Lake water level determination method, device, storage medium and electronic device

Abstract

The present invention discloses a method, device, storage medium, and electronic device for determining lake water levels. The method comprises: obtaining satellite radar altimetry data within a target lake; wherein the satellite radar altimetry data comprises echoes and geophysical data for at least one observation period; screening the echo data and normalizing the screened echo data to obtain the echo energy corresponding to each echo sampling point; determining the position of the optimal sub-wave according to the echo data and preset rules, and determining the position of a re-tracking point on the rising edge of the optimal sub-wave; wherein the re-tracking point is used to indicate the initial contact point between the ranging pulse signal and the target lake within the current observation period; and determining the water level value of the target lake corresponding to the current echo according to the re-tracking point. The present invention solves the technical problem of large errors or poor robustness in the process of determining lake water levels using radar altimetry data.

Description

Technical Field

[0001] The present invention relates to the technical field of remote sensing information processing, and in particular to a method, device, storage medium and electronic equipment for determining lake water level. Background Art

[0002] Lakes are a vital component of the terrestrial surface water cycle, playing a crucial role in regional agricultural irrigation, domestic and industrial water use, and the exchange of matter and energy. Lake level is one of the most important parameters reflecting lake changes and a key indicator in lake matter and energy exchange models. In recent years, due to the increasing impacts of climate change and human activities, lakes in some regions of the world, such as the Aral Sea and the Great Salt Lake, have undergone dramatic changes. Therefore, studying lake level changes is crucial for understanding the scope of climate change impacts and response mechanisms.

[0003] Since the 1990s, satellite altimetry technology has rapidly developed, bringing new opportunities for monitoring large-scale lake dynamics. Satellite altimeters enable long-term, large-scale monitoring of surface elevation, including oceans, sea ice, lakes, and rivers. Commonly used altimetry satellites include the ERS series of satellites (including ERS-1, ERS-2, Envisat, and SARAL) with a 35-day revisit period, the T / P series of satellites (including T / P, Jason-1 / 2 / 3) with a 10-day revisit period, and more recently developed satellites such as Cryosat-2, Sentinel-3A, and Sentinel-3B. Altimetry satellites typically utilize radar altimeters onboard their platforms for Earth observation. Satellite radar altimeters typically use the time difference between transmitted and received pulses to determine the satellite's distance from the ground, thereby inverting ground elevation. The key to accurate lake level tracking is to locate the point in the echo where the pulse contacts the lake surface (the retracking point). To obtain this retracking point, waveform retracking of the radar echo is required. The waveform re-tracking algorithms in related technologies are usually physical or empirical models designed for the ocean or sea ice, which are not applicable to lakes. In addition, another type of waveform re-tracking algorithm uses complex spatiotemporal dynamic models, which is not only time-consuming but also not very robust. Summary of the Invention

[0004] Embodiments of the present invention provide a lake water level determination method, device, storage medium, and electronic device to at least solve the technical problem of large error or poor robustness in the process of determining lake water level using radar altimetry data.

[0005] According to one aspect of an embodiment of the present invention, a method for determining lake water level is provided, which may also be referred to as an MSIE method, the method comprising: obtaining satellite radar altimetry data within a target lake; wherein the satellite radar altimetry data comprises echo data and geophysical data of at least one observation period; filtering the echo data and normalizing the filtered echo data to obtain echo energy corresponding to each echo sampling point; determining the position of an optimal sub-wave according to the echo data and preset rules, and determining the position of a re-tracking point on the rising edge of the optimal sub-wave; wherein the re-tracking point is used to indicate the initial contact point between the ranging pulse signal and the target lake in the current observation period; and determining the water level value of the target lake corresponding to the current echo according to the re-tracking point.

[0006] According to another aspect of an embodiment of the present invention, a lake water level determination device is also provided, including: an acquisition unit for acquiring satellite radar altimetry data within a target lake; wherein the satellite radar altimetry data is echo data and geophysical data containing at least one observation period; a standardization unit for filtering the echo data and standardizing the filtered echo data to obtain the echo energy corresponding to each echo sampling point; a first determination unit for determining the position of the optimal sub-wave according to the echo data and preset rules, and determining the position of the re-tracking point on the rising edge of the optimal sub-wave; wherein the re-tracking point is used to indicate the initial contact point between the ranging pulse signal in the current observation period and the target lake; a second determination unit for determining the water level value of the target lake corresponding to the current echo according to the re-tracking point.

[0007] According to another aspect of an embodiment of the present invention, an electronic device is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor is configured to execute the above-mentioned lake water level determination method through the computer program.

[0008] According to another aspect of an embodiment of the present invention, a computer-readable storage medium is provided, in which a computer program is stored, wherein the computer program is configured to execute the above-mentioned lake water level determination method when running.

[0009] In an embodiment of the present invention, a method is adopted for obtaining satellite radar altimetry data within a target lake; wherein the satellite radar altimetry data is echo data and geophysical data including at least one observation period; the echo data is screened and the screened echo data is standardized to obtain the echo energy corresponding to each echo sampling point; the position of the optimal sub-wave is determined according to the echo data and preset rules, and the position of the re-tracking point is determined on the rising edge of the optimal sub-wave; wherein the re-tracking point is used to indicate the initial contact point between the ranging pulse signal and the target lake in the current observation period; a method is provided for determining the water level value of the target lake corresponding to the current echo according to the re-tracking point. In the above method, since the echo data is standardized and the re-tracking point is determined, the lake surface echo with concentrated reflected energy can be better screened out, and the lake surface echo can be correctly selected from two consecutive rising edges of the frozen lake, which can effectively reduce the water level extraction error, thereby solving the technical problem of large error or poor robustness in the process of determining the lake water level by radar altimetry data. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0011] Figure 1 is a schematic diagram of an application environment of an optional lake water level determination method according to an embodiment of the present invention;

[0012] Figure 2 is a schematic diagram of an application environment of another optional lake water level determination method according to an embodiment of the present invention;

[0013] Figure 3 is a schematic diagram of an optional process for determining lake water level according to an embodiment of the present invention;

[0014] Figure 4 is an optional schematic diagram of radar footprint pollution along the track lake surface according to an embodiment of the present invention;

