A method and device for determining a correction coefficient for GNSS-R sea surface oil film detection

Abstract

The embodiment of the application provides a GNSS-R sea surface oil film detection correction coefficient determination method and device. The method comprises the following steps: acquiring GNSS direct signal power and GNSS reflected signal power of a seawater area in a target sea area; determining a left-handed reflectivity observation value based on the GNSS direct signal power and the GNSS reflected signal power; determining a left-handed reflectivity theoretical value according to measured seawater area reference data of the seawater area; and determining a correction coefficient corresponding to the target sea area based on the left-handed reflectivity observation value and the left-handed reflectivity theoretical value, wherein the correction coefficient is used for correcting the dielectric constant of the seawater and the oil film.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of remote sensing data processing, and in particular to a GNSS-R sea surface oil film detection correction coefficient determination method and device. BACKGROUND

[0002] With the continuous deepening of the development of marine oil and gas resources, offshore oil spill accidents as an important source of marine environmental pollution, its negative impact on the ecological system, fishery resources and coastal economy is increasingly prominent. Timely and accurately identifying the location, distribution range and diffusion trend of oil spill is a key technical requirement for effective protection and risk prevention and control of marine environment, and has important ecological and economic significance.

[0003] Compared with optical remote sensing, synthetic aperture radar (SAR) and microwave radiometer, the emerging global navigation satellite reflectometry (GNSS-R) uses the L-band reflected signal of existing navigation satellites (GPS (Global Positioning System), Beidou, etc.), and realizes inversion by analyzing the changes of reflected signal parameters (amplitude, phase, Doppler shift). Its advantages of all-weather, global coverage, low cost and low power consumption make it develop very quickly.

[0004] Most methods are usually based on satellite or airborne platforms, and the few shore-based experimental simulations are not the real situation of sea surface oil spill, that is, the sea surface is covered with thin oil film. When distinguishing oil and water through the dielectric constant of seawater and oil area, the current method only distinguishes them by the difference of dielectric constant values in different areas, without considering the influence of numerical value caused by calibration error, resulting in low accuracy of oil and water distinction. SUMMARY

[0005] The embodiments of the present application provide a GNSS-R sea surface oil film detection correction coefficient determination method and device to solve the problem that only the difference of dielectric constant values in different areas is used for distinction, without considering the influence of numerical value caused by calibration error, resulting in low accuracy of oil and water distinction.

[0006] To solve the above technical problems, the embodiments of the present application are implemented as follows:

[0007] In a first aspect, the embodiments of the present application provide a GNSS-R sea surface oil film detection correction coefficient determination method, which comprises:

[0008] obtaining the GNSS direct signal power and the GNSS reflected signal power of the seawater area in the target sea area;

[0009] determine a left-handed reflectivity observation value based on the GNSS direct signal power and the GNSS reflected signal power;

[0010] determine a left-handed reflectivity theoretical value according to measured seawater region reference data of the seawater region;

[0011] determine a correction coefficient corresponding to the target sea area based on the left-handed reflectivity observation value and the left-handed reflectivity theoretical value, the correction coefficient being used to correct the dielectric constant for distinguishing seawater and oil film.

[0012] Optionally, the GNSS direct signal power and the GNSS reflected signal power of the seawater region in the target sea area are obtained by:

[0013] obtain an initial GNSS direct signal power of a GNSS direct signal emitted by a GNSS satellite to the seawater region in a target period, and an initial GNSS reflected signal power of a GNSS reflected signal corresponding to the GNSS direct signal;

[0014] screen the GNSS direct signal power and the GNSS reflected signal power meeting the conditions from the initial GNSS direct signal power and the initial GNSS reflected signal power.

[0015] Optionally, the left-handed reflectivity observation value is determined based on the GNSS direct signal power and the GNSS reflected signal power, comprising:

[0016] calculate a power ratio between the GNSS reflected signal power and the GNSS direct signal power;

[0017] take the power ratio as the left-handed reflectivity observation value.

[0018] Optionally, the left-handed reflectivity theoretical value is determined according to the measured seawater region reference data of the seawater region, comprising:

[0019] measure seawater temperature and seawater salinity of the seawater region, and take the seawater temperature and the seawater salinity as the seawater region reference data;

[0020] determine the left-handed reflectivity theoretical value based on the seawater temperature and the seawater salinity.

[0021] Optionally, the left-handed reflectivity theoretical value is determined based on the seawater temperature and the seawater salinity, comprising:

[0022] The seawater temperature and the seawater salinity are substituted into a seawater Debye model to obtain a theoretical value of a seawater relative dielectric constant of the seawater area;

[0023] The theoretical value of the seawater relative dielectric constant and an incident angle are substituted into a Fresnel reflection model to obtain the theoretical value of the left-handed reflectivity, the incident angle being an incident angle of a GNSS direct signal corresponding to the GNSS direct signal power.

[0024] Optionally, the correction coefficient corresponding to the target sea area is determined based on the observed value of the left-handed reflectivity and the theoretical value of the left-handed reflectivity, including:

[0025] A ratio between the theoretical value of the left-handed reflectivity and the observed value of the left-handed reflectivity is calculated;

[0026] The ratio is determined as the correction coefficient corresponding to the target sea area.

[0027] Optionally, after the correction coefficient corresponding to the target sea area is determined based on the observed value of the left-handed reflectivity and the theoretical value of the left-handed reflectivity, the method further includes:

[0028] Target GNSS direct signal power and target GNSS reflected signal power of a to-be-measured area of the target sea area are obtained, as well as a corresponding satellite elevation angle;

[0029] Target left-handed reflectivity is determined based on the target GNSS direct signal power and the target GNSS reflected signal power;

[0030] Relative dielectric constant corresponding to the to-be-measured area is determined based on the target left-handed reflectivity, the satellite elevation angle and the correction coefficient;

[0031] An oil film detection result of the to-be-measured area is determined according to the relative dielectric constant.

