Wetland surface elevation measuring instrument and method based on acoustics

Abstract

The invention discloses an acoustics-based wetland surface elevation measuring instrument and a measuring method, and relates to the field of wetland surface elevation change measuring methods. The measuring instrument mainly comprises a measuring cross arm, an auxiliary device base station and a base, the measuring cross arm comprises a horizontal arm fixed on the base through a connecting end and an underwater acoustic depth finder fixed on the horizontal arm, and the underwater acoustic depth finder measures the distance to the surface of the wetland by measuring sound wave reflection in water; and the change rate of the surface elevation of the wetland is obtained by measuring the distance difference of different time points. According to the invention, long-distance data acquisition and transmission of user-defined time can be realized through the communication control module, compared with a current determination method of artificial data acquisition, errors and cost caused by artificial determination are greatly reduced, higher precision and efficiency are achieved, and monitoring of elevation change of the surface of the wetland on a smaller time scale can be realized; the research range is expanded; and the device is simple in structure, and can stably operate for a long time under severe working conditions such as coastal wetlands and the like.

Description

Technical Field

[0001] The present invention relates to the field of wetland surface elevation change measurement methods, and in particular to an acoustic-based wetland surface elevation measurement instrument and measurement method. Background Art

[0002] The change of wetland surface elevation is one of the important indicators of ecosystem risk assessment. Especially in the intertidal zone of coastal wetlands, small changes in surface elevation (millimeter level) play a key role in assessing the sensitivity of coastal intertidal zones to future climate change, especially sea level rise. Among the current methods for in-situ measurement of wetland surface elevation changes, the surface elevation table-marker horizon (SET-MH or SET) is a method generally recognized at home and abroad (see patents with application numbers 201510046080.9 and 201520780019.2), but it requires huge manpower and material resources in the actual measurement process; and it requires surveyors to conduct visual measurements, which inevitably affects the accuracy of elevation measurements by human factors; the measurement frequency cannot be carried out frequently due to the limitation of manpower and material resources, which to a certain extent hinders its application in smaller time scale research. Although there are improved automated surface elevation measuring instruments available, their mechanical structures are complex, and they do not fully consider the durability of the devices under the harsh environments of coastal wetlands such as tides. The manufacturing, installation and subsequent maintenance costs are high, and they lack practicality, making them difficult to use widely. Summary of the invention

[0003] The purpose of the present invention is to solve the above problems in the prior art and to provide an acoustic-based wetland surface elevation measuring instrument and measurement method, which has the characteristics of automation, high precision, simple structure and long-term stable operation.

[0004] In order to achieve the above object, the present invention adopts the following technical scheme:

[0005] A wetland surface elevation measuring instrument based on acoustics, comprising: a base, a measuring cross arm and an auxiliary device base station; one end of the base is connected to the measuring cross arm, and the other end of the base is vertically anchored to the wetland geological layer; the measuring cross arm comprises a cross arm body and a hydroacoustic depth sounder, and the hydroacoustic depth sounder is arranged on the cross arm body; the auxiliary device base station comprises a fixed pipe and a warm and salt water level meter arranged on the fixed pipe, a communication control module and a power supply device; the fixed pipe is vertically fixed to the wetland geological layer, and the warm and salt water level meter comprises a probe for recording the water level, temperature and salinity of the water body, and the probe of the warm and salt water level meter is kept at the same horizontal line as the lower end of the hydroacoustic depth sounder; the communication control module is used for collecting and sending data, and the power supply device is used for powering the wetland surface elevation measuring instrument based on acoustics.

[0006] The number of the cross arm bodies is determined according to the measurement requirements, and the cross arm bodies are arranged in a circular array, and the horizontal angles between the cross arm bodies are the same.

[0007] The number of the hydroacoustic depth sounders is determined according to the measurement requirements. There are no less than three hydroacoustic depth sounders on each cross arm body, and the hydroacoustic depth sounders are fixed on the cross arm body at equal distances.

[0008] The number of hydroacoustic depth sounders on each cross arm body is 3 to 9.

[0009] The power supply device includes a solar panel for generating electricity and a battery for storing electricity.

[0010] The communication control module is connected to the warm and salt water level meter and the hydroacoustic depth sounder through anti-corrosion wires.

