Beidou interferometric altimeter ocean multi-parameter wide swath imaging data processing method and system

Abstract

This invention provides a method and system for processing multi-parameter wide-swath imaging data of a BeiDou interferometric altimeter, relating to the field of GNSS-R altimetry technology. The method includes: constructing a complete and rigorous data processing chain; through precise calculation of the interferometric geometric model of the time delay difference between GNSS-R direct and reflected signals and correction of the measured time delay difference error, significantly reducing the systematic error in the conversion process from the original signal to geophysical parameters, improving the accuracy and reliability of the final inverted parameters; and based on an adaptive data aggregation strategy of parameter spatiotemporal transformation characteristics and a spatial interpolation reconstruction process, intelligently "weaving" discrete strip data into a continuously covering wide-swath imaging data product, making the data format more in line with the analytical needs of fields such as oceanography and climatology, and improving the intuitiveness and usability of the product.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of GNSS-R altimetry technology, in particular to a Beidou interferometric altimeter ocean multi-parameter wide swath imaging data processing method and a Beidou interferometric altimeter ocean multi-parameter wide swath imaging data processing system. BACKGROUND

[0002] Global Navigation Satellite System Reflectometry (GNSS-R) is a new remote sensing method for the earth, which can obtain geophysical parameters of the earth such as ocean, land and ice cover by receiving signals reflected by the earth surface. GNSS-R interferometric altimetry technology synchronously receives direct and reflected signals of navigation satellites, and generates an interference waveform by directly correlating the full-bandwidth signals (including non-public encryption) received by the receiver, so as to accurately determine the time delay difference of the double signals. Compared with the traditional active radar altimetry, GNSS-R interferometric altimetry technology has the advantages of low cost, wide coverage and short revisit period. However, the Beidou interferometric altimeter still has problems such as insufficient data processing accuracy and reliability, discontinuous spatial observation data, poor product intuitiveness and usability when processing corresponding environmental parameters. SUMMARY

[0003] The embodiments of the present application provide a Beidou interferometric altimeter ocean multi-parameter wide swath imaging data processing method and system to solve or partially solve the problems of insufficient ocean parameter inversion accuracy caused by immature data processing algorithm of the Beidou interferometric altimeter, and poor spatial usability of data products caused by sparse and discontinuous original observation trajectory.

[0004] The embodiments of the present application disclose a Beidou interferometric altimeter ocean multi-parameter wide swath imaging data processing method, comprising:

[0005] Based on the precise ephemeris of the navigation satellite, the precise orbiting data of the receiver and the reference sea surface height model, the time delay difference interference geometric theoretical value between the direct signal and the reflected signal of GNSS-R is determined;

[0006] The original interference signal corresponding to the reflecting surface received by the receiver is processed for error correction to obtain a measured time delay difference value;

[0007] According to the difference between the time delay difference interference geometric theoretical value and the measured time delay difference value, the height information between the reflecting surface and the reference sea surface height model is calculated;

[0008] Based on the height information, at least two kinds of ocean environmental parameters with sparse strip distribution are obtained;

[0009] The time-space variation characteristics corresponding to the marine environment parameters are acquired, a data collection strategy corresponding to the time-space variation characteristics is determined, the marine environment parameters are collected according to the data collection strategy, and a continuous and wide imaging data product is generated through space interpolation reconstruction.

[0010] In some possible implementation manners, the precise ephemeris of the navigation satellite, the precise orbiting data of the receiver and the reference sea surface height model are used to calculate a time delay difference interferometric geometric theoretical value between direct signals and reflected signals of GNSS-R, and the time delay difference interferometric geometric theoretical value includes:

[0011] The precise ephemeris of the navigation satellite, the precise orbiting data of the receiver and the reference sea surface height model are acquired.

[0012] The spaceborne original observation time is determined, and the spaceborne original observation time, the precise ephemeris and the precise orbiting data are used for interpolation processing to determine the receiver platform mass center position of the receiver and the navigation satellite position of the navigation satellite at the reflection event time.

[0013] The reference sea surface height model is used as an initial reflection surface, and a sea surface mirror reflection point is iteratively calculated.

[0014] The receiver platform mass center position, the navigation satellite position and the sea surface mirror reflection point are used for calculation to obtain the time delay difference interferometric geometric theoretical value between direct signals and reflected signals of GNSS-R.

[0015] In some possible implementation manners, the reference sea surface height model is used as the initial reflection surface, and the sea surface mirror reflection point is iteratively calculated, and the method includes:

[0016] The reference sea surface height model is used as the initial reflection surface, and iterative calculation is performed according to Fermat's principle, and the height value of the reference sea surface height model is updated in each iteration until the position variation of the calculated sea surface mirror reflection point is less than a preset threshold, and the sea surface mirror reflection point at which the iterative calculation ends is obtained.

[0017] In some possible implementation manners, the receiver includes at least a direct receiving antenna and a reflected receiving antenna, and the receiver platform mass center position, the navigation satellite position and the sea surface mirror reflection point are used for calculation to obtain the time delay difference interferometric geometric theoretical value between direct signals and reflected signals of GNSS-R, and the method includes:

[0018] Satellite attitude data of the receiver are acquired.

[0019] A coordinate system conversion relationship corresponding to the satellite attitude data is determined.

[0020] Using the coordinate system transformation relationship, the phase center position of the direct receiving antenna and the phase center position of the reflective receiving antenna are calculated.

[0021] Using the navigation satellite position, the phase center position of the direct antenna, the phase center position of the reflective receiving antenna, and the sea surface mirror reflection point, the time delay difference interference geometric theoretical value between the direct signal received by the direct receiving antenna and the reflected signal received by the reflective receiving antenna is calculated.

[0022] In some feasible implementations, the coordinate system transformation relationship is used to calculate the phase center position of the direct receiving antenna and the phase center position of the reflective receiving antenna, which are obtained based on the following formula:

[0023]

[0024] Among them, the The position of the phase center of the direct receiving antenna or the phase center of the reflected receiving antenna in the satellite's coordinate system, obtained from ground measurements before satellite launch. The transformation matrix between the satellite body coordinate system and the satellite orbit coordinate system is described below. This is the transformation matrix between the satellite orbit coordinate system and the reference ellipsoid coordinate system.

[0025] In some feasible implementations, the step of performing error correction processing on the original interference signal received by the receiver corresponding to the reflecting surface to obtain the measured value of the time delay difference includes:

[0026] The initial time delay difference estimate is extracted from the original interference signal;

[0027] The initial time delay difference estimate is compensated and filtered by the interference waveform time delay measurement value to obtain the target time delay difference observation value;

[0028] For the target time delay difference observation value, hardware time delay deviation correction, antenna phase center time delay deviation correction, sea state deviation correction, ionospheric propagation delay correction and tropospheric propagation delay correction are performed in sequence to obtain the corresponding measured time delay difference value.

[0029] In some feasible implementations, the initial time delay difference estimate is subjected to interference waveform time delay measurement compensation and filtering to obtain the target time delay difference observation value. The interference waveform time delay measurement compensation and filtering are performed using the following formula:

[0030]

[0031] Among them, the For the target time delay difference observation value, the It is the impulse response function of the filter, the The estimated initial time delay difference value for the receiver, the This indicates the time delay difference compensation value obtained by using the waveform re-tracking method to measure the interferometric measured waveform.

[0032] In some feasible implementations, the observed target time delay difference is sequentially corrected for hardware time delay deviation, antenna phase center time delay deviation, sea state deviation, ionospheric propagation delay, and tropospheric propagation delay to obtain the corresponding measured time delay difference value, which is then corrected using the following formula:

[0033]

[0034] Among them, the This is the measured value of the time delay difference after error correction. For the target time delay difference observation value, This is the receiver hardware delay correction amount. This is the time delay correction for sea state deviation. This is the time delay correction amount for antenna phase center error. This is the correction amount for ionospheric time delay deviation. This is the correction amount for tropospheric time delay deviation.

[0035] In some feasible implementations, the step of calculating the elevation information of the reflecting surface relative to the reference sea surface height model based on the difference between the theoretical value of the time delay difference interferometric geometry and the measured value of the time delay difference includes:

[0036] Obtain the angle between the incident signal path of the navigation satellite signal at the sea surface mirror reflection point on the reference sea surface height model and the target angle in the direction of the normal to the reflecting surface;

[0037] The elevation information of the reflecting surface relative to the reference sea surface height model is obtained by using the difference between the theoretical value of the time delay difference interferometric geometry and the measured value of the time delay difference, as well as the included angle of the target.

[0038] In some feasible implementations, the elevation information between the reflecting surface and the reference sea surface height model is calculated using the difference between the theoretical value of the time delay difference interferometric geometry and the measured value of the time delay difference, as well as the target angle. This information is obtained through the following formula:

[0039]

[0040] Among them, the The time delay difference interferometric geometric model value, the The measured value of the time delay difference, the The included angle of the target is denoted as .

[0041] In some feasible implementations, the inversion based on elevation information to obtain at least two marine environmental parameters with sparse strip distribution includes:

[0042] When the reflecting surface is the sea surface, the elevation information is corrected for ocean tides, polar tides, solid earth tides, and atmospheric inversion to obtain the sea surface height or sea surface height anomaly with sparse strip distribution.

[0043] And / or, when the reflecting surface is an ice surface, the elevation information is geophysically corrected, and the thickness of the sparsely distributed sea ice is obtained by inversion according to the law of buoyancy.

[0044] And / or, acquire dual-frequency observation data from the receiver, perform dual-frequency combination inversion on the dual-frequency observation data, and obtain the total electron content of the ionosphere with sparse strip distribution.

[0045] In some feasible implementations, determining the data collection strategy corresponding to the spatiotemporal variation characteristics includes:

[0046] For marine environmental parameters that vary slowly in time but are highly spatially variable, the first strategy is adopted, which involves using a large time window and a small spatial window to collect data.

[0047] For atmospheric environmental parameters that vary rapidly in time and have weak spatial variation, a second strategy is adopted, which involves using a small time window and a large spatial window to collect data.

[0048] In some feasible implementations, the large time window is a first duration, and the small spatial window is a range of n degrees of latitude and longitude on Earth.

[0049] The smaller time window is the second duration, and the larger spatial window is the range of Earth's latitude and longitude in m degrees.

[0050] Wherein, the first duration is greater than the second duration; n and m are both positive integers, and the value of m is greater than the value of n.

[0051] In some feasible implementations, the step of collecting marine environmental parameters according to the data collection strategy and generating a continuously covered wide-swath imaging data product through spatial interpolation reconstruction includes:

[0052] The Kriging interpolation method is used to perform spatial interpolation on the sparse strip data collected by the data aggregation strategy to generate a continuously covered wide-span imaging data product.

[0053] This invention also discloses a BeiDou interferometric altimeter marine multi-parameter wide-swath imaging data processing system, comprising:

[0054] The calculation module is used to calculate the theoretical value of the time delay difference interference geometry between the direct and reflected signals of GNSS-R based on the precise ephemeris of navigation satellites, the precise orbit determination data of receivers, and the reference sea surface height model.

