JP7530597B1 - Survey system and river survey method - Google Patents

Abstract

[Problem] To make it possible to measure the flow velocity distribution in the longitudinal and transverse sections of a water body such as a river, and its flow rate in a more realistic manner. [Solution] This is solved by a surveying system that includes a moving body capable of moving on the water surface, a first measuring means for measuring the flow velocity below the moving body, a second measuring means for measuring the water surface flow velocity around the moving body, and a third measuring means for measuring the moving speed of the moving body, and a river surveying method that includes a process of floating the moving body of the present invention on the water current of the river from the upstream to the downstream of the river. [Selected Figure] Figure 4

Description

The present invention relates to technology for measuring flow velocity distribution and flow rate in rivers, etc.

The following Patent Document 1 discloses a positioning system that uses an airship flying above a ship equipped with a camera that photographs the water surface and a Doppler current meter to determine the current position of the ship.

JP2006-300700

As flood damages become more severe due to global warming and disaster prevention legislation is strengthened, new flood control systems and river management methods that can stand up to these trends are required. However, the rivers that are the subject of management each have their own geographical and spatial characteristics, and are difficult to predict as their conditions change from moment to moment due to flooding. In order to ensure that rivers maintain the safety they should have into the future, it is necessary to clarify the mechanisms behind changes in river channels and the destruction of structures, and to be able to quantitatively predict the hydraulic impacts of rainfall and floods. In particular, understanding river flow rates and their changes during normal and flood periods is important for managing rivers. However, there is no method that can actually measure the flow velocity distribution and flow rate over long distances in the longitudinal and transverse sections of a river during flooding, and the current situation is that these are estimated based on theoretical values obtained from experiments and rules of thumb.

In view of these problems, the problem that this invention aims to solve is to make it possible to measure the flow velocity distribution and flow rate of the longitudinal and transverse sections of a water body such as a river in a manner that is more accurate to the actual situation.

To solve the above problem, the surveying system of the present invention comprises a moving body capable of moving on the water surface, a first measuring means for measuring the flow velocity below the moving body, a second measuring means for measuring the water surface flow velocity around the moving body, and a third measuring means for measuring the movement speed of the moving body.

By acquiring the flow velocity below the moving object and the surface flow velocity around it, it is possible to estimate the flow 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 flow velocity distribution in a wider water area while moving the moving object on the water surface.

In this case, it is preferable that the first measuring means includes an ultrasonic Doppler current meter mounted on the moving body. An ultrasonic Doppler current profiler (ADCP) is a device that acquires the flow velocity by emitting sound waves into water and measuring the Doppler shift of scatterers (suspended matter, etc.) that move with the water flow. 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. In addition, the ultrasonic Doppler current meter can also measure the movement speed of the moving body itself by measuring the Doppler shift of the water bottom. In other words, the ultrasonic Doppler current meter can also be used as a third measuring means.

In the surveying system of the present invention, the second measuring means may include an imaging means mounted on the moving body and adapted to capture images of the water surface around the moving body. By equipping the moving body itself with an imaging means, it becomes possible to perform surveying more easily, for example, without having to install a fixed camera around the water area to be surveyed in advance or to separately capture images of the water surface from the sky using a drone equipped with a camera.

In this case, it is preferable that 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 moving forward. This makes it possible to continuously measure the flow velocity distribution in the longitudinal and transverse sections of the water body along the moving direction of the moving body (the "vertical" direction).

In this case, the moving body preferably has an orientation part that is a subject whose relative position to the moving body is fixed, and the orientation part is preferably arranged in a position that is reflected in the image captured by the imaging means. For example, in space-time image velocimetry (STIV), in order to geometrically correct a water surface image captured from diagonally above to an image seen from directly above, orientation points whose position coordinates in real space are known are installed on the near side (camera side) of the water area to be photographed and on the opposite side. By providing an orientation part fixed to the moving body, that is, an orientation part whose position coordinates relative to the position of the imaging means equipped on the moving body are known, and including this in the angle of view of the imaging means, this can be used as an orientation point on the camera side.

