Sea wave characteristic analysis method based on electromagnetic field observation data

Abstract

The invention discloses an electromagnetic field observation data-based sea wave characteristic analysis method, which comprises the following steps of: processing electromagnetic field data by adopting a time-frequency spectrum analysis method, identifying distribution characteristics of electromagnetic field signals caused by sea waves at different time and frequencies through time-frequency decomposition, and extracting periods and time-varying characteristics of the sea waves; preprocessing the electromagnetic field data by using dominant frequency analysis and band-pass filtering technologies to obtain sea wave induced magnetic field time domain data; time domain and frequency domain induction electromagnetic field polarization direction analysis technologies are combined, and the movement direction of sea waves and the change characteristics of the sea waves along with time are inferred by measuring the change of the electromagnetic field polarization direction; the quantitative relation between the sea wave induction electromagnetic field intensity and the sea wave height is established, and the sea wave height change of the place is effectively estimated through the sea wave induction electromagnetic field intensity. By comprehensively analyzing the electromagnetic field data, the sea wave period, the time-varying characteristics, the motion direction and the sea wave height are evaluated, and a new way is provided for marine environment monitoring.

Description

Technical Field

[0001] The present invention relates to the technical field of ocean wave monitoring, and in particular to an ocean wave characteristic analysis method based on electromagnetic field observation data. Background Art

[0002] Traditional wave monitoring methods mostly rely on equipment such as buoys and radars, but there are problems such as high deployment cost, complex maintenance, and limited coverage. Marine electromagnetic technology is a commonly used detection technology in marine geophysics. The common working method is to place electromagnetic recorders on the seabed or water body to record active source or natural source signals transmitted through the water body and the seabed, thereby realizing the detection of underground geological structures. However, since seawater is a good conductor, the movement of seawater generates an induced electromagnetic field due to the cutting of the geomagnetic field, which is recorded by the electromagnetic recorder on the water body or the seabed and becomes the noise component of the geophysical detection signal; in shallow water, the influence of waves is particularly obvious, and its induced electromagnetic field energy is much greater than the natural electromagnetic field component. However, the wave induced electromagnetic field is generated by the movement of waves, and therefore carries the characteristic information of the waves, such as period, movement direction, and wave height. In recent years, research on wave monitoring using wave induced electromagnetic fields has gradually emerged, but how to accurately and efficiently extract wave characteristic parameters (such as period, wave height, movement direction) and establish a quantitative relationship with the wave induced electromagnetic field is still a technical challenge facing this field. Summary of the invention

[0003] In view of this, the purpose of the present invention is to provide a wave characteristic analysis method based on electromagnetic field observation data, which is an efficient and accurate wave characteristic extraction and estimation method. By comprehensively analyzing the electromagnetic field data, it can realize the evaluation of the wave period, time-varying characteristics, movement direction and wave height, providing a new way for marine environment monitoring.

[0004] The present invention solves the technical problem by adopting the following technical solution:

[0005] A method for analyzing ocean wave characteristics based on electromagnetic field observation data comprises the following steps:

[0006] Step S10, extraction of wave period and time-varying features:

[0007] The electromagnetic field data is processed using the time-frequency spectrum analysis method. Through time-frequency decomposition, the distribution characteristics of the electromagnetic field signals caused by the waves at different times and frequencies are identified, so as to accurately extract the period and time-varying characteristics of the waves.

[0008] Step S20, extraction of electromagnetic field induced by ocean waves:

[0009] Using main frequency analysis and bandpass filtering technology, the electromagnetic field data is preprocessed to filter out noise interference and obtain the time domain data of the wave-induced magnetic field.

[0010] Step S30, analysis of wave motion direction and time-varying characteristics:

[0011] Combining the time domain and frequency domain induced electromagnetic field polarization direction analysis technology, the direction of wave movement and its characteristics of change over time can be inferred by measuring the change of the electromagnetic field polarization direction;

[0012] Step S40, wave height estimation:

[0013] Establish a quantitative relationship between the intensity of the wave-induced electromagnetic field and the wave height. By measuring the intensity of the wave-induced electromagnetic field in a specific sea area, the change in wave height in that area can be effectively estimated.

