JP6642307B2 - Perimeter monitoring device - Google Patents

Description

  Embodiments of the present invention relate to a periphery monitoring device.

  2. Description of the Related Art Conventionally, there is a vehicle having a crossing (crossing) function. For example, a vehicle referred to as an off-road vehicle may be provided with a waterproofing measure so as to be able to run over water (underwater traveling) in swamps, rivers, flooded roads, and the like. In such vehicles, for example, the distance to the water surface is measured using a sensor such as an ultrasonic sonar, and a graphic image of the water surface and the own vehicle is displayed on a display device provided in the vehicle cabin, and the vehicle is in a traveling state. There is a system equipped with a system for displaying a simulation in a pseudo manner.

JP-T-2015-512825

  However, when the vehicle travels over the road, the water surface is often wavy. When detecting the distance to the water surface with a sensor such as an ultrasonic sonar and displaying a graphic image indicating the water surface as in the above-described technique, it is difficult to accurately measure the distance to the water surface due to the rising and falling of the water surface due to waving. There are cases. In this case, there is a problem that the wavy state and the height to the water surface cannot be accurately represented by the graphic image, and it is difficult to appropriately provide the user with the display of the water surface state and information on the suitability of the cruising.

  Therefore, one of the objects of the present invention is to provide a periphery monitoring device that can appropriately provide a user with a display of a water surface state and information on suitability of cruising (underwater traveling).

  A peripheral monitoring device according to an embodiment of the present invention includes, for example, a control unit that causes a display device to display an image based on captured image data output from an imaging unit that captures an image of a vehicle body surface and a periphery of the vehicle body surface as an imaging range. And an image processing unit for superimposing a water level limit line based on the water level limit information when the vehicle travels over the road, at a corresponding position on the vehicle body surface on the image. According to this configuration, for example, the display device displays an actual image based on the captured image data captured by the imaging unit, and the actual vehicle body surface of the own vehicle and the surrounding conditions during cruising (underwater traveling), that is, the water surface The status (water level, waving condition, etc.) is displayed. Further, the water level limit line is superimposed on a corresponding position on the vehicle body surface on the image. As a result, it is easier to more accurately convey to a user the actual situation, that is, the situation where the water level is located on the vehicle body, and to make it easier for the user to intuitively grasp the situation at the time of crossing traveling.

  In the peripheral monitoring device, for example, the control unit may display an image obtained by correcting the captured image data obtained by capturing the side surface of the vehicle. According to this configuration, for example, the visibility of the screen contents (vehicle side surface and the water level limit line superimposed thereon) is further improved, and the actual situation, that is, the situation where the water level is reached on the vehicle body is improved. Further, it is easy to make the user understand more accurately.

  In the peripheral monitoring device, for example, the control unit may perform a viewpoint conversion process on the captured image data as the correction. According to this configuration, for example, it is possible to provide an image as if the side of the vehicle is viewed from the side of the vehicle, and to provide an image that makes it easier to understand the relationship between the water level limit line and the water surface and the relationship between the water surface and the vehicle body. it can.

  In the peripheral monitoring device, for example, the control unit may perform a distortion correction process on the captured image data as the correction. According to this configuration, for example, it is possible to provide an image in which the shape of the vehicle is more easily recognizable and the relationship between the water level limit line and the water surface and the relationship between the water surface and the vehicle body can be more easily understood.

  In the peripheral monitoring device, for example, the control unit may perform a cutout process of cutting out a part of the captured image data as the correction. According to this configuration, for example, in a vehicle, it is possible to enlarge and display a specific portion of the vehicle in which attention should be paid to the relationship with the water level, and to easily understand the relationship between the vehicle body and the water level limit line and the relationship between the water surface and the vehicle body. Can be provided.

  In the peripheral monitoring device, for example, the water level limit line having a shape along the surface shape of the vehicle may be superimposed on the corresponding position. According to this configuration, for example, a deviation between the surface of the vehicle and the water level limit line is reduced, and an image can be provided that makes it easier to understand the relationship between the water level limit line and the water surface and the relationship between the water surface and the vehicle body.

  In the peripheral monitoring device, for example, the image processing unit may superimpose the linear water level limit line on the corresponding position. According to this configuration, for example, the process of superimposing the water level limit line is facilitated, and the processing load can be reduced. In addition, the water level limit line is simply displayed for the vehicle, and a display that makes it easy to intuitively understand the relationship between the vehicle, the water level limit line, and the water surface can be provided.

  In the peripheral monitoring device, for example, when the water level limit line is displayed, the display area of the vehicle body surface in the image is set to be larger than when the water level limit line is not displayed. Is also good. According to this configuration, for example, the water level limit line superimposed on the vehicle body can be easily recognized, and the fact that the screen is switched to the display mode of the water level limit line can be easily recognized.

  In the peripheral monitoring device, for example, the image processing unit may superimpose a water level reference line at a position lower in the vehicle height direction than the water level limit line superimposed on the image. According to this configuration, the water level reference line can indicate the degree of rise of the water level with respect to the vehicle body in a stepwise manner, so that the water level reference can be alerted stepwise.

  In the peripheral monitoring device, for example, the image processing unit may superimpose the water level reference line in a display mode different from the water level limit line. According to this configuration, it is possible to more clearly alert the user to a rise in the water level by the water level reference line.

FIG. 1 is an exemplary perspective view illustrating an example of a state in which a part of a cabin of a vehicle equipped with the periphery monitoring device according to the embodiment is seen through; FIG. 2 is an exemplary plan view illustrating an example of a vehicle equipped with the periphery monitoring device according to the embodiment. FIG. 3 is an example of a dashboard of a vehicle on which the periphery monitoring device according to the embodiment is mounted, and is a view from the rear of the vehicle. FIG. 4 is a block diagram illustrating an example of an image control system including the periphery monitoring device according to the embodiment. FIG. 5 is an explanatory diagram illustrating a display example of a water level limit line by the periphery monitoring device according to the embodiment. FIG. 6 is an example of display by the periphery monitoring device according to the embodiment, and is an explanatory diagram showing a state in which a water level limit line and a water level reference line are superimposed on an image after distortion correction and viewpoint conversion. FIG. 7 is an example of display by the periphery monitoring device according to the embodiment, and is an explanatory diagram showing a state where a water level limit line and a water level reference line are superimposed on another image after distortion correction and viewpoint conversion. FIG. 8 is a block diagram illustrating an example of a configuration of a CPU for realizing the display of the water level limit line realized in the ECU of the periphery monitoring device according to the embodiment. FIG. 9 is a display example of a display device of the periphery monitoring device according to the embodiment, and is a screen layout and a display example in a standard display mode before displaying a water level limit line. FIG. 10 is a display example of the display device of the periphery monitoring device according to the embodiment, and is a screen layout and a display example in the special display mode after the display of the water level limit line. FIG. 11 is a flowchart illustrating an example of a process of displaying a peripheral monitoring image including a display of a water level limit line by the peripheral monitoring device according to the embodiment.

