A high-precision water depth measurement method of a rotor unmanned aerial vehicle

Abstract

The application discloses a kind of high-precision water depth measurement methods of rotor unmanned aerial vehicle, belong to unmanned aerial vehicle, hydrology and surveying and mapping field, including unmanned aerial vehicle quick release support, positioning device, power device and depth measuring device.Positioning device includes airborne GNSS, laser positioner, radar ranging sensor, orthographic camera and data collector;Power device includes remote control equipment, power supply step-down equipment, small motor, winch and traction rope;Depth measuring device includes microsonic echo sounder and display with WIFI receiving function.Based on the depth data correction and accurate positioning method of orthographic image, the method utilizes the microsonic echo sounder position data observed by orthographic camera, the unmanned aerial vehicle to water surface distance observed by radar ranging sensor and the unmanned aerial vehicle position and attitude data observed by airborne GNSS, realizes the correction and accurate positioning of depth data.The method is safe, mobile and accurate for hydrological survey personnel, field research personnel to obtain depth data with geographic location information.

Description

Technical Field

[0001] This invention relates to the fields of unmanned aerial vehicles (UAVs), hydrology, and surveying, specifically to a high-precision water depth measurement method and apparatus for rotary-wing UAVs, which can safely, maneuverably, and accurately acquire water depth measurement data with geographic location information. Background Technology

[0002] Water depth is a key variable for accurately calculating river flow and surface water storage. Currently, water depth observation typically employs two methods: one is to transport the sounding equipment to the observation point using manned vessels or electric cables, but this method is inefficient, lacks mobility, and carries certain risks; the other is to conduct observations using unmanned vessels, but this method is not widely applicable or maneuverable in water bodies with harsh natural conditions, complex river underlying surfaces, and high flow velocities. Therefore, there is a lack of a water depth observation method and device that simultaneously possesses advantages such as high safety, high mobility, and portability. To address this, this invention proposes a high-precision water depth measurement method and device using a rotary-wing unmanned aerial vehicle (UAV) to solve the aforementioned problems. Summary of the Invention

[0003] The technical problem solved by this invention is to provide a safe, mobile, and accurate method for measuring water depth, offering hydrological surveyors and field researchers safe, portable, and accurate water depth observation data. This includes data acquisition, correction, and precise positioning of depth measurement data from sounding equipment. Based on the observation of river cross-sections using UAV-guided sounding equipment at different flow velocities, the results show good agreement with actual measured cross-sections, achieving an accuracy of approximately 2-5% of the actual water depth. In high-velocity areas, the depth measurement accuracy is significantly improved after correction using the method of this invention.

[0004] To solve the above-mentioned technical problems, the technical solution proposed by this invention is: a high-precision water depth measurement method for a rotary-wing UAV: ​​the high-precision water depth measurement device for a rotary-wing UAV includes a quick-release bracket for the UAV, a positioning device, a power unit, a depth measuring device, and a UAV remote controller 26. The quick-release bracket for the UAV includes a quick-release device 2, a first top plate 4, a second top plate 6, a third top plate 7, a shock-absorbing ball 8, and a support plate 9; the positioning device includes an airborne GNSS 10, a laser locator 17, a radar ranging sensor 18, an orthophoto camera 20, and a data acquisition device 22; the power unit includes a power step-down device 21, a twisted wire reel 12, a traction rope 13, an emergency brake switch 14, an emergency brake switch trigger 15, a small motor 19, a power unit remote control signal receiving device 11, and a power unit lifting and stopping control stick 23; the depth measuring device includes a miniature sonar 16 and a display 27 with WIFI receiving function.

[0005] The first top plate 4 and the second top plate 6 are fixedly connected. The first top plate 4 is fixedly connected to the quick-release device 2. The third top plate 7 is connected to the second top plate 6 by shock-absorbing balls 8. The airborne GNSS 10, laser locator 17, radar ranging sensor 18, orthophoto camera 20, data acquisition unit 22, power step-down device 21, twisted wire spool 12, traction rope 13, emergency brake switch 14, emergency brake switch trigger 15, small motor 14 and power unit remote control signal receiver 11 are fixed by the bracket plate 9 and connected to the third top plate 7. The airborne GNSS 10 is fixed directly above the laser locator 17. The laser locator 17 is fixed to the base plate 9-1 of the bracket plate 9, close to the orthophoto camera 20. The radar ranging sensor 18 and the orthophoto camera 20 are fixed to the base plate 9-1. The twisted wire reel 12 is connected to the shaft of the small motor 19; one end of the traction rope 13 is fixed to the twisted wire reel 12, and the other end is fixed to the miniature sonar 16; the emergency brake switch 14 is fixed to the base plate 9-1; the emergency brake switch trigger 15 is fixed to the end of the traction rope 13; one end of the traction rope 13 is fixed to the twisted wire reel 12, and the other end is fixed to the miniature sonar 16; the power unit lifting and stopping control stick 23, the orthophoto camera photo button 24, and the drone remote controller screen 25 are integrated into the drone remote controller 26;

[0006] The quick-release bracket includes a quick-release device 2, a first top plate (4), a second top plate (6), a third top plate (7), shock-absorbing balls 8, and a device fixing bracket 9. The first top plate (4), the second top plate (6), the third top plate (7), and the device fixing bracket 9 are made of high-strength, lightweight carbon fiber and are connected by shock-absorbing balls 8 to reduce the stress on the UAV.