[0011] A method for measuring wetland surface elevation based on the acoustic wetland surface elevation measuring instrument comprises the following steps:

[0012] 1) Installation and positioning: Install the base in the measurement area, and the calibration cross arm body is in a horizontal state;

[0013] 2) Environmental parameter collection: The real-time water temperature T and salinity S are obtained through the warm and salt water level meter, and the current sound speed V in the water is obtained through the Del Grosso empirical calculation formula for the sound speed in water; the Del Grosso empirical calculation formula for the sound speed in water is: ; Where V is the speed of sound, T is the water temperature, S is the salinity, and D is the depth;

[0014] 3) Elevation measurement: The hydroacoustic depth sounder and the warm and salt water level meter work simultaneously to obtain the time t when the sound wave reaches the wetland surface and reflects back to the bottom of the hydroacoustic depth sounder; through the formula The height h from the bottom of the hydroacoustic depth sounder to the wetland surface is calculated;

[0015] 4) Calculation of change: For two measurements at time T 1 , T 2 The height data H measured by n hydroacoustic depth sounders 1 , H 2 ,…,H n and h 1 、h 2 ,…,h n , according to the formula Find the average value, the rate of change of surface elevation ;

[0016] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0017] The present invention is based on the hydroacoustic depth sounder, which realizes long-distance custom-defined time data collection and transmission through the communication control module in the auxiliary device base station. Compared with the current measurement method of manually collecting data, the error and cost caused by manual measurement are greatly reduced, and it has higher measurement accuracy and efficiency. It can also realize the monitoring of wetland surface elevation changes on a smaller time scale, and expand the scope of application research. In addition, the present invention has a simple structure and can realize long-term and stable operation under harsh working conditions such as coastal wetlands. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the overall structure of an acoustic-based wetland surface elevation measuring instrument described in Example 1;

[0019] Figure 2 This is a schematic diagram of the application of the method described in Example 1;

[0020] Figure 3 It is a schematic diagram of the overall structure of the double-determination cross-arm measuring instrument of the present invention.

[0021] Figure numerals: 1 base, 2 measuring cross arm, 3 auxiliary device base station; 11 reference tube, 12 stabilizing tube, 13 base connector; 21 cross arm connecting end, 22 leveling device, 23 spirit level, 24 hydroacoustic depth sounder, 25 cross arm body; 31 fixing tube, 32 warm and salt water level meter, 33 communication control module, 34 power supply device. DETAILED DESCRIPTION

[0022] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and more understandable, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0023] Example 1

[0024] See also Figures 1 to 3 , This embodiment is a wetland surface elevation measuring instrument based on acoustics, comprising: a base 1, a measuring cross arm 2 and an auxiliary device base station 3;

[0025] One end of the base 1 is connected to the measuring cross arm 2, and the other end of the base 1 is vertically anchored to the wetland geological layer; specifically, the base 1 includes a reference pipe 11 vertically anchored in the stable geological layer, a stabilizing pipe 12 arranged around the reference pipe 11, and a base connector 13 arranged on the top of the reference pipe 11; in this embodiment, the base 1 is anchored to the underground stable layer by the reference pipe 11 to ensure that the overall elevation of the base 1 does not change, thereby providing a stable reference for measurement; the stabilizing pipe 12 is arranged around the reference pipe 11, and is made of concrete and PVC pipe, and is mainly used to stabilize the reference pipe 11 in the wetland to avoid the influence of water dynamics such as waves;

[0026] The measuring cross arm 2 comprises a cross arm connecting end 21, a cross arm main body 25, a hydroacoustic depth sounder 24, a leveling device 22, and a spirit level 23; the measuring cross arm 2 is screwed and fixed to the base connecting member 13 of the base 1 through the cross arm connecting end 21; the leveling device 22 and the spirit level 23 ensure that the cross arm main body 25 is in a horizontal state when the installation is completed; the hydroacoustic depth sounder 24 is arranged on the cross arm main body 25, and the hydroacoustic depth sounder 24 measures the distance to the wetland surface by measuring the reflection of sound waves in the water; and the rate of change of the wetland surface elevation is obtained by measuring the difference in distance at different time points;

[0027] The number of the cross arm bodies 25 is determined according to the measurement requirements, and the cross arm bodies 25 are arranged in a circular array, and the horizontal angles between the cross arm bodies 25 are the same; for example, if two measurement cross arms 2 are set, the horizontal angle is 180 degrees; if four measurement cross arms 2 are set, the horizontal angle is 90 degrees, which is not limited to Figure 1 and Figure 3 1 or 2 measuring arms;

