step for acquiring the lattice ID in which the OZT is located, an OZT blockage degree calculation step for calculating the OZT blockage degree for each lattice ID by time using track data synchronized with hull information including the captain of the own ship, an OZT blockage degree accumulation step for accumulating the OZT blockage degree to the lattice ID, a repeat step for repeating the OZT data acquisition step, the time-specific OZT data extraction step, the lattice ID acquisition step, the OZT blockage degree calculation step, and the OZT blockage degree accumulation step until they are completed for all of the ships, and an evaluation result output step for outputting the accumulated result of the OZT blockage degree as a collision risk assessment result.

[0015] Furthermore, in the repeating step, it is preferable to repeat the lattice ID acquisition step, the OZT blockage degree calculation step, and the OZT blockage degree accumulation step sequentially for all of the time-based OZT data extracted in the time-based OZT data extraction step.

[0016] It is also preferable to execute an evaluation result visualization step of visualizing and displaying the outputted collision risk evaluation result.

[0017] It is also preferable to plan an optimal route for the ship based on the collision risk assessment result obtained in the assessment result output step.

[0018] Furthermore, it is preferable to obtain OZT data for any own ship from the output results of the OZT calculation, extract the OZT data by time, calculate the area of ​​any OZT from the OZT data, link the any OZT to a grid ID, and then repeatedly calculate for all ships to obtain and output an OZT area file, while also repeatedly calculating for all ships the OZT blockage degree (probability of failing to avoid collision) for all OZTs caused by a group of ships encountered by the any own ship, and obtain and output an OZT blockage degree file.

[0019] It is also preferable to repeatedly perform the area calculation and the OZT blockage degree calculation for all of the extracted time-based OZT data in sequence.

[0020] It is also preferable to obtain arbitrary time data and arbitrary own ship data from the output OZT area file and OZT blockage degree file, extract the areas of all the OZTs in an arbitrary mesh in which the OZT with the group of ships encountered by the arbitrary own ship is located, sum them up, and take the reciprocal to determine the variable term of the number of potential OZT collisions, obtain the probability of avoidance failure based on the OZT blockage degree of the arbitrary own ship data, and repeatedly estimate the variable term of the number of collisions with the OZT with the group of ships encountered by the own ship, which is calculated by multiplying the variable term of the potential OZT collisions by the probability of avoidance failure, for all meshes of the own ship, and further repeat this for all the own ship to accumulate the variable term of the number of collisions in the mesh in which the OZT is located.

[0021] It is also preferable to repeat the acquisition of the arbitrary time data for all times and the acquisition of the arbitrary own ship data for all ships.

[0022] Furthermore, it is preferable to obtain the number of collisions per unit time and unit area by dividing the variable term of the number of collisions in the mesh in which the OZT exists by the OZT calculation interval, and further obtain and output the number of collisions in the mesh during the evaluation time by integrating the area of ​​the grid in which the OZT exists and the evaluation time that have been calculated in advance.

[0023] It is also preferable to visualize and display the output collision count results.

[0024] Another aspect of the present invention is a system for evaluating a risk of a maritime collision using an OZT, comprising a computer, an input means, and an output means, and causing the computer to execute the above-mentioned program for evaluating a risk of a maritime collision using an OZT.

[0025] Here, it is preferable that the computer, the input means, and the output means are connected via an information communication network. [Effects of the Invention]

[0026] According to the present invention, the OZT blockage degree (BCOZT) and the probability of collision avoidance failure that may occur to a ship navigating in a sea area can be estimated using OZT, and the collision risk can be appropriately evaluated. Furthermore, the optimal route can be determined based on the estimated OZT blockage degree (BCOZT) and the probability of collision avoidance failure. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a diagram showing a configuration of a maritime collision risk assessment system according to an embodiment of the present invention. [Figure 2] 1 is a diagram showing a configuration of a marine collision risk assessment device according to an embodiment of the present invention. [Figure 3] 1 is a flowchart showing a method for calculating the OZT between ships in an embodiment of the present invention. [Figure 4] 1 is a flowchart showing a method for evaluating the OZT blockage degree (BCOZT) and the probability of collision avoidance failure in an embodiment of the present invention. [Figure 5] FIG. 1 is a diagram illustrating a method for calculating OZT. [Figure 6] 10 is a flowchart showing a method for assessing a risk of a maritime collision according to another embodiment of the present invention (parameter calculation steps). [Figure 7] 10 is a flowchart showing a method for assessing a risk of a marine collision according to another embodiment of the present invention (calculation step of the frequency of collisions). [Figure 8] A diagram showing the calculation flow of the evaluation area file shown in Figure 7. [Figure 9] Diagram showing the flow of visualizing the results DETAILED DESCRIPTION OF THE INVENTION

[0028] 1, a maritime collision risk assessment system 100 according to an embodiment of the present invention includes a maritime collision risk assessment device 102 configured from a computer, computers (102a to 102c) of companies A to C, and an information and communications network 104. The computers (102a to 102c) of companies A to C are connected to the maritime collision risk assessment device 102 at the center via the information and communications network 104.

[0029] In Figure 1, the maritime collision risk assessment device 102 is located at the center, and the computers (102a to 102c) of companies A to C are connected to their respective input means and output means, and play a role in accepting input from users via the input means and outputting evaluation results to the output means, as well as exchanging information with the maritime collision risk assessment device 102 at the center.

[0030] The marine collision risk assessment device 102 calculates the OZT (Obstacle Zone by Target) and estimates and assesses the potential collision risk and the frequency of collisions that ships navigating in the sea area may have based on the OZT. The OZT is information that indicates the space within the ship's activity space that is obstructed by the presence and movement of other ships, i.e., the obstruction zone caused by other ships.

[0031] The maritime collision risk assessment device 102 can be configured by a general computer. As shown in FIG. 2, the maritime collision risk assessment device 102 includes a processing unit 10, a storage unit 12, an input unit 14, and an output unit 16.