[0007] The positioning device includes an airborne GNSS 10, a laser locator 17, a radar ranging sensor 18, an orthophoto camera 20, and a data acquisition unit 22. The airborne GNSS 10 is used to acquire the position and attitude data of the UAV; the laser locator 17 is used to locate the position of the airborne GNSS on the water surface; the radar ranging sensor 18 is used to acquire the distance from the UAV to the water surface; the orthophoto camera 20 is used to determine the relative position of the laser positioning point and the miniature sonar 16; and the data acquisition unit 22 is used to acquire the observation data of the airborne GNSS 10 and the radar ranging sensor 18.

[0008] The power unit includes a power step-down device 21, a stranded wire reel 12, a traction rope 13, an emergency brake switch 14, an emergency brake switch trigger 15, a small motor 19, a power unit remote control signal receiver 11, and a power unit lifting and stopping control lever 23. One end of the traction rope 13 is connected to the stranded wire reel 12, and the other end is connected to the miniature sonar 16. The small motor 19 is controlled to rotate forward, reverse, and stop via the power unit lifting and stopping control lever 23 to achieve the function of raising, lowering, and stopping the miniature sonar 16.

[0009] The depth sounding device includes a miniature sonar 16 and a display 27 with WIFI receiving function. The display 27 with WIFI receiving function displays and records water depth observation data through the WIFI connection emitted by the miniature sonar 16.

[0010] The steps of the high-precision water depth measurement method using a rotary-wing UAV are as follows:

[0011] Step 1: The remote controller 26 sends a command to the drone 1. The drone hovers directly above the point to be measured. The remote controller 26 controls the sonar lift-down control stick 23 to make the miniature sonar 16 descend to the water surface.

[0012] Step 2: Turn on the display 27 with WIFI receiving function and connect to the WIFI emitted by the miniature sonar. Once the WIFI connection is successful, the display 27 with WIFI receiving function will display the water depth observation data.

[0013] Step 3: Data acquisition. After the depth measurement data stabilizes, record for 10 seconds. During this process, send a photo-taking command to the orthophoto camera 20 via the remote controller 26 to record the relative position of the micro sonar 16 and the laser point emitted by the laser locator 17. Then, operate the sonar lifting and stopping control stick 23 of the remote controller 26 to retrieve the micro sonar 16 to the drone.

[0014] Step four, data download: Data acquisition unit 22 downloads data from airborne GNSS 10 and radar ranging sensor 18, including time, longitude, latitude, altitude, heading angle, lateral angle, roll angle, and distance data from the UAV to the water surface; downloads photos from orthophoto camera 20; downloads raw observation data from miniature sonar 16, including longitude, latitude, water depth, and time; the data downloaded by data acquisition unit 22 and the raw observation data from miniature sonar 16 can be correlated in time to achieve synchronous observation;

[0015] Step 5: Precise positioning of the miniature sonar 16, using an image recognition-based precise positioning method; utilizing the position information of the miniature sonar 16 observed by the orthophoto camera 20 and the distance H between the UAV and the water surface observed by the radar ranging sensor 18. z The data, along with the UAV's position and attitude data from airborne GNSS10 observations, were used for positioning using geometric theory, including H... z The calibration and precise positioning of the miniature sonar 16 are carried out through the following steps:

[0016] (1)H z Correction

[0017] Due to the influence of the drone's flight attitude, the distance H between the drone and the water surface observed by radar ranging sensor 18 is... z This is not a strictly vertical distance and requires further correction; H zThe camera parameter, the only variable in the derivation of this method's formulas, is a fixed value. Equations 1-5 and 1-6 form the basis for deriving subsequent formulas and directly affect observation accuracy. Based on geometric theory, the distance correction formula from the UAV to the water surface is derived as follows:

[0018]

[0019]

[0020] In the formula: μ is the pitch angle, θ is the roll angle, observed by airborne GNSS, in degrees;

[0021] Let OD = x, then

[0022] By OB 2 +OD 2 =AC 2 -OA 2 have to:

[0023]

[0024]

[0025] Equation 1-4 is H z Correction formula;

[0026] (2) Miniature sonar 16 precise positioning

[0027] The micro sonar 16 accurately locates UAV positions at the centimeter level using image recognition methods. The precise positioning formula for the micro sonar 16 is derived as follows:

[0028] ⑤ Determine the field of view of the orthophoto

[0029]

[0030]

[0031] In the formula: P L P represents the field of view length of an orthophoto, in meters (m). w V represents the field of view width of an orthophoto, in mm. L V represents the length of the long side of an orthophoto camera, in mm. w The f-axis represents the short side dimension of an orthophoto camera, in mm; the f-axis represents the focal length of the camera lens, in mm; and the H-axis represents... z The distance from the corrected drone to the water surface is in meters (m).

[0032] ⑥ Determine the relative positions of the miniature sonar and the laser positioning point.

