River section stratified sampling device, system and method based on water pressure control

Abstract

The invention discloses a riverway section stratified sampling device, system and method based on water pressure control, the device comprises a sampling container, the system comprises the device, the method utilizes the system to perform stratified sampling of a riverway water body, and the method comprises the following steps: measuring the width of a riverway; determining the number of vertical lines for sampling and the positions of the vertical lines according to the width; measuring the water depth of the river section; determining the number of sampling points needing to be arranged on the vertical line and the water depth of each sampling point according to the water depth of the cross section of the river channel; presetting an opening pressure range of the sampling container; the layered sampling device is released for descending sampling; during descending, a pressure sensing bottle cap of the sampling container is opened to automatically complete water body sampling; after sampling is completed, the stratified sampling device is pulled out of the water surface. The method can accurately identify the water depth of the cross section of the river channel, realizes stratified sampling to accurately reflect the real water quality condition of each water layer, and further provides more accurate and scientific data support for subsequent evaluation of the water pollution degree and source.

Description

Technical Field

[0001] The present invention belongs to the technical field of river section measurement, and in particular relates to a river section stratified sampling device, system and method based on water pressure control. Background Art

[0002] River water environment quality monitoring is a key link in environmental protection and water resources management. It can timely grasp the water quality status, assess the degree and source of pollution, and provide a scientific basis for water resources management, pollution prevention and control, and ecological restoration. Among them, achieving scientific sampling of river sections and ensuring the accuracy and representativeness of sampling data are the basis for water environment quality monitoring. The "Technical Specifications for Surface Water Environmental Quality Monitoring" (HJ91.2-2022) sets the number of sampling vertical lines set on the monitoring section and the setting of sampling points on each vertical line as shown in Table 1.

[0003] Table 1. Number of vertical lines for river sampling and setting of sampling points on vertical lines

[0004]

[0005] Taking the case where the width of a river is greater than 100 meters and the depth is greater than 10 meters as an example, the sampling vertical line and the sampling points on the vertical line are set as follows: Figure 1 As shown in the figure, the circle "°" indicates the location of the sampling point. Traditional sampling techniques mostly rely on the experience of operators rather than actual water depth data, which makes it difficult to achieve stratified sampling, low positioning accuracy, and limited sampling range. As a result, the samples lack representativeness and cannot accurately reflect the true water quality of each water layer, which in turn affects the scientific assessment of the degree and source of water pollution. Summary of the invention

[0006] In order to solve the above problems, the present invention provides a river section stratified sampling device, system and method based on water pressure control, which can accurately identify the water depth of the river section and realize stratified sampling to accurately reflect the actual water quality status of each water layer, thereby providing more accurate and scientific data support for the subsequent assessment of the degree and source of water pollution.

[0007] The technical solution adopted by the present invention is:

[0008] In the first aspect, the present application discloses a river section stratified sampling device based on water pressure control, comprising: an upper cover plate and a lower cover plate arranged in parallel up and down; at least three support columns, each of which has two ends connected to the upper cover plate and the lower cover plate respectively; at least three sampling containers, each of which is arranged between the upper cover plate and the lower cover plate; a traction rope connected to the upper cover plate; and a counterweight ball connected to the lower cover plate.

[0009] As an optional technical solution, the sampling container includes: a bottle body with a water level scale on it; a pressure sensing bottle cap that is adapted to the bottle body; a pressure sensor is provided in the pressure sensing bottle cap, and when the pressure detected by the pressure sensor is within a preset range, the water inlet of the pressure sensing bottle cap is opened, and when it is not within the preset range, the water inlet of the pressure sensing bottle cap is closed.

[0010] In the second aspect, the present application discloses a river section stratified sampling system based on water pressure control, comprising: a water depth identification device for identifying the water depth of the river; the water depth identification device includes a drone; a portable positioning device for providing location information for the drone; and a stratified sampling device as described in the first aspect above; the free end of the traction rope is connected to the drone.

[0011] As an optional technical solution, the water depth identification device further includes:

[0012] Lidar, which sends laser pulses to the water and receives signals reflected from the surface and river bottom;

[0013] A portable controller is connected to the laser radar for calculating the cross-sectional water depth data according to the reflected signal.

[0014] As an optional technical solution, the portable positioning device includes a GNSS receiver and an RTK device used in conjunction with each other.