[0032] The processing unit 10 includes a means for performing arithmetic processing, such as a CPU. The processing unit 10 executes a maritime collision risk assessment program stored in the memory unit 12 to implement the maritime collision risk assessment process of this embodiment. The memory unit 12 includes storage means, such as a semiconductor memory and a hard disk. The memory unit 12 is accessible to the processing unit 10 and stores data used in the maritime collision risk assessment process, such as the maritime collision risk assessment program and AIS data acquired from an external device. The input unit 14 includes a means for inputting information to the maritime collision risk assessment device 102. The input unit 14 includes, for example, a touch panel or a keyboard for receiving input from a user. The input unit 14 also includes, for example, a network interface for receiving information from outside the maritime collision risk assessment device 102, and receives the maritime collision risk assessment program and data used in the maritime collision risk assessment process. The output unit 16 includes a means for displaying and transmitting information processed by the maritime collision risk assessment device 102. The output unit 16 includes, for example, a display. The input / output unit 44 also includes a network interface or the like for transmitting and receiving information between the maritime collision risk assessment device 102 and the outside, and transmits information processed by the maritime collision risk assessment device 102 to external devices (computers 102a, 102b, 102c), and receives input information from external devices (computers 102a, 102b, 102c). The input unit 14 and the output unit 16 can be included in the maritime collision risk assessment device 102 or can be provided externally.

[0033] The maritime collision risk assessment program may not be stored in the memory unit 12 but may be stored in a storage such as the cloud and shared by multiple computers to function as multiple maritime collision risk assessment devices 102. For example, data required for processing may be sent and received via the information and communications network 104 using a network interface included in the input / output unit 44, and processing may be performed by an application that executes the maritime collision risk assessment program on the web. This eliminates the need to update the maritime collision risk assessment program in each of the multiple computers (maritime collision risk assessment devices 102), and allows potential collision risks to be analyzed using the latest methods at all times.

[0034] Furthermore, the AIS data may be stored in a storage such as a cloud and shared among multiple computers (maritime collision risk assessment devices 102) instead of being stored in the memory unit 12. In this case, the AIS data may be acquired via the information communication network 104 using a network interface included in the input / output unit 44. This allows the potential collision risk to be calculated arbitrarily in each of the multiple computers (maritime collision risk assessment devices 102).

[0035] Of course, both the marine collision risk assessment program and the AIS data may be stored in a storage such as a cloud and shared among multiple computers (marine collision risk assessment devices 102).

[0036] 1, the maritime collision risk assessment device 102 functions as an evaluation condition acquisition unit 20, an AIS data acquisition unit 22, an own ship data extraction unit 24, an other ship data extraction unit 26, an OZT calculation unit 28, a repeating unit 30, an OZT data acquisition unit 32, a time-based OZT data extraction unit 34, a grid ID acquisition unit 36, an OZT blockage degree calculation unit 38, an OZT blockage degree accumulation unit 40, a repeating unit 42, and an input / output unit 44. The maritime collision risk assessment device 102 also functions as an optimal route planning unit 46 and an assessment result visualization unit 48.

[0037] The computer may be a standalone type, with input and output handled by the computer, and a marine collision risk assessment program may be used to perform a marine collision risk assessment, or only AIS data may be acquired via the information and communications network 104. The marine collision risk assessment device 102 may also be configured such that the functions of each part are realized by combining multiple computers, or that some parts are configured with hardware circuits.

[0038] Figures 3 and 4 are flowcharts showing a maritime collision risk assessment method in an embodiment of the present invention. Hereinafter, the maritime collision risk assessment method in the maritime collision risk assessment system 100 will be described with reference to the flowcharts of Figures 3 and 4. The maritime collision risk assessment method is realized by executing a maritime collision risk assessment program in the maritime collision risk assessment device 102. First, a method for calculating the OZT between ships will be described with reference to the flowchart of Figure 3.

[0039] 3 shows a method for calculating the OZT for all ships in the sea area to be evaluated. In step S10, a process is performed to acquire data from an Automatic Identification System (AIS). Through the process in this step, the maritime collision risk assessment device 102 functions as an AIS data acquisition unit 22. The maritime collision risk assessment device 102 acquires the AIS data through the input unit 14 using the function of the input / output unit 44.

[0040] AIS is a system that automatically transmits and receives information on ship identification, type, position, course, speed, navigation status, and other safety information over VHF radio waves, enabling information exchange between ship stations and between ship stations and land-based navigation aids. By establishing AIS-related facilities (AIS transmitting and receiving stations and operating organizations) along the coast, navigation-related information such as static information (e.g., ship name, length), dynamic information (e.g., position, speed), destination port, and estimated time of arrival of AIS-equipped ships can be obtained in real time. In congested waters, AIS primarily provides smooth navigation control and effective information provision for ships navigating in and around sea routes. In coastal waters, it can also warn ships at risk of running aground or dragging anchor in rough weather. It can also provide various navigation safety information, such as marine accident information and weather and oceanographic information, to AIS-equipped ships.

[0041] In step S12, analysis conditions for the AIS data are acquired. Through the processing in this step, the marine collision risk assessment device 102 functions as the assessment condition acquisition unit 20. In the marine collision risk assessment device 102, the marine area to be assessed and the analysis period to be assessed are acquired by the function of the input / output unit 44 via the input unit 14. The analysis period for assessing the potential collision risk is not particularly limited, but can be, for example, one day. The marine area to be assessed is a marine area in which multiple ships navigate.

[0042] In step S14, track data for each individual ship is obtained. Track data for each individual ship included in the AIS data acquired in step S10 is obtained. At the same time, the total number of ships included in the AIS data is acquired. In step S16, AIS data synchronization processing and outlier removal processing are performed for an arbitrary time period on the track data for each individual ship acquired in step S14.

[0043] In step S18, own ship information (own ship data) is extracted. Through the processing in this step, the marine collision risk assessment device 102 functions as the own ship data extraction unit 24. From the AIS data acquired in step S10 and processed in step S16, one ship is determined to be the own ship, and information about that own ship is extracted as own ship information (own ship data).