[0055] The correction module is used to perform error correction processing on the original interference signal received by the receiver and corresponding to the reflecting surface, and obtain the measured value of the time delay difference;

[0056] The elevation calculation module is used to calculate the elevation information between the reflecting surface and the reference sea surface height model based on the difference between the theoretical value of the time delay difference interferometric geometry and the measured value of the time delay difference.

[0057] The inversion module is used to perform inversion based on elevation information to obtain at least two marine environmental parameters with sparse strip distribution;

[0058] The imaging module is used to acquire the spatiotemporal variation characteristics corresponding to the marine environmental parameters, determine the data collection strategy corresponding to the spatiotemporal variation characteristics, collect the marine environmental parameters according to the data collection strategy, and generate a continuously covered wide-swath imaging data product through spatial interpolation reconstruction.

[0059] In some feasible implementations, the solution module is specifically used for:

[0060] Acquire precise ephemeris data of navigation satellites, precise orbit determination data from receivers, and reference sea surface height models;

[0061] The original observation time on the satellite is determined, and interpolation is performed using the original observation time, the precise ephemeris, and the precise orbit determination data to determine the position of the receiver platform centroid and the position of the navigation satellite at the moment of the reflection event.

[0062] Using the reference sea surface height model as the initial reflecting surface, the sea surface mirror reflection point is calculated iteratively;

[0063] The theoretical value of the time delay difference between the direct and reflected signals of GNSS-R is obtained by calculating the centroid position of the receiver platform, the position of the navigation satellite, and the sea surface mirror reflection point.

[0064] In some feasible implementations, the solution module is specifically used for:

[0065] Using the reference sea surface height model as the initial reflecting surface, iterative calculations are performed based on Fermat's principle, and the elevation value of the reference sea surface height model is updated in each iteration until the position change of the calculated sea surface mirror reflection point is less than a preset threshold, thus obtaining the sea surface mirror reflection point at the end of the iterative calculation.

[0066] In some feasible implementations, the receiver includes at least a direct receiving antenna and a reflective receiving antenna, and the calculation module is specifically used for:

[0067] Acquire the satellite attitude data of the receiver;

[0068] Determine the coordinate system transformation relationship corresponding to the satellite attitude data;

[0069] Using the coordinate system transformation relationship, the phase center position of the direct receiving antenna and the phase center position of the reflective receiving antenna are calculated.

[0070] Using the navigation satellite position, the phase center position of the direct antenna, the phase center position of the reflective receiving antenna, and the sea surface mirror reflection point, the time delay difference interference geometric theoretical value between the direct signal received by the direct receiving antenna and the reflected signal received by the reflective receiving antenna is calculated.

[0071] In some feasible implementations, the solution module is specifically used to solve the problem using the following formula:

[0072]

[0073] Among them, the The position of the phase center of the direct receiving antenna or the phase center of the reflected receiving antenna in the satellite's coordinate system, obtained from ground measurements before satellite launch. The transformation matrix between the satellite body coordinate system and the satellite orbit coordinate system is described below. This is the transformation matrix between the satellite orbit coordinate system and the reference ellipsoid coordinate system.

[0074] In some feasible implementations, the correction module is specifically used for:

[0075] The initial time delay difference estimate is extracted from the original interference signal;

[0076] The initial time delay difference estimate is compensated and filtered by the interference waveform time delay measurement value to obtain the target time delay difference observation value;

[0077] For the target time delay difference observation value, hardware time delay deviation correction, antenna phase center time delay deviation correction, sea state deviation correction, ionospheric propagation delay correction and tropospheric propagation delay correction are performed in sequence to obtain the corresponding measured time delay difference value.

[0078] In some feasible implementations, the correction module is specifically used to compensate for and filter the time delay measurement of the interference waveform using the following formula:

[0079]

[0080] Among them, the For the target time delay difference observation value, the It is the impulse response function of the filter, the The estimated initial time delay difference value for the receiver, the This indicates the time delay difference compensation value obtained by using the waveform re-tracking method to measure the interferometric measured waveform.

[0081] In some feasible implementations, the correction module is specifically used to perform correction using the following formula:

[0082]

[0083] Among them, the This is the measured value of the time delay difference after error correction. For the target time delay difference observation value, This is the receiver hardware delay correction amount. This is the time delay correction for sea state deviation. This is the time delay correction amount for antenna phase center error. This is the correction amount for ionospheric time delay deviation. This is the correction amount for tropospheric time delay deviation.

[0084] In some feasible implementations, the elevation information calculation module is specifically used for:

[0085] Obtain the angle between the incident signal path of the navigation satellite signal at the sea surface mirror reflection point on the reference sea surface height model and the target angle in the direction of the normal to the reflecting surface;

[0086] The elevation information of the reflecting surface relative to the reference sea surface height model is obtained by using the difference between the theoretical value of the time delay difference interferometric geometry and the measured value of the time delay difference, as well as the included angle of the target.

[0087] In some feasible implementations, the elevation information calculation module is specifically used to calculate the elevation information using the following formula:

[0088]

[0089] Among them, the The time delay difference interferometric geometric model value, the The measured value of the time delay difference, the The included angle of the target is denoted as .

[0090] In some feasible implementations, the inversion module is specifically used for:

[0091] When the reflecting surface is the sea surface, the elevation information is corrected for ocean tides, polar tides, solid earth tides, and atmospheric inversion to obtain the sea surface height or sea surface height anomaly with sparse strip distribution.

[0092] And / or, when the reflecting surface is an ice surface, the elevation information is geophysically corrected, and the thickness of the sparsely distributed sea ice is obtained by inversion according to the law of buoyancy.

[0093] And / or, acquire dual-frequency observation data from the receiver, perform dual-frequency combination inversion on the dual-frequency observation data, and obtain the total electron content of the ionosphere with sparse strip distribution.

[0094] In some feasible implementations, the imaging module is specifically used for:

[0095] For marine environmental parameters that vary slowly in time but are highly spatially variable, the first strategy is adopted, which involves using a large time window and a small spatial window to collect data.

[0096] For atmospheric environmental parameters that vary rapidly in time and have weak spatial variation, a second strategy is adopted, which involves using a small time window and a large spatial window to collect data.

[0097] In some feasible implementations, the large time window is a first duration, and the small spatial window is a range of n degrees of latitude and longitude on Earth.

[0098] The smaller time window is the second duration, and the larger spatial window is the range of Earth's latitude and longitude in m degrees.

[0099] Wherein, the first duration is greater than the second duration; n and m are both positive integers, and the value of m is greater than the value of n.

[0100] In some feasible implementations, the imaging module is specifically used for:

[0101] Using a Kriging interpolation device, spatial interpolation is performed on the sparse strip data collected by the aforementioned data aggregation strategy to generate a continuously covered wide-swath imaging data product.

[0102] This invention also discloses an electronic device, including a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other through the communication bus;

[0103] The memory is used to store computer programs;

[0104] When the processor executes a program stored in the memory, it implements the method described in the embodiments of the present invention.

[0105] This invention also discloses a computer-readable storage medium storing instructions that, when executed by one or more processors, cause the processors to perform the methods described in this invention.

[0106] The embodiments of the present invention have the following advantages:

[0107] In this embodiment of the invention, calculations are performed based on the precise ephemeris of navigation satellites, precise orbit determination data from receivers, and a reference sea surface height model to determine the theoretical value of the time delay difference interferometric geometry between the direct and reflected signals of GNSS-R. Error correction processing is then performed on the original interferometric signal received by the receiver corresponding to the reflecting surface to obtain the measured value of the time delay difference. Then, based on the difference between the theoretical and measured values ​​of the time delay difference interferometric geometry, the elevation information between the reflecting surface and the reference sea surface height model is calculated. Based on this elevation information, inversion is performed to obtain at least two sparsely distributed marine environmental parameters, and the spatiotemporal variation characteristics corresponding to these parameters are acquired. A data collection strategy corresponding to these spatiotemporal variation characteristics is then determined, and the data is collected according to the established data collection strategy. This approach aggregates marine environmental parameters and reconstructs them through spatial interpolation to generate continuously covered wide-swath imaging data products. This establishes a complete and rigorous data processing chain. By precisely solving the time delay difference interferometric geometric model and correcting for measured time delay errors, it significantly reduces systematic errors in the conversion process from raw signals to geophysical parameters, improving the accuracy and reliability of the final retrieved parameters. Furthermore, based on the adaptive data aggregation strategy of parameter spatiotemporal transformation characteristics and the spatial interpolation reconstruction process, discrete strip data are intelligently "woven" into continuously covered wide-swath imaging data products. This makes the data format more suitable for the analytical needs of fields such as oceanography and climatology, enhancing the intuitiveness and usability of the products. Attached Figure Description

[0108] Figure 1 This is a flowchart of the steps of a method for processing marine multi-parameter wide-swath imaging data using a Beidou interferometric altimeter provided in an embodiment of the present invention;

[0109] Figure 2 This is a flowchart of high-precision wide-swath imaging data processing provided in the embodiments of the present invention;

[0110] Figure 3 This is a schematic diagram of the interference geometry model provided in an embodiment of the present invention;

[0111] Figure 4 This is the sparse strip product provided in the embodiments of the present invention;

[0112] Figure 5 This is a wide-swath imaging data product provided in the embodiments of the present invention;

[0113] Figure 6 This is a structural block diagram of a Beidou interferometric altimeter marine multi-parameter wide-swath imaging data processing system provided in an embodiment of the present invention. Detailed Implementation

[0114] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0115] As an example, compared to active radar altimetry, the BeiDou interferometric altimeter employs a dual-base remote sensing system and utilizes existing navigation signal sources, offering advantages such as low cost, rapid global coverage, and high revisit frequency. It can provide crucial data support for global marine dynamic environment research, sea-level change monitoring, geoid refinement, polar sea ice thickness inversion, and ice sheet elevation measurement. However, in related technologies, the onboard data processing algorithms remain immature, and due to the limited number of navigation satellites, although it possesses an ultra-wide swath of thousands of kilometers, significant gaps exist between observation strips, affecting product intuitiveness and usability.

[0116] To address this, this invention utilizes precise ephemeris data from navigation satellites, precise orbit determination data from receivers, and a reference sea surface height model to calculate and determine the theoretical value of the time delay difference between the direct and reflected signals of the GNSS-R. Error correction processing is then applied to the original interference signal received by the receiver corresponding to the reflecting surface to obtain the measured value of the time delay difference. Based on the difference between the theoretical and measured values ​​of the time delay difference, the elevation information between the reflecting surface and the reference sea surface height model is calculated. Inversion is then performed based on this elevation information to obtain at least two sparsely distributed marine environmental parameters. The spatiotemporal variation characteristics corresponding to these marine environmental parameters are also acquired, and a data collection strategy corresponding to these spatiotemporal variation characteristics is determined. This data collection strategy is then implemented according to the data collection... This approach aggregates marine environmental parameters and reconstructs them through spatial interpolation to generate continuously covered wide-swath imaging data products. This establishes a complete and rigorous data processing chain. By precisely solving the time delay difference interferometric geometric model and correcting for measured time delay errors, it significantly reduces systematic errors in the conversion process from raw signals to geophysical parameters, improving the accuracy and reliability of the final retrieved parameters. Furthermore, based on the adaptive data aggregation strategy of parameter spatiotemporal transformation characteristics and the spatial interpolation reconstruction process, discrete strip data are intelligently "woven" into continuously covered wide-swath imaging data products. This makes the data format more suitable for the analytical needs of fields such as oceanography and climatology, enhancing the intuitiveness and usability of the products.

