Reconstruction method and device of airborne multi-pass insar image

Abstract

The application discloses a reconstruction method and device of airborne multi-pass InSAR images, and belongs to the technical field of synthetic aperture radar interferometry. The method comprises the following steps: acquiring main image data and auxiliary image data of airborne multi-pass InSAR; calculating a ground view direction of the main image, setting the ground view direction of the auxiliary image to be consistent with that of the main image, and inversely calculating a reconstructed Doppler frequency of the auxiliary image; calculating a range resolution of the main image, setting the range resolution of the auxiliary image to be consistent with that of the main image, and inversely calculating a range resolution of the auxiliary image; setting a range resolution of the reconstructed auxiliary image to be consistent with that of the main image; generating a parameter file of the reconstructed auxiliary image, establishing a positioning relationship between the auxiliary image and the reconstructed auxiliary image, resampling the auxiliary image, and obtaining the reconstructed auxiliary image. The application solves the problems of inconsistent spatial directions and unmatched spatial scales, thereby realizing spatial alignment of the main image and the auxiliary image, and significantly improving the interference registration precision.

Description

TECHNICAL FIELD

[0001] The application relates to a reconstruction method and device for airborne multi-pass InSAR images, and belongs to the technical field of InSAR (Interferometric Synthetic Aperture Radar). BACKGROUND

[0002] SAR (Synthetic Aperture Radar) is an active imaging sensor, which can be used for observation of the earth at all times and in all weather conditions without being limited by natural conditions such as illumination and weather, and has a wide range of applications in many fields such as topographic mapping, natural resource surveying and monitoring, disaster emergency, and military reconnaissance. InSAR (Interferometric SAR) technology is an extension of SAR technology, which utilizes the mathematical relationship between interference phase and terrain elevation, and is an important remote sensing technology for measuring three-dimensional information of the earth surface, especially ground deformation.

[0003] Airborne multi-pass InSAR is an observation mode for interferometric measurement by performing multiple airborne SAR repeated flights over the same area. For long-wave SAR, it can break through the baseline length limitation of the airborne dual / multi-antenna InSAR system and measure three-dimensional information of the earth surface; and it can also effectively realize ground deformation measurement through multiple flights for differential interference.

[0004] Interference registration is a key step in InSAR processing, and good interference registration is required for high-precision inversion of three-dimensional information of the earth surface. Interference registration is performed on the main image and the auxiliary image of interference, and the image matching method is used to find the accurate same pixel points of the interference image pair, so that a pair of pixels in the two registered images correspond to the same area on the ground, and the image signals are coherent. The interference image matching generally adopts a window-based correlation function matching method, which requires the main image and the auxiliary image to be consistent in spatial scale and direction, otherwise the matching may fail or the precision is poor, and an effective interference image cannot be formed, resulting in failure of three-dimensional inversion. Due to the multiple repeated flights of airborne multi-pass InSAR, the flight lines cannot be strictly parallel due to factors such as aircraft flight control and air flow, and the main image and the auxiliary image are inconsistent in spatial direction due to the use of different Doppler center frequencies in each flight imaging. The difference in flight speed and the difference in sampling frequency used in imaging result in inconsistency in spatial scale of the main image and the auxiliary image, which makes it difficult to obtain ideal results by directly performing interference registration on the airborne multi-pass InSAR data. Therefore, the airborne multi-pass InSAR image needs to be reconstructed to make the main image and the auxiliary image consistent in spatial scale and direction, so as to realize high-precision interference registration and high-quality interference three-dimensional inversion. SUMMARY

[0005] In order to solve the above problems, the application provides a reconstruction method and device for airborne multi-pass InSAR images, which can realize spatial alignment of main and auxiliary images and improve interference registration accuracy.

