Sea surface height measurement method and device based on same-pass multi-angle SAR images

Abstract

The application discloses a sea surface height measurement method and device based on same-pass multi-angle SAR images, and the method comprises the following steps: determining the position information of the scene center point of each SAR image according to the same-pass SAR images, and cutting the auxiliary image according to the position information of the scene center point to obtain a cut auxiliary image; registering the cut auxiliary image and the main image to obtain the 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 the slant distance of the interpolated auxiliary image; determining the initial position information of the target point according to the slant distance of the corresponding pixel point; and correcting the initial position information according to the sea surface topographic map prior information to obtain the sea surface height information of the target point. The sea surface height can be determined by using the same-pass SAR images used for determining the flow velocity information, so that the sea surface flow velocity and the sea surface height at the same time can be obtained.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of synthetic aperture radar data processing, and particularly relates to a sea surface height measurement method and device based on same-pass multi-angle SAR images. BACKGROUND

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

[0003] Synthetic Aperture Radar (SAR) has become an important technology in the field of remote sensing due to its all-weather, high-resolution, and wide coverage. In particular, in marine monitoring, SAR can overcome the limitations of optical remote sensing technology due to weather and lighting conditions, and obtain sea surface information through active beam illumination. In recent years, using SAR technology for sea surface height measurement has become a research hotspot. In particular, through multi-angle observation, combined with the stereo reconstruction technology of synthetic aperture radar images, the accuracy and reliability of sea surface height measurement can be improved.

[0004] Currently, cross-track interferometric satellite altimeters have been put into commercial application and can obtain high-precision sea surface height data with a wide swath. At the same time, sea surface current measurement systems based on multi-angle along-track interferometry technology, such as the Harmony satellite system in Figure 1 , have also entered the research stage. However, sea surface height and flow rate both have strong real-time characteristics, and how to simultaneously obtain high-precision sea surface height and flow rate information at the same time is still an important problem to be solved. SUMMARY

[0005] The embodiment of the application provides a sea surface height measurement method based on same-pass multi-angle SAR images, which can solve the problem that the multi-angle along-track interferometry technology cannot be used to obtain sea surface height.

[0006] In a first aspect, the embodiment of the application provides a sea surface height measurement method based on same-pass multi-angle SAR images, and the method comprises the following steps:

[0007] The position information of the scene center point of each SAR image is determined according to the same-pass SAR images, and the auxiliary image is cropped according to the position information of the scene center point to obtain a cropped auxiliary image, wherein the same-pass SAR images include at least two SAR images whose scenes include the target point but have different shooting angles.

[0008] The offset between the main image and the cropped auxiliary image is obtained by registering the cropped auxiliary image and the main image, and the auxiliary image after interpolation is obtained by interpolating the cropped auxiliary image according to the offset, and the slant range of the auxiliary image after interpolation; wherein the main image is one of the same-pass SAR images, and the auxiliary image is the rest of the same-pass SAR images.

[0009] The initial position information of the target point is determined according to the slant range of the corresponding pixel points, wherein a pair of corresponding pixel points includes a pixel of the main image and a pixel of the auxiliary image after interpolation, and the same pair of corresponding pixel points has the same shooting scene.

[0010] The sea surface elevation information of the target point is obtained by correcting the initial position information according to the sea surface topographic map prior information.

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

[0012] An image cropping unit is configured to determine the position information of the scene center point of each SAR image according to the same-pass SAR images, 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-pass SAR images include at least two SAR images whose scenes include the target point but have different shooting angles.

[0013] A registration unit is configured 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 obtain the auxiliary image after interpolation by interpolating the cropped auxiliary image according to the offset, and to obtain the slant range of the auxiliary image after interpolation; wherein the main image is one of the same-pass SAR images, and the auxiliary image is the rest of the same-pass SAR images.

[0014] An initial position determination unit is configured to determine the initial position information of the target point according to the slant range of the corresponding pixel points, wherein a pair of corresponding pixel points includes a pixel of the main image and a pixel of the auxiliary image after interpolation, and the same pair of corresponding pixel points has the same shooting scene.

[0015] A sea surface elevation solving unit is configured to obtain the sea surface elevation information of the target point by correcting the initial position information according to the sea surface topographic map prior information.