[0117] To enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention, some technical features involved in the embodiments of the present invention are explained and described below:

[0118] In this embodiment of the invention, the system architecture may include at least a signal transmission layer, a signal reception and acquisition layer, a data processing layer, and a data application layer.

[0119] The signal transmission layer can be a navigation satellite constellation (the following embodiments use one navigation satellite as an example for illustrative purposes). It can mainly include satellites of the BeiDou Global Navigation Satellite System, as well as satellite signals from other positioning systems such as the Global Positioning System and Galileo. For navigation satellites, they can continuously broadcast L-band navigation signals containing precise ranging codes and carrier phases. After being reflected by the Earth's surface, these signals can be received by this system for remote sensing without the need for the system to have its own radar transmitter, thus realizing the observation mode of bi-base radar.

[0120] The signal receiving and acquisition layer can be the BeiDou interferometric altimeter payload (hereinafter referred to as the payload). This payload can be deployed on the core hardware of the space-based satellite platform, and can include at least the receiver satellite platform (hereinafter referred to as the receiver), direct receiving antenna, reflective receiving antenna, and high-precision dual-frequency receiver, etc. The receiver carries the entire payload, providing on-orbit orbit, attitude, time, and power assurance. Its precise orbital position (precise orbit determination data) and real-time attitude serve as the data foundation for geometric calculations. The direct receiving antenna can be pointed towards the zenith to directly receive direct signals from navigation satellites. This signal provides a precise time reference and satellite ephemeris information, and serves as a reference for interferometric comparison with reflected signals. The reflective receiving antenna can be pointed towards the ground to specifically receive navigation satellite signals reflected from the sea or ice surface. This signal carries information about the physical characteristics of the reflecting surface (such as roughness and elevation). The high-precision dual-frequency receiver serves as the core data processing center for the payload. It can be used for: ① Synchronous correlation processing: Simultaneously processing both direct and reflected signals, performing interferometric correlation, and generating the original interferometric waveform; ② Data recording: Recording the interferometric waveform, the corresponding observation time, and auxiliary data from the satellite platform (such as coarse orbit and attitude); ③ Signal tracking: Tracking the direct signal, demodulating the navigation message, and providing frequency and code phase guidance for reflected signal processing.

[0121] The data processing layer can be an algorithm system, deployed on-board (for real-time / on-orbit processing) or on the ground (for refined offline processing). It can include at least a precision geometry calculation module, a signal correction and inversion module, and an imaging product generation module. Specifically, the precision geometry calculation module can be used to construct high-precision interferometric geometric models; the signal correction and inversion module can be used for waveform re-tracking, system error correction, and touch parameter inversion; and the imaging product generation module can be used for intelligent data aggregation, spatial interpolation reconstruction, and product formatting.

[0122] The data application layer can be used to generate corresponding wide-swath imaging maps, such as global sea level height anomaly maps, polar sea ice thickness distribution maps, and ionospheric TEC dynamic maps.

[0123] Based on the above system components, the overall workflow of the system can be summarized as follows: ① Illumination: Navigation satellite signals illuminate the global sea surface; ② Reception: The reflective antenna of the Beidou interferometric altimeter receives the scattered signal, while the direct antenna synchronously receives the direct signal; ③ Interference: The receiver performs interference processing on the two signals to form a correlation waveform sensitive to the Earth's surface; ④ Calculation: The data processing system uses precise orbits and geometric models to extract time delay difference information from the waveform with high precision; ⑤ Inversion and Imaging: After error correction and physical inversion, primary parameters are obtained, and then through intelligent aggregation and spatial interpolation, sparse strip data is "stitched" into a continuous image.

[0124] ReferenceFigure 1 The diagram illustrates a flowchart of a method for processing marine multi-parameter wide-swath imaging data using a BeiDou interferometric altimeter, as provided in an embodiment of the present invention. Specifically, the method may include the following steps:

[0125] Step 101: Based on the precise ephemeris of the navigation satellite, the precise orbit determination data of the receiver, and the reference sea surface height model, calculate and determine the theoretical value of the time delay difference interference geometry between the direct signal and the reflected signal of GNSS-R.

[0126] In this embodiment of the invention, before starting imaging data processing, the necessary high-precision input information can be obtained. This input information includes at least the precise ephemeris of the navigation satellite, the precise orbit determination data of the receiver, and the reference sea surface height model, so as to determine the theoretical value of the time delay difference interference geometry between the direct signal and the reflected signal of the GNSS-R based on these data.

[0127] The precise ephemeris of navigation satellites can be a set of data files that describe the three-dimensional position and three-dimensional velocity of the navigation satellite in a ground-fixed coordinate system (such as the International Terrestrial Reference Frame, ITRF) at a specific moment with extremely high precision. Optionally, it can be in SP3 format, with orbital accuracy down to the centimeter level. For example, for GPS (Global Positioning System) satellites, the final precise ephemeris product released by the IGS (International GNSS Service) can be downloaded, with an accuracy better than 2.5 centimeters. For BeiDou satellites, precise ephemeris data can be calculated using data from the MGEX (Multi-GNSS Experiment) tracking network.

[0128] The precise orbit determination data from the receiver is similar to precise ephemeris data. It provides a high-precision description of the orbital position and velocity of the satellite platform carrying the BeiDou interferometric altimeter in the same Earth-fixed coordinate system, which can be used to determine the precise coordinates of the receiver platform's center of mass. For example, it can be obtained by combining data from the BeiDou interferometric altimeter, a spaceborne GNSS receiver (different from the interferometric altimeter), or satellite laser ranging (SLR) data with precise orbit determination software (such as Bernese, GAMIT / GLOBK). Correspondingly, its accuracy can also reach the centimeter level.

[0129] A reference sea level model can be a global digital model describing the height of the Earth's mean sea level relative to a reference ellipsoid, providing the initial "sea surface" shape needed to calculate specular reflection points. For example, a reference sea level model can include the EGM2008 geoid model or the CNES-CLS18 mean sea level model. The EGM2008 model provides global 2.5′×2.5′ grid geoid undulation data, which can be overlaid onto the WGS84 ellipsoid to create an initial reflecting surface that more closely approximates the true mean sea level.

[0130] In some feasible implementations, the calculation process for the theoretical value of the time delay difference interferometric geometry involves, after obtaining the precise ephemeris of the navigation satellite, the precise orbit determination data of the receiver, and the reference sea surface height model, further determining the original onboard observation time. Then, using the original onboard observation time, precise ephemeris, and precise orbit determination data, interpolation is performed to determine the receiver platform's centroid position and the navigation satellite's position at the moment of the reflection event. Next, using the reference sea surface height model as the initial reflecting surface, the sea surface mirror reflection point is iteratively calculated. Finally, based on the receiver platform's centroid position, the navigation satellite's position, and the sea surface mirror reflection point, the GNS is calculated. The theoretical value of the time delay difference between the direct and reflected signals of the S-R signal is obtained through interferometric geometry. This ensures the time consistency of the satellite and receiver position calculations through time synchronization interpolation, avoiding the reference error introduced by time asynchrony. Furthermore, by continuously using a more refined geophysical model to correct the reflecting surface, the positioning of the reflection point is gradually converged from the initial estimate based on the smooth model to a precise position that conforms to the actual geophysical state at the moment of observation. This allows all subsequent calculations based on the theoretical value of the time delay difference to be established on an extremely solid and accurate geometric foundation, achieving ultra-high precision geometric reference modeling and laying a reliable data foundation for the entire subsequent inversion chain.

[0131] Regarding the above process, an observation event involves several key points: the signal transmitter (navigation satellite) T ), signal receiver (receiver platform centroid) R ) and signal transmission point (sea surface mirror reflection point) O For example, if we want to determine whether something is happening at the same instant, then we need to first determine whether it is happening at the same instant. T and R The precise location. The original observation time on the satellite can be a time stamp taken by the payload receiver, marking the moment the original interferometric waveform was formed. This time can be unified to GPS time or BeiDou time.

[0132] In practical implementation, since precise ephemeris and precise orbit determination data are usually given as discrete points at certain time intervals (e.g., 15 minutes), while the original onboard observation time is arbitrary, interpolation algorithms can be used to obtain the precise positions of the receiver and navigation satellite at the corresponding moments of the original onboard observation time. Optionally, Lagrange interpolation can be used, employing an nth-order Lagrange interpolation based on several precise ephemeris points (e.g., x points before, x points after, etc.) before and after the original onboard observation time. This can yield the navigation satellite position at the original onboard observation time with millimeter-level accuracy. T Similarly, by interpolating the precise orbit determination data of the receiver, the position of the receiver platform's center of mass at the original observation time on space can be obtained. R .

[0133] For example, using eight precise ephemeris points (four before and four after) before and after the original onboard observation time, a 9th-order Lagrange interpolation can be performed to obtain the navigation satellite's position at the original onboard observation time with millimeter-level accuracy. T Similarly, by interpolating the precise orbit determination data from the receiver, the position of the receiver platform's center of mass at the original observation time on the satellite is obtained. R .

[0134] After obtaining the centroid position of the receiver platform and the position of the navigation satellite, the specular reflection point can be determined based on Fermat's principle in geometric optics (light travels along the shortest path). O This can be to make the total path length TO + OR The point is the stationary point (which can be the minimum value). Since the initial reference sea level model can be a smooth model, while the real sea surface is undulating, the real reflection point can be approximated through iterative calculation.

[0135] In some feasible implementations, a reference sea surface height model can be used as the initial reflecting surface. Then, iterative calculations are performed based on Fermat's principle, updating the elevation value of the reference sea surface height model in each iteration until the calculated positional change of the sea surface specular reflection point is less than a preset threshold. This yields the sea surface specular reflection point at the end of the iterative calculation, thus achieving a qualitative leap in reflection point positioning from "static approximation" to "dynamic convergence," significantly improving positioning accuracy. The iterative calculation process may include:

[0136] 1. Initialization iteration (zeroth iteration):

[0137] The initial reflecting surface is a WGS84 reference ellipsoid superimposed with a reference sea level model. On this initial reflecting surface, based on Fermat's principle (signal propagation path takes extreme values), and utilizing the already determined navigation satellite positions... T and the center of mass position of the receiver platformR An initial sea surface mirror reflection point is obtained by solving. O 0. Optionally, this process can be used to solve for a path length ( TO + OR The nonlinear equation system.

[0138] 2. Reflector model update and iterative calculation:

[0139] At the calculated initial reflection point O At point 0, query and obtain more detailed geophysical data, including the initial reflection point. O The mean sea level is 0, along with instantaneous corrections for ocean tides, solid earth tides, and atmospheric inversion. These geophysical corrections are then superimposed onto the initial reflector surface to construct an updated reflector model that more closely approximates the actual sea surface state at the time of observation. Based on this updated reflector model, with... O Using 0 as the initial guess, a new and more accurate specular reflection point on the sea surface was obtained by recalculating geometrically based on Fermat's principle. O 1.