[0033]

[0034]

[0035]

[0036] α=τ+ω 1-10

[0037] In the formula: P Li and P wi The lengths of the large and small dots in the horizontal and vertical directions of the orthophoto are respectively represented in meters (m); N. L and N w N represents the number of pixels on the long and short sides of the orthophoto, respectively. Li and N wi ω represents the number of pixels in the horizontal and vertical directions of the large and small dots in the orthophoto, respectively; ω is the heading angle, observed by airborne GNSS, in degrees; α is the angle between the projection of the traction rope on the water surface and due north, in degrees; τ is the angle between the projection line of the traction rope on the water surface and the direction of the short side of the orthophoto, in degrees.

[0038] ⑦ Determine the correction distance for the miniature sonar

[0039]

[0040] L x =R×sinα 1-12

[0041] L y =R×cosα 1-13

[0042] In the formula: R is the projected distance of the traction rope on the water surface, in meters; L x and L y These represent the corrected distances for the micro sonar-enabled UAV's position in the north and east coordinates, respectively.

[0043] ⑧ Determine the precise location information of the miniature sonar

[0044] N 声 =N 无 -L y 1-14

[0045] E 声 =E 无 -L x 1-15

[0046] Where: N 声 and E 声 Let N represent the north and east coordinates of the miniature sonar, respectively, in meters (m) and N. 无 and E 无 Let these be the north and east coordinates of the UAV, respectively, in meters (m).

[0047] Step Six: Correction of Miniature Sonar 16 Observation Data. Due to the impact of water flow, the water depth observed by Miniature Sonar 16 is often greater than the actual water depth, requiring further correction. On calm water surfaces, the water depth observed by the Miniature Sonar is the actual water depth and requires no correction. Based on time synchronization, the water depth at the same time as the captured images is selected for correction. The correction formula is derived as follows:

[0048]

[0049]

[0050] In the formula: β is the angle between the traction rope and the water surface, in degrees; H 实 The corrected observed water depth is in meters (m).

[0051] Preferably, the first top plate 4 and the second top plate 6 are connected by screws 5. The first top plate is connected to the quick-release device 2 by screws. The third top plate 7 is connected to the second top plate 6 by shock-absorbing balls 8. The second top plate 6 is U-shaped, with only the carbon fiber plates around the perimeter used to install the shock-absorbing balls 8 and screws 5. The third top plate 7 bears the entire weight of the equipment, and the force is transferred to the second top plate 6 through the shock-absorbing balls 8 to achieve a shock absorption effect. The equipment fixing bracket uses bracket plates 9 to fix the airborne GNSS 10, laser locator 17, radar ranging sensor 18, orthophoto camera 20, data acquisition unit 22, power step-down device 21, stranded coil 12, traction rope 13, emergency brake switch 14, emergency brake switch trigger 15, small motor 14, and power unit remote control signal receiver 11 to a certain size and connect them to the third top plate 7. All the above plates are made of high-strength and lightweight carbon fiber plates.

[0052] Preferably, the airborne GNSS 10 records the UAV's position and attitude data, including time, longitude, latitude, elevation, heading angle, pitch angle, and roll angle, and is fixed directly above the laser locator 17. The laser locator 17 illuminates the water surface to form a clear light spot and is fixed to the base plate 9-1, close to the orthophoto camera 20. The radar ranging sensor 18 can accurately measure the distance between the UAV and the water surface and is fixed to the base plate 9-1. The orthophoto camera 20 is a correctly calibrated optical camera and is fixed to the base plate 9-1. The data acquisition unit 22 supports the acquisition and storage of serial port data signals in 485 and 232 formats.

[0053] Preferably, the power supply step-down device 21 uses a transformer that can stably convert high-voltage DC power to 5-12V DC power; the stranded coil 12 is connected to the shaft of the small motor 19, made of carbon fiber material, with a U-shaped groove design, a groove length of 15mm, and inner and outer diameters of 20mm and 10mm respectively; one end of the traction rope 13 is fixed to the stranded coil 12, and the other end is fixed to the miniature sonar 16; the minimum traction force of the small motor 19 is not less than 10N, and it supports forward rotation, reverse rotation, and stop; the emergency brake switch 14 is a miniature pressure switch that immediately cuts off power when pressed, and is fixed to the base plate 9-1; the emergency brake switch trigger 15 is a carbon fiber rod fixed to the end of the traction rope; the power unit remote control signal receiver 11 is a 5-12V DC remote controller with an effective control distance of not less than 100m; the power unit lifting and stopping control stick 23 is integrated into the UAV remote controller 26.

[0054] Preferably, the miniature sonar 16 is circular in shape, with a diameter not exceeding 100mm, a mass not exceeding 500g, a minimum depth-sounding distance not less than 80m, and can float on the water surface; it can store raw observation data, including time and water depth; it has a built-in rechargeable lithium battery and a WIFI transmitter, enabling independent observation and wireless transmission of observation data. A display 27 with WIFI receiving function can connect to the WIFI signal emitted by the miniature sonar 16.

[0055] Beneficial effects:

[0056] Compared with existing water depth measurement methods, it can safely, mobilely and accurately acquire water depth observation data with geographical location information;

[0057] The quick-release bracket is made of high-strength, lightweight carbon fiber plate, which is both strong and lightweight. In terms of structure, shock-absorbing balls are used to connect the power compartment to the drone, which reduces the stress on the drone from the entire device.