[0015] In the third aspect, the present application discloses a stratified sampling method for a river section based on the above-mentioned system, including: measuring the width of the river, and determining the number and position of vertical lines for sampling based on the width; measuring the water depth of the river section; determining the number of sampling points that need to be set on the vertical line and the water depth h2 at each sampling point based on the water depth of the river section; presetting the opening pressure range of the sampling container: calculating the water pressure value at the sampling point, and presetting the opening pressure range of the sampling container based on the calculated water pressure value; releasing the stratified sampling device to descend for sampling: controlling the drone to fly above the water surface of the sampling point and gradually descending, and when the sampling container reaches the sampling point position, the pressure-sensing bottle cap of the sampling container opens to automatically complete the water sampling; ascending and recovering: after the sampling is completed, controlling the drone to ascend to pull the stratified sampling device out of the water.

[0016] As an optional technical solution, the measurement of the river channel width includes: using a laser radar to scan the river channel section in the horizontal direction to obtain a scanning angle range θ, and the river channel width d is calculated according to the following formula:

[0017]

[0018] Among them, the laser radar is carried on the drone, h1 is the vertical distance from the laser radar to the water surface, and θ is the horizontal scanning angle.

[0019] As an optional technical solution, the method of measuring the water depth of a river section includes: matching and connecting a GNSS receiver with an RTK device, and mounting the connected GNSS receiver on a drone; the GNSS receiver provides location information to the drone, and the drone flies to the measurement point according to the location information; after reaching the measurement point, the laser radar mounted on the drone emits laser pulses to the water surface, and receives echo signals reflected from the water surface and the river bottom; and the echo signal is used to calculate the water depth of the river section.

[0020] As an optional technical solution, the method of calculating the water depth of a river section by using the echo signal includes:

[0021] The filtering algorithm based on the threshold T separates the water surface and river bottom reflection signals. The threshold T is set to β times the maximum signal intensity of the echo signal, that is,

[0022] T=β×A max =β×max(E(t))

[0023] Among them, β ranges from 0.8 to 0.9, A max represents the maximum amplitude of the echo signal, E(t) represents the signal strength of the echo signal changing with time, and max(·) represents the maximum value;

[0024] Detect water surface reflection: Use the following formula (1) to find the time t of the first echo signal exceeding the threshold T: s :

[0025] t s =min{t|E(t)>T}…………(1);

[0026] Detect river bottom reflection: at t s Then, the second echo signal time t exceeding the threshold is found by the following formula (2): b :

[0027] t b =min{t>t s |E(t)>T}………(2);

[0028] According to the time delay of water surface and river bottom reflection, the water depth h of the river section is calculated:

[0029]

[0030] Where c is the speed of light and n is the refractive index of water.

[0031] As an optional technical solution, the preset opening pressure range of the sampling container includes:

[0032] First calculate the water pressure value P at the sampling point:

[0033] P = ρ × g × h2;

[0034] Among them, ρ is the river water density, g is the gravitational acceleration, and h2 is the water depth at the sampling point;

[0035] Set the opening pressure range of the sampling container to 0.95P≤P open ≤1.05P.

[0036] The beneficial effects of the present invention are as follows: the river section stratified sampling device, system and method based on water pressure control provided by the present invention can accurately identify the water depth and water surface width of the river section, so as to accurately determine the number and location of the sampling points. The stratified sampling system uses pressure sensors to intelligently control the opening and closing of the sampling container, ensuring that each container only collects water samples at a predetermined depth, effectively avoiding the mixing of water samples at different levels, and ensuring the representativeness of the samples and the accuracy of the data. By integrating the functions of water depth identification, positioning and stratified sampling, the present application realizes the automation of the entire process from measurement to sampling, simplifies the operation process, and reduces the difficulty and cost of operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a schematic diagram of the stratified sampling points in the river section.

[0038] Figure 2 It is a schematic diagram of the structure of a river section stratified sampling device based on water pressure control.

[0039] Figure 3 It is a circuit block diagram of the electronic components in the pressure sensing bottle cap.

[0040] Figure 4 It is the internal structural layout of the pressure-sensing bottle cap.

[0041] Figure 5 This is the system architecture diagram of the river section stratified sampling system based on water pressure control.

