Target monitoring device, target monitoring method, and program

Abstract

[Problem] To provide a target monitoring device with which it is possible to improve the accuracy of estimating a hull length. [Solution] This target monitoring device comprises: a data acquiring unit for acquiring image data including a ship observed by means of an imaging sensor; an image recognition unit for detecting an area of the ship included in the image data; a distance acquiring unit for acquiring a distance to the ship from an observation position, detected by a sensor different from the imaging sensor; a course acquiring unit for acquiring a course of the ship detected by a sensor different from the imaging sensor; and a hull length estimating unit for estimating a hull length of the ship on the basis of a horizontal-direction dimension of the region of the ship, the distance to the ship, and the course of the ship.

Description

[Technical Field]

[0001] This invention relates to a target monitoring device, a target monitoring method, and a program. [Background technology]

[0002] Patent Document 1 discloses a technique for calculating the length of a ship using radar. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Patent No. 5730565 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, because radar has low azimuth resolution, it is difficult to determine the size of a ship from radar echoes.

[0005] The present invention has been made in view of the above problems, and its main objective is to provide a target monitoring device, a target monitoring method, and a program that can improve the accuracy of estimating the length of a ship. [Means for solving the problem]

[0006] To solve the above problems, a target monitoring device according to one aspect of the present invention includes a data acquisition unit that acquires image data including a ship observed by an imaging sensor, an image recognition unit that detects the region of the ship included in the image data, a distance acquisition unit that acquires the distance from the observation position detected by a sensor other than the imaging sensor to the ship, a course acquisition unit that acquires the course of the ship detected by a sensor other than the imaging sensor, and a hull length estimation unit that estimates the hull length of the ship based on the horizontal dimensions of the region of the ship, the distance to the ship, and the course of the ship. This makes it possible to improve the accuracy of estimating the hull length.

[0007] In the above embodiment, the hull length estimation unit may further estimate the hull length of the vessel based on a predetermined aspect ratio of the hull. This makes it possible to improve the accuracy of the hull length estimation.

[0008] In the above embodiment, the imaging sensor is a camera, and the hull length estimation unit calculates the angle occupied by the ship within the field of view based on the horizontal dimensions of the image data, the horizontal dimensions of the ship's area, and the horizontal field of view of the camera, and estimates the ship's hull length based on the ship's occupied angle, the distance to the ship, and the ship's course. This makes it possible to improve the accuracy of the ship length estimation.

[0009] In the above embodiment, the hull length estimation unit may calculate the angle occupied by the target within the field of view based on the horizontal dimensions of the image data, the horizontal dimensions of the target area, the horizontal field of view of the camera, the focal length of the camera, and the optical center of the camera. This makes it possible to improve the accuracy of the hull length estimation.

[0010] In the above embodiment, the other sensor may be a radar, and the distance acquisition unit may acquire the distance to the vessel based on the data detected by the radar. This makes it possible to estimate the length of the vessel using the distance to the vessel detected by the radar.

[0011] In the above embodiment, the other sensor may be a radar, and the course acquisition unit may acquire the course of the vessel based on the data detected by the radar. This makes it possible to estimate the length of the vessel using the course of the vessel detected by the radar.

[0012] In the above embodiment, the image recognition unit may detect the boundary box surrounding the vessel included in the image as the vessel's region. This makes it easier to obtain the horizontal dimensions of the vessel's region.

[0013] Furthermore, another aspect of the present invention involves a target monitoring method which acquires image data including a vessel observed by an imaging sensor, detects the area of ​​the vessel included in the image data, acquires the distance from the observation position detected by a sensor other than the imaging sensor to the vessel, acquires the course of the vessel detected by a sensor other than the imaging sensor, and estimates the hull length of the vessel based on the horizontal dimensions of the area of ​​the vessel, the distance to the vessel, and the course of the vessel. This makes it possible to improve the accuracy of the hull length estimation.