[0016] In a third aspect, an embodiment of the present application provides a sea surface height measurement system based on same-pass multi-angle SAR images, comprising:

[0017] A plurality of same-pass satellites, configured to acquire same-pass SAR images, wherein the same-pass SAR images comprise SAR images of at least two scenes, each of which comprises a target point but has different angles of view;

[0018] A sea surface height measurement device based on same-pass multi-angle SAR images, configured to determine sea surface height information of a target point based on the method provided in the first aspect and the same-pass SAR images.

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

[0020] In a fifth aspect, an embodiment of the present application provides a computer readable storage medium, which stores a computer program, and when the computer program is executed, the method of the first aspect can be implemented.

[0021] Compared with the prior art, the method provided by the present application has the beneficial effects that: according to the method provided by the present application, the corresponding pixel points of the main image and the auxiliary image are obtained by registering the same-pass SAR images, the initial position information of the target point is determined according to the slant range of the corresponding pixel points, and the sea surface height information is obtained by correcting the initial position information, so that the sea surface height can be estimated using the same-pass SAR images obtained based on the multi-angle along-track interferometry technology while estimating the sea surface flow velocity, and the sea surface height can be estimated using the remaining information when estimating the flow velocity, thereby realizing the simultaneous estimation of the flow velocity and the sea surface height. BRIEF DESCRIPTION OF DRAWINGS

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

[0023] Figure 2 FIG. 5 is a schematic diagram of a SAR stereoscopic positioning geometric model provided by an embodiment of the present application;

[0024] Figure 3 FIG. 8 is a flowchart of a sea surface height measurement method based on same-pass multi-angle SAR images provided by an embodiment of the present application;

[0025] Figure 4 FIG. 11 is a schematic diagram of sea surface height information acquired based on the method provided by an embodiment of the present application;

[0026] Figure 5 An implementation flowchart of a registration method of same-pass SAR images provided by an embodiment of the present application is shown in FIG. 1.

[0027] Figure 6 A schematic diagram of same-pass SAR images provided by an embodiment of the present application is shown in FIG. 2.

[0028] Figure 7 A schematic diagram of an offset matrix provided by an embodiment of the present application is shown in FIG. 3.

[0029] Figure 8 A structural schematic diagram of a sea surface height measuring device based on same-pass multi-angle SAR images provided by an embodiment of the present application is shown in FIG. 4.

[0030] Figure 9 A structural schematic diagram of a sea surface height measuring system based on same-pass multi-angle SAR images provided by an embodiment of the present application is shown in FIG. 5.

[0031] Figure 10 A structural schematic diagram of an electronic device provided by an embodiment of the present application is shown in FIG. 6. DETAILED DESCRIPTION

[0032] In the following description, specific details are set forth, such as a particular system architecture, techniques, etc., in order to provide a thorough understanding of the embodiments of the present application. However, persons skilled in the art will understand that the present application can be practiced without these specific details. In other instances, well-known systems, structures, circuits, and techniques have not been shown in detail in order not to obscure the understanding of this description.

[0033] It should be understood that the term "comprises / comprising" when used in this specification and associated claims, denotes the presence of stated features, integers, steps, operations, elements, and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0034] It is also to be understood that the term "and / or" when used in this specification and associated claims, means that any combination of the associated listed items can be present, and all possible combinations are included.

[0035] As used in this specification and associated claims, the term "if' can be construed to mean "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 [a described condition or event] is detected" can be construed to mean "upon determining" or "in response to determining" or "upon detecting [the described condition or event]" or "in response to detecting [the described condition or event]," depending on the context.

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

[0037] In the present application, the reference to "one embodiment" or "some embodiments" and the like means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the application. Thus, the appearances of the phrases "in one embodiment", "in some embodiments", "in other embodiments", "in additional embodiments" and so on, in various places in the specification are not necessarily all referring to the same embodiment, unless otherwise specifically stated. The terms "comprising", "including", "having" and their variants mean "including but not limited to", unless otherwise specifically stated.

[0038] The application will be further described in detail below in conjunction with specific embodiments, but the embodiments of the application are not limited thereto.

[0039] Figure 2 A schematic diagram of a SAR stereoscopic positioning geometric model provided by an embodiment of the application is shown.

[0040] Referring to Figure 2 , Figure 2 A scene of joint observation of the same area from three perspectives is shown, and the radar line-of-sight directions of the three perspectives are represented by red, yellow and green lines respectively, and the included angle between any two radar lines of sight represents a solid angle.

