Surveying system and method for surveying river

Abstract

To enable measurement of the velocity distributions and the flow rates of longitudinal and cross sections of water areas such as rivers in a manner more consistent with actual conditions.SOLUTION: The surveying system according to the present invention includes: a mobile body movable on a water surface; first measuring means for measuring the flow velocity below the mobile body; second measuring means for measuring the surface flow velocity around the mobile body; and third measuring means for measuring the moving speed of the mobile body. The method for surveying a river according to the present invention includes the step of causing the mobile body of the present invention to drift from the upstream side to the downstream side of the river on the river flow.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a technique for measuring flow velocity distribution and flow rate of a river or the like. [Background technology]

[0002] The following Patent Document 1 discloses a position measurement system that identifies the current position of a ship equipped with a camera that photographs the water surface and a Doppler current meter using an airship flying above the ship. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2006-300700 Summary of the Invention [Problem to be solved by the invention]

[0004] With the increasing severity of flood damage due to global warming and the strengthening of disaster prevention legislation, new flood control systems and river management methods are needed to keep up. However, the rivers that are the subject of management each have their own geographical and spatial characteristics, and their conditions change from moment to moment due to floods, making them difficult to predict. To ensure that rivers maintain their required safety into the future, it is necessary to understand the mechanisms behind river channel changes and the destruction of structures, and to quantitatively predict the hydraulic impacts of rainfall and floods. Understanding river flow rates and their changes during normal and flood periods is particularly important for river management. However, there are currently no methods that can measure the flow velocity distribution and flow rate over long distances in the longitudinal and cross-sectional planes of rivers during floods. Therefore, these estimates are currently based on theoretical values ​​obtained through experiments and empirical rules.

[0005] In view of these problems, the problem that the present invention aims to solve is to make it possible to measure the flow velocity distribution and flow rate in the longitudinal and transverse sections of a water body such as a river in a manner that is more in line with the actual situation. [Means for solving the problem]

[0006] In order to solve the above problem, the surveying system of the present invention comprises a mobile body capable of moving on the water surface, a first measurement means for measuring the flow velocity below the mobile body, a second measurement means for measuring the water surface flow velocity around the mobile body, and a third measurement means for measuring the movement speed of the mobile body.

[0007] By acquiring the current velocity below the moving object and the surface current velocity around it, it is possible to estimate the current velocity distribution in the water area around the moving object based on actual measurements. In addition, by acquiring the moving speed of the moving object itself, it is possible to continuously acquire the current velocity distribution in a wider water area while moving the moving object on the water surface.

[0008] In this case, it is preferable that the first measurement means includes an ultrasonic Doppler current meter mounted on the moving body. An ultrasonic Doppler current profiler (ADCP) is a device that acquires flow velocity by emitting sound waves into water and measuring the Doppler shift of scatterers (suspended matter, etc.) that move with the water current. By acquiring the flow velocity below the moving body in multiple layers using the ultrasonic Doppler current meter, it becomes possible to more accurately calculate the flow velocity distribution around the moving body. Note that the ultrasonic Doppler current meter can also measure the movement speed of the moving body itself by measuring the Doppler shift at the water bottom. In other words, the ultrasonic Doppler current meter can also be used as a third measurement means.

[0009] In the surveying system of the present invention, the second measuring means may include a photographing means mounted on the moving body and taking pictures of the water surface around the moving body. By having the moving body itself equipped with a photographing means, it becomes possible to conduct surveying more easily, for example, without having to install fixed cameras around the water area to be surveyed in advance or separately photograph the water surface from the sky using a drone equipped with a camera.

[0010] In this case, it is preferable that the second measurement means includes one or more image capturing means for capturing images of a range including at least the left and right directions of the moving body when the moving body is moving forward, thereby making it possible to continuously measure the flow velocity distribution in the longitudinal and transverse cross sections of the water body along the moving direction (longitudinal direction) of the moving body.

[0011] In this case, it is preferable that the moving body has an orientation unit, which is a subject whose position relative to the moving body is fixed, and that the orientation unit is located at a position that is reflected in the image captured by the photographing means. For example, in Space-Time Image Velocimetry (STIV), in order to geometrically correct a water surface image captured from obliquely above to an image viewed from directly above, orientation points whose position coordinates in real space are known are installed on the shore on the near side (camera side) of the water area to be photographed and on the opposite shore. By providing an orientation unit fixed to the moving body, i.e., an orientation unit whose position coordinates relative to the position of the photographing means equipped on the moving body are known, and including this in the angle of view of the photographing means, it can be used as an orientation point on the camera side.