The surveying system of the present invention preferably further comprises an analysis means, which calculates the actual flow velocity by adding the moving speed 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 makes it possible to eliminate errors in the flow velocity caused by the movement of the moving body itself, and to continuously acquire the flow velocity distribution of a wider range of water bodies.

The surveying system of the present invention further includes an analysis means, and when the calibration coefficient for determining the average value of the flow velocity distribution in the depth direction of the water body from the water surface flow velocity around the moving body obtained by the second measurement means is called the surface flow velocity coefficient, it is preferable that the analysis means changes the surface flow velocity coefficient based on the flow velocity below the moving body obtained 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, the calculation results using this surface flow velocity coefficient may deviate from the actual situation. By adjusting the surface flow velocity coefficient based on the actual measured flow velocity below the moving body, calculation results that are more in line with the actual situation can be obtained.

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.

In addition, in the surveying system of the present invention, the moving body may be an unmanned aerial vehicle. By allowing the moving body to move freely in three-dimensional space, it becomes possible, for example, to move to dangerous water areas and land on water safely without human intervention. It also becomes possible to fly around and avoid structures and floating objects that cannot be avoided or circumvented on the water surface.

In this case, it is preferable that the second measuring 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 aircraft to a predetermined distance. For example, in a river during flooding, the moving body may be damaged by colliding with driftwood or the like. By making the moving body an unmanned aerial vehicle and monitoring floating objects around the aircraft with the photographing means, it becomes possible to automatically avoid collisions with floating objects.

In order to solve the above problems, the river surveying method of the present invention includes a step of floating the mobile body of the present invention from the upstream to the downstream of the river on the water flow of the river. This makes it possible to continuously measure the flow velocity distribution in the longitudinal and transverse sections of the river based on actual measurements.

The river surveying method of the present invention may also include a step of arranging the multiple mobile bodies at different positions in the river width direction and floating them on the water current of the river from the upstream to the downstream. This can reduce the time required to survey a large river.

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.

In this way, the surveying system and river surveying method of the present invention make it possible to measure the flow velocity distribution and flow rate of the longitudinal and transverse sections of a water body such as a river in a more realistic manner.

FIG. 2 is a perspective view of the multicopter 12. 1 is a block diagram showing the overall configuration of a surveying system 10. FIG. FIG. 2 is a block diagram showing an automatic driving function provided in the FC/BC 20. 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 areas using the surveying system 10. FIG. FIG. 2 is a schematic diagram showing a specific example of an image analysis method for water surface current velocity in the present embodiment. FIG. 13 is a schematic diagram showing another example of the imaging means. FIG. 2 is a schematic diagram showing a multicopter 12 riding on the water current of a river and traveling down the river. 1 is a schematic diagram showing a state in which multiple multicopters 12 ride the water current of a river and move down the river.

The following describes an embodiment of the present invention with reference to the drawings. The surveying system 10 and river surveying method described below are mainly characterized by having a multicopter 12, an unmanned aerial vehicle, float on the water flow of a river, measure the flow velocity distribution by layer below the aircraft, the water surface flow velocity around the aircraft, and the river channel shape, and calculate the flow velocity distribution, average flow velocity, and flow rate of the river's longitudinal and transverse sections based on these measured values. 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 scope of "surveying" defined in the Surveying Act. In the following description, "image" refers not only to still images, but also to "video" and "video", i.e., continuous still images.

<Survey 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. Below, an overview of the surveying system 10 will be described with reference to Figs. 1 and 2.

As shown in FIG. 1, the multicopter 12 of this embodiment is a so-called hexacopter, which has six arms extending radially in a plan view and rotors 12 fixed to the tips of the arms. The multicopter 12 has a pair of pontoon-shaped floats 50 that float the aircraft on the water surface, and a pair of thrusters 42 are fixed to each float 50 to move the multicopter 12 on the water surface. In addition, 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 (cross-sectional shape of the river channel), are attached under the fuselage of the multicopter 12. In addition, two GPS receivers 31 (hereinafter simply referred to as "GPS 31"), which are GNSS (Global Navigation Satellite System) devices, are arranged outside the multicopter 12.

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.

(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, and an omnidirectional camera 60 (hereinafter simply referred to as "camera 60") which is an imaging means, which are connected to the FC/BC 20, 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), an air pressure sensor, an orientation sensor (electronic compass), and the like.