[0140] 3. Iterative convergence judgment:

[0141] Calculate the difference between the reflection point positions obtained from the two iterations, i.e., the vector. O 1 and O The Euclidean norm of 0 || O 1- O 0||. If the change in position is less than a preset convergence threshold (e.g., 1 cm), the iterative calculation is considered to have converged. At this point, O 1 was identified as the final high-precision sea surface mirror reflection point. O If the change in position is greater than or equal to the convergence threshold, then convergence has not yet occurred. In this case, [the following will be done]. O 1 is used as the new initial point, and based on its corresponding latest reflector model, step 2 (reflector model update and calculation) is repeated to perform the next iteration until the convergence condition is met.

[0142] In the aforementioned iterative calculation process, by continuously introducing and integrating the instantaneous geophysical effects at the observation time, the "sea surface" height model used for geometric calculation is continuously corrected, so that the calculation benchmark of the reflection point gradually approaches the dynamic real instantaneous sea surface from a static long-term average sea surface. Through this process, the theoretical positioning error of the mirror reflection point can be significantly reduced from the meter level to the centimeter level, thus laying a crucial geometric foundation for the subsequent inversion of high-precision parameters such as sea surface height.

[0143] Furthermore, calculating the path length using the receiver platform's centroid position is not accurate enough because the actual electrical center of the signal being received and transmitted is the antenna's phase center. Since the phase center has a fixed offset in the satellite's coordinate system, a better approach is to acquire the receiver's satellite attitude data, determine the corresponding coordinate system transformation, and then use this transformation to calculate the phase center positions of the direct receiving antenna and the reflective receiving antenna. Finally, using the navigation satellite position, the direct antenna phase center position, the reflective receiving antenna phase center position, and the sea surface mirror reflection point, the theoretical value of the time delay difference interference geometry between the direct signal received by the direct receiving antenna and the reflected signal received by the reflective receiving antenna can be calculated.

[0144] Optionally, the phase center positions of the direct receiving antenna and the reflective receiving antenna are calculated using coordinate system transformation relationships, based on the following formula:

[0145] (1)

[0146] in, This refers to the position of the phase center of the direct receiving antenna or the phase center of the reflected receiving antenna in the satellite's coordinate system, obtained from ground measurements. This is the transformation matrix between the satellite body coordinate system and the satellite orbit coordinate system. This is the transformation matrix between the satellite orbit coordinate system and the reference ellipsoid coordinate system.

[0147] In practical implementation, the transformation of the antenna phase center from the satellite body coordinate system to the reference ellipsoid coordinate system requires two consecutive coordinate rotation transformations. The corresponding transformation process can be as follows:

[0148] 1. Input Acquisition: Known position vector of the antenna phase center in the satellite body coordinate system. This value was obtained through precise ground measurements and calibrations before the satellite launch.

[0149] 2. First Transformation (Satellite Body -> Orbit): Using real-time attitude data from the receiver satellite platform (obtained by star sensors, gyroscopes, etc.), determine the transformation matrix from the satellite body coordinate system to the satellite orbit coordinate system. .

[0150] 3. Second transformation (orbit -> reference ellipsoid): Using the precise orbital parameters of the receiver satellite platform, determine the transformation matrix from the satellite orbital coordinate system to the reference ellipsoidal coordinate system. .

[0151] 4. Comprehensive Calculation: The final position of the antenna phase center in the reference ellipsoidal coordinate system is calculated using the following matrix multiplication formula:

[0152]

[0153] The above formula can be applied to both the direct receiving antenna and the reflected receiving antenna of the receiver, that is, it can be used to calculate the position of the phase center of the direct antenna in the reference ellipsoidal coordinate system. R D The position of the phase center of the reflecting antenna in the reference ellipsoidal coordinate system R R Thus utilizing the position of navigation satellites T and the calculated RD , RR and the mirror reflection point of the sea surface O In order to calculate the theoretical value of the time delay difference interference geometry using the geometric distance formula. ρg This lays a precise geometric foundation for subsequent high-precision parameter inversion.

[0154] After obtaining the precise coordinates of all points, the theoretical value of the time delay difference interferometry can be further calculated. The two paths of signal propagation can include:

[0155] ① Reflection path: Signal from navigation satellite position T Departure, passing the specular reflection point on the sea surface (or ice surface) O After reflection, it reaches the phase center position of the reflecting antenna. R R The total geometric length of the path L reflect It can be:

[0156] L reflect =∣ T O ∣+∣ O R R |

[0157] Among them, | T O | represents the distance from satellite T to the reflection point O The straight-line distance, | O R R | represents the reflection point O To the phase center of the reflecting antenna R R The straight-line distance.

[0158] ② Direct path: The signal originates from the location of the same navigation satellite. It starts and propagates directly to the phase center of the direct-fire antenna. RD Position of navigation satellites along direct path Position of navigation satellites with reflection path T They are very close, but there are some differences due to the different signal transmission times. The geometric length of the path... L direct It can be:

[0159] L direct =∣ R D |

[0160] Furthermore, the additional path length that the reflected signal travels compared to the direct signal is the theoretical value of the time delay difference in interferometric geometry. ρ g That is, the theoretical value of the time delay difference interferometric geometry can be calculated using the following formula. ρ g :

[0161] ρ g = L reflect L direct =∣ T O ∣+∣ O R R | | R D ∣= ρ gs + ρ rs ρ gr

[0162] in, ρ g It characterizes the theoretical propagation delay (in length) of the reflected signal relative to the direct signal under an ideal reference sea surface model and precise geometric configuration. , and These represent the distances between the GNSS satellite position and the specular reflection point on the Earth's sea surface height model, the distance between the phase center of the receiver's reflecting antenna and the specular reflection point, and the distance between the GNSS satellite position and the phase center of the receiver's direct receiving antenna, respectively. These are key benchmarks for subsequent comparison with the measured time delay difference and for inverting parameters such as sea surface height.

[0163] Step 102: Perform error correction processing on the original interference signal received by the receiver corresponding to the reflecting surface to obtain the measured value of the time delay difference;

[0164] In this embodiment of the invention, the original observation data is full of various noises, so it is necessary to extract the time delay difference that reflects the real physical process and systematically remove various errors in order to obtain a "pure" measured value that can be compared with the theoretical value of the time delay difference interference geometry with high precision.

[0165] In some feasible implementations, the initial time delay difference estimate can be extracted from the original interferometric signal. Then, the initial time delay difference estimate is compensated and filtered by the interferometric waveform time delay measurement value to obtain the target time delay difference observation value. Then, the target time delay difference observation value is sequentially corrected by hardware time delay deviation, antenna phase center time delay deviation, sea state deviation, ionospheric propagation delay, and tropospheric propagation delay to obtain the corresponding measured time delay difference value. This constructs a standardized processing chain from "original observation" to "clean observation", realizes the systematic removal and suppression of errors, and significantly improves the absolute accuracy and physical consistency of the measured time delay difference value, providing a reliable input for high-precision elevation inversion.

[0166] The compensation and filtering process for the time delay measurement of the interference waveform can be calculated using the following formula:

[0167] (3)

[0168] in, For the target time delay difference observation value, It is the impulse response function of the filter. The initial delay difference estimate is the value predicted by the receiver. This indicates the time delay difference compensation value obtained by using the waveform re-tracking method to measure the interferometric measured waveform.

[0169] In addition, for the observed target time delay difference, hardware time delay deviation correction, antenna phase center time delay deviation correction, sea state deviation correction, ionospheric propagation delay correction, and tropospheric propagation delay correction are performed sequentially to obtain the corresponding measured time delay difference value, which is then corrected using the following formula:

[0170] (4)

[0171] in, This is the measured value of the time delay difference after error correction. For the target time delay difference observation value, This is the receiver hardware delay correction amount. This is the time delay correction for sea state deviation. This is the time delay correction amount for antenna phase center error. This is the correction amount for ionospheric time delay deviation. This is the correction amount for tropospheric time delay deviation.

[0172] For the above process, the original interference signal can be a series of signals output by the receiver at different time delays. τ and Doppler shift fd coherent integral value on Y ( τ , f d This refers to Delay-Doppler Mapping (DDM) or, at 0 Doppler frequency shift, different time delays. τ coherent integral value on Y ( τ , f 0), i.e., one-dimensional delay waveform map (DM). Due to the roughness and noise of the actual sea surface, the peak of the DDM or DM will broaden and shift. Therefore, the least-squares fitting of the measured waveform with a theoretical waveform template (such as a waveform generated based on geometric optics or integral equation models) can be performed by a re-tracking algorithm to accurately estimate the time delay offset Δ corresponding to the peak point of the first derivative of the waveform leading edge or the waveform leading edge. e For example, an initial coarse tracking can be performed using the "OCOG" (Offset Center of Gravity) algorithm or a "threshold" algorithm, followed by fine tracking using "polynomial fitting" or "maximum likelihood estimation," ultimately outputting a time delay observation relative to the receiver's internal timing reference. (Estimated internally by the receiver) and the compensation value Δ obtained through waveform fitting .

[0173] Next, compensation and filtering of the interference waveform time delay measurement values ​​can be performed. With Δ The initial time delay difference observation sequence obtained by addition It contains high-frequency noise (such as thermal noise and flicker noise). Specifically, the initial time delay difference estimate can first be compensated by the interference waveform time delay measurement value, that is, the value calculated by the following formula:

[0174]

[0175] Then, to The sequence is filtered. Optionally, it can be filtered using a Butterworth filter due to its flat passband frequency response. For example, a 6th-order Butterworth filter with a cutoff frequency of 0.01 Hz can be designed to filter the sequence along the track. The time series is filtered to remove high-frequency fluctuations, resulting in a smooth sequence. This process helps to reconcile the observed time delay difference with the theoretical value of the time delay difference interferometric geometry. ρ g Perform effective differencing to isolate systematic biases.

[0176] Furthermore, to improve the accuracy of the parameters, the following main error sources can be corrected sequentially:

[0177] 1. Hardware delay deviation Δ ρ hw :

[0178] Source: Fixed delay generated during signal transmission through components such as the receiver's RF front-end, cables, and filters. The hardware delays of the direct and reflected channels are typically different.

[0179] Correction method: Before the payload is launched, a rigorous internal delay calibration is performed in a ground microwave anechoic chamber to accurately measure the hardware delay difference between the two channels, which is then subtracted as a fixed constant during data processing. After launch, a cross-calibration method is used for correction.

[0180] 2. Antenna phase center time delay deviation Δ ρ ant :

[0181] Source: The beam direction of direct and reflective antennas varies with the reflection point of the mirror and is not an ideal point source, so the beam has a certain width.

[0182] Correction methods: Based on the antenna phase center pointing model and the pointing angles of direct and reflected antennas, the delay correction is calculated using the pointing model. Alternatively, parameterized correction can be performed using an empirical model.

[0183] 3. Sea state deviation Δ ρ ssb :

[0184] Source: A rough sea surface causes the effective scattering surface of reflected signals to be higher than that of the average sea surface, resulting in a shorter measured distance. This is a well-known phenomenon in radar gauging called "Sea State Bias" (SSB).

[0185] Correction methods: Parametric models related to significant wave height (SWH) and wind speed are typically used. For example, the model form is as follows: SSB = a SWH+ b U10 Where U10 can be a wind speed of 10 meters per second, and the coefficient is... a , b It was obtained through cross-calibration with other altimeter satellite data.