[0015] Figure 5 is a schematic diagram of lake surface echo formation according to an embodiment of the present invention;

[0016] Figure 6 is an optional schematic diagram of lake surface echo display according to an embodiment of the present invention;

[0017] Figure 7 is another optional schematic diagram of lake surface echo display according to an embodiment of the present invention;

[0018] Figure 8is a schematic diagram of another process for determining lake water level according to an embodiment of the present invention;

[0019] Figure 9 2. It is a schematic diagram comparing the water level extraction results of the MSIE method and the ICE-1 method on Big Bear Lake according to an embodiment of the present invention;

[0020] Figure 10 is a schematic structural diagram of an optional lake water level determination device according to an embodiment of the present invention;

[0021] Figure 11 FIG. 4 is a schematic structural diagram of an optional electronic device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the solutions of the present invention, 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 embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0023] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0024] According to one aspect of an embodiment of the present invention, a method for determining lake water level is provided. Optionally, as an optional implementation, the above-mentioned method for determining lake water level can be applied to, but is not limited to, Figure 1The application environment shown in FIG. This application environment includes a terminal device 102 for user interaction, a network 104, and a server 106. User 108 can interact with terminal device 102, which runs a lake water level determination application. Terminal device 102 includes a human-computer interaction screen 1022, a processor 1024, and a memory 1026. Human-computer interaction screen 1022 is used to display satellite radar altimetry data; processor 1024 is used to acquire satellite radar altimetry data. Memory 1026 is used to store this satellite radar altimetry data.

[0025] In addition, the server 106 includes a database 1062 and a processing engine 1064. The database 1062 is used to store the satellite radar altimetry data. The processing engine 1064 is used to obtain the satellite radar altimetry data within the target lake; wherein the satellite radar altimetry data includes echo data and geophysical data for at least one observation cycle; filter the echo data and normalize the filtered echo data to obtain the echo energy corresponding to each echo sampling point; determine the position of the optimal sub-wave based on the echo data and preset rules, and determine the position of the re-tracking point on the rising edge of the optimal sub-wave; wherein the re-tracking point is used to indicate the initial contact point between the ranging pulse signal and the target lake in the current observation cycle; and determine the water level value of the target lake corresponding to the current echo based on the re-tracking point.

[0026] In one or more embodiments, the lake water level determination method of the present application can be applied to Figure 2 In the application environment shown. Figure 2 As shown, human-computer interaction can be performed between user 202 and user device 204. User device 204 includes memory 206 and processor 208. In this embodiment, user device 204 can, but is not limited to, refer to and perform the operations performed by terminal device 102 to obtain the water level value of the target lake during the current observation period.

[0027] Optionally, the terminal device 102 and user device 204 include, but are not limited to, mobile phones, tablet computers, laptop computers, PCs, in-vehicle electronic devices, wearable devices, and the like. The network 104 may include, but is not limited to, a wireless network or a wired network. Wireless networks include Wi-Fi and other networks that enable wireless communication. Wired networks may include, but are not limited to, wide area networks, metropolitan area networks, and local area networks. The server 106 may include, but is not limited to, any hardware device capable of computing. The server may be a single server, a server cluster consisting of multiple servers, or a cloud server. The above is merely an example and is not intended to be limiting in this embodiment.

[0028] Existing lake water level extraction methods are mostly designed for the ocean or sea ice, and lakes are often smaller in area. Therefore, the echo shape of the large-footprint radar altimeter on the lake surface is not as regular as the ocean or sea ice echo, so this type of method does not perform well on the lake surface. Although there are some water level extraction methods designed specifically for inland water bodies, these methods have complex models and poor robustness. To address the above problems, the embodiments of the present invention design a practical and robust waveform re-tracking method based on the characteristics of lake surface echoes, which can achieve high-precision lake surface water level inversion.

[0029] As an optional implementation, Figure 3 As shown, an embodiment of the present invention provides a method for determining lake water level, comprising the following steps:

[0030] S302, obtaining satellite radar altimetry data within the target lake; wherein the satellite radar altimetry data includes echo data and geophysical data of at least one observation period;

[0031] S304, filtering the echo data and normalizing the filtered echo data to obtain the echo energy corresponding to each echo sampling point;

[0032] S306, determining the position of the optimal wavelet based on the echo data and a preset rule, and determining the position of a re-tracking point on the rising edge of the optimal wavelet; wherein the re-tracking point is used to indicate the initial contact point between the ranging pulse signal and the target lake in the current observation period;

[0033] S308: Determine the water level value of the target lake corresponding to the current echo according to the re-tracking point.

[0034] In an embodiment of the present invention, a method is adopted for obtaining satellite radar altimetry data within a target lake; wherein the satellite radar altimetry data is echo data and geophysical data including at least one observation period; the echo data is screened and the screened echo data is standardized to obtain the echo energy corresponding to each echo sampling point; the position of the optimal sub-wave is determined according to the echo data and preset rules, and the position of the re-tracking point is determined on the rising edge of the optimal sub-wave; wherein the re-tracking point is used to indicate the initial contact point between the ranging pulse signal and the target lake in the current observation period; a method is provided for determining the water level value of the target lake corresponding to the current echo according to the re-tracking point. In the above method, since the echo data is standardized and the re-tracking point is determined, the lake surface echo with concentrated reflected energy can be better screened out, and the lake surface echo can be correctly selected from two consecutive rising edges of the frozen lake, which can effectively reduce the water level extraction error, thereby solving the technical problem of large error or poor robustness in the process of determining the lake water level by radar altimetry data.

[0035] In one or more embodiments, normalizing the echo data to obtain the echo energy corresponding to each echo sampling point includes:

[0036] The echo data is normalized based on the Z-score normalization algorithm to obtain the echo energy corresponding to each echo sampling point.

[0037] In one or more embodiments, the normalizing the echo data based on the Z-score normalization algorithm to obtain the echo energy corresponding to each echo sampling point includes:

[0038] The echo data is processed by formulas (1) and (2) to obtain the echo energy corresponding to each echo sampling point:

[0039] P noise =quantile(Y,0.1) (1)

[0040]

[0041] Wherein, Y is the set of original echo energies of all sampling points in the echo data, P noise is the thermal noise level, i is the echo sampling point number, Y(i) is the original echo energy at sampling point i, y(i) is the normalized echo energy, The energy is greater than P noise The average energy of the sampling points, σ ​​is the energy greater than P noise The energy standard deviation of the sampling points.