[0041] For example, the multi-angle along-track interferometry technology, i.e. the SAR stereoscopic measurement technology, can use the same points in the SAR stereoscopic images obtained from different observation perspectives to extract the three-dimensional information of the ground surface.

[0042] Specifically, a distance equation and a Doppler equation can be established according to the geometric relationship between each satellite and the ground target point. Since the distance equation is related to the distance of the target point to the pixel coordinates, and the Doppler equation is related to the azimuth of the target point to the pixel coordinates, the positioning equation set including these equations can be solved to obtain the azimuth pixel coordinates and the distance pixel coordinates of each point in the shooting scene. Finally, the azimuth coordinates and the distance coordinates of the target point are determined through the matching of the same points to obtain the position information of the target point.

[0043] For example, the positioning equation set of the target point can satisfy the following formula:

[0044]

[0045] Wherein, R1 is the slant range of satellite 1, P S1 Coordinates of satellite 1, V S1 Velocity of satellite 1, P T Coordinates of target point, R2 is the slant range of satellite 2, P S2 Coordinates of satellite 2, f DC2 Doppler center of satellite 2, V S2 Velocity of satellite 2, λ is wavelength, R N Slant range of satellite N, P SN Coordinates of satellite N, V SN Velocity of satellite N, f DCN Doppler center of satellite N. Generally, the position information of the target point can be obtained by solving two equations.

[0046] As can be seen from the above formula (1.1), the number of equations that can be established by the sea surface flow velocity satellite configuration represented by Harmony is much greater than 2; therefore, the SAR stereoscopic measurement technology is very suitable for extracting the sea surface height. Therefore, the present application proposes a sea surface height measurement method based on the same navigation over multi-angle SAR image, which can obtain the sea surface height data while obtaining the two-dimensional flow velocity information of the sea surface, and is especially suitable for the task represented by the sea current measurement satellite system such as Harmony. This method effectively improves the accuracy and spatial resolution of sea surface height measurement through stereoscopic SAR imaging technology, and provides more accurate data support for marine monitoring.

[0047] The method provided by the embodiment of the present application can be applied to electronic devices such as mobile terminals, personal notebook computers, supercomputers and the like, and the embodiment of the present application does not make any limitation on the specific type of the electronic device.

[0048] Figure 3 An implementation flowchart of the sea surface height measurement method based on the same navigation over multi-angle SAR image provided by the embodiment of the present application is shown. As an example but not limitation, the method can include steps S301-S305, which are described as follows:

[0049] S301, the position information of the scene center point of each SAR image is determined according to the same navigation SAR image.

[0050] For example, referring to Figure 2 The same navigation SAR image includes at least two SAR images which have different shooting angles but both include the target point.

[0051] In one example, the position information of the scene center point can be determined according to the center slant range and the antenna phase center at the center time of the same navigation SAR image.

[0052] Generally, the scene center point of the same-pass SAR image (i.e., the same-pass SAR image in the present application) is the target point.

[0053] For example, the position information of the scene center point can satisfy the following formula:

[0054]

[0055] wherein P T =[X Y Z], req and rep are the equatorial radius and polar radius respectively, P cen is the antenna phase center at the center time, R cen is the central slant range, and V is the speed of the satellite obtaining the SAR image.

[0056] S302, the secondary image is cropped according to the position information of the scene center point to obtain the cropped secondary image.

[0057] In one example, the longitude and latitude of the four corners of the positioning scene can be determined according to the position information of the scene center point of each SAR image. One image is selected from the same-pass SAR images as the primary image, and the rest are secondary images. Then, the azimuth vector and the range vector of the primary image are determined according to the center time, the central slant range and the position information of the scene center point of the primary image. The cropping value of the secondary image is determined according to the position information of the scene center point of the primary and secondary images and the azimuth vector and the range vector of the primary image. Finally, the secondary image is cropped according to the cropping value of the secondary image and the longitude and latitude of the four corners of the positioning scene to obtain the cropped secondary image.

[0058] For example, the azimuth vector and the range vector of the primary image can satisfy the following formula 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] wherein d az and d ra are the azimuth vector and the range vector of the primary image respectively.

[0062] For example, the cropping value of the secondary image can satisfy the following formula:

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

[0064] wherein na, nr are the clipping values of the two different dimensions of the auxiliary image respectively, d az is the azimuth vector, d ra is the range vector, T cen is the position information of the scene center point of the main image, P Tn is the position information of the scene center point of the auxiliary image.