[0186] 4. Ionospheric propagation delay Δ ρ ion :

[0187] Source: When navigation signals pass through the ionosphere, their propagation speed changes, causing additional time delays. This delay is inversely proportional to the square of the signal frequency.

[0188] Correction method: Utilizing the dual-frequency observation advantages of the BeiDou interferometric altimeter. Through... L1 and L2 Frequency delay difference observations and The ionospheric delay can be calculated directly:

[0189]

[0190] in, f L1 and f L2 This process, which can be performed on the carrier frequency, allows for the real-time and accurate elimination of corresponding errors without the need for an external ionospheric model.

[0191] 5. Tropospheric propagation delay Δ ρ trop :

[0192] Source: Delay caused by the reduced propagation speed of signals in the troposphere (especially water vapor). It is divided into dry delay (accounting for about 90%) and wet delay.

[0193] Correction methods: The dry delay can be calculated with high precision using surface pressure models (such as the Saastamoinen model). The wet delay varies more significantly and usually requires correction using moisture content data provided by numerical weather prediction models (such as ECMWF) through ray tracing.

[0194] Integrating the above correction process, the comprehensive correction formula can be obtained by subtracting all correction terms sequentially from the filtered time delay difference, thus obtaining the refined measured time delay difference value:

[0195]

[0196] Through the above process This can reflect the time delay difference caused solely by changes in the actual elevation of the reflecting surface to the greatest extent possible.

[0197] Step 103: Based on the difference between the theoretical value of the time delay difference interferometric geometry and the measured value of the time delay difference, calculate the elevation information between the reflecting surface and the reference sea surface height model;

[0198] After obtaining the theoretical value of the time delay difference interferometric geometry and the measured value of the time delay difference, the elevation information between the reflecting surface and the reference sea surface height model can be obtained by solving based on the two. The elevation information represents the vertical height difference of the specular reflection point on the reflecting surface (such as the sea surface or ice surface) relative to a known and fixed reference datum surface (i.e., the reference sea surface height model) at the instant of observation.

[0199] In the process of calculating elevation information, due to the time delay difference, the geometric theoretical value of interference is... ρ g It is calculated based on a known reference sea level model, and the actual measured time delay difference... ρ m1 and ρ g The difference stems directly from the elevation difference Δ between the actual reflecting surface and the reference model. h .

[0200] In some feasible implementations, during the calculation of elevation information, the incident signal path of the navigation satellite signal at the sea surface mirror reflection point on the reference sea surface height model and the target angle between the normal direction of the reflecting surface can be obtained first. Then, the difference between the theoretical value of the time delay difference interferometric geometry and the measured value of the time delay difference, as well as the target angle, are used to calculate the elevation information between the reflecting surface and the reference sea surface height model. This establishes a direct and rigorous physical conversion bridge between observational measurements and geophysical quantities, ensuring the correctness and high fidelity of the inversion principle, and realizing the extraction of centimeter-level elevation information, providing a high-precision core input for subsequent multi-parameter inversion.

[0201] In practical implementation, it can be calculated using the following formula:

[0202]

[0203] in, The time delay difference is the value of the interferometric geometric model. This is the measured value of the time delay difference. The included angle is the target angle.

[0204] In the above process, θ It can be used to reflect satellite signals at the mirror point O The angle of incidence at the point is equal to the angle between the incident direction and the normal direction of the reflecting surface, which can be accurately obtained from the geometric configuration calculated in the aforementioned embodiments.

[0205] After obtaining the corresponding target angle θ, we can first perform the corresponding geometric relationship modeling, assuming that the actual reflection point has a small elevation change Δ relative to the reference sea surface height model. h (Perpendicular to the reference plane and outwards is positive), then according to geometric relationships, this elevation change will result in the propagation path of the reflected signal (T→O→). R The path length changes. The change in path length is Δ. L Approximately 2Δ h cos θ , where the factor cos θ This is the projection coefficient of the path change in the vertical direction; the factor of 2 is because the path includes both incident and reflected segments. Next, observational correlation is performed; specifically, the change in the path length Δ... L This directly corresponds to the observed theoretical time delay difference. ρ g Difference from measured delay ρ m1 The difference between them is:

[0206] ρ g ρ m1 ≈Δ L =2Δ h cos θ

[0207] If the actual sea level is higher than the reference model (Δ) h >0), the reflection path becomes shorter, then the measured time delay difference ρ m1 Will be less than the theoretical value ρ g , making ρ g ρ m1 >0, logically consistent.

[0208] Furthermore, based on the above relationship, the formula for calculating the instantaneous elevation of the reflecting surface relative to the reference sea surface height model can be directly derived, that is:

[0209]

[0210] in: SSH ori : Represents the instantaneous sea surface height at the reflection point, that is, the vertical height difference relative to the reference sea surface height model; ρ g The theoretical value of the time delay difference interference geometry obtained from the foregoing embodiments; ρ m1: The measured time delay difference obtained from the aforementioned process after error correction; θ The angle of incidence of the signal at the point of reflection on the mirror.

[0211] In some feasible examples, let's assume a single observation instance:

[0212] Theoretical value of time delay difference interferometry ρ g =10000.500 meters.

[0213] Corrected measured time delay difference ρ m1 =10000.200 meters.

[0214] Signal incident angle θ =30°, then cos θ ≈0.8660.

[0215] Substitute the above values ​​into the formula to calculate:

[0216]

[0217] Therefore, the calculation results show that at this observation point, the instantaneous sea level is approximately 17.3 cm higher than the reference sea level model. SSH ori This serves as the foundational data for subsequent inversion of more refined ocean parameters (such as sea surface height anomalies after deducting tides).

[0218] Step 104: Perform inversion based on elevation information to obtain at least two marine environmental parameters for sparse strip distribution;

[0219] After obtaining the corresponding elevation information, it is possible to invert it based on the physical characteristics corresponding to different reflective surfaces to obtain at least two marine environmental parameters with sparse strip distribution, which can then be transformed into different oceanographic or geophysical parameters.

[0220] In some feasible implementations, when the reflecting surface is the sea surface, the elevation information is corrected for ocean tides, polar tides, solid earth tides, and atmospheric inversion to obtain the sparsely distributed sea surface height or sea surface height anomaly; and / or, when the reflecting surface is ice, the elevation information is geophysically corrected, and the sparsely distributed sea ice thickness is obtained by inversion based on the law of buoyancy; and / or, dual-frequency observation data from the receiver is acquired, and dual-frequency combined inversion is performed on the dual-frequency observation data to obtain the sparsely distributed total electron content of the ionosphere. This achieves a highly efficient inversion capability of "one unit for multiple uses," enabling the synchronous or selective generation of geophysical products of different properties, greatly improving the data output value and cost-effectiveness of a single payload, and ensuring that multi-parameter products have a common high-precision benchmark and a consistent spatiotemporal framework, which is conducive to fusion analysis and collaborative applications.

[0221] In practical implementation, assuming the reflecting surface is the sea surface, the elevation information includes sea surface deformation caused by various periodic forces. To obtain sea surface height anomalies reflecting ocean circulation and the gravitational field, the effects of ocean tides, polar tides, solid Earth tides, and atmospheric inversion pressure must be subtracted. Specifically, for ocean tides Δ... Tide ocean : Calculate the tidal height at the observation time and observation point using a global tidal model (such as FES2014, TPXO9), and subtract the tidal height; for polar tides Δ Tide pole The sea level changes caused by the Earth's axial tilt are subtracted using a model; for the solid Earth's tides Δ Tide solid Elastic deformation of the solid Earth under the gravitational pull of the Sun and Moon is subtracted using the Standard Model; atmospheric inversion correction Δ IBL The static response of the sea surface caused by changes in atmospheric pressure is calculated using atmospheric pressure field data and subtracted from other parameters. The final product can be:

[0222] SSH anomaly = SSH ori Δ Tide ocean Δ Tide pole Δ Tide solid Δ IBL

[0223] Among them, the obtained SSH anomaly It refers to the sparsely distributed sea surface height anomaly product, which mainly reflects information such as ocean geostrophic currents and mesoscale eddies.

[0224] Assuming the reflecting surface is the ice surface, the elevation information also needs to be adjusted to subtract the effects of solid tides, polar tides, etc., on the ice sheet elevation to obtain the net height of the ice surface relative to the reference ellipsoid. H ice ， Because GNSS satellites operate in the L-band and have strong penetrating power, the reflected signals from them on the ice surface mainly originate from the lower surface of the ice. Therefore, the height of the ice surface relative to the reference ellipsoid primarily refers to the net height of the lower ice surface relative to the reference ellipsoid. Sea ice floats in the seawater and follows Archimedes' principle of buoyancy; the submersion height of the ice shelf or sea ice (the portion of the ice surface submerged below the water surface) is... F ) and its thickness T ice There is a definite relationship. Specifically, we can assume that the local sea level is known. SSH local (This information can be obtained from observations or models of nearby ice-free sea areas), calculate the height of the subglacial surface relative to the sea surface above it, i.e., the submersion height. F = SSH local H ice Next, according to the buoyancy formula:

[0225]

[0226] in, ρ sw It is the density of seawater (approximately 1024 kg / m³). ρ ice It is the density of sea ice (approximately 915 kg / m³), Δ snow This is a correction term that takes snow cover into account. Finally, the calculated sea ice thickness... T ice Sparse strip products are formed along the trajectory.

[0227] In addition, for the dual-frequency observation data of the receiver and Its inversion principle can be derived from the ionospheric delay Δ ρ ion and total electron content (TEC) and signal frequency along the path f The relationship is:

[0228]

[0229] In this case, ignoring other error differences, the difference in time delay between the two frequency observations can mainly be attributed to the ionospheric delay difference, as shown in the following formula:

[0230]

[0231] Wherein, α can be a known constant, and this invention does not impose any restrictions on it.

[0232] Based on the above process, the oblique total electron content (STEC) along the signal propagation path can be obtained:

[0233]

[0234] Furthermore, by multiplying by a tilt factor, it can be converted into the total electron content (VTEC) in the zenith direction. Ultimately, a high spatiotemporal resolution ionospheric VTEC sparse data product distributed along the observation strip can be obtained. Understandably, this reflects the unique capability of the BeiDou interferometric altimeter to simultaneously invert ocean and space environment parameters.

[0235] Step 105: Obtain the spatiotemporal variation characteristics corresponding to the marine environmental parameters, determine the data collection strategy corresponding to the spatiotemporal variation characteristics, collect the marine environmental parameters according to the data collection strategy, and generate a continuously covered wide-swath imaging data product through spatial interpolation reconstruction.

[0236] Through the process described in the foregoing embodiments, sparse and discontinuous marine environmental parameters can be obtained. In the embodiments of the present invention, the spatiotemporal variation characteristics corresponding to the marine environmental parameters can be further obtained, and a data collection strategy corresponding to the spatiotemporal variation characteristics can be determined. The marine environmental parameters are collected according to the data collection strategy, and a continuous wide-swath imaging data product is generated through spatial interpolation reconstruction. Thus, by utilizing the correlation between marine parameters in time and space, sparse orbital data from multiple orbits and multiple days can be "woven" into a complete image.

