Ocean wave characteristics analysis method based on electromagnetic field observation data

Abstract

The present invention discloses a method for analyzing ocean wave characteristics based on electromagnetic field observation data. The method comprises the following steps: processing the electromagnetic field data using a time-frequency spectrum analysis method, identifying the distribution characteristics of the electromagnetic field signals caused by the ocean waves at different times and frequencies through time-frequency decomposition, and extracting the period and time-varying characteristics of the ocean waves; preprocessing the electromagnetic field data using dominant frequency analysis and bandpass filtering techniques to obtain time-domain data of the ocean wave-induced magnetic field; combining time-domain and frequency-domain induced electromagnetic field polarization direction analysis techniques to infer the direction of ocean wave motion and its temporal variation characteristics by measuring changes in the electromagnetic field polarization direction; establishing a quantitative relationship between the intensity of the ocean wave-induced electromagnetic field and the wave height, and effectively estimating the wave height variation in the area based on the intensity of the ocean wave-induced electromagnetic field. By comprehensively analyzing the electromagnetic field data, the present invention enables the assessment of the period, time-varying characteristics, direction of motion, and wave height of the ocean waves, providing a new approach for marine environmental 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 rely heavily on equipment such as buoys and radar, but these methods suffer from high deployment costs, complex maintenance, and limited coverage. Marine electromagnetic technology is a commonly used detection technique in marine geophysics. A common method involves placing electromagnetic recorders on the seafloor or water column to record active or natural source signals propagating through the water column and seafloor, thereby enabling the detection of subsurface geological structures. However, because seawater is a good conductor, its movement cuts through the geomagnetic field, generating induced electromagnetic fields. These fields are recorded by electromagnetic recorders in the water column or seafloor, adding noise to the geophysical detection signals. The impact of waves is particularly pronounced in shallow water, where the energy of the induced electromagnetic fields far exceeds that of natural electromagnetic fields. However, wave-induced electromagnetic fields, generated by wave motion, carry characteristic wave information, such as period, direction, and wave height. In recent years, research on using wave-induced electromagnetic fields for wave monitoring has gained momentum. However, accurately and efficiently extracting wave characteristic parameters (such as period, wave height, and direction) and establishing a quantitative relationship between these parameters and the wave-induced electromagnetic field remain technical challenges. 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 electromagnetic field data, it can realize the evaluation of 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 solutions:

[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 time-frequency spectrum analysis. Through time-frequency decomposition, the distribution characteristics of the electromagnetic field signals caused by ocean waves at different times and frequencies are identified, thereby accurately extracting the periodic and temporal characteristics of the ocean waves.

[0008] Step S20: Extracting the electromagnetic field induced by ocean waves:

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

[0010] Step S30: Analysis of the direction and time-varying characteristics of the wave motion:

[0011] Combining the time domain and frequency domain induced electromagnetic field polarization direction analysis technology, by measuring the changes in the electromagnetic field polarization direction, the direction of wave movement and its temporal variation characteristics are inferred;

[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, effectively estimate the changes in the wave height in that area.

[0014] Furthermore, before step S10, the method further includes step S00 of correcting the electromagnetic field data observed in the ocean:

[0015] 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; magnetic field sensitivity correction measures the instrument's response under different magnetic field intensities, calculates the instrument's magnetic field sensitivity factor, and uses these factors to convert the voltage signal into the actual magnetic field intensity value.

[0016] Furthermore, between step S00 and step S10, step S01 is further included, wherein the posture of the acquisition device is corrected to obtain a corrected electromagnetic field:

[0017] First, we need to obtain the real-time orientation θ, tilt α and roll β from the acquisition device; according to 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. The corrected electromagnetic field B is obtained by solving the following equation:

[0018]

[0019] Furthermore, in step S10, the specific method for 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 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. 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] Furthermore, in step S30, the method for obtaining the direction of wave movement 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: 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. 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 arc 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 coordinate, B x Component is the vertical axis, plot B x and B y The time domain scatter plot identifies the polarization direction of the induced magnetic field based on the long axis direction of the induced magnetic field polarization; the magnetic field polarization direction ±90° is defined as the wave movement direction; by recording the direction of seawater movement within each time window, a complete time series can be constructed, which records in detail the dynamic changes in 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 in the wave movement direction during the entire observation period.