[0014] Furthermore, a program in another aspect of the present invention causes a computer to perform the following actions: acquire image data including a ship observed by an imaging sensor; detect the region of the ship included in the image data; acquire the distance from the observation position detected by a sensor other than the imaging sensor to the ship; acquire the ship's course detected by a sensor other than the imaging sensor; and estimate the ship's hull length based on the horizontal dimensions of the ship's region, the distance to the ship, and the ship's course. This makes it possible to improve the accuracy of the ship length estimation. [Brief explanation of the drawing]

[0015] [Figure 1] This is a diagram showing an example configuration of a target monitoring system. [Figure 2]It is a diagram showing a configuration example of a target monitoring device. [Figure 3] It is a diagram showing a configuration example of an image processing unit. [Figure 4] It is a diagram showing an example of image recognition. [Figure 5] It is a diagram showing an example of a bounding box. [Figure 6] It is a diagram showing an example of an echo. [Figure 7] It is a diagram showing an example of an echo. [Figure 8] It is a diagram showing an example of the calculation of the hull length. [Figure 9] It is a diagram showing an example of the calculation of the hull length. [Figure 10] It is a diagram showing an example of the calculation of the hull length. [Figure 11] It is a diagram showing an example of the procedure of a target monitoring method.

Embodiments for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0017] FIG. 1 is a block diagram showing a configuration example of a target monitoring system 100. The target monitoring system 100 is a system mounted on a ship. In the following description, the ship on which the target monitoring system 100 is mounted is referred to as the "own ship", and other ships are referred to as "other ships".

[0018] The target monitoring system 100 includes a target monitoring device 1, a display unit 2, a radar 3, an AIS 4, a camera 5, a GNSS receiver 6, a gyrocompass 7, an ECDIS 8, a wireless communication unit 9, and a ship control unit 10. These devices are connected to a network N such as a LAN, for example, and can communicate with each other via the network.

[0019] The target monitoring device 1 is a computer including a CPU, a RAM, a ROM, a non-volatile memory, an input / output interface, and the like. The CPU of the target monitoring device 1 executes information processing according to a program loaded from the ROM or the non-volatile memory into the RAM.

[0020] The program may be supplied via an information storage medium such as an optical disc or memory card, or via a communication network such as the Internet or LAN.

[0021] Display unit 2 displays display images generated by target monitoring device 1. Display unit 2 also displays radar images, camera images, or electronic charts.

[0022] The display unit 2 is, for example, a display device with a touch sensor, a so-called touch panel. The touch sensor detects the position indicated on the screen by the user's finger or the like. However, the position may also be input by a trackball or the like.

[0023] Radar 3 emits radio waves around the vessel and receives the reflected waves, generating echo data based on the received signals. Radar 3 also identifies targets from the echo data and generates TT data (Target Tracking) representing the target's position and speed.

[0024] The Automatic Identification System (AIS) 4 receives AIS data from other vessels or shore-based control systems in the vicinity of the vessel. While AIS is not the only option, a VHF Data Exchange System (VDES) may also be used. AIS data includes the identification code, name, position, course, speed, vessel type, length, and destination of other vessels.

[0025] Camera 5 is a digital camera that captures images of the outside from the ship and generates image data. Camera 5 is installed, for example, on the ship's bridge, facing the bow. Camera 5 may also be a camera with pan, tilt, and zoom functions, a so-called PTZ camera.

[0026] Furthermore, camera 5 may include an image recognition unit that estimates the position and type of targets, such as other vessels, included in the captured image using an object detection model. The image recognition unit is not limited to camera 5, but may also be implemented in other devices such as the target monitoring device 1.

[0027] The GNSS receiver 6 detects the ship's position based on radio waves received from the GNSS (Global Navigation Satellite System). The gyrocompass 7 detects the ship's heading. A GPS compass may be used instead of a gyrocompass.

[0028] The ECDIS (Electronic Chart Display and Information System) 8 obtains the ship's position from the GNSS receiver 6 and displays the ship's position on the electronic chart. The ECDIS 8 also displays the ship's planned route on the electronic chart. A GNSS plotter may be used instead of the ECDIS.

[0029] The radio communication unit 9 includes various radio equipment for enabling communication with other ships or land-based air traffic control, such as radio equipment for the ultra-high frequency, very high frequency, medium frequency, and short frequency bands.

[0030] The ship steering control unit 10 is a control device for realizing automatic ship steering and controls the ship's steering gear. The ship steering control unit 10 may also control the ship's engine.

[0031] In this embodiment, the target monitoring device 1 is an independent device, but it is not limited to this and may be integrated with other devices such as ECDIS8. In other words, the functional parts of the target monitoring device 1 may be implemented by other devices.

[0032] In this embodiment, the target monitoring device 1 is mounted on the vessel itself and used to monitor targets such as other vessels in the vicinity of the vessel; however, its use is not limited to this. For example, the target monitoring device 1 may be installed at a land-based control center and used to monitor vessels in a controlled area.

