An along-track effective baseline estimation method and system for interferometric synthetic aperture radar

Abstract

The application discloses a kind of along-track effective baseline estimation method and system of interferometric synthetic aperture radar, including obtaining the orbit data of main auxiliary satellite in set time period and main auxiliary satellite image, the orbit equation of main auxiliary satellite is obtained using polynomial fitting;The offset between main auxiliary satellite image is calculated, and the starting time of main auxiliary satellite imaging is determined based on the offset, respectively obtain the imaging time of each row in the azimuth direction of main auxiliary satellite image;The relationship function of along-track effective baseline and the row number in the azimuth direction of main auxiliary satellite image is established;Based on the orbit equation of main auxiliary satellite and the imaging time of each row in the azimuth direction of main auxiliary satellite image, the along-track effective baseline of different positions in the azimuth direction is estimated by combining the relationship function.The application solves the problem that the along-track effective baseline cannot be accurately estimated in the prior art, and accurately estimates the along-track effective baseline of different azimuth directions by row, to ensure accurate sea current inversion at different azimuth positions and improve the accuracy of sea current inversion.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of satellite ocean microwave remote sensing, and particularly relates to an along-track effective baseline estimation method and system for interferometric synthetic aperture radar. BACKGROUND

[0002] The statements in this section merely provide background information related to the present application and do not necessarily constitute prior art that is already known to those skilled in the art.

[0003] It is of great significance to study the ocean surface flow field (i.e. the sea current) for naval operations, sea rescue, coastal construction, fishery, ship route planning, ocean environment monitoring and forecasting, etc. In the prior art, satellite remote sensing along-track interferometry is one of the promising technologies applied to target velocity monitoring, which can be applied to the field of ocean, such as observing the ocean surface flow velocity, sea surface wind speed, glacier movement and ship speed, etc. At present, the ocean surface flow field inversion method based on along-track interferometric synthetic aperture radar (ATI-SAR) technology is one of the main methods for studying the sea current. In this method, for an interferometric synthetic aperture radar (InSAR) system, the accurate estimation of the along-track effective baseline plays an important role in InSAR data image registration, flat phase removal, terrain phase calculation, etc., and is also a key parameter for the inversion of high-precision sea surface flow. That is, the accurate estimation of the along-track effective baseline of the interferometric synthetic aperture radar is the basis for the inversion of high-precision sea current.

[0004] The existing ATI-SAR-based sea current inversion method applies the along-track effective baseline value at the center of the azimuth direction (i.e. the satellite flight direction) of the InSAR image to the entire InSAR image. However, in fact, due to the instability of the satellite flight attitude, the along-track effective baseline at different azimuth positions will change greatly. Using the traditional single image center value (i.e. a single fixed value) to invert the sea current will cause a large deviation between the inversion estimate value and the actual observation value, resulting in poor accuracy of the sea current inversion and failing to achieve accurate sea current inversion at different azimuth positions. SUMMARY

[0005] To solve the above problems of the prior art, the present application provides an along-track effective baseline estimation method and system for interferometric synthetic aperture radar, which solves the problem of inaccurate estimation of the along-track effective baseline in the prior art, and ensures accurate sea current inversion at different azimuth positions and improves the accuracy of sea current inversion by accurately estimating the along-track effective baseline of different azimuths of the InSAR data image.

[0006] In a first aspect, the disclosure provides a method for estimating along-track effective baseline of interferometric synthetic aperture radar, comprising:

[0007] Obtaining orbit data of the primary and secondary satellites within a set time period, and obtaining an orbit equation of the primary and secondary satellites by polynomial fitting;

[0008] Obtaining images of the primary and secondary satellites within the set time period, calculating the offset between the images of the primary and secondary satellites, determining the starting time of imaging of the primary and secondary satellites based on the offset, and then obtaining the imaging time of each row in the azimuth direction of the images of the primary and secondary satellites;

[0009] Establishing a relationship function between the along-track effective baseline and the row number in the azimuth direction of the images of the primary and secondary satellites;

[0010] Based on the orbit equation of the primary and secondary satellites and the imaging time of each row in the azimuth direction of the images of the primary and secondary satellites, and in combination with the relationship function, estimating the along-track effective baseline at different positions in the azimuth direction.