[0044] Own ship information (own ship data) includes dynamic information and static information. Dynamic information preferably includes the Maritime Mobile Service Identification Code (MMSI), time, speed over ground (SOG), latitude and longitude (LatLon), course over ground (COG), and heading (HDG). Static information preferably includes the Maritime Mobile Service Identification Code (MMSI), ship name, ship type, length of ship (Loa), and breadth. The Maritime Mobile Service Identification Code (MMSI) is used to link dynamic information with static information. The ship name and ship type are not necessary for OZT calculation, but are used to identify the ship. The length of ship (Loa) and breadth can be calculated from the GPS antenna position information included in the AIS data.

[0045] In step S20, other ship information (other ship data) is extracted. Through the processing in this step, the marine collision risk assessment device 102 functions as the other ship data extraction unit 26. From the AIS data acquired in step S10, information about other ships that may encounter a ship other than the own ship is extracted as other ship information (other ship data). There may be one or more other ships.

[0046] Other ship information (other ship data) includes dynamic information and static information. Dynamic information preferably includes the Maritime Mobile Service Identification Code (MMSI), time, speed over ground (SOG), latitude and longitude (LatLon), course over ground (COG), and heading (HDG). Static information preferably includes the Maritime Mobile Service Identification Code (MMSI), ship name, ship type, length of ship (Loa), and breadth. The Maritime Mobile Service Identification Code (MMSI) is used to link dynamic information with static information. The ship name and ship type are not necessary for OZT calculation, but are used to identify the ship. The length of ship (Loa) and breadth can be calculated from the antenna position information included in the AIS data.

[0047] In step S22, processing is performed to extract data for the same time. Through the processing in this step, the maritime collision risk assessment device 102 functions as part of the OZT calculation unit 28. Data for the same time are combined and extracted from the own ship information extracted in step S18 and the other ship data extracted in step S20.

[0048] In step S24, conditions for OZT calculation are acquired. Through the processing in this step, the maritime collision risk assessment device 102 functions as part of the OZT calculation unit 28. As conditions for OZT calculation, the calculation interval, the distance between two ships, and the minimum safe passing distance are acquired. The calculation interval is the time interval at which calculations are performed during the analysis period acquired in step S12. The calculation interval is not particularly limited, but can be, for example, 5 minutes. The distance between two ships is the distance between two ships calculated from the latitude and longitude information of the AIS data. The minimum safe passing distance is either a fixed value acquired in advance, at which safety is deemed unenforced, or a variable distance calculated from own ship information and other ship information.

[0049] In addition, pairs of vessels where the distance between the own ship and the other vessel is less than a predetermined value are considered to be encounter vessels, and all such vessels are included in the OZT calculation. On the other hand, vessels where the distance between the own ship and the other vessel is greater than the predetermined value may be excluded from the OZT calculation as they are considered not to encounter. For example, if the entire Tokyo Bay is set as the evaluation area, and all vessels navigating the area are paired one-to-one with the own ship and the other vessel, a pairing of the own ship in Tokyo Port and the other vessel at the southern end of the Uraga Strait may occur. Thus, calculating the OZT for pairs of the own ship and the other vessel that are sufficiently far apart that the collision risk is currently considered extremely low would unnecessarily increase the amount of calculation. In other words, excluding pairs of vessels that are farther apart than the predetermined value from the OZT calculation reduces the amount of calculation and is considered to be acceptable for risk assessment. Therefore, if the distance between the own ship and the other vessel is greater than the predetermined value, it is preferable to exclude them from the all vessels and omit the OZT calculation. The set value may be set to, for example, 3.0 NM.

[0050] In step S26, the OZT is calculated for each combination of the own ship and another ship. Through the processing in this step, the marine collision risk assessment device 102 functions as part of the OZT calculation unit 28. For each pair of the own ship and another ship, the OZT at the same time is calculated using the own ship information, the other ship information, the distance between the two ships, and the minimum safe passing distance.

[0051] OZT can be calculated based on conventional technology, as shown in Figure 5. (1) Position own ship O and other ship T based on the position information from AIS data, and draw a circle with a radius of minimum safe passing distance r centered on own ship O. (2) Draw tangents AA and BB to the circle from the position of other ship T. (3) Draw the speed vector VT of other ship T from the position of T, and determine its endpoint C. (4) Draw a circle with a radius of own ship O's speed vector VO centered on endpoint C. (5) The intersections of the circle with tangents AA and BB are intersections E and F, respectively. (6) The lines connecting endpoint C and intersection E, and endpoint C and intersection F, are the course of own ship O. (7) The area of ​​angle ΔC sandwiched between the two courses is translated to the position of ship O, and the lines connecting the position of ship O to intersection point E' and the position of ship O to intersection point F' are extended to the extension of the course of the other ship T, and the sandwiched line segment is defined as OZT.

[0052] In step S28, a process of outputting the calculation result of the OZT is performed. Through the process in this step, the maritime collision risk assessment device 102 functions as a part of the OZT calculation unit 28. A calculation result file (F1) of the OZT calculated in step S26 is output.

[0053] Specifically, the contents of the OZT database are output as an OZT file. Here, it is preferable that the OZT calculation results include a set of time, own ship information, other ship information, and OZT position information. Also, for example, the OZT calculation results may be stored in the memory unit 12 as an OZT database. The OZT position information can be obtained by dividing the sea area to be evaluated into a grid for each combination of latitude and longitude, assigning a grid ID to each grid, and outputting the grid ID corresponding to the OZT in association with the time, own ship information, and other ship information.

[0054] As shown in Loop 2 of FIG. 3, the above-described OZT calculation process for pairs of the own ship and other ships is repeated for each other ship that the own ship encounters until all other ships that the own ship will encounter are calculated. Specifically, steps S20 to S28 are repeated for all ships, with pairs of ships whose inter-ship distance is equal to or less than a predetermined value being considered as all ships. Furthermore, once the OZT calculation for all other ships that will encounter one own ship is completed, as shown in Loop 1 of FIG. 3, another ship is designated as the next own ship, and the OZT calculation is repeated for pairs of the own ship and other ships that will encounter the next own ship. Specifically, steps S18 to S28 are performed for all ships that may encounter the newly designated own ship based on the inter-ship distance between the other ship and the new ship. These processes are repeated until the OZT calculation for all ships is completed. In this way, the maritime collision risk assessment system 100 functions as a repeating unit 30.