[0012] Furthermore, it is preferable that the surveying system of the present invention further comprises an analysis means, which calculates the actual flow velocity by adding the moving velocity of the moving body acquired by the third measurement means to the flow velocity acquired by the first measurement means and the flow velocity acquired by the second measurement means. This eliminates errors in the flow velocity caused by the movement of the moving body itself, and makes it possible to continuously acquire the flow velocity distribution of a wider water body.

[0013] Furthermore, the surveying system of the present invention further comprises an analysis means, and when the calibration coefficient for determining the average value of the depthwise flow velocity distribution of the water body from the water surface flow velocity around the moving body acquired by the second measurement means is called the surface flow velocity coefficient, the analysis means preferably modifies the surface flow velocity coefficient based on the flow velocity below the moving body acquired by the first measurement means. Generally, a fixed value of 0.85 is used for the surface flow velocity coefficient of rivers. However, depending on the flow conditions and river shape, calculation results using this surface flow velocity coefficient may deviate from the actual situation. By adjusting the surface flow velocity coefficient based on the actually measured flow velocity below the moving body, calculation results that are more in line with the actual situation can be obtained.

[0014] Here, it is more preferable that the moving body further includes a scanner device that acquires underwater topography data, and the analysis means changes the surface current velocity coefficient based on the flow velocity below the moving body acquired by the first measurement means and the underwater topography data acquired by the scanner device. By simultaneously acquiring topography data of the surveyed water area, more accurate calculation results can be obtained.

[0015] In addition, in the surveying system of the present invention, the mobile body may be an unmanned aerial vehicle. By being able to move freely in three-dimensional space, the mobile body can, for example, safely move into dangerous water areas and land on water without human intervention. Furthermore, it becomes possible to fly around and avoid structures and floating objects that cannot be avoided or evaded on the water surface.

[0016] In this case, it is preferable that the second measurement means is mounted on the moving body and includes a photographing means for photographing the water surface around the moving body, and that the moving body is equipped with a collision avoidance means for automatically taking off from the water to avoid a floating object when a photograph is taken of the floating object approaching the body to a predetermined distance. For example, in a river during a flood, the moving body may be damaged by a collision with driftwood or the like. By making the moving body an unmanned aerial vehicle and monitoring floating objects around the body with a photographing means, it is possible to automatically avoid collisions with floating objects.

[0017] In order to solve the above problems, the present invention provides a river surveying method that includes a step of floating the mobile object of the present invention along the water current of the river from upstream to downstream, thereby making it possible to continuously measure the flow velocity distribution in the longitudinal and cross-sectional planes of the river based on actual measurements.

[0018] The river surveying method of the present invention may also include a step of disposing the plurality of mobile bodies at different positions in the river width direction and floating them downstream along the water current of the river, thereby reducing the time required to survey a large river.

[0019] Furthermore, the river surveying method of the present invention preferably includes a step in which the mobile body is an unmanned aerial vehicle, and when the mobile body reaches a predetermined position down the river, the mobile body automatically takes off and flies, and lands at another position further downstream. This reduces the need for a pilot to be present and the piloting skills required of the pilot, making it possible to carry out river surveying more safely and easily. [Effects of the Invention]

[0020] As described above, the surveying system and river surveying method of the present invention make it possible to measure the flow velocity distribution and flow rate of a water body such as a river in a more realistic manner. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 2 is a perspective view of the multicopter 12. [Figure 2] 1 is a block diagram showing the overall configuration of a surveying system 10. FIG. [Figure 3] FIG. 2 is a block diagram showing an automatic pilot function provided in the FC / BC 20. [Figure 4] 1 is a schematic diagram illustrating a method for calculating the flow velocity distribution and flow rate of a river in its longitudinal and cross-sectional planes using the surveying system 10. FIG. [Figure 5] 1 is a schematic diagram showing a specific example of an image analysis method for water surface current velocity in this embodiment. FIG. [Figure 6]FIG. 10 is a schematic diagram showing another example of the imaging means. [Figure 7] FIG. 1 is a schematic diagram showing a multicopter 12 riding on the water current of a river and descending the river. [Figure 8] FIG. 1 is a schematic diagram showing a state in which multiple multicopters 12 ride the current of a river and descend the river. DETAILED DESCRIPTION OF THE INVENTION

[0022] An embodiment of the present invention will be described below with reference to the drawings. The surveying system 10 and river surveying method described below primarily feature the following: a multicopter 12, an unmanned aerial vehicle, is floated along the river's water flow, the flow velocity distribution by layer below the aircraft, the water surface flow velocity around the aircraft, and the river channel shape; and, based on these measurements, calculates the flow velocity distribution, average flow velocity, and flow rate in the longitudinal and cross-sectional planes of the river. This feature and other associated features will be described below through the embodiments. Note that "surveying" in the following description refers to measuring flow velocity, river channel shape (topography), flow rate, water level, etc., and is not limited to the meaning of "surveying" as defined in the Surveying Act. In the following description, "image" refers not only to still images but also to "video" and "video," i.e., a series of still images.