[0028] The number of the hydroacoustic depth sounders 24 is determined according to the measurement requirements. There are no less than 3 hydroacoustic depth sounders 24 on each cross arm body 25, and the hydroacoustic depth sounders 24 are equidistantly fixed on the cross arm body 25. Generally, the number of the hydroacoustic depth sounders 24 on each cross arm body 25 is 3 to 9, and in this embodiment, it is 6;

[0029] The auxiliary device base station 3 includes a fixed tube 31 and a warm and salt water level meter 32, a communication control module 33 and a power supply device 34 arranged on the fixed tube 31; the fixed tube 31 is vertically fixed to the wetland geological layer, and the warm and salt water level meter 32 includes a probe for recording the water level, temperature and salinity of the water body, and the probe of the warm and salt water level meter 32 is kept at the same horizontal line as the lower end of the hydroacoustic depth sounder 24; the communication control module 33 is used for collecting and sending data, specifically, it can accept remote commands and send relevant measurement data, and the communication control module 33 connects the warm and salt water level meter 32 and the hydroacoustic depth sounder 24 through anti-corrosion wires; the power supply device 34 is used to power the entire acoustic-based wetland surface elevation measuring instrument. The power supply device 34 in this embodiment includes a solar panel for generating electricity and a battery for storing electricity; the fixed tube 31 is made of 304 stainless steel.

[0030] A method for measuring wetland surface elevation based on the acoustic wetland surface elevation measuring instrument comprises the following steps:

[0031] 1) Installation and positioning: The acoustic wetland surface elevation measuring instrument of the present invention is installed in the measurement area, and after the installation is completed, the cross arm body is calibrated to ensure that it is in a horizontal state;

[0032] 2) Environmental parameter collection: First, the water level in the measurement area is determined to be higher than the lower end of the hydroacoustic depth sounder through the warm and salt water level meter, and then a measurement command is issued to obtain the real-time water temperature T and salinity S through the warm and salt water level meter, and the sound speed V in the current water is obtained through the Del Grosso empirical calculation formula for the sound speed in water; the Del Grosso empirical calculation formula for the sound speed in water is: ; Wherein, V is the speed of sound (m / s), T is the water temperature (degrees Celsius), S is the salinity (‰), and D is the depth (m). Since the application scenario of this embodiment belongs to a shallow water area, the depth D is not included in the speed of sound calculation;

[0033] 3) Elevation measurement: The hydroacoustic depth sounder and the warm and salt water level meter work simultaneously to obtain the time t when the sound wave reaches the wetland surface and reflects back to the bottom of the hydroacoustic depth sounder; the height h from the bottom of the hydroacoustic depth sounder to the wetland surface is calculated by the formula h / 2=V·t;

[0034] 4) Calculation of change: For two measurements at time T 1 , T 2 The height data H measured by the n hydroacoustic depth sounders 24 1 , H 2 ,…,H n and h 1 、h 2 ,…,h n , according to the formula Find the average value, the rate of change of surface elevation .

[0035] The specific steps for calculating the rate of change of surface elevation are as follows: the heights to the wetland surface measured by the six hydroacoustic depth sounders on the cross arm are H 1 ~H 6 After a period of time T, the six hydroacoustic depth sounders measured the heights of the wetland surface to be h and h respectively. 1 ~h 6 The difference between the two measurement results is the mean D, which is the change in surface elevation of the wetland in this area during the time period. The difference is divided by the time period T to obtain the surface elevation change rate S.

[0036] Specifically, Figure 2 As shown, when the test is completed, the water level in the measured area is confirmed to be higher than the lower end of the hydroacoustic depth sounder by remote water level meter data. On March 1, 2024 (T 1 ) issued a measurement command, started the measurement and obtained 6 heights from the ground surface (mm): 93 (H 1 ), 95 (H 2 ), 92 (H 3 ), 90 (H 4 ), 92 (H 5), 96 (H 6 ); on May 1, 2024 (T 2 ), repeat the above operation to obtain the height of the probe from the ground surface: 95 (h 1 ), 96 (h 2 ), 95 (h 3 ), 93 (h 4 ), 95 (h 5 ), 98 (h 6 ); calculated by the following formula:

[0037]

[0038]

[0039] Get the measurement area at T 1 To T 2 The rate of change of surface elevation during this period is 13.62 .