  Hereinafter, exemplary embodiments of the present invention will be disclosed. The configurations of the embodiments described below, and the operations, results, and effects provided by the configurations are examples. The present invention can be realized by configurations other than those disclosed in the following embodiments, and can obtain at least one of various effects based on the basic configuration and derivative effects. .

  In the present embodiment, the vehicle 1 equipped with the peripheral monitoring device (peripheral monitoring system) may be, for example, an automobile driven by an unillustrated internal combustion engine, that is, an internal combustion engine automobile, or an unillustrated electric motor. The vehicle may be a driving source, that is, an electric vehicle or a fuel cell vehicle. Further, a hybrid vehicle using both of them as drive sources may be used, or a vehicle provided with another drive source may be used. Further, the vehicle 1 can be mounted with various transmissions, and can be mounted with various devices required for driving the internal combustion engine and the electric motor, such as systems and components. In addition, the vehicle 1 preferably travels on so-called “on-roads” (mainly paved roads or equivalent roads), as well as on “off-roads” (mainly unpaved rough roads). A vehicle that can be used. The driving system may be a four-wheel drive vehicle that transmits the driving force to all four wheels 3 and uses all four wheels as driving wheels. The type, number, layout, and the like of the devices related to the driving of the wheels 3 can be variously set. For example, the vehicle may be a vehicle whose main purpose is “on-road” traveling. Further, the drive system is not limited to the four-wheel drive system, and may be, for example, a front-wheel drive system or a rear-wheel drive system.

  As illustrated in FIG. 1, the vehicle body 2 constitutes a vehicle compartment 2 a in which a passenger (not shown) rides. A steering unit 4, an acceleration operation unit 5, a braking operation unit 6, a shift operation unit 7, and the like are provided in the vehicle interior 2a in a state of facing a driver's seat 2b as an occupant. The steering unit 4 is, for example, a steering wheel protruding from the dashboard 24, the acceleration operation unit 5 is, for example, an accelerator pedal positioned below the driver's feet, and the braking operation unit 6 is, for example, a driver's The shift pedal 7 is, for example, a shift lever projecting from the center console. The steering unit 4, the acceleration operation unit 5, the braking operation unit 6, the shift operation unit 7, and the like are not limited to these.

  Further, a display device 8 as a display output unit and an audio output device 9 as an audio output unit are provided in the passenger compartment 2a. The display device 8 is, for example, an LCD (liquid crystal display), an OELD (organic electroluminescent display), or the like. The audio output device 9 is, for example, a speaker. The display device 8 is covered with, for example, a transparent operation input unit 10 such as a touch panel. The occupant can visually recognize an image displayed on the display screen of the display device 8 via the operation input unit 10. Further, the occupant can execute the operation input by operating the operation input unit 10 by touching, pushing, or moving the operation input unit 10 with a finger or the like at a position corresponding to the image displayed on the display screen of the display device 8. . The display device 8, the audio output device 9, the operation input unit 10, and the like are provided, for example, on the monitor device 11 located at the center of the dashboard 24 in the vehicle width direction, that is, in the left-right direction. The monitor device 11 can include an operation input unit (not shown) such as a switch, a dial, a joystick, and a push button. An audio output device (not shown) can be provided at another position in the passenger compartment 2a different from the monitor device 11, and audio is output from the audio output device 9 of the monitor device 11 and another audio output device. be able to. Note that the monitor device 11 can also be used, for example, as a navigation system or an audio system.

  Further, a display device 12 different from the display device 8 is provided in the passenger compartment 2a. As illustrated in FIG. 3, the display device 12 is provided on, for example, an instrument panel 25 of the dashboard 24, and is provided at a substantially center of the instrument panel 25 between a speed display unit 25 a and a rotation speed display unit 25 b. It is located in. The size of the screen 12a of the display device 12 is smaller than the size of the screen 8a (FIG. 3) of the display device 8. On the display device 12, for example, an indicator, a mark, or an image showing character information can be displayed as auxiliary information when peripheral monitoring of the vehicle 1 and other functions are operating. The amount of information displayed on the display device 12 may be smaller than the amount of information displayed on the display device 8. The display device 12 is, for example, an LCD, an OELD, or the like. The information displayed on the display device 12 may be displayed on the display device 8.

  Further, as exemplified in FIGS. 1 and 2, the vehicle 1 is, for example, a four-wheeled vehicle, and has two left and right front wheels 3F and two left and right rear wheels 3R. Each of these four wheels 3 can be configured to be steerable. As illustrated in FIG. 4, the vehicle 1 has a steering system 13 that steers at least two wheels 3. The steering system 13 has an actuator 13a and a torque sensor 13b. The steering system 13 is electrically controlled by an ECU 14 (electronic control unit) or the like to operate the actuator 13a. The steering system 13 is, for example, an electric power steering system, an SBW (steer by wire) system, or the like. Further, the torque sensor 13b detects, for example, a torque given to the steering unit 4 by the driver.

  Further, as illustrated in FIG. 2, the vehicle body 2 is provided with, for example, four imaging units 15 a to 15 d as the plurality of imaging units 15. The imaging unit 15 is, for example, a digital camera having a built-in imaging device such as a charge coupled device (CCD) or a CMOS image sensor (CIS). The imaging unit 15 can output moving image data (captured image data) at a predetermined frame rate. Each of the imaging units 15 has a wide-angle lens or a fisheye lens, and can capture, for example, a range of 140 ° to 220 ° in the horizontal direction. The optical axis of the imaging unit 15 may be set obliquely downward. Therefore, the image capturing unit 15 is capable of moving the vehicle 1 on a road surface, a water surface during cruising, surrounding conditions (the presence or absence of water, a state of the water surface, a height to the water surface, etc.) and an object (for example, as an obstacle, An external environment around the vehicle 1 including rocks, trees, people, bicycles, vehicles, etc.) is sequentially photographed and output as captured image data.