[0014] Furthermore, before step S10, step S00 is also included to correct the electromagnetic field data observed in the ocean:

[0015] The correction methods include gain correction and magnetic field sensitivity correction; by comparing the difference between the actual measured value and the theoretical value, the gain factor of each channel or time period is calculated, and these gain factors are used to adjust the original observation data; the magnetic field sensitivity correction measures the instrument's response under different magnetic field strengths, calculates the instrument's magnetic field sensitivity factor, and uses these factors to convert the voltage signal into the actual magnetic field strength value.

[0016] Furthermore, between step S00 and step S10, step S01 is also included, collecting device posture correction to obtain a corrected electromagnetic field:

[0017] First, we need to obtain the real-time azimuth θ, inclination α and roll angle β from the acquisition device; based on the acquired attitude parameters, we construct the corresponding rotation matrix R θ , R α and R β ; The observed electromagnetic field B' and the electromagnetic field B after attitude correction satisfy the following relationship, and the corrected electromagnetic field B is obtained by solving the following equation:

[0018]

[0019] Furthermore, in step S10, the specific method of extracting the wave period and time-varying features includes:

[0020] The corrected electromagnetic field data is deeply analyzed and subdivided into multiple time windows. Through segmented processing, the subtle characteristics of the electromagnetic field changing with time are accurately captured. For the data in each time window, Fourier transform is used to convert it from the time domain to the frequency domain. In the frequency domain, the amplitude spectrum curve of each time window is plotted. By recording the wave frequency in each time window, a complete time series is constructed, which records in detail the dynamic changes of the wave cycle during the entire observation period.

[0021] Further, in step S30, the method for obtaining the wave movement direction includes:

[0022] The polarization direction of the wave-induced magnetic field is perpendicular to the wave motion direction. Therefore, the wave motion direction is obtained by obtaining the polarization direction of the wave magnetic field. The wave motion direction is determined by two methods, namely, the time domain method and the frequency domain method.

[0023] For the time domain ocean wave electromagnetic data, it is subdivided into multiple time windows, and for each time window, the least squares fitting method is used to fit the linear formula:

[0024] B x (t i )=k*B y (t i )+b

[0025] Among them B x is the north-south component of the magnetic field, B y is the east-west component of the magnetic field, t i are different moments, k is the slope, and b is the slope distance;

[0026] Obtain the slope k by linear fitting and calculate the 90-atan -1 (k)*180 / pi to obtain the polarization direction of the induced magnetic field, where atan -1 (k) is the inverse tangent of the slope k, and pi is the circumference of a circle. At the same time, for each time window, B y With the component as the horizontal axis, B x Component as the ordinate, plot B x and B y The time domain scatter plot identifies the polarization direction of the induced magnetic field according to the long axis direction of the induced magnetic field polarization; the magnetic field polarization direction ±90° is the wave movement direction; by recording the seawater movement direction in each time window, a complete time series can be constructed, which records in detail the dynamic changes of the wave movement direction during the entire observation period;

[0027] For the frequency domain method, it is subdivided into multiple time windows, and the amplitude of the frequency domain wave-induced magnetic field is calculated for each time window. and Where f is the main frequency of the wave-induced magnetic field. For each time window, the rotation angle γ is changed in small steps. The range of γ is 0 to 180°. For each γ, the wave-induced magnetic field value of each window is calculated. Find the γ that maximizes the above value, and record this angle as the polarization direction of the wave-induced magnetic field; the magnetic field polarization direction ±90° is the wave movement direction; by recording the direction of seawater movement in each time window, a complete time series is constructed, which records in detail the dynamic changes of the wave movement direction during the entire observation period.