[0055] Next, a method for evaluating the OZT blockage degree (BCOZT) and the probability of collision avoidance failure using the results of the OZT calculation will be described with reference to FIG.

[0056] In this embodiment, the OZT blockage degree is evaluated with reference to the evaluation of the collision avoidance maneuvering space blocking coefficient (BC), which has the advantage that it is possible to perform both individual evaluations of one ship against another and overall evaluations of one ship against many ships by arbitrarily selecting the ships to be evaluated.

[0057] In step S40, a process is performed to acquire an OZT file showing the results of the OZT calculation. Through the process in this step, the maritime collision risk assessment device 102 functions as part of the OZT data acquisition unit 32. Specifically, the OZT file output in step S28 is acquired.

[0058] In step S42, a process is performed to acquire OZT data for any own ship. Through the process in this step, the maritime collision risk assessment device 102 functions as part of the OZT data acquisition unit 32. One of the ships included in the OZT data contained in the OZT file acquired in step S40 is selected as the own ship, and all OZT data for that own ship included in the OZT file is extracted.

[0059] In step S44, a process is performed to rearrange the OZT data in chronological order. Through the process in this step, the maritime collision risk assessment device 102 functions as part of the time-based OZT data extraction unit 34. A process is performed to sort the OZT data for the own ship extracted in step S42 in the order of the time of encounter with other ships.

[0060] In step S46, a process is performed to extract OZT data that the ship simultaneously encountered at each time. Through the process in this step, the marine collision risk assessment device 102 functions as part of the time-specific OZT data extraction unit 34. For the OZT data for the ship arranged chronologically in step S44, a time of interest is set in order from the first time, and the OZT data that the ship simultaneously encountered at that time of interest is extracted.

[0061] In step S48, a process is performed to acquire the lattice ID in which the OZT exists for the OZT data that the ship encountered simultaneously at the time of interest. By the process in this step, the marine collision risk assessment device 102 functions as the lattice ID acquisition unit 36.

[0062] In step S50, the OZT blockage degree is calculated for the OZT data that the ship encountered simultaneously at the time of interest. By the processing in this step, the marine collision risk assessment device 102 functions as the OZT blockage degree calculation unit 38.

[0063] The blocking coefficient (BC) is an index that indicates the degree to which a ship is blocked by other ships in the vicinity. The blocking coefficient (BC) is expressed by the following formula (1):

number

[0064] The degree of obstruction of the space for maneuvering to avoid collisions (BC) is calculated by taking into account the ship's course changes in 5-degree increments up to 60 degrees left or right and speed changes in 10% increments from 0 to 120%, and by calculating the degree of intrusion into the exclusive zone of other ships at any course change angle and speed R(XI, J) (each course is I and each speed is J) and the weighting coefficient Pb(XI) which indicates the preference of speed and course changes as means of avoiding collisions (referring to the desirability and preference as means of maneuvering). , J). Here, the course I is calculated within the range of -60° (I=1), -55° (I=2), 0° (I=13), 60° (I=m=25) for the range of 60° left and right. Also, the speed J is calculated within the range of 0 (J=1), 10% (J=2), 10% (J=3), 10% (J=4), 10% (J=5), 10% (J=6), 10% (J=7), 10% (J=8), 10% (J=9), 10% (J=10), 10% (J=11), 10% (J=12), 10% (J=13), 10% (J=14), 10% (J=15), 10% (J=16), 10% (J=17), 10% (J=18), 10% (J=19 Calculated within the range of 120% (J=n=13).

[0065] In this embodiment, based on the evaluation method of the collision avoidance maneuvering space closure degree (BC), the collision risk with the OZT encountered by the ship is quantified by taking a weighted average of the unsafety factor Ri for n courses at any increment centered on the bow direction and the risk attenuation rate wi due to deviation from the course head-on, as shown in formula (2), and this is shown as the OZT closure degree (BCOZT).

number

[0066] When the OZT arrival time for each course is TCPAi, the dimensionless OZT arrival time TCPAi', which takes into account the ship's speed Vo [m / sec] and length Lo [m], is expressed by equation (3).

number

[0067] Furthermore, the time to reach the dimensionless OZT that is safe for the ship, TCPA0', is defined as a constant and shown as the safety margin. At this time, the unsafety factor Ri is normalized in the range of 0 to 1, as shown in equation (4). The unsafety factor Ri is defined as 0 indicating a safe state with no risk of collision, and 1 indicating a dangerous state in which a collision has occurred.

number

[0068] If the ship encounters multiple OZTs at once, TCPAi in equation (3) can be calculated from the time it takes to reach the nearest OZT from the ship.

[0069] Furthermore, it is preferable to set the constant TCPA0' based on the relationship between the crew's sense of danger and the dimensionless OZT arrival time TCPA' in actual ship accidents. Even if the OZT is directly ahead, when TCPA' is 10 or higher, the crew's sense of danger is low; when the OZT is directly ahead and TCPA' is around 10.0, the crew begins to sense danger; and regardless of the OZT position, when TCPA' is around 5.0, the crew often clearly senses danger. Therefore, it is preferable to set the safety margin time TCPA0' that ensures safety for both ships to TCPA0' = 15.0, which is a 50% margin on TCPA' = 10.0, which is the benchmark for when the crew's sense of danger is low even when the OZT is directly ahead.

[0070] In step S52, a process is performed to accumulate the OZT blockage degree (BCOZT) for each grid ID. By the process in this step, the marine collision risk assessment device 102 functions as the OZT blockage degree accumulation unit 40. The OZT blockage degrees (BCOZT) calculated in step S52 for the same grid ID are added together to calculate the probability of collision avoidance failure. In other words, in a meeting relationship between any two ships, the probability is calculated by multiplying the number of potential collisions "1" that the ship has encountered by the ship itself by the probability of collision avoidance failure (= OZT blockage degree (BCOZT)), and by accumulating this, the collision frequency in all meeting relationships is evaluated as the probability of collision avoidance failure.

[0071] The processing of steps S46 to S52 is repeated for the OZT data at each time point sorted in chronological order in step S44 (loop 4). As a result, the OZT blockage degree (BCOZT) and the probability of collision avoidance failure are calculated for the OZT data for the ship selected as the own ship in step S42.