[0011] In a further technical solution, the orbit data includes the spatial position and flight speed of the primary and secondary satellites in the WGS-84 coordinate system; and the orbit equation includes the spatial position equation and flight speed equation of the primary and secondary satellites.

[0012] In a further technical solution, the calculation of the offset between the images of the primary and secondary satellites comprises:

[0013] Selecting the scene center of the image of the primary satellite as a control point, and using the coherence coefficient as a matching measure to determine the offset of the image of the secondary satellite.

[0014] In a further technical solution, the offset is divided into a pixel-level offset and a sub-pixel-level offset.

[0015] The method for determining the pixel-level offset comprises:

[0016] Selecting a matching window centered on the control point in the image of the primary satellite, and then selecting a search window with a size larger than the matching window in the image of the secondary satellite, traversing the matching window in the search window, and calculating the corresponding coherence coefficient during the traversal process to determine the traversal position with the maximum coherence coefficient, and taking the offset between the traversal position and the position of the matching window as the pixel offset of the image of the secondary satellite.

[0017] In a further technical solution, the method for determining the sub-pixel-level offset comprises:

[0018] In the main satellite image, a matching window is selected around the control point, and a search window with a size larger than the matching window is selected in the auxiliary satellite image. After oversampling the matching window and the search window, interpolation processing is performed by using a sinc function interpolation method. Then, the matching window is traversed in the search window, and the corresponding coherence coefficients are calculated during the traversal process. The traversal position with the maximum coherence coefficient is determined, and the offset of the traversal position and the matching window position is taken as the sub-pixel level offset of the auxiliary satellite image.

[0019] In a further technical solution, the imaging time of the main auxiliary satellite image in the azimuth direction of the nth row is:

[0020]

[0021] Where PRF is the pulse repetition frequency, and t0 is the imaging start time, including the main satellite imaging start time and the auxiliary satellite imaging start time.

[0022] In a further technical solution, for the single-launch double-reception mode, the along-track effective baseline B e The relationship function with the imaging row number is:

[0023]

[0024] In the formula, t m and t s are the imaging times of the main satellite and the auxiliary satellite on the same target point; X m , Y m , and Z m represent the positions of the main satellite in the x, y, and z directions, respectively; V mx , V my , and V mz represent the flight speeds of the main satellite in the x, y, and z directions, respectively; X s , Y s , and Z s represent the positions of the auxiliary satellite in the x, y, and z directions, respectively.

[0025] In a second aspect, the disclosure provides an along-track effective baseline estimation system for interferometric synthetic aperture radar, comprising:

[0026] A data acquisition module is configured to acquire orbit data of the main and auxiliary satellites within a set time period and main and auxiliary satellite images

[0027] The data processing module is configured to obtain an orbit equation of the primary satellite and the auxiliary satellite by polynomial fitting according to orbit data of the primary satellite and the auxiliary satellite within a set time period; calculate an offset between images of the primary satellite and the auxiliary satellite within the set time period, and determine a starting time of imaging of the primary satellite and the auxiliary satellite based on the offset, and then obtain imaging times of each row in the azimuth direction of the images of the primary satellite and the auxiliary satellite.

[0028] The relationship function building module is configured to build a relationship function between the along-track effective baseline and the row number in the azimuth direction of the images of the primary satellite and the auxiliary satellite.

[0029] The along-track effective baseline estimation module is configured to estimate the along-track effective baseline at different positions in the azimuth direction based on the orbit equation of the primary satellite and the auxiliary satellite and the imaging times of each row in the azimuth direction of the images of the primary satellite and the auxiliary satellite, and in combination with the relationship function.

[0030] In a third aspect, the present disclosure further provides an electronic device, including a memory and a processor, and computer instructions stored in the memory and running on the processor, when the computer instructions are run by the processor, the steps of the method of the first aspect are completed.