[0058] The positioning device described above is based on a method for correcting and accurately positioning depth measurement data from orthophotos. This method utilizes the position data of miniature sonar observed by an orthophoto camera, the distance from the UAV to the water surface observed by a radar ranging sensor, and the position and attitude data of the UAV observed by an airborne GNSS to achieve the correction and accurate positioning of depth measurement data, providing a foundation for drawing underwater topographic maps.

[0059] The miniature sonar of the depth sounding device can float on the water surface, ensuring the accuracy of water depth observation; by connecting the sonar to a display with WIFI receiving function through WIFI, remote transmission and storage of observation data can be realized. Attached Figure Description

[0060] The present invention will be further described below with reference to the accompanying drawings.

[0061] Figure 1This is a schematic diagram of the overall structure of the present invention.

[0062] Figure 2 This is the present invention. Figure 1 Enlarged view of point A.

[0063] Figure 3 This is a schematic diagram illustrating the principle of distance correction between a drone and the water surface.

[0064] Figure 4 This is a schematic diagram of the principle of a miniature sonar for precise positioning based on UAV orthophotos. Figure a is a geometric positioning diagram of the UAV-tractioned depth sounding device; Figure b is a schematic diagram of the relative position of the orthophoto analysis depth sounding device and the UAV GNSS water surface projection point.

[0065] Figure 5 This is a schematic diagram of the correction of observation data from a miniature sonar.

[0066] Figure 6 Figure A shows an embodiment of the present invention. Figure A is an accuracy evaluation diagram of the depth sounding device based on UAV orthophoto image positioning; Figure B is a cross-sectional view of a river channel observed by a UAV equipped with a depth sounding device, where Figure a is a river channel cross-section with calm water surface, and Figure b is a river channel cross-section with a combination of calm water surface and high-velocity water surface.

[0067] In the diagram: 1-Rotor UAV, 2-Quick release device, 3-GNSS antenna, 4-First top plate, 5-Screw, 6-Second top plate, 7-Third top plate, 8-Shock absorber ball, 9-Bracket plate, 10-Airborne GNSS, 11-Power unit remote control signal receiver, 12-Twisted cable reel, 13-Tether rope, 14-Emergency brake switch, 15-Emergency brake switch trigger, 16-Miniature sonar, 17-Laser locator, 18-Radar ranging sensor, 19-Small motor, 20-Orthophoto camera, 21-Power supply step-down device, 22-Data collector, 23-Power unit lifting and stopping control stick, 24-Orthophoto camera photo button, 25-UAV remote controller screen, 26-Control remote controller, 27-Display with WIFI receiving function. Detailed Implementation

[0068] The technical solution of the present invention will be further described in detail below with reference to the specification and accompanying drawings.

[0069] A high-precision water depth measurement device for a rotary-wing unmanned aerial vehicle (UAV) includes a quick-release bracket for the UAV, a positioning device, a power unit, and a depth measuring device. The high-precision water depth measurement device for the rotary-wing UAV includes a quick-release bracket for the UAV, a positioning device, a power unit, a depth measuring device, and a UAV remote controller (26). The quick-release bracket for the UAV includes a quick-release device (2), a first top plate (4), a second top plate (6), a third top plate (7), a shock-absorbing ball (8), and a support plate (9). The positioning device includes an airborne GNSS (10), a laser locator (17), a radar ranging sensor (18), an orthophoto camera (20), and a data acquisition device (22). The power unit includes a power step-down device (21), a twisted wire reel (12), a traction rope (13), an emergency brake switch (14), an emergency brake switch trigger (15), a small motor (19), a power unit remote control signal receiving device (11), and a power unit lifting and stopping control stick (23). The depth measuring device includes a miniature sonar (16) and a display with WIFI receiving function (27).

[0070] The first top plate (4) and the second top plate (6) are fixedly connected. The first top plate (4) is fixedly connected to the quick-release device (2). The third top plate (7) is connected to the second top plate (6) using shock-absorbing balls (8). The airborne GNSS (10), laser locator (17), radar ranging sensor (18), orthophoto camera (20), data acquisition unit (22), power step-down device (21), stranded coil (12), traction rope (13), emergency brake switch (14), emergency brake switch trigger (15), small motor (14), and power unit remote control signal receiver (11) are fixed using a bracket plate (9) and connected to the third top plate (7). The airborne GNSS (10) is fixed directly above the laser locator (17). The laser locator (17) is fixed to the bracket plate (9). The base plate (9-1) is close to the orthophoto camera (20); the radar ranging sensor (18) and the orthophoto camera (20) are fixed to the base plate (9-1). The twisted wire reel (12) is connected to the shaft of the small motor (19); one end of the traction rope (13) is fixed to the twisted wire reel (12), and the other end is fixed to the miniature sonar (16); the emergency brake switch (14) is fixed to the base plate (9-1); the emergency brake switch trigger (15) is fixed to the end of the traction rope (13); one end of the traction rope (13) is fixed to the twisted wire reel (12), and the other end is fixed to the miniature sonar (16); the power unit lifting and stopping control stick (23), the orthophoto camera photo button (24), and the drone remote controller screen (25) are integrated into the drone remote controller (26);

[0071] A high-precision water depth measurement device for a rotary-wing unmanned aerial vehicle (UAV) includes a quick-release bracket for the UAV, a positioning device, a power unit, and a depth measuring device.