[0072] When the process of calculating the OZT blockage degree (BCOZT) and avoidance failure probability for one own ship is completed, the process returns to step S42. Then, for the OZT data contained in the OZT file, a ship other than the ships processed so far is selected as the own ship, and the processes of steps S44 to S52 are repeated (loop 3).

[0073] By repeating these processes, the marine collision risk assessment device 102 functions as the repeating unit 42.

[0074] By the above process, the OZT blockage degree (BCOZT) and the probability of collision avoidance failure for each ship are calculated for each sea area indicated by the grid ID. That is, according to the maritime collision risk assessment system 100 of this embodiment, the OZT blockage degree (BCOZT) and the probability of collision avoidance failure can be evaluated based on AIS data.

[0075] Furthermore, when planning a route for a ship's navigation, the optimal route that allows safe navigation can be derived using information on the OZT blockage degree (BCOZT) or the probability of collision avoidance failure. This allows, for example, the route of an autonomously operated ship to be planned as an optimal route with a low collision risk. Furthermore, through this processing, the maritime collision risk assessment device 102 functions as the optimal route planning unit 46.

[0076] For example, when operating a ship, the route that connects the starting point and the end point in the shortest way among routes that pass through only sea areas that correspond to grids where the probability of collision avoidance failure is below a predetermined standard value can be set as the ship's optimal route.

[0077] The method for planning the optimum ship route is not particularly limited as long as it is based on the OZT blockage degree (BCOZT) or the probability of collision avoidance failure.

[0078] In step S54, the calculation results are output. Through the processing in this step, the maritime collision risk assessment device 102 functions as part of the input / output unit 44. For example, the maritime collision risk assessment device 102 transmits and outputs the OZT blockage degree (BCOZT) and the probability of collision avoidance failure to external devices such as company A's computer 102a, company B's computer 102b, and engine C's computer 102c. In addition, for example, the maritime collision risk assessment device 102 transmits and outputs the optimal ship route to external devices such as company A's computer 102a, company B's computer 102b, and engine C's computer 102c.

[0079] In step S56, the calculation results are visualized and displayed. The processing in this step causes the maritime collision risk assessment device 102 to function as the assessment result visualization unit 48. For example, the output unit 16 of the maritime collision risk assessment device 102 may be configured to display the calculated OZT blockage degree (BCOZT) and the probability of collision avoidance failure on a sea area map. The processing causes the maritime collision risk assessment device 102 to function as the assessment result visualization unit 48. For example, it is preferable to indicate the risk level of each sea area for the ship by changing and displaying the color, brightness, luminance, etc. of the sea area according to the probability of collision avoidance failure for each sea area indicated by the grid ID for the ship. Furthermore, the assessment results of the maritime collision risk assessment device 102 may be visualized by displaying them on an external device, such as the company A's computer 102a, the company B's computer 102b, or the engine C's computer 102c.

[0080] 6 and 7 are flowcharts showing a method for assessing a risk of collision in a maritime area according to another embodiment of the present invention, where FIG. 6 shows the steps for calculating parameters and FIG. 7 shows the steps for calculating the collision frequency.

[0081] This embodiment is a method for assessing the risk of collision in sea areas, which mainly estimates the frequency of collisions using Obstacle Zone by Target (OZT), which represents an area where the navigation of a ship is obstructed and was developed for the purpose of supporting navigation. Basically, based on the concept of a collision frequency model, the frequency of collisions is calculated as the product of the potential number of collisions (the number of collisions that will occur if the ship navigates without taking avoiding maneuvers) and the probability of failure of avoiding collisions when encountering a ship.

[0082] This embodiment also uses the OZT calculation result file (F1) output in step S28 shown in Fig. 3. The maritime collision risk assessment method in this embodiment is realized by executing a maritime collision risk assessment program in the maritime collision risk assessment device 102.

[0083] The parameter calculation steps are shown in Figure 6. In step S40, a process is performed to acquire an OZT file showing the results of the OZT calculation. Through the process in step S40, the maritime collision risk assessment device 102 functions as part of the OZT data acquisition unit 32. Specifically, the OZT calculation result file (F1) output in step S28 is acquired.

[0084] In step S42, a process is performed to acquire OZT data for any own ship. Through the process in step S42, the maritime collision risk assessment device 102 functions as part of the OZT data acquisition unit 32. One of the ships included in the OZT data acquired in step S40 is selected as the own ship, and all OZT data for that own ship included in the OZT file is extracted.

[0085] In step S44, a process is performed to rearrange the OZT data in chronological order. By the process in step S44, the marine collision risk assessment device 102 functions as part of the time-based OZT data extraction unit 34. A process is performed to sort the OZT data for the own ship extracted in step S42 in the order of the time of encounter with other ships.

[0086] In step S46, a process is performed to extract OZT data that the ship simultaneously encountered at each time. Through the process in step S46, the marine collision risk assessment device 102 functions as part of the time-specific OZT data extraction unit 34. For the OZT data for the ship arranged chronologically in step S44, a time of interest is set in order from the first time, and the OZT data that the ship simultaneously encountered at that time of interest is extracted.

[0087] In this embodiment, arbitrary OZT data is obtained from the OZT data at the time of interest extracted in step S46 (step S60), the area of ​​any OZT encountered simultaneously by the ship at the time of interest is calculated (step S62), the lattice ID in which the arbitrary OZT exists is obtained, and the arbitrary OZT is linked to the lattice ID (step S48). By repeating the processes of steps S60, S62, and S48 for each time, an OZT area file for all time periods is obtained, and further, the calculation is repeated for all ship's ships to obtain and output an OZT area file (F3) (step S64). Here, the OZT area file (F3) includes the time, ship information, other ship information, OZT length and width, OZT area, and mesh information (latitude ID, longitude ID).

[0088] The processes in steps S60 and S62 are performed by the OZT calculation unit 28, and the process in step S48 is performed by the lattice ID acquisition unit .