[0065] S303, the main image and the clipped auxiliary image are registered to obtain the offset between the main image and the clipped auxiliary image, and the clipped auxiliary image is interpolated according to the offset to obtain the interpolated auxiliary image and the slant range of the interpolated auxiliary image.

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

[0067] S304, the initial position information of the target point is determined according to the slant range of the corresponding pixel points.

[0068] Exemplarily, a pair of corresponding pixel points can include one main image pixel and one pixel of the interpolated auxiliary image. The same pair of corresponding pixel points has the same shooting scene.

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

[0070] Exemplarily, the R-D equation constructed by the main image and the first auxiliary image can satisfy the following formula:

[0071]

[0072] wherein R'1 is the slant range of the satellite obtaining the main image (i.e. the main satellite), P' S1 is the position coordinates of the main satellite, T cen is the position information of the scene center point of the main image, f' DC1 is the Doppler center of the main satellite, V' S1is the velocity of the primary satellite; R'2 is the slant range of the satellite (i.e., the first auxiliary satellite) that obtains the first auxiliary image, P' S2 is the position coordinate of the first auxiliary satellite, P' Tn is the position 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 velocity of the first auxiliary satellite.

[0073] Specifically, the preliminary coordinates T0 of each pixel point (including the target point) in the primary image can be obtained according to the above R-D equation.

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

[0075] In one possible implementation, the initial position information can be corrected according to the sea surface topographic map prior information to obtain the sea surface elevation information of the target point based on a sea surface elevation solving model (see Figure 4 ).

[0076] For example, the sea surface elevation solving model can satisfy the following formula:

[0077]

[0078] wherein A is the differential matrix of the R-D 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(|H-h|) is the heuristic function, H is the sea surface elevation information, and h is the sea surface topographic map prior information.

[0079] wherein:

[0080] In one example, the R-D equation constructed by all the same navigation SAR images (see formula (1.1)) can be expanded, and then the differential matrix of the stereoscopic SAR target positioning equation can be obtained by differentiating the expanded R-D equation.

[0081] For example, the expanded R-D equation can satisfy the following formula:

[0082]

[0083] wherein x S2 , y S2 , z S2 are the x, y, z axis values of the coordinates P S2 of satellite 2, x S1 , y S1 , z S1 are the x, y, z axis values of the coordinates PS1 x, y, z axis values of the coordinate P of satellite 1, x S3 , y S2 , z S2 respectively. S1 x, y, z axis values of the coordinate P of satellite N, x SN , y SN , z SN respectively. SN x, y, z axis values of the coordinate P of satellite N, x ST , y ST , z ST respectively. ST x, y, z axis values of the coordinate P of satellite N, x

[0084] The derivative of x ST in the R-D equation after unfolding can be obtained as follows:

[0085]

[0086] wherein v is the modulus of V.

[0087] The derivative of y T can be obtained as follows:

[0088]

[0089] The derivative of z T can be obtained as follows:

[0090]

[0091] The matrix form of the R-D equation can be obtained from the above formulas (1.9)-(1.11) as follows:

[0092]

[0093] That is:

[0094] A·ΔT=b (1.13)

[0095] Thus the differential matrix in the sea surface height solving model is obtained.

[0096] Exemplarily, the slant range error ΔR k and the Doppler frequency error Δf DCk of the initial position information of the target point can be obtained by substituting the initial position information of the target point into the above formula (1.12) for calculation.

[0097] In one example, a sea surface elevation 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 model when solving ΔT using the least squares method, resulting in 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 latitudinal coordinate system, B is the geodetic latitude in the latitudinal coordinate system, and H is the geodetic height in the latitudinal coordinate system (which can be regarded as the sea level elevation for the sea surface). x″, y″, and z″ are the coordinate values ​​of the x, y, and z axes in the WGS84 coordinate system, respectively. 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 co-orbital SAR images to obtain corresponding pixel points of the main image and the auxiliary image, determining the initial position information of the target point based on the slant distance of the corresponding pixel points, and then correcting the initial position information to obtain the sea surface elevation information, it is possible to simultaneously estimate the sea surface flow velocity using the multi-angle down-track interferometry technology and use the co-orbital SAR images obtained based on the technology to estimate the sea surface elevation, 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 requires ground-based receivers to receive existing co-orbital SAR images captured by co-orbital satellites. These SAR images can be processed using the method provided by the present invention to achieve high-precision, high-spatial-resolution two-dimensional sea surface flow field data inversion. Compared to current methods that require the special launch of aircraft and dedicated satellites to measure two-dimensional flow field data, the present invention is less expensive. Furthermore, when acquiring co-orbital SAR data, only the receiver antenna angle needs to be adjusted, eliminating the need for satellites to continuously observe the same scene, making it more practical.