[0023] <Surveying system overview> Fig. 1 is a perspective view of a multicopter 12, and Fig. 2 is a block diagram showing the overall configuration of a surveying system 10. An overview of the surveying system 10 will be described below with reference to Figs.

[0024] As shown in FIG. 1 , the multicopter 12 of this embodiment is a so-called hexacopter, equipped with six arms extending radially in a plan view and rotors 12 fixed to the tips of the arms. The multicopter 12 is equipped with a pair of pontoon-shaped floats 50 that allow the aircraft to float on the water surface, and each float 50 is equipped with a pair of thrusters 42 for moving the multicopter 12 on the water surface. Also attached to the underside of the fuselage of the multicopter 12 are an ADCP unit 70, which is an ultrasonic Doppler current meter that acquires the flow velocity distribution below the aircraft after landing on water, and a sonar unit 80, which is a scanner device that acquires the topography of the river channel (the cross-sectional shape of the river channel). Also installed outside the multicopter 12 are two GPS receivers 31 (hereinafter simply referred to as "GPS 31"), which are GNSS (Global Navigation Satellite System) devices.

[0025] As shown in Fig. 2, the surveying system 10 of this embodiment is mainly composed of an analysis device 11 and a multicopter 12. The analysis device 11 and the multicopter 12 are connected via the Internet. In this embodiment, the operator terminal 19 of the surveying system 10 is also connected to each device via the Internet.

[0026] (multicopter) The multicopter 12 of this embodiment is composed of a flight controller / boat controller 20 (hereinafter referred to as "FC / BC 20") which is a control device, a GPS 31, an RTK receiver 32, a rotor 41, thrusters 42 connected to the FC / BC 20, an omnidirectional camera 60 (hereinafter simply referred to as "camera 60") which is an imaging means, an ADCP unit 70, a sonar unit 80, and a float 50. The FC / BC 20 of this embodiment includes an IMU (Inertial Measurement Unit), a barometric pressure sensor, a direction sensor (electronic compass), etc.

[0027] The FC / BC 20 drives the rotors 41 and thrusters 42 to fly and navigate the multicopter 12 in response to various autopilot programs (described later) and instructions from the operator terminal 19. In the surveying system 10 of this embodiment, the multicopter 12 is equipped with the thrusters 42, thereby increasing the freedom, flexibility, and safety of river surveying using the multicopter 12. Note that "navigation" here means that the multicopter 12 moves on the water surface. The multicopter 12 of this embodiment is equipped with six rotors 41 as thrust sources for movement through the air and two thrusters 42 as thrust sources for movement on the water surface, and the FC / BC 20 can switch automatically or in response to instructions from the operator terminal 19 between a "flight mode" in which the rotors 41 are used to move through the air and a "navigation mode" in which the thrusters 42 are used to move on the water surface. The operator can remotely control the multicopter 12 visually if it is within the visual range, or by relying on images transmitted from the camera 60 if it is out of the visual range.

[0028] The RTK receiver 32 is an RTK device that acquires correction information for the longitude and latitude values ​​and altitude values ​​acquired by the GPS 31. The RTK receiver 32 in this embodiment acquires correction information provided as an Internet service via an LTE (Long Term Evolution) line. This eliminates the need to install RTK base stations (fixed stations) around each survey point. Furthermore, the distance restrictions between the RTK receiver 32 and each RTK base station are relaxed, enabling faster, simpler, and more extensive surveying. The RTK receiver 32 may use other mobile communication networks, such as 5G, 3G, or WiMAX (Worldwide Interoperability for Microwave Access), in addition to an LTE line. While this embodiment employs GPS as the GNSS device, it may also be a receiver for other technologies, such as GLONASS, Galileo, Michibiki (Quasi-Zenith Satellite System), or COMPASS (BeiDou Satellite Positioning System).