[0032] Optionally, the relative dielectric constant corresponding to the to-be-measured area is determined based on the target left-handed reflectivity, the satellite elevation angle and the correction coefficient, including:

[0033] The relative dielectric constant is calculated based on the following formula (1):

[0034] (1)

[0035] In the above formula (1), is the relative dielectric constant, is the target left-handed reflectivity, is the satellite elevation angle, is the correction coefficient.

[0036] In a second aspect, the embodiments of the present application provide a device for determining a correction coefficient for GNSS-R sea surface oil film detection, the device comprising:

[0037] a power acquisition module configured to acquire GNSS direct signal power and GNSS reflected signal power of a seawater region in a target sea area;

[0038] an observation value determination module configured to determine a left-handed reflectivity observation value based on the GNSS direct signal power and the GNSS reflected signal power;

[0039] a theoretical value determination module configured to determine a left-handed reflectivity theoretical value according to seawater region reference data of the seawater region;

[0040] a correction coefficient determination module configured to determine a correction coefficient corresponding to the target sea area based on the left-handed reflectivity observation value and the left-handed reflectivity theoretical value, the correction coefficient being used to correct a dielectric constant for distinguishing seawater and oil film.

[0041] Optionally, the power acquisition module comprises:

[0042] an initial power acquisition unit configured to acquire initial GNSS direct signal power of a GNSS direct signal emitted by a GNSS satellite to the seawater region in a target time period and initial GNSS reflected signal power of a GNSS reflected signal corresponding to the GNSS direct signal;

[0043] a power screening unit configured to screen the GNSS direct signal power and the GNSS reflected signal power that meet a condition from the initial GNSS direct signal power and the initial GNSS reflected signal power.

[0044] Optionally, the observation value determination module comprises:

[0045] a power ratio calculation unit configured to calculate a power ratio between the GNSS reflected signal power and the GNSS direct signal power;

[0046] an observation value acquisition unit configured to take the power ratio as the left-handed reflectivity observation value.

[0047] Optionally, the theoretical value determination module comprises:

[0048] a reference data acquisition unit configured to measure seawater temperature and seawater salinity of the seawater region and take the seawater temperature and the seawater salinity as the seawater region reference data;

[0049] a theoretical value determination unit configured to determine the left-handed reflectivity theoretical value based on the seawater temperature and the seawater salinity.

[0050] Optionally, the theoretical value determination unit comprises:

[0051] a dielectric theoretical value acquisition sub-unit, configured to substitute the seawater temperature and the seawater salinity into a seawater Debye model to obtain a seawater relative dielectric constant theoretical value of the seawater area;

[0052] a reflectivity theoretical value acquisition sub-unit, configured to substitute the seawater relative dielectric constant theoretical value and an incident angle into a Fresnel reflection model to obtain the left-handed reflectivity theoretical value, the incident angle being an incident angle of a GNSS direct signal corresponding to the GNSS direct signal power.

[0053] Optionally, the correction coefficient determination module comprises:

[0054] a reflectivity ratio calculation unit, configured to calculate a ratio between the left-handed reflectivity theoretical value and the left-handed reflectivity observed value;

[0055] a correction coefficient determination unit, configured to determine the ratio as a correction coefficient corresponding to the target sea area.

[0056] Optionally, the device further comprises:

[0057] a target power acquisition module, configured to acquire a target GNSS direct signal power and a target GNSS reflected signal power of a to-be-measured area of the target sea area, and a corresponding satellite elevation angle;

[0058] a target reflectivity determination module, configured to determine a target left-handed reflectivity based on the target GNSS direct signal power and the target GNSS reflected signal power;

[0059] a dielectric constant determination module, configured to determine a relative dielectric constant corresponding to the to-be-measured area based on the target left-handed reflectivity, the satellite elevation angle and the correction coefficient;

[0060] a detection result determination module, configured to determine an oil film detection result of the to-be-measured area according to the relative dielectric constant.

[0061] Optionally, the dielectric constant determination module comprises:

[0062] the relative dielectric constant is calculated based on the following formula (1):

[0063] (1)

[0064] In the above formula (1), is the relative dielectric constant, is the target left-handed reflectivity, is the satellite elevation angle, is the correction coefficient.

[0065] In a third aspect, an electronic device is provided, comprising:

[0066] The memory, the processor, and a computer program stored in the memory and executable on the processor, when executed by the processor, implement the GNSS-R sea surface oil film detection correction coefficient determination method of any of the preceding embodiments.

[0067] In a fourth aspect, a readable storage medium is provided, when instructions in the storage medium are executed by a processor of an electronic device, the electronic device can execute the GNSS-R sea surface oil film detection correction coefficient determination method of any of the preceding embodiments.

[0068] In the embodiments of the present application, the correction coefficient is calculated by introducing seawater area reference data to correct the dielectric constant for distinguishing seawater and oil film, so as to effectively reduce the influence of the calibration error, more truly reflect the dielectric constant distribution of the detection area, and improve the accuracy of oil-water differentiation.

[0069] The above description is only a summary of the technical solutions of the present application, in order to more clearly understand the technical means of the present application, and can be implemented according to the content of the specification, and in order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the following specific embodiments of the present application are described. BRIEF DESCRIPTION OF DRAWINGS

[0070] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the description of the embodiments of the present application. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creating laborious work.