[0033] Figure 2 shows an example of the configuration of the target monitoring device 1. The control unit 20 of the target monitoring device 1 includes data acquisition units 11, 12, 13, an image processing unit 14, a data integration unit 15, a display control unit 16, and a ship operation decision unit 17. These functional units are realized by the control unit 20 executing information processing according to a program.

[0034] The control unit 20 of the target monitoring device 1 further includes a radar management database 21, an AIS management database 22, a camera management database 23, and an integrated management database 24. These storage units are located in the memory of the control unit 20.

[0035] The data acquisition unit 11 sequentially acquires the TT data generated by the radar 3 as target data and registers it in the radar management DB 21.

[0036] The target data registered in the radar management DB21 includes the position, speed, and course of targets such as other vessels detected by radar 3. The target data registered in the radar management DB21 may further include the target's track, elapsed time since detection, size of the echo image, and signal strength of the reflected wave.

[0037] The data acquisition unit 12 acquires the AIS data received by AIS4 as target data and registers it in the AIS management DB 22.

[0038] The target data registered in the AIS management DB22 includes the position, speed, and course of other vessels detected by AIS4. The target data registered in the AIS management DB22 may further include the type, name, and destination of other vessels.

[0039] The data acquisition unit 13 acquires images including targets such as other vessels captured by the camera 5. The data acquisition unit 13 sequentially acquires time-series images from the camera 5 and provides them sequentially to the image processing unit 14. The time-series images are, for example, still images (frames) included in video data.

[0040] The image processing unit 14 performs predetermined image processing, such as image recognition, on the image acquired by the data acquisition unit 13, generates target data for the recognized targets from the image, and registers it in the camera management DB 23. Details of the image processing unit 14 will be described later.

[0041] The target data registered in the camera management DB23 includes the position, speed, and course of targets such as other vessels, calculated by the image processing unit 14. The target data registered in the camera management DB23 may further include the size of the target, the type of target, and the elapsed time since detection.

[0042] The position of the target detected by radar 3 and the position of the target recognized from the image captured by camera 5 are relative positions to the ship, so they are converted to absolute positions using the ship's position detected by GNSS receiver 6.

[0043] The targets detected by radar 3 and those recognized from images captured by camera 5 are mainly ships, but may also include other objects such as buoys.

[0044] The data integration unit 15 registers target data registered in the radar management DB 21, AIS management DB 22, and camera management DB 23 into the integrated management DB 24, which manages these databases across the board. The target data registered in the integrated management DB 24 includes the position, speed, and course of targets such as other vessels.

[0045] The data integration unit 15 integrates target data and registers it in the integrated management DB 24 if the location of a target in the target data registered in one of the radar management DB 21, AIS management DB 22, and camera management DB 23 is the same as or similar to the location of a target in the target data registered in the other one.

[0046] The display control unit 16 generates a display image containing objects representing targets based on target data registered in the integrated management DB 24 and outputs it to the display unit 2. The display image is, for example, a radar image, an electronic chart, or an image combining them, and the objects representing targets are placed in positions within the image that correspond to the actual locations of the targets.

[0047] The ship handling decision unit 17 makes a ship handling decision based on the target data registered in the integrated management DB 24, and if it determines that it is necessary to avoid a target, it instructs the ship handling control unit 10 to perform avoidance maneuvers. Specifically, the ship handling control unit 10 calculates an avoidance route to avoid the target using an avoidance maneuvering algorithm, and controls the steering gear and engines, etc., so that the ship follows the avoidance route.

[0048] Figure 3 shows an example of the configuration of the image processing unit 14. The image processing unit 14 includes an image recognition unit 31, a distance / course acquisition unit 32, and a hull length estimation unit 33. The figure shows the configuration related to the function of estimating the hull length of other ships, which is one of the functions realized by the image processing unit 14.

[0049] In this embodiment, the image processing unit 14 acquires image data, including targets such as other vessels, captured by the camera 5, from the data acquisition unit 13. The camera 5 is an example of an imaging sensor. However, it is not limited to this, and image data observed by other imaging sensors, such as LiDAR (Light Detection and Ranging), may also be acquired. Image data observed by LiDAR is also included in the image data.

[0050] The image recognition unit 31 detects the area of ​​a ship included in the image acquired by the data acquisition unit 13. Specifically, the image recognition unit 31 uses a pre-trained model generated by machine learning to calculate the area of ​​a ship, the type of target, and the confidence level of the estimation included in the image. The type of target is, for example, a tanker or a fishing boat. However, the image recognition unit 31 may also recognize the area and type of target included in the image using a rule-based method.

