Sea surface elevation measurement method and device based on multi-angle SAR (Synthetic Aperture Radar) image in same flight

Abstract

The invention discloses a sea surface elevation measurement method and device based on co-flight multi-angle SAR (Synthetic Aperture Radar) images, and the method comprises the steps: determining the position information of a scene center point of each SAR image according to the co-flight SAR images, and cutting an auxiliary image according to the position information of the scene center point to obtain a cut auxiliary image; performing registration on the cut auxiliary image and the main image to obtain an offset of the main image and the cut auxiliary image, and performing interpolation processing on the cut auxiliary image according to the offset to obtain an interpolated auxiliary image and a slope distance of the interpolated auxiliary image; determining initial position information of the target point according to the slope distance of the corresponding pixel point; and correcting the initial position information according to the prior information of the sea surface topographic map to obtain sea surface elevation information of the target point. According to the method, the sea surface elevation can be determined by using the co-flight SAR image used for determining the flow velocity information, so that the sea surface flow velocity and the sea surface elevation at the same moment are obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of synthetic aperture radar data processing, and in particular relates to a method and a device for measuring sea surface elevation based on multi-angle SAR images in the same flight. Background Art

[0002] Sea surface height (SSH) is an important physical quantity that describes the vertical distance between the ocean surface and the reference ellipsoid. It is widely used in oceanography, meteorology, and environmental monitoring. Accurately obtaining sea surface elevation information is of great significance for studying ocean circulation, climate change, and marine disaster warning. Traditional sea surface elevation measurement methods mostly rely on satellite laser altimeters, buoy systems, and shipborne measurements. However, these methods have certain limitations, such as limited spatial coverage, limited measurement accuracy, and poor adaptability to sea surface conditions.

[0003] Synthetic Aperture Radar (SAR) has become one of the important technologies in the field of remote sensing due to its advantages such as all-weather, high resolution, and wide coverage. Especially in the field of ocean monitoring, SAR can overcome the limitations of optical remote sensing technology on weather and lighting conditions and obtain sea surface information through active beam illumination. In recent years, the use of SAR technology to measure sea surface elevation has become a research hotspot. In particular, through multi-angle observations combined with the stereo reconstruction technology of synthetic aperture radar images, the accuracy and reliability of sea surface elevation measurements can be improved.

[0004] At present, the cross-track interferometer satellite altimeter has been put into commercial use, which can obtain high-precision sea surface elevation data over a wide range of widths. At the same time, the sea surface current velocity measurement system based on multi-angle along-track interferometry technology, such as Figure 1 The Harmony satellite system in the 2013 Global Oceanographic Institutional Survey and Research Center has also entered the research stage. However, both sea surface elevation and current velocity have strong real-time characteristics, and how to obtain high-precision sea surface elevation and current velocity information at the same time is still an important problem that needs to be solved. Summary of the invention

[0005] The embodiment of the present invention provides a method for measuring sea surface elevation based on multi-angle SAR images obtained during the same flight, which can solve the problem that the sea surface elevation cannot be obtained by using multi-angle along-track interferometry technology.

[0006] In a first aspect, an embodiment of the present invention provides a method for measuring sea surface elevation based on multi-angle SAR images in a same-flight manner, the method comprising:

[0007] Determine the position information of the scene center point of each SAR image according to the same-flight SAR images, and crop the auxiliary image according to the position information of the scene center point to obtain a cropped auxiliary image, wherein the same-flight SAR images include at least two SAR images whose shooting scenes both include the target point but have different shooting angles;

[0008] The cropped auxiliary image and the main image are registered to obtain the offset between the main image and the cropped auxiliary image, and the cropped auxiliary image is interpolated according to the offset to obtain the interpolated auxiliary image and the slant range of the interpolated auxiliary image; wherein the main image is one of the SAR images in the same flight, and the auxiliary image is the remaining images in the SAR images in the same flight;

[0009] Determine the initial position information of the target point according to the slant distances of the corresponding pixel points, wherein a pair of corresponding pixel points includes a pixel of a main image and a pixel of an interpolated auxiliary image, and the shooting scene of the same pair of corresponding pixel points is the same;

[0010] The initial position information is corrected according to the prior information of the sea surface topography map to obtain the sea surface elevation information of the target point.

[0011] In a second aspect, an embodiment of the present invention provides a sea surface elevation measurement device based on multi-angle SAR images of the same flight, comprising:

[0012] An image cropping unit, the image cropping unit is used to determine the position information of the scene center point of each SAR image according to the same-flight SAR image, and to crop the auxiliary image according to the position information of the scene center point to obtain a cropped auxiliary image, wherein the same-flight SAR image includes at least two SAR images whose shooting scenes both include the target point but have different shooting angles;

[0013] A registration unit, the registration unit is used to register the cropped auxiliary image and the main image to obtain an offset between the main image and the cropped auxiliary image, and to interpolate the cropped auxiliary image according to the offset to obtain an interpolated auxiliary image and a slant range of the interpolated auxiliary image; wherein the main image is one of the SAR images in the same flight, and the auxiliary images are the remaining images in the SAR images in the same flight;

[0014] An initial position determination unit, the initial position determination unit is used to determine the initial position information of the target point according to the slant distance of the corresponding pixel points, wherein a pair of corresponding pixel points includes a pixel of a main image and a pixel of an interpolated auxiliary image, and the shooting scene of the same pair of corresponding pixel points is the same;

[0015] The sea surface elevation solving unit is used to correct the initial position information according to the prior information of the sea surface topography map to obtain the sea surface elevation information of the target point.