[0071] Figure 1 A step flow chart of a GNSS-R sea surface oil film detection correction coefficient determination method provided by the embodiments of the present application;

[0072] Figure 2 A schematic diagram of oil-water left-handed reflectivity changing with elevation angle provided by the embodiments of the present application;

[0073] Figure 3 A histogram of oil-water area dielectric constant probability provided by the embodiments of the present application;

[0074] Figure 4 A structural schematic diagram of a GNSS-R sea surface oil film detection correction coefficient determination device provided by the embodiments of the present application;

[0075] Figure 5A structural schematic diagram of an electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0076] The technical solutions in the embodiments of the present application will be clearly and completely described in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0077] Reference Figure 1 FIG. 1 shows a flowchart of steps of a method for determining a correction coefficient for GNSS-R sea surface oil film detection provided in an embodiment of the present application, as shown in FIG. 1, the method for determining the correction coefficient for GNSS-R sea surface oil film detection can include steps 101, 102, 103 and 104. Figure 1

[0078] Step 101: Obtain GNSS direct signal power and GNSS reflected signal power of a seawater area in a target sea area.

[0079] The embodiments of the present application can be applied to a scenario of calculating a correction coefficient for correcting a dielectric constant for distinguishing seawater and oil film in combination with reference data of the seawater area.

[0080] The target sea area refers to a specific range of sea area for which the correction coefficient calculation is needed. In the present example, the target sea area can be, but is not limited to, an independent geographical unit sea area, such as a certain gulf, a sea area near a certain island group, etc.

[0081] The seawater area refers to an area in the target sea area without oil film coverage.

[0082] The GNSS direct signal power refers to a power value of a signal emitted by a global satellite navigation system (such as GPS, Beidou, etc.) and directly captured by a receiver. The GNSS direct signal power reflects the intensity of the satellite signal after propagation in free space, and is affected by factors such as satellite elevation angle, ionospheric / tropospheric attenuation, etc.

[0083] The GNSS reflected signal power refers to a power value of a GNSS signal reflected by seawater or other media and captured by a receiver. The reflected power is closely related to the dielectric constant, roughness, incident angle, etc. of the seawater or other media, and is a key parameter for remote sensing of the surface characteristics.

[0084] In the calculation of the correction coefficient for the target sea area, the GNSS direct signal power and the GNSS reflected signal power of the seawater area in the target sea area can be obtained. The implementation process can be described in detail in combination with the following specific implementation manners.

[0085] ​In an implementation of the present application, the step 101 can include:

[0086] Sub-step A1: obtaining initial GNSS direct signal power of a GNSS direct signal transmitted by a GNSS satellite to the sea area in a target period, and initial GNSS reflected signal power of a GNSS reflected signal corresponding to the GNSS direct signal.

[0087] In the embodiment, the target period refers to a specific time window preset for collecting GNSS signals.

[0088] The initial GNSS direct signal power refers to an original signal power value of the GNSS direct signal directly transmitted by the GNSS satellite in the target period and captured by the receiver.

[0089] The initial GNSS reflected signal power refers to an original power value of the GNSS reflected signal captured by the receiver after the GNSS signal is reflected by the sea surface.

[0090] In the implementation, a dual-antenna receiving system can be built: 1. A direct antenna, which can be a high-gain right-hand circular polarization (RHCP) antenna, is installed in an unobstructed position (such as the top of the mast) and points to the zenith direction (elevation angle ≥ 5°, etc.), and is used to capture the GNSS direct signal. 2. A reflected antenna, which can be a left-hand circular polarization (LHCP) antenna, is installed on the deck or the buoy platform and points to the target sea area (azimuth angle covers the main reflection area, elevation angle ≤ 45°, etc.), and is used to capture the GNSS reflected signal.

[0091] When the GNSS satellite transmits the GNSS signal to the sea area in the target period, the initial GNSS direct signal power of the GNSS direct signal and the initial GNSS reflected signal power of the GNSS reflected signal corresponding to the GNSS direct signal can be obtained. Specifically, for the GNSS direct signal and the GNSS reflected signal, the satellite signal can be captured by using a C / A code correlator through the processing of a radio frequency front end (low noise amplifier, band pass filter, frequency down converter), analog-to-digital conversion, digital down conversion, etc., the code phase and the carrier phase are calculated, and then the signal power, i.e., the initial GNSS direct signal power and the initial GNSS reflected signal power, can be calculated by using a square law detector.

[0092] After obtaining the initial GNSS direct signal power and the initial GNSS reflected signal power, sub-step A2 is performed.

[0093] Sub-step A2: Select the GNSS direct signal power and the GNSS reflected signal power that meet the conditions from the initial GNSS direct signal power and the initial GNSS reflected signal power.

[0094] After obtaining the initial GNSS direct signal power and the initial GNSS reflected signal power, the GNSS direct signal power and the GNSS reflected signal power that meet the conditions can be selected from the initial GNSS direct signal power and the initial GNSS reflected signal power. For example Figure 2 As shown, the variation of left-handed reflectivity of seawater and oil film with elevation angle is illustrated, where the horizontal axis represents elevation angle (in degrees) and the vertical axis represents left-handed reflectivity. Line 21 represents the curve of left-handed reflectivity of seawater as a function of elevation angle, and line 22 represents the curve of left-handed reflectivity of oil as a function of elevation angle. To obtain accurate correction coefficients, it is necessary to select stable ranges with relatively small variations, such as... Figure 2 As shown, it is necessary to filter out the GNSS direct signal power and GNSS reflected signal power corresponding to the left-handed reflectivity when the elevation angle is greater than 40°. The elevation angle is determined based on the position of the GNSS receiver and the position of the satellite in the sky.

[0095] This application embodiment improves the accuracy of correction coefficient calculation by filtering out GNSS direct signal power and GNSS reflected signal power that meet the conditions for subsequent correction coefficient calculation.

[0096] After obtaining the GNSS direct signal power and GNSS reflected signal power of the seawater area within the target sea area, proceed to step 102.

[0097] Step 102: Determine the observed left-handed reflectivity based on the GNSS direct signal power and the GNSS reflected signal power.

