JP2015127669A - Water flow observation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water flow observation method for simply and accurately observing a water flow at a desired water area.SOLUTION: A water flow observation method comprises the steps of: photographing a predetermined water area with a thermographic camera 5 from above by using a multi-rotor helicopter 1 mounting the thermographic camera 5 and a GPS sensor 4; and observing a water flow at the predetermined water area on the basis of a water surface temperature distribution image obtained by the photographing.

Description

  The present invention relates to a water flow observation method used for a water flow investigation such as a river flow, and more particularly to a water flow observation method using a thermo camera (infrared thermography).

  Conventionally, as a method for observing water currents such as rivers and tidal currents, for example, there is observation by installing an anemometer.

  As such an anemometer, for example, an image sensor that is sensitive to the pattern of the fluid surface along the flow direction is provided in the upper space of the water channel through which the fluid having a free water surface flows, and the pattern information of the fluid surface at different time periods is respectively obtained. The amount of pattern movement when the correlation function is maximized by adjusting the mutual transfer of the pattern information of both stored in the memory and read from the memory is obtained, and the flow of the fluid in the water channel exhibiting a random phenomenon is determined from the pattern movement speed An anemometer that measures the surface flow velocity has been proposed (see Patent Document 1).

  This anemometer can be used to measure the surface flow velocity of clean water, sewage, agricultural water, rivers, etc., and can stably measure by avoiding the influence of impurities inside the fluid, but the observation point is limited There's a problem.

  In addition, a video camera for photographing the relief pattern on the water surface at regular time intervals, an image processing means for performing a process of cutting a low frequency component from an image photographed by the video camera and leaving a high frequency component, and a first An average pixel color value of the first specific area is calculated by specifying a certain area in the image, an average pixel color value in a plurality of areas in the vicinity of the specified area in the second image is calculated, An area correlation value between an average pixel color value in a specified area of one image and a plurality of average pixel color values in a second image is calculated, and an area having the maximum area correlation value in the second image is calculated There has been proposed a water flow measuring device comprising comparison area specifying means for specifying as a second specific area and water flow calculating means for calculating the direction and / or speed of the water flow based on position data of the first to nth specific areas. (See Patent Document 2) ).

  This water flow measuring device takes video camera photographs of the undulation pattern on the water surface caused by the flow and waves of water at regular time intervals, measures the movement amount and movement direction of the undulation pattern in a certain area, and measures the flow velocity and water flow. One or both of the directions are measured, and a correlation window image centered on the measurement point is cut out from two images (captured images) taken at a certain time interval, and between the correlation window images The velocity and direction of the flow are measured based on the positional relationship of the correlation window that maximizes the similarity of the average pixel color value. However, since a complicated process of measuring the movement amount and movement direction of the undulating pattern from an image photographed using a normal video camera is necessary, and the installation location of the video camera is limited, Patent Document 1 Similarly, there is a problem that observation points are limited.

  On the other hand, as a method for observing tidal currents in the range of several hundred meters to several kilometers, there are methods using buoys and dyes. However, according to the method using a dye, since there is a possibility that the spread of the dye may be misunderstood as contamination, there is a problem that frequent investigation cannot be performed.

  In addition, a method for measuring a flow field using a balloon camera has been proposed for the purpose of investigating water currents such as tidal currents (see Patent Document 3). In this method, for example, two balloons are tethered by two ropes and floated at approximately the same height and at the same interval, and a camera capable of photographing the lower part is suspended from each balloon. The surface of the sea is photographed simultaneously and remotely, and the common photographing range is made into a stereo model, and the water surface shape distribution is obtained using a plotter.

  This observation method is a method proposed to solve the problem that stereo photography using an airplane, helicopter, etc. is costly, and that plotting with a small camera has low measurement accuracy and reproducibility. It is a large-scale method that uses, and it is difficult to say that it is inexpensive. In addition, it is necessary to simultaneously perform a work of arranging a plurality of floats on the sea surface and taking images at predetermined time intervals, thereby obtaining a flow direction and a velocity distribution, which is also very complicated. It will be a thing.