The FC/BC 20 drives the rotors 41 and thrusters 42 in response to various autopilot programs described below and instructions from the operator terminal 19 to fly and navigate the multicopter 12. In the surveying system 10 of this embodiment, the multicopter 12 is equipped with thrusters 42, which increases 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 that are thrust sources for moving in the air and two thrusters 42 that are thrust sources for moving on the water surface, and the FC/BC 20 can switch between a "flight mode" in which the rotors 41 move in the air and a "navigation mode" in which the thrusters 42 move on the water surface automatically or by instructions from the operator terminal 19. The operator can remotely control the multicopter 12 visually if it is within the field of view, and rely on images transmitted from the camera 60 if it is out of the field of view.

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 a service on the Internet through an LTE (Long Term Evolution) line. As a result, in the surveying system 10 in this embodiment, it is not necessary to install an RTK base station (fixed station) around the survey point each time, and the constraints on the distance between the RTK receiver 32 and each RTK base station are also relaxed, making it possible to carry out surveying more quickly, easily, and widely. In addition to the LTE line, the RTK receiver 32 may use other mobile communication networks such as 5G, 3G, and WiMAX (Worldwide Interoperability for Microwave Access). In this embodiment, GPS is used as the GNSS device, but this may be a receiver such as GLONASS, Galileo, Michibiki (quasi-zenith satellite system), or COMPASS (Hokuto satellite positioning system).

In this embodiment, the FC/BC 20 continues to operate the GPS 31 and the RTK receiver 32 even after the rotor 41 stops, for example, after the multicopter 12 lands on water. The speed at which the multicopter 12 moves on the water surface can be calculated from the longitude and latitude information of the GPS 31.

The camera 60 is supported above the body of the multicopter 12 and is a so-called 360° camera/celestial camera that 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 (the image analysis program 231 described below).

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.

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 flow velocity measured by the probes into a three-dimensional flow 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.

The sonar unit 80 is a multi-beam echo sounding device (a so-called multi-beam sonar) that transmits sound beams of different frequencies in a fan-shaped manner into the water and receives the reflected waves to obtain river topography data.

The sonar unit 80 is a unit equipped with a transmitter with an array of multiple sonars, a receiver that receives reflected waves, a dedicated IMU, and a surface sound speed meter. Measurements using ultrasonic waves are less affected by turbidity than optical cameras or green lasers, and more accurate topographical data can be obtained even under difficult conditions. The scanner device mounted on the multicopter 12 is not limited to the sonar unit 80, as long as it can acquire underwater topographical data after the multicopter 12 lands on the water. For example, if only still water areas with high transparency are to be surveyed, it is believed that topographical data can be acquired using a scanner device using an optical camera or laser.

(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. In addition, the operation terminal of the operator terminal 19 may have the function of the analysis device 11.

The analysis device 11 of this embodiment obtains the flow velocity distribution (or the data that is the basis for it) 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 obtains longitude and latitude values and altitude values that are corrected by the correction information of the RTK receiver 32 using the output information of the GPS 31.

Then, as will be described in detail later, the analysis device 11 calculates the flow velocity distribution and flow rate in the longitudinal and transverse sections of the river basin through which the multicopter 12 has traveled, based on various actual measurements 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, so that the load and functions of the surveying system 10 are appropriately distributed throughout the system. In addition, 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.

(Autopilot function)
3 is a block diagram showing the autopilot functions of the FC/BC 20. The multicopter 12 of this embodiment is provided with 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 as its autopilot functions. Each of the autopilot functions of the FC/BC 20 will be described below.

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, the flight altitude at each waypoint, and the flight speed between each waypoint.

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's water current and travels down the river, moves along the navigation route.