[0098] Left-Hand Circular Polarization Reflectivity (LHCPReflectivity) refers to the ratio of the power of the left-hand circular polarization (LHCP) component to the power of the incident right-hand circular polarization (RHCP) component after an electromagnetic wave is reflected from the surface of a target.

[0099] After obtaining the GNSS direct signal power and GNSS reflected signal power of the seawater area within the target sea area, the observed left-handed reflectivity can be determined based on these two values. Specifically, the power ratio between the GNSS reflected signal power and the GNSS direct signal power can be calculated, and this power ratio can be used as the observed left-handed reflectivity. The calculation formula is as follows:

[0100]

[0101] In the above formula, is a left-handed reflectivity observation value, is a GNSS reflected signal power, is a GNSS direct signal power.

[0102] After determining the left-handed reflectivity observation value based on the GNSS direct signal power and the GNSS reflected signal power, step 104 is performed.

[0103] Step 103: determining a left-handed reflectivity theoretical value according to measured seawater area reference data of the seawater area.

[0104] The seawater area reference data refers to seawater physical parameters obtained through field measurement or a historical database. In the present example, the seawater area reference data can be, but is not limited to, seawater salinity and seawater temperature data of the seawater area.

[0105] When calculating the correction coefficient of the target sea area, seawater area parameter data of the seawater area can be measured, and the left-handed reflectivity theoretical value can be determined according to the seawater area reference data. The implementation process can be described in detail in combination with the following specific implementation manners.

[0106] In a specific implementation of the present application, the above step 103 can include:

[0107] Sub-step B1: measuring seawater temperature and seawater salinity of the seawater area, and taking the seawater temperature and the seawater salinity as the seawater area reference data.

[0108] In the present example, the seawater temperature and the seawater salinity of the seawater area can be measured first, and the seawater temperature and the seawater salinity can be taken as the seawater area reference data. Specifically, the seawater temperature and the seawater salinity of the seawater area can be obtained through a CTD (Conductivity, Temperature, Depth) instrument, etc.

[0109] After obtaining the seawater area reference data, sub-step B2 is performed.

[0110] Sub-step B2: determining the left-handed reflectivity theoretical value based on the seawater temperature and the seawater salinity.

[0111] After obtaining the seawater region reference data, the left-handed reflectivity theoretical value of the seawater region can be determined based on the seawater temperature and the seawater salinity. Specifically, the measured seawater temperature and seawater salinity can be substituted into the seawater Debye model to obtain a seawater relative permittivity theoretical value of the seawater region. Then, the seawater relative permittivity theoretical value and the incident angle can be substituted into the Fresnel reflection model to obtain the left-handed reflectivity theoretical value. The incident angle is the incident angle of the GNSS direct signal corresponding to the GNSS direct signal power.

[0112] In the present embodiment, the seawater Debye model is a classical theory for describing the dielectric properties of a dielectric in an alternating electromagnetic field, used to characterize the polarization relaxation behavior of the medium. The seawater Debye model regards seawater as a complex dielectric composed of water molecules, ions, etc., and establishes a theoretical calculation model of the dielectric constant through parameters such as temperature, salinity, and frequency.

[0113] The Fresnel reflection model is based on Maxwell's equations and describes the reflection and transmission laws of electromagnetic waves at the interface of two media. The reflection coefficient is calculated through the dielectric constant of the medium and the incident angle, and then the polarization characteristics and power distribution of the reflected signal are obtained.

[0114] The implementation process of substituting the seawater temperature and the seawater salinity into the seawater Debye model to obtain the seawater relative permittivity theoretical value can be as follows:

[0115]

[0116] In the above formula, , is the seawater salinity (i.e., the seawater salt content), is the seawater temperature, is the electromagnetic wave frequency, is the complex permittivity of seawater (i.e., the seawater relative permittivity theoretical value in the present embodiment), is the static permittivity of seawater. is the dielectric constant of seawater at infinite frequency, which can be considered not affected by temperature and salt content, and has a value of 4.9. is the relaxation time, representing the time taken by seawater to complete the polarization process from the start. is the ionic conductivity of dissolved salt in seawater, with a unit of mho / m. i is the imaginary unit.

[0117] , , The relationship between and the seawater temperature and the seawater salinity can be represented by the Stogryn model (i.e., a semi-empirical model for calculating electromagnetic parameters such as the dielectric constant of seawater, saltwater, etc., which is an extension of the seawater Debye model framework) as follows:

[0118]

[0119]

[0120]

[0121] In the embodiment, the seawater and the oil are distinguished according to the relative dielectric constant value, the relative dielectric constant of the seawater can be represented by the Fresnel reflection coefficient, the Fresnel reflection coefficient of the vertical polarization The Fresnel reflection coefficient of the horizontal polarization can be represented as a function of the relative dielectric constant , as shown in the following formula:

[0122]

[0123]

[0124] wherein, represents the elevation angle, represents the relative dielectric constant of the medium.

[0125] Since the polarization mode of the GNSS satellite signal is RHCP, the polarization mode of the GNSS receiver signal is LHCP, and the Fresnel reflection coefficient of the mirror surface reflection point (i.e. the reflection point of the GNSS signal irradiated to the seawater area) can be represented as:

[0126]

[0127] The left-handed reflectivity can be represented as:

[0128]

[0129] That is, the square of the Fresnel reflection coefficient is the left-handed reflectivity.

[0130] The above formula can be obtained by comprehensively combining the above formula:

[0131]

[0132] The left-handed reflectivity theoretical value is the theoretical value of the seawater dielectric constant, and the left-handed reflectivity theoretical value can be obtained by substituting the theoretical value of the seawater dielectric constant and the satellite elevation angle when observing the seawater into the above formula.