[0089] In step S50, the OZT blockage degree is calculated for the OZT data that the ship encountered simultaneously at the time of interest, and this is repeated for each time. The processing in step S50 is performed by the OZT blockage degree calculation unit 38. The OZT blockage degree in step S50 is calculated repeatedly for all ships, and the OZT blockage degree file (F4) is calculated and output (step S66). Here, the OZT blockage degree file (F4) includes the time, ship information, information on all other ships encountered, OZT blockage degree, and mesh information (latitude ID, longitude ID).

[0090] The steps for calculating the collision frequency are shown in Figure 7. In step S68, the OZT area file (F3) is obtained, and in step S70, the OZT blockage level file (F4) is obtained. In step S72, data for an arbitrary time is obtained from the OZT area file (F3) and the OZT blockage level file (F4). In step S74, data related to an arbitrary own ship is obtained from the data for the arbitrary time obtained in step S72. Then, based on the data obtained in step S74, the area of ​​the OZT group in an arbitrary mesh related to the arbitrary own ship is extracted (step S76), and a variable term for the number of potential OZT collisions for the OZT group encountered by the arbitrary ship is obtained for each mesh (step S78).

[0091] Next, we will explain how to estimate the number of potential OZT collisions. The expected number of collisions caused by OZT per evaluation time and per evaluation area is defined as the number of potential OZT collisions (N P ) is defined as the number of potential OZT collisions N Pi Let us consider the case (i=1). Here, the collision probability per unit area and per unit time of OZT is expressed as the OZT density (pz: OZT density) [1 / s m 2 ] is defined as follows. Consider the case where, at an infinitesimal time dt, a single collision occurs with probability P=1 at any location within any OZT with area Azi (i=1). The probability density function f(x, y, t) within Azi is given by equation (5) (x, y are position, t is time).

number

[0092] Here, since f(x, y, t) is uniformly distributed within Azi during dt, the collision probability density function per unit area and per unit time is given by equation (6).

number

[0093] From the above definition, the OZT density pzi is given by equation (7).

number

[0094] The OZT area Azi is the product of the OZT length lzi [m] and the minimum safe passing distance ri [m], which means the width.

[0095] Next, we consider the expected number of collisions for an arbitrary OZT (area Azi, density pzi) (i = 1) in an arbitrary evaluation area with an arbitrary evaluation time Te and an arbitrary evaluation area Ae. The expected number of collisions for an OZT is expressed by Equation (8) using the probability density function f(x, y, t).

number

[0096] Substituting formula (7) into formula (8) gives formula (9).

number

[0097] Here, since the area Az and the time Te are independent, Equation (9) becomes Equation (10).

number

[0098] Here, when Ae is sufficiently small compared to OZT, assuming that OZT is distributed throughout the entire evaluation area, that is, that pzi is uniformly distributed throughout Ae, the respective integrals are expressed by equations (11) and (12).

number

[0099]

number

[0100] Therefore, the expected number of collisions at an arbitrary evaluation time Te and an arbitrary evaluation area Ae, that is, the potential number of OZT collisions N Pi is expressed by Equation (13).

number

[0101] This can be said to be the average number of collisions observed in the evaluation area Ae over time Te.

[0102] Next, the number of potential OZT collisions N for the group of OZTs encountered by a random ship PS Looking at the OZTs present in any evaluation area at an infinitesimal time dt, they can be organized into the OZTs OZTs = {OZTs1, OZTs2, , OZTsn} encountered by each ship (s = 1, 2, , m).

[0103] When the area of ​​each of the OZTs (i = 1, 2, , n) encountered by a given vessel (s = 1) is Azi (i = 1, 2, , n), the given vessel can be considered to be independent of each other in the OZTs, since there is a possibility of a collision with each of the encountered vessels. The density of each OZT is expressed as pzi (i = 1, 2, , n) using equation (7).

[0104] For any evaluation time Te and any evaluation area Ae, the potential number of OZT collisions for each OZT encountered by any ship is calculated from equation (13) as N Pi (i=1,2,...,n). Since each OZT is independent, the number of potential OZT (group) collisions N of the OZT group encountered by an arbitrary ship (s=1) at an arbitrary evaluation time Te and an arbitrary evaluation area Ae is PS is N per OZT Pi It can be estimated by the sum of equation (15).

number

[0105] Substituting equation (13) and expanding it based on the fact that the minute time dt, the time Te to be evaluated, and the area Ae are constant in the OZT(s), gives equation (16).

number

[0106] Furthermore, based on the data acquired in step S74, the probability of collision avoidance failure is calculated based on the OZT blockage degree of arbitrary own ship data (step S80). The probability of collision avoidance failure refers to the probability that the own ship will fail to avoid collision, and since the greater the obstruction of the course by the OZT, the more difficult collision avoidance becomes, the risk of collision due to the OZT can be considered to correspond to the probability of collision avoidance failure. In other words, the probability of collision avoidance failure Pc is defined as the OZT blockage degree, which represents the risk of collision due to an arbitrary OZT.

[0107] Consider the probability of failing to avoid a group of OZTs encountered by a given vessel. When a given vessel encounters a group of OZTs made up of multiple vessels, it can be considered that the situation becomes more complicated than a case of obstruction by an individual OZT, and avoidance becomes more difficult. In other words, the degree of OZT blockage for a group of OZTs encountered by a given vessel (s=1) is the probability of failing to avoid a collision, Pcs.

[0108] In step S82, the variable term (ΣPcs / (Azi)) of the number of collisions with the OZT group that the given vessel encountered is calculated. The number of collisions will be shown below. According to the collision frequency model, the collision frequency is estimated as the product of the potential number of collisions and the probability of failure to avoid collisions when an encounter occurs. If the probability of failure to avoid collisions for a group of OZTs encountered by a given vessel is Pcs, the number of collisions with a group of OZTs encountered by that given vessel can be estimated by multiplying this by the potential number of OZT collisions for the group of OZTs encountered by that given vessel.