[0103] Figure 5An implementation flowchart of a registration method of co-passing SAR images is shown. As an example but not limitation, the registration method is a specific possible implementation of step S303 in the sea surface height measurement method, and the registration method can include steps S501-S504, which are described below.

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

[0105] In a possible implementation, the overall of the co-passing SAR images can be correlated according to the amplitude matrix of the main image (see Figure 6 ) and the amplitude matrix of the cropped auxiliary image to obtain the first correlation coefficient matrix between the main image and each cropped auxiliary image; and then the overall offset between the main image and the cropped auxiliary image is determined according to the coordinate difference between the pair of pixel points where the maximum value of the first correlation coefficient matrix is obtained.

[0106] For example, the pair of pixel points where the maximum value of the first correlation coefficient matrix is obtained is pixel point m1 of the main image K1 and pixel point m2 of the cropped auxiliary image K2, and 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 an example, the first correlation coefficient matrix can satisfy the following formula:

[0108]

[0109] Where 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 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, according to the overall offset, performing pixel-level registration on the main image and the cropped auxiliary image to obtain the offset of each first corresponding control block.

[0111] For example, a corresponding control block includes two corresponding first main control block and first auxiliary control block, the first main control block is a sub-image of the main image, and the first auxiliary control block is a sub-image of the cropped auxiliary image.

[0112] For example, the first auxiliary control block and the first main control block correspond to each other in the same shooting scene.

[0113] In a possible implementation, the main image can be divided into a plurality of first main control blocks, then a first auxiliary control block slightly larger (for example, 2 or 3 pixels larger than the first main control block) corresponding to the first main control block can be obtained from the cropped auxiliary image according to the overall offset, and then a second correlation coefficient matrix of each group of first corresponding control blocks can be obtained by calculating the correlation coefficient of each group of first main control blocks and the first auxiliary control block.

[0114] For example, the correlation coefficient between the pixel m3 in the first main control block K3 and the pixel m4 in the first auxiliary control block K4 corresponding to the pixel m3 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] For example, the offset of each group of first corresponding control blocks can be saved in a first offset matrix (see FIG. 4) for subsequent calculation. Figure 7 ) in the first offset matrix (see FIG. 4) for subsequent calculation.

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

[0117] For example, the second correlation coefficient matrix can satisfy the following formula:

[0118]

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

[0120] S503, performing interpolation processing on the cropped auxiliary image to obtain an interpolated auxiliary image, and performing sub-pixel level 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 second set of corresponding control blocks includes two second primary control blocks and a second auxiliary control block corresponding to each other. The second primary control block is a sub-image of the primary image, and the second auxiliary control block is a sub-image of the interpolated auxiliary image. The second primary control block and the second auxiliary control block corresponding to each other have the same shooting scene.

[0122] In a possible implementation, the cropped auxiliary image can be interpolated to an integer multiple of the original size. Similarly, the first primary control block can be processed as a second primary control block, and a second auxiliary control block slightly larger than the second primary 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 coefficients of each second set of corresponding control blocks are calculated to obtain a third correlation coefficient matrix of each second set of corresponding control blocks. Finally, the difference between the coordinate values of a pair of pixels with the maximum value of the third correlation coefficient matrix is taken as the offset of the second set of corresponding control blocks.

[0123] In an example, the third correlation coefficient matrix can satisfy the following formula:

[0124]

[0125] wherein γ3(m, n) represents the third correlation coefficient matrix of the second primary control block with the top-left pixel coordinates (m, n), na" and nr" represent the number of rows and columns of pixels of the second primary control block respectively, u"1 is the amplitude matrix of the second primary control block, u"1(m+i", n+j") represents the amplitude of the i" row j" column pixel in the second primary 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" row j" column pixel in the second auxiliary control block with the top-left pixel coordinates (m", n"), and m" = m + Δm' and n" = n + Δn'.

[0126] S504, re-interpolating the slant range of the interpolated auxiliary image according to the offset of the second corresponding control block to obtain the slant range of the interpolated auxiliary image.