JP-A-4-120467 JP 2009-074968 A Japanese Patent Laid-Open No. 52-151074

  This invention is made | formed in view of the above problems, and it aims at providing the water flow observation method which observes a water flow simply and correctly in a desired water area.

  The inventors of the present invention have been conducting research on the rip current, and have investigated the occurrence pattern of the rip current. In the survey, for example, we measured offshore current using a wired GPS small float, but we found a so-called offshore current neckline that is fast and easy to determine the occurrence of offshore current. It is difficult to conduct the survey, and the survey is not easy, and a method capable of performing the water flow survey more simply and accurately has been desired.

Under such circumstances, the present inventors have conducted extensive research on water flow observation methods for the purpose of water flow investigation,
(1) The water flow can be visualized by measuring the water surface temperature using a thermo camera with high temperature resolution.
(2) In order to accurately obtain the water surface temperature, it is necessary to prevent the reflection of the background due to reflection from the water surface and the influence of infrared radiation from the atmosphere. For this purpose, an appropriate altitude above the desired water area is required. From the above, it was found that it was necessary to shoot, and the present invention was completed.

  That is, the present invention is a water flow observation in which a predetermined water area is photographed with a thermo camera from above using a flying body equipped with a thermo camera, and a water flow in the predetermined water area is observed based on a water surface temperature distribution image obtained by the photographing. Regarding the method.

  The flying object used in the water flow observation method of the present invention preferably includes position detection means.

  The flying object used in the water flow observation method of the present invention is preferably a small flying object.

  In the water flow observation method of the present invention, preferably, the water surface is photographed from an altitude of less than 150 m.

  In the water flow observing method of the present invention, preferably, the thermo camera is adjusted within the range of 48.6 ° from the vertically lower side to photograph the water surface, and more preferably, the thermo camera is adjusted to the vertically lower side. Take a picture of the water surface from above.

  Furthermore, in the water flow observation method of the present invention, preferably, the same water area is photographed at a plurality of different photographing angles.

  In addition, the water flow observation method of the present invention preferably observes the water flow at the river junction or the water flow at the river mouth where the river water flows.

  According to the water flow observation method of the present invention, the water flow can be visualized easily and accurately, and the water flow in a desired water area can be grasped.

It is a figure which shows the structure of the small aircraft which concerns on one Embodiment used for the water flow observation method of this invention. It is a block diagram which shows the structure of the small aircraft which concerns on one Embodiment used for the water flow observation method of this invention. It is a figure for demonstrating the reason the imaging | photography at low altitude is required in the water flow observation method of this invention. It is a figure for demonstrating the reason the imaging | photography from upper direction is required in the water flow observation method of this invention. It is a figure for demonstrating the aspect image | photographed from a different angle in the water flow observation method of this invention. It is a figure which shows the relationship between the water depth of a pool and a fire prevention water tank, and temperature. (A) is the image by the thermo camera which shows an example which image | photographed the pool from right above and visualized the water flow, (b) is the image by the visible camera similarly image | photographed with the visible camera. (A) is the image by the thermo camera which shows an example which image | photographed the pool from right above and visualized the water flow, (b) is the image by the visible camera similarly image | photographed with the visible camera. (A) is the image by the thermo camera which shows an example which image | photographed the pool from right above and visualized the water flow, (b) is the image by the visible camera similarly image | photographed with the visible camera. It is a figure which shows the example which image | photographs a pool with a thermo camera from a pool side, the infrared radiation from a background reflects on a water surface, and observation becomes difficult, (a) is an image by a thermo camera, (b) It is an image by a visible camera.

  As the water flow observation method of the present invention, a predetermined water area is photographed with a thermo camera from above using a flying object equipped with a thermo camera, and the water flow in the predetermined water area is observed based on a water surface temperature distribution image obtained by the photographing. If it is a method to do, it will not restrict | limit in particular, By using the water flow observation method of this invention, a water flow can be visualized simply and correctly, and the water flow in a desired water area can be grasped | ascertained.