[0237] Different parameters exhibit drastically different patterns of change, necessitating a data processing strategy that is "tailored to the specific parameters," meaning that a matching data processing strategy must be selected based on the characteristics of the data. Spatiotemporal variation characteristics can be categorized into time-varying and space-varying characteristics. Time-varying characteristics refer to the rate and magnitude of change in the value of a target environmental parameter (such as sea level height, ionospheric TEC, etc.) over time at a specific spatial point. This can be used to measure the speed of parameter change; strong time-varying characteristics mean that the parameter will fluctuate significantly in a short period (e.g., minutes, hours); weak time-varying characteristics mean that the parameter remains relatively stable over a longer period (e.g., days, weeks). Space-varying characteristics refer to the gradient and structure of the change in the value of a target environmental parameter within a spatial range at a specific moment. This can be used to measure the degree of spatial non-uniformity of the parameter; strong space-varying characteristics mean that the parameter exhibits significant differences over short distances (e.g., tens of kilometers); weak space-varying characteristics mean that the parameter is evenly distributed and changes slowly over a large area (e.g., hundreds of kilometers).

[0238] For example, highly time-varying parameters may include the total electron content (TEC) of the ionosphere, which is driven by solar radiation and geomagnetic activity and can change dramatically within minutes, similar to weather changes. Weakly time-varying parameters may include sea surface height anomalies (SSHA), dominated by dynamic processes such as ocean circulation and eddies; a mesoscale eddy can have a lifespan of several weeks, changing relatively slowly, similar to climate change. Correspondingly, highly space-varying parameters may include sea surface height anomalies (SSHA), where the height field can change dramatically within tens of kilometers (tens of centimeters) at ocean fronts, eddy edges, etc., exhibiting large spatial gradients; while weakly space-varying parameters may include ionospheric TEC, which typically exhibits a large-scale smooth structure on a scale of hundreds of kilometers, with relatively gentle spatial changes except in equatorial anomaly regions or polar regions.

[0239] In the above process, time-varying characteristics are the key factor in determining the size of the data aggregation time window. For parameters with strong time-varying characteristics, a small time window must be used to aggregate data to avoid blurring transient signals at different times; for parameters with weak time-varying characteristics, a large time window can be used to aggregate more data to increase the sampling density of spatial interpolation. Correspondingly, spatial-varying characteristics are the key factor in determining the size of the data aggregation spatial window. For parameters with strong spatial-varying characteristics, a small spatial window must be used to aggregate data to avoid forcibly mixing signals with vastly different spatial structures, leading to interpolation distortion; for parameters with weak spatial-varying characteristics, a large spatial window can be used to aggregate more data to fill spatial gaps and obtain more stable interpolation results.

[0240] Based on the above process, for marine environmental parameters that vary slowly in time but are highly spatially variable, the first strategy is adopted, which involves using a large time window and a small spatial window to collect data; for atmospheric environmental parameters that vary rapidly in time but are relatively weakly spatially variable, the second strategy is adopted, which involves using a small time window and a large spatial window to collect data.

[0241] The larger time window is the first duration, and the smaller spatial window is the range of Earth's latitude and longitude n degrees; the smaller time window is the second duration, and the larger spatial window is the range of Earth's latitude and longitude m degrees; the first duration is greater than the second duration; n and m are both positive integers, and the value of m is greater than the value of n.

[0242] In some examples, for Strategy 1 (used for SSHA and SIT (Sea Ice Thickness)): a large time window and a small spatial window. Example parameters: time window = 7 days; spatial window = a rectangular area of ​​2 degrees latitude and longitude (approximately 200km × 200km, low latitude). Specifically, for a target grid point, all SSHA or SIT observation data within a 2-degree × 2-degree range centered on the target grid point are collected over the past 7 days, forming a "data pool" for interpolation at that point.

[0243] For Strategy 2 (for ionospheric TEC): small time window, large spatial window. Example parameters: time window = 1 minute; spatial window = a rectangular area with 5 degrees latitude and longitude (approximately 550km × 550km, low latitude). Specifically, for the target grid point, collect all TEC observation data within 30 seconds before and after the current time, where all ground trajectories fall within a 5-degree × 5-degree range, forming a "data pool".

[0244] Furthermore, after data aggregation using appropriate strategies, Kriging interpolation can be employed to spatially interpolate the sparse strip data, generating a continuously covered, wide-swath imaging data product. Kriging interpolation can be a geostatistical interpolation method, which not only considers the distance between data points and the points to be estimated but also quantifies the spatial correlation structure of the data itself through a variogram, thus providing the optimal linear unbiased estimate.

[0245] In a specific implementation, the process of Kriging space interpolation may include:

[0246] 1. Construct a data pool: For each regular grid point to be interpolated x 0. Select the corresponding spatiotemporal aggregation strategy based on the type of target parameter (sea surface height anomaly, sea ice thickness, or ionospheric TEC). Within the selected spatiotemporal window, aggregate all raw sparse strip observation data falling within that window to form the data pool corresponding to that grid point. Z ( x i ), i =1,2,...,n}. Where, Z ( x i ) represents the position of the i-th observation point. x i The observed parameter values ​​at that location.

[0247] 2. Modeling spatial correlation (variance function analysis):

[0248] Calculate the semivariance between all pairs of observations in the data pool. γ (h ij ),in h ij It is a point x i and x j The spatial distance between them. Based on the calculations. γ (h) and h The scatter plot (i.e., the experimental variation function) is fitted with a continuous theoretical variation function model. γ model ( h Examples of models include the spherical model or the exponential model. This model quantitatively describes how the spatial autocorrelation of parameters decays with distance and is the core of Kriging interpolation.

[0249] 3. Solving for Kriging weights: Based on the fitted variation function model γ model ( h (), which is the current point to be estimated. x 0. Establish the Kriging equations. By solving these equations, the data for each known observation point in the data pool is obtained. x i Treatment of estimation x Contribution weight of 0 λ i These weights not only reflect geometric distance, but more importantly, incorporate spatial structure information of the data, ensuring the optimality of the interpolation.

[0250] 4. Calculate the estimated value and assess the uncertainty:

[0251] Grid points x Parameter estimate at 0 Calculated by weighted sum of known observations:

[0252]

[0253] At the same time, the Kriging method can also provide the Kriging variance of this estimate. This serves as a quantitative assessment of the uncertainty of the interpolation results.

[0254] Through the above process, Kriging interpolation can effectively utilize the spatial statistical characteristics of data, avoiding the generation of unrealistic "bull's-eye" contour patterns in sparse data areas. The generated two-dimensional field is smoother and more continuous in space, and has clear physical statistical significance. It is suitable for processing geophysical parameters with strong spatial correlation, such as sea surface height field and ice thickness field.

[0255] Furthermore, by repeating the above interpolation process for all regular grid points, the originally sparse and discontinuous strip data can be filled into a continuous two-dimensional image covering the entire area. The final product can be output in a standard Geographic Information System (GIS) format, such as GeoTIFF or NetCDF, where each pixel value represents sea surface height anomalies, sea ice thickness, or ionospheric TEC at that location.

[0256] For example, multiple sparse SSHA orbital data, after being aggregated over 7 days / 2 degrees and interpolated using Kriging, generated a continuous color image of sea surface height anomalies covering a portion of the Northwest Pacific. The image clearly shows the structure of a warm eddy (red, sea surface bulge) and a cold eddy (blue, sea surface depression), which cannot be visually displayed at all by the original strip data.

[0257] It should be noted that the embodiments of the present invention include, but are not limited to, the examples described above. It is understood that those skilled in the art can make further settings according to actual needs under the guidance of the ideas in the embodiments of the present invention, and the present invention does not limit such settings.

[0258] In this embodiment of the invention, calculations are performed based on the precise ephemeris of navigation satellites, precise orbit determination data from receivers, and a reference sea surface height model to determine the theoretical value of the time delay difference interferometric geometry between the direct and reflected signals of GNSS-R. Error correction processing is then performed on the original interferometric signal received by the receiver corresponding to the reflecting surface to obtain the measured value of the time delay difference. Then, based on the difference between the theoretical and measured values ​​of the time delay difference interferometric geometry, the elevation information between the reflecting surface and the reference sea surface height model is calculated. Based on this elevation information, inversion is performed to obtain at least two sparsely distributed marine environmental parameters, and the spatiotemporal variation characteristics corresponding to these parameters are acquired. A data collection strategy corresponding to these spatiotemporal variation characteristics is then determined, and the data is collected according to the established data collection strategy. This approach aggregates marine environmental parameters and reconstructs them through spatial interpolation to generate continuously covered wide-swath imaging data products. This establishes a complete and rigorous data processing chain. By precisely solving the time delay difference interferometric geometric model and correcting for measured time delay errors, it significantly reduces systematic errors in the conversion process from raw signals to geophysical parameters, improving the accuracy and reliability of the final retrieved parameters. Furthermore, based on the adaptive data aggregation strategy of parameter spatiotemporal transformation characteristics and the spatial interpolation reconstruction process, discrete strip data are intelligently "woven" into continuously covered wide-swath imaging data products. This makes the data format more suitable for the analytical needs of fields such as oceanography and climatology, enhancing the intuitiveness and usability of the products.

[0259] To enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention, the following examples are provided for illustrative purposes:

[0260] As an example, refer to Figure 2 The flowchart of high-precision imaging data processing provided in the embodiments of the present invention is shown. The formulas involved can be referred to the description in the foregoing embodiments, and will not be repeated here. Specifically, the corresponding process may include:

[0261] (I) Calculation of sea surface mirror reflection points and time delay difference geometric model based on GNSS precise ephemeris and precise orbit:

[0262] (1) such as Figure 3 The diagram illustrates an interferometric geometry model provided in this embodiment of the invention. Based on the original onboard observation time, and combining the receiver's precise orbit determination data with the GNSS satellite SP3 precise ephemeris, the receiver's centroid at the time of the reflection event is determined by Lagrange interpolation. R With GNSS satellite position T Correspondingly, receiver mirror R1 and receiver mirror R2 are the mirror points formed by the sea surface on the receiver position, used to simplify the geometric relationship of the reflection path.

[0263] (2) Using the WGS84 ellipsoid as the initial sea surface height model, calculate the sea surface mirror reflection point according to Fermat's law. O .

[0264] (3) Superimpose sea surface mirror reflection points onto the initial sea surface height model. O The mean sea level and geophysical correction at the location are used to iteratively repeat steps (1)-(2) until the change in the position of the reflection point is less than 1 cm, and finally the position is determined. R , T , O Three-dimensional coordinates. Where R... TR R is the distance between the receiver R and the GNSS satellite T. RO For the receiver and the mirror reflection point of the sea surface O The distance between them, R TO GNSS satellite T and sea surface mirror reflection point O The distance between them. Correspondingly, the specular reflection point of the sea surface in the initial sea surface height model is... O The specular reflection point on the actual sea surface is... S .

[0265] (4) Based on the satellite attitude data and coordinate system transformation matrix, calculate the phase center position of the direct / reflected antenna according to formula (1).

[0266] (5) Using the phase center of the direct / reflective antenna and the position of the GNSS satellite T and the location of the reflection point O The time delay difference interference geometric theoretical value Δ is calculated according to formula (2). ρ g .