[0042] In one or more embodiments, determining the position of the optimal wavelet according to the echo data and a preset rule, and determining the position of the re-tracking point on the rising edge of the optimal wavelet, includes:

[0043] determining a reference rising edge in the echo data according to an energy difference and a rate of change of the energy difference between adjacent echo sampling points in the echo data;

[0044] Determine the reference sub-wave where the reference rising edge is located;

[0045] The wavelet with the largest cumulative energy value in the reference wavelet is taken as the target wavelet; wherein, the starting energy point of the reference rising edge plus the third threshold is taken as the end point of the echo energy, and a straight line with the end point as the reference and parallel to the horizontal axis is obtained, and the energy enclosed between the straight line and the echo waveform is taken as the cumulative energy value.

[0046] In one or more embodiments, determining a reference rising edge in the echo data based on an energy difference and a rate of change of the energy difference between adjacent echo sampling points in the echo data includes:

[0047] determining the echo sampling points constituting the rising edge according to the energy difference between adjacent echo sampling points in the echo data and the rate of change of the energy difference;

[0048] In a rising edge consisting of at least three consecutive echo sampling points, a rising edge in which the absolute value of the difference between adjacent sampling points in the rising edge is greater than a first threshold and the sum of the energy values ​​of all echo sampling points is greater than a second threshold is determined as a reference rising edge; or

[0049] In a rising edge consisting of two consecutive echo sampling points, a rising edge in which the absolute value of the difference between adjacent sampling points in the rising edge is greater than three times the second threshold is determined as a reference rising edge.

[0050] In one or more embodiments, acquiring the re-tracking point based on the rising edge of the target wavelet includes:

[0051] The energy value of the re-tracking point is obtained by formula (3) and (4): R ;

[0052] A=y p+m-1 -y p (3)

[0053] E R =y p +Tl4*A (4)

[0054] Among them, the starting sampling point of the target rising edge is p, the rising edge consists of m sampling points, y p is the energy value corresponding to the starting sampling point p, y p+m+1 is the energy value corresponding to the highest sampling point of the rising edge, A is the target rising edge amplitude, and Tl4 is the fourth threshold;

[0055] According to the energy value E R The re-tracking point is determined.

[0056] In one or more embodiments, determining the water level value of the target lake in the current period according to the tracking points includes:

[0057] According to formulas (5), (6), and (7), the water level value of the target lake in the current cycle is obtained:

[0058] ΔR=Δt*c / 2 (5)

[0059] R1=R0+ΔR (6)

[0060] H=H sat -(R1+R wet +R dry +R iono )-Cse -C pt -C EGM2008 (7)

[0061] Wherein, Δt is the time interval between the re-tracking point and the preset tracking gate, the preset tracking gate is the actual moment when the current radar pulse signal contacts the lake surface, ΔR is the satellite lake surface distance correction, R0 is the distance from the satellite to the preset tracking gate, c is the speed of light, R1 is the distance from the satellite to the lake surface, and H sat is the satellite altitude, R dry and R wet is the dry and wet troposphere correction value of the satellite radar pulse signal on the propagation path, R iono is the ionospheric correction value, C se is the correction for the Earth's solid tide, C pt is the correction value of the Earth's extreme tide, C EGM2008 is the elevation correction value, and H is the target lake water level value corresponding to the footprint data.

[0062] In one or more embodiments, after determining the water level value of the target lake corresponding to the current echo according to the re-tracking point, the method further includes:

[0063] The average value of the target lake water level corresponding to the along-track footprint points is used as the lake water level in the current observation period; wherein the along-track footprint points are the along-track footprint data of the satellite radar on the target lake; here, the area on the ground covered by the radar satellite transmission signal is also called the radar footprint.

[0064] A water level time series of the target lake is obtained based on the water level values ​​of the target lake in multiple observation periods.

[0065] The rapid development of satellite altimetry technology has brought new opportunities for dynamic monitoring of large-scale lakes. Satellite altimeters can monitor surface elevation over a wide range over long periods of time, including those of oceans, sea ice, lakes, and rivers. Commonly used altimetry satellites include the ERS series of satellites (including ERS-1, ERS-2, Envisat, and SARAL) with a 35-day revisit period, the T / P series of satellites (including T / P, Jason-1 / 2 / 3) with a 10-day revisit period, and the more recently developed Cryosat-2, Sentinel-3A, and Sentinel-3B. Altimetry satellites use altimeters onboard their spacecraft to observe the Earth. Satellite altimeters generally use the time difference between transmitted and received pulses to determine the satellite-to-ground distance, thereby inverting ground elevation. The key to accurate lake level tracking is to find the point in the echo where the pulse touches the lake surface. To obtain this re-tracking point, waveform re-tracking of the radar echo is required.

[0066] Existing waveform re-tracking algorithms are either physical or empirical models designed for the ocean or sea ice, which perform poorly on lakes and have large errors, or complex spatiotemporal models that are time-consuming and not very robust. There are two most commonly used lake water level extraction methods: 1. Using the ICE-1 method, which is designed for sea ice and is an empirical threshold method. This method is developed from the center of gravity offset model OCOG. The central idea of ​​OCOG is to fit the echo with a rectangular box to obtain the center of gravity position of the echo and the amplitude P of the echo. u , and the width of the echo, the first intersection of the rectangle and the echo is the position of the re-tracking point. The ICE-1 method uses an empirical threshold based on OCOG to obtain the position of the re-tracking point, and the P obtained by the OCOG method is u As the echo amplitude, the empirical threshold (T l ) interpolation to find the energy P u T l The point is used as the re-tracking point.

[0067] 2. Use the complex spatiotemporal dynamic model tshydro to solve the water level. This method takes into account both the temporal correlation of the water level time series and the spatial correlation of the water level along the satellite radar's footprint. The central idea of ​​the tshydro model is that in the time series, the closer the time, the stronger the correlation of the water levels. In space, there is a certain random error between the along-track water level and the overall water level of the lake, and the distribution of this random error may be asymmetric. tshydro divides the water level time series into a process model (the real water level time series) and an observation model (the size of the error of the observed value from the real water level). The process model uses a simple random walk model, and the observation model uses a Gaussian plus Cauchy mixed distribution model.