  Specifically, the water flow can be visualized and observed easily and accurately at the confluence of rivers with different water temperatures, the estuary where the river water flows, the tide, near the shallows, the offshore current generation point, and the like. Unlike the conventional methods using buoys and dyes, the water flow observation method of the present invention can be easily applied at points where it is not known whether the water flow is actually generated by the naked eye, etc. The presence or absence of water flow can be easily grasped.

  For example, safety measures for prevention of water accidents at beaches can be taken by finding offshore currents using the water flow observation method of the present invention. Moreover, since the flow of seawater and the like can be easily visualized, it is possible to predict fish trends. Furthermore, by visualization of the water flow, for example, it can be applied to the prediction of topographic shape such as sand or the like is accumulated in a portion where the water flow overlaps.

  The water flow observation method of the present invention is to photograph a predetermined water area from above using a flying object equipped with a thermo camera. A thermo camera is an infrared thermography that measures the amount of infrared energy emitted from an object and images the temperature distribution of the object, and displays an image in a color tone according to the intensity of the detected infrared light. . Here, since the infrared radiant energy emitted from the object has a correlation with the temperature of the object, the surface temperature of the object is visually recognized by measuring the infrared radiant energy emitted from the surface of the object. be able to.

  Such a thermocamera can use a camera having a temperature resolution and an image resolution that can detect and observe a water flow in consideration of a photographing altitude, a movement of an object to be measured, and the like, and a commercially available thermocamera can be used. it can. For example, a temperature resolution of about 0.2 ° C. and a resolution of about 160 × 120 pixels can be used. This thermo camera generally captures and records a still image, and is preferably capable of capturing and recording a continuous photograph. Further, the thermo camera may shoot and record a moving image. Therefore, the water surface temperature distribution image according to the present invention is an image showing the temperature distribution of the surface portion of the target water flow, and is a still image. And a concept including both moving images.

  The flying object used in the water flow observation method of the present invention is preferably an flying object provided with position detecting means. The position detection means is a means for detecting the current position of the flying object, and can include, for example, a GPS sensor that receives a signal (GPS signal) from a GPS (Global Positioning System) satellite.

  The GPS sensor has a function as a GPS receiver and a function as a GPS antenna, and communicates with a plurality of GPS satellites. The GPS signal received by the GPS sensor is input to the microcomputer, and the microcomputer detects the current position of the flying object based on the GPS signal.

  From the position information (longitude, latitude, altitude) in this position detection means and the photographing angle / viewing angle of the thermo camera, a photographing water area (a predetermined water area centered on a specific point) can be specified. In order to make it easy to specify the shooting position by the thermo camera, it is preferable that the position information of the position detection means is simultaneously imposed inside the image.

  In addition, when conducting a survey of a narrow area of water with a specified location, position detection means are not necessarily required. For example, a visible camera is mounted on a flying object together with a thermo camera, and a shooting water area is specified from a visible image. You can also

  The flying body according to the present invention is not particularly limited as long as it reaches the upper side (altitude) of a desired water area and enables photographing, and is preferably a small flying body, for example, A multi-rotor helicopter, a radio control helicopter, etc. can be mentioned.

  The small air vehicle is a so-called unmanned aerial vehicle (UAV), and the “small size” of the small air vehicle means a size that a person cannot board. As the small flying object, for example, a small flying object that does not affect the water surface of the observation water area by the operation of the flying object such as rotation of a rotor (rotary wing) is preferable.

  Specific examples of the flying object include those that determine the flight path by operating the flying object by a remote operation (controller) based on the information of the position detection means. That is, the small airplane is configured to operate by remote control, and the flying object can be moved to a desired position while confirming the current position of the small flying object based on information from the position detection means. . It is also possible to determine the course of the small air vehicle while checking the water surface temperature distribution image by the thermo camera on the monitor at hand. Furthermore, the small flying object may be one that automatically operates a flight path that is set in advance using information of the position detection means.

  Here, the small aircraft according to an embodiment used in the water flow observation method of the present invention will be described in more detail with reference to the drawings.