[0042] Figure 6 It is a schematic diagram of the flow of the river section stratified sampling method based on water pressure control.

[0043] Figure 7 is the reflection signal curve.

[0044] Figure 8 This is a comparison curve of the root mean square error between the drone-mounted laser radar water depth measurement method of this embodiment and the traditional measurement method.

[0045] Fig. 9This is a relative error comparison curve between the drone-mounted laser radar water depth measurement method of this embodiment and the traditional measurement method. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. The components and method steps of the embodiments of the present invention generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0047] Example

[0048] like Figure 2 As shown, this embodiment discloses a river section stratified sampling device based on water pressure control, including: an upper cover plate 1 and a lower cover plate 2 arranged in parallel up and down; at least three support columns 3, each of the two ends of the support column 3 is respectively connected to the upper cover plate 1 and the lower cover plate 2, and the upper cover plate 1 and the lower cover plate 2 are both circular, and all the support columns 3 are evenly distributed along the edges of the upper cover plate 1 and the lower cover plate 2; at least three sampling containers 4, each of the sampling containers 4 is arranged between the upper cover plate 1 and the lower cover plate 2, and all the sampling containers 4 are evenly distributed between the upper cover plate 1 and the lower cover plate 2; a traction rope 5, connected to the upper cover plate 1; a counterweight ball 6, connected to the lower cover plate 2, and the counterweight ball 6 can make the entire sampling system sink quickly to the required depth, ensuring that the sampling process is rapid and accurate. Figure 2 As shown, in this embodiment, six support columns 3 are provided and six sampling containers 4 are provided.

[0049] As an optional embodiment, the sampling container 4 includes: a bottle body 401, which is provided with a water level scale; a pressure sensing bottle cap 402, which is adapted to the bottle body 401; a pressure sensor 403 is provided in the pressure sensing bottle cap 402, when the pressure detected by the pressure sensor 403 is within a preset range, the water inlet of the pressure sensing bottle cap 402 is opened, and when it is not within the preset range, the water inlet of the pressure sensing bottle cap 402 is closed.

[0050] Specifically, the pressure sensor 403 is a strain gauge pressure sensor, and the pressure sensing bottle cap 402 is also provided with a microcontroller MCU, a battery and a power amplifier, and a solenoid valve is provided at the water inlet of the pressure sensing bottle cap 402, wherein the microcontroller MCU, the battery and the power amplifier are sealed in the pressure sensing bottle cap 402 through a waterproof sealing ring. The circuit block diagram of each electronic component in the pressure sensing bottle cap 402 is shown in FIG. Figure 3 As shown, the strain gauge pressure sensor 403 is used to monitor the surrounding water pressure in real time to ensure that the solenoid valve 404 is triggered to operate when a predetermined depth is reached; the solenoid valve 404 controls the opening and closing of the valve by turning the electromagnetic coil on and off; the microcontroller 405 is responsible for receiving the signal from the strain gauge pressure sensor 403 and controlling the operation of the solenoid valve 404 according to a preset pressure threshold; the battery 406 supplies power to the entire system to ensure that it can work independently in an underwater environment; the power amplifier 407 is used to drive the solenoid valve 404 and provide sufficient current to ensure that the solenoid valve 404 works reliably.

[0051] Furthermore, the internal structure layout of the pressure sensing bottle cap 402 is as follows: Figure 4 As shown, it includes a cover body 408, a sampling water inlet 409 penetrating the cover body 408 is provided in the cover body 408, and a solenoid valve 404 is provided on the sampling water inlet 409 to control the opening and closing of the sampling water inlet 409; a pressure sensor water inlet 410 is also provided in the cover body 408, a strain gauge pressure sensor 403 is provided at the bottom of the pressure sensor water inlet 410, and the strain gauge pressure sensor 403 is connected to the microcontroller MCU 405 through a cable 411; one end of the power amplifier 407 is connected to the microcontroller MCU 405 through the cable 411, and the other end is connected to the solenoid valve 404; the microcontroller MCU 405 and the battery 406 are both sealed in the cover body 408.