[0028] Further, in step S40, the method for establishing a quantitative relationship between the intensity of the wave-induced electromagnetic field and the wave height includes: subdividing the frequency-domain wave-induced electromagnetic field data into a plurality of time windows, and calculating the amplitude of the frequency-domain wave-induced magnetic field for each time window. and Calculate the wave-induced magnetic field value for each window Construct a complete time series; obtain the wave height data of the study area at that time through actual measurement or model simulation, fit the wave induced magnetic field with the wave height data, and obtain the fitting empirical formula.

[0029] The present invention discloses a method for analyzing ocean wave characteristics based on electromagnetic field observation data, which has the following beneficial effects:

[0030] The present invention makes full use of the strong energy of the electromagnetic field induced by the waves, turns the noise in the ocean electromagnetic detection into treasure, and realizes the extraction of ocean wave characteristics. It does not need to rely on traditional physical equipment, reduces the monitoring cost, and improves the efficiency of ocean wave monitoring; the ocean electromagnetic field data is easy to collect remotely and is suitable for continuous monitoring of vast sea areas; it provides new data support and analysis tools for research in the fields of ocean wave dynamics, ocean electromagnetism, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a flow chart of the method for analyzing ocean wave characteristics based on electromagnetic field observation data of the present invention;

[0032] Figure 2 It is a schematic diagram of the spectrum of the induced magnetic field of waves and the main frequency of waves measured in a certain sea area of ​​the present invention;

[0033] Figure 3 Schematic diagram of the measured magnetic field time domain polarization direction (blue) and wave direction (red) of the present invention;

[0034] Figure 4 This is a schematic diagram of the change of the wave motion direction over time in the present invention;

[0035] Figure 5 It is a schematic diagram comparing the wave height inferred from the wave induced magnetic field and the simulated wave height according to the present invention. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution 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. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] refer to Figure 1 The present invention discloses a method for analyzing ocean wave characteristics based on electromagnetic field observation data, comprising the following steps:

[0038] Step S10, extraction of wave period and time-varying features:

[0039] The electromagnetic field data is processed by time-frequency spectrum analysis method. Through time-frequency decomposition, the distribution characteristics of electromagnetic field signals caused by ocean waves at different times and frequencies are identified, so as to accurately extract the period and time-varying characteristics of ocean waves. The dynamic changes of the ocean wave period (or frequency) within the observation period are obtained, and the ocean wave induced magnetic field is extracted by bandpass filtering each window, and the frequency domain data is obtained by inverse Fourier transforming the ocean wave induced magnetic field time domain data.

[0040] Step S20, extraction of electromagnetic field induced by ocean waves:

[0041] Using main frequency analysis and bandpass filtering technology, the electromagnetic field data is preprocessed to filter out noise interference, obtain the time domain data of the wave-induced magnetic field, highlight the signal components of the wave-induced electromagnetic field, and ensure the accuracy of subsequent analysis;

[0042] Step S30, analysis of wave motion direction and time-varying characteristics:

[0043] Combining the time domain and frequency domain induced electromagnetic field polarization direction analysis technology, the direction of wave movement and its characteristics of change over time can be inferred by measuring the change of the electromagnetic field polarization direction;

[0044] Step S40, wave height estimation:

[0045] Innovatively proposed a mathematical relationship formula between the wave-induced electromagnetic field and the wave height in a specific sea area. Established a quantitative relationship between the wave-induced electromagnetic field intensity and the wave height, and effectively estimated the wave height change in that area by measuring the wave-induced electromagnetic field intensity in a specific sea area.

[0046] To further optimize the technical solution, since the electromagnetic field observed in the ocean is recorded in a certain format in the form of voltage, it needs to be decoded. Before step S10, step S00 is also included to correct the electromagnetic field data observed in the ocean:

[0047] The correction methods include gain correction and magnetic field sensitivity correction; by comparing the difference between the actual measured value and the theoretical value, the gain factor of each channel or time period is calculated, and these gain factors are used to adjust the original observation data; the magnetic field sensitivity correction measures the instrument's response under different magnetic field strengths, calculates the instrument's magnetic field sensitivity factor, and uses these factors to convert the voltage signal into the actual magnetic field strength value.