  As shown in FIG. 1, a multi-rotor helicopter 1 that is a flying object according to an embodiment of the present invention includes a fuselage body 2, four rotors 3, a GPS sensor 4, a thermo camera 5, and a thermo camera 5. It is a small flying object provided with the gimbal 6 to hold | maintain. The multi-rotor helicopter 1 has, for example, a size of about 70 cm in height and width, and a size that does not affect the water surface due to the rotation of the rotor 3 or the like.

  The four rotors 3 are provided at equal intervals around the body body 2. The rotor 3 generates lift by rotating. The rotor 3 has a plurality of about 2 to 4 blades for obtaining lift and a hub for supporting these blades, and the blades are equally spaced around the rotation axis of the rotor 3. Provided.

  As shown in FIG. 2, each rotor 3 is rotated by a motor 7. The motor 7 functions as a drive source that rotates the rotor 3. The motor 7 has a drive shaft, and this drive shaft is connected to the hub of the rotor 3 to transmit a rotational driving force to the rotor 3. The motor 7 is driven by receiving power from a battery (not shown). The battery is held at a predetermined position of the machine body 2.

  The motor 7 is controlled by a microcomputer 8 via a motor amplifier 9. The motor amplifier 9 receives a signal from the microcomputer 8, senses the battery voltage, and adjusts the voltage supplied to the motor 7. For this reason, the battery is connected to the motor amplifier 9 and supplies power to the motor 7 via the motor amplifier 9.

  The microcomputer 8 functions as a controller that controls each part of the multi-rotor helicopter 1 and includes a CPU, a flash memory, a ROM, and the like. The microcomputer 8 may be configured by a one-chip LSI or the like.

  As described above, the multi-rotor helicopter 1 including the airframe body 2, the rotor 3 and the motor 7 held by the airframe body 2 is lifted by the lift generated by the rotation of the rotor 3 driven by the motor 7 and flies. .

  The GPS sensor 4 receives a signal (GPS signal) from a GPS satellite. The GPS sensor 4 is held in a fixed state at a predetermined position on the upper part of the body body 2. The GPS sensor 4 has a function as a GPS receiver and a function as a GPS antenna, and communicates with a plurality of GPS satellites. A GPS signal from a GPS satellite received by the GPS sensor 4 is input to the microcomputer 8 and detected as the current position of the multi-rotor helicopter 1.

  The microcomputer 8 is based on the GPS signal received by the GPS sensor 4, and the spatial coordinates and time including the longitude, latitude, and altitude of the position where the main body 2 of the multirotor helicopter 1 is present (current position of the multirotor helicopter 1). Is detected. For this reason, the microcomputer 8 has a functional unit that detects spatial coordinates and time based on the GPS signal received by the GPS sensor 4. The spatial coordinates and time of the current position of the multi-rotor helicopter 1 acquired by the GPS sensor 4 are used for autonomous navigation control of the multi-rotor helicopter 1 performed by the microcomputer 8 according to a predetermined program. For example, the microcomputer 8 performs feedback control for updating a control amount for the rotor 3 with a target of a navigation route performed according to a predetermined program based on signals transmitted from the GPS sensor 4 and the gyro sensor 10 as needed. Do. Thereby, the microcomputer 8 controls the horizontal position (latitude, longitude), vertical position (altitude), moving direction (traveling direction), moving speed, etc. of the multi-rotor helicopter 1.

  The thermo camera 5 is provided below the center of the body 2 and is stably held by the gimbal 6. The gimbal 6 has a fixing portion that fixes and holds the thermo camera 5 and an angle adjustment mechanism that rotates so as to maintain the photographing angle θ of the thermo camera 5 (an angle with respect to the direction of gravity: see FIG. 4). Under the control of the gyro sensor 10, the thermo camera 5 is maintained at a preset predetermined shooting angle θ. The gyro sensor 10 is a sensor that detects which direction the aircraft is facing with respect to gravity (the direction of gravitational acceleration). The imaging angle θ is preset and stored in a storage unit or the like included in the microcomputer 8.

  The operation of the gimbal 6, that is, the tilting operation of the gimbal 6 relative to the main body 2 is controlled by the microcomputer 8 based on information from the gyro sensor 10. Specifically, the operation of the gimbal 6 is controlled by a servo motor 11 that receives a signal from the microcomputer 8.