[0016] In a third aspect, an embodiment of the present invention provides a sea surface elevation measurement system based on multi-angle SAR images in a same-flight manner, comprising:

[0017] A plurality of groups of satellites in the same flight, wherein the plurality of groups of satellites in the same flight are used to obtain SAR images in the same flight, wherein the SAR images in the same flight include at least two SAR images whose shooting scenes both include a target point but have different shooting angles;

[0018] A sea surface elevation measurement device based on multi-angle SAR images in the same flight, wherein the sea surface elevation measurement device based on multi-angle SAR images in the same flight is used to determine the sea surface elevation information of the target point according to the multi-angle SAR images in the same flight based on the method provided in the first aspect.

[0019] In a fourth aspect, an embodiment of the present invention provides an electronic device, comprising a processor and a memory, wherein the memory is used to store computer programs; the processor can be used to execute the computer program (instructions) stored in the memory to implement the method of the first aspect above.

[0020] In a fifth aspect, an embodiment of the present invention provides a computer-readable storage medium, in which a computer program is stored. When the computer program is executed, the method of the first aspect described above can be implemented.

[0021] Compared with the prior art, the embodiments of the present invention have the following beneficial effects: according to the method provided by the present invention, by aligning the same-flight SAR images to obtain corresponding pixel points of the main image and the auxiliary image, the initial position information of the target point is determined according to the slant distance of the corresponding pixel points, and then the same-flight SAR images obtained based on the technology are corrected to obtain the sea surface elevation information, so that the sea surface flow velocity can be estimated using the multi-angle along-track interference technology while the sea surface elevation can be estimated using the same-flight SAR images obtained based on the technology, avoiding the need to obtain other information to estimate the sea surface elevation when estimating the flow velocity, thereby achieving simultaneous estimation of the flow velocity and the sea surface elevation. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic diagram of a Harmony satellite system;

[0023] Figure 2 A schematic diagram of a SAR stereo positioning geometric model provided by an embodiment of the present invention;

[0024] Figure 3 A flow chart of an implementation method of a sea surface elevation measurement method based on multi-angle SAR images provided by an embodiment of the present invention;

[0025] Figure 4 A schematic diagram of sea surface elevation information obtained based on the method provided by the present invention is provided in an embodiment of the present invention;

[0026] Figure 5 A flowchart of a registration method for co-flight SAR images provided by an embodiment of the present invention;

[0027] Figure 6 A schematic diagram of a co-flight SAR image provided by an embodiment of the present invention;

[0028] Figure 7 A schematic diagram of an offset matrix provided by an embodiment of the present invention;

[0029] Figure 8 A schematic diagram of the structure of a sea surface elevation measurement device based on multi-angle SAR images provided by an embodiment of the present invention;

[0030] Fig. 9 A schematic diagram of the structure of a sea surface elevation measurement system based on multi-angle SAR images provided by an embodiment of the present invention;

[0031] Fig.10 A schematic diagram of the structure of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0032] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention.

[0033] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0034] It should also be understood that the term "and / or" used in the present description and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0035] As used in the present specification and the appended claims, the term "if" may be interpreted as "when" or "upon" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" may be interpreted as meaning "upon determination" or "in response to determining" or "upon detection of [described condition or event]" or "in response to detecting [described condition or event]", depending on the context.

[0036] In addition, in the description of the present specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0037] References to "one embodiment" or "some embodiments" etc. described in the present specification mean that one or more embodiments of the present invention include specific features, structures or characteristics described in conjunction with the embodiment. Therefore, the statements "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear in different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0038] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0039] Figure 2 Shown is a schematic diagram of a SAR stereo positioning geometric model provided by an embodiment of the present invention.

[0040] See also Figure 2 , Figure 2 The figure shows a scene of joint observation of the same area from three perspectives. The red, yellow and green lines represent the radar line of sight directions of the three perspectives, and the angle between any two radar lines of sight represents the solid angle.

[0041] For example, the multi-angle along-track interferometry technology, namely the SAR stereo measurement technology, can extract three-dimensional surface information using the same-name points in SAR stereo images obtained from different observation angles.

[0042] Specifically, the distance equation and the Doppler equation can be established first according to the geometric relationship between each satellite and the ground target point; since the distance equation is related to the range pixel coordinates of the target point, and the Doppler equation is related to the azimuth pixel coordinates of the target point, the positioning equation group including these equations can be solved to obtain the azimuth pixel coordinates and the range pixel coordinates of each point in the shooting scene; finally, the azimuth coordinates and the distance coordinates of the target point are determined by matching the points with the same name, and the position information of the target point is obtained.