[0052] In this embodiment, water samples of a specific depth are collected through the sampling container 4. Each sampling container 4 is equipped with a pressure-sensing bottle cap 402, and the opening and closing of the pressure-sensing bottle cap water inlet solenoid valve 404 is controlled by a strain gauge pressure sensor 403. When the sampling container 4 drops to a predetermined depth, the strain gauge pressure sensor 403 senses the corresponding pressure, and the microcontroller MCU 405 sends an opening signal to the power amplifier 407, and the power amplifier 407 drives the solenoid valve 404 to open and start collecting water samples; when the sampling container 4 rises and leaves the depth area or reaches the next set depth, the water pressure change triggers the strain gauge pressure sensor 403 again, and the valve closes to seal the sample. This mechanism ensures that each container only collects water samples within a specific depth range, avoiding the mixing of water samples at different depths.

[0053] like Figure 5As shown, this embodiment also discloses a river section stratified sampling system based on water pressure control, including: a water depth identification device for identifying the water depth of the river; the water depth identification device includes a drone 7; a portable positioning device for providing location information for the drone 7; and a stratified sampling device as described in the above embodiment; the free end of the traction rope 5 is connected to the drone 7.

[0054] As an optional embodiment, the water depth identification device also includes: a laser radar 8, which is used to emit laser pulses to the water surface and receive signals reflected from the water surface and the river bottom; a portable controller 9, which is communicated with the laser radar 8 and is used to calculate the cross-sectional water depth data based on the reflected signals.

[0055] As an optional embodiment, the portable positioning device includes a GNSS receiver 10 and an RTK device 11 used in conjunction, providing high-precision location information for the drone 7, ensuring that it can fly along a predetermined path and accurately reach the air above the water surface of each sampling point. The GNSS receiver 10 and the RTK device 11 are used in conjunction to achieve centimeter-level positioning accuracy.

[0056] like Figure 6 As shown, this embodiment also discloses a river section stratified sampling method based on the above system embodiment, comprising the following steps:

[0057] S1. Measure the width of the river channel, and determine the number and position of vertical lines for sampling based on the width.

[0058] Specifically, the width of the river channel is measured in the following manner: the drone hovers on one side of the river channel, and the laser radar 8 is used to scan the river channel to obtain the scanning angle range θ. The width of the river channel d is calculated according to the following formula:

[0059]

[0060] The laser radar 8 is mounted on the drone 7, h1 is the vertical distance from the laser radar 8 to the water surface, and θ is the horizontal scanning angle.

[0061] After the river width d is obtained, the number and position of the vertical lines are determined according to the Technical Specifications for Surface Water Environmental Quality Monitoring (HJ91.2-2022). Specifically, the river width d obtained is the water surface width b in Table 1.

[0062] S2. Measure the water depth of the river section.

[0063] Specifically, during measurement, the GNSS receiver 10 (GNSS, i.e., Global Navigation Satellite System) is first matched and connected with the RTK device 11 (RTK, i.e., Real time kinematic, carrier phase differential technology), and the connected GNSS receiver 10 is mounted on the drone 7; the GNSS receiver 10 provides location information for the drone 7, and the drone 7 flies to the measurement point according to the location information. During actual measurement, 7 or more water depth measurement points can be set on the river section. Taking the setting of 7 water depth measurement points as an example, the positions of the measurement points are respectively at d / 8, 2d / 8, 3d / 8, 4d / 8, 5d / 8, 6d / 8, and 7d / 8 of the river width (e.g., Figure 1 ); after reaching the measuring point, the laser radar 8 mounted on the drone 7 emits laser pulses to the water surface and receives echo signals reflected from the water surface and the river bottom; the echo signals reflected from each measuring point are used to calculate the water depth at each measuring point, and then the entire river section is obtained.

[0064] The laser radar echo signal model can be expressed as:

[0065] E(t)=A s ·δ(tt s )+A b ·δ(tt b )+N(t)

[0066] Where: A s is the amplitude of the water surface reflection signal, t s is the time delay of the signal reflected from the water surface, A b is the amplitude of the river bottom reflection signal, t b is the time delay of the river bottom reflection signal, N(t) is the noise or background signal, δ(tt s ) represents the instantaneous peak value of the water surface reflection signal at time ts, δ(tt b ) represents the instantaneous peak value of the river bottom reflection signal at time ts. Find t s With t b The difference between the two can be used to calculate the water depth of the river section.