[0006] The application adopts the technical scheme of:

[0007] In a first aspect, the application provides a reconstruction method for airborne multi-pass InSAR images, which includes the following steps:

[0008] Step S1: obtaining main image data and auxiliary image data of airborne multi-pass InSAR;

[0009] Step S2: calculating a ground line-of-sight direction of the main image according to imaging parameters of the main image, setting the ground line-of-sight direction of the auxiliary image to be consistent with the ground line-of-sight direction of the main image, and inversely calculating a Doppler frequency of the reconstructed auxiliary image based on the ground line-of-sight direction;

[0010] Step S3: calculating a range direction pixel resolution of the main image according to a range direction time resolution and a flight speed of the main image, setting the range direction pixel resolution of the auxiliary image to be consistent with the range direction pixel resolution of the main image, and inversely calculating a range direction time resolution of the reconstructed auxiliary image based on the range direction pixel resolution and a flight speed of the auxiliary image platform;

[0011] Step S4: setting the range direction pixel resolution of the reconstructed auxiliary image to be consistent with the range direction pixel resolution of the main image;

[0012] Step S5: generating a reconstructed auxiliary image parameter file, establishing a positioning relationship between the auxiliary image and the reconstructed auxiliary image, resampling the auxiliary image, and obtaining the reconstructed auxiliary image.

[0013] As a possible implementation manner of the embodiment, the step S2 includes the following steps:

[0014] Step S21: selecting a center point of the main image, obtaining an image coordinate of the center point, determining a corresponding platform flight speed according to a range direction image coordinate, and calculating an oblique viewing angle of the main image;

[0015] Step S22: calculating a slant range according to a range direction image coordinate, calculating a projection length of the slant range in a normal side direction, a ground distance, a normal side direction projection ground distance, and a ground projection oblique viewing angle, and determining a ground line-of-sight direction of the main image in combination with a heading azimuth of the main image, which is used to accurately obtain a direction reference of a ground observed by the main image;

[0016] Step S23: using a range-Doppler (R-D) model to calculate a geographic coordinate from the image coordinate of the center point of the main image in combination with a local average elevation, and then calculating an image coordinate of a corresponding auxiliary image point according to the geographic coordinate, which is used to establish a correlation between the main image and the auxiliary image in the geographic coordinate;

[0017] Step S24, set the auxiliary image ground view direction consistent with the main image ground view direction, calculate the ground projection angle of view according to the auxiliary image heading azimuth, combine the auxiliary image platform flight speed, slant range and flight height, and back-calculate the reconstructed auxiliary image Doppler frequency, so as to ensure that the auxiliary image and the main image are consistent in the ground view direction, and lay a foundation for subsequent spatial alignment.

[0018] As a possible implementation manner of the embodiment, the step S3 comprises the following steps:

[0019] Step S31, calculate the main image azimuth pixel resolution by using the main image platform flight speed, and determine the spatial scale of the main image in the azimuth direction;

[0020] Step S32, set the auxiliary image azimuth pixel resolution and the main image azimuth time resolution consistent, and back-calculate the reconstructed auxiliary image azimuth time resolution by using the auxiliary image platform flight speed.

[0021] As a possible implementation manner of the embodiment, the step S5 comprises the following steps:

[0022] Step S51, modify the auxiliary image parameter file, update the Doppler frequency to the reconstructed frequency, the azimuth time resolution to the reconstructed time resolution, and the range pixel resolution to the set resolution, generate the reconstructed auxiliary image parameter file, and provide accurate parameter basis for subsequent resampling;

[0023] Step S52, establish a geometric positioning model of the auxiliary image and the reconstructed auxiliary image based on the imaging parameters, and determine the spatial mapping relationship therebetween;

[0024] Step S53, initialize the reconstructed auxiliary image according to the auxiliary image size, realize the mapping from the reconstructed auxiliary image coordinates to the auxiliary image coordinates through the positioning model pixel by pixel, obtain the pixel value by using the interpolation algorithm, complete the resampling, and finally obtain the reconstructed auxiliary image which is spatially aligned with the main image.

