On-orbit geometric verification methods, devices, equipment, and media for satellite altimetry data

Abstract

This disclosure provides an on-orbit geometric verification method, apparatus, equipment, and medium for satellite altimetry data. The method includes: screening the validity of multiple buoys in a buoy array to identify multiple target buoys; forming target buoy pairs from any two target buoys; determining the double-difference residual corresponding to each target buoy pair; determining the semi-variable value corresponding to the baseline length between the two target buoys in each target buoy pair, based on the number of target buoy pairs matching the baseline length and the double-difference residual corresponding to the target buoy pairs matching the baseline length; and separating the variance of the satellite instrument's background noise and the variance of the geophysical environment error based on each baseline length and the corresponding semi-variable value, thereby achieving variance coupling and accurately determining the satellite instrument's background noise and improving the accuracy of the verification results.

Description

Technical Field

[0001] This disclosure relates to the field of satellite remote sensing data processing technology, and more specifically, to an on-orbit geometric verification method, apparatus, equipment, and medium for satellite altimetry data. Background Technology

[0002] Ocean science research has expanded from large-scale circulation to mesoscale and sub-mesoscale dynamics, leading to the emergence of a new generation of wide-swath satellite altimetry technology. Represented by surface water and ocean topography satellites, these satellites, equipped with Ka-band radar interferometers, can achieve two-dimensional sea surface height observations with a 120km wide swath and resolutions of 2km and even 250m. To ensure the accuracy and reliability of satellite altimetry, on-orbit geometric verification of the data is necessary.

[0003] In-orbit geometric verification of satellite altimetry data often relies on long-term maintained ground verification fields, mostly employing a nadir point model. This involves comparing the instantaneous altitude of the satellite at its overhead position using tide gauge stations or individual GNSS buoys. However, this method cannot distinguish between satellite instrument background noise and geophysical environmental errors, resulting in significant uncertainty in the verification results. Consequently, even valid satellite altimetry data can be incorrectly classified as invalid. Summary of the Invention

[0004] This disclosure provides at least one method, apparatus, device, and medium for on-orbit geometric verification of satellite altimetry data. It employs a buoy array and separates the variance of satellite instrument background noise and the variance of geophysical environmental error through double-difference processing and semi-variance analysis, thereby improving the accuracy of the verification results.

[0005] Specifically, this application is implemented through the following technical solution:

[0006] According to a first aspect of this application, an on-orbit geometric verification method for satellite altimetry data is provided, the method comprising: For each buoy in the buoy array, based on buoy observation data from the observation equipment installed on the buoy, multiple sea surface heights corresponding to the buoy are determined, and based on the sea surface height observation data along the orbit of the target satellite, the satellite observation sea surface height corresponding to the buoy is determined. Based on the satellite observation time and buoy observation time corresponding to each buoy, the effectiveness of multiple buoys is screened to determine multiple target buoys, and any two target buoys are paired to form a target buoy pair. For each target buoy pair, the double-difference residual corresponding to the target buoy pair is determined based on the satellite-observed sea surface height and the buoy-observed sea surface height corresponding to each target buoy in the target buoy pair; the buoy-observed sea surface height is determined based on multiple observed sea surface heights corresponding to the target buoy. For the baseline length between the two target buoys in each target buoy pair, the semi-variance value corresponding to the baseline length is determined based on the number of target buoy pairs that match the baseline length and the double-difference residuals corresponding to the target buoy pairs that match the baseline length. Based on each of the baseline lengths and the corresponding semivariograms, the satellite instrument background noise variance and the geophysical environment error variance are determined; the satellite instrument background noise variance and the geophysical environment error variance are used to determine the verification result of the target satellite.

[0007] In one optional implementation, the observation equipment includes a Global Navigation Satellite System (GNSS) and an Inertial Navigation System (INS), the observation equipment performs continuous single-point observations, and the buoy observation data includes dual-frequency observations and attitude angles over multiple buoy observation periods; The determination of multiple sea surface heights corresponding to the buoy based on buoy observation data from observation equipment installed on the buoy includes: For each buoy observation time, based on the dual-frequency observation values ​​at that buoy observation time, the three-dimensional spatial coordinates of the buoy are determined, and the three-dimensional spatial coordinates are converted into the antenna phase center position of the GNSS; the antenna phase center position includes longitude, latitude, and sea surface height; Based on the attitude angle of the buoy during the observation time and the distance between the antenna phase center of the GNSS and the sea surface, the position of the antenna phase center is reduced to the buoy's centroid, and the antenna phase center position after being reduced to the buoy's centroid is reduced to the instantaneous sea surface to obtain the instantaneous sea surface position. The instantaneous sea surface height, including the instantaneous sea surface position, is filtered to obtain the filtered instantaneous sea surface height. The filtered instantaneous sea level is corrected according to the mean tide system matched with the target satellite to obtain the observed sea level of the buoy at the buoy observation time.

[0008] In one optional implementation, determining the satellite-observed sea surface height corresponding to the buoy based on the target satellite's along-orbit sea surface height observation data includes: Extract the original sea surface height corresponding to each grid point within the target range centered on the buoy from the sea surface height observation data along the target satellite's orbit; The original sea level height is corrected for environmental errors to obtain the corrected sea level height. The buoy position is interpolated based on the corrected sea level height to obtain the satellite-observed sea level height corresponding to the buoy.

[0009] In one optional implementation, the step of correcting the original sea level height for environmental errors to obtain the corrected sea level height includes: Environmental correction terms are extracted from the sea surface height observation data along the track. These environmental correction terms include ocean tide model correction terms, dynamic atmospheric correction terms, wet tropospheric delay correction terms, and sea state deviation correction terms. The original sea surface height is corrected for environmental errors based on the environmental correction terms to obtain the corrected sea surface height.

[0010] In one optional implementation, the step of filtering the effectiveness of multiple buoys based on the satellite observation time and buoy observation time corresponding to each buoy to determine multiple target buoys includes: For each of the buoys, a mass marker is extracted from the sea level observation data along the track; When the quality indicator indicates that the quality of the orbital sea level height observation data is valid, the satellite observation time corresponding to the satellite-observed sea level height is extracted from the quality of the orbital sea level height observation data, and the buoy observation time corresponding to each observed sea level height is extracted from the buoy observation data. The coverage rate of the buoy observation time within the time window corresponding to the satellite observation time is determined. If the coverage rate is greater than the coverage rate threshold, the buoy is determined to be the target buoy.

[0011] In one optional implementation, the method further includes: Based on the satellite-observed sea surface height and the buoy-observed sea surface height corresponding to each of the target buoys, determine the sea surface height residual corresponding to each of the target buoys; For the sea level residual sequence composed of each of the sea level residuals, the deviation range is determined based on the interquartile range of the sea level residual sequence; If the sea surface height residual corresponding to any of the target buoys exceeds the deviation range, the target buoys shall be eliminated. The step of forming a target buoy pair from any two target buoys includes: For the multiple target buoys remaining after the elimination process, any two target buoys are paired together to form a target buoy pair.

[0012] In one optional embodiment, the buoys in the buoy array are arranged according to an along-track reference line and a cross-track reference line, wherein the along-track reference line is the surface projection of the center line of the target satellite's sweep swath, and the cross-track reference line is perpendicular to the along-track reference line; the method further includes: Based on the satellite-observed sea surface height and the buoy-observed sea surface height corresponding to each target buoy arranged according to the trans-orbit baseline, determine the sea surface height residual corresponding to each target buoy arranged according to the trans-orbit baseline; Based on the sea surface height residuals and cross-track distances corresponding to each target buoy arranged according to the cross-track baseline, the roll error and phase error corresponding to the target satellite are determined; the roll error and phase error are used to determine the verification result of the target satellite.

[0013] According to a second aspect of this application, an on-orbit geometric verification device for satellite altimetry data is provided, the device comprising: The data acquisition module is used to determine multiple sea surface heights corresponding to each buoy in the buoy array based on buoy observation data from the observation equipment installed on the buoy, and to determine the satellite observation sea surface height corresponding to the buoy based on the sea surface height observation data along the orbit of the target satellite. The buoy screening module is used to screen multiple buoys for effectiveness based on the satellite observation time and buoy observation time corresponding to each buoy, determine multiple target buoys, and form a target buoy pair by any two target buoys. The dual-difference observation module is used to determine the dual-difference residual for each target buoy pair based on the satellite-observed sea surface height and the buoy-observed sea surface height corresponding to each target buoy in the target buoy pair; the buoy-observed sea surface height is determined based on multiple observed sea surface heights corresponding to the target buoy. The semi-variation determination module is used to determine the semi-variation value corresponding to the baseline length between the two target buoys in each target buoy pair, based on the number of target buoy pairs that match the baseline length and the double-difference residuals corresponding to the target buoy pairs that match the baseline length. The variance separation module is used to determine the satellite instrument background noise variance and the geophysical environment error variance based on each of the baseline lengths and the corresponding semivariograms; the satellite instrument background noise variance and the geophysical environment error variance are used to determine the verification result of the target satellite.