[0040] Compared with existing measurement technologies and instruments, the acoustic-based wetland surface elevation measuring instrument and measurement method provided by the present invention have the following advantages:

[0041] First, the use of a hydroacoustic depth sounder as a technical means to obtain surface elevation change data greatly improves the accuracy of the data compared to manual measurement; and based on the base, it provides a stable benchmark for the measurement, ensuring the credibility of the data and high repeatability; coupled with a communication control module, remote data collection is achieved, greatly improving measurement efficiency.

[0042] Secondly, the present invention has a simple structure and is easy to install and promote. Compared with other measuring instruments that rely on complex mechanical and electronic components and cannot work in intertidal zones that are repeatedly submerged by seawater, the present invention can achieve stable and long-term operation in harsh environmental conditions such as coastal wetlands, with low subsequent maintenance costs.

[0043] Finally, the present invention is applicable to the measurement of surface elevations of all wetlands that can be covered by water bodies and has a wide range of applications.

Claims

1. A wetland surface elevation measuring instrument based on acoustics, characterized in that: include: A base, a measuring cross arm and an auxiliary device base station; one end of the base is connected to the measuring cross arm, and the other end of the base is vertically anchored to the wetland geological layer; the measuring cross arm includes a cross arm body and a hydroacoustic depth sounder, and the hydroacoustic depth sounder is arranged on the cross arm body; the auxiliary device base station includes a fixed pipe and a warm and salt water level meter arranged on the fixed pipe, a communication control module and a power supply device; the fixed pipe is vertically fixed to the wetland geological layer, and the warm and salt water level meter includes a probe for recording the water level, temperature and salinity of the water body, and the probe of the warm and salt water level meter is kept at the same horizontal line with the lower end of the hydroacoustic depth sounder; the communication control module is used for collecting and sending data, and the power supply device is used for powering the acoustic-based wetland surface elevation measuring instrument.

2. The acoustic wetland surface elevation measuring instrument according to claim 1, characterized in that: The number of the cross arm bodies is determined according to the measurement requirements, and the cross arm bodies are arranged in a circular array, and the horizontal angles between the cross arm bodies are the same.

3. The acoustic wetland surface elevation measuring instrument according to claim 1, characterized in that: The number of the hydroacoustic depth sounders is determined according to the measurement requirements. There are no less than three hydroacoustic depth sounders on each cross arm body, and the hydroacoustic depth sounders are fixed on the cross arm body at equal distances.

4. The acoustic wetland surface elevation measuring instrument according to claim 3, characterized in that: The number of hydroacoustic depth sounders on each cross arm body is 3 to 9.

5. The acoustic wetland surface elevation measuring instrument according to claim 1, characterized in that: The power supply device includes a solar panel for generating electricity and a battery for storing electricity.

6. The acoustic wetland surface elevation measuring instrument according to claim 1, characterized in that: The communication control module is connected to the warm and salt water level meter and the hydroacoustic depth sounder through anti-corrosion wires.

7. A method for measuring wetland surface elevation using the acoustic wetland surface elevation measuring instrument according to any one of claims 1 to 6, characterized in that: The following steps are involved: 1) Installation and positioning: Install the base in the measurement area, and the calibration cross arm body is in a horizontal state; 2) Environmental parameter collection: The real-time water temperature T and salinity S are obtained through the temperature and salt water level meter, and the current sound speed V in the water is obtained through the Del Grosso empirical calculation formula for the sound speed in water; 3) Elevation measurement: The hydroacoustic depth sounder and the warm and salt water level meter work simultaneously to obtain the time t when the sound wave reaches the wetland surface and reflects back to the bottom of the hydroacoustic depth sounder; the height h from the bottom of the hydroacoustic depth sounder to the wetland surface is calculated by the formula h / 2=V·t.

8. The wetland surface elevation measurement method according to claim 7, characterized in that: The following steps are also included: 4) Calculation of variation: The height data H1, H2, ..., H measured by n hydroacoustic depth sounders at two measurement times T1 and T2 are calculated. n and h1, h2, …, h n , according to the formula D = (H1 - h1 + H2 - h2 + … + H n -h n ) / n to find the average, the rate of change of surface elevation S = D / (T2 - T1).

9. The wetland surface elevation measurement method according to claim 7, characterized in that: The Del Grosso empirical calculation formula for the speed of sound in water is: ; Where V is the speed of sound, T is the water temperature, S is the salinity, and D is the depth.

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