[0025] As a possible implementation manner of the embodiment, the step S2 comprises the following steps:

[0026] Step S21, select the main image center point, obtain the image coordinates , determine the corresponding platform flight speed according to the azimuth image coordinates , calculate the main image angle of view , wherein, is the main image Doppler frequency, is the radar wavelength;

[0027] Step S22, obtain the slant range according to the range image coordinates ​ Calculate the projected length of the slant range in the frontal side view direction. Distance Projected distance from the ground in the front and side view directions and oblique angle of ground projection , Main image altitude, combined with main image heading and azimuth Determine the ground line of sight direction of the main image. The purpose of this step is to accurately obtain the orientation reference of the ground observed in the main image;

[0028] Step S23: Based on the SAR image geometric positioning model, determine the coordinates of the main image center point. The standard is combined with the local average elevation. Calculate geographic coordinates Then based on the geographical coordinates Calculate the image coordinates of the corresponding auxiliary image points Its function is to establish the correlation between the primary and secondary images in geographic coordinates. The SAR image geometric positioning model adopts the range-Doppler (RD) model:

[0029] ,

[0030] in, The observation equation is for range imaging conditions. The observation equation for Doppler imaging conditions, Geographic coordinates Image coordinates;

[0031] Step S24, set the ground view direction of the auxiliary image to be consistent with the ground view direction of the main image. According to the auxiliary image heading and azimuth angle Calculate its ground projection oblique angle Combined with the flight speed of the auxiliary imaging platform Slope distance and flight altitude Inversely calculate the Doppler frequency of the reconstructed auxiliary image. Among them, the auxiliary image oblique angle The projected length of the slant distance in the frontal side view direction Projected distance from the ground in the frontal and lateral viewing directions auxiliary image point distance This ensures that the auxiliary image and the main image are aligned in the direction of the ground line of sight, laying the foundation for subsequent spatial alignment.

[0032] As one possible implementation of this embodiment, step S3 specifically includes the following steps:

[0033] Calculate the azimuth pixel resolution of the main image: ,in Flight speed of the main imaging platform As the temporal resolution of the main image in the azimuth direction, this calculation can clearly define the spatial scale of the main image in the azimuth direction;

[0034] If the azimuth pixel resolution of the auxiliary image is set to be the same as the azimuth temporal resolution of the primary image, then the azimuth pixel resolution of the auxiliary image will be: Inversely calculate the azimuth temporal resolution of the reconstructed auxiliary image. , To aid in the flight speed of the imaging platform.

[0035] As one possible implementation of this embodiment, step S4 specifically involves setting the range pixel resolution of the reconstructed auxiliary image. Distance pixel resolution relative to the main image Consistency, that is Its function is to ensure that the primary and secondary images maintain consistency in the spatial scale of the distance direction.

[0036] As one possible implementation of this embodiment, step S5 specifically includes:

[0037] Doppler frequency from auxiliary image parameter file Azimuth time resolution and distance pixel resolution Modified to the reconstructed Doppler frequency Azimuth time resolution and distance pixel resolution Generate the reconstructed auxiliary image parameter file;

[0038] Geometric positioning models for auxiliary and reconstructed auxiliary images are established based on imaging parameters;

[0039] A reconstructed auxiliary image is created based on the size of the auxiliary image; then the image coordinates of the reconstructed auxiliary image points are used. Starting point, combined with local average elevation Calculate geographic coordinates based on the geometric positioning model Then, based on geographical coordinates and local average elevation Calculate the image coordinates of the corresponding auxiliary image points based on the geometric positioning model. According to image coordinates Pixel values ​​are obtained by interpolation sampling on the secondary image and then filled into the reconstructed secondary image. Image point location; thus, pixel-by-pixel localization and resampling processing is performed on the reconstructed auxiliary image to obtain the final reconstructed auxiliary image.

[0040] Secondly, an embodiment of the present invention provides a reconstruction apparatus for airborne multi-flight InSAR images, comprising:

[0041] a data acquisition module configured to acquire main image data and auxiliary image data of airborne multi-pass InSAR;

[0042] a Doppler frequency reconstruction module configured to calculate a ground view direction of the main image according to main image imaging parameters, set the ground view direction of the auxiliary image to be consistent with the ground view direction of the main image, and inversely solve the reconstructed Doppler frequency of the auxiliary image based on the ground view direction;

[0043] an azimuth parameter reconstruction module configured to calculate an azimuth pixel resolution of the main image according to an azimuth time resolution of the main image and a flight speed, set the azimuth pixel resolution of the auxiliary image to be consistent with the azimuth pixel resolution of the main image, and inversely solve a reconstructed azimuth time resolution of the auxiliary image based on the azimuth pixel resolution and a flight speed of the auxiliary image platform;

[0044] a range parameter setting module configured to set the reconstructed range pixel resolution of the auxiliary image to be consistent with the range pixel resolution of the main image;

[0045] a resampling module configured to generate a reconstructed auxiliary image parameter file, establish a positioning relationship between the auxiliary image and the reconstructed auxiliary image, and resample the auxiliary image to obtain the reconstructed auxiliary image.