[0072] The quick-release bracket includes a quick-release device (2), a first top plate (4), screws (5), a second top plate (6), a third top plate (7), shock-absorbing balls (8), and a device fixing bracket (9). The first top plate (4), the second top plate (6), the third top plate (7), and the device fixing bracket (9) are made of high-strength, lightweight carbon fiber and are connected by shock-absorbing balls (8) to reduce the stress on the UAV.

[0073] The positioning device includes an airborne GNSS (10), a laser locator (17), a radar ranging sensor (18), an orthophoto camera (20), and a data acquisition unit (22). The airborne GNSS (10) is used to acquire the position and attitude data of the UAV; the laser locator (17) is used to locate the position of the airborne GNSS on the water surface; the radar ranging sensor (18) is used to acquire the distance from the UAV to the water surface; the orthophoto camera (20) is used to determine the relative position of the laser positioning point and the miniature sonar (16); and the data acquisition unit (22) is used to acquire the observation data of the airborne GNSS (10) and the radar ranging sensor (18).

[0074] The power unit includes a power step-down device (21), a stranded wire reel (12), a traction rope (13), an emergency brake switch (14), an emergency brake switch trigger (15), a small motor (19), a power unit remote control signal receiver (11), and a power unit lifting and stopping control lever (23). One end of the traction rope (13) is connected to the stranded wire reel (12), and the other end is connected to the miniature sonar (16). The small motor (19) is controlled to rotate forward, reverse, and stop by the power unit lifting and stopping control lever (23) to realize the function of raising, lowering, and stopping the miniature sonar (16).

[0075] The depth measuring device includes a miniature sonar (16) and a display (27) with WIFI receiving function. The display (27) with WIFI receiving function displays and records water depth observation data through the WIFI connection emitted by the miniature sonar (16).

[0076] The high-precision water depth measurement method for rotary-wing UAVs proposed in this invention includes the following specific steps:

[0077] Step 1: The remote controller (26) sends a command to the drone (1). The drone hovers directly above the point to be measured. The remote controller (26) controls the sonar lift-up and stop control stick (23) to make the miniature sonar (16) land on the water surface.

[0078] Step 2: Turn on the monitor (27) with WIFI receiving function and connect to the WIFI emitted by the miniature sonar. Once the WIFI connection is successful, the monitor (27) with WIFI receiving function will display the water depth observation data.

[0079] Step 3, data acquisition. After the depth measurement data stabilizes, record for 10 seconds. During this process, send a photo-taking command to the orthophoto camera (20) via the remote controller (26) to record the relative position of the laser point emitted by the micro sonar (16) and the laser locator (17). Then, operate the sonar lifting and stopping control stick (23) of the remote controller (26) to retrieve the micro sonar (16) to the UAV.

[0080] Step 4, data download: The data acquisition unit (22) downloads data from the airborne GNSS (10) and radar ranging sensor (18), including time, longitude, latitude, altitude, heading angle, lateral angle, roll angle, and distance data from the UAV to the water surface; downloads photos from the orthophoto camera (20); and downloads raw observation data from the micro sonar (16), including longitude, latitude, water depth, and time. It should be noted that the data downloaded by the CR 300 data acquisition unit (22) and the raw observation data from the micro sonar (16) can be correlated through time to achieve synchronous observation.

[0081] Step 5, precise positioning of the miniature sonar (16). This invention proposes a precise positioning method based on image recognition; this method utilizes the position information of the miniature sonar (16) observed by the orthophoto camera (20) and the distance (H) between the UAV and the water surface observed by the radar ranging sensor (18). z The data, along with the UAV position and attitude data observed by airborne GNSS (10), are used for positioning based on geometric theory, including H... z The calibration and precise positioning of the miniature sonar (16) are carried out in the following steps:

[0082] (1)H z Correction

[0083] Affected by the flight attitude of the UAV, the distance (H) between the UAV and the water surface observed by the radar ranging sensor (18) z This is not a strictly vertical distance and requires further correction. Based on geometric theory, the distance correction formula for the UAV to the water surface is derived as follows:

[0084]

[0085]

[0086] In the formula: μ is the pitch angle, θ is the roll angle, observed by airborne GNSS, in degrees;

[0087] Let OD = x, then

[0088] By OB 2 +OD 2 =AC 2 -OA 2have to:

[0089]

[0090]

[0091] Equation (1-4) is H z Correction formula.

[0092] (2) Miniature sonar (16) Precise positioning

[0093] This invention uses high-precision UAV location information (centimeter level) to accurately locate a miniature sonar (16) through image recognition. Based on geometric theory, the precise positioning formula for the miniature sonar (16) is derived as follows:

[0094] ① Determine the field of view of the orthophoto

[0095]

[0096]

[0097] In the formula: P L P represents the field of view length of an orthophoto, in meters (m). w V represents the field of view width of an orthophoto, in mm. L V represents the length of the long side of an orthophoto camera, in mm. w The f-axis represents the short side dimension of an orthophoto camera, in mm; the f-axis represents the focal length of the camera lens, in mm; and the H-axis represents... z The distance from the corrected drone to the water surface is in meters (m).