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 the image captured by the camera 60. The collision avoidance program 23 automatically operates the thrusters 42 based on the analysis results of the image analysis program 231 so that the distance between the multicopter 12 and its surrounding objects does not become less than a predetermined distance and so that the multicopter 12 does not deviate from the navigation route as much as possible. When a floating object such as driftwood is captured approaching the aircraft to a predetermined distance, the multicopter 12 automatically takes off from the water to avoid the floating object. The collision avoidance program 23 can also use a distance sensor, such as a LiDAR (Light Detection and Ranging), one or more ultrasonic distance sensors, laser distance sensors, stereo cameras, depth cameras, millimeter wave radars, etc., that are directed to the side (horizontal direction) of the body of the multicopter 12. If the camera 60 alone is not able to determine the distance to surrounding objects, these sensors may be used in combination.

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. In this embodiment, the heading control program 24 automatically operates the thrusters 42 to maintain the sonar array direction of the sonar unit 80 in a direction that intersects (as perpendicular as possible) with the direction of travel along the navigation route of the cruise plan.

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

In this way, the surveying system 10 of this embodiment is equipped with various automatic operation functions, and even when the operator terminal 19 is inexperienced or the survey is outside of visual line of sight, it is possible to perform surveys of a certain level or above of quality.

<Calculation method of flow velocity distribution and flow rate>
FIG. 4 is a schematic diagram for explaining a method for calculating the flow velocity distribution and the flow rate of a river in the longitudinal and transverse sections by the surveying system 10. In FIG.

As described above, the surveying system 10 is equipped with a first measuring means for measuring the flow velocity distribution below the multicopter 12, a second measuring means for measuring the water surface flow velocity around the aircraft, and a third measuring means for measuring the moving speed of the aircraft. The surveying system 10 of this embodiment 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 transverse sections.

(First measuring means)
In the surveying system 10, as shown in FIG. 4A, the flow velocity distribution in layers according to depth below the fuselage of the multicopter 12 (shown as A) is actually measured by the ADCP unit 70 (and the analysis device 11).

(Second measuring means)
The camera 60 of the multicopter 12 captures images of the sides and above the aircraft in a hemispherical shape (C in the figure), 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 speed around the aircraft based on the received images.

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

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 seen from directly above, so orientation points P, whose position coordinates in real space are known, are placed on the near bank (camera side) of the water area being photographed and on the opposite bank. In this embodiment, orientation points P are placed on both banks of the river (see FIG. 4(a)).

In this embodiment of the multicopter 12, an orientation unit 71 with a mark suitable for this orientation point is fixed to the aircraft, and this orientation unit 71 is reflected in the captured image as a subject. By providing an orientation unit 71 fixed to the multicopter 12, that is, an orientation unit 71 with known position coordinates relative to the position of the camera 60, 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 the one in 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 the aircraft of the multicopter 12 is fixed and it is in a position that is reflected in the captured image.

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 value features such as ripples. As shown in Figure 5(b), in STIV, the positional changes of the brightness value feature parts are arranged in chronological order, and the surface flow velocity is calculated from the gradient θ when the change in position is represented as a straight line.

In this embodiment, a 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 shore-side control point P from the multicopter 12.

Figure 6 is a schematic diagram showing another example of the photographing means. In this embodiment, the camera 60 for photographing the water surface is mounted on the multicopter 12 itself, but the mode of the photographing means is not limited to this. For example, as shown in Figure 6, a fixed camera 91 may be installed in advance along the water area to be surveyed, and the water surface current speed around the multicopter 12 may be measured from the image of this fixed camera 91. STIV using a fixed camera 91 has already had many achievements and knowledge, and can further improve the measurement accuracy of the water surface current speed. Alternatively, the water surface may be photographed from the sky separately using a so-called drone 92 equipped with a camera. By photographing the water area to be surveyed from directly above, image degradation and errors in flattening the photographed image are reduced, and the measurement accuracy of the water surface current speed can be further improved. Furthermore, the second measurement means of the present invention may be any one that can measure the water surface current speed around the multicopter 12, and is not limited to one that uses image analysis. For example, it is also possible to adopt a method of measuring the surface current speed using radio waves.

(Third measuring means)
As described above, the method for measuring the moving speed of the multicopter 12 on the water surface includes a method using the longitude and latitude information of the GPS 31 and a method using the ADCP unit 70. Either method may be adopted.

(Means for acquiring topographical data)
Returning to Fig. 4, a method for acquiring topographical data will 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 Fig. 4(b), the sonar unit 80 transmits a sound beam in a fan shape over a set swath width S, and acquires 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, the cross-sectional shape over the entire width direction of the river can also be acquired.