[0051] The trained model is, for example, an object detection model such as SSD (Single Shot MultiBox Detector) or YOLO (You Only Look Once), which detects the bounding box surrounding a ship in an image as the ship's region. However, the trained model may also be a region segmentation model such as Semantic Segmentation or Instance Segmentation.

[0052] Figure 4 shows an example of recognition of image P. Figure 5 shows a magnified view of the boundary box BB. As shown in these figures, the other vessel SH included in image P is surrounded by a rectangular boundary box BB. A label CF is attached to the boundary box BB, indicating the type of target and the confidence level of the estimation.

[0053] In Figure 4, Lb represents the horizontal dimension of image P. In Figure 5, Lw represents the horizontal dimension of the area of ​​the other ship SH, i.e., the horizontal dimension of the boundary box BB. The horizontal direction of the image corresponds to the horizontal direction in real space, and in the illustrated example, it is the left-right direction. Dimensions are expressed, for example, in pixels.

[0054] The horizontal dimension Lw of the area of ​​the other vessel SH detected from the image changes depending on the distance and orientation from the other vessel SH. Therefore, it is difficult to determine the hull length of the other vessel SH using only this dimension Lw. In this embodiment, the accuracy of estimating the hull length is improved by using data of the other vessel SH detected by a target detection unit other than camera 5, as described below.

[0055] The distance / course acquisition unit 32 acquires the distance from its own vessel to the other vessel and the other vessel's course from the TT data generated by the radar 3. Specifically, the distance / course acquisition unit 32 reads the target data of the target other vessel from the radar management DB 21 and acquires the distance from its own vessel to the other vessel and the other vessel's course from the read target data. The radar 3 is an example of "another sensor".

[0056] The course of the other vessel is, for example, the course over ground (COG). However, the heading (HDG) of the other vessel may also be used. While it is preferable to use the heading to estimate the hull length, in this embodiment, the course over ground is used for ease of acquisition.

[0057] As shown in Figure 6, the echo EC detected by radar 3 allows us to determine the distance d to the target MK and the target MK's course DR. However, because the echo EC has an angularly spread shape, meaning that radar 3 has low azimuth resolution, it is difficult to determine the size of the target MK from the size of the echo EC. This difficulty becomes particularly pronounced as the distance d increases.

[0058] Therefore, in this embodiment, as shown in Figure 7, the accuracy of estimating the hull length of the other vessel SH is improved by combining the bearing width (occupied angle) θ obtained by the camera 5 with high bearing resolution and the distance d and course DR obtained by the radar 3 with high distance resolution.

[0059] The distance / course acquisition unit 32 may acquire the distance from its own vessel to another vessel and the course of the other vessel from the AIS data received by AIS4.

[0060] The hull length estimation unit 33 estimates the hull length of the other vessel based on the horizontal dimensions of the other vessel's area detected by the image recognition unit 31, and the distance and course of the other vessel acquired by the distance / course acquisition unit 32. Furthermore, the hull length estimation unit 33 estimates the hull length of the other vessel based on a predetermined aspect ratio of the hull. Before estimating the hull length, pre-processing such as distortion correction may be applied to the image.

[0061] Specifically, as shown in Figure 8, the hull length estimation unit 33 first calculates the angle (azimuth width) θ occupied by the other vessel SH within the field of view Θ, based on the horizontal dimension Lb of the image, the horizontal dimension Lw of the area of ​​the other vessel SH, and the horizontal field of view Θ of the camera 5. Dimensions Lb and Lw represent dimensions within the image (e.g., number of pixels). Distance d represents the distance in real space detected by the radar 3.

[0062] The field of view Θ is the angle that represents the range included in the image when captured by camera 5, and is determined by the lens of camera 5. The angle of occupation of other vessels SH θ is the angle that represents the range occupied by other vessels SH, and is the angle between the left and right edges of other vessels SH with camera 5 as the center.

[0063] The ratio of the horizontal dimension Lb of the image to the horizontal dimension Lw of the area of ​​the other vessel SH can be considered the same as the ratio of the horizontal field of view Θ of camera 5 to the occupied angle θ of the other vessel SH, and thus the occupied angle θ of the other vessel SH can be calculated.