[0028] Furthermore, in step S40, the method for establishing a quantitative relationship between the intensity of the ocean wave induced electromagnetic field and the ocean wave height includes: subdividing the frequency domain ocean wave induced electromagnetic field data into multiple time windows, and calculating the amplitude of the frequency domain ocean wave induced magnetic field for each time window. and Calculate the wave-induced magnetic field value of 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] This method fully utilizes the strong energy of the wave-induced electromagnetic field, transforming noise from ocean electromagnetic detection into valuable insights, enabling the extraction of wave characteristics. This eliminates the need for traditional physical equipment, reducing monitoring costs and improving wave monitoring efficiency. Ocean electromagnetic field data can be easily collected remotely, making it suitable for continuous monitoring over vast ocean areas. This provides new data support and analytical tools for research in fields such as wave dynamics and ocean electromagnetism. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0033] Figure 3 Schematic diagram of the time-domain polarization direction (blue) and wave direction (red) of the measured magnetic field 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 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] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments 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 shall fall 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 using a time-frequency spectrum analysis method. Through time-frequency decomposition, the distribution characteristics of the electromagnetic field signals caused by ocean waves at different times and frequencies are identified, thereby accurately extracting the period and time-varying characteristics of the 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. The frequency domain data is then subjected to an inverse Fourier transform to obtain the time domain data of the ocean wave-induced magnetic field.

[0040] Step S20: Extracting the electromagnetic field induced by ocean waves:

[0041] Using main frequency analysis and bandpass filtering technology, the electromagnetic field data is pre-processed 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 the direction and time-varying characteristics of the wave motion:

[0043] Combining the time domain and frequency domain induced electromagnetic field polarization direction analysis technology, by measuring the changes in the electromagnetic field polarization direction, the direction of wave movement and its temporal variation characteristics are inferred;

[0044] Step S40, wave height estimation:

[0045] An innovative mathematical formula is proposed to link the wave-induced electromagnetic field (EMF) in a specific sea area with the wave height. This quantitative relationship is established, and by measuring the EMF intensity in a specific sea area, the wave height variation in that area can be effectively estimated.

[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 further included to correct the electromagnetic field data observed in the ocean:

[0047] 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; magnetic field sensitivity correction measures the instrument's response under different magnetic field intensities, calculates the instrument's magnetic field sensitivity factor, and uses these factors to convert the voltage signal into the actual magnetic field intensity 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 a corrected electromagnetic field:

[0049] In ocean electromagnetic field observation, the azimuth θ, inclination α, and roll angle β of the acquisition device are 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; based on 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. 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 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 of the signal energy in this frequency band, and the frequency corresponding to the peak 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 period (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: 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. 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 arc 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 coordinate, B x Component is the vertical axis, plot B x and B y The time domain scatter plot identifies the polarization direction of the induced magnetic field based on the long axis direction of the induced magnetic field polarization; the magnetic field polarization direction ±90° is defined as the wave movement direction; by recording the direction of seawater movement within each time window, a complete time series can be constructed, which records in detail the dynamic changes in 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 in the wave movement direction during the entire observation period.

[0060] Further optimizing 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: 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 of 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. This fitting empirical formula can be used to predict the wave height 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] This method fully utilizes the strong energy of the wave-induced electromagnetic field, transforming noise from ocean electromagnetic detection into valuable insights, enabling the extraction of wave characteristics. This eliminates the need for traditional physical equipment, reducing monitoring costs and improving wave monitoring efficiency. Ocean electromagnetic field data can be easily collected remotely, making it suitable for continuous monitoring over vast ocean areas. This provides new data support and analytical tools for research in fields such as wave dynamics and ocean electromagnetism.

[0064] Example:

[0065] For example, let's take a specific sea area in my country, located at a depth of 21 meters. An electromagnetic data acquisition station is deployed on the seafloor. Due to the shallow waters, the station can clearly detect the wave-induced electromagnetic field. First, the collected data is decoded. Gain correction eliminates errors caused by inconsistent instrument or circuit gain. Magnetic field sensitivity correction converts the gain-corrected voltage signal into an actual magnetic field strength value. Next, the data acquisition device's attitude is corrected. The device's attitude is recorded using its attitude recorder, so this data is substituted into step two to obtain the corrected horizontal electromagnetic field.

[0066] The wave period is further extracted from the decoded and corrected electromagnetic field data. The data is subdivided into 1-hour 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 signal spectrum characteristics. 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 0.3 Hz. Signal changes in this frequency band are often closely related to wave activity. 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 of the signal energy in this frequency band, and the frequency corresponding to the peak is the dominant frequency of the waves in this time period. Figure 2 Figure a shows the amplitude spectra of three time windows, showing a clear bulge at 0.1-0.2 Hz. The curves for other time periods are similar to those shown, except that the bulge has a slight shift in frequency. From the three windows shown, we can identify the dominant frequencies of the waves as 0.1198 Hz, 0.1305 Hz, and 0.1408 Hz, respectively. This indicates that the frequency (the inverse of the period) of the waves gradually increases over time. In this way, by recording the wave frequency in each time window, we can construct a complete time series that records in detail the dynamic changes of the wave period (or frequency) during the entire observation period, as shown in Figure 3. Figure 2 As shown in Figure b, the wave frequency in this sea area gradually increases from 0.11 Hz to 0.15 Hz over time through the wave-induced magnetic field, that is, the wave period gradually decreases from 9.1 s to 6.7 s.