[0031] In a fourth aspect, the present disclosure further provides a computer readable storage medium for storing computer instructions, when the computer instructions are executed by a processor, the steps of the method of the first aspect are completed.

[0032] The above one or more technical solutions have the following beneficial effects:

[0033] 1. The present application provides an along-track effective baseline estimation method and system for interferometric synthetic aperture radar, which solves the problem of inaccurate estimation of the along-track effective baseline in the prior art, and ensures accurate sea current inversion at different positions in the azimuth direction by accurately estimating the along-track effective baseline of each row in the azimuth direction of InSAR data images, thereby improving the accuracy of sea current inversion.

[0034] 2. The present application establishes a functional relationship between the along-track effective baseline value and the row number in the azimuth direction on the basis of satellite orbit fitting, and then obtains the along-track effective baseline length of each row in the azimuth direction, thereby realizing the fine use of InSAR data images in the along-track effective baseline aspect and effectively improving the accuracy of sea current inversion based on ATI. BRIEF DESCRIPTION OF DRAWINGS

[0035] The drawings accompanying the specification of the present application form a part of the present application and serve to provide a further understanding of the present application, the illustrative embodiments of the present application and their descriptions serve to explain the present application, and do not constitute an improper limitation on the present application.

[0036] Figure 1 The method described in Embodiment One of the present application is shown in the overall flowchart;

[0037] Figure 2 FIG. 1 is a schematic diagram of the flight orbits of the primary and secondary satellites in Embodiment One of the present application;

[0038] Figure 3 FIG. 2 is a geometric schematic diagram of the along-track effective baseline in Embodiment One of the present application;

[0039] Figure 4 FIG. 3 is a diagram of the along-track effective baseline and the azimuth row number in Example One in Embodiment One of the present application;

[0040] Figure 5 FIG. 4 is a diagram of the along-track effective baseline and the azimuth row number in Example Two in Embodiment One of the present application;

[0041] Figure 6 FIG. 5 is a diagram of the difference between the results of the two algorithms for flow velocity inversion in Example One in Embodiment One of the present application. DETAILED DESCRIPTION

[0042] It should be noted that the following detailed description is exemplary in nature and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0043] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0044] Embodiment One

[0045] To solve the problems in the background art, the present embodiment provides an along-track effective baseline estimation method for interferometric synthetic aperture radar. On the basis of fitting the satellite orbit, a relationship function between the along-track effective baseline and the azimuth row number is established, and then the along-track effective baseline length of each row in the azimuth direction is obtained. This realizes the fine application of InSAR images in along-track effective baseline estimation and improves the accuracy of sea current inversion based on along-track interferometric synthetic aperture radar (ATI-SAR) technology.

[0046] The along-track effective baseline estimation method described in the present embodiment, as shown in FIG. 1, specifically includes the following steps: Figure 1

[0047] Step S1, obtaining the orbit data of the primary and secondary satellites in a set time period, and using polynomial fitting to obtain the orbit equation of the primary and secondary satellites;

[0048] ​Step S2: Acquire primary and secondary satellite images within a set time period, calculate the offset between the primary and secondary satellite images, determine the start time of primary and secondary satellite imaging based on the offset, and then obtain the imaging time of each row of the primary and secondary satellite images in the azimuth direction.

[0049] Step S3: Establish the relationship function between the effective baseline and the azimuth up-row number of the primary and secondary satellite images;

[0050] Step S4: Based on the orbit equations of the primary and secondary satellites and the imaging times of each row in the azimuth of the primary and secondary satellite images, and in conjunction with the aforementioned relationship function, estimate the effective baselines for orbital alignment at different positions in the azimuth direction.