(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 measures the water surface flow velocity around the body. Then, the analysis device 11 takes into account the moving speed of the multicopter 12, that is, adds or subtracts the moving speed of the multicopter 12 to or from the measured flow velocity, to calculate the actual flow velocity.

Then, based on the flow velocity and the river channel topography data, the flow velocity distribution in the depth direction of the water area around the multicopter 12 is calculated. More specifically, the flow velocity distribution of the river cross section at the acquisition position of the actual measurement data set is calculated. Even more specifically, when a calibration coefficient for determining the average flow velocity in the depth direction of each water area from the water surface flow velocity of each water area 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 actual measurement data set. Then, while adjusting this surface flow velocity coefficient, the average flow velocity of the cross section is continuously obtained along the movement direction of the multicopter 12, thereby specifying the flow velocity distribution in the longitudinal direction of the river.

Generally, 0.85 is used as the surface velocity coefficient of a river. However, depending on the flow conditions and the shape of the river, the calculation results using this surface velocity coefficient may deviate from the actual situation. In the surveying system 10 of this embodiment, the surface velocity coefficient is adjusted based on the data set actually measured by the multicopter 12, so that a calculation result that is more in line with the actual situation can be obtained. That is, in the surveying system 10 of this embodiment, the surface velocity coefficient, which is not a fixed value (0.85), but a variable value, is applied to the water surface velocity of the water area around the multicopter 12 to obtain the average flow velocity. Once the average flow velocity in the cross section of the river is obtained, the flow rate can be calculated using the following formula.

Flow rate Q (m ³ /s) = flow rate V (m/s) x cross-sectional area A (m ² )

In this embodiment, "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 ( ^m3 /s).

As mentioned above, the analysis device 11 of this embodiment accumulates survey results, and the survey results are widely shared with river operators, researchers, and the like. As the survey system 12 is repeatedly used in various flow conditions and river shapes and the survey results are accumulated, the factors that affect the flow velocity distribution of the river gradually become clearer from the discrepancies between the actual measurements and the calculation results. In addition, the influence of these factors is gradually quantified according to their degree. In other words, as the survey system 12 continues to be used, the calculation accuracy of the flow velocity distribution and the flow rate over a long distance of the river improves. The adjustment parameters of the surface flow velocity coefficient currently expected include, for example, the flow velocity distribution and water depth below the aircraft, the water surface flow velocity and wind direction/speed around the aircraft, the continuous topographical changes in the vertical and cross-sectional sections of the river and the roughness of the bottom, and the movement speed of the aircraft. In addition, the currently anticipated algorithm for adjusting the surface current coefficient is to predict the difference between the water surface current velocity and the underwater average current velocity from the values of the above parameters based on the current velocity distribution below the aircraft and the topography, and if the difference is small, to increase the coefficient, and if the difference is large, to decrease the coefficient. In other words, the specific parameters, variables, algorithms, etc. for adjusting the surface current coefficient are not currently optimal, and will be improved as the system is used more.

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 accurate to the actual situation than if the conventional surface flow velocity coefficient (0.85) were simply applied.

<River survey method>
7 and 8 are schematic diagrams showing a state in which 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.

When surveying a river using the survey system 10, first, as shown in FIG. 7, the multicopter 12 is floated on the surface of the river. It may fly or navigate to the starting point of the cruise plan. Once the multicopter 12 is floated on the water, the FC/BC 20 switches the multicopter 12 from flight mode to navigation mode. As mentioned above, the FC/BC 20 continues to operate the GPS 31 and the RTK receiver 32 even after switching the multicopter 12 to navigation mode (after stopping the rotor 41). After switching to navigation mode, the multicopter 12 starts scanning the water with the ADCP unit 70 and the sonar unit 80.

The multicopter 12 floating on the river rides the water current and moves down the river. The autonomous navigation program 22 automatically operates the thrusters 42 so that the multicopter 12 moves down the river 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 where it intersects with the traveling direction of the navigation route R1 as much as possible. When the multicopter 12 descends the river to its designated position, the flight detouring program 25 flies around the intake weir B1, which is an inaccessible structure located on the navigation route R1 (R2). The image analysis program 231 detects the bridge pier B2 located on the navigation route R1, and the collision avoidance program 23 passes through it with the minimum deviation required (R4).