[0046] As a possible implementation manner of the embodiment, the Doppler frequency reconstruction module comprises:

[0047] a main image parameter calculation module configured to select a main image center point, acquire an image coordinate thereof, determine a corresponding platform flight speed according to an azimuth image coordinate, and calculate a main image off-nadir angle;

[0048] a main image ground view direction determination module configured to acquire an off-nadir distance according to a range image coordinate, calculate a projection length of the off-nadir distance on an ortho direction, a ground distance, an ortho direction projection ground distance, and a ground projection off-nadir angle, and determine the main image ground view direction in combination with a main image heading azimuth angle;

[0049] an auxiliary image coordinate calculation module configured to calculate geographical coordinates from the main image center point image coordinate in combination with a local average elevation by using a range-Doppler (R-D) model, and calculate image coordinates of a corresponding auxiliary image point according to the geographical coordinates;

[0050] a reconstructed auxiliary image Doppler frequency inverse solving module configured to set the ground view direction of the auxiliary image to be consistent with the ground view direction of the main image, calculate a ground projection off-nadir angle thereof according to an auxiliary image heading azimuth angle, and inversely solve the reconstructed auxiliary image Doppler frequency in combination with an auxiliary image platform flight speed, an off-nadir distance, and a flight height.

[0051] As a possible implementation manner of the embodiment, the azimuth parameter reconstruction module comprises:

[0052] a main image resolution calculation module, configured to calculate a main image azimuth pixel resolution by using a main image platform flight speed, and to determine a spatial scale of the main image in the azimuth direction;

[0053] a secondary image time resolution inversion module, configured to set the secondary image azimuth pixel resolution and the main image azimuth time resolution to be consistent, and to inversely calculate the reconstructed secondary image azimuth time resolution by using a secondary image platform flight speed.

[0054] As a possible implementation manner of the embodiment, the resampling module comprises:

[0055] a parameter file generation module, configured to modify a secondary image parameter file, update a Doppler frequency to a reconstructed frequency, an azimuth time resolution to a reconstructed time resolution, and a range pixel resolution to a set resolution, and generate a reconstructed secondary image parameter file;

[0056] a positioning model establishment module, configured to establish a geometric positioning model of the secondary image and the reconstructed secondary image based on imaging parameters, and to determine a spatial mapping relationship between the two;

[0057] an interpolation sampling module, configured to initialize the reconstructed secondary image according to a secondary image size, to realize mapping from a reconstructed secondary image coordinate to a secondary image coordinate pixel by pixel through the positioning model, to obtain a pixel value by using an interpolation algorithm, to complete resampling, and to finally obtain a reconstructed secondary image that is spatially aligned with the main image.

[0058] In a third aspect, an electronic device is provided, which comprises a processor, a memory and a bus, the memory stores machine readable instructions executable by the processor, when the electronic device is running, the processor and the memory communicate through the bus, and the processor executes the machine readable instructions to perform the steps of the method for reconstructing the airborne multi-pass InSAR image.

[0059] In a fourth aspect, a storage medium is provided, which stores a computer program, when the computer program is run by a processor, the steps of the method for reconstructing the airborne multi-pass InSAR image are performed.

[0060] The technical scheme of the embodiment of the present application has the following beneficial effects:

[0061] The application solves the problem of inconsistent spatial directions of the main and auxiliary images by reconstructing the Doppler frequency of the auxiliary image so that the ground sight directions of the main and auxiliary images are consistent, solves the problem of mismatched spatial scales by unifying the azimuth and range pixel resolutions of the main and auxiliary images, thereby realizing the spatial alignment of the main and auxiliary images and significantly improving the interference registration accuracy, and ensures the accuracy and reliability of the reconstruction process by inversely reconstructing the parameters based on the physical imaging model, thereby laying a solid foundation for subsequent high-quality interference processing and three-dimensional information inversion.