[0043] Exemplarily, the positioning equation group of the target point may satisfy the following formula:

[0044]

[0045] Among them, the slant range of R1 satellite 1, P S1 Coordinates of satellite 1, V S1 The speed of satellite 1, P T is the target point coordinate, the slant range of R2 satellite 2, P S2 The coordinates of satellite 2, f DC2 is the Doppler center of satellite 2, V S2 The speed of satellite 2, λ is the wavelength, R N The slant range of satellite N, P SN The coordinates of satellite N, V SN The speed of satellite N, f DCN The Doppler center of satellite N. Generally, the location information of the target point can be obtained by solving two equations.

[0046] It can be seen from the above formula (1.1) that the number of equations that can be established by the sea surface current satellite configuration represented by Harmony is much greater than 2; therefore, SAR stereo measurement technology is very suitable for extracting sea surface elevation. Therefore, the present invention proposes a sea surface elevation measurement method based on multi-angle SAR images in the same flight. This method can obtain sea surface elevation data while obtaining two-dimensional sea surface current information, and is particularly suitable for tasks represented by Harmony and other current measurement satellite systems. This method effectively improves the accuracy and spatial resolution of sea surface elevation measurement through stereo SAR imaging technology, providing more accurate data support for ocean monitoring.

[0047] The method provided in the embodiment of the present invention can be applied to electronic devices such as mobile terminals, personal notebook computers, supercomputers, etc. The embodiment of the present invention does not impose any limitation on the specific type of electronic devices.

[0048] Figure 3 The flowchart of the implementation of a method for measuring sea surface elevation based on multi-angle SAR images provided by an embodiment of the present invention is shown. As an example but not a limitation, the method may include steps S301-S305, and each step is described below:

[0049] S301, determining the location information of the scene center point of each SAR image according to the SAR image in the same flight.

[0050] For example, see Figure 2 SAR images of the same flight include at least two SAR images whose shooting scenes both include the target point but have different shooting angles.

[0051] In one example, the location information of the center point of the scene may be determined according to the center slant range of the co-flight SAR image and the antenna phase center at the center moment.

[0052] Generally, the center point of the scene of the same-flight SAR image (ie, the same-flight SAR image in the present invention) is the target point.

[0053] Exemplarily, the location information of the scene center point may satisfy the following formula:

[0054]

[0055] Among them, P T =[XYZ], req and rep are the equatorial radius and polar radius respectively, P cen is the antenna phase center at the center moment, R cen is the center slant range, and V is the speed of the satellite that obtains this SAR image.

[0056] S302: Crop the auxiliary image according to the position information of the scene center point to obtain a cropped auxiliary image.

[0057] In one example, the longitude and latitude of the four corners of the positioning scene can be determined based on the location information of the scene center point of each SAR image. One image is selected from the SAR images of the same flight as the main image, and the rest are auxiliary images. Then, the azimuth vector and range vector of the main image are determined based on the center time, center slant distance and location information of the scene center point of the main image. The cropping value of the auxiliary image is determined based on the location information of the scene center points of the main and auxiliary images and the azimuth vector and range vector of the main image. Finally, the auxiliary image is cropped according to the cropping value of the auxiliary image and the longitude and latitude of the four corners of the positioning scene to obtain a cropped auxiliary image.

[0058] Exemplarily, the azimuth vector and the distance vector of the main image may satisfy the following formulas respectively:

[0059] d az =(P cen -T cen )×T cen / ||T cen || / ||P cen -T cen || (1.3)

[0060] d ra =d az ×T cen / ||T cen || (1.4)

[0061] Among them, d az d ra They are the azimuth vector and distance vector of the main image respectively.

[0062] Exemplarily, the clipping value of the auxiliary image may satisfy the following formula:

[0063] na·daz +nr·d ra =T cen -P Tn (1.5)

[0064] Among them, na and nr are the cropping values ​​of the auxiliary image in two different dimensions, d az is the azimuth vector, d ra is the distance vector, T cen The location information of the scene center point of the main image, P Tn The location information of the scene center point of the auxiliary image.

[0065] S303, registering the main image and the cropped auxiliary image to obtain an offset between the main image and the cropped auxiliary image, and interpolating the cropped auxiliary image according to the offset to obtain an interpolated auxiliary image and a slant distance of the interpolated auxiliary image.

[0066] In one example, the main image and the cropped auxiliary image may be registered multiple times from the overall level to the pixel level and the sub-pixel level based on the amplitude coherence method to obtain the interpolated auxiliary image and the slant distance of the interpolated auxiliary image.

[0067] S304, determining the initial position information of the target point according to the slant distance of the corresponding pixel point.

[0068] For example, a pair of corresponding pixels may include a primary image pixel and an interpolated secondary image pixel. The corresponding pixels of the same pair have the same shooting scene.