  The imaging unit 15a is located, for example, at the rear end 2e of the vehicle body 2, and is provided on a wall below the rear window of the door 2h of the rear hatch. The imaging unit 15b is located, for example, at the right end 2f of the vehicle body 2 and is provided on the right door mirror 2g. The imaging unit 15c is located, for example, at the front side of the vehicle body 2, that is, at the front end 2c in the front-rear direction of the vehicle, and is provided on a front bumper, a front grill, and the like. The imaging unit 15d is located, for example, on the left side of the vehicle body 2, that is, on the left end 2d in the vehicle width direction, and is provided on the left side door mirror 2g. The ECU 14 performs arithmetic processing and image processing based on the captured image data obtained by the plurality of imaging units 15 to generate an image with a wider viewing angle, or a virtual overhead image of the vehicle 1 viewed from above. Or can be generated. Further, the ECU 14 performs a distortion correction process for correcting distortion by performing arithmetic processing or image processing on the wide-angle image data (curved image data) obtained by the imaging unit 15 or an image obtained by cutting out a specific area. Or an extraction process for generating image data indicating only a specific area. In addition, the ECU 14 can execute a viewpoint conversion process of converting captured image data into virtual image data as if the image was captured from a virtual viewpoint different from the viewpoint captured by the imaging unit 15. For example, the image data is converted into virtual image data indicating an overhead view image of the vehicle 1 as viewed from above, or is converted into virtual image data indicating a side view image of the side of the vehicle 1 viewed from a position away from the vehicle 1. Or you can. The ECU 14 displays the acquired image data on the display device 8, for example, to confirm the safety of the right side and the left side of the vehicle 1, check the water level at the time of traversing running described later, look down at the vehicle 1, and Provide perimeter monitoring information so that safety checks can be performed.

  In addition, the ECU 14 displays the state of the water surface and a part of the vehicle body 2 and displays the relationship between the vehicle 1 and the water surface during the cruising traveling, and performs the cruising traveling support (underwater traveling support). Can also. In this case, the ECU 14 can display an image in which a water level limit line, a water level reference line, and the like are superimposed on a part of the vehicle 1, for example, a side surface of the vehicle body 2, as described later. The ECU 14 identifies the lane markings and the like indicated on the road surface around the vehicle 1 from the captured image data provided by the imaging unit 15 and performs driving assistance, or detects (extracts) a parking lane to park the vehicle. Or provide assistance.

  As illustrated in FIGS. 1 and 2, the vehicle body 2 is provided with a plurality of distance measuring units 16 and 17, for example, four distance measuring units 16 a to 16 d and eight distance measuring units 17 a to 17 h. ing. The distance measuring units 16 and 17 are, for example, sonars that emit ultrasonic waves and capture reflected waves. The sonar can also be called a sonar sensor, an ultrasonic detector, or an ultrasonic sonar. In the present embodiment, the distance measuring units 16 and 17 are provided at lower positions in the vehicle height direction of the vehicle 1, for example, front and rear bumpers, detect obstacles around the vehicle 1, for example, and determine the distance to the obstacle. Can be measured. Further, the distance measuring units 16 and 17 can be used as sensors for determining whether or not the vehicle 1 is in an underwater approach (running) state. As described above, since the distance measuring units 16 and 17 are provided on the front and rear bumpers which are low positions in the vehicle height direction of the vehicle 1, when performing crossing traveling, the water level is such that the water level becomes incapable of crossing traveling ( Submergence at a relatively early stage before reaching the height at which the water level limit line is superimposed). For example, when the distance measuring units 16 and 17 are submerged, the reception state of the reflected wave becomes unstable, and an operation error occurs. Therefore, when the vehicle 1 enters a river or swamp and is submerged, an error signal can be output from the plurality of distance measuring units 16 and 17 almost simultaneously. For example, when the vehicle 1 enters a river or swamp while traveling forward, the distance measuring units 17e, 17f, 17g, and 17h are submerged almost simultaneously and output an error signal, and subsequently, the distance measuring units 16c and 16d output an error signal. Outputs an error signal. Similarly, when the vehicle 1 enters a river or swamp while traveling backward, the distance measuring units 17a, 17b, 17c, and 17d are submerged almost simultaneously and output an error signal, and subsequently, the distance measuring units 16a and 16b Outputs an error signal. That is, it is possible to obtain information for determining whether or not the vehicle 1 is in the traveling mode based on the output mode of the error signal from the distance measuring units 16 and 17. When the vehicle 1 has completed the cruising run (when it has landed), when the vehicle 1 escapes from a river or swamp while traveling forward, the distance measuring units 17e, 17f, 17g, and 17h return almost simultaneously, and subsequently, Thus, the distance measuring units 16c and 16d return. When the landing further proceeds, the distance measuring units 16a and 16b return, and finally, the distance measuring units 17a, 17b, 17c, and 17d return almost simultaneously. Thus, when all the distance measuring units 16 and 17 return, information for determining that the vehicle 1 has escaped from the cruising traveling (complete landing) can be obtained. Note that the distance measuring units 16 and 17 have a waterproof structure, and are configured so as not to be damaged by water immersion.

  As illustrated in FIG. 4, in the periphery monitoring system 100 (perimeter monitoring device), in addition to the ECU 14, the monitor device 11, the steering system 13, the distance measuring units 16 and 17, a brake system 18, a steering angle sensor 19, an accelerator sensor 20, a shift sensor 21, a wheel speed sensor 22, an acceleration sensor 26 and the like are electrically connected via an in-vehicle network 23 as an electric communication line. The in-vehicle network 23 is configured as, for example, a CAN (controller area network). The ECU 14 can control the steering system 13, the brake system 18, and the like by sending a control signal through the in-vehicle network 23. The ECU 14 also controls the torque sensor 13b, the brake sensor 18b, the steering angle sensor 19, the distance measuring unit 16, the distance measuring unit 17, the accelerator sensor 20, the shift sensor 21, the wheel speed sensor 22, and the acceleration sensor via the in-vehicle network 23. It can receive a detection result such as 26, an operation signal from the operation input unit 10, and the like.