[0064] More specifically, the hull length estimation unit 33 may calculate the angle θ occupied by the target SH within the field of view Θ based on the horizontal dimension Lb of the image, the horizontal dimension Lw of the area of ​​the target SH, and the horizontal field of view Θ of the camera 5, as well as the focal length and optical center of the camera 5. That is, in order to take into account the intrinsic parameters of the camera in the perspective projection model, the angle θ occupied by the target SH may be calculated using the focal length and optical center of the camera 5, which represent the intrinsic parameters of the camera.

[0065] Next, as shown in Figure 9, the hull length estimation unit 33 calculates the occupancy angle θ of the other ship SH, the distance d from the own ship SP to the other ship SH, the relative course φ of the other ship SH with respect to the own ship, and the deviation angle φ according to the aspect ratio of the hull. asp Based on this, we estimate the hull length L of the other vessel SH.

[0066] The hull length L of the other vessel SH is expressed by the following formula 1.

[0067]

number

[0068] L dig φ is the length of the diagonal when the hull of the other ship SH is assumed to be rectangular, and corresponds to the angle θ occupied by the other ship SH (i.e., the part that appears in the image). asp This is determined by the aspect ratio of the hull, and is L relative to the course φ of other ships. dig This is the angle of deviation, and tan -1 It is expressed as (width of the hull / length of the hull).

[0069] L dig This is expressed by the following formula 2.

[0070]

number

[0071] The derivation of equation 2 will be explained using Figure 10, with an example where φ is in the range of 0° to 90°.

[0072] In this diagram, the line segment from the position P of our ship to the left end of the diagonal of the other ship SH is denoted as A, and the line segment to the right end is denoted as B. Also, the length of the diagonal of the other ship SH is L'(=L dig ) and the course φ of other vessel SH and the angle of deviation φ asp Let φ' be the angle formed by combining the two angles.

[0073] The triangle formed by the left and right ends of the diagonal of the other ship SH, and the position P of our own ship, is represented by the following formula 3.

[0074]

number

[0075] Multiplying both sides of equation 3 by 2cosθ yields equation 4 below.

[0076]

number

[0077] Furthermore, the vectors A and B, with the ship's position P as the origin, can be expressed as shown in equation 5 below.

[0078]

number

[0079] Taking the dot product of vectors A and B yields equation 6 below.

[0080]

number

[0081] Substituting equation 6 into equation 4 above yields equation 7 below.

[0082]

number

[0083] By rearranging equation 7, we obtain equation 8 for L'.

[0084]

number

[0085] Solving equation 8 for L' using the quadratic formula yields equation 9 below.

[0086]

number

[0087] Here, since the distance is a positive value, we have the following equation 10.

[0088]

number

[0089] Here, L' = L dig and φ' = φ + φ asp Therefore, Equation 10 becomes the same as Equation 2 above.

[0090] The hull length estimation unit 33 estimates the hull length L of the other ship SH as described above. The hull length L of the other ship SH estimated by the hull length estimation unit 33 is included in the target data together with the position, ship speed, and course of the other ship SH, and is registered in the camera management DB 23.

[0091] In this embodiment, the area of the other ship SH is detected by image recognition from the image captured by the camera 5. However, the present invention is not limited to this, and for example, the area of the other ship SH may be detected by image recognition from image data including the other ship observed by another sensor such as LiDAR (Light Detection and Ranging). The sensor preferably has a higher azimuth resolution than the radar 3.

[0092] FIG. 11 is a diagram showing an example of the procedure of the target monitoring method realized in the target monitoring system 100. This figure mainly shows the process of estimating the hull length of the other ship. The target monitoring device 1 executes the process shown in this figure according to a program.

[0093] When the target monitoring device 1 acquires an image captured by the camera 5, it performs image recognition processing and calculates the area of the other ship, the type of the ship, and the reliability of the estimation included in the image (S11, processing as the image recognition unit 31).

[0094] Next, the target monitoring device 1 acquires the horizontal dimension of the area of the other ship calculated by the image recognition processing (S12). The horizontal dimension of the area of the other ship is the horizontal dimension Lw of the bounding box BB (see FIG. 5).

[0095] Next, the target monitoring device 1 acquires the distance from the own ship to the other ship and the course of the other ship based on the target data detected by the radar 3 (S13, processing as the distance / course acquisition unit 32).

[0096] Next, the target monitoring device 1 estimates the hull length of the other vessel based on the horizontal dimensions of the other vessel's area, the distance from its own vessel to the other vessel, and the other vessel's course (S14, processing as the hull length estimation unit 33).