[0109] Substituting equation (16) and considering that the infinitesimal time dt, the evaluation target time Te, and the area Ae are constant, the number of collisions between an arbitrary vessel and a group of OZTs encountered can be estimated using equation (18). Note that the collision frequency refers to the number of collisions per evaluation area and evaluation time, and the collision frequency per evaluation area and evaluation time is called the number of collisions.

number

[0110] In step S84, the variable term (ΣPcs / (Azsi)) of the number of collisions between a given ship and an OZT group encountered is accumulated for each mesh in which an OZT group exists, and the variable term of the number of collisions between ships and an OZT group is calculated. That is, the processes of steps S76, S78, S80, and S82 are repeated for a given own ship at a given time, and further the processes of steps S76, S78, S80, and S82 are repeated for all own ships at a given time, and further the processes of steps S76, S78, S80, and S82 are repeated for all time periods, thereby calculating the variable term of the number of collisions between ships and an OZT group for all ships, and repeatedly estimating the number of collisions between ships and an OZT for all ships, and accumulating the variable term of the number of collisions in the mesh in which the OZT group exists.

[0111] This section describes a method for estimating the frequency of collisions of OZT groups between ship groups (s = 1, 2, . . . , m). First, calculate the potential number of OZT (group) collisions between ship groups. Since the OZT groups between ship groups are independent of each other, the potential number of OZT (group) collisions N between ship groups at an arbitrary evaluation time Te and an arbitrary evaluation area Ae is calculated. P is the potential number of OZT collisions N for the OZT group encountered by a given ship in equation (16). PS It can be estimated by the sum of equation (19).

number

[0112] Expanding this gives Equation (20) and Equation (21).

number

[0113]

number

[0114] The probability of failure to avoid collision is estimated as Pcs(s=1,2,···,m) for each ship in the group of ships (s=1,2,···,m).

[0115] The collision frequency (number of collisions) F for OZT groups among ship groups is expressed as the potential number of OZT (group) collisions N for each ship in the ship group (s = 1, 2, . . . , m). PS and the probability of collision avoidance failure Pcs(s=1,2,···,m) is estimated by equation (22).

number

[0116] Expanding this gives equation (23).

number

[0117] In step S86, an intermediate file (grid data (latitude ID, longitude ID, ΣΣ1 / (Azi)*Pcs)) is output. Since the intermediate file output in step S86 corresponds to the variable term (ΣΣPcs / (Azsi)) in equation (23), the OZT calculation conditions (e.g., OZT calculation interval dt, evaluation time Te) are obtained from the OZT calculation result file (F1) and the values ​​for each mesh are multiplied by (1 / dt) (step S88), and based on the data in the evaluation area file (F2), the values ​​for each mesh are multiplied by (Ae·Te) (step S90), the collision frequency (number of collisions) F between ship groups against the OZT group is calculated, and the resulting file (F5) is output (S92).

[0118] In this way, the area of ​​the grid in which the pre-calculated OZT exists is obtained, and the collision frequency per unit time and unit area is calculated by dividing the variable term for the number of collisions in all meshes in which the OZT exists by the OZT calculation interval, and then the number of collisions within the mesh in the evaluation time is calculated and output using the evaluation area and evaluation time (corresponding to the analysis period in the AIS analysis conditions in Figure 4).

[0119] Figure 8 shows the calculation flow for the evaluation area file shown in Figure 7. The output (step S103) of the evaluation area file (F2) shown in Figure 7 is performed by acquiring the grid size conditions (step S100), calculating the length and width of each grid (step S101), and calculating the area of ​​each grid (step S102), as shown in Figure 8. In this way, the area of ​​the grid where the OZT exists is calculated in advance, but if the latitude interval of the target sea area is narrow, the grid area at any latitude can be substituted as a representative value.

[0120] Fig. 9 shows a flow of visualizing the results. The result file (F5) (step S92) output by the process shown in Fig. 7 visualizes and displays the number of collisions and the collision frequency (step S110).

[0121] Finally, the number of collisions between ships and OZTs when the evaluation area is the entire sea area is N Z The total area is A = {Ae1, Ae2, , Aek} (j = 1, 2, k), and the number of potential OZT (group) collisions in each evaluation area is N Pj are independent, so N Z is N Pj It is estimated by the summation using equation (24).

number

[0122] In other words, this refers to the collision frequency between groups of ships targeting OZT groups, and corresponds to the sum of the values ​​obtained by multiplying each mesh in the intermediate file (step S86) output by repeating steps S76, S78, and S84 by (1 / dt).

[0123] In addition, the number of collisions in the entire sea area F Z is estimated by the sum of the number of collisions Fj (j = 1, 2, · · · k) in each evaluation area using equation (25).

number

[0124] where N Pj , Fj are expressed by the following equations (21) and (23), respectively.

[0125] In other words, this corresponds to the sum of the collision frequencies (number of collisions) F between the ships and the OZTs output in step S92. [Industrial Applicability]

[0126] The present invention can be used to evaluate the OZT obstruction degree (BCOZT) and the probability of collision avoidance failure in a sea area where multiple mobile objects are navigating due to a navigation obstruction zone. Furthermore, it is possible to plan an optimal route with a low collision risk for mobile objects based on the OZT obstruction degree (BCOZT) or the probability of collision avoidance failure.

[0127] The scope of application of the present invention is not limited to the assessment of collision risk for ships sailing in the ocean, lakes, and marshes, but can also be applied to the assessment of collision risk for mobile bodies sailing on land or in the air. [Explanation of symbols]

[0128] 10 Processing section 12 Storage section 14 Input section 16 Output section 20 Evaluation condition acquisition unit 22 AIS data acquisition unit 24 Own ship data extraction unit 26 Other ship data extraction section 28 OZT calculation section 30 Repeating section 32 OZT data acquisition section 34 Time-specific OZT data extraction section 36 Grid ID acquisition part 38 OZT occlusion degree calculation section 40 OZT occlusion degree accumulation part 42 Repeating section 44 Input / output section 46 Optimal Route Planning Department 48 Evaluation result visualization unit 100 Maritime Collision Risk Assessment System 102 Maritime Collision Risk Assessment Device 102a Company A's computer 102b Company B's computer 102c Agency C's computer 104 Information and Communications Network

Claims

1. A marine collision risk assessment program for assessing a collision risk in a marine area where multiple ships navigate due to an obstruction zone (OZT), On the computer, an evaluation condition acquisition step of acquiring the sea area and the analysis period as evaluation conditions; an AIS data acquisition step of acquiring AIS data of the ship navigating the sea area; One of the plurality of ships is determined as the own ship, and the own ship data is extracted from the AIS data. an own ship data extraction step; an other ship data extraction step of determining other ships among the plurality of ships other than the own ship as other ships that the own ship will encounter, and extracting other ship data from the AIS data; an OZT calculation step of performing OZT calculations for the own ship and the other ship as a pair at the same time; a repeating step of determining another of the plurality of ships as the next own ship, extracting the own ship data, extracting the other ship data, and calculating the OZT until the steps are completed for all ships encountered; A program for evaluating a risk of a maritime collision using OZT, characterized by executing an OZT calculation result output step of outputting the result of the OZT calculation.