[0068] Based on the above embodiment, in an application embodiment, the above lake water level determination method further includes:

[0069] The example of the present invention uses the global secondary non-time critical (NTC) data set of the Sentinel-3A satellite SRAL altimeter.

[0070] The lake water level extraction method provided in this embodiment is suitable for Figure 4 Altimetry satellites operate in the manner shown. Altimetry satellites typically carry limited-pulse radar altimeters, which often have larger ground footprints. However, the frequency of transmitting pulse signals is relatively high, so there is a certain overlap between the ground footprints.

[0071] The above-mentioned satellite transmits a vertical pulse signal to the ground. The pulse signal is reflected by the ground and received by the satellite again. By recording the transmission time and reception time difference of the pulse on the satellite, the distance between the satellite and the ground can be preliminarily determined. However, due to the large footprint of the radar altimeter, the signal returned is a wide pulse echo. It is difficult to accurately find a moment to represent the ground elevation. Therefore, it is necessary to record a section of the reflected signal and find a moment from it to represent the moment when the satellite touches the ground. This process is generally called waveform retracking. When the radar pulse illuminates a flat ideal reflector, the echo signal is formed as follows Figure 5 As shown. When it first contacts the reflective surface, the illuminated area is a circle with a continuously increasing diameter, forming the rising edge of the echo. When the illuminated area reaches its maximum value, the rising edge reaches its peak, and then the circle becomes a ring, but the total illuminated area remains unchanged. At this time, the reflected signal received by the satellite continues to weaken, forming a falling edge of the echo. An ideal echo consists of a rising edge and a falling edge. Since the rising edge corresponds to the process of rising reflected energy, it is also the time when the pulse signal begins to contact the reflective surface. Therefore, the present invention focuses on the rising edge and finds the re-tracking point on the rising edge, which represents the water surface elevation.

[0072] Unlike an ideal reflector, the land surface has large fluctuations in elevation, and the radar footprint is large. When the ground elevation within the footprint is not uniform, the echo signal formed often has multiple sub-waves (such as Figure 6 (b)), this phenomenon is often called echo contamination. In addition, when the lake surface is frozen, the radar echo will form two strong reflections between the air-ice surface and the ice surface-water surface, so there will be two consecutive rising edges in the echo signal, such as Figure 7 (a) shows that the traditional echo re-tracking method is designed to extract ocean or sea ice elevation, so it performs worse on inland lakes, especially when the echo is severely polluted or the lake is frozen.

[0073] like Figure 5 As shown in FIG, the data processing method for obtaining the target lake water level includes:

[0074] Step 1: Prepare satellite radar altimetry data, extract key field information and filter footprints.

[0075] The satellite radar altimetry data in this embodiment of the present invention utilizes echo and geophysical data. In addition to extracting the echo data, it is also necessary to extract relevant fields such as the data time, longitude and latitude, satellite ground distance corresponding to the preset retracking algorithm, ionospheric and tropospheric range corrections, geophysical corrections, and quality control. Next, the lake surface footprint data is screened to remove footprint data that deviates too far from the lake surface elevation and data with severe waveform contamination.

[0076] Step 2: Echo normalization to make the energy of different echoes more comparable.

[0077] Since background noise often has low energy, to better normalize the echo energy, we need to exclude the noise before normalizing the echo. Assuming that the echo energy conforms to a normal distribution, we use quantile statistics to obtain the noise level, and then use the Z-score method to normalize the entire echo. The specific echo normalization method is as follows:

[0078] P noise =quantile(Y,0.1) (1)

[0079]

[0080] Among them, Y is the original echo energy, P noise is the thermal noise level, i is the echo sampling point number, y is the normalized echo energy, The energy is greater than P noise The average energy of the sampling points, σ ​​is the energy greater than P noise The energy standard deviation of the sampling points.

[0081] Step 3: Identify the rising edge of the echo.

[0082] Among them, we use certain threshold rules to identify and filter rising edges. First, we calculate two basic parameters d1 and d2, the energy difference between adjacent sampling points and the rate of change of the energy difference.

[0083] d1=y(i+1)-y(i) (3)

[0084] d2=y(i+1)+y(i-1)-2y(i) (4)

[0085] Next, we look for the sampling points that make up the rising edge. Based on the energy change process of the rising edge, we divide the rising edge into two types: ocean-like and ice-like rising edges. The ocean-like rising edge generally consists of two parts: accelerated rising and decelerated rising (such as Figure 6 (a)), while the ice-like rising edge generally only includes the accelerated rising part (e.g. Figure 6 (b)). Therefore, after obtaining the first rising point, this paper first searches for the accelerated rising sampling point, and then searches for the decelerated rising sampling point. The judgment condition for the rising point is that d1 is greater than the threshold Tl1, the judgment condition for the accelerated rising sampling point is d1>Tl1 and d2≥0, and the judgment condition for the decelerated rising point is d1>Tl1 and d2<0.

[0086] Finally, qualified rising edges are screened. Generally, three or more consecutive sampling points constitute a rising edge. If the maximum d1 value in the rising edge is greater than 2Tl1 and the total rising energy is greater than the threshold Tl2, the rising edge is considered a qualified rising edge. In special cases, if there are two consecutive rising sampling points and the d1 of the starting point is greater than 3Tl2, this method also considers these two points to constitute a qualified rising edge. After analyzing thousands of global lake surface echo samples used for echo classification, Tl1 and Tl2 are set to 0.1 and 0.5.

[0087] Step 4: From all rising edges of the echo, select the best rising edge to represent the lake surface.