  In this embodiment, as shown in FIG. 1, the gimbal 6 has a so-called two-axis control configuration that is controlled by two servo motors 11 (11 a and 11 b) arranged so that the rotation axes are orthogonal to each other. . In other words, the multi-rotor helicopter 1 according to the present embodiment projects, as the servo motor 11, a first servo motor 11a having a predetermined first direction (a direction perpendicular to the paper surface in FIG. 1) as the rotation axis direction, and a projection. And a second servo motor 11b having a second direction (left and right direction in FIG. 1) perpendicular to the first direction as a rotation axis direction, and the operation of the gimbal 6 by these servo motors 11a and 11b. Is controlled. Specifically, the gimbal 6 includes a first support frame portion 6a that is supported by the first servomotor 11a with respect to the airframe of the multi-rotor helicopter 1 and a first support frame portion 6a. A second support frame portion 6b that supports the thermocamera 5 and is supported by a support shaft portion 6a via a rotation shaft that is rotated by a second servomotor 11b. Then, as the inclination of the airframe of the multi-rotor helicopter 1, the thermo camera based on the inclination detected by the gyro sensor 10 for each of the inclination about the axis in the first direction and the inclination about the axis in the second direction. The two servo motors 11a and 11b control the operation of the gimbal 6 such as the inclination of the first support frame portion 6a and the second support frame portion 6b so that 5 is always in a predetermined direction (for example, downward). The By controlling the operation of the gimbal 6, the direction of the thermo camera 5 is controlled so as to be maintained in a fixed direction.

  The setting of the predetermined photographing angle θ of the thermo camera 5 using the gimbal 6 can be set in advance as described above, but can also be changed during flight by remote operation. That is, the microcomputer 8 can be configured to control the operation of the gimbal 6 based on a radio signal received by the RC receiver 12 described later.

  The multi-rotor helicopter 1 has a configuration for performing radio control (remote control). That is, the multi-rotor helicopter 1 includes an RC receiver 12 as a receiver that receives a radio signal for remotely operating the motor 7 (see FIG. 2). The RC receiver 12 is held in a state of being fixed at a predetermined position on the front side surface of the main body 2.

  The RC receiver 12 receives a radio signal from a radio pilot operated by a pilot operating the multi-rotor helicopter 1. The radio signal received from the radio pilot by the RC receiver 12 includes a control signal for controlling the operation of the motor 7 that drives the rotor 3. A radio signal from the radio pilot received by the RC receiver 12 is input to the microcomputer 8 and used for controlling the operation of the motor 7.

  Specifically, when the microcomputer 8 controls the operation of the motor 7 based on the radio signal received by the RC receiver 12, the microcomputer 8 corresponds to the control amount instructed by the operation of the radio pilot. 9, the control amount of the motor 7 is determined, and the rotational speed (rotational speed) of the motor 7 is controlled. Further, in the case of a configuration in which the predetermined shooting angle θ of the thermo camera 5 is changed during flight by remote control, a signal for changing the shooting angle θ is included in the radio signal received by the RC receiver 12 from the radio pilot. It is.

  By using the multi-rotor helicopter 1 equipped with the thermocamera 5 configured as described above, a desired water area can be photographed more stably at a predetermined altitude and a photographing angle θ. The water flow observation method can be implemented more reliably.

  The water flow observing method of the present embodiment is to shoot from a relatively low altitude using the flying object as described above. For example, it may be about 1000 m or less from the water surface, but from an altitude of less than 150 m from the water surface. It is preferable to photograph the water surface, more preferably from an altitude of less than 100 m, and the lower limit is about 3 m. By photographing from the low sky, it is possible to suppress the influence of infrared rays generated from the atmosphere and to measure the temperature of the water surface more accurately. In the water flow observation method of the present embodiment using a small flying object, it is possible to take an image from an altitude lower than the lowest safe altitude (150 m) of the aircraft. The capturing altitude can be grasped by using the GPS mounted on the flying object, but the altitude may be grasped separately using an altimeter.