  The ECU 14 includes, for example, a CPU 14a (central processing unit), a ROM 14b (read only memory), a RAM 14c (random access memory), a display control unit 14d, a voice control unit 14e, an SSD 14f (solid state drive, flash memory), and the like. ing. The CPU 14a can execute, for example, arithmetic processing and control of image processing related to images displayed on the display devices 8 and 12. For example, it executes processing and calculation for displaying an image in the standard display mode displayed during land traveling, an image in the special display mode displayed during crossing traveling, and the like. In addition, the CPU 14a determines a movement target position (a parking target position, a target position) of the vehicle 1, calculates a guidance route (a guidance route, a parking route, a parking guidance route) of the vehicle 1, and determines whether or not there is interference with an object. Various types of arithmetic processing and control, such as automatic control of the vehicle 1 and release of the automatic control, can be performed.

  The CPU 14a reads a program installed and stored in a non-volatile storage device such as the ROM 14b, and can execute arithmetic processing according to the program. The RAM 14c temporarily stores various data used in the calculation by the CPU 14a. In addition, the display control unit 14d mainly performs, for example, synthesis of image data displayed on the display device 8 in the arithmetic processing performed by the ECU 14. In addition, the voice control unit 14 e mainly performs processing of voice data output from the voice output device 9 in the arithmetic processing in the ECU 14. The SSD 14f is a rewritable nonvolatile storage unit, and can store data even when the power of the ECU 14 is turned off. Note that the CPU 14a, the ROM 14b, the RAM 14c, and the like can be integrated in the same package. Further, the ECU 14 may be configured to use another logical operation processor, a logical circuit, or the like, such as a DSP (digital signal processor), instead of the CPU 14a. Further, a hard disk drive (HDD) may be provided instead of the SSD 14f, and the SSD 14f and the HDD may be provided separately from the ECU 14.

  The brake system 18 includes, for example, an anti-lock brake system (ABS) that suppresses lock of the brake, an electronic stability control (ESC) that suppresses a side slip of the vehicle 1 at the time of cornering, and increases the braking force ( Electric brake system for executing brake assist), BBW (brake by wire) and the like. The brake system 18 applies a braking force to the wheels 3 and thus to the vehicle 1 via the actuator 18a. In addition, the brake system 18 can execute various controls by detecting a lock of a brake, an idling of the wheel 3, a sign of a skid, or the like based on a rotation difference between the left and right wheels 3 and the like. The brake sensor 18b is, for example, a sensor that detects the position of the movable part of the braking operation unit 6.

  The steering angle sensor 19 is, for example, a sensor that detects a steering amount of the steering unit 4 such as a steering wheel. The ECU 14 obtains, from the steering angle sensor 19, the amount of steering of the steering unit 4 by the driver, the amount of steering of each wheel 3 during automatic steering, and executes various controls. The accelerator sensor 20 is, for example, a sensor that detects the position of the movable part of the acceleration operation unit 5. The shift sensor 21 is, for example, a sensor that detects the position of the movable part of the speed change operation unit 7. The wheel speed sensor 22 is a sensor that detects the amount of rotation of the wheel 3 and the number of rotations per unit time. The wheel speed sensor 22 outputs a wheel speed pulse number indicating the detected rotation speed as a sensor value. The ECU 14 calculates the amount of movement of the vehicle 1 and the like based on the sensor values acquired from the wheel speed sensors 22 and executes various controls. In the present embodiment, it is assumed that the vehicle 1 is provided with two acceleration sensors 26 (26a, 26b). When the vehicle 1 is equipped with an ESC, the acceleration sensors 26 (26a, 26b) conventionally mounted on the ESC are used. In the present embodiment, the acceleration sensor is not limited, and may be any sensor that can detect the acceleration of the vehicle 1 in the left-right direction. In the present embodiment, the longitudinal acceleration and the lateral acceleration are derived.

  The configuration, arrangement, electrical connection form, and the like of the various sensors and actuators described above are merely examples, and can be set (changed) in various ways.

  As an example, the ECU 14 that implements the periphery monitoring system 100 uses the real image based on the captured image data captured by the imaging unit 15 when the vehicle 1 crosses and travels to determine the water surface around the vehicle 1 and the “water level limit line”. The superimposed relationship with the vehicle body 2 is displayed on the display device 8. In this case, the captured image data captured by the imaging unit 15 is data obtained by capturing the surface of the vehicle body 2 of the vehicle 1 and the periphery of the surface as an imaging range. Here, the “water level limit line” refers to a water level at which a function provided in the vehicle 1 such as a running function can be normally operated even when the vehicle 1 is submerged, and a water level in the vehicle compartment 2a can be prevented. This is an index that indicates the limit of the water level.

  5 to 7 are explanatory diagrams illustrating a state in which the “water level limit line L” is superimposed on an image based on the captured image data. The “water level limit line L” is a line that is set, for example, at a position of 600 mm in the vehicle height direction from the ground position of the wheel 3, and is a height at which a waterproofing process, a water stopping process, and the like are performed at the design stage of the vehicle 1. And the height set in advance according to the driving performance of the vehicle 1 and the like. The “water level limit line L” can be superimposed and displayed, for example, along the body side surface 2m (along the curved surface of the body 2) among the bodies 2 included in the image based on the captured image data captured by the imaging unit 15. . For example, when the body side surface 2m is a curved surface, it is desirable that the water level limit line L also be shaped (curved) along the surface shape (horizontal cross-sectional shape) of the vehicle 1. The water level limit line L is superimposed within the range of the vehicle body 2. In this case, the water level limit line L is superimposed including the wheel 3 portion. In this way, by making the water level limit line L overlap the body side surface 2m and within the range of the vehicle body 2, it is possible to make it easy for the user to recognize the position of the water level rising to the vehicle body 2 without a sense of incongruity.

  As described above, the imaging unit 15b and the imaging unit 15d having the wide-angle lens or the fisheye lens are fixed to the door mirror 2g. Therefore, the imaging unit 15b and the imaging unit 15d use a part of the body side surface 2m of the vehicle 1 (including the front wheel 3F and the rear wheel 3R) and a landscape on the side thereof as an imaging range. In other words, when the vehicle 1 enters underwater such as a river, a swamp, or a flooded channel, an image can be obtained in which the body side surface 2m of the vehicle 1 and the water surface that has risen due to entering the water are contained in the same screen. . Then, the ECU 14 displays, on the display device 8, an image in which the “water level limit line L” is superimposed and displayed on the body side surface 2 m of the vehicle 1 displayed together with the water surface, so that the vehicle 1 is in a submerged state and a submerged state while the vehicle 1 is traveling. Can be visually confirmed by the user (driver or the like). In addition, since the water surface is displayed as an actual image on the screen, it is possible to make it easy for the user to intuitively grasp the change in the water level. In this case, since the image to be displayed is a real image, even when the water surface is wavy, it is possible for the user to recognize the change in the water surface in real time, and it is easy to more appropriately determine the situation at the time of crossing traveling. be able to.