[0098] ② Determine the relative positions of the miniature sonar and the laser positioning point.

[0099]

[0100]

[0101]

[0102] α=τ+ω (1-10)

[0103] In the formula: P Li and P wi The lengths of the large and small dots in the horizontal and vertical directions of the orthophoto are respectively represented in meters (m); N. L and N w N represents the number of pixels on the long and short sides of the orthophoto, respectively. Li and N wiω represents the number of pixels in the horizontal and vertical directions of the large and small dots in the orthophoto, respectively; ω is the heading angle, observed by airborne GNSS, in degrees; α is the angle between the projection of the traction rope on the water surface and due north, in degrees; τ is the angle between the projection line of the traction rope on the water surface and the direction of the short side of the orthophoto, in degrees.

[0104] ③ Determine the correction distance for the miniature sonar

[0105]

[0106] L x =R×sinα (1-12)

[0107] L y =R×cosα (1-13)

[0108] In the formula: R is the projected distance of the traction rope on the water surface, in meters; L x and L y These represent the corrected distances of the micro sonar-based UAV's location in the north and east coordinates, respectively.

[0109] ④ Determine the precise location information of the miniature sonar

[0110] N 声 =N 无 -L y (1-14)

[0111] E 声 =E 无 -L x (1-15)

[0112] Where: N 声 and E 声 Let N represent the north and east coordinates of the miniature sonar, respectively, in meters (m) and N. 无 and E 无 Let m represent the north and east coordinates of the UAV, respectively.

[0113] Step Six: Correction of Miniature Sonar (16) Observation Data. Due to the impact of water flow, the observed water depth by the miniature sonar (16) is often greater than the actual water depth, requiring further correction. It should be noted that the water depth observed by the miniature sonar on a calm water surface is the actual water depth. Based on geometric theory, the correction formula is derived as follows:

[0114]

[0115]

[0116] In the formula: β is the angle between the traction rope and the water surface, in degrees; H 实 The corrected observed water depth is in meters (m).

[0117] According to the present invention, a high-precision water depth measurement method and device for rotary-wing UAVs was designed and assembled. The device includes: a quick-release bracket, a quick-release device (KOBIT Vanguard I quick-release interface), a shock-absorbing ball (17.5mm×20mm gimbal shock-absorbing ball), a first top plate (4), a second top plate (6), a third top plate (7), and a device fixing bracket (9) made of 2mm carbon fiber plate; a positioning device, an airborne GNSS (UPK100 airborne GNSS), a laser locator (infrared laser with input voltage of 5V DC), a radar ranging sensor (24GHz radar ranging chip with input voltage of 12V), an orthophoto camera (SONY-102 / 35mm camera), and a data acquisition device (CR300 data acquisition device); a power unit, a power supply step-down device (17-58V to 5-12V, 1A DC transformer), a stranded wire reel (carbon fiber U-shaped groove), and a traction rope ( 0.2mm fishing line), emergency brake switch (miniature pressure switch), emergency brake switch trigger ( The system includes a 2mm carbon fiber rod, a small motor (12V input, 100r / min speed, 3.5Kgf·cm rated torque DC motor for both forward and reverse rotation), a power unit remote control signal receiver (12V DC remote controller), and a power unit lift and stop control stick (integrated into the drone remote controller). The depth sounding device includes a micro sonar (Deeper Chirp+ micro sonar) and a display (mobile phone) with WIFI reception capability.

[0118] After assembling the equipment, this experiment verified the Huzhuang Sanhe section of the Chuzhou Field Hydrological Base of the Nanjing Hydraulic Research Institute according to the steps provided in this method, involving the verification of positioning accuracy and depth sounding accuracy. Considering the difficulty of verifying positioning accuracy in water, this invention transplants the positioning accuracy verification to the ground, that is, on the ground, the depth sounding equipment and the UAV are artificially offset by a certain distance on the horizontal projection plane to simulate the relative position of the depth sounding equipment and the UAV under the impact of water flow. The verification of positioning accuracy and depth sounding accuracy both use the measured data of Huace RTK GNSS (I70) as the true value. Through verification, the positioning accuracy of the depth sounding equipment based on UAV orthophoto images is good, and the consistency with the RTK observation values ​​is high. Figure 6 (A)), with an accuracy of approximately 5% of the drone's hovering height (≤10m). Based on the river cross-section observed by the drone-guided depth sounding equipment at different flow velocities ( Figure 6 (B) shows good agreement with the measured cross-section, with an accuracy of approximately 2-5% of the actual water depth; after correction, the depth measurement accuracy in the high-velocity region is significantly improved. Figure 6 (Bb). This level of depth sounding and positioning accuracy is acceptable for most inland water bodies.