[0029] Here, the FC / BC 20 in this embodiment continues to operate the GPS 31 and the RTK receiver 32 even after the rotors 41 have stopped, for example, after the multicopter 12 has landed on water. The moving speed of the multicopter 12 on the water surface can be calculated from the longitude and latitude information of the GPS 31.

[0030] The camera 60 is a so-called 360° camera / celestial camera that is supported above the body of the multicopter 12 and captures images of the sides and above the body in a hemispherical shape. The images captured by the camera 60 are sent to the analysis device 11 and the operator terminal 19, and are also input to the FC / BC 20 (an image analysis program 231, described later).

[0031] The ADCP unit 70 is a device that emits sound waves into the water and measures the Doppler shift of scattering bodies (suspended matter, etc.) that move with the water current, thereby obtaining the flow velocity distribution of each layer according to the water depth. The ADCP unit 70 may also be equipped with its own electronic compass and IMU.

[0032] The ADCP unit 70 of this embodiment is equipped with three or more probes with different orientation angles. The ADCP unit 70 converts the one-dimensional current velocity measured by the probes into a three-dimensional current velocity by applying trigonometry based on the arrangement angles of these probes. The ADCP unit 70 of this embodiment can also be used as a DVL (Doppler Velocity Log). That is, it can emit sound waves from the multicopter 12 toward the bottom of the water and measure the ground speed of the multicopter 12 from the Doppler shift of the waves reflected from the bottom of the water. In other words, it can also obtain the moving speed of the multicopter 12 on the water surface.

[0033] The sonar unit 80 is a multi-beam echo sounding device (so-called multi-beam sonar), which transmits sound beams of different frequencies in a fan-shaped pattern into the water and receives the reflected waves to obtain topographical data of the river.

[0034] The sonar unit 80 is a unit that includes a transmitter with an array of multiple sonars, a receiver that receives reflected waves, a dedicated IMU, and a surface sound speedometer. Ultrasonic measurements are less affected by turbidity than optical cameras or green lasers, and more accurate terrain data can be obtained even under difficult conditions. The scanner device mounted on the multicopter 12 need not be the sonar unit 80, as long as it can acquire underwater terrain data after the multicopter 12 lands on the water. For example, if only highly transparent, still water areas are to be surveyed, it is believed that terrain data can also be acquired using a scanner device that uses an optical camera or laser.

[0035] (Analysis equipment) The analysis device 11 in this embodiment is a server computer, a PC, or a dedicated computer device. The analysis device 11 may be a single device or a combination of multiple devices. Furthermore, the operation terminal of the operator terminal 19 may have the functions of the analysis device 11.

[0036] The analysis device 11 of this embodiment acquires the current velocity distribution (or the original data) below the multicopter 12 from the ADCP unit 70, the water surface image around the aircraft from the camera 60, and the topographical data from the sonar unit 80. The analysis device 11 of this embodiment also acquires longitude and latitude values ​​and altitude values ​​obtained by correcting the output information of the GPS 31 with the correction information of the RTK receiver 32.

[0037] As will be described in detail later, the analysis device 11 calculates the flow velocity distribution and flow rate in the longitudinal and cross-sectional planes of the river basin through which the multicopter 12 traveled, based on various actual measurement values ​​received from the multicopter 12. The surveying system 10 of this embodiment is equipped with a configuration (analysis device 11) specialized for collecting, analyzing, and integrating data acquired by the multicopter 12 and its onboard equipment, thereby appropriately distributing the load and functions of the surveying system 10 throughout the system. Furthermore, the analysis device 11 accumulates survey results, and the accumulated information is widely shared with river operators, researchers, and the like. Note that an independent analysis device 11 is not essential for the surveying system 10, and the functions of the analysis device 11 may be provided in the multicopter 12.

[0038] (Autopilot function) 3 is a block diagram showing the autopilot functions of the FC / BC 20. The multicopter 12 of this embodiment is equipped with the following autopilot functions: an autonomous flight program 21, an autonomous navigation program 22, a collision avoidance program 23, an image analysis program 231, a heading control program 24, and a flight detouring program 25. Each of the autopilot functions of the FC / BC 20 will be described below.

[0039] The autonomous flight program 21 is a function that automatically flies the multicopter 12 according to a flight plan prepared in advance. The flight plan is data that includes parameters such as a takeoff point (takeoff from water) and a landing point (landing on water) specified on map data, one or more waypoints that make up the flight route, flight altitude at each waypoint, and flight speed between each waypoint.