  The ECU 14 may superimpose the “water level reference line K” at a position lower in the vehicle height direction than the “water level limit line L” as an index similar to the “water level limit line L” as shown in FIGS. it can. The “water level reference line K” is an index line superimposed substantially in parallel with the water level limit line L and not reaching the water level limit line L but notifying the user of a rise in water level in advance. When two “water level reference lines K” are superimposed, for example, one is “400 mm below the“ water level limit line L ”, that is, 200 mm from the ground contact surface of the wheel 3 as the“ first water level reference line K1 ”. Superimposed. The other is superimposed as a “second water level reference line K2” at, for example, 200 mm below the “water level limit line L”, that is, 400 mm from the ground surface of the wheel 3. By providing the “water level reference line K” in this manner, the degree of rise of the water level with respect to the vehicle body 2 can be indicated in a stepwise manner, so that a stepwise alert for the water level rise can be given. Note that whether or not the “water level reference line K” is displayed may be made selectable by the user. Further, the number of the “water level reference lines K” and the overlapping position (the height of the wheels 3 from the ground contact position) can be set as appropriate.

  As shown in FIG. 8, the CPU 14 a included in the ECU 14 includes the image acquisition unit 30 and the display processing unit 32 (FIG. 8) in order to provide an image including the “water level limit line L” during the cruising traveling as described above. Control unit), an image processing unit 34, and an output unit 36. The display processing unit 32 includes a distortion correction unit 38, a viewpoint conversion unit 40, and a layout adjustment unit 42, and the image processing unit 34 includes a water level limit line superimposition unit 44 and a water level reference line superimposition unit 46. The image acquisition unit 30, the display processing unit 32, the image processing unit 34, the output unit 36, the distortion correction unit 38, the viewpoint conversion unit 40, the layout adjustment unit 42, the water level limit line superimposition unit 44, and the water level reference line superimposition unit 46 are stored in the ROM 14b. It can be realized by reading out a program installed and stored in a storage device such as, and executing the program.

  The image acquisition unit 30 acquires the captured image data output from the imaging unit 15 that is provided in the vehicle 1 and captures the periphery of the vehicle 1 via the display control unit 14d. The display control unit 14d may output the captured image data captured by the image capturing unit 15 to the display device 8 or the display device 12 as it is, without going through the processing by the CPU 14a. Further, the CPU 14a may allow the user to select desired display content using an input device such as the operation input unit 10 or the operation unit 14g. That is, the display control unit 14d can selectively display the image selected by the operation of the operation input unit 10 or the operation unit 14g on the display device 8. For example, the rear image of the vehicle 1 captured by the imaging unit 15a can be displayed on the display device 8, and the left image captured by the imaging unit 15d can be displayed on the display device 8.

  The display processing unit 32 performs various types of image processing on the captured image data output from the imaging unit 15 that captures the surface of the vehicle body 2 of the vehicle 1 and the periphery of the surface as an imaging range, and generates an image based on the captured image data. The image is converted into an image in which the water level limit line L and the “water level reference line K” are easily recognizable and displayed on the display device 8.

  For example, the distortion correction unit 38 performs a known distortion correction process on captured image data or an image based on the captured image data. As described above, when the imaging unit 15b and the imaging unit 15d include the wide-angle lens or the fisheye lens, the original image based on the captured image data is a curved image as illustrated in FIG. In this case, the curved image is an image including the vehicle 1 and a wide range of conditions in front, behind, and side of the vehicle 1 in the imaging range. That is, it is possible to provide an image that allows the user to easily grasp the situation of the vehicle 1 and the entire surroundings of the vehicle 1. On the other hand, a user unfamiliar with the curved image may take a long time to understand the displayed contents. Further, since the “water level limit line L”, which should be close to a straight line, is curved, it may give a sense of incongruity. Therefore, the distortion correction unit 38 (CPU 14a) corrects the image data obtained by imaging the side surface of the vehicle 1 by giving a displacement amount corresponding to the pixel position, based on the correction information stored in the ROM 14b, for example. A process for relaxing or removing the curvature is performed. As a result, the shape of the vehicle 1 displayed on the display device 8 can be approximated to the actual shape, and the user can more easily understand the display contents.

  The viewpoint conversion unit 40 performs a known viewpoint conversion process on captured image data or an image based on the captured image data. For example, in order to make it easier for the user to understand the relationship between the “water level limit line L” or the “water level reference line K” superimposed on the body side surface 2m of the vehicle body 2 and the water surface W (water surface line), the water level limit line L It is desirable to provide an image in which the line of sight is directed from a direction in which the surface of the vehicle body 2 on which the water level reference line K is superimposed (for example, the body side surface 2m) is easily viewed. For example, as shown in FIGS. 6 and 7, the converted image faces the body side surface 2m from a position separated from the body side surface 2m, and shows the vicinity of a contact portion (water surface line) between the body side surface 2m and the water surface W. It is assumed that the image is obtained by looking down. As a result, in the converted image, the relationship between the body side surface 2m and the water surface W can be more easily understood. The viewpoint conversion unit 40 (CPU 14a) separates the vehicle 1 from the vehicle 1 by applying conversion information of a mapping table held in, for example, the ROM 14b to captured image data obtained by capturing the side surface of the vehicle 1. It generates virtual image data (viewpoint conversion image) when viewed from the viewpoint point of view. 6 and 7 show examples in which distortion correction and viewpoint conversion processing are performed on an image based on captured image data, but the distortion correction processing may be omitted and the viewpoint conversion processing may be executed. In this case, the image as shown in FIG. 5 is an image viewed from a position separated from the body side surface 2m. The viewpoint conversion unit 40 may perform distortion correction during the viewpoint conversion processing. Further, the distortion correction unit 38 and the viewpoint conversion unit 40 may be configured collectively as an image conversion unit.