[0067] Furthermore, the calculation of the water depth of the river section using the echo signal includes:

[0068] The filtering algorithm based on threshold T separates the water surface and river bottom reflection signals. The threshold T is set to β times the maximum signal intensity of the echo signal, that is:

[0069] T=β×A max =β×max(E(t))

[0070] Among them, β ranges from 0.8 to 0.9, A max represents the maximum amplitude of the echo signal, E(t) represents the signal strength of the echo signal changing with time, and max(·) represents the maximum value.

[0071] Detect water surface reflection: Use the following formula (1) to find the time t of the first echo signal exceeding the threshold T: s :

[0072] t s =min{t|E(t)>T}......(1);

[0073] Detect river bottom reflection: at t s Then, the second echo signal time t exceeding the threshold is found by the following formula (2): b :

[0074] t b =min{t>t s |E(t)>T}………(2);

[0075] According to the time delay of water surface and river bottom reflection, the water depth h of the river section is calculated:

[0076]

[0077] Where c is the speed of light and n is the refractive index of water.

[0078] S3. According to the water depth h of the river section, determine the number of sampling points that need to be set on the vertical line and the water depth h2 at each sampling point.

[0079] Specifically, after obtaining the water depth h of the river section, the number of sampling points on each vertical line and the water depth h2 at each sampling point are determined according to the "Technical Specifications for Surface Water Environmental Quality Monitoring" (HJ91.2-2022).

[0080] S4. Presetting the opening pressure range of the sampling container 4: calculating the water pressure value at the sampling point, and presetting the opening pressure range of the sampling container 4 according to the calculated water pressure value.

[0081] Specifically, first calculate the water pressure value P at the sampling point:

[0082] P = ρ × g × h2;

[0083] Among them, ρ is the river water density, g is the gravitational acceleration, and h2 is the water depth at the sampling point.

[0084] Set the opening pressure range of the sampling container to 0.95P≤P open ≤1.05P.

[0085] When P is obtained openAfter the initialization is completed in the ground preparation stage, the opening pressure P of the sampling container 4 is set to open The thresholds of 0.95P and 1.05P are programmed into the microcontroller MCU.

[0086] S5, release the stratified sampling device to descend sampling: control the drone 7 to fly above the water surface of the sampling point and gradually descend. When the sampling container 4 reaches the sampling point, the pressure sensing bottle cap of the sampling container 4 opens to automatically complete the water sampling. During the sampling process, the working process of the sampling container 4 is as follows:

[0087] ①: Real-time monitoring.

[0088] When the sampling container 4 begins to descend, the strain gauge pressure sensor 403 continuously monitors the surrounding water pressure P(t), and converts the analog signal into a digital signal through the digital converter of the strain gauge pressure sensor and transmits it to the microcontroller MCU405.

[0089] ②: Enable conditional judgment.

[0090] The microcontroller MCU 405 compares the current water pressure P(t) with the preset opening pressure P in real time. open , if P(t) is located in P open Within the range of 0.95P≤P(t)≤1.05P, the MCU sends an opening signal. The opening signal is transmitted to the electromagnetic valve 404 through the power amplifier 407, so that the electromagnetic valve 404 opens the water inlet and starts to collect water samples.

[0091] ③: Close condition judgment.

[0092] When the sampling container 4 rises or continues to fall, the microcontroller MCU 405 continues to monitor the water pressure P(t) and compares it with the preset threshold value 0.95P or 1.05P. If P(t) < 0.95P or P(t) > 1.05P, the microcontroller MCU 405 sends a closing signal. The closing signal is transmitted to the solenoid valve 404 through the power amplifier 407, so that the solenoid valve 404 closes the water inlet and seals the sample.

[0093] S6. Ascent and recovery: After completing the sampling, control the drone to ascend and pull the stratified sampling device out of the water.