[0051] In step S1 above, if Figure 2 As shown, A and B represent the orbits of the primary and secondary satellites, respectively. During the operation of the primary and secondary satellites, orbital data of the satellites in their respective orbits within a certain time period is acquired. Typically, each satellite can provide orbital parameters at 1-second intervals, including its spatial position and velocity in the WGS-84 coordinate system. For example, P m Let P be a point on orbit A. The main satellite moves to point P on orbit A. m When a point is defined, its spatial rectangular coordinates are (X... m Y m Z m The flight speed on the three coordinate axes is (V) xm V ym V zm ); P s For a point on orbit B, the auxiliary satellite moves to point P on orbit B. s When a point is defined, its spatial rectangular coordinates are (X... s Y s Z s The flight speed on the three coordinate axes is (V) xs V ys V zs Using time as the independent variable, a cubic polynomial is used to fit the orbital data of the primary and secondary satellites within a set time period to obtain the orbital equations of the primary and secondary satellites. These orbital equations include the spatial position equation and the flight velocity equation.

[0052] The spatial position equation is as follows:

[0053]

[0054] The equation for flight speed is:

[0055]

[0056] In the above formula, (X, Y, Z) and (V) x V y Vz ) represents the position of the satellite and the flight velocity in the three coordinate axis directions x, y, z, a i , b i , c i , d i , e i , f i are polynomial coefficients which are constants, wherein i = 0, 1, 2, 3.

[0057] In the step S2, since the primary and secondary satellites have the orbit equations (1) and (2) respectively, and the primary and secondary satellite images obtained by the primary and secondary satellites can have the same row of pixels corresponding to different ground imaging points, when the orbit equation of the secondary satellite is used, the row numbers of the secondary satellite image and the primary satellite image need to be registered first to determine the correspondence between the different row numbers of the secondary satellite image and the primary satellite image corresponding to the same ground imaging point.

[0058] In this embodiment, in order to solve the problem that the ground imaging points corresponding to the row numbers of the primary and secondary satellite images are not unified, the offset between the primary and secondary satellite images is determined first. Specifically, the scene center of the primary satellite image is selected as the control point, and the coherence coefficient is used as the matching measure to determine the offset of the secondary satellite image. The calculation formula of the coherence coefficient is as follows:

[0059]

[0060] In the formula, M and N are the size of the image block for calculating the coherence; n' and m' are the row and column numbers of the random pixels in the image block; μ1(n', m') and μ2(n', m') are the complex values of the random pixels at the coordinates (n', m') in the primary and secondary image blocks; |·| 2 is the second norm of the data; * represents conjugate.

[0061] In the above method for determining the offset using the correlation coefficient, the determined offset is divided into a pixel-level offset and a sub-pixel-level offset.

[0062] The method for determining the pixel-level offset is as follows: a matching window is selected in the primary satellite image with the control point as the center, and a search window with a size larger than the matching window is selected in the secondary satellite image, the matching window is traversed in the search window, and the corresponding coherence coefficients are calculated in the traversal process to determine the traversal position with the maximum coherence coefficient, and the offset between the traversal position and the position of the matching window is taken as the pixel offset of the secondary satellite image, that is, the difference between the center pixel positions, so as to determine the number of row numbers to be adjusted for the secondary satellite image.

[0063] Further, considering that the InSAR imaging interval is in the order of milliseconds, during which the random motion of the sea surface causes the sea wave texture recorded by the rear antenna to have changed to a certain extent compared with the sea wave texture recorded by the front antenna, the correlation of the sea wave texture between images will sharply decrease, thus when the correlation coefficient method is used to obtain the offset between the primary and secondary satellite images, the area contained in the selected matching window should contain land area to reduce the error of the offset calculation.

[0064] In order to further improve the calculation accuracy of the along-track effective baseline, the sub-pixel level offset can also be further calculated. The method for determining the sub-pixel level offset is as follows: a matching window is selected in the primary satellite image with the control point as the center, and a search window with a size larger than the matching window is selected in the secondary satellite image; the matching window and the search window are respectively oversampled, and interpolation processing is performed by using the sinc function interpolation method, and the interpolation interval is set to 0.1 pixel. After the SAR image is interpolated, the offset calculation accuracy can reach 0.1 pixel. If no interpolation is performed, the accuracy is only 1 pixel. Therefore, in order to further improve the inversion accuracy, the image offset is further calculated by interpolation in the present embodiment. Finally, the sub-pixel level offset is determined by using the same traversal method as above. At this time, the row number of the unified primary and secondary satellite images becomes decimal.