[0014] According to a third aspect of this application, a computer device is provided, comprising: a processor, a memory, and a bus, wherein the memory stores machine-readable instructions executable by the processor, and when the computer device is running, the processor communicates with the memory via the bus, and when the machine-readable instructions are executed by the processor, the steps of the on-orbit geometric verification method for satellite altimetry data described in the first aspect are performed.

[0015] According to a fourth aspect of this application, a computer-readable storage medium is provided, on which a computer program is stored, which, when executed by a processor, performs the steps of the on-orbit geometric verification method for satellite altimetry data described in the first aspect.

[0016] The on-orbit geometric verification method, apparatus, equipment, and medium for satellite altimetry data provided in this application determine the sea surface height observed by each buoy in the buoy array and the sea surface height observed by the satellite. Based on the observation time, validity screening is completed and target buoy pairs are constructed. For each target buoy pair, double difference processing and semi-variogram analysis are performed to separate the variance of the satellite instrument's background noise and the variance of the geophysical environment error, achieving variance coupling. This accurately determines the background noise of the satellite instrument and effectively reduces the impact of environmental errors on the analysis of the satellite instrument's background noise. Compared with satellite errors coupled with geophysical environment errors, it can restore the true performance of the satellite instrument and improve the accuracy of the verification results.

[0017] It should be understood that the above general description and the following detailed description are merely exemplary and explanatory, and are not intended to limit the technical solutions of this disclosure.

[0018] To make the above-mentioned objects, features and advantages of this disclosure more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the embodiments will be briefly described below. These drawings are incorporated in and constitute a part of this specification. They illustrate embodiments conforming to this disclosure and, together with the specification, serve to explain the technical solutions of this disclosure. It should be understood that the following drawings only show some embodiments of this disclosure and should not be considered as limiting the scope. Those skilled in the art can obtain other related drawings based on these drawings without creative effort.

[0020] Figure 1 A flowchart of an on-orbit geometric verification method for satellite altimetry data provided in an embodiment of this disclosure is shown; Figure 2This diagram illustrates the process of on-orbit geometric verification of satellite altimetry data provided in an embodiment of this disclosure. Figure 3 A schematic diagram of a buoy array provided in an embodiment of this disclosure is shown; Figure 4 A schematic diagram illustrating the variance of satellite instrument background noise and the variance of geophysical environment error provided in an embodiment of this disclosure is shown. Figure 5 A schematic diagram of an error in the cross-track direction provided by an embodiment of this disclosure is shown; Figure 6 This illustration shows one of the schematic diagrams of an on-orbit geometric verification device for satellite altimetry data provided in an embodiment of this disclosure; Figure 7 This is a second schematic diagram of an on-orbit geometric verification device for satellite altimetry data provided in an embodiment of this disclosure; Figure 8 A schematic diagram of the structure of a computer device provided in an embodiment of this disclosure is shown. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. The components of the embodiments of this disclosure described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this disclosure provided in the accompanying drawings is not intended to limit the scope of the claimed disclosure, but merely represents selected embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without inventive effort are within the scope of protection of this disclosure.

[0022] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0023] In this document, the term "and / or" merely describes a relationship, indicating that three relationships can exist. For example, A and / or B can represent three cases: A alone, A and B simultaneously, and B alone. Furthermore, the term "at least one" in this document means any combination of at least two of any one or more elements. For example, including at least one of A, B, and C can mean including any one or more elements selected from the set consisting of A, B, and C.

[0024] Furthermore, the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this disclosure are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments described herein can be implemented in a sequence other than that illustrated or described herein.

[0025] Research has revealed that on-orbit geometric verification of satellite altimetry data often relies on long-term maintained ground verification fields, mostly employing a nadir point model. This involves comparing the instantaneous altitude of the satellite at its overhead position using tide gauge stations or individual GNSS buoys. However, this method, due to its use of single or sparse stations, suffers from insufficient spatial coverage and a limited verification dimension. It can only achieve point-to-point absolute deviation assessment, lacking the ability to verify the variation of errors with spatial scales and failing to verify the error distribution characteristics within a two-dimensional swath up to 120 km wide. Consequently, it cannot distinguish between satellite instrument background noise and geophysical environmental errors, especially in the short-scale range of 10 to 100 km. The coupling between satellite instrument background noise and geophysical environmental errors such as nearshore moist tropospheric delay and tidal residuals is severe, leading to significant uncertainty in the verification results. This can cause otherwise valid satellite altimetry data to be incorrectly classified as invalid. Some methods directly incorporate the root mean square error of geophysical environmental errors into the satellite error, resulting in an underestimation of the actual performance of the satellite instrument.

[0026] Based on the above research, this disclosure provides an on-orbit geometric verification method for satellite altimetry data. Using a buoy array, through double-difference processing and semi-variogram analysis, the variance of the satellite instrument's background noise and the variance of the geophysical environment error are separated, achieving variance coupling. This accurately determines the background noise of the satellite instrument, effectively reduces the impact of environmental errors on the analysis of the satellite instrument's background noise, and improves the accuracy of the verification results.

[0027] To facilitate understanding of this embodiment, a detailed description of the on-orbit geometric verification method for satellite altimetry data disclosed in this application embodiment is provided first. The execution entity of the on-orbit geometric verification method for satellite altimetry data provided in this application embodiment is generally a computer device with certain computing capabilities. This computer device can be a server, which can be an independent physical server, a server cluster or distributed system composed of multiple physical servers, or a cloud server providing basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud storage, big data, and artificial intelligence platforms. In some possible implementations, the computer device can also be a terminal device, which can be a mobile device, terminal, handheld device, computing device, vehicle-mounted device, etc. In other implementations, the on-orbit geometric verification method for satellite altimetry data can be applied to an implementation environment composed of a terminal device and a server. Furthermore, the on-orbit geometric verification method for satellite altimetry data can also be implemented by a processor calling computer-readable instructions stored in memory.

[0028] The following description, in conjunction with the accompanying drawings, illustrates an on-orbit geometric verification method for satellite altimetry data provided in this application.

[0029] See Figure 1 The diagram shown is a flowchart of an on-orbit geometric verification method for satellite altimetry data provided in an embodiment of this disclosure. Figure 1 As shown in the figure, the on-orbit geometric verification method for satellite altimetry data provided in this embodiment includes steps S101 to S105, wherein: S101: For each buoy in the buoy array, based on the buoy observation data from the observation equipment installed on the buoy, determine the multiple sea surface heights corresponding to the buoy, and based on the sea surface height observation data along the orbit of the target satellite, determine the satellite observation sea surface height corresponding to the buoy.

[0030] Here, the buoys in the buoy array are arranged according to the along-track baseline and the cross-track baseline. The along-track baseline is the surface projection of the center line of the target satellite's swath, and the cross-track baseline is perpendicular to the along-track baseline.

[0031] Specifically, the deployment method of the buoy array can be determined based on the swath geometry parameters of the target satellite. For the along-orbit baseline, for example, to meet the requirements of multi-scale baseline sampling during subsequent semi-variation analysis, the number of buoys must ensure that there are at least two pairs of effective buoys in each distance range; the number of buoys deployed along the along-orbit baseline can be greater than or equal to five, forming a longitudinal sub-array; the spacing between adjacent buoys adopts a non-uniform distribution, covering the spatial scale from the minimum baseline distance (e.g., 10km) to the maximum baseline distance (e.g., 80km). For the trans-orbit baseline, the number of buoys deployed along the trans-orbit baseline can be greater than or equal to seven, forming a lateral sub-array; to meet the requirements of subsequent independent identification of the linear term of the trans-orbit roll error and the quadratic term of the phase error, it covers the span from the minimum lateral distance from the nadir point (e.g., 10km) to the maximum lateral distance (e.g., 60km).

[0032] It is understood that the above parameter values ​​are all examples, and the specific values ​​can be set according to the satellite orbit parameters of the target satellite and the on-orbit geometric verification requirements of the satellite altimetry data. No limitation is made here.

[0033] Traditional calibration methods using single or sparse stations cannot meet the calibration requirements of wide-swath interferometric imaging altimeters for two-dimensional spatial error fields. Compared to traditional methods, the embodiments disclosed in this disclosure employ a buoy array, which can improve the accuracy and precision of calibration, especially enabling on-orbit accuracy verification and error calibration for wide-swath marine topographic mapping satellites equipped with interferometric synthetic aperture radar.