  The viewpoint conversion unit 40 can appropriately set the position of the viewpoint. For example, as shown in FIG. 6, the viewpoint may be set at a position separated from the body side surface 2m at a substantially central portion of the body side surface 2m, and may be a line-of-sight conversion image facing the front side of the vehicle 1. In addition, as shown in FIG. 7, the viewpoint conversion unit 40 sets the viewpoint at a position substantially apart from the body side surface 2m at a substantially central portion of the body side surface 2m, and converts the viewpoint conversion image to look at the body side surface 2m of the vehicle 1. Is also good. Similarly, the line-of-sight conversion image may be such that the rear side of the vehicle 1 is viewed from substantially the center of the side surface 2m of the body. In this case, a cutout process for appropriately cutting out a part of the image based on the captured image data may be performed. In this way, by making it possible to appropriately change the viewpoint position or to make it possible to appropriately enlarge the display by cutting out processing, the water level limit line L (water level reference line K) and the water surface W of the part that the user wants to pay attention to are displayed. It is possible to provide an image indicating the relationship, and it is easier to recognize the crossing traveling state. Further, for example, when displaying an image facing the body side surface 2m as shown in FIG. 7, an image facing the body side surface 2m opposite to the driver's seat side may be displayed on the display device 8. In this case, the driver can visually check the body side 2m on the driver's seat side, and can confirm the opposite body side 2m on the display device 8. These viewpoint switching can be selected by, for example, an input from the operation input unit 10 or the operation unit 14g.

  The layout adjustment unit 42 adjusts (changes) the layout of the screen displayed on the display device 8. As shown in FIG. 9, the ECU 14 divides the display area of the display device 8 into a plurality of parts, and displays images in various directions, an inclinometer 50 indicating the attitude of the vehicle 1, and the like as a driving assistance screen normally displayed on the display device 8. Is displayed. FIG. 9 is an image example in the standard display mode displayed when the vehicle 1 is traveling on land. In this case, as a standard display mode, the layout adjustment unit 42 arranges, for example, a front display area FV in the upper center of the display area of the display device 8, and arranges a left display area SVL and a right display area SVR to the left and right thereof. Further, an attitude display area PV for displaying the inclinometer 50 is arranged below the front display area FV. When traveling on land, the front display area FV includes, as necessary, a course index R indicating the estimated traveling direction of the vehicle 1 and a front reference line Qa indicating a measure of the distance from the front end 2c of the vehicle body 2. Alternatively, a lateral reference line Pa or the like that indicates a measure of the distance from the lateral ends 2d and 2f of the vehicle body 2 may be displayed to provide driving assistance. In the left display area SVL and the right display area SVR, the vehicle body 2 and the road surface are displayed as images in which distortion has been corrected and distortion has been reduced. In the standard display mode in which the display is mainly performed during land running, the layout adjustment unit 42 displays the vehicle body 2 and the road surface more in the left display area SVL and the right display area SVR on the road surface. That is, in the case of the standard display mode, the left display area SVL and the right display area SVR display an image that makes it easier to grasp the road surface condition around the front wheel 3F. The inclinometer 50 displays the inclination of the vehicle 1 in the left-right direction (roll angle) and the inclination in the front-rear direction (pitch angle) based on the signal from the acceleration sensor 26 (26a, 26b) in the posture of the symbol 52.

  In addition, the layout adjustment unit 42 can change the display content (layout change) so that the relationship between the water level limit line L or the water level reference line K and the water surface W can be more easily understood during crossing traveling. FIG. 10 is an example of an image in the special display mode that is displayed when the vehicle is traveling with a driver. In the case of FIG. 10, the layout of the front display area FV, the left display area SVL, the right display area SVR, and the posture display area PV is the same as that during land running in FIG. 9, but the left display area SVL and the right display area The internal layout of the SVR is different from that of FIG. As shown in FIG. 10, in the special display mode in which the water level limit line L (water level reference line K) is displayed, the display area on the surface of the vehicle body 2 in the image displayed in the left display area SVL and the right display area SVR. Is larger than when the water level limit line L (water level reference line K) is not displayed. In the special display mode, the display mainly shows how much the water surface W has risen with respect to the water level limit line L (the water level reference line K). Therefore, in the special display mode, the display area of the body side surface 2m in the left display area SVL and the right display area SVR is increased. By changing the layout in the image in this way, the visibility of the relationship between the water level limit line L (water level reference line K) and the water surface W can be improved. Further, it is possible to make it easy to recognize that the screen of the display device 8 has been switched to the display mode of the water level limit line L. Note that the captured image data captured by the image capturing unit 15 is set to an area larger than the area displayed in the left display area SVL or the right display area SVR as an imaging range, for example, by performing cutout processing therefrom to obtain the left display area SVL. And in the right display area SVR. Therefore. Enlarging the display area on the surface of the vehicle body 2 can be performed, for example, by adjusting the cutout range from the original image. Further, in another embodiment, the water level limit line L (water level reference line K) may be displayed while the display area on the surface of the vehicle body 2 is kept in FIG.

  Further, the layout adjustment unit 42 changes the layout and uses the entire display area of the display device 8 to display an image showing the relationship between the water level limit line L (water level reference line K) and the water surface W as shown in FIGS. May be displayed. By performing such display, the visibility of the relationship between the water level limit line L (the water level reference line K) and the water surface W is further improved, and the water level limit line L (the water level reference line K) and the water surface W are displayed to the user. Can be emphasized to give particular attention to the relationship.