[0127] For example, if the offset of the second corresponding control block is Δm" and Δn", a pair of corresponding pixels can be the pixel with the coordinates (m, n) in the primary image and the pixel with the coordinates (m+Δm", n+Δn") in the cropped auxiliary image.

[0128] Figure 8 Fig. 8 shows a structural schematic diagram of a device for measuring sea surface height based on the same-pass multi-angle SAR image according to an example embodiment of the present application. As an example but not limitation, the device 800 can include an image cropping unit 810, a registration unit 820, an initial position determining unit 830, and a sea surface height solving unit 840.

[0129] The image cropping unit 810 is configured to determine position information of a scene center point of each SAR image according to the same-pass SAR images, and crop the auxiliary images to obtain cropped auxiliary images according to the position information of the scene center point, wherein the same-pass SAR images include at least two SAR images having different photographing angles but the same photographing scene including a target point; the registration unit 820 is configured to register the cropped auxiliary images and the main image to obtain an offset between the main image and the cropped auxiliary images, and perform interpolation processing on the cropped auxiliary images according to the offset to obtain interpolated auxiliary images and slant ranges of the interpolated auxiliary images; wherein the main image is one of the same-pass SAR images, and the auxiliary images are the remaining images of the same-pass SAR images; the initial position determining unit 830 is configured to determine initial position information of the target point according to the slant ranges of a pair of corresponding pixels, wherein the pair of corresponding pixels includes a pixel of the main image and a pixel of the interpolated auxiliary image, and the photographing scene of the pair of corresponding pixels is the same; and the sea surface height solving unit 840 is configured to correct the initial position information according to sea surface topographic map prior information to obtain sea surface height information of the target point.

[0130] According to the device provided in the application, the corresponding pixels of the main image and the auxiliary image are obtained by registering the same-pass SAR images, the initial position information of the target point is determined according to the slant ranges of the corresponding pixels, and the sea surface height information is obtained by correcting the initial position information, so that the sea surface height can be estimated using the same-pass SAR images obtained based on the multi-angle along-track interferometry technology while the sea surface flow velocity is estimated using the multi-angle along-track interferometry technology, and the sea surface height is estimated using the remaining information obtained when the flow velocity is estimated, thereby achieving simultaneous estimation of the flow velocity and the sea surface height.

[0131] Figure 9 The system 900 can include a plurality of same-pass satellites 910 (only one is shown) and the device 800.

[0132] The same-pass satellites 910 can be configured to obtain the same-pass SAR images, and the device 800 can be configured to determine the sea surface height information of the target point based on the above measurement method according to the same-pass SAR images.

[0133] According to the system provided in the application, the corresponding pixels of the main image and the auxiliary image are obtained by registering the same-pass SAR images, the initial position information of the target point is determined according to the slant ranges of the corresponding pixels, and the sea surface height information is obtained by correcting the initial position information, so that the sea surface height can be estimated using the same-pass SAR images obtained based on the multi-angle along-track interferometry technology while the sea surface flow velocity is estimated using the multi-angle along-track interferometry technology, and the sea surface height is estimated using the remaining information obtained when the flow velocity is estimated, thereby achieving simultaneous estimation of the flow velocity and the sea surface height.

[0134] Figure 10 A structural schematic diagram of an electronic device provided by an embodiment of the present application is shown. As shown in the figure, Figure 10 The electronic device 1000 shown can include at least one processor 1010 (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 executes the computer program 1030 to implement the steps in any of the method embodiments described above. Figure 10

[0135] The electronic device 1000 can be a processing device such as a robot, which can implement the method described above, and the embodiments of the present application do not limit the specific type of the electronic device.

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

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

[0138] ​The memory 1020 can be an internal storage unit, such as a hard disk or a memory, in some embodiments. The memory 1020 can also be an external storage device, such as a plug-in hard disk, a Smart Memory Card (SMC), a Secure Digital (SD) card, a Flash Card, or the like, in some other embodiments. Further, the memory 1020 can include both an internal storage unit and an external storage device. The memory 1020 is used to store an operating system, application programs, a Boot Loader, data, and other programs, such as program codes of the computer program, and the like. The memory 1020 can also be used to temporarily store data that has been output or is to be output.