  In addition, in the water flow observation method of the present embodiment, the photographing altitude can be determined according to the degree of water movement to be detected and observed and the performance (resolution) of the thermocamera 5, for example, When observation is desired or when the performance of the thermo camera 5 is low, desired water flow observation can be performed by photographing from a low sky.

  Note that the shooting area may become narrow due to the low shooting altitude. However, by using a flying object, particularly a small flying object, it is possible to move and photograph easily, and a plurality of photographed images can be combined into one wide range image. For example, it is possible to take a picture by moving the flying object according to the flow of water.

  Moreover, as a method of performing water flow observation, for example, as shown in FIG. 3, a method of performing imaging from the satellite 13 by remote sensing is conceivable. However, in remote sensing by the satellite 13, the position of the satellite 13 is at a high altitude, so that the infrared radiation from the water surface to be measured is buried in the infrared radiation of the atmosphere or affected by the radiation from the deep part of the water. In addition, since the photographing location is too far and the image becomes rough, it is difficult to observe the infrared radiation from the target water surface. In particular, it is difficult to accurately observe water flow in a narrow water area of about 1 to 1000 m square, for example. Therefore, in the water flow observation method of the present embodiment, it is preferable to take a picture from a relatively low sky, and the multi-rotor helicopter 1 that can be easily measured at an arbitrary altitude in the range from the water surface to several hundred meters is a water flow by the thermo camera 5. Suitable for observation.

  In the case of remote sensing by the satellite 13, it is difficult to continuously take images in such a short time that the change of the water surface state can be grasped in order to observe the water flow, and it is difficult to accurately observe the water flow. is there. In this regard, according to the water flow observation method of the present embodiment, the multi-rotor helicopter 1 can be moved to a predetermined position and the water surface can be continuously photographed at a relatively short time interval. The change in temperature state is known, and the movement of the water current can be accurately observed.

  Furthermore, the water flow observation method of the present embodiment is to take a picture of the water surface from above in a predetermined water area using a flying object, but it is preferable to take a picture of the water surface at an angle such that the background does not appear on the water surface. .

  That is, as shown in FIG. 4, for example, when photographing the water surface of the river 20, it is conceivable to photograph the water surface of the river 20 from the fixed thermo camera 14 installed on the ground near the coast of the river 20. However, according to the fixed thermocamera 14 installed on the ground near the coast of the river 20, the shooting angle with respect to the water surface becomes shallow, so that infrared radiation from a building or the like on the other side (opposite side) of the river 20 causes the surface of the river 20 to This causes a phenomenon that the building is reflected in the image. Such a phenomenon may make accurate temperature measurement of the water surface difficult. In this regard, as in the water flow observation method of the present embodiment, the multi-rotor helicopter 1 is used to move the thermo camera 5 to a position where it is desired to photograph, and the water surface is photographed from above, thereby preventing the above-described reduction in reflection. This makes it possible to accurately measure the temperature distribution on the water surface.

  Specifically, the photographing angle θ of the thermo camera 5 may be adjusted by adjusting the thermo camera 5 within a range of 48.6 ° (θ = 0 to 48.6 °) from the vertically lower side to shoot the water surface. Preferably, it is more preferable to adjust within the range of 30 ° from the vertically lower side (θ = 0 to 30 °), more preferably within the range of 15 ° from the lower vertical side (θ = 0 to 15 °), It is particularly preferable to take a picture of the water surface from vertically above by adjusting vertically downward (θ = 0 °).

  Moreover, in the water flow observation method of this embodiment, the same water area or the same point can be image | photographed with several imaging | photography angles as needed, when the temperature difference of a water surface is not clear.

  As shown in FIG. 5, in photographing from an oblique direction by the multi-rotor helicopter 1A with the thermo camera 5 directed obliquely downward with respect to the vertical direction, infrared radiation from the deep part of water (see arrow A1) due to light attenuation. ), The ratio of infrared radiation (see arrow A2) on the surface portion is higher. Therefore, the temperature distribution on the water surface may become clearer when photographing from an oblique direction. For this reason, it is possible to obtain information on the depth direction of the water by analyzing the information of a plurality of shooting angles together, and more accurately grasp the temperature of the water surface portion, and more accurate The water flow can be grasped. In addition, when performing measurement by photographing from an oblique direction, it is preferable to perform the measurement within the range of the photographing angle θ in order to prevent the reflection of a building or the like as described above.