[0048] The technical solution is further optimized, and between step S00 and step S10, step S01 is further included, wherein the posture of the acquisition device is corrected to obtain the corrected electromagnetic field:

[0049] In the observation of marine electromagnetic fields, the azimuth θ, inclination α and roll angle β of the acquisition device are the key parameters to describe its spatial attitude. Because the measured value of the electromagnetic field will be affected by the attitude of the device, in order to extract the true horizontal electromagnetic field component from the measurement data, the collected observation electromagnetic field B' needs to be attitude corrected. First, it is necessary to obtain the real-time azimuth θ, inclination α and roll angle β from the acquisition device; according to the acquired attitude parameters, the corresponding rotation matrix R is constructed. θ , R α and R β ; The observed electromagnetic field B' and the electromagnetic field B after attitude correction satisfy the following relationship, and the corrected electromagnetic field B is obtained by solving the following equation:

[0050]

[0051] To further optimize the technical solution, in step S10, the specific method for extracting the wave period and time-varying features includes:

[0052] The corrected electromagnetic field data is analyzed in depth and subdivided into multiple time windows. Through segmented processing, the subtle characteristics of the electromagnetic field changing over time are accurately captured; for the data in each time window, Fourier transform is used to convert it from the time domain to the frequency domain; in the frequency domain, the amplitude spectrum curve of each time window is plotted; the signal changes in the frequency band of 0.1 to 0.3 Hz are often closely related to the activity of the waves. In order to accurately identify the frequency characteristics of the waves, special attention is paid to the amplitude extremes in this frequency band. These extremes represent the local maximum value of the signal energy in this frequency band, and the frequency corresponding to the peak value is the dominant frequency of the waves in this time period. By recording the wave frequency in each time window, a complete time series is constructed, which records in detail the dynamic changes of the wave cycle (or frequency) during the entire observation period.

[0053] To further optimize the technical solution, in step S30, the method for obtaining the direction of wave movement includes:

[0054] The polarization direction of the wave-induced magnetic field is perpendicular to the wave motion direction. Therefore, the wave motion direction is obtained by obtaining the polarization direction of the wave magnetic field. The wave motion direction is determined by two methods, namely, the time domain method and the frequency domain method.

[0055] For the time domain ocean wave electromagnetic data, it is subdivided into multiple time windows, and for each time window, the least squares fitting method is used to fit the linear formula:

[0056] B x (t i )=k*B y (t i )+b

[0057] Among them B x is the north-south component of the magnetic field, B y is the east-west component of the magnetic field, t i are different moments, k is the slope, and b is the slope distance;

[0058] Obtain the slope k by linear fitting and calculate the 90-atan -1 (k)*180 / pi to obtain the polarization direction of the induced magnetic field, where atan -1 (k) is the inverse tangent of the slope k, and pi is the circumference of a circle. At the same time, for each time window, B y With the component as the horizontal axis, B x Component as the ordinate, plot B x and B y The time domain scatter plot identifies the polarization direction of the induced magnetic field according to the long axis direction of the induced magnetic field polarization; the magnetic field polarization direction ±90° is the wave movement direction; by recording the seawater movement direction in each time window, a complete time series can be constructed, which records in detail the dynamic changes of the wave movement direction during the entire observation period;

[0059] For the frequency domain method, it is subdivided into multiple time windows, and the amplitude of the frequency domain wave-induced magnetic field is calculated for each time window. and Where f is the main frequency of the wave-induced magnetic field. For each time window, the rotation angle γ is changed in a small step (such as 1°). The range of γ is 0 to 180°. For each γ, the wave-induced magnetic field value of each window is calculated. Find the γ that maximizes the above value, and record this angle as the polarization direction of the wave-induced magnetic field; the magnetic field polarization direction ±90° is the wave movement direction; by recording the direction of seawater movement in each time window, a complete time series is constructed, which records in detail the dynamic changes of the wave movement direction during the entire observation period.