[0139] It should be understood that the size of the serial number of each step in the above embodiments does not mean the order of execution, and the execution order of each process should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0140] It can be clearly understood by those skilled in the art that, for the convenience and brevity of description, only the division of the above functional units and modules is taken as an example, and in actual application, the above functions can be completed by different functional units and modules according to needs, that is, the internal structure of the device is divided into different functional units or modules to complete all or part of the functions described above. Each functional unit and module in the embodiment can be integrated in one processing unit, or each unit can exist physically, or two or more units can be integrated in one unit. The integrated unit can be realized in the form of hardware or in the form of software functional unit. In addition, the specific name of each functional unit and module is only for convenient distinction, and does not limit the protection scope of the present application. The specific working process of the unit and module in the above system can refer to the corresponding process in the foregoing method embodiments, which will not be described here.

[0141] The embodiment of the present application further provides a computer readable storage medium, the computer readable storage medium stores a computer program, and the computer program is executed by a processor to realize the steps in each method embodiment.

[0142] The embodiment of the present application provides a computer program product, when the computer program product runs on an electronic device, so that the electronic device executes to realize the steps in each method embodiment.

[0143] The integrated unit, if implemented in the form of a software function unit and sold or used as an independent product, can be stored in a computer readable storage medium. Based on such understanding, the present application can implement all or part of the processes in the above-mentioned embodiment methods, which can be completed by instructing related hardware through a computer program. The computer program can be stored in a computer readable storage medium, and the computer program can implement the steps of each method embodiment when executed by a processor. The computer program includes computer program code, which can be in the form of source code, object code, executable files or some intermediate forms. The computer readable medium can at least include any entity or device capable of carrying the computer program code to the photographing device / terminal equipment, recording medium, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal and software distribution medium. For example, U disk, mobile hard disk, magnetic disk or optical disk, etc. In some jurisdictions, according to legislation and patent practice, the computer readable medium can not be an electrical carrier signal and a telecommunication signal.

[0144] In the above embodiments, the description of each embodiment has its own focus, and the parts not described or recorded in detail in a certain embodiment can be referred to the relevant description of other embodiments.

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

Claims

1. A method for measuring sea surface elevation based on multi-angle SAR images taken in parallel flight, characterized in that: include: determining, based on the co-flying SAR images, position information of a scene center point of each SAR image, and cropping the auxiliary image based on the position information of the scene center point to obtain a cropped auxiliary image, wherein the co-flying SAR images include at least two SAR images whose shooting scenes both include the target point but are shot at different angles; Registering the cropped auxiliary image and the main 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 range of the interpolated auxiliary image; wherein the main image is one of the co-aviation SAR images, and the auxiliary images are the remaining images in the co-aviation SAR images; determining initial position information of the target point according to slant distances of corresponding pixel points, wherein a pair of corresponding pixel points includes a pixel of the primary 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 scene center point to obtain a cropped auxiliary image includes: Determining 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 scene center point of the main image; Determining a 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 range 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, wherein The registering the cropped auxiliary image and the main image to obtain an integral 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 includes: 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 for each group of first corresponding control blocks, wherein a group of 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 an offset of a second corresponding control block, wherein the second corresponding control block includes a pair of mutually corresponding second main control blocks and second auxiliary control blocks, the mutually corresponding second auxiliary control blocks and second main control blocks have the same shooting scene, 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 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, wherein 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 distance of the corresponding pixel points; The initial position information is determined based on the RD equation according to the position information and velocity information of the satellite of the first auxiliary image and the position information and velocity 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 parallel flight, characterized in that: include: an image cropping unit, configured to determine position information of a scene center point of each SAR image based on the same-flight SAR images, and crop the auxiliary image based on 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 are shot at different angles; a registration unit, configured 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 co-aviation SAR images, and the auxiliary images are the remaining images in the co-aviation SAR images; an initial position determination unit, configured to determine initial position information of the target point based on slant distances of corresponding pixels, wherein a pair of corresponding pixels comprises a pixel of the primary image and a pixel of the interpolated auxiliary image, and the same pair of corresponding pixels are captured in the same scene; 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 parallel flight, characterized in that: include: Multiple groups of satellites in co-orbit, the multiple groups of satellites in co-orbit used to acquire co-orbit SAR images, wherein the co-orbit SAR images include at least two SAR images of which both shooting scenes include a target point but are shot at different angles; A sea surface elevation measurement device based on multi-angle SAR images taken in the same flight, wherein the sea surface elevation measurement device based on multi-angle SAR images taken in the same flight is used to determine the sea surface elevation information of a target point based on the multi-angle SAR images taken 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 an electronic device, the method according to any one of claims 1 to 6 is implemented.

Images