[0034] In some possible implementations, the observation equipment includes a Global Navigation Satellite System (GNSS) and an Inertial Navigation System (INS), the observation equipment performs continuous single-point observations, and the buoy observation data includes dual-frequency observations and attitude angles over multiple buoy observation periods.

[0035] Here, each buoy is equipped with a GNSS and an Inertial Navigation System (INS). The GNSS includes a dual-frequency receiver capable of acquiring dual-frequency observations at a preset sampling frequency (e.g., 2Hz). These dual-frequency observations include L1 and L2 pseudorange observations and carrier phase observations. The center frequency of L1 is 1575.42MHz, and the wavelength is 19.03cm; the center frequency of L2 is 1227.60MHz, and the wavelength is 24.42cm. The GNSS antenna is mounted on top of the buoy. The INS is capable of acquiring attitude angles at a preset sampling frequency (e.g., greater than or equal to 100Hz), including pitch, roll, and yaw angles. The INS is installed inside the buoy's body. In practice, the observation equipment performs continuous single-point observations; therefore, the buoy observation data for each buoy includes dual-frequency observations and attitude angles over a series of buoy observation periods.

[0036] Specifically, determining multiple sea surface heights corresponding to the buoy based on buoy observation data from the observation equipment installed on the buoy includes: For each buoy observation time, based on the dual-frequency observation values ​​at that buoy observation time, the three-dimensional spatial coordinates of the buoy are determined, and the three-dimensional spatial coordinates are converted into the antenna phase center position of the GNSS; the antenna phase center position includes longitude, latitude, and sea surface height; Based on the attitude angle of the buoy during the observation time and the distance between the antenna phase center of the GNSS and the sea surface, the position of the antenna phase center is reduced to the buoy's centroid, and the antenna phase center position after being reduced to the buoy's centroid is reduced to the instantaneous sea surface to obtain the instantaneous sea surface position. The instantaneous sea surface height, including the instantaneous sea surface position, is filtered to obtain the filtered instantaneous sea surface height. The filtered instantaneous sea level is corrected according to the mean tide system matched with the target satellite to obtain the observed sea level of the buoy at the buoy observation time.

[0037] In the above steps, the three-dimensional spatial coordinates of the buoy at the buoy observation time can be determined based on the non-differential combined precise single-point positioning observation model and the dual-frequency observation values ​​at the buoy observation time. The three-dimensional spatial coordinates of the buoy include the X, Y, and Z components of the buoy in the geocentric geofixed coordinate system.

[0038] Specifically, the non-differential combined precise single-point positioning observation model can be represented by the following formula (1): (1) in, Indicates GNSS receiver To the target satellite The pseudorange observations were acquired by a GNSS receiver mounted on the buoy; Indicates GNSS receiver To the target satellite The carrier phase observations were obtained by a GNSS receiver mounted on the buoy; Represents the speed of light; The receiver clock bias can be obtained using least squares estimation. The satellite clock bias is represented by a precision clock bias product published by the International GNSS Service (IGS), with an accuracy better than 0.1 ns. Indicates tropospheric delay; λ represents the ionospheric delay, calculated using dual-frequency observations from a GNSS receiver; λ represents the carrier wavelength. The integer ambiguity can be obtained by least squares estimation. and These represent pseudorange observation noise and carrier phase observation noise, respectively. They are random errors and are minimized as residuals in least squares estimation. This indicates the geometric distance between the GNSS antenna phase center and the target satellite.

[0039] Substituting the dual-frequency observation values ​​under the buoy observation time into the non-differential combined precise single-point positioning observation model, the geometric distance between the GNSS antenna phase center and the target satellite can be obtained. The three-dimensional spatial coordinates of the target satellite at the buoy observation time can be obtained based on the precision clock bias product published by IGS. Based on the geometric distance between the GNSS antenna phase center and the target satellite, and the three-dimensional spatial coordinates of the target satellite at the buoy observation time, the three-dimensional spatial coordinates of the buoy at the buoy observation time can be determined.

[0040] Convert the three-dimensional spatial coordinates into longitude. ,latitude The ellipsoidal height. Subtracting the geoid from the ellipsoidal height yields the corresponding sea level height, thus determining the longitude. ,latitude and sea level The location of the antenna phase center of the GNSS was determined.

[0041] After determining the antenna phase center position, attitude and boom effect corrections are applied to it. Specifically, based on the attitude angle at the buoy observation time, the rotation matrix from the buoy carrier coordinate system to the navigation coordinate system is determined. Based on the rotation matrix and the distance between the GNSS antenna phase center and the sea surface, the antenna phase center position is reduced to the buoy's centroid, and then reduced to the instantaneous sea surface position. The distance between the GNSS antenna phase center and the sea surface can be determined after buoy installation by measuring the length of the fixed boom from the GNSS antenna phase center to the sea surface.

[0042] Specifically, the instantaneous sea surface position can be determined by the following formula (2): (2) in, Indicates the instantaneous position of the sea surface (including longitude, latitude, and sea surface height); Indicates the location of the GNSS antenna phase center (including longitude, latitude, and sea level); This represents the rotation matrix from the buoy carrier coordinate system to the navigation coordinate system. Indicates pitch angle, Indicates the roll angle. Indicates the heading angle; This indicates the distance between the GNSS antenna phase center and the sea surface.

[0043] The rotation matrix from the buoy carrier coordinate system to the navigation coordinate system can be expressed by the following formula (3): (3) in, This represents the rotation matrix from the buoy carrier coordinate system to the navigation coordinate system. Indicates pitch angle, Indicates the roll angle. Indicates the heading angle.

[0044] By sorting the sea surface heights included in the instantaneous sea surface positions at each buoy observation time according to time, we can obtain the original sea surface height sequence h(t) at the preset sampling frequency, where t represents the buoy observation time.

[0045] Traditional calibration methods mostly employ buoy processing techniques from Differential Global Positioning System (GPS) or Real Time Kinematic (RTK) for filtering. This filtering method is limited by the baseline length, resulting in limited reference accuracy and easily smoothing out shortwave ocean signals observable by satellites.

[0046] In this embodiment of the disclosure, an adaptive Gaussian low-pass filter is constructed, and a Gaussian convolution kernel is used to filter the original sea surface height sequence. This can remove high-frequency wave noise that does not match the size of the target satellite spot, and obtain the filtered instantaneous sea surface height.

[0047] Specifically, the filtered instantaneous sea level height can be expressed by the following formula (4): (4) in, Indicates the buoy observation time The instantaneous sea level height after filtering; Represents the integral variable; This represents the standard deviation of the Gaussian kernel, in seconds. For example, setting... =30s, corresponding to a 3dB cutoff frequency fc≈1 / (2π) It can effectively preserve medium and long wave ocean signals with spatial wavelengths greater than 2km.

[0048] In practical applications, satellite-measured sea surface height data is based on the mean tide system, while buoy-GNSS-calculated sea surface height data is based on the zero-tide system. The filtered instantaneous sea surface height is corrected according to the mean tide system matched with the target satellite, thus correcting the filtered instantaneous sea surface height to the mean tide system. This yields the observed sea surface height of the buoy at the specified observation time, converting the zero-tide sea surface height data measured by the buoy into a data consistent with the satellite altimetry reference. By unifying the geodetic reference and ellipsoidal parameters of the satellite and the buoy, consistent processing of permanent tides is ensured.

[0049] Specifically, the observed sea surface height can be determined using the following formula (5): (5) in, This indicates the observed sea level height of the buoy under the mean tide system; This indicates the filtered instantaneous sea level of the buoy under zero tide conditions. This represents the amount of permanent tidal crustal deformation, expressed in meters.

[0050] The amount of permanent tidal crustal deformation can be determined by the following formula (6): (6) in, This represents the amount of permanent tidal crustal deformation. This indicates the latitude included in the instantaneous sea surface position.

[0051] Thus, traditional calibration methods struggle to simultaneously preserve mid- and long-wave ocean signals and eliminate wave noise, failing to provide millimeter-level dynamic sea surface height references and limiting reference accuracy. This disclosed embodiment employs precise single-point positioning combined with attitude and lever effect correction, adaptive Gaussian filtering, and tidal unification to construct a high-precision dynamic base sea surface height reference that matches the wide-swath pixel scale of satellites. This results in a buoy array differential reference accuracy better than 5mm, significantly improving reference accuracy compared to traditional methods and meeting millimeter-level calibration requirements.

[0052] In some possible implementations, determining the satellite-observed sea surface height corresponding to the buoy based on the target satellite's along-orbit sea surface height observation data includes: Extract the original sea surface height corresponding to each grid point within the target range centered on the buoy from the sea surface height observation data along the target satellite's orbit; The original sea level height is corrected for environmental errors to obtain the corrected sea level height. The buoy position is interpolated based on the corrected sea level height to obtain the satellite-observed sea level height corresponding to the buoy.