[0040] The autonomous navigation program 22 is a function that automatically moves the multicopter 12 on the water surface according to a cruise plan (navigation plan) prepared in advance. The cruise plan is data that includes a start point, an end point, and one or more waypoints that constitute a navigation route specified on map data. The autonomous navigation program 22 automatically operates the thrusters 42 so that the multicopter 12, which rides the river current and travels downstream, moves along the navigation route.

[0041] The collision avoidance program 23 and the image analysis program 231 are functions that prevent the multicopter 12 from colliding with floating objects on the water surface or surrounding objects in the navigation mode. The image analysis program 231 identifies the positional relationship between the body of the multicopter 12 and its surrounding objects based on images captured by the camera 60. Based on the analysis results of the image analysis program 231, the collision avoidance program 23 automatically operates the thrusters 42 so that the distance between the multicopter 12 and its surrounding objects does not fall below a predetermined distance and so that the multicopter 12 does not deviate from its navigation route as much as possible. When an image of a floating object, such as driftwood, approaching the body of the multicopter 12 within a predetermined distance is captured, the multicopter 12 automatically takes off to avoid the floating object. The collision avoidance program 23 can also use a ranging sensor, such as a LiDAR (Light Detection and Ranging) sensor, one or more ultrasonic ranging sensors, laser ranging sensors, a stereo camera, a depth camera, or a millimeter-wave radar, directed laterally (horizontally) from the body of the multicopter 12. When the distance to the surrounding objects cannot be determined by the camera 60 alone, these sensors may be used in combination.

[0042] The heading control program 24 is a function that controls the heading direction of the aircraft, i.e., the orientation of the sonar unit 80, using an electronic compass provided in the FC / BC 20. The heading control program 24 of this embodiment automatically operates the thrusters 42 to maintain the sonar array direction of the sonar unit 80 in an orientation that intersects (as perpendicular as possible to) the direction of travel along the navigation route of the cruise plan.

[0043] The flight detour program 25 is a function that allows the multicopter 12, which rides the river current down the river, to fly around structures that it cannot pass through, such as water intake weirs and dams. When the multicopter 12 reaches a predetermined position down the river, the flight detour program 25 automatically causes the multicopter 12 to take off and fly, and land at another position further downstream. In this embodiment, the takeoff and landing points of the flight detour program 25, as well as the flight altitude between these two points, are specified as waypoints in the cruise plan.

[0044] As described above, the surveying system 10 of this embodiment is equipped with various automatic operation functions, and can perform surveying of a certain level or above in quality even when the operator terminal 19 is inexperienced or when the surveying is outside of visual range.

[0045] <Calculation method of flow velocity distribution and flow rate> FIG. 4 is a schematic diagram illustrating a method for calculating the flow velocity distribution and the flow rate of a river in its longitudinal and cross-sectional planes using the surveying system 10. In FIG.

[0046] As described above, the surveying system 10 is equipped with a first measuring means for measuring the flow velocity distribution below the body of the multicopter 12, a second measuring means for measuring the water surface flow velocity around the body, and a third measuring means for measuring the moving speed of the body. The surveying system 10 of this embodiment then combines these with topographical data of the river to calculate the flow velocity distribution and the flow rate of the river in its longitudinal and cross-sectional planes.

[0047] (First measurement method) In the surveying system 10, as shown in FIG. 4(a), the flow velocity distribution of each layer according to depth below the body of the multicopter 12 (shown as A) is measured by the ADCP unit 70 (and the analysis device 11).

[0048] (Second measurement method) The camera 60 of the multicopter 12 captures images of the sides and above the aircraft in a hemispherical shape (illustrated C), and the angle of view includes the water surface SF of the river. The multicopter 12 transmits all of the images captured by the camera 60, or only the water surface portion, to the analysis device 11. The analysis device 11 calculates the water surface current velocity around the aircraft based on the received images.

[0049] In this embodiment, a method applying STIV is used for image analysis of water surface current velocity. Fig. 5 is a schematic diagram showing a specific example. Fig. 5(a) is a schematic diagram of a cut-out portion of the image sent to the analysis device 11, and Fig. 5(b) is a diagram explaining an outline of current velocity calculation using STIV. The method for analyzing water surface current velocity in this embodiment will be explained below with reference to Fig. 5.

[0050] First, a portion of the hemispherical image captured by the camera 60 can be cut out as a planar image by known means. The schematic diagram in Fig. 5(a) is an example of such a cut-out image. In flow velocity calculations using STIV, a water surface image captured obliquely from above is generally corrected to an image viewed from directly above, so control points P, whose position coordinates in real space are known, are set on the near bank (camera side) of the water area being photographed and on the opposite bank. In this embodiment, control points P are set on both banks of the river (see Fig. 4(a)).