Claims

1. A high-precision water depth measurement method for a rotary-wing unmanned aerial vehicle (UAV), characterized in that: The high-precision water depth measurement device for a rotary-wing UAV includes a quick-release bracket, a positioning device, a power unit, a depth measuring device, and a UAV remote controller (26). The quick-release bracket includes a quick-release device (2), a first top plate (4), a second top plate (6), a third top plate (7), a shock-absorbing ball (8), and a support plate (9). The positioning device includes an airborne GNSS (10), a laser locator (17), a radar ranging sensor (18), an orthophoto camera (20), and a data acquisition unit (22). The power unit includes a power step-down device (21), a cable reel (12), a traction rope (13), an emergency brake switch (14), an emergency brake switch trigger (15), a small motor (19), a power unit remote control signal receiver (11), and a power unit lifting and stopping control stick (23). The depth measuring device includes a miniature sonar (16) and a display with WIFI receiving function (27). The first top plate (4) and the second top plate (6) are fixedly connected. The first top plate (4) is fixedly connected to the quick-release device (2). The third top plate (7) is connected to the second top plate (6) using shock-absorbing balls (8). The airborne GNSS (10), laser locator (17), radar ranging sensor (18), orthophoto camera (20), data acquisition unit (22), power step-down device (21), twisted wire reel (12), traction rope (13), emergency brake switch (14), emergency brake switch trigger (15), small motor (14) and power unit remote control signal receiver (11) are fixed using bracket plate (9) and connected to the third top plate (7). The airborne GNSS (10) is fixed directly above the laser locator (17). (17) The base plate (9-1) is fixed to the bracket plate (9) and close to the orthophoto camera (20); the radar ranging sensor (18) and the orthophoto camera (20) are fixed to the base plate (9-1); the twisted wire reel (12) is connected to the shaft of the small motor (19); one end of the traction rope (13) is fixed to the twisted wire reel (12) and the other end is fixed to the miniature sonar (16); the emergency brake switch (14) is fixed to the base plate (9-1); the emergency brake switch trigger (15) is fixed to the end of the traction rope (13); one end of the traction rope (13) is fixed to the twisted wire reel (12) and the other end is fixed to the miniature sonar (16); the power unit lifting and stopping control lever (23), the orthophoto camera photo button (24), and the drone remote controller screen (25) are integrated into the drone remote controller (26); The steps of the high-precision water depth measurement method using a rotary-wing UAV are as follows: Step 1: The remote controller (26) sends a command to the drone (1). The drone hovers directly above the point to be measured. The remote controller (26) controls the sonar lift-up and stop control stick (23) to make the miniature sonar (16) land on the water surface. Step 2: Turn on the monitor (27) with WIFI receiving function and connect to the WIFI emitted by the miniature sonar. Once the WIFI connection is successful, the monitor (27) with WIFI receiving function will display the water depth observation data. Step 3, data acquisition. After the depth measurement data stabilizes, record for 10 seconds. During this process, send a photo-taking command to the orthophoto camera (20) via the remote controller (26) to record the relative position of the laser point emitted by the micro sonar (16) and the laser locator (17). Then, operate the sonar lifting and stopping control stick (23) of the remote controller (26) to retrieve the micro sonar (16) to the drone. Step 4, data download: The data acquisition unit (22) downloads data from the airborne GNSS (10) and radar ranging sensor (18), including time, longitude, latitude, altitude, heading angle, lateral angle, roll angle, and distance data from the UAV to the water surface; downloads photos from the orthophoto camera (20); downloads raw observation data from the miniature sonar (16), including longitude, latitude, water depth, and time; the data downloaded by the data acquisition unit (22) and the raw observation data from the miniature sonar (16) can be correlated by time to achieve synchronous observation; Step 5, precise positioning of the miniature sonar (16), based on image recognition; using the position information of the miniature sonar (16) observed by the orthophoto camera (20) and the distance H from the UAV to the water surface observed by the radar ranging sensor (18). z The data, along with the UAV's position and attitude data from airborne GNSS10 observations, were used for positioning using geometric theory, including H... z The calibration and precise positioning of the miniature sonar (16) are carried out in the following steps: (1)H z Correction Affected by the flight attitude of the UAV, the distance H between the UAV and the water surface observed by the radar ranging sensor (18) z This is not a strictly vertical distance and requires further correction; H z The camera parameter, the only variable in the derivation of this method's formulas, is a fixed value. Equations 1-5 and 1-6 form the basis for deriving subsequent formulas and directly affect observation accuracy. Based on geometric theory, the distance correction formula from the UAV to the water surface is derived as follows: In the formula: μ is the roll angle, θ is the pitch angle, observed by airborne GNSS, in degrees; Let OD = x, then By OB 2 +OD 2 =AC 2 -OA 2 have to: Equation 1-4 is H z Correction formula; (2) Miniature sonar (16) Precise positioning The high-precision UAV location information is used to accurately locate the micro sonar (16) at the centimeter level using image recognition methods; the accurate positioning formula of the micro sonar (16) is derived as follows: ① Determine the field of view of the orthophoto In the formula: P L P represents the field of view length of an orthophoto, in meters (m). w V represents the field of view width of an orthophoto, in mm. L V represents the length of the long side of an orthophoto camera, in mm. w The f-axis represents the short side dimension of an orthophoto camera, in mm; the f-axis represents the focal length of the camera lens, in mm; and the H-axis represents... z The corrected distance from the drone to the water surface, in meters (m); ② Determine the relative positions of the miniature sonar and the laser positioning point. α=τ+ω (1-10) In the formula: P Li and P wi The lengths of the large and small dots in the horizontal and vertical directions of the orthophoto are respectively represented in meters (m); N. L and N w N represents the number of pixels on the long and short sides of the orthophoto, respectively. Li and N wi ω represents the number of pixels in the horizontal and vertical directions of the orthophoto, respectively; ω is the heading angle, observed by airborne GNSS, in degrees; α is the angle between the projection of the traction rope on the water surface and true north, in degrees; τ is the angle between the projection line of the traction rope on the water surface and the short side of the orthophoto, in degrees. ③ Determine the correction distance for the miniature sonar L x =R×sinα (1-12) L y =R×cosα (1-13) In the formula: R is the projected distance of the traction rope on the water surface, in meters; L x and L y These represent the corrected distances for the micro sonar-enabled UAV's position in the north and east coordinates, respectively. ④ Determine the precise location information of the miniature sonar N 声 < N 无 -L y (1-14) AND 声 =And 无 -THE x (1-15) Where: N 声 and E 声 Let these be the north and east coordinates of the miniature sonar, respectively, in meters (m). N 无 and E 无 Let these be the north and east coordinates of the UAV, respectively, in meters (m). Step 6: Correction of the observation data of the miniature sonar (16). Due to the impact of water flow, the water depth observed by the miniature sonar (16) is often greater than the actual water depth, requiring further correction. The water depth observed by the miniature sonar on a calm water surface is the actual water depth, and no correction is needed. Based on time synchronization, the water depth at the same time as the photograph is taken is selected for correction, and the correction formula is derived as follows: In the formula: β is the angle between the traction rope and the water surface, in degrees; H 实 The corrected observed water depth is in meters (m).