[0065] In the present embodiment, if the offset is positive, it means that the imaging time of a certain point in the secondary satellite image is earlier than that of the same point in the primary satellite image. If the offset is negative, it is the opposite.

[0066] Preferably, in the process of calculating the offset, a plurality of matching windows (i.e. image blocks) containing land area are selected, the corresponding offsets are respectively calculated, a plurality of offsets are obtained, the average offset is obtained by averaging the plurality of offsets, and the calculation accuracy is further ensured.

[0067] On the basis of obtaining the offset, the starting time of the primary and secondary satellite imaging is determined according to the offset. For example, the starting time of the primary satellite imaging is set to t m0 , i.e. the imaging time of the first row of the primary satellite image. The starting time of the secondary satellite imaging is t s0 , i.e. the imaging time of the first row of the primary satellite image after registration. Usually, the obtained offset is the number of rows of offset (such as 0.12 rows). On the basis of the known PRF, the imaging time of each row is 1 / PRF, and the offset time is the product of the offset and 1 / PRF. Thus, the starting time of the secondary satellite imaging is the sum of the starting time of the primary satellite imaging and the offset time.

[0068] On the basis of the above-mentioned offset, the imaging time of each row of the primary and secondary satellite images in the azimuth direction is obtained. Specifically, the imaging time of the nth row in the azimuth direction of the InSAR image is:

[0069]

[0070] Wherein, PRF is the pulse repetition frequency, t0 is the imaging starting time, including the main satellite imaging starting time and the auxiliary satellite imaging starting time.

[0071] In the above step S3, the relationship function between the along-track effective baseline and the image azimuth of the main and auxiliary satellites is established. The geometric schematic of the along-track effective baseline is shown in Figure 3 Wherein, S1 is the instantaneous position of the main satellite when imaging the point P, S2 is the instantaneous position of the auxiliary satellite when imaging the point P, and the vector formed by S1 and S2 is the interference baseline The velocity vector of the main satellite is Then the baseline vector is The projection in the direction of the velocity vector of the main satellite is the along-track physical baseline B V , which is:

[0072]

[0073] And for the single-transmit dual-receive mode, that is, only one antenna is used for transmission, and two antennas are used for reception, the along-track effective baseline B e is half of the along-track physical baseline B V .

[0074] Due to the instability of the satellite attitude, the along-track effective baseline of the same interferometric image data is a variable that changes with the azimuth of the uplink number, therefore, the relationship function between the along-track effective baseline and the image azimuth of the main and auxiliary satellites is established, so as to obtain the along-track effective baseline value of each row in the satellite image.

[0075] Through the above formula (1), (2), (5), the function relationship between the along-track effective baseline B e of the single-transmit dual-receive mode and the imaging row number is derived as:

[0076]

[0077] In the formula, t m and t s are the imaging times of the main satellite and the auxiliary satellite on the same target point, that is:

[0078] t m = [(n-1) / PRF] + t m0 (7)

[0079] t s = [(n-1) / PRF] + t s0 (8)

[0080] Wherein, t m0is the imaging time of the first row of the primary satellite image s0 is the imaging time of the first row of the primary satellite image after registration of the secondary satellite image and the primary satellite image.

[0081] Finally, in step S4, the orbit equation of the primary satellite and the imaging time of each row in the azimuth direction of the primary satellite image and the secondary satellite image are substituted into the relationship function to estimate the along-track effective baseline at different positions in the azimuth direction. That is, according to the orbit equation of the primary satellite, the spatial position and flight speed of the imaging time corresponding to the current row of the primary satellite image are obtained; according to the orbit equation of the secondary satellite, the spatial position and flight speed of the imaging time corresponding to the current row of the secondary satellite image after registration of the secondary satellite image and the primary satellite image are obtained; and the above relationship function is substituted to obtain the along-track effective baseline of the current row, that is, the along-track effective baseline of the position in the azimuth direction corresponding to the current row.