[0088] In this case, the rising edge with the largest sub-wave accumulated energy is selected as the optimal rising edge. Taking the starting point of each rising edge as the basis, add Tl3 (0.3) as the end value of the echo energy. With the end value as the benchmark, draw a straight line parallel to the horizontal axis. The energy between the line and the echo is taken as the sub-wave accumulated energy (online part) (such as Figure 7 Selecting the rising edge with the largest accumulated wavelet energy as the rising edge of the lake can more accurately obtain the rising edge of the lake surface from the echo of the frozen lake surface, because frozen lakes often have two consecutive rising edges, and the energy value of the second rising edge is generally much higher than that of the first rising edge (such as Figure 7 (a)). In addition, the rising edge of the wavelet with the largest accumulated energy is selected as the rising edge of the lake, which can accurately represent the lake surface echo, such as Figure 7 (b) and 7(c), because the lake surface is often the dominant reflector in the center of the radar footprint, and the reflection intensity of water is generally higher than that of general reflectors, the lake surface reflection signal tends to last longer, forming a wide and slowly decaying falling edge, and the accumulated echo energy is large. In contrast, the land signals around the lake tend to decay rapidly and last for a short time because they are generally located at the edge of the footprint and have a smaller area, so the accumulated energy value of the noise echo is generally small.

[0089] Step 5: Get the re-tracking point on the optimal rising edge.

[0090] When the rising edge is an ocean-like rising edge, the duration of the rising edge is generally longer, and the midpoint of the rising edge can better represent the lake water level. However, when the rising edge is an ice-like rising edge, the duration of the rising edge is shorter, and the midpoint of the rising edge may not be a good representation of the lake water level. We use the height of the rising edge as the amplitude (A) and obtain the re-tracking point through the threshold (Tl4). Assuming that the starting point of the rising edge is p, the rising edge consists of m points, and the energy value of the re-tracking point is E R The energy value is E R The intersection of the line parallel to the x-axis and the rising edge is the re-tracking point.

[0091] A=y p+m-1 -y p (5)

[0092] E R =y p +Tl4*A (6)

[0093] A threshold of 0.5 is used for ocean-like rising edges, while for ice-like rising edges, a large number of threshold experiments show that a threshold of 0.2 (suitable for low-resolution altimeters) or 0.4 (suitable for SAR altimeters) should be used.

[0094] Step 6: After distance re-tracking and correction, obtain the lake water level.

[0095] After obtaining the re-tracking point, the time interval (Δt) between the re-tracking point and the preset tracking gate is used to obtain the satellite lake surface distance correction (ΔR). Since the distance from the satellite to the preset tracking gate of the echo (R0) is given in the altimetry data, the distance from the satellite to the lake surface (R1) can be obtained by adding the distance re-tracking correction. Then, the satellite altitude H is used to calculate the distance between the satellite and the lake surface. sat Subtracting R1, we can get the initial water level of the footprint point on the lake surface. Then, we can make the dry and wet tropospheric correction on the propagation path (R dry and R wet ) and ionospheric correction (R iono ), and geophysical correction (earth solid tide correction C se and Earth's polar tide correction C pt In addition, in order to obtain a physically meaningful water level value, it is necessary to perform an elevation datum conversion, changing the elevation datum from the Earth reference ellipsoid to the physically meaningful geoid height. The geoid EGM2008 is selected as the unified elevation datum. The elevation of EGM2008 on the satellite reference ellipsoid is the elevation correction value C. EGM2008 Finally, the water level H at the footprint point is obtained according to the following formula.

[0096] ΔR=Δt*c / 2 (7)

[0097] R1=R0+ΔR (8)

[0098] H=H sat -(R1+R wet +R dry +R iono )-C se -C pt -C EGM2008 (9)

[0099] where c is the speed of light.

[0100] Finally, we took the average of the water levels at the footprint points along the track as the lake water level for that observation period.

[0101] Step 7: Process the periodic observation data to obtain the lake water level time series.

[0102] The lake surface radar altimetry data of each observation period are processed in sequence to form a long-term series of lake water level data. Taking Big Bear Lake as an example, the final lake water level obtained by Sentinel-3A is as follows: Figure 9 Compared with the commonly used ICE-1 method, the lake water level obtained by the MSIE method is significantly more continuous and has smaller errors.

[0103] The embodiments of the present invention also have the following beneficial effects:

[0104] 1. The lake surface echo decomposition method of the embodiment of the present invention has simple rules, strong robustness, strong independence, and a wide range of applications. It can better separate the two consecutive rising edges of the echo of the frozen lake surface, which is beneficial to reducing the water level extraction error of the frozen lake surface.

[0105] 2. The embodiment of the present invention uses the lake surface echo decomposition method of the embodiment of the present invention to utilize the energy change process of the rising edge to divide the echo rising edge into an ocean-like rising edge and an ice-like rising edge. This distinction is conducive to adopting different thresholds for different types of echoes, thereby improving the accuracy of lake surface water level extraction.

[0106] 3. The screening rules for the optimal sub-wavelet of the lake surface in the embodiment of the present invention are simple, especially the rule of selecting the sub-wavelet with the largest accumulated energy. This rule can not only effectively screen out lake surface echoes with concentrated reflected energy, but also correctly select lake surface echoes from two consecutive rising edges of frozen lakes. This rule can effectively reduce water level extraction errors.

[0107] 4. This embodiment of the present invention uses a threshold of 0.5 for ocean-like rises. The optimal threshold for ice-like rises was determined through extensive threshold experimentation. Experimental findings revealed that the optimal threshold for low-resolution altimeters is 0.2, and for SAR altimeters is 0.4. These thresholds, derived from these experiments, are more targeted and applicable to multi-source satellite radar altimetry data.

[0108] It should be noted that for the aforementioned method embodiments, for simplicity of description, they are all expressed as a series of action combinations. However, those skilled in the art should be aware that the present invention is not limited by the order of the actions described, because according to the present invention, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in this specification are all preferred embodiments, and the actions and modules involved are not necessarily required by the present invention.

[0109] According to another aspect of the embodiments of the present invention, a lake water level determination device for implementing the above lake water level determination method is also provided. Figure 10 As shown, the device includes:

[0110] An acquisition unit 1002 is configured to acquire satellite radar altimetry data within a target lake; wherein the satellite radar altimetry data includes echo data and geophysical data of at least one observation period;

[0111] The normalization unit 1004 is configured to filter the echo data and perform normalization on the filtered echo data to obtain the echo energy corresponding to each echo sampling point;

[0112] A first determining unit 1006 is configured to determine the position of an optimal wavelet based on the echo data and a preset rule, and to determine the position of a re-tracking point on the rising edge of the optimal wavelet; wherein the re-tracking point is used to indicate the initial contact point between the ranging pulse signal and the target lake during the current observation period;

[0113] The second determining unit 1008 is configured to determine the water level value of the target lake corresponding to the current echo according to the re-tracking point.