[0069] In one example, the baseline between the main image and the interpolated auxiliary image can be calculated based on the slant distance of the corresponding pixel points, and the interpolated auxiliary image with the longest baseline between the main image and the main image is determined as the first auxiliary image. Then, based on the RD equation (i.e., the positioning equation group of the target point), the initial position information of the target point is solved according to the position information and speed information of the satellite of the first auxiliary image and the position information and speed information of the satellite of the main image.

[0070] Exemplarily, the RD equation constructed by the main image and the first auxiliary image may satisfy the following formula:

[0071]

[0072] Among them, R'1 is the slant range of the satellite that obtains the main image (i.e., the main satellite), P' S1 is the position coordinate of the main satellite, T cen is the location information of the scene center point of the main image above, f′ DC1 is the Doppler center of the main satellite, V′ S1is the speed of the main satellite; R′2 is the slant distance of the satellite that obtains the first auxiliary image (i.e., the first auxiliary satellite), P′ S2 is the position coordinate of the first auxiliary satellite, P′ Tn is the location information of the scene center point of the first image, f′ DC2 is the Doppler center of the first auxiliary satellite, V′ S2 is the speed of the first auxiliary satellite.

[0073] Specifically, the preliminary coordinates T0 of each pixel point (including the target point) in the main image can be obtained by solving the above RD equation.

[0074] S305, correcting the initial position information according to the prior information of the sea surface topography map to obtain the sea surface elevation information of the target point.

[0075] In a possible implementation, the sea surface elevation information of the target point can be obtained by correcting the initial position information based on the sea surface elevation solution model according to the prior information of the sea surface topography map (see Figure 4 ).

[0076] Exemplarily, the sea surface elevation solution model can satisfy the following formula:

[0077]

[0078] Among them, A is the differential matrix of the RD equation, the specific value of the differential matrix can be determined according to the initial position information, ΔT is the correction amount of the initial position information, b represents the error observation vector, α is the error amplification coefficient, f(|Hh|) is the heuristic function, H is the sea surface elevation information, and h is the prior information of the sea surface topography map.

[0079] in:

[0080] In one example, the RD equation constructed by all co-flight SAR images (see formula (1.1)) can be expanded, and then the expanded RD equation is differentiated to obtain the differential matrix of the stereo SAR target positioning equation.

[0081] Exemplarily, the expanded RD equation may satisfy the following formula:

[0082]

[0083] Among them, x S2 ,y S2 、z S2 are the coordinates P of satellite 2 S2 The x, y, and z axis values, x S1 ,y S1 、z S1 are the coordinates P of satellite 1S1 The x, y, and z axis values, x S3 ,y S2 、z S2 are the coordinates P of satellite 1 S1 The x, y, and z axis values, x SN ,y SN 、z SN are the coordinates P of satellite N respectively SN The x, y, and z axis values, x ST ,y ST 、z ST The coordinates of the target point are ST The x, y, and z axis values ​​of the .

[0084] For x in the expanded RD equation ST Taking the derivative we get:

[0085]

[0086] Where v is the modulus of V.

[0087] For T Taking the derivative we get:

[0088]

[0089] Right T Taking the derivative we get:

[0090]

[0091] From the above formulas (1.9)-(1.11), we can get the matrix form of the RD equation:

[0092]

[0093] Right now:

[0094] A·ΔT=b (1.13)

[0095] Thus, the differential matrix in the sea surface elevation solution model is obtained.

[0096] For example, the initial position information of the target point is substituted into the above formula (1.12) to calculate the slant range error ΔR of the initial position information. k and Doppler frequency error Δf DCk .

[0097] In one example, a sea surface elevation solution model can be constructed based on the conversion relationship between the WGS84 coordinate system and the latitude and longitude coordinate system. Since the sea surface elevation is generally approximately equal to 0, a penalty function can be introduced into the sea surface elevation solution model when using the least squares method to solve ΔT, thereby obtaining the above formula (1.7).

[0098] For example, the conversion relationship between the WGS84 coordinate system and the latitude and longitude coordinate system can satisfy the following formula:

[0099]

[0100] Where L is the geodetic longitude in the latitude coordinate system, B is the geodetic latitude in the latitude coordinate system, and H is the geodetic height in the latitude coordinate system (which can be regarded as the sea surface elevation for the sea surface). x″, y″, z″ are the coordinate values ​​of the x, y, and z axes in the WGS84 coordinate system, respectively, and N′=a e (1-e 2 sin 2 B) -1 / 2 , a e is the semi-major axis of the WGS-84 ellipsoid, e is the square of the first eccentricity of the Earth ellipsoid d = N'e 2 / (N′+H).

[0101] According to the method provided by the present invention, by aligning the same-flight SAR images to obtain corresponding pixel points of the main image and the auxiliary image, the initial position information of the target point is determined according to the slant distance of the corresponding pixel points, and then the same-flight SAR images obtained based on the technology are corrected to obtain the sea surface elevation information. This can achieve the estimation of the sea surface flow velocity using the multi-angle down-track interferometry technology while estimating the sea surface elevation using the same-flight SAR images obtained based on the technology, avoiding the need to obtain other information to estimate the sea surface elevation when estimating the flow velocity, thereby achieving simultaneous estimation of the flow velocity and the sea surface elevation.