  The image processing unit 34 performs a process of superimposing the water level limit line L and the water level reference line K based on the water level limit information when the vehicle 1 crosses the road, at the corresponding position of the surface of the vehicle body 2 on the image displayed on the display device 8. . The water level limit information is, for example, information for superimposing a water level limit line L or a water level reference line K on an image, and may be information specifying an image on the image, or a reference line, for example, from a ground contact position of the wheel 3. Height information or the like may be used. When the conditions for displaying the water level limit line L are met, the CPU 14a superimposes the water level limit line L on the position of the height determined in the vehicle height direction at the stage of designing the vehicle 1. As described above, each imaging unit 15 is fixed to the vehicle body 2 and an imaging range is determined. Therefore, since it is possible to calculate where in the display range the vehicle body 2 is displayed in the captured image data or the image based on the captured image data, the water level limit line L is superimposed on the position. Similarly, the water level reference line superimposing unit 46 superimposes the water level reference line K at a height position determined in the vehicle height direction at the stage of designing the vehicle 1. It should be noted that the water level limit line superimposing section 44 and the water level reference line superimposing section 46 have different displays so that the water level limit line L and the water level reference line K (the first water level reference line K1 and the second water level reference line K2) can be easily identified. It may overlap in an aspect. For example, the line type and line color can be changed. When a line color is selected, it is desirable that the line color be a color that can be identified from the color of the vehicle body 2. For example, the water level limit line superimposing section 44 and the water level reference line superimposing section 46 may acquire color information of the vehicle body 2 and automatically select an identifiable line color, or may allow the user to select. Good. When the water level limit line superimposing section 44 superimposes and displays the water level limit line L, as shown in FIGS. 6 and 7, information indicating the water level limit line L, for example, a “mark” such as an arrow or the like. “Character information” such as Limit may be added. In addition, when adding “mark” or “text information”, it is superimposed on the upper side of the water level limit line L so that even when the water surface W rises, the “mark” or “text information” is easily visible. Is desirable. When the water level reference line K is superimposed by the water level reference line superimposing unit 46, “mark” and “character information” may be added in the same manner. 6 and 7, the water level reference line K has been described as an example in which the water level reference line K is superimposed in parallel with the water level limit line L. However, the water level reference line K is superimposed in a direction orthogonal to the water level limit line L, and the water depth is determined. It may be displayed together with the scale shown.

  The CPU 14a performs a manual operation by the user to determine whether or not the water level limit line L (the water level reference line K) is displayed, for example, switching from the display state of FIG. 9 to the display state of FIG. 10 and vice versa. It may be performed by an input operation by the user 10 or the operation unit 14g. Further, as described above, the switching may be performed according to the operation state (the output state of the error signal) of the distance measuring sections 16 and 17. In addition, the switching operation may be performed using input means such as voice recognition or gesture recognition.

  A control example of the periphery monitoring system 100 thus configured will be described with reference to a flowchart of FIG. Note that the flow illustrated in FIG. 11 is repeatedly executed at a predetermined processing cycle.

  First, the CPU 14a determines whether peripheral monitoring is currently being performed (S100), and if peripheral monitoring is not currently being performed (No in S100), for example, when the power of the vehicle 1 is OFF, or when the display device 8 is used for another purpose (navigation or If it is used for audio, etc., the flow is once ended. On the other hand, when the CPU 14a determines that the surrounding area is currently being monitored (Yes in S100), the CPU 14a determines whether the crossing traveling mode switching condition is satisfied (S102). As described above, the CPU 14a determines that the crossover traveling mode switching condition is satisfied when the input operation is performed by the operation input unit 10 or the operation unit 14g. Further, the CPU 14a determines whether the distance measuring unit 16 or the distance measuring unit 17 outputs an error signal in a predetermined pattern, for example, when the distance measuring units 17e to 17h output the error signal almost simultaneously (for example, within 2 seconds). It is considered that the traveling mode switching condition has been satisfied.

  In S102, when the crossing traveling mode switching condition is satisfied (Yes in S102), the CPU 14a acquires the captured image data currently captured by the imaging unit 15, for example, the side image of the vehicle 1, via the image acquisition unit 30. (S104). Subsequently, the CPU 14a performs an image conversion process on the acquired side image (S106). In the image conversion processing, at least one of the distortion correction processing by the distortion correction unit 38 and the viewpoint conversion processing by the viewpoint conversion unit 40 is executed based on the setting of the mode of the display image by the user. In the case where the water level limit line L and the like are superimposed on the original image shown in FIG. 5 according to the selection or setting by the user, the process of S106 may be skipped.

  Subsequently, the CPU 14a superimposes the “water level limit line L” on the body side surface 2m of the vehicle body 2 by the water level limit line superimposing section 44, and the “water level reference line K” by the water level reference line superimposing section 46. It overlaps with 2m (S108). In this case, the “water level reference line K” may be hidden by selection or setting by the user. By hiding the “water level reference line K”, it is possible to simplify the image on which the water level limit line L is superimposed. That is, a display corresponding to a user who prefers a simple display can be performed.

  Subsequently, when switching from the screen in the standard display mode of FIG. 9 displayed as the surroundings monitoring screen to the screen in the traveling mode, the layout adjustment unit 42 determines whether the screen in the traveling mode is designated as the main screen. Is checked (S110). For example, when “main display” is selected by an input operation using the operation input unit 10 or the operation unit 14g (Yes in S110), the layout adjustment unit 42 switches from the standard display mode screen of FIG. Is switched to a screen that emphasizes the relationship between the water level limit line L (water level reference line K) and the water surface W as shown by, and a process of displaying (main display) using the entire display area of the display device 8 is executed. (S112).

  On the other hand, when the main display selection has not been performed (No in S110), the layout adjustment unit 42, as shown in FIG. 10, displays the surface of the vehicle body 2 in the image displayed in the left display area SVL and the right display area SVR. The display area is switched to the special display mode in which the water level limit line L (the water level reference line K) is larger than the non-display state and the display area is displayed on the display device 8 (S114).

  The CPU 14a determines whether the mode return condition for returning from the cruising traveling mode to the land traveling mode is satisfied while the display in the cruising traveling mode indicating the relationship between the water level limit line L (the water level reference line K) and the water surface W is being performed. It is confirmed whether or not it is (S116). In the case of the manual return, the CPU 14a regards that the mode return condition is satisfied when a user requests a screen return (a screen display request in the land traveling mode) by an input operation via the operation input unit 10 or the operation unit 14g. . In the case of automatic return, the CPU 14a determines that the distance measuring unit 16 and the distance measuring unit 17 have all returned (when all error signals have been eliminated by landing) and that a predetermined period of time, for example, 5 seconds, has elapsed. It is assumed that the mode return condition has been satisfied. When the mode return condition is satisfied (Yes in S116), the layout adjustment unit 42 returns the image displayed on the display device 8 to the image in the standard display mode (the screen in FIG. 9) (S118), and performs a series of crossing traveling. The display process of the water level limit line L (water level reference line K) in the mode ends.

  In S116, when the mode return condition is not satisfied (No in S116), the CPU 14a shifts to S104 and executes the processing of S104 and thereafter to sequentially update the display images during the crossing travel. The change in the relationship between the change in the water surface W (change in the water level) and the water level limit line L (the water level reference line K) is displayed on the display device 8 in real time. Further, in S102, when the traveling mode switching condition is not satisfied (No in S102), that is, when the display of the water level limit line L (the water level reference line K) is unnecessary, the process proceeds to S118, and the standard display mode is set. The process of displaying the screen on the display device 8 is continued.