[0267] (II) Calculation of measured time delay difference based on the interferometric waveform re-tracking algorithm of Beidou interferometric altimeter:

[0268] (1) The measured dual-frequency interferometric waveform of the Beidou interferometric altimeter was noncoherently accumulated, denoised and normalized, and the observation delay of the mirror reflection point relative to the waveform zero point was extracted by waveform matching method.

[0269] (2) The observation delay and the predicted value of the zero value of the waveform output by the receiver are added together according to formula (3) to obtain the measured value of the delay difference.

[0270] (3) After the measured time delay difference is divided with the interferometric geometric model value, it is filtered by a Butterworth filter and then reconstructed with the model value to obtain the filtered measured time delay difference.

[0271] (4) Use the time delay difference after dual-frequency filtering to perform dual-frequency combination inversion to obtain sparse strip distribution ionospheric VTEC products.

[0272] (5) The measured value of the filtered time delay difference is corrected in sequence according to formula (4) for hardware delay, antenna phase center time delay deviation, sea state deviation, ionospheric delay and tropospheric delay, so as to obtain the accurate direct-reflection signal propagation time delay difference.

[0273] (III) Calculation of sea surface height, sea ice thickness, and ionospheric TEC parameters corresponding to the latitude and longitude of two-dimensional sparse stripes based on time delay difference:

[0274] (1) The measured value of the time delay difference after error correction and the value of the interferometric geometric model are calculated according to formula (5) to obtain the instantaneous elevation of the reflecting surface. Then, the sea surface height model value is added to obtain the final elevation value of the reflecting surface. .in, The target angle is the angle between the incident signal path of the navigation satellite signal at the sea surface mirror reflection point on the reference sea surface height model and the direction of the normal to the reflecting surface.

[0275] (2) Sea surface scene: Instantaneous elevation is corrected for ocean tides, polar tides, solid tides, and atmospheric inversion, and sparse strip sea surface height products are obtained, such as Figure 4 As shown.

[0276] (3) Ice surface scenario: After geophysical correction of instantaneous elevation, the thickness of sparse strip sea ice is inverted based on the law of buoyancy, and compared with... Figure 4 The distributions are similar.

[0277] (iv) Data aggregation with high spatiotemporal correlation and Kriging interpolation to generate two-dimensional wide-swath imaging data products:

[0278] (1) For datasets showing temporal weakening and spatial strengthening of anomalies such as sea surface height and sea ice thickness, a large time window and a small spatial window are used for data aggregation. In this case, a 7-day time window and a 2-degree spatial window of Earth's latitude and longitude are used for data aggregation. Wide-swath imaging products are generated through Kriging interpolation, such as... Figure 5 As shown.

[0279] (2) For datasets like VTEC, which are time-varying and space-varying, small time windows and large spatial windows are used for data aggregation. In this case, a 15-minute time window and a 5° latitude and longitude spatial window are used for data aggregation, and wide-span imaging products are generated by Kriging interpolation.

[0280] Through the above process, a complete and rigorous data processing chain was constructed. By precisely solving the time delay difference interferometric geometric model and correcting the measured time delay difference error, the systematic error in the conversion process from the original signal to geophysical parameters was significantly reduced, improving the accuracy and reliability of the parameters obtained in the final inversion. Furthermore, based on the adaptive data collection strategy of parameter spatiotemporal transformation characteristics and the spatial interpolation reconstruction process, discrete strip data were intelligently "woven" into a continuous wide-swath imaging data product, making the data format more in line with the analytical needs of fields such as oceanography and climatology, and improving the intuitiveness and usability of the product.

[0281] It should be noted that, for the sake of simplicity, the method embodiments are all described as a series of actions. However, those skilled in the art should understand that the embodiments of the present invention are not limited to the described order of actions, because according to the embodiments of the present invention, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions involved are not necessarily essential to the embodiments of the present invention.

[0282] Reference Figure 6 The diagram illustrates a structural block diagram of a BeiDou interferometric altimeter marine multi-parameter wide-swath imaging data processing system provided in an embodiment of the present invention, which may specifically include the following modules:

[0283] The calculation module 601 is used to perform calculations based on the precise ephemeris of navigation satellites, the precise orbit determination data of receivers, and the reference sea surface height model to determine the theoretical value of the time delay difference interference geometry between the direct and reflected signals of GNSS-R.

[0284] The correction module 602 is used to perform error correction processing on the original interference signal received by the receiver and corresponding to the reflecting surface, and obtain the measured value of the time delay difference;

[0285] The elevation calculation module 603 is used to calculate the elevation information between the reflecting surface and the reference sea surface height model based on the difference between the theoretical value of the time delay difference interferometric geometry and the measured value of the time delay difference.

[0286] Inversion module 604 is used to perform inversion based on elevation information to obtain at least two marine environmental parameters with sparse strip distribution;

[0287] The imaging module 605 is used to acquire the spatiotemporal variation characteristics corresponding to the marine environmental parameters, determine the data collection strategy corresponding to the spatiotemporal variation characteristics, collect the marine environmental parameters according to the data collection strategy, and generate a continuously covered wide-swath imaging data product through spatial interpolation reconstruction.

[0288] In some feasible implementations, the solution module is specifically used for:

[0289] Acquire precise ephemeris data of navigation satellites, precise orbit determination data from receivers, and reference sea surface height models;

[0290] The original observation time on the satellite is determined, and interpolation is performed using the original observation time, the precise ephemeris, and the precise orbit determination data to determine the position of the receiver platform centroid and the position of the navigation satellite at the moment of the reflection event.

[0291] Using the reference sea surface height model as the initial reflecting surface, the sea surface mirror reflection point is calculated iteratively;

[0292] The theoretical value of the time delay difference interference geometry between the direct and reflected signals of GNSS-R is obtained by calculating the centroid position of the receiver platform, the position of the navigation satellite, and the sea surface mirror reflection point.

[0293] In some feasible implementations, the solution module is specifically used for:

[0294] Using the reference sea surface height model as the initial reflecting surface, iterative calculations are performed based on Fermat's principle, and the elevation value of the reference sea surface height model is updated in each iteration until the position change of the calculated sea surface mirror reflection point is less than a preset threshold, thus obtaining the sea surface mirror reflection point at the end of the iterative calculation.

[0295] In some feasible implementations, the receiver includes at least a direct receiving antenna and a reflective receiving antenna, and the calculation module is specifically used for:

[0296] Acquire the satellite attitude data of the receiver;

[0297] Determine the coordinate system transformation relationship corresponding to the satellite attitude data;

[0298] Using the coordinate system transformation relationship, the phase center position of the direct receiving antenna and the phase center position of the reflective receiving antenna are calculated.

[0299] Using the navigation satellite position, the phase center position of the direct antenna, the phase center position of the reflective receiving antenna, and the sea surface mirror reflection point, the time delay difference interference geometric theoretical value between the direct signal received by the direct receiving antenna and the reflected signal received by the reflective receiving antenna is calculated.

[0300] In some feasible implementations, the solution module is specifically used to solve the problem using the following formula:

[0301]

[0302] Among them, the The position of the phase center of the direct receiving antenna or the phase center of the reflected receiving antenna in the satellite's coordinate system, obtained from ground measurements before satellite launch. The transformation matrix between the satellite body coordinate system and the satellite orbit coordinate system is described below. This is the transformation matrix between the satellite orbit coordinate system and the reference ellipsoid coordinate system.

[0303] In some feasible implementations, the correction module is specifically used for:

[0304] The initial time delay difference estimate is extracted from the original interference signal;

[0305] The initial time delay difference estimate is compensated and filtered by the interference waveform time delay measurement value to obtain the target time delay difference observation value;

[0306] For the target time delay difference observation value, hardware time delay deviation correction, antenna phase center time delay deviation correction, sea state deviation correction, ionospheric propagation delay correction and tropospheric propagation delay correction are performed in sequence to obtain the corresponding measured time delay difference value.

[0307] In some feasible implementations, the correction module is specifically used to compensate for and filter the time delay measurement of the interference waveform using the following formula:

[0308]

[0309] Among them, the For the target time delay difference observation value, the It is the impulse response function of the filter, the The estimated initial time delay difference value for the receiver, the This indicates the time delay difference compensation value obtained by using the waveform re-tracking method to measure the interferometric measured waveform.

[0310] In some feasible implementations, the correction module is specifically used to perform correction using the following formula:

[0311]

[0312] Among them, the This is the measured value of the time delay difference after error correction. For the target time delay difference observation value This is the receiver hardware delay correction amount. This is the time delay correction for sea state deviation. This is the time delay correction amount for antenna phase center error. This is the correction amount for ionospheric time delay deviation. This is the correction amount for tropospheric time delay deviation.

[0313] In some feasible implementations, the elevation information calculation module is specifically used for:

[0314] Obtain the angle between the incident signal path of the navigation satellite signal at the sea surface mirror reflection point on the reference sea surface height model and the target angle in the direction of the normal to the reflecting surface;

[0315] The elevation information of the reflecting surface relative to the reference sea surface height model is obtained by using the difference between the theoretical value of the time delay difference interferometric geometry and the measured value of the time delay difference, as well as the included angle of the target.

[0316] In some feasible implementations, the elevation information calculation module is specifically used to calculate the elevation information using the following formula:

[0317]

[0318] Among them, the The time delay difference interferometric geometric model value, the The measured value of the time delay difference, the The included angle of the target is denoted as .

[0319] In some feasible implementations, the inversion module is specifically used for:

[0320] When the reflecting surface is the sea surface, the elevation information is corrected for ocean tides, polar tides, solid earth tides, and atmospheric inversion to obtain the sea surface height or sea surface height anomaly with sparse strip distribution.

[0321] And / or, when the reflecting surface is an ice surface, the elevation information is geophysically corrected, and the thickness of the sparsely distributed sea ice is obtained by inversion according to the law of buoyancy.

[0322] And / or, acquire dual-frequency observation data from the receiver, perform dual-frequency combination inversion on the dual-frequency observation data, and obtain the total electron content of the ionosphere with sparse strip distribution.

[0323] In some feasible implementations, the imaging module is specifically used for:

[0324] For marine environmental parameters that vary slowly in time but are highly spatially variable, the first strategy is adopted, which involves using a large time window and a small spatial window to collect data.

[0325] For atmospheric environmental parameters that vary rapidly in time and have weak spatial variation, a second strategy is adopted, which involves using a small time window and a large spatial window to collect data.

[0326] In some feasible implementations, the large time window is a first duration, and the small spatial window is a range of n degrees of latitude and longitude on Earth.

[0327] The smaller time window is the second duration, and the larger spatial window is the range of Earth's latitude and longitude in m degrees.

[0328] Wherein, the first duration is greater than the second duration; n and m are both positive integers, and the value of m is greater than the value of n.

[0329] In some feasible implementations, the imaging module is specifically used for:

[0330] Using a Kriging interpolation device, spatial interpolation is performed on the sparse strip data collected by the aforementioned data aggregation strategy to generate a continuously covered wide-swath imaging data product.

[0331] As the system implementation is basically similar to the method implementation, it is described in a relatively simple way. For relevant details, please refer to the description of the method implementation.

[0332] In addition, this invention also provides an electronic device, including: a processor, a memory, and a computer program stored in the memory and executable on the processor. When the computer program is executed by the processor, it implements the various processes of the above-described Beidou interferometric altimeter marine multi-parameter wide-swath imaging data processing method embodiment and achieves the same technical effect. To avoid repetition, it will not be described again here.