[0102] Furthermore, the present invention only needs to deploy receivers on the ground to receive the existing co-orbital SAR images taken by co-orbital satellites, and these SAR images can be processed according to the method provided by the present invention to achieve high-precision, high-spatial-resolution two-dimensional sea surface flow field data inversion. Compared with the current method of specially launching aircraft and dedicated satellites to measure two-dimensional flow field data, the cost of the present invention is lower. At the same time, when acquiring co-orbital SAR data, it is only necessary to adjust the antenna angle of the receiver, and there is no need to let the satellite continuously observe the same scene, which is more practical.

[0103] Figure 5The flowchart of the implementation of a registration method for co-flight SAR images provided by an embodiment of the present invention is shown. As an example but not a limitation, the registration method is a specific possible implementation of step S303 in the above-mentioned sea surface elevation measurement method, and the registration method may include steps S501-S504, and each step is described below.

[0104] S501 , registering the main image and the cropped auxiliary image according to the amplitude matrix of the main image and the amplitude matrix of the cropped auxiliary image, and obtaining the overall offset of the cropped auxiliary image relative to the main image.

[0105] In a possible implementation, the main image (see Figure 6 ) and the amplitude matrix of the cropped auxiliary image are correlated with the entire co-aviation SAR image to obtain a first correlation coefficient matrix between the main image and each cropped auxiliary image; then the overall offset between the main image and the cropped auxiliary image is determined based on the coordinate difference between a pair of pixel points that obtains the maximum value of the first correlation coefficient matrix.

[0106] For example, a pair of pixel points that obtain the maximum value of the first correlation coefficient matrix are pixel point m1 of the main image K1 and pixel point m2 of the cropped auxiliary image K2. The overall offset of the cropped auxiliary image K2 relative to the main image can be obtained by subtracting the coordinate value of m1 from the coordinate value of m2.

[0107] In one example, the first correlation coefficient matrix may satisfy the following formula:

[0108]

[0109] Wherein, γ1 is the first correlation coefficient matrix, FFT(·) and IFFT(·) represent Fourier transform and inverse Fourier transform, respectively, u1 is the amplitude matrix of the main image, u2 is the amplitude matrix of the cropped auxiliary image, * represents the conjugate operation, M and N″ are the number of rows and columns of the amplitude matrix, respectively, and u1(i,j) and u2(i,j) represent the amplitude of the pixel in the i-th row and j-th column of the main image and the cropped auxiliary image, respectively.

[0110] S502: Perform pixel-level registration on the main image and the cropped auxiliary image according to the overall offset to obtain the offset of each group of first corresponding control blocks.

[0111] Exemplarily, a group of corresponding control blocks includes two mutually corresponding first main control blocks and first auxiliary control blocks, the first main control block is a sub-image of the main image, and the first auxiliary control block is a cropped sub-image of the auxiliary image.

[0112] Exemplarily, the shooting scene of the first auxiliary control block and the first main control block corresponding to each other is the same.

[0113] In a possible implementation, the main image can be divided into several first main control blocks, and then a slightly larger first auxiliary control block (for example, 2 or 3 pixels larger than the first main control block) corresponding to the first control block is taken from the cropped auxiliary image according to the overall offset, and then the correlation coefficients of each group of first main control blocks and first auxiliary control blocks are calculated to obtain the second correlation coefficient matrix of each group of first corresponding control blocks. Similarly, the difference between the coordinate values ​​of a pair of pixels that obtain the maximum value of the second correlation coefficient matrix is ​​used as the offset of the group of first corresponding control blocks.

[0114] For example, the correlation coefficient between pixel m3 in the first main control block K3 and pixel m4 in the corresponding first auxiliary control block K4 is the largest, and the offset of the first auxiliary control block K4 relative to the first main control block K3 can be obtained by subtracting the coordinate value of m3 from the coordinate value of m4.

[0115] Exemplarily, the offset of each group of first corresponding control blocks can be saved in the first offset matrix (see Figure 7 ) to facilitate subsequent calculations.

[0116] In one example, the first main control block can be slid from the upper left corner of the first auxiliary control block corresponding to it from left to right and from top to bottom. Each time it slides, the correlation coefficient of the overlapping part of the first main control block and the first auxiliary control block at the current position is calculated and stored in the second correlation coefficient matrix.

[0117] Exemplarily, the second correlation coefficient matrix may satisfy the following formula:

[0118]

[0119] Among them, γ2(m,n) represents the second similarity coefficient matrix of the first main control block with the upper left corner pixel coordinates (m,n), m′=m+Δm, n′=n+Δn, Δm and Δn are the overall row offset and column offset of the cropped auxiliary image relative to the main image, na′ and nr′ are the number of row pixels and column pixels of the first main control block, u′1 is the amplitude matrix of the first main control block, u′2 is the amplitude matrix of the first auxiliary control block, u′1(m+i′,n+j′) represents the amplitude of the pixel in the i′th row and j′th column of the first main control block, and u′2(m′+i′,n′+j′) represents the amplitude of the pixel in the i′th row and j′th column of the first auxiliary control block.