[0067] The period of the wave-induced magnetic field, obtained from the previous step, is 0.11 to 0.15 Hz. Bandpass filtering is performed on each window to extract the wave-induced magnetic field, which can be separated from all magnetic field data. According to the previous description, the polarization direction (direction of wave motion) of the wave-induced electromagnetic field is obtained using time domain and frequency domain methods. For the time domain data, linear fitting is performed on the north-south component Bx and the east-west component By according to step 5. Time domain scatter plots of Bx and By are also plotted. The polarization direction of the induced magnetic field is identified based on the long axis direction of the induced magnetic field. Figure 3 The scatter plot and fitted straight line drawn for 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 in the figure, the direction of wave movement is not constant over time, and the range of change is 130 to 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, thereby achieving the goal of predicting wave height from electromagnetic field data. Process the data according to step 6. Figure 5 The thick red line represents the wave-induced magnetic field B obtained at station 1, and the dotted red line represents the simulated significant wave height data H. The relationship between the two is log 10(B) = 1.2753H - 2.3757. This indicates that the logarithmic domain value of the wave-induced magnetic field amplitude is linearly related to the significant wave height. This relationship was applied to predict the magnetic field observed at another station, station 2, in the same sea area. The distance between station 2 and station 1 is 3 km. The results show that the wave height predicted using this relationship (thick gray line) corresponds well to the simulated wave height (dotted black 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 a certain timeframe.

[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 various 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, extracting the wave period and time-varying features: The electromagnetic field data is processed using time-frequency spectrum analysis. Through time-frequency decomposition, the distribution characteristics of the electromagnetic field signals caused by ocean waves at different times and frequencies are identified, thereby accurately extracting the periodic and temporal characteristics of the ocean waves. Step S20: Extracting the electromagnetic field induced by ocean waves: Using main frequency analysis and bandpass filtering technology, the electromagnetic field data is pre-processed to filter out noise interference and obtain the time domain data of the wave-induced electromagnetic field; Step S30: Analysis of the direction and time-varying characteristics of the wave motion: Combining the time domain and frequency domain induced electromagnetic field polarization direction analysis technology, by measuring the changes in the electromagnetic field polarization direction, the direction of wave movement and its temporal variation characteristics are inferred; Step S40, wave height estimation: Establish a quantitative relationship between the intensity of the electromagnetic field induced by waves and the wave height. By measuring the intensity of the electromagnetic field induced by waves in a specific sea area, the change of the wave height in the specific sea area can be effectively estimated. In step S30, the method for obtaining the direction of wave movement 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: the time domain method and the frequency domain method. For the time domain ocean wave electromagnetic data, it is subdivided into multiple time windows. 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; The slope k is obtained by linear fitting, and the polarization direction of the induced magnetic field is obtained by calculating 90-arctan(k)*180 / pi, where arctan(k) is the inverse tangent of the slope k and pi is the circumference of the circle. At the same time, for each time window, B y With the component as the horizontal coordinate, B x Component is the vertical axis, plot B x and B y The time domain scatter plot identifies the polarization direction of the induced magnetic field based on the long axis direction of the induced magnetic field polarization; the magnetic field polarization direction ±90° is defined as the wave movement direction; by recording the direction of seawater movement within each time window, a complete time series can be constructed, which records in detail the dynamic changes in 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 in the wave movement direction during the entire observation period.

2. The ocean wave characteristic analysis method based on electromagnetic field observation data according to claim 1, characterized in that: Before step S10, the method further includes step S00 of correcting the electromagnetic field data observed in the ocean: 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 intensities, calculates the instrument's magnetic field sensitivity factor, and uses the magnetic field sensitivity factor to convert the voltage signal into the actual magnetic field intensity value.

3. The ocean wave characteristic analysis method based on electromagnetic field observation data according to claim 2, characterized in that: Between step S00 and step S10, step S01 is also included, wherein the posture of the acquisition device is corrected to obtain the corrected electromagnetic field: First, we need to obtain the real-time orientation θ, tilt α and roll β from the acquisition device; according to 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. The corrected electromagnetic field B is obtained by solving the following equation:

4. The ocean wave characteristic analysis method based on electromagnetic field observation data according to claim 3, characterized in that: In step S10, the specific method for 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 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. 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 S40, the method for establishing a quantitative relationship between the intensity of the ocean wave induced electromagnetic field and the wave height includes: subdividing the frequency domain ocean wave induced electromagnetic field data into multiple time windows, and calculating the amplitude of the frequency domain ocean wave induced magnetic field for each time window. and Calculate the wave-induced magnetic field value of 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.

Images