[0051] In the multicopter 12 of this embodiment, an orientation unit 71 displaying a mark suitable for this orientation point is fixed to the airframe, and this orientation unit 71 appears in the captured image as a subject. By providing an orientation unit 71 fixed to the multicopter 12, that is, an orientation unit 71 whose relative position coordinates with respect to the position of the camera 60 are known, and including this in the captured image, the orientation unit 71 can be used as an orientation point on the camera side. Note that the orientation unit 71 is not limited to that of this embodiment, and can be replaced by any part, such as the end of the float 50 of the multicopter 12, as long as the relative position with respect to the airframe of the multicopter 12 is fixed and it is positioned so as to appear in the captured image.

[0052] The dashed-dotted box in Figure 5(a) is an example of an inspection line in STIV, and the black circles within the box are brightness feature points such as ripples. As shown in Figure 5(b), STIV arranges the positional changes of brightness feature points in time series, and calculates the surface flow velocity from the gradient θ when the transition of that position is represented as a straight line.

[0053] In this embodiment, the camera 60 is used as a means for photographing the water surface, but this may also be one or more video cameras that photograph the control point P on the shore side from the multicopter 12.

[0054] FIG. 6 is a schematic diagram showing another example of the imaging means. In this embodiment, a camera 60 for capturing images of the water surface is mounted on the multicopter 12 itself, but the imaging means is not limited to this. For example, as shown in FIG. 6, a fixed camera 91 may be installed in advance along the water area to be surveyed, and the water surface current velocity around the multicopter 12 may be measured from the images captured by the fixed camera 91. STIV using a fixed camera 91 has already been widely used and has been well-established, and can further improve the accuracy of measuring water surface current velocity. Alternatively, a so-called drone 92 equipped with a camera may be used to capture images of the water surface from above. Capturing the water area to be surveyed from directly above reduces image degradation and errors in flattening the captured image, thereby further improving the accuracy of measuring water surface current velocity. Furthermore, the second measurement means of the present invention may be any means capable of measuring the water surface current velocity around the multicopter 12 and is not limited to those using image analysis. For example, a method of measuring surface current velocity using radio waves may also be employed.

[0055] (Third measurement method) As described above, there are two methods for measuring the moving speed of the multicopter 12 on the water surface: a method using longitude and latitude information from the GPS 31, and a method using the ADCP unit 70. Either method may be adopted.

[0056] (Method of acquiring topographical data) Returning to Figure 4, a method for acquiring topographical data will now be described. The multicopter 12 of this embodiment is equipped with a sonar unit 80, which can acquire topographical data of a river. As shown in Figure 4(b), the sonar unit 80 transmits a fan-shaped sound beam over a set swath width S to acquire point cloud data representing the topography of the river channel TP. If the swath width S of the sonar unit 80 is set to 180° or more, it is also possible to acquire the cross-sectional shape of the entire river width direction.

[0057] (Calculation method) The analysis device 11 acquires various measured data (hereinafter also referred to as "measured data set") from the multicopter 12 and performs analysis and calculation in real time. More specifically, the analysis device 11 first measures the flow velocity distribution in each layer below the body of the multicopter 12, and then measures the water surface flow velocity around the body. Then, the analysis device 11 takes into account the movement speed of the multicopter 12 to calculate the actual flow velocity, i.e., adds or subtracts the movement speed of the multicopter 12 from the measured flow velocity.

[0058] Then, based on the flow velocity and the river channel topography data, the flow velocity distribution in the depth direction of the water body around the multicopter 12 is calculated. More specifically, the flow velocity distribution in the cross section of the river at the acquisition position of the measured data set is calculated. Even more specifically, when a calibration coefficient for determining the average flow velocity of each water body in the river width direction of the cross section is called a surface flow velocity coefficient, the analysis means 11 adjusts this surface flow velocity coefficient based on the measured data set. Then, by continuously determining the average flow velocity in the cross section along the direction of movement of the multicopter 12 while adjusting this surface flow velocity coefficient, the flow velocity distribution in the longitudinal direction of the river is identified.