[0120] S503, interpolating the cropped auxiliary image to obtain an interpolated auxiliary image, and performing sub-pixel registration on the main image and the interpolated auxiliary image according to the offset of the first corresponding control block to obtain the offset of the second corresponding control block.

[0121] Similarly, a group of second corresponding control blocks includes two second main control blocks and a second auxiliary control block corresponding to each other. The second main control block is a sub-image of the main image, and the second auxiliary control block is a sub-image of the interpolated auxiliary image. The shooting scenes of the second main control block and the second auxiliary control block corresponding to each other are the same.

[0122] In a possible implementation, the cropped auxiliary image can be interpolated to an integer multiple of the original size. Similarly, the first main control block can continue to be processed as the second main control block, and a second auxiliary control block slightly larger than the second main control block can be taken from the interpolated auxiliary image according to the offsets Δm′ and Δn′ of the first corresponding control block. The correlation coefficient of each group of second corresponding control blocks is calculated to obtain the third correlation coefficient matrix of each group of second corresponding control blocks. Finally, the difference between the coordinate values ​​of a pair of pixels that obtain the maximum value of the third correlation coefficient matrix is ​​used as the offset of the second corresponding control block of the group.

[0123] In one example, the third correlation coefficient matrix may satisfy the following formula:

[0124]

[0125] Among them, γ3(m,n) represents the third similarity coefficient matrix of the second main control block with the upper left corner pixel coordinates of (m,n), na″ and nr″ respectively represent the number of row pixels and column pixels of the second main control block, u″1 is the amplitude matrix of the second main control block, u″1(m+i″,n+j″) represents the amplitude of the i″th row and j″th column pixel in the second main control block, u″2 represents the amplitude matrix of the second auxiliary control block, u″2(m″+i″,n″+j″) represents the amplitude of the i″th row and j″th column pixel in the second auxiliary control block with the upper left corner pixel coordinates of (m″,n″), m″=m+Δm′, n″=n+Δn′.

[0126] S504: re-interpolate the slant distance of the interpolated auxiliary image according to the offset of the second corresponding control block to obtain the slant distance of the interpolated auxiliary image.

[0127] Exemplarily, if the offset of the second corresponding control block is Δm″, Δn″, a pair of corresponding pixel points can be a pixel with coordinates (m, n) in the main image and a pixel with coordinates (m+Δm″, n+Δn″) in the cropped auxiliary image.

[0128] Figure 8 The structure diagram of a sea surface elevation measurement device based on multi-angle SAR images provided by an embodiment of the present invention is shown. As an example but not a limitation, the device 800 may include an image cropping unit 810, a registration unit 820, an initial position determination unit 830, and a sea surface elevation solution unit 840.

[0129] Exemplarily, the image cropping unit 810 is used to determine the position information of the scene center point of each SAR image according to the same-flight SAR image, and to crop the auxiliary image according to the position information of the scene center point to obtain a cropped auxiliary image, wherein the same-flight SAR image includes at least two SAR images whose shooting scenes both include the target point but have different shooting angles; the registration unit 820 is used to register the cropped auxiliary image and the main image to obtain the offset between the main image and the cropped auxiliary image, and to interpolate the cropped auxiliary image according to the offset to obtain the interpolated auxiliary image and the slant distance of the interpolated auxiliary image; wherein the main image is an image in the same-flight SAR image, and the auxiliary image is the remaining images in the same-flight SAR image; the initial position determination unit 830 is used to determine the initial position information of the target point according to the slant distance of the corresponding pixel points, wherein a pair of corresponding pixel points includes a pixel of the main image and a pixel of the interpolated auxiliary image, and the shooting scene of the same pair of corresponding pixel points is the same; the sea surface elevation solution unit 840 is used to correct the initial position information according to the prior information of the sea surface topography map to obtain the sea surface elevation information of the target point.

[0130] According to the device provided by the present invention, by aligning the same-flight SAR images to obtain corresponding pixel points of the main image and the auxiliary image, the initial position information of the target point is determined according to the slant distance of the corresponding pixel points, and then the same-flight SAR images obtained based on the technology are corrected to obtain the sea surface elevation information. This can achieve the estimation of the sea surface flow velocity using the multi-angle down-track interferometry technology while estimating the sea surface elevation using the same-flight SAR images obtained based on the technology, avoiding the need to obtain other information to estimate the sea surface elevation when estimating the flow velocity, thereby achieving simultaneous estimation of the flow velocity and the sea surface elevation.

[0131] Fig. 9 The structure diagram of a sea surface elevation measurement system based on co-flying multi-angle SAR images provided by an embodiment of the present invention is shown. As an example but not a limitation, the system 900 may include multiple groups of co-flying satellites 910 (only one is shown here) and the above-mentioned device 800.

[0132] The satellite 910 can be used to obtain the SAR image, and the device 800 can be used to determine the sea surface elevation information of the target point according to the SAR image based on the above measurement method.