[0133] Step 104: determining the correction coefficient corresponding to the target sea area based on the left-handed reflectivity observation value and the left-handed reflectivity theoretical value, the correction coefficient being used for correcting the dielectric constant for distinguishing the seawater and the oil film. ​

[0134] After obtaining the left-handed reflectivity observation value and the left-handed reflectivity theoretical value, a correction coefficient of the target sea area can be determined based on the left-handed reflectivity observation value and the left-handed reflectivity theoretical value, and the correction coefficient can be used to correct the dielectric constant for distinguishing seawater and oil film. Specifically, a ratio between the left-handed reflectivity theoretical value and the left-handed reflectivity observation value can be calculated, and the ratio is determined as the correction coefficient.

[0135] In a specific implementation, based on the formula in the above step 103, it can be derived that the influence of the calibration error of the same sensor in the similar environment is the same in different target areas, and in order to eliminate the influence of the calibration error, a proportional correction coefficient C is defined, and the formula is as follows:

[0136]

[0137] In the above formula, is the left-handed reflectivity observation value, is the left-handed reflectivity theoretical value.

[0138] The GNSS-R sea surface oil film detection correction coefficient determination method provided by the embodiments of the present application can calculate the correction coefficient by introducing the seawater area reference data, correct the dielectric constant for distinguishing seawater and oil film, thereby effectively reducing the influence of the calibration error, more truly reflecting the dielectric constant distribution of the detection area, and improving the accuracy of oil-water differentiation.

[0139] After obtaining the correction coefficient of the target sea area, the relative dielectric constant of the target sea area can be corrected, so as to determine the oil film detection result of the to-be-measured area according to the corrected dielectric constant. The implementation process can be described in detail in combination with the following specific implementation manners.

[0140] In a specific implementation of the present application, after the above step 104, the following can also be included:

[0141] Step C1: obtaining the target GNSS direct signal power and the target GNSS reflected signal power of the to-be-measured area of the target sea area, and the corresponding satellite elevation angle.

[0142] In the embodiments, when the oil film detection is performed on a certain area of the target sea area, the target GNSS direct signal power and the target GNSS reflected signal power of the to-be-measured area of the target sea area, and the corresponding satellite elevation angle can be obtained.

[0143] Step C2: determining the target left-handed reflectivity based on the target GNSS direct signal power and the target GNSS reflected signal power.

[0144] After obtaining the target GNSS direct signal power and the target GNSS reflected signal power, the target left-handed reflectivity can be determined based on the target GNSS direct signal power and the target GNSS reflected signal power. That is, the target left-handed reflectivity = target GNSS reflected signal power / target GNSS direct signal power.

[0145] Step C3: determining the relative permittivity corresponding to the to-be-measured area based on the target left-handed reflectivity, the satellite elevation angle and the correction coefficient.

[0146] After obtaining the target left-handed reflectivity, the relative permittivity corresponding to the to-be-measured area can be determined based on the target left-handed reflectivity, the satellite elevation angle and the correction coefficient. Specifically, the relative permittivity can be calculated based on the following formula (1):

[0147] (1)

[0148] In the above formula (1), is the relative permittivity, is the target left-handed reflectivity, is the satellite elevation angle, is the correction coefficient.

[0149] Step C4: determining the oil film detection result of the to-be-measured area according to the relative permittivity.

[0150] After obtaining the relative permittivity, the oil film detection result of the to-be-measured area can be determined according to the relative permittivity. Specifically, a threshold range of the relative permittivity of an oil film and a threshold range of the relative permittivity of seawater can be set in advance, and according to the threshold range in which the corrected relative permittivity is located, the oil film detection result of the to-be-measured area, i.e., whether the to-be-measured area has an oil film, can be determined.

[0151] The embodiments of the present application use the GNSS-R technology to inverse the oil spill area on the sea surface, and the direct signal power, the reflected signal power and the incident angle obtained by detection in combination with the reference data of seawater temperature and seawater salinity can obtain the dielectric constant after correction and scaling error. This method can effectively reduce the influence of scaling error by introducing reference data, and more truly reflect the dielectric constant distribution of the detection area.

[0152] In order to verify the above technical solutions, the embodiments of the present application have made related experiments, which are as follows:

[0153] The receiver used in the experiment has eight channels, which can receive the signals of GNSS satellite constellation in all observable angles (including GPS, BDS, GAL). The azimuth angle range is ±90°, the signal receiving frequency is 1 Hz, and the duration of each data receiving is about 1.5 hours. The receiver antenna adopts a fixed gain mode.

[0154] The specific implementation steps are as follows:

[0155] 1. Data acquisition and preprocessing. Obtain the GNSS direct signal power and reflected signal power of the mirror reflection point in the continuous detection period and their corresponding elevation angles, screen the data falling within the target area and having an elevation angle greater than 40°, measure the reference data of the seawater area not covered by the oil film, and the seawater temperature is 27℃ and the seawater salinity is 31‰.

[0156] 2. Calculate and correct the dielectric constant. Calculate the left-handed reflectivity of the mirror reflection point from the direct signal power and the reflected signal power, and together with the elevation angle, substitute it into the last formula in step 103 to obtain the uncorrected relative dielectric constant of the mirror reflection point. Substitute the seawater temperature and seawater salinity reference data of the seawater area into the Debye model and Stogryn model to obtain the theoretical value of the seawater relative dielectric constant as 70.7885, and substitute this theoretical value as the correction parameter of the seawater relative dielectric constant into the last formula in step 103 to obtain the reference left-handed reflectivity, and then substitute it into the first step in step 104 together with the left-handed reflectivity to obtain the correction coefficient. Substitute this correction coefficient into the above formula (1) to obtain the dielectric constant value of other areas after correcting and scaling the error in other detection areas, and the dielectric constant mean value of the oil film covered area is 17.5592.