[0053] In the above steps, the orbital sea surface height observation data of the target satellite can be obtained based on the buoy's observation time, longitude, and latitude (i.e., the longitude and latitude included in the instantaneous sea surface position). The target satellite performs instantaneous area observation. The orbital sea surface height observation data of the target satellite includes the satellite observation time, longitude, latitude, original sea surface height, quality label, correction items, etc., for each grid point. Then, based on the longitude and latitude of the buoy (i.e., the longitude and latitude included in the instantaneous sea surface position), the original sea surface height corresponding to each grid point within the target range centered on the buoy can be extracted from the target satellite's orbital sea surface height observation data, thus loading the satellite data. The specific value of the target range can be determined according to the actual needs of determining the satellite's observed sea surface height, and is not limited here.

[0054] After obtaining the original sea level height, environmental error correction can be applied to the original sea level height to obtain the corrected sea level height.

[0055] In some possible implementations, the step of correcting the original sea level for environmental errors to obtain the corrected sea level includes: Environmental correction terms are extracted from the sea surface height observation data along the track. These environmental correction terms include ocean tide model correction terms, dynamic atmospheric correction terms, wet tropospheric delay correction terms, and sea state deviation correction terms. The original sea surface height is corrected for environmental errors based on the environmental correction terms to obtain the corrected sea surface height.

[0056] Here, the environmental correction item can be removed from the original sea level height, and the result after deletion can be used as the corrected sea level height.

[0057] Specifically, the corrected sea level height can be determined using the following formula (7): (7) in, This indicates the corrected sea level. Indicates the original sea level height. This represents the correction term for the ocean tide model. This indicates a dynamic atmospheric correction term. This represents the wet tropospheric delay correction term. This indicates the sea state deviation correction item.

[0058] In this way, by extracting ocean tide model correction terms, dynamic atmospheric correction terms, wet tropospheric delay correction terms, and sea state deviation correction terms from the sea surface height observation data along the orbit, and performing multi-source geophysical error correction on the original sea surface height based on the above correction terms, it is possible to effectively eliminate systematic errors introduced by various natural environmental factors, making the satellite-observed sea surface height obtained by subsequent interpolation more accurate and reliable.

[0059] In other possible implementations, the environmental corrections can also be calculated using corresponding geophysical models. For example, ocean tidal model corrections can be calculated using ocean tidal models (such as FES2014), dynamic atmospheric corrections can be obtained using atmospheric models or radiometer data carried by the target satellite, moist tropospheric delay corrections can be obtained using microwave radiometers carried by the target satellite or atmospheric reanalysis models, and sea state deviation corrections can be estimated using empirical models based on significant wave height and wind speed.

[0060] After obtaining the corrected sea surface height, the longitude and latitude corresponding to each grid point covering the target area centered on the buoy can be extracted from the along-track sea surface height observation data. Using bilinear interpolation, the buoy position is determined based on the longitude and latitude corresponding to the buoy (i.e., the longitude and latitude included in the instantaneous sea surface position). The longitude and latitude corresponding to each grid point covering the target area centered on the buoy, as well as the corrected sea surface height, are interpolated to the buoy position to obtain the satellite-observed sea surface height corresponding to the buoy.

[0061] Specifically, the satellite-observed sea surface height corresponding to the buoy can be determined by the following formula (8): (8) in, Indicates the first The satellite observation sea level corresponding to each buoy Indicates bilinear interpolation. This indicates the longitude corresponding to the grid point. Indicates the latitude corresponding to the grid point. Indicates the first The longitude corresponding to each buoy Indicates the first The latitude corresponding to each buoy This indicates the corrected sea level.

[0062] In this way, by extracting the original sea surface height data of the grid points covering the target area where the buoy is located and performing environmental error correction, the interference of systematic bias introduced by environmental factors on satellite observation results can be effectively reduced. Then, based on the corrected sea surface height, the buoy position can be interpolated to accurately obtain the satellite-observed sea surface height corresponding to the spatial position of the buoy. This ensures the consistency and accuracy of the spatial matching between satellite observations and buoy observations, providing a reliable data foundation for subsequent processing.

[0063] S102: Based on the satellite observation time and buoy observation time corresponding to each buoy, the effectiveness of multiple buoys is screened to determine multiple target buoys, and any two target buoys are combined into a target buoy pair.

[0064] Here, the satellite observation time and buoy observation time corresponding to each buoy can be extracted. Each observed sea surface height corresponds to one buoy observation time, and each satellite observed sea surface height corresponds to one satellite observation time. Therefore, each buoy corresponds to one satellite observation time and multiple buoy observation times.

[0065] In some possible implementations, the step of filtering the effectiveness of multiple buoys based on the satellite observation time and buoy observation time corresponding to each buoy to determine multiple target buoys includes: For each of the buoys, a mass marker is extracted from the sea level observation data along the track; When the quality indicator indicates that the quality of the orbital sea level height observation data is valid, the satellite observation time corresponding to the satellite-observed sea level height is extracted from the quality of the orbital sea level height observation data, and the buoy observation time corresponding to each observed sea level height is extracted from the buoy observation data. The coverage rate of the buoy observation time within the time window corresponding to the satellite observation time is determined. If the coverage rate is greater than the coverage rate threshold, the buoy is determined to be the target buoy.

[0066] In the above steps, for each buoy, a quality indicator is extracted from the along-track sea level height observation data. If the quality indicator indicates that the along-track sea level height observation data is invalid or missing, the buoy observation is invalid, and therefore the buoy is not considered a target buoy. If the quality indicator indicates that the along-track sea level height observation data is valid, the satellite observation time corresponding to the satellite-observed sea level height is extracted from the along-track sea level height observation data quality, and the buoy observation time corresponding to each observed sea level height is extracted from the buoy observation data.

[0067] When determining the coverage of the buoy observation time within the time window corresponding to the satellite observation time, specifically, based on the preset time window length, the number of buoy observation times within the time window corresponding to the satellite observation time, and the total number of buoy observation times corresponding to the time window are determined; the ratio of the number of buoy observation times within the time window corresponding to the satellite observation time to the total number of buoy observation times corresponding to the time window is determined as the coverage.

[0068] The specific length of the time window is set according to the needs of validity filtering, and is not limited here. For example, the time window length... For example, For satellite observation time The corresponding time window; determine the location Buoy observation time quantity Total number of buoy observation times corresponding to the time window ,Will and The ratio of is determined as the coverage rate.

[0069] Specifically, the coverage rate can be determined by the following formula (9): (9) in, Indicates coverage rate. This indicates the number of buoy observation times within the time window corresponding to the satellite observation time. This represents the total buoy observation time corresponding to the time window.

[0070] The total number of buoy observation times corresponding to the time window can be determined based on the time window length and the sampling frequency of the GNSS receiver. The total number of buoy observation times corresponding to the time window can be determined by the following formula (10): (10) in, This indicates the total number of buoy observation times corresponding to the time window. Indicates the length of the time window. This indicates the sampling frequency of the GNSS receiver.

[0071] The coverage rate is compared with a coverage threshold. If the coverage rate is greater than the coverage threshold, the buoy is determined to be the target buoy. The specific coverage threshold is set according to the needs of the effectiveness screening and is not limited here; for example, the coverage threshold could be 50%.

[0072] Optionally, since the satellite observation time and buoy observation time are acquired using different systems, after extracting the satellite observation time and buoy observation time, all satellite observation time and buoy observation time can be synchronized to the same time system, such as Coordinated Universal Time (UTC), to ensure that the timestamps of the acquired data are consistent and to achieve a unified benchmark for the measurement time of both satellites and buoys. The coverage rate is then determined using the adjusted satellite observation time and buoy observation time.

[0073] In this way, by initially screening buoys based on satellite data quality indicators and then conducting a secondary screening based on the coverage of the time window corresponding to the satellite observation time and the buoy observation time, invalid buoys with satellite observation failures or insufficient time matching can be effectively eliminated, ensuring that the target buoys participating in subsequent verification have reliable observation quality and good time-frequency matching.

[0074] Optionally, after selecting multiple target buoys, for each target buoy, the buoy observation sea level corresponding to that target buoy is determined based on multiple observed sea level heights corresponding to that target buoy. In specific implementation, the sea level height can be determined based on the buoy observation time within the time window corresponding to the satellite observation time. The buoy observation sea surface height corresponding to the target buoy was obtained by using cubic spline interpolation. .