[0082] The above scheme of the embodiment is further described through the following examples.

[0083] In Example 1, taking the primary satellite and the secondary satellite of TanDEM-X / TerraSAR-X as an example, the orbit data of the primary satellite and the secondary satellite at the time of 6:41 on March 19, 2012 and the location of the Oniket group region are obtained, and the primary satellite image and the secondary satellite image are obtained, wherein the size of the primary satellite image is 20782x18432, that is, the row number is from 1 to 20782, the data in the time period of 6:41:15-6:41:32 is selected, the spatial position equation and the flight speed equation of the primary satellite are fitted by using a cubic polynomial, which are formula (9) and formula (10) respectively:

[0084]

[0085]

[0086] Similarly, the spatial position equation of the secondary satellite is fitted by using a cubic polynomial, which is formula (11):

[0087]

[0088] Then, the average offset of the primary satellite image and the secondary satellite image in the azimuth direction is obtained by using the coherence coefficient method, and the calculation is 0.141 rows. At this time, midnight zero time is set as 0s, the starting time of the primary satellite imaging is obtained by reading the satellite header file as 24079.843000s, and the PRF is also obtained by reading the satellite header file as 3356.74Hz, that is, the imaging time of each row is 1 / PRF. Through conversion, the starting time of the secondary satellite imaging is obtained as 24079.842957s.

[0089] The line number 1-20782 is passed through formula (3) to obtain the respective time of the main and auxiliary satellite imaging corresponding to the line; then the instantaneous position of the main and auxiliary satellites and the instantaneous velocity of the main satellite are obtained through the orbit equations (9), (10), (11); the obtained data is substituted into formula (10), and the along-track effective baseline B of the main satellite image (or the auxiliary satellite image) corresponding to each line can be obtained e , and the results are shown in Figure 4 .

[0090] As another example, in example two, the same TanDEM-X / TerraSAR-X main and auxiliary satellite data is taken as an example, and another pair of along-track interferometric data is obtained, that is, the main and auxiliary satellite orbit data and the main and auxiliary satellite images at 6:51 on September 1, 2014, near the Isle of Arran in southwest Scotland, wherein the size of the main satellite image is 28200x12790.

[0091] The relationship between the along-track effective baseline obtained by the same method above and the line number of the main satellite image in the azimuth direction is shown in Figure 5 .

[0092] In addition, in specific applications, the fitted linear equation can also be used to replace the cumbersome calculation of formula (6). In combination with Figure 4 , the linear equation fitting of the along-track effective baseline and the line number in example one above is formula (12), that is:

[0093] B e = 41.6857 + 9.1847x10 -5 n (12)

[0094] The radar radial current of the region is inverted using the azimuth direction row-by-row along-track effective baseline obtained by the above method, and the inversion result is compared with the result of inverting the sea current using the traditional InSAR single image center value. The difference between the radar radial current inverted by the two is shown in Figure 6 . From Figure 6 , it can be seen that in the comparative analysis from line 1 to line 20782, the radial current value inverted by the row-by-row obtained along-track effective baseline gradually decreases as the line number increases. At the 10000th line position, the radial current values obtained by the two are basically close, but as the line number decreases or increases, the difference between the radial current values inverted by the two gradually increases, and the maximum can be ±3cm / s.

[0095] This also further illustrates that the along-track effective baseline at different azimuth positions will have greater changes, thereby affecting the final inversion result, and the use of the traditional single image center value to invert the sea current will cause a large deviation between the inversion estimated value and the actual observation value, and the embodiment ensures the accurate sea current inversion at different azimuth positions by accurately estimating the along-track effective baseline of each row in different azimuths of the InSAR data image, and improves the accuracy of the sea current inversion.