[0157] 3. The reflectivity of the static water surface covered with oil film will show a downward trend after the signal is refracted and attenuated by the oil film. According to the approximate distribution of the oil film in the experimental scene and the oil film reflectivity distribution in the oil spill detection pool, the area of is considered as the area covered with oil film. The corrected data of the seawater area without oil film is taken as the theoretical value to correct the oil film data, and the relative dielectric constant of the oil film area is obtained. Through the test, it can be determined that the relative dielectric constant of the oil area and the seawater area is significantly different. In order to quantify the degree of this difference, the absolute value of the effect size can be calculated as (95% confidence interval [2.9025, 3.0423]), which is far beyond the effect threshold , which indicates that there is a very significant difference between the two groups, and the small range of confidence interval also emphasizes the robustness and reliability of this difference. Further combined with the probability histogram of the corrected dielectric constant of seawater and oil, as shown in Figure 3As shown, the horizontal axis represents the dielectric constant, and the vertical axis represents the probability (i.e., the frequency of occurrence of oil or seawater samples in the corresponding dielectric constant interval, i.e., the proportion of the number of samples in the interval to the total number of samples), the seawater region data is mainly concentrated in the range of 60-90, and the oil region data is concentrated in the range of 0-30, the distribution range of the two is small, and the dielectric constant of the seawater region is significantly higher than that of the oil region. This distribution characteristic is consistent with the above effect quantity analysis result, that is, the dielectric constant of the seawater and oil film regions is significantly different, and the oil and water can be effectively distinguished.

[0158] The embodiment of the present application can distinguish seawater and oil film covered regions while correcting the scaling error by referring to the data, thereby providing a more accurate technical idea and method for GNSS-R sea surface oil spill detection.

[0159] Reference Figure 4 , a structure schematic diagram of a GNSS-R sea surface oil film detection correction coefficient determination device provided by an embodiment of the present application is shown. As Figure 4 shown, the GNSS-R sea surface oil film detection correction coefficient determination device 400 can include:

[0160] The power acquisition module 410 is configured to acquire GNSS direct signal power and GNSS reflected signal power of a seawater region in a target sea area.

[0161] The observation value determination module 420 is configured to determine a left-handed reflectivity observation value based on the GNSS direct signal power and the GNSS reflected signal power.

[0162] The theoretical value determination module 430 is configured to determine a left-handed reflectivity theoretical value according to measured seawater region reference data of the seawater region.

[0163] The correction coefficient determination module 440 is configured to determine a correction coefficient corresponding to the target sea area based on the left-handed reflectivity observation value and the left-handed reflectivity theoretical value, and the correction coefficient is used to correct the dielectric constant of the seawater and oil film.

[0164] Optionally, the power acquisition module includes:

[0165] The initial power acquisition unit is configured to acquire initial GNSS direct signal power of a GNSS direct signal emitted by a GNSS satellite to the seawater region in a target time period, and initial GNSS reflected signal power of a GNSS reflected signal corresponding to the GNSS direct signal.

[0166] The power screening unit is configured to screen the GNSS direct signal power and the GNSS reflected signal power that meet the conditions from the initial GNSS direct signal power and the initial GNSS reflected signal power.

[0167] Optionally, the observation value determination module comprises:

[0168] a power ratio calculation unit configured to calculate a power ratio between the GNSS reflected signal power and the GNSS direct signal power;

[0169] an observation value acquisition unit configured to acquire the power ratio as the left-handed reflectivity observation value.

[0170] Optionally, the theoretical value determination module comprises:

[0171] a reference data acquisition unit configured to measure seawater temperature and seawater salinity of the seawater area, and acquire the seawater temperature and the seawater salinity as the seawater area reference data;

[0172] a theoretical value determination unit configured to determine the left-handed reflectivity theoretical value based on the seawater temperature and the seawater salinity.

[0173] Optionally, the theoretical value determination unit comprises:

[0174] a dielectric theoretical value acquisition sub-unit configured to substitute the seawater temperature and the seawater salinity into a seawater Debye model to obtain a seawater relative dielectric constant theoretical value of the seawater area;

[0175] a reflectivity theoretical value acquisition sub-unit configured to substitute the seawater relative dielectric constant theoretical value and an incident angle into a Fresnel reflection model to obtain the left-handed reflectivity theoretical value, the incident angle being an incident angle of a GNSS direct signal corresponding to the GNSS direct signal power.

[0176] Optionally, the correction coefficient determination module comprises:

[0177] a reflectivity ratio calculation unit configured to calculate a ratio between the left-handed reflectivity theoretical value and the left-handed reflectivity observation value;

[0178] a correction coefficient determination unit configured to determine the ratio as a correction coefficient corresponding to the target sea area.

[0179] Optionally, the device further comprises:

[0180] a target power acquisition module configured to acquire target GNSS direct signal power and target GNSS reflected signal power of a to-be-measured area of the target sea area, and a corresponding satellite elevation angle;

[0181] a target reflectivity determination module configured to determine a target left-handed reflectivity based on the target GNSS direct signal power and the target GNSS reflected signal power.

[0182] a dielectric constant determination module configured to determine a relative dielectric constant corresponding to the to-be-detected area based on the target left-handed reflectivity, the satellite elevation angle and the correction coefficient;

[0183] a detection result determination module configured to determine an oil film detection result of the to-be-detected area according to the relative dielectric constant.

[0184] Optionally, the dielectric constant determination module comprises:

[0185] The relative dielectric constant is calculated based on the following formula (1):

[0186] (1)

[0187] In the above formula (1), is the relative dielectric constant, is the target left-handed reflectivity, is the satellite elevation angle, is the correction coefficient.

[0188] The GNSS-R sea surface oil film detection correction coefficient determination apparatus provided by the embodiment of the present application can effectively reduce the influence of the calibration error, more truly reflect the dielectric constant distribution of the detection area, and improve the accuracy of oil-water differentiation by introducing the seawater area reference data to calculate the correction coefficient to correct the dielectric constant for distinguishing seawater and oil film.