[0075] In some possible implementations, the method further includes: Based on the satellite-observed sea surface height and the buoy-observed sea surface height corresponding to each of the target buoys, determine the sea surface height residual corresponding to each of the target buoys; For the sea level residual sequence composed of each of the sea level residuals, the deviation range is determined based on the interquartile range of the sea level residual sequence; If the sea surface height residual corresponding to any of the target buoys exceeds the deviation range, the target buoys shall be eliminated. The step of forming a target buoy pair from any two target buoys includes: For the multiple target buoys remaining after the elimination process, any two target buoys are paired together to form a target buoy pair.

[0076] In the above steps, for each target buoy, based on the satellite-observed sea surface height and the buoy-observed sea surface height corresponding to the target buoy, the sea surface height residual corresponding to the target buoy is determined. These sea surface height residuals are then used to construct a sea surface height residual sequence.

[0077] Specifically, the sea surface height residual sequence can be represented by the following formula (11): (11) in, Indicates the first Sea surface height residual for each buoy Indicates the first The satellite observation sea level corresponding to each buoy Indicates the first Each buoy corresponds to the buoy's observation of sea surface height.

[0078] Calculate the first quartile and the third quartile for the sea surface height residual sequence, and determine the interquartile range of the sea surface height residual sequence based on the first quartile and the third quartile.

[0079] Specifically, the interquartile range can be determined by the following formula (12): (12) in, Indicates the interquartile range. Indicates the third quartile. This represents the first quartile.

[0080] The deviation range is determined based on the first quartile, the third quartile, and the interquartile range.

[0081] Specifically, the deviation range can be expressed by the following formula (13): (13) in, Indicates the interquartile range. Indicates the third quartile. This represents the first quartile.

[0082] Each sea level height residual is compared with the deviation range. If any sea level height residual exceeds the deviation range, it indicates that the sea level height residual is abnormal. The target buoys with sea level height residuals exceeding the deviation range are then eliminated. Furthermore, for the remaining target buoys after the elimination process, any two target buoys are paired together.

[0083] In this way, by calculating the sea surface height residual corresponding to each target buoy and constructing the deviation range based on the interquartile range of the sea surface height residual sequence, target buoys with gross errors and abnormal deviations can be automatically identified and eliminated, effectively avoiding abnormal data from interfering with subsequent processing and ensuring the accuracy and reliability of the calibration results.

[0084] S103: For each target buoy pair, based on the satellite-observed sea surface height and the buoy-observed sea surface height corresponding to each target buoy in the target buoy pair, determine the double-difference residual corresponding to the target buoy pair; the buoy-observed sea surface height is determined based on multiple observed sea surface heights corresponding to the target buoy.

[0085] In this step, for each target buoy pair, based on the satellite-observed sea surface height and the buoy-observed sea surface height corresponding to each target buoy in the pair, the sea surface height residual corresponding to each target buoy is determined. The difference between the two sea surface height residuals is then determined as the double-difference residual corresponding to the target buoy pair. In this way, by determining the double-difference residual, common-mode error can be eliminated, that is, systematic geoid error and large-scale orbital error can be eliminated.

[0086] Specifically, the double-difference residuals corresponding to the target buoy pair can be determined by the following formula (14): (14) in, Indicates the first The buoy and the first The target buoy pair consisting of several buoys corresponds to the double-difference residuals. Indicates the first The satellite observation sea level corresponding to each buoy Indicates the first Each buoy corresponds to the buoy's observation of sea surface height. Indicates the first The satellite observation sea level corresponding to each buoy Indicates the first Each buoy corresponds to the buoy's observation of sea surface height.

[0087] S104: For the baseline length between the two target buoys in each target buoy pair, determine the semi-variance value corresponding to the baseline length based on the number of target buoy pairs matching the baseline length and the double-difference residuals corresponding to the target buoy pairs matching the baseline length.

[0088] In this step, the baseline length between the two target buoys in each target buoy pair is determined. For each baseline length, the corresponding distance interval is determined based on the distance grading width. The specific distance grading width is set according to the on-orbit geometric verification requirements of the satellite altimetry data and is not limited here.

[0089] Specifically, the distance interval can be represented by the following formula (15): (15) in, Indicates the baseline length. Indicates the width of the distance increments.

[0090] Target buoy pairs whose baseline length falls within the specified distance interval are identified as target buoy pairs whose baseline length matches the specified distance interval. This determines the number of target buoy pairs matching the specified baseline length and the corresponding double-difference residuals. A semi-variogram is constructed, and based on the semi-variogram, the semi-variogram value corresponding to the specified baseline length is determined using the specified quantities and double-difference residuals.

[0091] Specifically, the semi-variogram function can be represented by the following formula (16): (16) in, Indicates baseline length The corresponding semi-mutated value, Indicates the length of the baseline The number of target buoy pairs matched. Indicates the first Individual and baseline length The matching target buoy pair corresponds to the double-difference residual.

[0092] It is understandable that after validity screening and target buoy removal, some observations are missing. Therefore, there may be cases where the number of target buoy pairs matching a certain baseline length is 0. In this case, there are no available target buoy pairs within the distance interval corresponding to the baseline length. Therefore, there is no need to determine the semivariogram corresponding to the baseline length, nor does it participate in subsequent variance separation.

[0093] S105: Based on each of the baseline lengths and the corresponding semi-variable values, determine the satellite instrument background noise variance and the geophysical environment error variance; the satellite instrument background noise variance and the geophysical environment error variance are used to determine the verification result of the target satellite.

[0094] In this step, an exponential variogram model can be constructed to separate the satellite instrument background noise from the geophysical environment error based on the exponential variogram model. Specifically, the exponential variogram model can be represented by the following formula (17): (17) in, Indicates baseline length The corresponding semi-mutated value; Indicates the baseline length; This represents the variance of the satellite instrument's background noise, corresponding to the intercept of the semivariogram (i.e., (limit value at time). This represents the variance of geophysical environmental errors; It represents the spatial correlation length of geophysical environmental errors.

[0095] The parameters in the exponential variogram model are adjusted using the lengths of each baseline and their corresponding semivariogram values. , and To minimize the fitting error, record the time when the fitting error is minimized. , and The specific values ​​are used as the final determined variances of the satellite instrument background noise and the geophysical environment error, thereby achieving quantitative separation of satellite instrument noise and geophysical environment error. Optionally, the calibration result of the target satellite can be determined based on the aforementioned variances of the satellite instrument background noise and the geophysical environment error.

[0096] In some possible implementations, the buoys in the buoy array are arranged according to an along-track baseline and a trans-track baseline, wherein the along-track baseline is the surface projection of the center line of the target satellite's swath, and the trans-track baseline is perpendicular to the along-track baseline; the method further includes: Based on the satellite-observed sea surface height and the buoy-observed sea surface height corresponding to each target buoy arranged according to the trans-orbit baseline, determine the sea surface height residual corresponding to each target buoy arranged according to the trans-orbit baseline; Based on the sea surface height residuals and cross-track distances corresponding to each target buoy arranged according to the cross-track baseline, the roll error and phase error corresponding to the target satellite are determined; the roll error and phase error are used to determine the verification result of the target satellite.

[0097] In the above steps, for each target buoy arranged according to the cross-track baseline, the sea surface height residual corresponding to the target buoy is determined based on the satellite-observed sea surface height and the buoy-observed sea surface height. The specific method for determining the sea surface height residual can be referred to formula (11), which will not be elaborated here.

[0098] Based on the lateral distance between the target buoy and the target satellite, the transorbital distance corresponding to the target buoy is determined. An error identification model is constructed, and the roll error and phase error corresponding to the target satellite are determined according to the error identification model.

[0099] Specifically, the error identification model can be represented by the following formula (18): (18) in, This indicates the trans-rail distance corresponding to the target buoy; Indicates the distance across tracks The sea surface height residual corresponding to the target buoy at that location; It represents the roll error and characterizes the linear tilt component; This represents the linear component of the roll error; It represents the phase error and characterizes the second-order distortion component; This represents the second component of the phase error; This represents the random error term.

[0100] Based on the sea surface height residuals and cross-track distances corresponding to each target buoy arranged according to the aforementioned cross-track baseline, the roll error coefficient can be obtained by calculating the error identification model using the least squares method. The estimated value and the phase error coefficient The estimated value. Here, when the estimated value is significantly different from zero, it indicates that there is a systematic geometric error in the transorbiting direction of the target satellite. The estimated value can be fed back to the satellite data management department, so that the roll angle and phase parameter values ​​in the target satellite data processing system can be corrected based on the estimated value.

[0101] Optionally, the verification result of the target satellite can be determined based on the roll error and phase error. Alternatively, the verification result of the target satellite can be determined based on the satellite instrument background noise variance, the geophysical environment error variance, the roll error, and the phase error.