2. The maritime collision risk assessment program using OZT according to claim 1, A marine collision risk assessment program using OZT, characterized in that when performing the OZT calculation in the OZT calculation step, a minimum safe passing distance defined by a pre-acquired calculation interval, information on the own ship and the other ship and the distance between the two ships, and a pre-acquired fixed value or a variable distance calculated from the information on the own ship and the other ship is used.

3. The maritime collision risk assessment program using OZT according to claim 1, A marine collision risk assessment program using OZT, characterized in that it calculates track data for each of the ships based on the acquired AIS data, and uses synchronized track data as the AIS data at any time.

4. The maritime collision risk assessment program using OZT according to claim 1, A collision risk assessment program using OZT, characterized in that the OZT calculation for the pair of the own ship and the other ship in the OZT calculation step is repeated for each other ship that encounters the own ship until the calculation is completed for all other ships that will be encountered.

5. The maritime collision risk assessment program using OZT according to claim 1, an OZT data acquisition step of acquiring OZT data for any of the ship's own ship from the result of the OZT calculation outputted in the OZT calculation result output step; a time-based OZT data extraction step of sorting the OZT data in time order and extracting all OZT data by time; a lattice ID acquisition step of acquiring a lattice ID where the OZT exists; an OZT blockage degree calculation step of calculating an OZT blockage degree for each grid ID by time using ship track data synchronized with ship hull information including the ship captain of the ship; an OZT blockage degree accumulation step of accumulating the OZT blockage degree in the lattice ID; a repeating step of repeating the OZT data acquisition step, the time-based OZT data extraction step, the grid ID acquisition step, the OZT blockage degree calculation step, and the OZT blockage degree accumulation step until they are completed for all of the ships; The program for evaluating a risk of a marine collision using OZT further executes an evaluation result output step of outputting the cumulative result of the OZT blockage degree as a collision risk evaluation result.

6. 6. The maritime collision risk assessment program using OZT according to claim 5, A program for evaluating the risk of marine collisions using OZT, characterized in that in the repeating step, the grid ID acquisition step, the OZT blockage degree calculation step, and the OZT blockage degree accumulation step are repeated sequentially for all of the OZT data by time extracted in the time-specific OZT data extraction step.

7. 6. The maritime collision risk assessment program using OZT according to claim 5, A marine collision risk assessment program using OZT, characterized by executing an assessment result visualization step of visualizing and displaying the output collision risk assessment results.

8. 6. The maritime collision risk assessment program using OZT according to claim 5, A marine collision risk assessment program using OZT, characterized in that it plans an optimal route for the ship based on the collision risk assessment result obtained in the assessment result output step.

9. The maritime collision risk assessment program using OZT according to claim 1, A program for assessing the risk of collision in a sea area using OZT, characterized in that: OZT data for an arbitrary ship is obtained from the output results of the OZT calculation, the OZT data by time is extracted, the area of ​​an arbitrary OZT is calculated from the OZT data, the arbitrary OZT is linked to a grid ID, and then the calculation is repeated for all ships to obtain and output an OZT area file; meanwhile, the OZT blockage degree (probability of failing to avoid collision) for all OZTs caused by a group of ships encountered by the arbitrary ship is repeatedly calculated for all ships to obtain and output an OZT blockage degree file.

10. The maritime collision risk assessment program using OZT according to claim 9, A program for evaluating a risk of a marine collision using OZT, characterized in that the area calculation and the OZT blockage degree calculation are repeated sequentially for all of the extracted time-based OZT data.

11. The maritime collision risk assessment program using OZT according to claim 10, A program for assessing the risk of marine collisions using OZT, characterized in that it obtains arbitrary time data and arbitrary own ship data from the output OZT area file and OZT blockage level file, extracts and sums the areas of all the OZTs in an arbitrary mesh in which the OZT with the group of ships encountered by the arbitrary own ship exists, and takes the reciprocal to determine a variable term for the number of potential OZT collisions, obtains the probability of collision avoidance failure based on the OZT blockage level of the arbitrary own ship data, and repeatedly estimates the variable term for the number of collisions with the group of ships encountered by the own ship, which is calculated by multiplying the variable term for the number of potential OZT collisions by the probability of collision avoidance failure, for all meshes of the own ship, and further repeats this for all the own ships, thereby accumulating the variable term for the number of collisions in the mesh in which the OZT exists.

12. The maritime collision risk assessment program using OZT according to claim 11, A marine collision risk assessment program using OZT, characterized in that acquisition of the arbitrary time data is repeated until acquisition of the arbitrary own ship data is completed for all times, and until acquisition of the arbitrary own ship data is completed for all ships.

13. The maritime collision risk assessment program using OZT according to claim 12, A marine collision risk assessment program using OZT, characterized in that the number of collisions per unit time and unit area is calculated by dividing the variable term of the number of collisions in the mesh in which the OZT exists by the OZT calculation interval, and further the number of collisions in the mesh in the evaluation time is calculated and output by integrating the area of ​​the grid in which the OZT exists and the evaluation time that have been calculated in advance.

14. The maritime collision risk assessment program using OZT according to claim 13, A marine collision risk assessment program using OZT that visualizes and displays the output collision count results.

15. A computer, an input means, and an output means, 15. A system for evaluating a risk of a maritime collision using OZT, comprising causing the computer to execute the program for evaluating a risk of a maritime collision using OZT according to claim 1.

16. The system for assessing a risk of a marine collision using the OZT according to claim 15, A maritime collision risk assessment system using OZT, characterized in that the computer, the input means, and the output means are connected via an information and communications network.

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