[0189] In addition, the embodiment of the present application further provides an electronic device, which comprises a memory, a processor and a computer program stored in the memory and capable of running on the processor, and the computer program is implemented when the processor is executed to realize the above-mentioned GNSS-R sea surface oil film detection correction coefficient determination method.

[0190] Figure 5 A structural schematic diagram of an electronic device 500 according to an embodiment of the present application is shown. As shown in the figure, Figure 5 The electronic device 500 comprises a central processing unit (CPU) 501, which can perform various appropriate actions and processes according to computer program instructions stored in a read-only memory (ROM) 502 or loaded from a storage unit 508 to a random access memory (RAM) 503. In the RAM 503, various programs and data required for the operation of the electronic device 500 can also be stored. The CPU 501, the ROM 502 and the RAM 503 are connected to each other through a bus 504. An input / output (I / O) interface 505 is also connected to the bus 504.

[0191] A plurality of components in the electronic device 500 are connected to the I / O interface 505, including: an input unit 506, such as a keyboard, a mouse, a microphone, etc.; an output unit 507, such as various types of displays, a speaker, etc.; a storage unit 508, such as a magnetic disk, an optical disk, etc.; and a communication unit 509, such as a network card, a modem, a wireless communication transceiver, etc. The communication unit 509 allows the electronic device 500 to exchange information / data with other devices through a computer network, such as the Internet, and / or various telecommunication networks.

[0192] The various processes and methods described above can be performed by the processing unit 501. For example, the methods of any of the embodiments described above can be implemented as a computer software program tangibly embodied in a computer readable medium, such as the storage unit 508. In some embodiments, portions of the computer program, or all of the computer program, can be loaded onto the electronic device 500 via the ROM 502 and / or the communication unit 509. When the computer program is loaded onto the RAM 503 and executed by the CPU 501, one or more acts of the methods described above can be performed.

[0193] The embodiments of the present application also provide a computer readable storage medium, and the computer readable storage medium stores a computer program. The computer program is executed by a processor to implement various processes of the above-mentioned GNSS-R sea surface oil film detection correction coefficient determination method embodiments, and can achieve the same technical effects. To avoid repetition, details are not described here. The computer readable storage medium includes, for example, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, etc.

[0194] It should be noted that in this document, the terms "comprising", "including", or any other variant thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not only include those elements, but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without more limitations, an element defined by the phrase "comprising a" does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0195] Those skilled in the art can clearly understand that the above-mentioned embodiment method can be realized by means of software and necessary general hardware platform, of course, it can also be realized by hardware, but in many cases, the former is a better embodiment. Based on such understanding, the technical solutions of the present application can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) and includes a plurality of instructions for making a terminal (which can be a mobile phone, computer, server, air conditioner, or network device) execute the methods described in various embodiments of the present application.

[0196] The embodiments of the present application are described above in conjunction with the drawings, but the present application is not limited to the specific embodiments described above, which are only illustrative and not restrictive, and those of ordinary skill in the art can make many forms without departing from the purpose of the present application and the scope protected by the claims.

[0197] Those of ordinary skill in the art can realize that the units and algorithm steps of each example described in conjunction with the embodiments disclosed in the embodiments of the present application can be realized by electronic hardware or a combination of computer software and electronic hardware. Whether the functions are performed in hardware or software depends on the specific application and design constraints of the technical solutions. Those of ordinary skill in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0198] Those of ordinary skill in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described system, device and unit can refer to the corresponding processes in the foregoing method embodiments, which will not be described here.

[0199] In the embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only illustrative, for example, the division of the units is only a logical function division, and actual implementation can have another division manner, for example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the displayed or discussed units can be indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0200] The units described as separate components may or may not be physically separate, and the components displayed as units may or may not be physical units, that is, may be located in one place, or may be distributed to multiple network units. Part or all of the units can be selected according to actual needs to achieve the purpose of the embodiment scheme.

[0201] In addition, the functional units in each embodiment of the present application can be integrated in one processing unit, or each unit can be physically present separately, or two or more units can be integrated in one unit.

[0202] The functions, if realized in the form of software functional units and sold or used as independent products, can be stored in a computer readable storage medium. Based on such understanding, the technical solutions of the present application or the part of the present application that essentially contributes to the prior art or the part of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes a plurality of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: a U disk, a mobile hard disk, a ROM, a RAM, a magnetic disk or an optical disk, and various storage medium capable of storing program codes.

[0203] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed in the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for determining the correction coefficient for GNSS-R sea surface oil film detection, characterized in that, The method includes: Acquire the direct GNSS signal power and reflected GNSS signal power in the seawater area within the target sea area; Based on the GNSS direct signal power and the GNSS reflected signal power, the observed value of left-handed reflectivity is determined; Based on the seawater area reference data obtained from the measurement, the theoretical value of the left-handed reflectivity is determined; The ratio between the theoretical value of the left-handed reflectivity and the observed value of the left-handed reflectivity is calculated; the ratio is determined as the correction coefficient corresponding to the target sea area, and the correction coefficient is used to correct the dielectric constant that distinguishes seawater from oil film; Obtain the target GNSS direct signal power and target GNSS reflected signal power of the area to be measured in the target sea area, as well as the corresponding satellite elevation angle; The left-handed reflectivity of the target is determined based on the target's direct GNSS signal power and the target's reflected GNSS signal power. Based on the target left-handed reflectivity, the satellite elevation angle, and the correction coefficient, the relative permittivity of the region to be measured is determined; The oil film detection result of the test area is determined based on the relative permittivity.