[0094] For example, for Figure 1 When sampling at the three sampling points on the middle line of The water depth and the depth of the three sampling points in the lower layer are h 21 、h 22 、h 23 , in order to obtain the opening pressure ranges of the three sampling points:

[0095] 0.95P1≤P open1 ≤1.05P1

[0096] 0.95P2≤P open1 ≤1.05P2

[0097] 0.95P3≤P open1 ≤1.05P3

[0098] Where P1 = ρ × g × h 21 , P2=ρ×g×h 22 , P3=ρ×g×h 23 Then, the opening pressures of the three sampling containers were preset. The thresholds of the opening pressure of the first sampling container were set to 0.95P1 and 1.05P1, the thresholds of the opening pressure of the second sampling container were set to 0.95P2 and 1.05P2, and the thresholds of the opening pressure of the third sampling container were set to 0.95P3 and 1.05P3. During the sampling process, the stratified sampling device moved slowly along the central line. When it was at 0.95h 21 To 1.05h 21 When the depth is 0.95h, the solenoid valve of the first sampling container opens to sample the upper sampling point. When it is at other depths, the solenoid valve of the first sampling container is closed. 22 To 1.05h 22 When the water depth is 0.95h, the solenoid valve of the second sampling container opens to sample the sampling point at half the water depth. When the water depth is 0.95h, the solenoid valve of the second sampling container closes. 23 To 1.05h 23 When the depth is 100°, the solenoid valve of the third sampling container opens to sample the lower sampling point. When it is at other depths, the solenoid valve of the third sampling container is closed. In this way, the sampling of the three sampling points on the Zhonghong line can be completed at one time, and the water samples collected at each sampling point will not be mixed, achieving high sampling efficiency and accurate stratified sampling of the sampled water body.

[0099] For ease of understanding, an example of calculating the water depth of a river section using the method of this embodiment is listed below.

[0100] Table 2 is a list of signals reflected back from laser pulses emitted by the laser radar. Figure 7 is the reflection signal curve. Figure 7 It can be seen that there are two obvious peaks. The first peak appears at t = 10μs and the second peak appears at t = 30μs. The former corresponds to the water surface reflection and the latter corresponds to the river bottom reflection.

[0101] Table 2. Laser pulse reflection signal

[0102]

[0103]

[0104] (1) Calculate the maximum value:

[0105] Calculate the maximum value of the echo signal strength A max :

[0106] A max =max(E(t))=20.0

[0107] (2) Setting the threshold:

[0108] Set the threshold T to the maximum value A max 80%:

[0109] T=0.8·A max =0.8·20.0=16.0

[0110] (3) Detecting water surface reflection:

[0111] Find the first echo signal time t that exceeds the threshold T s :

[0112] t s =min{t|E(t)>16.0}=10μs

[0113] (4) Detect river bottom reflection:

[0114] In t s After that, find the second echo signal time t that exceeds the threshold T b :

[0115] t b =min{t>t s |E(t)>16.0}=30μs

[0116] (5) Calculate water depth:

[0117]

[0118] The method of this embodiment is used to measure the water depth of the river section with high measurement accuracy, which is conducive to the accurate collection of water bodies. The following compares the accuracy of the water depth measurement method using the laser radar technology carried by the drone of this embodiment with that of the traditional measurement method.

[0119] The root mean square error (RMSE) and relative error are selected to compare the measurement errors of the UAV-mounted laser radar technology of this embodiment and the traditional method. Figure 8 and Fig. 9They are the root mean square error RMSE and relative error change curves of the drone-mounted laser radar technology in this embodiment and the traditional measurement method. Figure 8 It can be seen that the RMSE of the UAV-mounted laser radar in this embodiment remains at a low level in all water depth ranges, especially in shallow waters (2-4 meters). The accuracy of the ship-borne depth sounder is relatively poor, especially in shallow waters, which is greatly affected by the speed of the ship and the water flow, resulting in high RMSE and relative error. The accuracy of sonar depth sounding is good in deep waters (>5 meters), but poor in shallow waters (<5 meters), so it is not suitable for high-precision measurement in shallow waters.

[0120] In summary, the drone equipped with laser radar in this embodiment has significant advantages in measurement accuracy, flexibility and efficiency, and can provide more reliable and accurate water depth measurement results.

[0121] The above description is only a specific implementation mode of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. All technical solutions that fall within the scope defined by the claims of the present invention fall within the protection scope of the present invention.

Claims

1. A river section stratified sampling device based on water pressure control, characterized in that: include: An upper cover plate and a lower cover plate arranged in parallel up and down; At least three support columns, both ends of each support column are connected to the upper cover plate and the lower cover plate respectively; At least three sampling containers, each of which is disposed between the upper cover plate and the lower cover plate; A traction rope connected to the upper cover plate; A counterweight ball is connected to the lower cover plate.