  In this way, as a method of photographing the same water area at a plurality of photographing angles, for example, a specific point on the water surface is set as the photographing center, and after photographing once, the flying object is moved and the photographing center is set. By photographing again with the thermo-camera 5 set so as to always face the photographing center, photographing at different angles with respect to the same portion can be performed. In such a photographing method, for example, from the relationship between the position of the photographing center and the spatial coordinates of the multirotor helicopter 1 detected by the GPS sensor 4, the change in the photographing angle of the thermocamera 5 as the multirotor helicopter 1 moves. Is calculated, and the imaging angle of the thermo camera 5 is adjusted based on the calculation result.

  Further, the water flow observation method of the present embodiment detects a water flow in a predetermined water area from a water surface temperature distribution image obtained by photographing with the thermo camera 5. Here, the water surface temperature distribution image according to the present invention does not necessarily mean an image showing the exact temperature distribution of the water surface (water surface), but a water surface portion (surface) obtained by photographing from above with a thermo camera. It means an image representing the temperature distribution of the layer.

  Specifically, in water flow surveys such as tidal currents, when the amount of solar radiation in fine weather is high, the temperature of the water surface part (surface part) becomes higher than the temperature of the water depth part. It is determined that the water flow is generated in the portion where the water surface temperature in the water surface temperature distribution image is relatively low by utilizing the fact that the water surface temperature where the water mixing occurs is relatively low.

  For example, the discovery of a rip current is an important point to find a fast part called a neck (neckline), but it is generally difficult to find a neck in this rip current. This difficulty in finding the neck part makes it difficult to find and clarify the rip current, but according to the water flow observation method of this embodiment, it is possible to visually grasp the water flow from the water surface temperature distribution image. As a result, it is possible to elucidate the entire picture of the offshore flow as well as the neck of the offshore current.

  The ability to discover offshore currents provides the following benefits: Offshore currents are largely involved in coastal erosion. For example, a cliff is formed by sand being washed away by a rip current. For this reason, it becomes possible to grasp the situation of the movement of the sand supplied from the river by grasping the actual situation of the offshore flow. Such information is used, for example, for installing a breakwater or maintaining a coastal shape. In addition, the offshore current is a cause of locally forming a deep water portion. For this reason, if the flow of a rip-off flow can be recognized, a customer's safety can be protected, for example in a beach. Also, the place where the offshore current is generated tends to be a fishing ground. Therefore, when forming a fishing ground, it is possible to appropriately determine how to arrange an artificial object such as a tetrapot with respect to a rip current.

  Further, according to the water flow observation method of the present embodiment, in the water flow survey at the river mouth where river water flows, fresh water flowing from the river into the sea is lower in temperature and lighter than sea water. Can be determined. Furthermore, in the water flow survey at the confluence of rivers, the water flow can be observed because the water temperatures of the rivers are different.

  Hereinafter, the present invention will be described based on examples.

  First, in this example, the water depth and the water temperature were measured for each of a highly transparent pool immediately after water change and a fireproof water tank with low transparency. The relationship is shown in FIG. In the graph shown in FIG. 6, the horizontal axis is the water temperature (° C.), and the vertical axis is the water depth (cm). The measurement result shown in FIG. 6 is a measurement result in the same time zone on the same day in fine weather.

  As shown in FIG. 6, this measurement result is a measurement result in the same time zone on a clear day, but the temperature of the water surface portion (water depth 10 cm) is 0.5 ° C. in the pool and 4 in the fire prevention water tank. A temperature rise of ℃ was observed. The rivers and oceans to be observed have transparency in the middle between the pool and the fire prevention water tank, and a temperature change of several degrees can be expected at a water depth of about 15 cm. Since the commercially available thermo camera has a temperature resolution of about 0.1 ° C., it is considered that it can be sufficiently observed.