[0333] This invention also provides a computer-readable storage medium storing a computer program. When executed by a processor, the computer program implements the various processes described in the embodiments of the BeiDou interferometric altimeter marine multi-parameter wide-swath imaging data processing method, achieving the same technical effects. To avoid repetition, it will not be described again here. The computer-readable storage medium may be a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk, etc.

[0334] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0335] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, embodiments of the present invention can take the form of entirely hardware embodiments, entirely software embodiments, or embodiments combining software and hardware aspects. Furthermore, embodiments of the present invention can take the form of computer program products implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, EEPROM, Flash, and eMMC, etc.) containing computer-usable program code.

[0336] Embodiments of the present invention are described with reference to flowchart illustrations and / or block diagrams of methods, terminal devices (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing terminal device to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing terminal device, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure One One or more processes and / or boxes Figure One A system that specifies functions in one or more boxes.

[0337] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing terminal device to operate in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including an instruction set implemented in a process. Figure One One or more processes and / or boxes Figure One The function specified in one or more boxes.

[0338] These computer program instructions can also be loaded onto a computer or other programmable data processing terminal equipment, causing a series of operational steps to be performed on the computer or other programmable terminal equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable terminal equipment for implementing the process. Figure One One or more processes and / or boxes Figure One The steps of the function specified in one or more boxes.

[0339] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present invention.

[0340] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes said element.

[0341] The foregoing has provided a detailed description of a wide-swath imaging data processing method and a wide-swath imaging data processing system for multiple parameters of a BeiDou interferometric altimeter in the ocean, as provided by this invention. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A method for processing wide-swath imaging data of multiple parameters in the ocean using a BeiDou interferometric altimeter, characterized in that, include: Based on the precise ephemeris of navigation satellites, the precise orbit determination data of receivers, and the reference sea surface height model, the theoretical value of the time delay difference interferometric geometry between the direct and reflected signals of GNSS-R is determined. The original interference signal received by the receiver and corresponding to the reflecting surface is subjected to error correction processing to obtain the measured value of the time delay difference; Based on the difference between the theoretical value of the time delay difference interferometric geometry and the measured value of the time delay difference, the elevation information between the reflecting surface and the reference sea surface height model is calculated. Inversion based on elevation information yields at least two marine environmental parameters with sparse strip distribution; The spatiotemporal variation characteristics of the marine environmental parameters are obtained, and a data collection strategy corresponding to the spatiotemporal variation characteristics is determined. The marine environmental parameters are collected according to the data collection strategy, and a continuously covered wide-swath imaging data product is generated through spatial interpolation reconstruction.

2. The method according to claim 1, characterized in that, The method utilizes precise ephemeris data from navigation satellites, precise orbit determination data from receivers, and a reference sea level model to calculate and determine the theoretical value of the time delay difference interferometric geometry between the direct and reflected signals of GNSS-R, including: Acquire precise ephemeris data of navigation satellites, precise orbit determination data from receivers, and reference sea surface height models; The original observation time on the satellite is determined, and interpolation is performed using the original observation time, the precise ephemeris, and the precise orbit determination data to determine the position of the receiver platform centroid and the position of the navigation satellite at the moment of the reflection event. Using the reference sea surface height model as the initial reflecting surface, the sea surface mirror reflection point is calculated iteratively; The theoretical value of the time delay difference between the direct and reflected signals of GNSS-R is obtained by calculating the centroid position of the receiver platform, the position of the navigation satellite, and the sea surface mirror reflection point.

3. The method according to claim 2, characterized in that, The step of iteratively calculating the specular reflection point of the sea surface using the reference sea surface height model as the initial reflecting surface includes: Using the reference sea surface height model as the initial reflecting surface, iterative calculations are performed based on Fermat's principle, and the elevation value of the reference sea surface height model is updated in each iteration until the position change of the calculated sea surface mirror reflection point is less than a preset threshold, thus obtaining the sea surface mirror reflection point at the end of the iterative calculation.

4. The method according to claim 2 or 3, characterized in that, The receiver includes at least a direct receiving antenna and a reflected receiving antenna. The calculation, based on the centroid position of the receiver platform, the position of the navigation satellite, and the specular reflection point on the sea surface, yields the theoretical interferometric value of the time delay difference between the direct and reflected signals of GNSS-R, including: Acquire the satellite attitude data of the receiver; Determine the coordinate system transformation relationship corresponding to the satellite attitude data; Using the coordinate system transformation relationship, the phase center position of the direct receiving antenna and the phase center position of the reflective receiving antenna are calculated. Using the navigation satellite position, the phase center position of the direct antenna, the phase center position of the reflective receiving antenna, and the sea surface mirror reflection point, the time delay difference interference geometric theoretical value between the direct signal received by the direct receiving antenna and the reflected signal received by the reflective receiving antenna is calculated.

5. The method according to claim 4, characterized in that, The coordinate system transformation relationship is used to calculate the phase center positions of the direct receiving antenna and the reflective receiving antenna, based on the following formula: Among them, the The position of the phase center of the direct receiving antenna or the phase center of the reflected receiving antenna in the satellite's coordinate system, obtained from ground measurements before satellite launch. The transformation matrix between the satellite body coordinate system and the satellite orbit coordinate system is described below. This is the transformation matrix between the satellite orbit coordinate system and the reference ellipsoid coordinate system.

6. The method according to claim 1, characterized in that, The step of performing error correction processing on the original interference signal received by the receiver and corresponding to the reflecting surface to obtain the measured value of the time delay difference includes: The initial time delay difference estimate is extracted from the original interference signal; The initial time delay difference estimate is compensated and filtered by the interference waveform time delay measurement value to obtain the target time delay difference observation value; For the target time delay difference observation value, hardware time delay deviation correction, antenna phase center time delay deviation correction, sea state deviation correction, ionospheric propagation delay correction and tropospheric propagation delay correction are performed in sequence to obtain the corresponding measured time delay difference value.

7. The method according to claim 6, characterized in that, The initial time delay difference estimate is compensated by the time delay measurement value of the interferometric waveform and then filtered to obtain the target time delay difference observation value. The interferometric waveform time delay measurement value compensation and filtering are performed using the following formula: Among them, the For the target time delay difference observation value, the It is the impulse response function of the filter, the The estimated initial time delay difference value for the receiver, the This indicates the time delay difference compensation value obtained by using the waveform re-tracking method to measure the interferometric measured waveform.

8. The method according to claim 6 or 7, characterized in that, The observed target time delay difference is sequentially corrected for hardware time delay deviation, antenna phase center time delay deviation, sea state deviation, ionospheric propagation delay, and tropospheric propagation delay to obtain the corresponding measured time delay difference value, which is then corrected using the following formula: Among them, the This is the measured value of the time delay difference after error correction. For the target time delay difference observation value, This is the receiver hardware delay correction amount. This is the time delay correction for sea state deviation. This is the time delay correction amount for antenna phase center error. This is the correction amount for ionospheric time delay deviation. This is the correction amount for tropospheric time delay deviation.

9. The method according to claim 2, characterized in that, The step of calculating the elevation information of the reflecting surface relative to the reference sea surface height model based on the difference between the theoretical value of the time delay difference interferometric geometry and the measured value of the time delay difference includes: Obtain the angle between the incident signal path of the navigation satellite signal at the sea surface mirror reflection point on the reference sea surface height model and the target angle in the direction of the normal to the reflecting surface; The elevation information of the reflecting surface relative to the reference sea surface height model is obtained by using the difference between the theoretical value of the time delay difference interferometric geometry and the measured value of the time delay difference, as well as the included angle of the target.

10. The method according to claim 9, characterized in that, The elevation information of the reflecting surface relative to the reference sea surface height model is obtained by using the difference between the theoretical value of the time delay difference interferometric geometry and the measured value of the time delay difference, as well as the target angle, and is calculated using the following formula: Among them, the The time delay difference interferometric geometric model value, the The measured value of the time delay difference, the The included angle of the target is denoted as .

11. The method according to claim 1, characterized in that, The inversion based on elevation information yields at least two marine environmental parameters with sparse strip distribution, including: When the reflecting surface is the sea surface, the elevation information is corrected for ocean tides, polar tides, solid earth tides, and atmospheric inversion to obtain the sea surface height or sea surface height anomaly with sparse strip distribution. And / or, when the reflecting surface is an ice surface, the elevation information is geophysically corrected, and the thickness of the sparsely distributed sea ice is obtained by inversion according to the law of buoyancy. And / or, acquire dual-frequency observation data from the receiver, perform dual-frequency combination inversion on the dual-frequency observation data, and obtain the total electron content of the ionosphere with sparse strip distribution.

12. The method according to claim 1, characterized in that, The method for determining the data collection strategy corresponding to the spatiotemporal variation characteristics includes: For marine environmental parameters that vary slowly in time but are highly spatially variable, the first strategy is adopted, which involves using a large time window and a small spatial window to collect data. For atmospheric environmental parameters that vary rapidly in time and have weak spatial variation, a second strategy is adopted, which involves using a small time window and a large spatial window to collect data.

13. The method according to claim 12, characterized in that, The large time window is the first duration, and the small spatial window is the range of Earth's latitude and longitude n degrees. The smaller time window is the second duration, and the larger spatial window is the range of Earth's latitude and longitude in m degrees. Wherein, the first duration is greater than the second duration; n and m are both positive integers, and the value of m is greater than the value of n.

14. The method according to claim 1, characterized in that, The process of collecting marine environmental parameters according to the aforementioned data collection strategy and generating a continuously covered wide-swath imaging data product through spatial interpolation reconstruction includes: The Kriging interpolation method is used to perform spatial interpolation on the sparse strip data collected by the data aggregation strategy to generate a continuously covered wide-span imaging data product.

15. A wide-swath imaging data processing system for multi-parameter marine imaging using a BeiDou interferometric altimeter, characterized in that, include: The calculation module is used to calculate the theoretical value of the time delay difference interference geometry between the direct and reflected signals of GNSS-R based on the precise ephemeris of navigation satellites, the precise orbit determination data of receivers, and the reference sea surface height model. The correction module is used to perform error correction processing on the original interference signal received by the receiver and corresponding to the reflecting surface, and obtain the measured value of the time delay difference; The elevation calculation module is used to calculate the elevation information between the reflecting surface and the reference sea surface height model based on the difference between the theoretical value of the time delay difference interferometric geometry and the measured value of the time delay difference. The inversion module is used to perform inversion based on elevation information to obtain at least two marine environmental parameters with sparse strip distribution; The imaging module is used to acquire the spatiotemporal variation characteristics corresponding to the marine environmental parameters, determine the data collection strategy corresponding to the spatiotemporal variation characteristics, collect the marine environmental parameters according to the data collection strategy, and generate a continuously covered wide-swath imaging data product through spatial interpolation reconstruction.

16. An electronic device, characterized in that, It includes a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other through the communication bus; The memory is used to store computer programs; When the processor executes a program stored in the memory, it implements the method as described in any one of claims 1-14.

17. A computer-readable storage medium having instructions stored thereon that, when executed by one or more processors, cause the processors to perform the method as described in any one of claims 1-14.

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