Here, the flow speed of a river may differ depending on the position in the river width direction. For example, even in a place where the river flows in a straight line, in a deep area, the flow speed in the center of the river is faster than the flow speed on both sides due to the influence of two spiral currents aligned in the river width direction. Also, when the water volume of the river increases, the water level in the center of the river increases, and a flow from the center to both sides occurs on the water surface. Conversely, when the water volume of the river decreases, the water level in the center of the river decreases, and a flow from both sides to the center occurs on the water surface. Also, in an area where the river is curved, the flow speed on the outside of the curved part is faster than the flow speed on the inside. And if a floating object in the deep water faces the direction where the flow speed is the fastest, it will naturally be guided to the direction where the flow speed is faster. Therefore, if it is sufficient to let the multicopter 12 flow along the course of the river with the fastest flow speed, it is considered that the longitude and latitude values specified for the autopilot function are sufficient as long as they are accurate enough to circumvent obstacles such as bridges.

As shown in FIG. 8, in the case of a wide river, multiple multicopters 12 can be positioned at staggered positions in the direction of the river width, and each can be floated along the river's water current. This can reduce the time required to survey a large river. Also, scanning the terrain with two sonar units 80 with narrow swath widths can reduce the number of blocked areas that the beam cannot reach, such as so-called occlusion areas and shadow areas, rather than setting a wide swath width for one sonar unit 80.

Although an embodiment of the present invention has been described above, the scope of the present invention is not limited to this, and various modifications can be made without departing from the spirit of the invention. For example, in the above embodiment, an unmanned aerial vehicle is used as a mobile body capable of moving on the water surface, but the mobile body may also be an unmanned boat.

10: Surveying system, 11: Analysis device (analysis means), 12: Multicopter (unmanned aerial vehicle, mobile body), 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: R TK receiver, 41: rotor, 42: thruster, 50: float, 60: omnidirectional camera (photography means), 70: ADCP unit (ultrasonic Doppler current meter), 71: orientation unit, 80: sonar unit (scanner device), 91: fixed camera, 92: drone, TP: river channel, SF: water surface, B1: bridge pier, B2: water intake weir, R1: designated route, R2: flight detour route, R3: return route, R4: collision prevention route, P: orientation point

Claims (13)

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. The first measuring means includes an ultrasonic Doppler flow meter mounted on the moving object.
The surveying system according to claim 1 . The second measurement means includes an imaging means mounted on the moving body and configured to image the water surface around the moving body.
The surveying system according to claim 1 . The second measurement 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 moving forward.
The surveying system according to claim 3. the moving body has a targeting unit which 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. The analysis means further comprises:
calculating an actual flow velocity by adding the moving speed of the moving body obtained by the third measuring means to the flow velocity obtained by the first measuring means and the flow velocity obtained by the second measuring means;
The surveying system according to claim 3. Further comprising an analysis means,
When a calibration coefficient for calculating an average value of the flow velocity distribution in the depth direction of the water body 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 current velocity coefficient based on the current velocity below the moving body acquired by the first measurement means.
The surveying system according to claim 1 . 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 current 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. The moving object is an unmanned aerial vehicle.
The surveying system according to claim 1 . the second measuring means is mounted on the moving body and includes an imaging means for imaging a water surface around the moving body;
The moving body is equipped with a collision avoidance means that, when a floating object is photographed approaching the aircraft 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. a step of floating the moving body according to any one of claims 1 to 10 from an upstream to a downstream of a river on a water current of the river,
River surveying methods. a step of disposing a plurality of the movable bodies at staggered positions in a river width direction and floating the movable bodies on the water current of the river from upstream to downstream of the river,
The river surveying method according to claim 11. The moving object is an unmanned aerial vehicle,
a step of automatically taking off and flying the moving body when the moving body reaches a predetermined position down the river, and landing on the water at another position further downstream than the predetermined position;
The river surveying method according to claim 11.

Images