[0060] To further optimize the technical solution, in step S40, the method for establishing a quantitative relationship between the intensity of the wave-induced electromagnetic field and the wave height includes: for the frequency domain wave-induced electromagnetic field data, subdividing it into multiple time windows, and calculating the amplitude of the frequency domain wave-induced magnetic field for each time window and Calculate the wave-induced magnetic field value for each window Construct a complete time series; obtain the wave height data of the study area at that time through actual measurement or model simulation, fit the wave induced magnetic field with the wave height data, and obtain a fitting empirical formula, which can be used for wave height prediction in adjacent sea areas and time. In this embodiment, the fitting empirical formula is as follows:

[0061] log10(B)=k*Hb

[0062] Among them, B is the observed magnetic field, H is the wave height, k is the slope, and b is the slant distance.

[0063] The present invention makes full use of the strong energy of the electromagnetic field induced by the waves, turns the noise in the ocean electromagnetic detection into treasure, and realizes the extraction of ocean wave characteristics. It does not need to rely on traditional physical equipment, reduces the monitoring cost, and improves the efficiency of ocean wave monitoring; the ocean electromagnetic field data is easy to collect remotely and is suitable for continuous monitoring of vast sea areas; it provides new data support and analysis tools for research in the fields of ocean wave dynamics, ocean electromagnetism, etc.

[0064] Example:

[0065] Take a certain sea area in my country as an example. The water depth in this sea area is 21m. An electromagnetic acquisition station is deployed on the seabed. Due to the shallow sea water, the seabed electromagnetic acquisition station can obviously collect the electromagnetic field induced by the waves. First, the collected data is decoded. Gain correction eliminates the error caused by inconsistent instrument or circuit gain. Magnetic field sensitivity correction requires converting the gain-corrected voltage signal into the actual magnetic field strength value. Then the attitude of the acquisition device is corrected. The attitude of the acquisition device has been obtained through the attitude recorder of the acquisition device, so it can be substituted into step 2 to obtain the corrected horizontal electromagnetic field.

[0066] The wave cycle is further extracted from the decoded and corrected electromagnetic field data. The data is subdivided into 1h time windows to more accurately capture the subtle characteristics of the electromagnetic field over time. The amplitude spectrum curve of each time window is plotted. These curves intuitively show the distribution of electromagnetic field energy with frequency and provide important information about the spectral characteristics of the signal. The spectral characteristics of the wave-induced electromagnetic field are particularly unique, and its bandwidth is mainly concentrated in a narrow range of 0.1 to 0.3Hz. Signal changes in this frequency band are often closely related to the activity of waves. In order to accurately identify the frequency characteristics of waves, special attention is paid to the amplitude extremes in this frequency band. These extremes represent the local maximum value of the signal energy in this frequency band, and the frequency corresponding to the peak value is the dominant frequency of the waves in this time period. Figure 2 a shows the amplitude spectra of three time windows, showing an obvious bulge at 0.1-0.2 Hz. The curves of other time periods are similar to those shown, except that the bulge frequency is slightly shifted. From the three windows shown, it can be identified that the main frequencies of the waves are 0.1198 Hz, 0.1305 Hz, and 0.1408 Hz, respectively, indicating that the frequency (inverse of the period) of the waves gradually increases over time. In this way, by recording the frequency of the waves in each time window, a complete time series can be constructed, which records in detail the dynamic changes of the wave period (or frequency) during the entire observation period, such as Figure 2 As shown in b. Therefore, through the wave-induced magnetic field, it is obtained that the wave frequency in this sea area gradually increases from 0.11 Hz to 0.15 Hz over time, that is, the wave period gradually decreases from 9.1 s to 6.7 s.