[0096] Embodiment two

[0097] The embodiment provides an along-track effective baseline estimation system of interferometric synthetic aperture radar, comprising:

[0098] The data acquisition module is configured to acquire orbit data of the primary and secondary satellites within a set time period and primary and secondary satellite images

[0099] The data processing module is configured to obtain an orbit equation of the primary and secondary satellites by polynomial fitting according to the orbit data of the primary and secondary satellites within the set time period, calculate the offset between the primary and secondary satellite images within the set time period, determine the starting time of imaging of the primary and secondary satellites based on the offset, and then obtain the imaging time of each row in the azimuth direction of the primary and secondary satellite images, respectively.

[0100] The relationship function building module is configured to build a relationship function of the along-track effective baseline and the row number in the azimuth direction of the primary and secondary satellite images.

[0101] The along-track effective baseline estimation module is configured to estimate the along-track effective baseline at different positions in the azimuth direction based on the orbit equation of the primary and secondary satellites and the imaging time of each row in the azimuth direction of the primary and secondary satellite images in combination with the relationship function.

[0102] Embodiment three

[0103] The embodiment provides an electronic device, comprising a memory and a processor, and computer instructions stored in the memory and running on the processor, when the computer instructions are run by the processor, the steps in the along-track effective baseline estimation method of the interferometric synthetic aperture radar are completed.

[0104] Embodiment four

[0105] The embodiment also provides a computer readable storage medium for storing computer instructions, when the computer instructions are executed by the processor, the steps in the along-track effective baseline estimation method of the interferometric synthetic aperture radar are completed.

[0106] The steps and methods involved in the above embodiments two to four correspond to the method embodiment one, and the specific implementation can refer to the relevant description part of embodiment one. The term "computer readable storage medium" should be understood as including a single medium or multiple media of one or more instruction sets; it should also be understood as including any medium capable of storing, encoding or carrying instruction sets for execution by a processor and causing the processor to perform any of the methods in the present application.

[0107] Those skilled in the art should understand that each module or step of the present application described above can be realized by a general computer device, alternatively, they can be realized by program codes executable by a computing device, so that they can be stored in a storage device for execution by a computing device, or they can be respectively manufactured into each integrated circuit module, or a plurality of modules or steps among them can be manufactured into a single integrated circuit module to realize. The present application is not limited to any specific combination of hardware and software.

[0108] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

[0109] The above describes the specific embodiments of the present application in combination with the accompanying drawings, but is not intended to limit the protection scope of the present application. Those skilled in the art should understand that various modifications or changes made by those skilled in the art on the basis of the technical solutions of the present application without creative labor are still within the protection scope of the present application.

Claims

1. A method for estimating the effective baseline along the trajectory of an interferometric synthetic aperture radar, characterized in that, include: The orbital data of the primary and secondary satellites within a set time period are obtained, and the orbital equations of the primary and secondary satellites are obtained by polynomial fitting. Acquire primary and secondary satellite images within a set time period, calculate the offset between the primary and secondary satellite images, determine the start time of primary and secondary satellite imaging based on the offset, and then obtain the imaging time of each row of the primary and secondary satellite images in the azimuth direction. Establish a relationship function between the effective baseline and the azimuth up-row number of the primary and secondary satellite images; Based on the orbit equations of the primary and secondary satellites and the imaging times of each row in the azimuth of the primary and secondary satellite images, combined with the aforementioned relationship function, the effective baselines for orbital alignment at different positions in the azimuth direction are estimated. Among them, the effective baseline for single-transmitter dual-receiver mode is as follows. The relationship function between the image row number and the image row number is: ； In the formula, and These are the times when the main satellite and the auxiliary satellite image the same target point, respectively. X m , Y m , Z m These represent the main satellite in the three coordinate axes. x , y , z The position above, V mx , V my , V mz These represent the main satellite in the three coordinate axes. x , y , z Flight speed on X s , Y s , Z s These represent the auxiliary satellite in the three coordinate axes. x , y , z The position above.