[0133] According to the system provided by the present invention, by aligning the same-flight SAR images to obtain corresponding pixel points of the main image and the auxiliary image, the initial position information of the target point is determined according to the slant distance of the corresponding pixel points, and then the same-flight SAR images obtained based on the technology are corrected to obtain the sea surface elevation information. This can achieve the estimation of the sea surface flow velocity using the multi-angle along-track interferometry technology while estimating the sea surface elevation using the same-flight SAR images obtained based on the technology, avoiding the need to obtain other information to estimate the sea surface elevation when estimating the flow velocity, thereby achieving simultaneous estimation of the flow velocity and the sea surface elevation.

[0134] Fig.10 FIG. 1 is a schematic diagram of the structure of an electronic device provided by an embodiment of the present invention. Fig.10 The electronic device 1000 shown may include: at least one processor 1010 ( Fig.10 Only one processor is shown in the figure), a memory 1020, and a computer program 1030 stored in the memory 1020 and executable on the at least one processor 1010, wherein the processor 1010 implements the steps of any of the above-mentioned method embodiments when executing the computer program 1030.

[0135] The electronic device 1000 may be a processing device such as a robot that can implement the above method. The embodiment of the present invention does not impose any limitation on the specific type of the electronic device.

[0136] Those skilled in the art will understand that Fig.10 The electronic device 1000 is merely an example and does not constitute a limitation on the electronic device. The electronic device 1000 may include more or fewer components than shown in the figure, or may combine certain components, or may include different components. For example, the electronic device 1000 may also include an input and output interface.

[0137] The processor 1010 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASTC), field programmable gate arrays (FPGA), or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc.

[0138] The memory 1020 may be an internal storage unit in some embodiments, such as a hard disk or a memory. The memory 1020 may also be an external storage device in other embodiments, such as a plug-in hard disk, a smart memory card (SmartMemory Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), etc. Further, the memory 1020 may also include both an internal storage unit and an external storage device. The memory 1020 is used to store an operating system, an application, a boot loader (Boot Loader), data, and other programs, such as the program code of the computer program, etc. The memory 1020 may also be used to temporarily store data that has been output or is to be output.

[0139] It should be understood that the order of execution of the steps in the above embodiment does not necessarily mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0140] Those skilled in the art can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In practical applications, the above-mentioned function allocation can be completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated into a processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of the present invention. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, which will not be repeated here.

[0141] An embodiment of the present invention further provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps in the above-mentioned method embodiments can be implemented.

[0142] An embodiment of the present invention provides a computer program product. When the computer program product runs on an electronic device, the electronic device can implement the steps in the above-mentioned method embodiments when executing the computer program product.

[0143] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, which can be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by the processor, the steps of the above-mentioned various method embodiments can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium can at least include: any entity or device that can carry the computer program code to the camera / terminal device, recording medium, computer memory, read-only memory (ROM, Read-Only Memory), random access memory (RAM, RandomAccess Memory), electric carrier signal, telecommunication signal and software distribution medium. For example, a USB flash drive, a mobile hard disk, a magnetic disk or an optical disk. In some jurisdictions, according to legislation and patent practice, computer-readable media cannot be electric carrier signals and telecommunication signals.

[0144] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0145] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

Claims

1. A method for measuring sea surface elevation based on multi-angle SAR images taken in the same flight, characterized in that: include: Determine the position information of the scene center point of each SAR image according to the same-flight SAR images, and crop the auxiliary image according to the position information of the scene center point to obtain a cropped auxiliary image, wherein the same-flight SAR images include at least two SAR images whose shooting scenes both include the target point but have different shooting angles; The cropped auxiliary image and the main image are registered to obtain an offset between the main image and the cropped auxiliary image, and the cropped auxiliary image is interpolated according to the offset to obtain an interpolated auxiliary image and a slant range of the interpolated auxiliary image; wherein the main image is one of the same-flight SAR images, and the auxiliary images are the remaining images in the same-flight SAR images; Determine the initial position information of the target point according to the slant distance of the corresponding pixel points, wherein a pair of corresponding pixel points includes a pixel of the main image and a pixel of the interpolated auxiliary image, and the shooting scene of the same pair of corresponding pixel points is the same; The initial position information is corrected according to the prior information of the sea surface topography map to obtain the sea surface elevation information of the target point.

2. The method according to claim 1, characterized in that The step of cropping the auxiliary image according to the position information of the center point of the scene to obtain a cropped auxiliary image includes: Determine the azimuth vector and the range vector of the main image according to the center time, the center slant distance and the position information of the center point of the scene of the main image; Determine the cropping value of the auxiliary image according to the position information of the scene center point of the auxiliary image and the position information, the azimuth vector, and the distance vector of the scene center point of the main image; The auxiliary image is cropped according to the cropping value to obtain the cropped auxiliary image.

3. The method according to claim 2, characterized in that The clipping value satisfies the following formula: na·daz+nr·dra=Tcen-PTn Among them, na and nr are the cropping values ​​of two different dimensions of the auxiliary image, daz is the azimuth vector, dra is the distance vector, Tcen is the position information of the scene center point of the main image, and PTn is the position information of the scene center point of the auxiliary image.