  Moreover, in this example, a water flow was actually created on the water surface of the pool before water change, and the water surface vertically below was observed with a thermo camera and a visible camera mounted on a small flying object. The results are shown in FIGS. 7 to 9, (a) is an image by a thermo camera taken from directly above the pool with a thermo camera, and (b) is an image by a visible camera taken by the visible camera in the same manner.

  As shown in each figure (b), the water flow which cannot be observed with a visible camera is clearly shown in the water surface temperature distribution image with a thermo camera as shown in each figure (a). You can see that it is captured. That is, in the images obtained by the visible cameras shown in FIGS. 7 to 9, the color of water only appears monotonously regardless of the water surface temperature, and the water flow cannot be observed. According to the image by the thermocamera shown in FIG. (A), since the temperature distribution of the water surface appears as a change in color, it becomes possible to visually observe the water flow accompanying the temperature change of the water surface.

  Moreover, the water surface of the pool immediately after water change was image | photographed with the thermo camera and visible camera which were installed on the ground as a comparative example. In this comparative example, as described with reference to FIG. 4, a building or the like is reflected in an image due to reflection of the water surface. The result of this comparative example is shown in FIG. In FIG. 10, (a) is an image by a thermo camera taken by a thermo camera from a shallow angle, and (b) is an image by a visible camera taken by a visible camera in the same manner.

  From the captured image of FIG. 10, as shown in FIG. 10B, in the visible camera image, a background building or the like is reflected on the water surface, and the reflected portion of the building or the like in the visible camera image is Also in the image by the thermocamera shown to the same figure (a), it is received as influenced as temperature distribution of a water surface. That is, in the image by the thermo camera of FIG. 10A, the temperature information of the water surface is not obtained due to the reflection of the background above the center of the water surface portion. From this, it can be seen that, as in the water flow observation method according to the present embodiment, it is necessary to observe from above, preferably vertically above the water surface.

  As described above, the present invention has devised a method for observing a water current using a bird's-eye view image by a thermo camera for the purpose of investigating river flows and tidal currents. When there is a lot of solar radiation in fine weather, the water surface temperature is higher than the water depth, so the water flow appears as a water surface temperature distribution due to the difference in water temperature between the water surface and the water depth. By using, water flow can be visualized. The method according to the present invention preferably employs photographing and observation of the water surface from above by a flying object such as a multi-rotor helicopter equipped with GPS in order to prevent reflection of the background due to reflection from the water surface.

  According to the water flow observation method according to the present invention, the water flow in a desired water area, such as a confluence of rivers with different water temperatures, river water flowing into the estuary into the sea, tide, near shallow water, offshore current generation point, etc. can be accurately observed. can do.

1 Multirotor helicopter (small aircraft)
2 Body body 3 Rotor 4 GPS sensor 5 Thermo camera 6 Gimbal 7 Motor 8 Microcomputer 9 Motor amplifier 10 Gyro sensor 11 Servo motor 12 RC receiver 13 Satellite 14 Fixed thermo camera

Claims (8)

  A method for observing a water current in which a predetermined water area is photographed from above with a thermo camera using a flying body equipped with a thermo camera, and the water flow in the predetermined water area is observed based on a water surface temperature distribution image obtained by the photographing. .   The water current observation method according to claim 1, wherein the flying object includes a position detection unit.   The water flow observation method according to claim 1, wherein the flying object is a small flying object.   The water flow observation method according to claim 1, wherein the water surface is photographed from an altitude of less than 150 m.   5. The water flow observation method according to claim 1, wherein the water surface is imaged by adjusting the thermo camera within a range of 48.6 ° from below in the vertical direction.   The water flow observation method according to any one of claims 1 to 5, wherein the thermo camera is adjusted vertically downward to photograph the water surface from vertically above.   The water flow observation method according to claim 1, wherein the same water area is photographed at a plurality of different photographing angles.   The water flow observation method according to any one of claims 1 to 7, wherein a water flow at a confluence of rivers or a water flow at a river mouth into which river water flows is observed.