[0059] Generally, 0.85 is used as the surface velocity coefficient for rivers. However, depending on the flow conditions and river shape, calculation results using this surface velocity coefficient may deviate from the actual situation. In the surveying system 10 of this embodiment, by adjusting this surface velocity coefficient based on a data set actually measured by the multicopter 12, calculation results that are more in line with the actual situation can be obtained. In other words, in the surveying system 10 of this embodiment, the surface velocity coefficient is applied to the water surface velocity of the water area around the multicopter 12, rather than a fixed value (0.85), i.e., a variable value, to calculate the average flow velocity. Once the average flow velocity at the cross section of the river is determined, the flow rate can be calculated using the following formula. Flow rate Q(m 3 / s) = flow velocity V (m / s) × cross-sectional area A (m 2 ) In this context, "flow rate" refers to the volume of water flowing through a cross section of a river in a given unit of time. The flow rate of a river is calculated by multiplying the flow velocity by the cross-sectional area of ​​the cross section. The unit of measurement is cubic meters per second (m 3 / s).

[0060] As mentioned above, the analysis device 11 of this embodiment accumulates survey results, which are widely shared with river operators, researchers, and others. As the surveying system 12 is repeatedly used for various flow conditions and river shapes, and the survey results are accumulated, the factors affecting the river's flow velocity distribution become increasingly clearer, based on discrepancies between actual measurements and calculated results. The degree of influence of these factors is also gradually quantified. In other words, as the surveying system 12 continues to be used, the accuracy of calculating the flow velocity distribution and discharge rate over long distances in the river improves. Currently anticipated adjustment parameters for the surface flow velocity coefficient include, for example, the flow velocity distribution and water depth below the aircraft, the water surface flow velocity and wind direction and speed around the aircraft, continuous topographical changes in the river's longitudinal and cross-sectional sections, the roughness of the bottom, and the aircraft's movement speed. Furthermore, the currently anticipated algorithm for adjusting the surface velocity coefficient is to predict the difference between the water surface velocity and the underwater average velocity from the values ​​of the above parameters based on the velocity distribution below the aircraft and the topography, and if the difference is small, increase the coefficient, and if the difference is large, decrease the coefficient. In other words, the specific parameters, variables, algorithms, etc. for adjusting the surface velocity coefficient are not currently optimal, and will be improved as the system is used more and more.

[0061] In this embodiment, the topographical data is acquired by the multicopter 12, but even if the topographical data cannot be acquired, that is, even if only the first to third measurement means are used, it is possible to obtain a flow velocity distribution and flow rate that are more in line with the actual situation than by simply applying the conventional surface flow velocity coefficient (0.85).

[0062] <River surveying method> 7 and 8 are schematic diagrams showing how the multicopter 12 rides on the water current of the river and moves down the river. A river surveying method using the surveying system 10 will be described with reference to FIGS.

[0063] When surveying a river using the survey system 10, first, the multicopter 12 is floated on the surface of the river, as shown in FIG. 7 . The multicopter 12 may travel by flight or by sailing to the starting point of the cruise plan. Once the multicopter 12 is floating on the water, the FC / BC 20 switches the multicopter 12 from flight mode to navigation mode. As described above, the FC / BC 20 continues to operate the GPS 31 and RTK receiver 32 even after switching the multicopter 12 to navigation mode (stopping the rotors 41). Once switched to navigation mode, the multicopter 12 begins scanning the water using the ADCP unit 70 and sonar unit 80.

[0064] A multicopter 12 floating on a river rides the current and moves downstream. The autonomous navigation program 22 automatically operates the thrusters 42 so that the multicopter 12 moves downstream along the navigation route R1 of the cruise plan. If the multicopter 12 deviates from the navigation route R1, it gradually returns to the navigation route R1 while descending the river (R3). At this time, the heading control program 24 controls the heading direction so that the sonar array direction of the sonar unit 80 maintains a state in which it intersects with the direction of travel of the navigation route R1 as much as possible. When the multicopter 12 reaches the designated position on the navigation route R1, the flight detour program 25 flies around the intake weir B1, an inescapable structure located along the navigation route R1 (R2). The image analysis program 231 detects a bridge pier B2 located along the navigation route R1, and the collision avoidance program 23 passes through it with the minimum deviation necessary (R4).

[0065] Here, the flow speed of a river can vary depending on the position across the river width. For example, even in areas where the river flows in a straight line, in areas with deep water, the flow speed in the center of the river is faster than the flow speed on either side due to the influence of two spiral currents aligned across the river width. Furthermore, as the river volume increases, the water level in the center rises, creating a flow on the surface from the center toward both banks. Conversely, as the river volume decreases, the water level in the center drops, creating a flow on the surface from both banks toward the center. Furthermore, in areas where the river curves, the flow speed on the outside of the curve is faster than the flow speed on the inside. Furthermore, if a floating object in deep water faces the direction of the fastest flow, it will naturally be guided toward the faster flow. Therefore, if the multicopter 12 is to be flowed along the course of the river with the fastest flow speed, it is considered sufficient that the longitude and latitude values ​​specified for the autopilot function are accurate enough to circumvent obstacles such as bridges.