[0114] In an embodiment of the present invention, a method is adopted for obtaining satellite radar altimetry data within a target lake; wherein the satellite radar altimetry data is echo data and geophysical data including at least one observation period; the echo data is screened and the screened echo data is standardized to obtain the echo energy corresponding to each echo sampling point; the position of the optimal sub-wave is determined according to the echo data and preset rules, and the position of the re-tracking point is determined on the rising edge of the optimal sub-wave; wherein the re-tracking point is used to indicate the initial contact point between the ranging pulse signal and the target lake in the current observation period; a method is provided for determining the water level value of the target lake corresponding to the current echo according to the re-tracking point. In the above method, since the echo data is standardized and the re-tracking point is determined, the lake surface echo with concentrated reflected energy can be better screened out, and the lake surface echo can be correctly selected from two consecutive rising edges of the frozen lake, which can effectively reduce the water level extraction error, thereby solving the technical problem of large error or poor robustness in the process of determining the lake water level by radar altimetry data.

[0115] In one or more embodiments, the standardization unit 1004 includes:

[0116] The normalization module is used to perform normalization processing on the echo data based on the Z-score normalization algorithm to obtain the echo energy corresponding to each echo sampling point.

[0117] In one or more embodiments, the standardization module includes:

[0118] The processing subunit is used to process the echo data using formulas (1) and (2) to obtain the echo energy corresponding to each echo sampling point:

[0119] P noise =quantile(Y,0.1) (1)

[0120]

[0121] Wherein, Y is the set of original echo energies of all sampling points in the echo data, P noise is the thermal noise level, i is the echo sampling point number, Y(i) is the original echo energy at sampling point i, y(i) is the normalized echo energy, The energy is greater than P noise The average energy of the sampling points, σ ​​is the energy greater than P noise The energy standard deviation of the sampling points.

[0122] In one or more embodiments, the root first determining unit 1006 includes:

[0123] A first determining module is configured to determine a reference rising edge in the echo data according to an energy difference and a change rate of the energy difference between adjacent echo sampling points in the echo data;

[0124] A second determining module is used to determine the reference sub-wave where the reference rising edge is located;

[0125] a third determination module, configured to select the wavelet with the largest cumulative energy value among the reference wavelets as the target wavelet; wherein the starting energy point of the reference rising edge plus a third threshold is used as the end point of the echo energy, and a straight line parallel to the horizontal axis with the end point as a reference is obtained, and the energy enclosed between the line and the echo waveform is used as the cumulative energy value;

[0126] The first acquisition module is configured to acquire a re-tracking point based on the target rising edge.

[0127] In one or more embodiments, the first determining module includes:

[0128] a first determining subunit, configured to determine echo sampling points constituting a rising edge according to energy differences and energy difference change rates between adjacent echo sampling points in the echo data;

[0129] a second determining subunit, configured to determine, among rising edges consisting of at least three consecutive echo sampling points, a rising edge in which the absolute value of the difference between adjacent sampling points in the rising edge is greater than a first threshold and the sum of the energy values ​​of all echo sampling points is greater than a second threshold as a reference rising edge; or

[0130] The third determining subunit is configured to determine, among the rising edges consisting of two consecutive echo sampling points, a rising edge in which the absolute value of the difference between adjacent sampling points in the rising edge is greater than three times the second threshold as a reference rising edge.

[0131] In one or more embodiments, the first acquisition module includes:

[0132] The first acquisition subunit is used to obtain the energy value of the re-tracking point as E according to formulas (3) and (4): R ;

[0133] A=y p+m-1 -y p (3)

[0134] E R =y p +Tl4*A (4)

[0135] Among them, the starting sampling point of the target rising edge is p, the rising edge consists of m sampling points, y p is the energy value corresponding to the starting sampling point p, y p+m+1 is the energy value corresponding to the highest sampling point of the rising edge, A is the target rising edge amplitude, and Tl4 is the fourth threshold;

[0136] The fourth determining subunit is configured to determine the energy value E according to the energy value E. R The re-tracking point is determined.

[0137] In one or more embodiments, the second determining unit 1008 includes:

[0138] The second acquisition module is used to obtain the water level value of the target lake in the current cycle according to formulas (5), (6), and (7):

[0139] ΔR=Δt*c / 2 (5)

[0140] R1=R0+ΔR (6)

[0141] H=H sat -(R1+R wet +R dry +R iono )-C se -C pt -C EGM2008 (7)

[0142] Wherein, Δt is the time interval between the re-tracking point and the preset tracking gate, the preset tracking gate is the actual moment when the current radar pulse signal contacts the lake surface, ΔR is the satellite lake surface distance correction, R0 is the distance from the satellite to the preset tracking gate, c is the speed of light, R1 is the distance from the satellite to the lake surface, and Hsat is the satellite altitude, R dry and R wet is the dry and wet troposphere correction value of the satellite radar pulse signal on the propagation path, R iono is the ionospheric correction value, C se is the correction for the Earth's solid tide, C pt is the correction value of the Earth's extreme tide, C EGM2008 is the elevation correction value, and H is the target lake water level value corresponding to the footprint data.

[0143] In one or more embodiments, the lake water level determination device further includes:

[0144] A third determination module is configured to use the average value of the water level of the target lake corresponding to the along-track footprint points as the lake water level in the current observation period; wherein the along-track footprint points are along-track footprint data of the satellite radar on the target lake;

[0145] The third acquisition unit is used to acquire the water level time series of the target lake according to the water level values ​​of the target lake in multiple periods.

[0146] According to another aspect of the embodiment of the present invention, an electronic device for implementing the above-mentioned lake water level determination method is also provided. The electronic device may be Figure 11 The terminal device or server shown in FIG. This embodiment is described by taking the electronic device as a terminal as an example. Figure 11 As shown, the electronic device includes a memory 1102 and a processor 1104. The memory 1102 stores a computer program, and the processor 1104 is configured to execute the steps in any of the above method embodiments through the computer program.