[0067] From the previous step, the period of the wave-induced magnetic field is 0.11-0.15 Hz. Bandpass filtering is performed on each window to extract the wave-induced magnetic field, and the wave-induced magnetic field can be separated from all magnetic field data. According to the previous description, the polarization direction (direction of wave movement) of the wave-induced electromagnetic field is obtained from the time domain and frequency domain methods respectively. For the time domain data, linear fitting is performed on the north-south component Bx and the east-west component By according to step five, and the time domain scatter plots of Bx and By are drawn at the same time. The polarization direction of the induced magnetic field is identified according to the long axis direction of the induced magnetic field polarization. Figure 3 The scatter plot and fitted straight line drawn in a certain time window show that the two magnetic field directions have obvious polarization directions. The polarization direction of the magnetic field is ~60° (or 240°). Since the polarization direction of the magnetic field is perpendicular to the direction of wave movement, the direction of wave movement is 150° (or 330°). By recording the direction of seawater movement in each time window, a complete time series can be constructed. This series records in detail the dynamic changes of the wave movement direction during the entire observation period, such as Figure 4As shown, the direction of wave movement is not constant over time, and the range of change is 130~170°. It can be seen that the direction of wave movement changes significantly over time.

[0068] Further determine the relationship between the effective wave height and the wave induced electromagnetic field, so as to achieve the purpose of predicting the wave height from the electromagnetic field data. Process the data according to step six. Figure 5 The red thick line is the wave induced magnetic field B obtained by station 1, and the red dotted line is the simulated effective wave height data H. The relationship between the two is log 10 (B) = 1.2753H-2.3757. This shows that the logarithmic domain value of the wave induced magnetic field amplitude is linearly related to the effective wave height of the waves. This relationship is used to predict the magnetic field observed by another station 2 in the sea area. The distance between station 2 and station 1 is 3km. The results show that the wave height predicted by this relationship (gray thick line) has a good correspondence with the simulated wave height (black dotted line), indicating that the empirical formula is suitable for this sea area. Therefore, this empirical formula can be used to predict wave heights in adjacent sea areas and within time.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for analyzing ocean wave characteristics based on electromagnetic field observation data, characterized in that: The steps include: Step S10, extraction of wave period and time-varying features: The electromagnetic field data is processed using the time-frequency spectrum analysis method. Through time-frequency decomposition, the distribution characteristics of the electromagnetic field signals caused by the waves at different times and frequencies are identified, so as to accurately extract the period and time-varying characteristics of the waves. Step S20, extraction of electromagnetic field induced by ocean waves: Using main frequency analysis and bandpass filtering technology, the electromagnetic field data is preprocessed to filter out noise interference and obtain the time domain data of the wave-induced magnetic field. Step S30, analysis of wave motion direction and time-varying characteristics: Combining the time domain and frequency domain induced electromagnetic field polarization direction analysis technology, the direction of wave movement and its characteristics of change over time can be inferred by measuring the change of the electromagnetic field polarization direction; Step S40, wave height estimation: Establish a quantitative relationship between the intensity of the wave-induced electromagnetic field and the wave height. By measuring the intensity of the wave-induced electromagnetic field in a specific sea area, the change in wave height in that area can be effectively estimated.

2. The method for analyzing ocean wave characteristics based on electromagnetic field observation data according to claim 1, characterized in that: Before step S10, the method further includes step S00, in which the electromagnetic field data observed in the ocean are corrected: The correction methods include gain correction and magnetic field sensitivity correction; by comparing the difference between the actual measured value and the theoretical value, the gain factor of each channel or time period is calculated, and these gain factors are used to adjust the original observation data; the magnetic field sensitivity correction measures the instrument's response under different magnetic field strengths, calculates the instrument's magnetic field sensitivity factor, and uses these factors to convert the voltage signal into the actual magnetic field strength value.