[0102] In traditional verification methods, the baseline roll error unique to the interferometer payload causes a linear tilt in the sea surface height perpendicular to the flight direction, and the phase error causes nonlinear distortion. Single-point observations cannot detect these errors, which mainly exist in the cross-track direction (i.e., the cross-track direction), making it impossible to independently evaluate the cross-track roll error and phase error unique to interferometry, thus resulting in a lack of verification for wide-swath-specific errors. However, in the embodiments disclosed in this disclosure, a hybrid buoy array along and across tracks can be used to perform geometric verification that independently verifies the cross-track roll error and phase error unique to the target satellite interferometric imaging altimeter. This allows for simultaneous verification of sea surface height and cross-track error characteristics, providing a standardized engineering solution for comprehensive quality control of wide-swath satellite data through multi-dimensional comprehensive verification.

[0103] To more clearly illustrate the on-orbit geometric verification process of satellite altimetry data, see [link to documentation]. Figure 2 This is a schematic diagram illustrating an on-orbit geometric verification process for satellite altimetry data, as shown in an exemplary embodiment of this application. Figure 2 As shown, a buoy array is constructed; observation equipment is installed on the buoys; coordinate calculations are performed based on the buoy observation data to obtain the buoy's three-dimensional spatial coordinates; the three-dimensional spatial coordinates are converted into the antenna phase center position; attitude and boom effect corrections are applied to the antenna phase center position to obtain the instantaneous sea surface position; the sea surface height included in the instantaneous sea surface position is filtered to obtain the filtered instantaneous sea surface height; tidal unification is performed according to the mean tide system matched with the target satellite to obtain the observed sea surface height. The along-orbit sea surface height observation data of the target satellite is extracted to obtain the original sea surface height; environmental error correction is applied to the original sea surface height to obtain the corrected sea surface height; the buoy position is interpolated based on the corrected sea surface height to obtain the satellite-observed sea surface height. Multiple buoys are screened for validity to identify multiple target buoys; after removing abnormal target buoys, target buoy pairs are constructed; double-difference processing and semi-variation analysis are performed on each target buoy pair to separate the satellite instrument background noise variance and the geophysical environmental error variance; cross-orbit error detection is performed to obtain roll error and phase error. The specific steps are described in the foregoing embodiments and will not be repeated here.

[0104] To better understand the on-orbit geometric verification process of satellite altimetry data and demonstrate the effectiveness of this embodiment, an example will be provided below. See [link to example]. Figures 3-5 , Figure 3 This is a schematic diagram of a buoy array provided in an embodiment of the present disclosure. Figure 4 This is a schematic diagram illustrating the variance of satellite instrument background noise and the variance of geophysical environment error provided in an embodiment of this disclosure. Figure 5This is a schematic diagram illustrating an error in the transorbital direction provided in an embodiment of this disclosure. This example uses hardware-in-the-loop (HIL) simulation for verification. The data to be verified includes L2-level sea surface height observation data published by the Surface Water and Ocean Topography (SWOT) satellite, orbital number Cycle 573 Pass 043, with a spatial resolution of 2 km, and the observation area located in the Northwest Pacific Ocean (160°E to 168°E, 30°N to 40°N). This data includes actual instrument measurement noise and geophysical environmental errors.

[0105] like Figure 3 As shown, the reference data includes, according to the embodiments of this disclosure, a longitudinal array of buoys (i.e., arranged according to the orbital baseline) is virtually constructed along the satellite's nadir trajectory, with buoys numbered A1 to A7 and spaced 10km to 80km apart. A transverse array (arranged according to the cross-orbit baseline) is constructed in the middle, with buoys numbered C1 to C4, forming a multi-scale hybrid verification topology. The buoy-observed sea surface height is generated according to the embodiments of this disclosure, wherein the significant wave height is set to SWH = 2.0m, and the GNSS observation noise is set to σGNSS = 2cm.

[0106] By using difference-in-differences (DID) processing and semi-variogram analysis, the variance of satellite instrument background noise and the variance of geophysical environmental errors can be separated. For example... Figure 4 As shown in the diagram, the horizontal axis represents the baseline length, the vertical axis represents the variance, the dashed line represents the variance of the satellite instrument background noise, and the curve represents the change of the semivariogram with the baseline length. It can be seen that at a short baseline scale of 10 km, the semivariogram is approximately 8.9 mm. 2 This value is consistent with the calculated variance of the satellite instrument background noise, which is 7.7 mm. 2 The results are relatively close, indicating that under short baseline length conditions, the semivariogram primarily reflects the satellite instrument's background noise level. As the baseline length increases to 80 km, the semivariogram increases to approximately 40.3 mm. 2 The incremental portion (approximately 31.5 mm) 2 This corresponds to the spatial decorrelation effect of geophysical environmental errors such as wet tropospheric delay and tidal model residuals. The above results verify that the method described in the embodiments of this disclosure can effectively separate satellite instrument noise from geophysical environmental errors.

[0107] The sea surface height residual in the trans-track direction is fitted based on the target buoys arranged according to the trans-track baseline. For example... Figure 5 As shown in the figure, the horizontal axis represents the distance across the track. The vertical axis represents the residual sea level height. The black dashed line represents the fitting model curve of the error identification model. ), including roll error and phase error; red dots represent the actual residual points of each buoy; green dashed lines represent the linear component of roll error ( The pink dashed line represents the second component of the phase error (); As can be seen, the roll error exhibits opposite error variation characteristics on both sides of the retracement; the phase error term increases with distance from the nadir point; this is consistent with the expected error characteristics of sea level height measurement caused by satellite attitude roll and phase, demonstrating the effective identification of roll and phase errors by the embodiments of this disclosure. Thus, roll error can be successfully identified. ) and phase error ( The linear component of the roll error and the quadratic component of the phase error at the point where the cross-track distance is 0 verify that the method of this embodiment can effectively detect and separate the systematic geometric distortion in the cross-track direction unique to the wide-span interferometric altimeter.

[0108] The on-orbit geometric verification method for satellite altimetry data provided in this disclosure determines the sea surface height observed by each buoy in the buoy array and the sea surface height observed by the satellite. Based on the observation time, it completes the validity screening and constructs target buoy pairs. For each target buoy pair, it performs double difference processing and semi-variogram analysis to separate the variance of the satellite instrument's background noise and the variance of the geophysical environment error, thereby achieving variance coupling. This accurately determines the background noise of the satellite instrument and effectively reduces the impact of environmental errors on the analysis of the satellite instrument's background noise. Compared with satellite errors coupled with geophysical environment errors, it can restore the true performance of the satellite instrument and improve the accuracy of the verification results.

[0109] Those skilled in the art will understand that, in the above-described method of the specific implementation, the order in which each step is written does not imply a strict execution order and does not constitute any limitation on the implementation process. The specific execution order of each step should be determined by its function and possible internal logic.

[0110] Based on the same inventive concept, this disclosure also provides an on-orbit geometric verification device for satellite altimetry data corresponding to the on-orbit geometric verification method for satellite altimetry data. Since the principle of solving the problem by the on-orbit geometric verification device for satellite altimetry data in this disclosure is similar to the on-orbit geometric verification method for satellite altimetry data described above in this disclosure, the implementation of the device can refer to the implementation of the method, and the repeated parts will not be described again.

[0111] Please see Figure 6 and Figure 7 , Figure 6 This is one of the schematic diagrams of an on-orbit geometric verification device for satellite altimetry data provided in this disclosure. Figure 7 This is a second schematic diagram of an on-orbit geometric verification device for satellite altimetry data provided in an embodiment of this disclosure. Figure 6 As shown in the illustration, the on-orbit geometric verification device 600 for satellite altimetry data provided in this embodiment includes: The data acquisition module 601 is used to determine multiple sea surface heights corresponding to each buoy in the buoy array based on buoy observation data from the observation equipment installed on the buoy, and to determine the satellite observation sea surface height corresponding to the buoy based on the sea surface height observation data along the orbit of the target satellite. The buoy screening module 602 is used to screen multiple buoys based on the satellite observation time and buoy observation time corresponding to each buoy, determine multiple target buoys, and form any two target buoys into a target buoy pair. The dual-difference observation module 603 is used to determine the dual-difference residual corresponding to each target buoy pair based on the satellite-observed sea surface height and the buoy-observed sea surface height corresponding to each target buoy in the target buoy pair; the buoy-observed sea surface height is determined based on multiple observed sea surface heights corresponding to the target buoy. The semi-variation determination module 604 is used to determine the semi-variation value corresponding to the baseline length for each pair of target buoys based on the number of target buoy pairs that match the baseline length and the double-difference residuals corresponding to the target buoy pairs that match the baseline length. The variance separation module 605 is used to determine the satellite instrument background noise variance and the geophysical environment error variance based on each of the baseline lengths and the corresponding semivariograms; the satellite instrument background noise variance and the geophysical environment error variance are used to determine the verification result of the target satellite.