[0066] As shown in Figure 8, in the case of a wide river, multiple multicopters 12 may be positioned at different positions across the river width, and each may float along the river's water current. This reduces the time required to survey a large river. Furthermore, scanning the terrain with two sonar units 80 each with a narrow swath width can reduce areas that are blocked by the beam, such as occlusion areas and shadow areas, rather than setting a wide swath width for a single sonar unit 80.

[0067] While the embodiments of the present invention have been described above, the scope of the present invention is not limited to these, and various modifications can be made without departing from the spirit of the invention. For example, although an unmanned aerial vehicle is used as the mobile object capable of moving on the water surface in the above-described embodiments, the mobile object may be an unmanned boat. [Explanation of symbols]

[0068] 10: Surveying system, 11: Analysis device (analysis means), 12: Multicopter (unmanned aerial vehicle, mobile object), 19: Operator, 20: Flight controller / boat controller, 21: Autonomous flight program, 22: Autonomous navigation program, 23: Collision avoidance program (collision avoidance means), 231: Image analysis program, 24: Heading control program, 25: Flight detouring program, 31: GPS receiver, 32: RTK receiver, 41: Rotor, 42: Thruster, 50: Float, 60: Omnidirectional camera (photography means), 70: ADCP unit (ultrasonic Doppler current meter), 71: Control unit, 80: Sonar unit (scanner device), 91: Fixed camera, 92: Drone, TP: River channel, SF: Water surface, B1: Bridge pier, B2: Intake weir, R1: Designated route, R2: Flight detouring route, R3: Return route, R4: Collision prevention route, P: Control point

Claims

1. a mobile body capable of moving on the water surface; a first measuring means for measuring a flow velocity below the moving body; a second measuring means for measuring a water surface current velocity around the moving body; and a third measuring means for measuring the moving speed of the moving object. Surveying system.

2. the first measuring means includes an ultrasonic Doppler flow meter mounted on the moving body, The surveying system according to claim 1 .

3. the second measuring means is mounted on the moving body and includes an imaging means for imaging the water surface around the moving body; The surveying system according to claim 1 .

4. the second measuring means includes one or more imaging means that capture images of a range including at least the left and right directions of the moving body when the moving body is traveling in a forward direction, The surveying system according to claim 3.

5. the moving body has a targeting unit that is a subject whose position relative to the moving body is fixed; The orientation unit is disposed at a position where it is reflected in an image captured by the imaging means. The surveying system according to claim 3.

6. The analysis means further comprises: calculating an actual flow velocity by adding the moving velocity of the moving body acquired by the third measuring means to the flow velocity acquired by the first measuring means and the flow velocity acquired by the second measuring means; The surveying system according to claim 3.

7. further comprising an analysis means; When a calibration coefficient for calculating the average value of the flow velocity distribution in the depth direction of the water area from the water surface flow velocity around the moving body acquired by the second measurement means is called a surface flow velocity coefficient, the analysis means changes the surface flow velocity coefficient based on the flow velocity below the moving object acquired by the first measurement means. The surveying system according to claim 1 .

8. The moving body further includes a scanner device for acquiring underwater topographical data; the analysis means changes the surface current velocity coefficient based on the flow velocity below the moving body acquired by the first measurement means and the underwater topography data acquired by the scanner device. The surveying system according to claim 7.

9. The moving object is an unmanned aerial vehicle. The surveying system according to claim 1 .

10. the second measuring means is mounted on the moving body and includes an imaging means for imaging the water surface around the moving body; The moving body is equipped with a collision avoidance means that, when a photograph is taken of a floating object approaching the body to within a predetermined distance, the moving body automatically takes off from the water to avoid the floating object. The surveying system according to claim 9.

11. a step of floating the moving body according to any one of claims 1 to 10 from upstream to downstream of a river on the water current of the river, River surveying methods.

12. a step of arranging the plurality of moving bodies at staggered positions in the river width direction and floating the moving bodies from upstream to downstream of the river on the water current of the river, The river surveying method according to claim 11.

13. the moving object is an unmanned aerial vehicle, a step of automatically taking off and flying the mobile body when the mobile body has descended the river to a predetermined position, and landing on the water at another position further downstream than the predetermined position; The river surveying method according to claim 11.

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