2. The method for estimating the effective baseline of interferometric synthetic aperture radar as described in claim 1, characterized in that, The orbital data includes the spatial position and flight velocity of the primary and secondary satellites in the WGS-84 coordinate system; the orbital equations include the spatial position equations and flight velocity equations of the primary and secondary satellites.

3. The method for estimating the effective baseline of interferometric synthetic aperture radar as described in claim 1, characterized in that, The calculation of the offset between the primary and secondary satellite images includes: The scene center of the main satellite image is selected as the control point, and the offset of the secondary satellite image is determined using the coherence coefficient as the matching measure.

4. The method for estimating the effective baseline of interferometric synthetic aperture radar as described in claim 3, characterized in that, The offset is divided into pixel-level offset and sub-pixel-level offset; Methods for determining cell-level offsets include: In the main satellite image, a matching window is selected with the control point as the center. Then, in the secondary satellite image, a search window larger than the matching window is selected. The matching window is traversed in the search window. During the traversal, the corresponding coherence coefficient is calculated. The traversal position with the largest coherence coefficient is determined. The offset between the traversal position and the matching window position is used as the pixel offset of the secondary satellite image.

5. The method for estimating the effective baseline of interferometric synthetic aperture radar as described in claim 4, characterized in that, Methods for determining sub-cell level offsets include: In the main satellite image, a matching window is selected centered on the control point. In the secondary satellite image, a search window larger than the matching window is selected. After oversampling the matching window and the search window respectively, the sinc function is used for interpolation. Then, the matching window is traversed in the search window. During the traversal, the corresponding coherence coefficient is calculated. The traversal position with the largest coherence coefficient is determined. The offset between the traversal position and the matching window position is used as the sub-pixel offset of the secondary satellite image.

6. The method for estimating the effective baseline of interferometric synthetic aperture radar as described in claim 1, characterized in that, The azimuth direction of the primary and secondary satellite images n The imaging time of the line is: ； in, PRF The pulse repetition frequency, t 0 represents the imaging start time, including the main satellite imaging start time and the auxiliary satellite imaging start time.

7. A system for estimating the effective baseline along the trajectory of an interferometric synthetic aperture radar, characterized in that, include: The data acquisition module is used to acquire orbital data and images of the primary and secondary satellites within a set time period; The data processing module is used to obtain the orbit equations of the primary and secondary satellites by using polynomial fitting based on the orbit data of the primary and secondary satellites within a set time period; calculate the offset between the primary and secondary satellite images based on the primary and secondary satellite images within the set time period; determine the start time of the imaging of the primary and secondary satellites based on the offset; and then obtain the imaging time of each row of the primary and secondary satellite images in the azimuth direction. The relation function building module is used to establish the relation function between the effective baseline and the azimuth up-row number of the primary and secondary satellite images; The effective baseline estimation module is used to estimate the effective baseline at different positions in the azimuth direction based on the orbit equations of the primary and secondary satellites and the imaging time of each row in the azimuth of the primary and secondary satellite images, combined with the relationship function. Among them, the effective baseline for single-transmitter dual-receiver mode is as follows. The relationship function between the image row number and the image row number is: ； In the formula, and These are the times when the main satellite and the auxiliary satellite image the same target point, respectively. X m , Y m , Z m These represent the main satellite in the three coordinate axes. x , y , z The position above, V mx , V my , V mz These represent the main satellite in the three coordinate axes. x , y , z Flight speed on X s , Y s , Z s These represent the auxiliary satellite in the three coordinate axes. x , y , z The position above.

8. An electronic device, characterized in that, It includes a memory and a processor, as well as computer instructions stored in the memory and running on the processor, which, when executed by the processor, complete the steps of the on-track effective baseline estimation method for interferometric synthetic aperture radar as described in any one of claims 1-6.

9. A computer-readable storage medium, characterized in that, Used to store computer instructions, which, when executed by a processor, complete the steps of the on-track effective baseline estimation method for interferometric synthetic aperture radar as described in any one of claims 1-6.

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