[0097] Subsequently, the target monitoring device 1 generates target data including the hull length of the other vessel, along with its position, speed, and course, and registers it in the camera management DB 23 (S15). This completes the series of processing on the image.

[0098] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and various modifications are of course possible for those skilled in the art. [Explanation of Symbols]

[0099] 1 Target monitoring device, 2 Display unit, 3 Radar, 4 AIS, 5 Camera, 6 GNSS receiver, 7 Gyrocompass, 8 ECDIS, 9 Wireless communication unit, 10 Ship handling control unit, 20 Control unit, 11, 12, 13 Data acquisition unit, 14 Image processing unit, 15 Data integration unit, 16 Display control unit, 17 Ship handling decision unit, 21 Radar management DB, 22 AIS management DB, 23 Camera management DB, 24 Integrated management DB, 31 Image recognition unit, 32 Distance / course acquisition unit, 33 Ship length estimation unit, 100 Target monitoring system

Claims

1. A data acquisition unit that acquires image data including ships observed by an imaging sensor, An image recognition unit that detects the area of ​​the ship included in the image data, A distance acquisition unit that acquires the distance from the observation position detected by a sensor other than the aforementioned imaging sensor to the ship, A course acquisition unit that acquires the course of the ship detected by a sensor other than the imaging sensor, A hull length estimation unit estimates the hull length of the vessel based on the horizontal dimensions of the vessel's area, the distance to the vessel, and the vessel's course. Equipped with, The aforementioned imaging sensor is a camera, The hull length estimation unit is, Based on the horizontal dimensions of the image data, the horizontal dimensions of the vessel's area, and the horizontal field of view of the camera, the angle occupied by the vessel within the field of view is calculated. The length of the vessel is estimated based on the angle occupied by the vessel, the distance to the vessel, and the course of the vessel. Target monitoring device.

2. The hull length estimation unit estimates the hull length of the vessel based on a predetermined aspect ratio of the hull. The target monitoring device according to claim 1.

3. The hull length estimation unit is, Based on the horizontal dimensions of the image data, the horizontal dimensions of the vessel's area, the horizontal field of view of the camera, the focal length of the camera, and the optical center of the camera, the angle occupied by the vessel within the field of view is calculated. The target monitoring device according to claim 1 or 2.

4. The aforementioned other detection method is radar, The distance acquisition unit acquires the distance to the vessel based on the data detected by the radar. A target monitoring device according to any one of claims 1 to 3.

5. The aforementioned other detection method is radar, The course acquisition unit acquires the course of the vessel based on the data detected by the radar. A target monitoring device according to any one of claims 1 to 4.

6. The image recognition unit detects the boundary box surrounding the vessel included in the image data as the region of the vessel. A target monitoring device according to any one of claims 1 to 5.

7. Image data including ships observed by imaging sensors is acquired. The region of the ship contained in the image data is detected, The distance from the observation position detected by a sensor other than the aforementioned imaging sensor to the vessel is obtained. The course of the ship, detected by a sensor other than the imaging sensor, is acquired. The length of the vessel is estimated based on the horizontal dimensions of the vessel's area, the distance to the vessel, and the vessel's course. A target monitoring method, The aforementioned imaging sensor is a camera, The estimation of the hull length is as follows: Based on the horizontal dimensions of the image data, the horizontal dimensions of the vessel's area, and the horizontal field of view of the camera, the angle occupied by the vessel within the field of view is calculated. The length of the vessel is estimated based on the angle occupied by the vessel, the distance to the vessel, and the course of the vessel. Target monitoring method.

8. To acquire image data including ships observed by imaging sensors, To detect the area of ​​the ship included in the image data, To obtain the distance from the observation position detected by a sensor other than the aforementioned imaging sensor to the aforementioned vessel, To acquire the course of the ship detected by a sensor other than the aforementioned imaging sensor, and To estimate the hull length of the vessel based on the horizontal dimensions of the vessel's area, the distance to the vessel, and the vessel's course. Have the computer run it, The aforementioned imaging sensor is a camera, The estimation of the hull length is as follows: Based on the horizontal dimensions of the image data, the horizontal dimensions of the vessel's area, and the horizontal field of view of the camera, the angle occupied by the vessel within the field of view is calculated. The length of the vessel is estimated based on the angle occupied by the vessel, the distance to the vessel, and the course of the vessel. program.

Images