2. The method according to claim 1, characterized in that, The acquisition of the direct GNSS signal power and the reflected GNSS signal power in the seawater area within the target sea area includes: The initial GNSS direct signal power of the GNSS direct signal transmitted by the GNSS satellite to the sea area during the target time period, and the initial GNSS reflected signal power of the GNSS reflected signal corresponding to the GNSS direct signal are obtained. From the initial GNSS direct signal power and the initial GNSS reflected signal power, select the GNSS direct signal power and the GNSS reflected signal power that meet the conditions.

3. The method according to claim 1, characterized in that, The determination of the left-handed reflectivity observation based on the GNSS direct signal power and the GNSS reflected signal power includes: The power ratio between the reflected GNSS signal power and the direct GNSS signal power was calculated. The power ratio is used as the observed value of the left-handed reflectivity.

4. The method according to claim 1, characterized in that, The step of determining the theoretical value of left-handed reflectance based on the seawater region reference data obtained from measurements includes: The seawater temperature and salinity of the seawater area are measured and used as reference data for the seawater area. The theoretical value of the left-handed reflectance is determined based on the seawater temperature and the seawater salinity.

5. The method according to claim 4, characterized in that, Determining the theoretical value of the left-handed reflectance based on the seawater temperature and the seawater salinity includes: Substituting the seawater temperature and salinity into the Debye model of seawater, the theoretical value of the relative permittivity of seawater in the seawater region is obtained; Substituting the theoretical value of the relative permittivity of seawater and the incident angle into the Fresnel reflection model, the theoretical value of the left-handed reflectivity is obtained, where the incident angle is the incident angle of the GNSS direct signal corresponding to the GNSS direct signal power.

6. The method according to claim 1, characterized in that, The determination of the relative permittivity of the region to be measured based on the target left-handed reflectivity, the satellite elevation angle, and the correction coefficient includes: The relative permittivity is calculated based on the following formula (1): （1） In the above formula (1), The relative permittivity, For the target left-handed reflectivity, The satellite elevation angle. This is the correction factor.

7. A GNSS-R device for determining the correction coefficient for sea surface oil film detection, characterized in that, The device includes: The power acquisition module is used to acquire the GNSS direct signal power and GNSS reflected signal power in the seawater area within the target sea area; The observation determination module is used to determine the left-handed reflectivity observation value based on the GNSS direct signal power and the GNSS reflected signal power. The theoretical value determination module is used to determine the theoretical value of the left-handed reflectance based on the seawater area reference data obtained from the measurement. The correction coefficient determination module is used to determine the correction coefficient corresponding to the target sea area based on the observed left-handed reflectance value and the theoretical left-handed reflectance value. The correction coefficient is used to correct the dielectric constant that distinguishes seawater from oil film. The correction coefficient determination module includes: A reflectance ratio calculation unit is used to calculate the ratio between the theoretical value of the left-handed reflectance and the observed value of the left-handed reflectance; The correction coefficient determination unit is used to determine the ratio as the correction coefficient corresponding to the target sea area; The device further includes: The target power acquisition module is used to acquire the target GNSS direct signal power and target GNSS reflected signal power of the area to be measured in the target sea area, as well as the corresponding satellite elevation angle; The target reflectivity determination module is used to determine the left-handed reflectivity of the target based on the target's direct GNSS signal power and the target's reflected GNSS signal power. The dielectric constant determination module is used to determine the relative dielectric constant of the area to be measured based on the target left-handed reflectivity, the satellite elevation angle, and the correction coefficient. The detection result determination module is used to determine the oil film detection result of the test area based on the relative permittivity.

8. The apparatus according to claim 7, characterized in that, The power acquisition module includes: The initial power acquisition unit is used to acquire the initial GNSS direct signal power of the GNSS direct signal transmitted by the GNSS satellite to the sea area during the target time period, and the initial GNSS reflected signal power of the GNSS reflected signal corresponding to the GNSS direct signal. A power filtering unit is used to filter out the GNSS direct signal power and the GNSS reflected signal power that meet the conditions from the initial GNSS direct signal power and the initial GNSS reflected signal power.

9. The apparatus according to claim 7, characterized in that, The observation determination module includes: A power ratio calculation unit is used to calculate the power ratio between the power of the GNSS reflected signal and the power of the GNSS direct signal. An observation acquisition unit is used to take the power ratio as the observed value of the left-handed reflectivity.

10. The apparatus according to claim 7, characterized in that, The theoretical value determination module includes: A reference data acquisition unit is used to measure the seawater temperature and salinity of the seawater area and use the seawater temperature and salinity as reference data for the seawater area. The theoretical value determination unit is used to determine the theoretical value of the left-handed reflectance based on the seawater temperature and the seawater salinity.

11. The apparatus according to claim 10, characterized in that, The theoretical value determination unit includes: The dielectric theory value acquisition subunit is used to substitute the seawater temperature and the seawater salinity into the Debye model of seawater to obtain the theoretical value of the relative permittivity of seawater in the seawater region. The reflectivity theoretical value acquisition subunit is used to substitute the theoretical value of the relative permittivity of seawater and the incident angle into the Fresnel reflection model to obtain the theoretical value of the left-handed reflectivity, wherein the incident angle is the incident angle of the GNSS direct signal corresponding to the GNSS direct signal power.

12. The apparatus according to claim 7, characterized in that, The dielectric constant determination module includes: The relative permittivity is calculated based on the following formula (1): （1） In the above formula (1), The relative permittivity, For the target left-handed reflectivity, The satellite elevation angle. This is the correction factor.

13. An electronic device, characterized in that, include: The memory, the processor, and the computer program stored in the memory and executable on the processor, wherein the computer program, when executed by the processor, implements the GNSS-R sea surface oil film detection correction coefficient determination method as described in any one of claims 1 to 6.

14. A readable storage medium, characterized in that, When the instructions in the storage medium are executed by the processor of the electronic device, the electronic device is able to perform the GNSS-R sea surface oil film detection correction coefficient determination method according to any one of claims 1 to 6.

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