[0112] In one optional implementation, the observation equipment includes a Global Navigation Satellite System (GNSS) and an Inertial Navigation System (INS), the observation equipment performs continuous single-point observations, and the buoy observation data includes dual-frequency observations and attitude angles over multiple buoy observation periods; When the data acquisition module 601 determines multiple sea surface heights corresponding to the buoy based on buoy observation data from the observation equipment installed on the buoy, it is specifically used for: For each buoy observation time, based on the dual-frequency observation values ​​at that buoy observation time, the three-dimensional spatial coordinates of the buoy are determined, and the three-dimensional spatial coordinates are converted into the antenna phase center position of the GNSS; the antenna phase center position includes longitude, latitude, and sea surface height; Based on the attitude angle of the buoy during the observation time and the distance between the antenna phase center of the GNSS and the sea surface, the position of the antenna phase center is reduced to the buoy's centroid, and the antenna phase center position after being reduced to the buoy's centroid is reduced to the instantaneous sea surface to obtain the instantaneous sea surface position. The instantaneous sea surface height, including the instantaneous sea surface position, is filtered to obtain the filtered instantaneous sea surface height. The filtered instantaneous sea level is corrected according to the mean tide system matched with the target satellite to obtain the observed sea level of the buoy at the buoy observation time.

[0113] In one optional implementation, when the data acquisition module 601 determines the satellite-observed sea surface height corresponding to the buoy based on the target satellite's along-orbit sea surface height observation data, it is specifically used for: Extract the original sea surface height corresponding to each grid point within the target range centered on the buoy from the sea surface height observation data along the target satellite's orbit; The original sea level height is corrected for environmental errors to obtain the corrected sea level height. The buoy position is interpolated based on the corrected sea level height to obtain the satellite-observed sea level height corresponding to the buoy.

[0114] In one optional implementation, when the data acquisition module 601 corrects for environmental errors in the original sea surface height to obtain the corrected sea surface height, it is specifically used for: Environmental correction terms are extracted from the sea surface height observation data along the track. These environmental correction terms include ocean tide model correction terms, dynamic atmospheric correction terms, wet tropospheric delay correction terms, and sea state deviation correction terms. The original sea surface height is corrected for environmental errors based on the environmental correction terms to obtain the corrected sea surface height.

[0115] In an optional implementation, when the buoy screening module 602 is used to perform validity screening on multiple buoys based on the satellite observation time and buoy observation time corresponding to each buoy, and to determine multiple target buoys, it is specifically used for: For each of the buoys, a mass marker is extracted from the sea level observation data along the track; When the quality indicator indicates that the quality of the orbital sea level height observation data is valid, the satellite observation time corresponding to the satellite-observed sea level height is extracted from the quality of the orbital sea level height observation data, and the buoy observation time corresponding to each observed sea level height is extracted from the buoy observation data. The coverage rate of the buoy observation time within the time window corresponding to the satellite observation time is determined. If the coverage rate is greater than the coverage rate threshold, the buoy is determined to be the target buoy.

[0116] In an optional implementation, the buoy screening module 602 is further configured to: Based on the satellite-observed sea surface height and the buoy-observed sea surface height corresponding to each of the target buoys, determine the sea surface height residual corresponding to each of the target buoys; For the sea level residual sequence composed of each of the sea level residuals, the deviation range is determined based on the interquartile range of the sea level residual sequence; If the sea surface height residual corresponding to any of the target buoys exceeds the deviation range, the target buoys shall be eliminated. When the buoy selection module 602 is used to form a target buoy pair from any two target buoys, it is specifically used for: For the multiple target buoys remaining after the elimination process, any two target buoys are paired together to form a target buoy pair.

[0117] In one optional embodiment, the buoys in the buoy array are arranged according to an along-track baseline and a cross-track baseline, wherein the along-track baseline is the surface projection of the center line of the target satellite's sweep swath, and the cross-track baseline is perpendicular to the along-track baseline; Figure 7 As shown, the on-orbit geometric verification device 600 for satellite altimetry data further includes a cross-orbit error detection module 606, which is used for: Based on the satellite-observed sea surface height and the buoy-observed sea surface height corresponding to each target buoy arranged according to the trans-orbit baseline, determine the sea surface height residual corresponding to each target buoy arranged according to the trans-orbit baseline; Based on the sea surface height residuals and cross-track distances corresponding to each target buoy arranged according to the cross-track baseline, the roll error and phase error corresponding to the target satellite are determined; the roll error and phase error are used to determine the verification result of the target satellite.

[0118] The processing flow of each module in the device and the interaction flow between each module can be referred to the relevant descriptions in the above method embodiments, and will not be detailed here.

[0119] The on-orbit geometric verification device for satellite altimetry data provided in this embodiment determines the sea surface height observed by each buoy in the buoy array and the sea surface height observed by the satellite. Based on the observation time, it completes the validity screening and constructs target buoy pairs. For each target buoy pair, it performs double difference processing and semi-variogram analysis to separate the variance of the satellite instrument's background noise and the variance of the geophysical environment error, thereby achieving variance coupling. This effectively reduces the impact of environmental errors on the analysis of the satellite instrument's background noise. Compared with satellite errors coupled with geophysical environment errors, it can restore the true performance of the satellite instrument and improve the accuracy of the verification results.

[0120] Corresponding to Figure 1 In addition to the on-orbit geometric verification method for satellite altimetry data, this disclosure also provides a computer device 800, such as... Figure 8 The diagram shown is a structural schematic of a computer device 800 provided in an embodiment of this disclosure, including: The processor 810, memory 820, and bus 830 are included. The memory 820 is used to store execution instructions and includes main memory 821 and external memory 822. The main memory 821, also known as internal memory, is used to temporarily store the operation data in the processor 810 and the data exchanged with external memory 822 such as hard disk. The processor 810 exchanges data with external memory 822 through main memory 821.

[0121] In this embodiment, the memory 820 is specifically used to store application code that executes the scheme of this application, and its execution is controlled by the processor 810. That is, when the computer device 800 is running, the processor 810 communicates with the memory 820 through the bus 830, or the processor 810 communicates with the memory 820 through other means, so that the processor 810 executes the application code stored in the memory 820, and then executes the steps of the on-orbit geometric verification method for satellite altimetry data described in any of the foregoing embodiments.

[0122] The memory 820 may be, but is not limited to, random access memory (RAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), etc.

[0123] Processor 810 may be an integrated circuit chip with signal processing capabilities. The aforementioned processor can be a general-purpose processor, including a Central Processing Unit (CPU), a Network Processor (NP), etc.; it can also be a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components. It can implement or execute the methods, steps, and logic block diagrams disclosed in the embodiments of this invention. The general-purpose processor can be a microprocessor or any conventional processor.

[0124] It is understood that the structures illustrated in the embodiments of this application do not constitute a specific limitation on the computer device 800. In other embodiments of this application, the computer device 800 may include more or fewer components than illustrated, or combine some components, or split some components, or have different component arrangements. The illustrated components may be implemented in hardware, software, or a combination of software and hardware.

[0125] This disclosure also provides a computer-readable storage medium storing a computer program. When executed by a processor, the computer program performs the steps of the on-orbit geometric verification method for satellite altimetry data described in the above-described method embodiments. The storage medium can be either volatile or non-volatile computer-readable storage.

[0126] This disclosure also provides a computer program product, which stores a computer program. When the computer program is run by a processor, it executes the steps of the on-orbit geometric verification method for satellite altimetry data provided in any of the above embodiments of this disclosure. For details, please refer to the above method embodiments, which will not be repeated here.

[0127] The aforementioned computer program product can be implemented through hardware, software, or a combination thereof. In one optional embodiment, the computer program product is specifically embodied in a computer storage medium, which can be a volatile or non-volatile computer-readable storage medium. In another optional embodiment, the computer program product is specifically embodied in a software product, such as a software development kit (SDK), etc.

[0128] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the devices and apparatuses described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here. In the several embodiments provided in this disclosure, it should be understood that the disclosed devices, apparatuses, and methods can be implemented in other ways. The apparatus embodiments described above are merely illustrative. For example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. Furthermore, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Another point is that the displayed or discussed mutual coupling or direct coupling or communication connection may be through some communication interfaces; the indirect coupling or communication connection of devices or units may be electrical, mechanical, or other forms.