  As described above, according to the periphery monitoring system 100 of the present embodiment, the display device 8 displays the actual image based on the image data captured by the imaging unit 15, and displays the actual surface of the vehicle body 2 of the vehicle 1 and the interference. The area around the vehicle, that is, the water surface W, is displayed. Further, the water level limit line L is superimposed on a corresponding position on the surface of the vehicle body 2 on the image. As a result, the actual situation, that is, about where the water surface W is formed on the vehicle body 2 and the state of the water surface are more accurately conveyed, and the user is intuitively informed of the information. It is possible to make it easier to grasp.

  In the case of the above-described embodiment, an example is shown in which the water level limit line L and the water level reference line K are superimposed on the body side surface 2m based on image data captured by the imaging unit 15b or the imaging unit 15d provided on the door mirror 2g. . In another embodiment, image data captured by another imaging unit 15 may be used. For example, when the imaging range of the imaging unit 15c provided at the front part of the vehicle body 2 includes the front part (the front surface of the body) of the vehicle body 2, the water level limit line L and the water level reference line K are superimposed and displayed on the image of the front surface of the body. The information may be displayed in the front display area FV of the device 8. In this case, when the vehicle 1 is moved forward, a change in the water level with respect to the vehicle body 2 can be easily grasped. Similarly, when the rear of the vehicle body 2 (rear surface of the body) is included in the imaging range of the imaging unit 15a provided at the rear of the vehicle body 2, the water level limit line L and the water level reference line K are superimposed on the image of the rear surface of the body. 8 may be displayed. In this case, the preceding and following images may be switched based on the shift position of the shift operation section 7 (shift lever). Alternatively, the display area of the display device 8 may be divided into four parts, and the water level limit line L (water level reference line K) may be superimposed and displayed on the front, rear, left, and right images. In this case, since the relationship between the water surface W and the water level limit line L (water level reference line K) can be shown with respect to the entire circumference of the vehicle 1, for example, in the case where the unevenness of the water bottom is large and the vehicle 1 is greatly inclined. However, the user can easily understand the relationship between the water level limit line L (water level reference line K) and the water surface W.

  In the present embodiment, an example has been described in which the water level limit line L and the water level reference line K are superimposed along the body side surface 2m. That is, when the body side surface 2m is a curved surface, the water level limit line L and the water level reference line K are also superimposed so as to correspond to the curved surface, but are not limited thereto. For example, when distortion correction is performed on the captured image data or an image based on the captured image data to approximate the actual shape of the vehicle 1, the water level limit line L and the water level reference line K are superimposed in the front-rear direction of the vehicle body 2. Since the shape is a linear shape, the water level limit line L and the water level reference line K may be simply represented by a straight line. In this case, the image processing load on the ECU 14 can be reduced. In addition, since the water level limit line L and the water level reference line K are displayed as simple straight lines, the relationship with the water surface can be easily understood intuitively.

  In the above-described embodiment, a so-called off-road vehicle has been described. However, the periphery monitoring device according to the present embodiment can be applied to a so-called on-road vehicle (passenger car or the like), and similar effects can be obtained. Further, by processing the image on which the water level reference line K and the water level limit line L are superimposed, the position of the water surface W with respect to the water level reference line K and the water level limit line L is detected, and a warning message such as a voice is output. It may be.

  Further, in the above-described embodiment, an example in which the signals from the distance measuring units 16 and 17 are used when automatically switching to the cruising traveling mode (underwater traveling mode) is used. Switching may be performed using a signal from a sensor. Further, the water surface W may be detected and switched based on the image captured by the imaging unit 15. Further, the mode switching may be performed only manually.

  Although the embodiment and the modification of the present invention have been described, the embodiment and the modification are presented as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in other various forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and their equivalents.

  DESCRIPTION OF SYMBOLS 1 ... Vehicle, 2 ... Body, 2m ... Body side surface, 8 ... Display device, 14 ... ECU, 14a ... CPU, 14b ... ROM, 14d ... Display control part, 14g ... Operation part, 15, 15a, 15b, 15c, 15d ... Imaging unit, 30 ... Image acquisition unit, 32 ... Display processing unit, 34 ... Image processing unit, 36 ... Output unit, 38 ... Distortion correction unit, 40 ... Viewpoint conversion unit, 42 ... Layout adjustment unit, 44 ... Water level limit line Superposition unit, 46: water level reference line superposition unit, L: water level limit line, K: water level reference line, W: water surface, 100: peripheral monitoring system (peripheral monitoring device).

Claims (10)

A control unit that causes a display device to display an image based on captured image data output from an imaging unit that captures an image of the vehicle body surface and the periphery of the vehicle body surface as an imaging range,
An image processing unit that superimposes a water level limit line based on the water level limit information at the time of cruising traveling of the vehicle at a corresponding position of the vehicle body surface on the image.
A peripheral monitoring device comprising:   The periphery monitoring device according to claim 1, wherein the control unit displays an image obtained by correcting the captured image data obtained by capturing the side surface of the vehicle.   The peripheral monitoring device according to claim 2, wherein the control unit performs a viewpoint conversion process on the captured image data as the correction.   The periphery monitoring device according to claim 2, wherein the control unit performs a distortion correction process on the captured image data as the correction.   5. The periphery monitoring device according to claim 2, wherein the control unit performs, as the correction, a cutout process of cutting out a part of the captured image data. 6.   The surroundings monitoring device according to any one of claims 1 to 5, wherein the image processing unit superimposes the water level limit line having a shape along the surface shape of the vehicle at the corresponding position.   The peripheral monitoring device according to claim 1, wherein the image processing unit superimposes the straight water level limit line on the corresponding position.   The control unit according to any one of claims 1 to 7, wherein when the water level limit line is displayed, a display area of the vehicle body surface in the image is larger than when the water level limit line is not displayed. Perimeter monitoring device as described.   The surroundings monitoring device according to any one of claims 1 to 8, wherein the image processing unit superimposes a water level reference line at a position lower in the vehicle height direction than the water level limit line superimposed on the image.   The periphery monitoring device according to claim 9, wherein the image processing unit superimposes the water level reference line in a display mode different from the water level limit line.

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