[0062] The application realizes the spatial alignment of the airborne multi-pass InSAR main and auxiliary images by parameter and image reconstruction, and is used for subsequent high-precision interference registration and three-dimensional inversion. The application can reconstruct the auxiliary image by reconstructing the Doppler frequency, azimuth time resolution and range pixel resolution during the interference processing of the SAR image data, thereby solving the problem of inconsistent spatial scales and directions of the airborne multi-pass InSAR main and auxiliary images, and has better technical effects. BRIEF DESCRIPTION OF DRAWINGS

[0063] Figure 1 is a reconstruction method flowchart of airborne multi-pass InSAR images according to an exemplary embodiment;

[0064] Figure 2 is a structural schematic diagram of a reconstruction device of airborne multi-pass InSAR images according to an exemplary embodiment;

[0065] Figure 3 is a schematic diagram of inversely reconstructing the Doppler frequency of the auxiliary image according to the ground sight direction according to an exemplary embodiment. DETAILED DESCRIPTION

[0066] To more clearly illustrate the technical features of the application scheme, the application is described in detail below with reference to the specific embodiments and the accompanying drawings.

[0067] As shown in Figure 1 , the reconstruction method of the airborne multi-pass InSAR images provided by the embodiment of the application includes the following steps:

[0068] Step S1, acquiring the main image data and auxiliary image data of the airborne multi-pass InSAR;

[0069] Step S2, calculating the ground sight direction of the main image according to the imaging parameters of the main image, setting the ground sight direction of the auxiliary image to be consistent with the main image, and inversely reconstructing the Doppler frequency of the auxiliary image after reconstruction based on the ground sight direction;

[0070] Step S3, calculating the azimuth direction pixel resolution of the main image according to the azimuth direction time resolution and the flight speed, setting the azimuth direction pixel resolution of the auxiliary image consistent with the main image, and inversely solving the azimuth direction time resolution of the reconstructed auxiliary image based on the azimuth direction pixel resolution and the flight speed of the auxiliary image platform;

[0071] Step S4, setting the range direction pixel resolution of the reconstructed auxiliary image consistent with the range direction pixel resolution of the main image;

[0072] Step S5, generating a reconstructed auxiliary image parameter file, establishing the positioning relationship between the auxiliary image and the reconstructed auxiliary image, resampling the auxiliary image, and obtaining the reconstructed auxiliary image.

[0073] As a possible implementation manner of the embodiment, the step S2 includes the following steps:

[0074] Step S21, selecting a main image center point, obtaining the image coordinates thereof, determining the corresponding platform flight speed according to the azimuth direction image coordinates, and calculating the oblique viewing angle of the main image; this sub-step determines the relevant parameters of the main image center point and calculates the oblique viewing angle, thereby providing key angle information for subsequent determination of the ground line-of-sight direction;

[0075] Step S22, obtaining the slant range according to the range direction image coordinates, calculating the projection length of the slant range on the forward-looking direction, the ground distance, the forward-looking direction projection ground distance, and the ground projection oblique viewing angle, and determining the ground line-of-sight direction of the main image in combination with the heading azimuth of the main image; this step comprehensively considers multiple parameters to accurately obtain the direction reference of the ground observed by the main image;

[0076] Step S23, using a range-Doppler (R-D) model to calculate the geographic coordinates from the main image center point image coordinates in combination with the local average elevation, and then calculating the image coordinates of the corresponding auxiliary image point according to the geographic coordinates; the role of this step is to establish the association between the main image and the auxiliary image in the geographic coordinate layer, thereby providing an association basis for subsequent adjustment of the auxiliary image parameters;

[0077] Step S24, setting the ground line-of-sight direction of the auxiliary image consistent with the main image, calculating the ground projection oblique viewing angle according to the heading azimuth of the auxiliary image, inversely solving the Doppler frequency of the reconstructed auxiliary image in combination with the platform flight speed, the slant range, and the flight height of the auxiliary image; through this sub-step, the Doppler frequency of the auxiliary image is matched with the main image in the ground line-of-sight direction, thereby ensuring that the auxiliary image is consistent with the main image in the ground line-of-sight direction, and laying a foundation for subsequent spatial alignment.