[0129] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0130] In addition, the functional units in the various embodiments of this disclosure can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0131] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a processor-executable, non-volatile, computer-readable storage medium. Based on this understanding, the technical solution of this disclosure, in essence, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this disclosure. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0132] Finally, it should be noted that the above-described embodiments are merely specific implementations of this disclosure, used to illustrate the technical solutions of this disclosure, and not to limit it. The protection scope of this disclosure is not limited thereto. Although this disclosure has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features, within the scope of the technology disclosed in this disclosure; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this disclosure, and should all be covered within the protection scope of this disclosure. Therefore, the protection scope of this disclosure should be determined by the protection scope of the claims.

Claims

1. An on-orbit geometric verification method for satellite altimetry data, characterized in that, The method includes: For each buoy in the buoy array, based on buoy observation data from the observation equipment installed on the buoy, multiple sea surface heights corresponding to the buoy are determined, and based on the sea surface height observation data along the orbit of the target satellite, the satellite observation sea surface height corresponding to the buoy is determined; the buoys in the buoy array are arranged according to the along-orbit baseline and the cross-orbit baseline, the along-orbit baseline being the surface projection of the center line of the target satellite's swath, and the cross-orbit baseline being perpendicular to the along-orbit baseline; Based on the satellite observation time and buoy observation time corresponding to each buoy, the effectiveness of multiple buoys is screened to determine multiple target buoys, and any two target buoys are paired to form a target buoy pair. For each target buoy pair, the double-difference residual corresponding to the target buoy pair is determined based on the satellite-observed sea surface height and the buoy-observed sea surface height corresponding to each target buoy in the target buoy pair; the buoy-observed sea surface height is determined based on multiple observed sea surface heights corresponding to the target buoy. For the baseline length between the two target buoys in each target buoy pair, the semi-variance value corresponding to the baseline length is determined based on the number of target buoy pairs that match the baseline length and the double-difference residuals corresponding to the target buoy pairs that match the baseline length. Obtain an exponential variogram model, which is used to indicate the mapping relationship between the semivariogram values ​​and the baseline length, the variance of satellite instrument background noise, and the variance of geophysical environmental error; Based on each of the baseline lengths and the corresponding semivariogram values, the exponential variogram model is fitted, and the variance of the satellite instrument background noise and the variance of the geophysical environment error are determined when the fitting error is minimized. Based on the sea surface height observed by the satellite and the sea surface height observed by the buoys corresponding to each target buoy arranged according to the cross-track baseline, the sea surface height residual corresponding to each target buoy arranged according to the cross-track baseline is determined; based on the sea surface height residual corresponding to each target buoy arranged according to the cross-track baseline and the cross-track distance, the roll error and phase error corresponding to the target satellite are determined. The verification result of the target satellite is determined based on the satellite instrument background noise variance, the geophysical environment error variance, the roll error, and the phase error.

2. The method according to claim 1, characterized in that, The observation equipment includes a Global Navigation Satellite System (GNSS) and an Inertial Navigation System. The observation equipment performs continuous single-point observations, and the buoy observation data includes dual-frequency observation values ​​and attitude angles at multiple buoy observation times. The determination of multiple sea surface heights corresponding to the buoy based on buoy observation data from observation equipment installed on the buoy includes: For each buoy observation time, based on the dual-frequency observation values ​​at that buoy observation time, the three-dimensional spatial coordinates of the buoy are determined, and the three-dimensional spatial coordinates are converted into the antenna phase center position of the GNSS; the antenna phase center position includes longitude, latitude, and sea surface height; Based on the attitude angle of the buoy during the observation time and the distance between the antenna phase center of the GNSS and the sea surface, the position of the antenna phase center is reduced to the buoy's centroid, and the antenna phase center position after being reduced to the buoy's centroid is reduced to the instantaneous sea surface to obtain the instantaneous sea surface position. The instantaneous sea surface height, including the instantaneous sea surface position, is filtered to obtain the filtered instantaneous sea surface height. The filtered instantaneous sea level is corrected according to the mean tide system matched with the target satellite to obtain the observed sea level of the buoy at the buoy observation time.

3. The method according to claim 1, characterized in that, The determination of the satellite-observed sea surface height corresponding to the buoy based on the target satellite's along-orbit sea surface height observation data includes: Extract the original sea surface height corresponding to each grid point within the target range centered on the buoy from the sea surface height observation data along the target satellite's orbit; The original sea level height is corrected for environmental errors to obtain the corrected sea level height. The buoy position is interpolated based on the corrected sea surface height to obtain the satellite-observed sea surface height corresponding to the buoy.

4. The method according to claim 3, characterized in that, The step of correcting the original sea level height for environmental errors to obtain the corrected sea level height includes: Environmental correction terms are extracted from the sea surface height observation data along the track. These environmental correction terms include ocean tide model correction terms, dynamic atmospheric correction terms, wet tropospheric delay correction terms, and sea state deviation correction terms. The original sea surface height is corrected for environmental errors based on the environmental correction terms to obtain the corrected sea surface height.

5. The method according to claim 1, characterized in that, The process of filtering the effectiveness of multiple buoys based on the satellite observation time and buoy observation time corresponding to each buoy, and determining multiple target buoys, includes: For each of the buoys, a mass marker is extracted from the sea level observation data along the track; When the quality indicator indicates that the quality of the orbital sea level height observation data is valid, the satellite observation time corresponding to the satellite-observed sea level height is extracted from the quality of the orbital sea level height observation data, and the buoy observation time corresponding to each observed sea level height is extracted from the buoy observation data. The coverage rate of the buoy observation time within the time window corresponding to the satellite observation time is determined. If the coverage rate is greater than the coverage rate threshold, the buoy is determined to be the target buoy.

6. The method according to claim 1, characterized in that, The method further includes: Based on the satellite-observed sea surface height and the buoy-observed sea surface height corresponding to each of the target buoys, determine the sea surface height residual corresponding to each of the target buoys; For the sea level residual sequence composed of each of the sea level residuals, the deviation range is determined based on the interquartile range of the sea level residual sequence; If the sea surface height residual corresponding to any of the target buoys exceeds the deviation range, the target buoys shall be eliminated. The step of forming a target buoy pair from any two target buoys includes: For the multiple target buoys remaining after the elimination process, any two target buoys are paired together to form a target buoy pair.

7. An on-orbit geometric verification device for satellite altimetry data, characterized in that, The device includes: The data acquisition module is used to determine multiple sea surface heights corresponding to each buoy in the buoy array based on buoy observation data from the observation equipment installed on the buoy, and to determine the satellite observation sea surface height corresponding to each buoy based on the sea surface height observation data along the orbit of the target satellite; the buoys in the buoy array are arranged according to the along-orbit baseline and the cross-orbit baseline, the along-orbit baseline being the surface projection of the center line of the target satellite's swath, and the cross-orbit baseline being perpendicular to the along-orbit baseline; The buoy screening module is used to screen multiple buoys for effectiveness based on the satellite observation time and buoy observation time corresponding to each buoy, determine multiple target buoys, and form a target buoy pair by any two target buoys. The dual-difference observation module is used to determine the dual-difference residual for each target buoy pair based on the satellite-observed sea surface height and the buoy-observed sea surface height corresponding to each target buoy in the target buoy pair; the buoy-observed sea surface height is determined based on multiple observed sea surface heights corresponding to the target buoy. The semi-variation determination module is used to determine the semi-variation value corresponding to the baseline length between the two target buoys in each target buoy pair, based on the number of target buoy pairs that match the baseline length and the double-difference residuals corresponding to the target buoy pairs that match the baseline length. The variance separation module is used to obtain an exponential variogram model, which indicates the mapping relationship between the semi-variogram values ​​and the baseline length, satellite instrument background noise variance, and geophysical environment error variance. Based on each baseline length and the corresponding semi-variogram values, the exponential variogram model is fitted, and the satellite instrument background noise variance and geophysical environment error variance are determined when the fitting error is minimized. The satellite instrument background noise variance and geophysical environment error variance are used to determine the verification result of the target satellite. The cross-track error detection module is used to determine the sea surface height residual corresponding to each target buoy arranged according to the cross-track baseline based on the satellite-observed sea surface height and the buoy-observed sea surface height corresponding to each target buoy arranged according to the cross-track baseline; and to determine the roll error and phase error corresponding to the target satellite based on the sea surface height residual corresponding to each target buoy arranged according to the cross-track baseline and the cross-track distance. The verification result determination module is used to determine the verification result of the target satellite based on the satellite instrument background noise variance, the geophysical environment error variance, the roll error, and the phase error.

8. A computer device, characterized in that, include: The computer device includes a processor, a memory, and a bus. The memory stores machine-readable instructions executable by the processor. When the computer device is running, the processor communicates with the memory via the bus. When the machine-readable instructions are executed by the processor, they perform the steps of the on-orbit geometric verification method for satellite altimetry data as described in any one of claims 1 to 6.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, performs the steps of the on-orbit geometric verification method for satellite altimetry data as described in any one of claims 1 to 6.

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