[0147] Optionally, in this embodiment, the electronic device may be located in at least one network device among a plurality of network devices of a computer network.

[0148] Optionally, in this embodiment, the processor may be configured to execute the following steps through a computer program:

[0149] S1, obtaining satellite radar altimetry data within the target lake; wherein the satellite radar altimetry data includes echo data and geophysical data of at least one observation cycle;

[0150] S2, filtering the echo data and normalizing the filtered echo data to obtain the echo energy corresponding to each echo sampling point;

[0151] S3, determining the position of the optimal wavelet based on the echo data and preset rules, and determining the position of the re-tracking point on the rising edge of the optimal wavelet; wherein the re-tracking point is used to indicate the initial contact point between the ranging pulse signal and the target lake in the current observation period;

[0152] S4, determining the water level value of the target lake corresponding to the current echo according to the re-tracking point.

[0153] Alternatively, those skilled in the art will appreciate that Figure 11 The structure shown is for illustration only, and the electronic device may also be a smart phone (such as an Android phone, an iOS phone, etc.), a tablet computer, a PDA, a mobile Internet device (MID), a PAD, or other terminal devices. Figure 11 It does not limit the structure of the electronic device. For example, the electronic device may also include Figure 11 More or fewer components (such as network interfaces, etc.) as shown in, or with Figure 11 Different configurations shown.

[0154] Among them, the memory 1102 can be used to store software programs and modules, such as the program instructions / modules corresponding to the lake water level determination method and device in the embodiment of the present invention. The processor 1104 executes various functional applications and data processing by running the software programs and modules stored in the memory 1102, that is, realizing the above-mentioned lake water level determination method. The memory 1102 may include a high-speed random access memory, and may also include a non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory. In some instances, the memory 1102 may further include a memory remotely located relative to the processor 1104, and these remote memories may be connected to the terminal via a network. Examples of the above-mentioned networks include, but are not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof. Among them, the memory 1102 can be used specifically, but not limited to, to store information such as satellite radar altimetry data. As an example, such as Figure 11 As shown, the memory 1102 may include, but is not limited to, the acquisition unit 1002, the normalization unit 1004, the first determination unit 1006, and the second determination unit 1008 in the lake water level determination device. In addition, it may also include, but is not limited to, other module units in the lake water level determination device, which will not be repeated in this example.

[0155] Optionally, the transmission device 1106 is configured to receive or send data via a network. Specific examples of the network may include a wired network and a wireless network. In one embodiment, the transmission device 1106 includes a network interface controller (NIC), which can be connected to other network devices and a router via a network cable to communicate with the Internet or a local area network. In one embodiment, the transmission device 1106 is a radio frequency (RF) module, which is configured to communicate with the Internet wirelessly.

[0156] In addition, the electronic device further includes: a display 1108 for displaying the satellite radar altimetry data; and a connection bus 1110 for connecting the various module components in the electronic device.

[0157] In other embodiments, the terminal device or server may be a node in a distributed system, wherein the distributed system may be a blockchain system, and the blockchain system may be a distributed system formed by connecting multiple nodes through network communication. The nodes may form a peer-to-peer (P2P) network, and any computing device, such as a server, terminal, or other electronic device, may become a node in the blockchain system by joining the peer-to-peer network.

[0158] According to one aspect of the present application, a computer program product or computer program is provided, comprising computer instructions stored in a computer-readable storage medium. A processor of a computer device reads the computer instructions from the computer-readable storage medium and executes the computer instructions, causing the computer device to perform the above-described lake water level determination method. The computer program is configured to execute the steps of any of the above-described method embodiments when executed.

[0159] Optionally, in this embodiment, the computer-readable storage medium may be configured to store a computer program for performing the following steps:

[0160] S1, obtaining satellite radar altimetry data within the target lake; wherein the satellite radar altimetry data includes echo data and geophysical data of at least one observation cycle;

[0161] S2, filtering the echo data and normalizing the filtered echo data to obtain the echo energy corresponding to each echo sampling point;

[0162] S3, determining the position of the optimal wavelet based on the echo data and preset rules, and determining the position of the re-tracking point on the rising edge of the optimal wavelet; wherein the re-tracking point is used to indicate the initial contact point between the ranging pulse signal and the target lake in the current observation period;

[0163] S4, determining the water level value of the target lake corresponding to the current echo according to the re-tracking point.

[0164] Optionally, in this embodiment, a person of ordinary skill in the art may understand that all or part of the steps in the various methods of the above embodiments may be completed by instructing the hardware related to the terminal device through a program, and the program may be stored in a computer-readable storage medium, which may include: a flash drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, etc.

[0165] The serial numbers of the above embodiments of the present invention are for description only and do not represent the advantages or disadvantages of the embodiments.

[0166] If the integrated units in the above embodiments are implemented in the form of software functional units and sold or used as independent products, they can be stored in the above-mentioned computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes a number of instructions for causing one or more computer devices (such as personal computers, servers, or network devices) to execute all or part of the steps of the methods of various embodiments of the present invention.

[0167] In the above embodiments of the present invention, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0168] In the several embodiments provided in this application, it should be understood that the disclosed client can be implemented in other ways. The device embodiments described above are merely illustrative. For example, the division of units is merely a logical functional division. In actual implementation, there may be other division methods, such as combining or integrating multiple units or components into another system, or ignoring or not implementing some features. Furthermore, the mutual coupling or direct coupling or communication connection shown or discussed may be through some interface, indirect coupling or communication connection of units or modules, and may be electrical or other forms.