2. The high-precision water depth measurement method for a rotary-wing UAV according to claim 1, characterized in that: The first top plate (4) and the second top plate (6) are connected by screws (5). The first top plate is connected to the quick-release device (2) by screws. The third top plate (7) is connected to the second top plate (6) by shock-absorbing balls (8). The second top plate (6) is U-shaped, with only the carbon fiber plates around the perimeter reserved for installing the shock-absorbing balls (8) and screws (5). The third top plate (7) bears the entire weight of the equipment and transmits the force to the second top plate (6) through the shock-absorbing balls (8) to achieve the shock absorption effect. The equipment fixing bracket uses a bracket plate (9). The airborne GNSSB (10), laser locator (17), radar ranging sensor (18), orthophoto camera (20), data acquisition unit (22), power step-down device (21), stranded coil (12), traction rope (13), emergency brake switch (14), emergency brake switch trigger (15), small motor (14) and power unit remote control signal receiver (11) are fixed to a certain size and connected to the third top plate (7); all the above plates are made of high-strength and lightweight carbon fiber plates.

3. The high-precision water depth measurement method for a rotary-wing unmanned aerial vehicle according to claim 1, characterized in that: The airborne GNSS (10) records the position and attitude data of the UAV, including time, longitude, latitude, elevation, heading angle, pitch angle and roll angle, and is fixed directly above the laser locator 17; the laser locator 17 can form a clear light spot when it illuminates the water surface, and is fixed on the base plate 9-1, close to the orthophoto camera 20; the radar ranging sensor 18 can accurately measure the distance between the UAV and the water surface, and is fixed on the base plate 9-1; the orthophoto camera 20 is a correctly calibrated optical camera, and is fixed on the base plate 9-1; the data acquisition unit 22 supports the acquisition and storage of serial port data signals of 485 and 232.

4. The high-precision water depth measurement method for a rotary-wing UAV according to claim 1, characterized in that: The power supply step-down device 21 uses a transformer that can stably convert high-voltage DC power to 5-12V DC power; the stranded coil 12 is connected to the shaft of the small motor 19, made of carbon fiber material, with a U-shaped groove design, a groove length of 15mm, and inner and outer diameters of 20mm and 10mm respectively; one end of the traction rope 13 is fixed to the stranded coil 12, and the other end is fixed to the miniature sonar 16; the minimum traction force of the small motor 19 is not less than 10N, and it supports forward rotation, reverse rotation, and stop; the emergency brake switch 14 uses a miniature pressure switch, which immediately cuts off the power after being pressed, and is fixed to the base plate 9-1; the emergency brake switch trigger 15 uses a carbon fiber rod fixed to the end of the traction rope; the power unit remote control signal receiver 11 uses a 5-12V DC remote controller, with an effective control distance of not less than 100m; the power unit lifting and stopping control stick 23 is integrated into the UAV remote controller 26.

5. The high-precision water depth measurement method for a rotary-wing UAV according to claim 1, characterized in that: The miniature sonar 16 is circular in shape, with a diameter of no more than 100mm and a mass of no more than 500g. It has a minimum depth measurement distance of no less than 80m and can float on the water surface. It can store raw observation data, including time and water depth. It has a built-in rechargeable lithium battery and a WIFI transmitter, and can independently observe and wirelessly transmit observation data. It has a display 27 with WIFI receiving function, which can connect to the WIFI signal emitted by the miniature sonar 16.

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