4. The method according to claim 1, characterized in that: The registering the cropped auxiliary image and the main image to obtain the integral offset between the main image and the cropped auxiliary image, and interpolating the cropped auxiliary image according to the offset to obtain the interpolated auxiliary image and the slant distance of the interpolated auxiliary image, comprises: Registering the main image and the cropped auxiliary image according to the amplitude matrix of the main image and the amplitude matrix of the cropped auxiliary image to obtain an overall offset of the cropped auxiliary image relative to the main image; Performing pixel-level registration on the main image and the cropped auxiliary image according to the overall offset to obtain an offset of each group of first corresponding control blocks, wherein a group of the first corresponding control blocks includes two mutually corresponding first main control blocks and a first auxiliary control block, the mutually corresponding first auxiliary control blocks and the first main control block have the same shooting scene, the first main control block is a sub-image of the main image, the first auxiliary control block is a sub-image of the cropped auxiliary image, and the size of the first auxiliary control block is larger than the first main control block; performing interpolation processing on the cropped auxiliary image to obtain an interpolated auxiliary image, and performing sub-pixel registration on the main image and the interpolated auxiliary image according to the offset of the first corresponding control block to obtain the offset of the second corresponding control block, wherein the second corresponding control block includes a pair of second main control blocks and second auxiliary control blocks corresponding to each other, the shooting scene of the second auxiliary control blocks and the second main control blocks corresponding to each other is the same, the second main control block is a sub-image of the main image, the second auxiliary control block is a sub-image of the interpolated auxiliary image, and the size of the second auxiliary control block is larger than that of the second main control block; The slant distance of the interpolated auxiliary image is re-interpolated according to the offset of the second corresponding control block to obtain the slant distance of the interpolated auxiliary image.

5. The method according to claim 1, characterized in that The determining the initial position information of the target point according to the slant distance of the corresponding pixel point includes: Selecting a first auxiliary image from the auxiliary images according to the slant distances of the corresponding pixel points; The initial position information is determined based on the RD equation according to the position information and speed information of the satellite of the first auxiliary image and the position information and speed information of the satellite of the main image.

6. The method according to claim 1, characterized in that The step of correcting the initial position information according to the prior information of the sea surface topography map to obtain the sea surface elevation information of the target point includes: Based on the sea surface elevation solution model, the initial position information is corrected according to the prior information of the sea surface topography map to obtain the sea surface elevation information of the target point; The sea surface elevation solution model satisfies the following formula: Among them, A is the differential matrix of the RD equation, the specific value of the differential matrix can be determined according to the initial position information, ΔT is the correction amount of the initial position information, b represents the error observation vector, α is the error amplification coefficient, f(Hh|) is the heuristic function, H is the sea surface elevation information, and h is the prior information of the sea surface topography map.

7. A sea surface elevation measurement device based on multi-angle SAR images taken in the same flight, characterized in that: include: An image cropping unit, the image cropping unit is used to determine the position information of the scene center point of each SAR image according to the same-flight SAR image, and to crop the auxiliary image according to the position information of the scene center point to obtain a cropped auxiliary image, wherein the same-flight SAR image includes at least two SAR images whose shooting scenes both include the target point but have different shooting angles; A registration unit, the registration unit is used to register the cropped auxiliary image and the main image to obtain an offset between the main image and the cropped auxiliary image, and to interpolate the cropped auxiliary image according to the offset to obtain an interpolated auxiliary image and a slant range of the interpolated auxiliary image; wherein the main image is an image in the same-flight SAR image, and the auxiliary image is the remaining images in the same-flight SAR image; an initial position determination unit, the initial position determination unit being used to determine the initial position information of the target point according to the slant distances of corresponding pixel points, wherein a pair of corresponding pixel points includes a pixel of the main image and a pixel of the interpolated auxiliary image, and the shooting scene of the same pair of corresponding pixel points is the same; The sea surface elevation solving unit is used to correct the initial position information according to the prior information of the sea surface topography map to obtain the sea surface elevation information of the target point.

8. A sea surface elevation measurement system based on multi-angle SAR images taken in the same flight, characterized in that: include: A plurality of groups of satellites in the same flight, wherein the plurality of groups of satellites in the same flight are used to obtain SAR images in the same flight, wherein the SAR images in the same flight include at least two SAR images whose shooting scenes both include a target point but have different shooting angles; A sea surface elevation measurement device based on multi-angle SAR images in the same flight, wherein the sea surface elevation measurement device based on multi-angle SAR images in the same flight is used to determine the sea surface elevation information of the target point based on the multi-angle SAR images in the same flight based on the method described in any one of claims 1 to 6.

9. An electronic device comprising a memory, a processor and a computer program stored in the memory, characterized in that: When the processor executes the computer program, the method according to any one of claims 1 to 6 is implemented.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by the electronic device, the method according to any one of claims 1 to 6 is implemented.

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