[0169] Units described as separate components may or may not be physically separate, and components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0170] In addition, the functional units in the various embodiments of the present invention may be integrated into a single processing unit, each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0171] The above are only preferred embodiments of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for determining lake water level, characterized in that: include: Acquire satellite radar altimetry data within the target lake; wherein the satellite radar altimetry data includes echo data and geophysical data for at least one observation period; Filtering the echo data and normalizing the filtered echo data to obtain the echo energy corresponding to each echo sampling point; The position of the optimal wavelet is determined according to the echo data and a preset rule, and the position of the re-tracking point is determined on the rising edge of the optimal wavelet, including: determining the echo sampling points constituting the rising edge according to the energy difference and the rate of change of the energy difference between adjacent echo sampling points in the echo data; in a rising edge consisting of at least three consecutive echo sampling points, determining the rising edge in which the absolute value of the difference between adjacent sampling points in the rising edge is greater than a first threshold and the sum of the energy values ​​of all echo sampling points is greater than a second threshold as a reference rising edge; or in a rising edge consisting of two consecutive echo sampling points, determining the absolute value of the difference between adjacent sampling points in the rising edge as a reference rising edge. A rising edge with a value greater than three times the second threshold is determined as a reference rising edge; a reference sub-wave where the reference rising edge is located is determined; the sub-wave with the largest cumulative energy value in the reference sub-wave is used as a target sub-wave; wherein, the starting energy point of the reference rising edge plus the third threshold is used as the end point of the echo energy, and a straight line with the end point as a reference and parallel to the horizontal axis is obtained, and the energy enclosed between the line and the echo waveform is used as the cumulative energy value; the re-tracking point is obtained based on the rising edge of the target sub-wave; the re-tracking point is used to indicate the initial contact point between the ranging pulse signal and the target lake in the current observation period; The water level value of the target lake corresponding to the current echo is determined according to the re-tracking point.

2. The method according to claim 1, characterized in that The echo data is normalized to obtain the echo energy corresponding to each echo sampling point, including: The echo data is normalized based on the Z-score normalization algorithm to obtain the echo energy corresponding to each echo sampling point.

3. The method according to claim 2, characterized in that The Z-score normalization algorithm is used to normalize the echo data to obtain the echo energy corresponding to each echo sampling point, including: The echo data is processed by formulas (1) and (2) to obtain the echo energy corresponding to each echo sampling point: P noise =quantile(Y,0.1) (1) Wherein, Y is the set of original echo energies of all sampling points in the echo data, P noise is the thermal noise level, i is the echo sampling point number, Y(i) is the original echo energy at sampling point i, y(i) is the normalized echo energy, The energy is greater than P noise The average energy of the sampling points, σ ​​is the energy greater than P noise The energy standard deviation of the sampling points.

4. The method according to claim 1, wherein The acquiring the re-tracking point based on the rising edge of the target wavelet comprises: The energy value E of the re-tracking point is obtained by formulas (3) and (4): R ; A=y p+m-1 -and p (3) AND R =and p +Tl4*A (4) Among them, the starting sampling point of the target rising edge is p, the rising edge consists of m sampling points, y p is the energy value corresponding to the starting sampling point p, y p+m+1 is the energy value corresponding to the highest sampling point of the rising edge, A is the target rising edge amplitude, and Tl4 is the fourth threshold; According to the energy value E R The re-tracking point is determined.

5. The method according to claim 1, wherein The step of determining the water level of the target lake corresponding to the current echo according to the re-tracking point includes: According to formulas (5), (6), and (7), the water level value of the target lake in the current cycle is obtained: ΔR=Δt*c / 2 (5) R1=R0+ΔR (6) H=H sat -(R1+R wet +R dry +R iono )-C se -C pt -C EGM2008 (7) Wherein, Δt is the time interval between the re-tracking point and the preset tracking gate, the preset tracking gate is the actual moment when the current radar pulse signal contacts the lake surface, ΔR is the satellite lake surface distance correction, R0 is the distance from the satellite to the preset tracking gate, c is the speed of light, R1 is the distance from the satellite to the lake surface, and H sat is the satellite altitude, R dry and R wet is the dry and wet troposphere correction value of the satellite radar pulse signal on the propagation path, R iono is the ionospheric correction value, C se is the correction for the Earth's solid tide, C pt is the correction value of the Earth's extreme tide, C EGM2008 is the elevation correction value, and H is the target lake water level value corresponding to the satellite footprint data.

6. The method according to claim 1, characterized in that After determining the water level value of the target lake corresponding to the current echo according to the re-tracking point, the method further includes: The average value of the water level of the target lake corresponding to the along-track footprint points is used as the lake water level in the current observation period; wherein the along-track footprint points are the along-track footprint data of the satellite radar on the target lake; A water level time series of the target lake is obtained based on the water level values ​​of the target lake in multiple observation periods.

7. A lake water level determination device, characterized in that: include: An acquisition unit is used to acquire satellite radar altimetry data within the target lake; wherein the satellite radar altimetry data includes echo data and geophysical data of at least one observation cycle; a normalization unit, configured to filter the echo data and perform normalization on the filtered echo data to obtain an echo energy corresponding to each echo sampling point; A first determining unit is configured to determine the position of an optimal wavelet based on the echo data and a preset rule, and to determine the position of a re-tracking point on a rising edge of the optimal wavelet; the unit comprising: determining echo sampling points constituting a rising edge based on an energy difference and a rate of change of the energy difference between adjacent echo sampling points in the echo data; and determining, in a rising edge consisting of at least three consecutive echo sampling points, a rising edge in which the absolute value of the difference between adjacent sampling points in the rising edge is greater than a first threshold and the sum of the energy values ​​of all echo sampling points is greater than a second threshold as a reference rising edge; or In a rising edge consisting of two consecutive echo sampling points, a rising edge in which the absolute value of the difference between adjacent sampling points in the rising edge is greater than three times a second threshold is determined as a reference rising edge; a reference sub-wave in which the reference rising edge is located is determined; and a sub-wave with the largest cumulative energy value in the reference sub-wave is used as a target sub-wave; wherein, the starting energy point of the reference rising edge plus the third threshold is used as the end point of the echo energy, and a straight line with the end point as a reference and parallel to the horizontal axis is obtained, and the energy enclosed between the straight line and the echo waveform is used as the cumulative energy value; the re-tracking point is obtained based on the rising edge of the target sub-wave, and the re-tracking point is used to indicate the initial contact point between the ranging pulse signal and the target lake in the current observation period; The second determining unit is configured to determine the water level value of the target lake corresponding to the current echo according to the re-tracking point.

8. An electronic device comprising a memory and a processor, characterized in that: A computer program is stored in the memory, and the processor is configured to execute the method according to any one of claims 1 to 6 through the computer program.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium includes a stored program, wherein the method according to any one of claims 1 to 6 is executed when the program is executed.

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