2. The river section stratified sampling device based on water pressure control according to claim 1 is characterized in that: The sampling container comprises: A bottle body, on which a water level scale is provided; A pressure-sensing bottle cap is adapted to the bottle body; a pressure sensor is arranged inside the pressure-sensing bottle cap, and when the pressure detected by the pressure sensor is within a preset range, the water inlet of the pressure-sensing bottle cap is opened, and when the pressure is not within the preset range, the water inlet of the pressure-sensing bottle cap is closed.

3. The river section stratified sampling system based on water pressure control is characterized by: include: A water depth identification device, used to identify the water depth of a river; the water depth identification device includes a drone; A portable positioning device, used to provide position information for the drone; And, the stratified sampling device as described in any one of claims 1 or 2; the free end of the traction rope is connected to the drone.

4. The river section stratified sampling system based on water pressure control according to claim 3 is characterized in that: The water depth identification device also includes: Lidar, which sends laser pulses to the water and receives signals reflected from the surface and river bottom; A portable controller is connected to the laser radar for calculating the cross-sectional water depth data according to the reflected signal.

5. The river section stratified sampling system based on water pressure control according to claim 3 is characterized in that: The portable positioning device includes a GNSS receiver and an RTK device used in conjunction with each other.

6. A river section stratified sampling method based on the system according to any one of claims 3 to 5, characterized in that: include: Measuring the width of the river channel, and determining the number and position of vertical lines for sampling based on the width; Measure the water depth of river sections; According to the water depth of the river section, determine the number of sampling points that need to be set on the vertical line and the water depth h2 at each sampling point; Presetting the opening pressure range of the sampling container: calculating the water pressure value at the sampling point, and presetting the opening pressure range of the sampling container according to the calculated water pressure value; Release the stratified sampling device to descend for sampling: control the drone to fly above the water surface at the sampling point and gradually descend. When the sampling container reaches the sampling point, the pressure-sensing bottle cap of the sampling container opens to automatically complete water sampling; Ascent and recovery: After completing the sampling, control the drone to ascend and pull the stratified sampling device out of the water.

7. The river section stratified sampling method according to claim 6, characterized in that: The measurement of the river channel width includes: using a laser radar to scan the river channel section in the horizontal direction to obtain a scanning angle range θ, and the river channel width d is calculated according to the following formula: Among them, the laser radar is carried on the drone, h1 is the vertical distance from the laser radar to the water surface, and θ is the horizontal scanning angle.

8. The river section stratified sampling method according to claim 6, characterized in that: The measurement of the water depth of the river section includes: Match and connect the GNSS receiver with the RTK device, and then mount the connected GNSS receiver on the drone; The GNSS receiver provides the drone with location information, and the drone flies to the measurement point based on the location information; After reaching the measurement point, the laser radar mounted on the drone emits laser pulses to the water surface and receives echo signals reflected from the water surface and the river bottom; The echo signal is used to calculate the water depth of the river section.

9. The river section stratified sampling method according to claim 8, characterized in that: The calculating of the water depth of the river section by using the echo signal comprises: The filtering algorithm based on the threshold T separates the water surface and river bottom reflection signals. The threshold T is set to β times the maximum signal intensity of the echo signal, that is, T=β×A max =β×max(E(t)) Among them, β ranges from 0.8 to 0.9, A max represents the maximum amplitude of the echo signal, E(t) represents the signal strength of the echo signal changing with time, and max(·) represents the maximum value; Detect water surface reflection: Use the following formula (1) to find the time t of the first echo signal exceeding the threshold T: s : t s =min{t|E(t)>T}………(1); Detect river bottom reflection: at t s Then, the second echo signal time t exceeding the threshold is found by the following formula (2): b : t b =min{t>t s |E(t)>T}………(2); According to the time delay of water surface and river bottom reflection, the water depth h of the river section is calculated: Where c is the speed of light and n is the refractive index of water.

10. The river section stratified sampling method according to claim 8, characterized in that: The opening pressure range of the preset sampling container includes: First calculate the water pressure value P at the sampling point: P = ρ × g × h2; Among them, ρ is the river water density, g is the gravitational acceleration, and h2 is the water depth at the sampling point; Set the opening pressure range of the sampling container to 0.95P≤P open ≤1.05P.

Images