3. The method for analyzing ocean wave characteristics based on electromagnetic field observation data according to claim 2, characterized in that: Between step S00 and step S10, step S01 is also included, collecting device posture correction to obtain a corrected electromagnetic field: First, we need to obtain the real-time azimuth θ, inclination α and roll angle β from the acquisition device; based on the acquired attitude parameters, we construct the corresponding rotation matrix R θ , R α and R β ; The observed electromagnetic field B' and the electromagnetic field B after attitude correction satisfy the following relationship, and the corrected electromagnetic field B is obtained by solving the following equation:

4. The method for analyzing ocean wave characteristics based on electromagnetic field observation data according to claim 3, characterized in that: In step S10, the specific method of extracting the wave period and time-varying features includes: The corrected electromagnetic field data is deeply analyzed and subdivided into multiple time windows. Through segmented processing, the subtle characteristics of the electromagnetic field changing with time are accurately captured. For the data in each time window, Fourier transform is used to convert it from the time domain to the frequency domain. In the frequency domain, the amplitude spectrum curve of each time window is plotted. By recording the wave frequency in each time window, a complete time series is constructed, which records in detail the dynamic changes of the wave cycle during the entire observation period.

5. The method for analyzing ocean wave characteristics based on electromagnetic field observation data according to claim 4, characterized in that: In step S30, the method for obtaining the wave movement direction includes: The polarization direction of the wave-induced magnetic field is perpendicular to the wave motion direction. Therefore, the wave motion direction is obtained by obtaining the polarization direction of the wave magnetic field. The wave motion direction is determined by two methods, namely, the time domain method and the frequency domain method. For the time domain ocean wave electromagnetic data, it is subdivided into multiple time windows, and for each time window, the least squares fitting method is used to fit the linear formula: B x (t i )=k*B y (t i )+b Among them B x is the north-south component of the magnetic field, B y is the east-west component of the magnetic field, t i are different moments, k is the slope, and b is the slope distance; Obtain the slope k by linear fitting and calculate the 90-atan -1 (k)*180 / pi to obtain the polarization direction of the induced magnetic field, where atan -1 (k) is the inverse tangent of the slope k, and pi is the circumference of a circle. At the same time, for each time window, B y With the component as the horizontal axis, B x Component as the ordinate, plot B x and B y The time domain scatter plot identifies the polarization direction of the induced magnetic field according to the long axis direction of the induced magnetic field polarization; the magnetic field polarization direction ±90° is the wave movement direction; by recording the seawater movement direction in each time window, a complete time series can be constructed, which records in detail the dynamic changes of the wave movement direction during the entire observation period; For the frequency domain method, it is subdivided into multiple time windows, and the amplitude of the frequency domain wave-induced magnetic field is calculated for each time window. and Where f is the main frequency of the wave-induced magnetic field. For each time window, the rotation angle γ is changed in small steps. The range of γ is 0 to 180°. For each γ, the wave-induced magnetic field value of each window is calculated. Find the γ that maximizes the above value, and record this angle as the polarization direction of the wave-induced magnetic field; the magnetic field polarization direction ±90° is the wave movement direction; by recording the direction of seawater movement in each time window, a complete time series is constructed, which records in detail the dynamic changes of the wave movement direction during the entire observation period.

6. The method for analyzing ocean wave characteristics based on electromagnetic field observation data according to claim 5, characterized in that: In step S40, the method for establishing a quantitative relationship between the intensity of the wave-induced electromagnetic field and the wave height includes: subdividing the frequency-domain wave-induced electromagnetic field data into multiple time windows, and calculating the amplitude of the frequency-domain wave-induced magnetic field for each time window. and Calculate the wave-induced magnetic field value for each window Construct a complete time series; obtain the wave height data of the study area at that time through actual measurement or model simulation, fit the wave induced magnetic field with the wave height data, and obtain the fitting empirical formula.

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