[0078] As a possible implementation manner of the embodiment, the step S3 includes the following steps:

[0079] Step S31, the main image platform flight speed is used to calculate the main image azimuth pixel resolution, and the spatial scale of the main image in the azimuth direction is determined;

[0080] Step S32, the azimuth pixel resolution of the auxiliary image and the azimuth time resolution of the main image are set to be consistent, and the azimuth time resolution of the reconstructed auxiliary image is inversely calculated based on the platform flight speed of the auxiliary image. Through this step, the azimuth time resolution of the auxiliary image is adjusted based on the azimuth pixel resolution of the main image, so that the spatial scales of the two in the azimuth direction are unified.

[0081] As a possible implementation manner of the embodiment, the step S5 includes the following steps:

[0082] Step S51, the auxiliary image parameter file is modified, the Doppler frequency is updated to the reconstructed frequency, the azimuth time resolution is updated to the reconstructed time resolution, and the range pixel resolution is updated to the set resolution, so as to generate a reconstructed auxiliary image parameter file. This step integrates the parameters reconstructed in the foregoing steps into the parameter file, so as to provide comprehensive and accurate parameter guidance for subsequent resampling;

[0083] Step S52, a geometric positioning model of the auxiliary image and the reconstructed auxiliary image is established based on the imaging parameters. Through the model, the spatial correspondence between each pixel point of the auxiliary image and the reconstructed auxiliary image is determined.

[0084] Step S53, the reconstructed auxiliary image is initialized according to the size of the auxiliary image. The mapping from the coordinates of the reconstructed auxiliary image to the coordinates of the auxiliary image is realized pixel by pixel through the positioning model, the pixel value is obtained by using an interpolation algorithm, the resampling is completed, and finally the reconstructed auxiliary image that is spatially aligned with the main image is obtained. This step performs pixel-by-pixel resampling on the auxiliary image based on the positioning relationship established in the foregoing steps, so as to generate the reconstructed auxiliary image that meets the spatial alignment requirement.

[0085] As a possible implementation manner of the embodiment, the step S2 includes the following steps:

[0086] Step S21, a center point of the main image is selected, and the image coordinates of the center point are obtained According to the azimuth image coordinates , the corresponding platform flight speed is determined, the main image oblique angle is calculated, wherein is the Doppler frequency of the main image, and is the radar wavelength.

[0087] Step S22, the slant range is obtained according to the range image coordinates , the projection length of the slant range in the normal side view direction is calculated, the ground range is calculated, and the ground range in the normal side view direction and ground projection oblique view angle , is the main image ground view direction, and the main image heading azimuth angle is combined to determine the main image ground view direction . The role of this step is to accurately obtain the direction reference of the main image observed ground;

[0088] Step S23, according to the SAR image geometric positioning model, the main image center point image coordinate is combined with the local average elevation to calculate the geographic coordinates , and then according to the geographic coordinates , the image coordinates of the corresponding auxiliary image point are calculated . The role is to establish the correlation of the main and auxiliary images in geographic coordinates, and the SAR image geometric positioning model adopts the range-Doppler (R-D) model:

[0089] ,

[0090] Among them, is the distance imaging condition observation equation, is the Doppler imaging condition observation equation, is the geographic coordinate, is the image coordinate;

[0091] Step S24, set the auxiliary image ground view direction consistent with the main image ground view direction as , according to the auxiliary image heading azimuth angle , the ground projection oblique view angle is calculated, combined with the auxiliary image platform flight speed , the slant range and the altitude , the reconstructed auxiliary image Doppler frequency is back calculated , wherein the auxiliary image oblique view angle , the slant range is the length of the projection in the normal side direction , the normal side direction projection ground distance , the auxiliary image point ground distance , so as to ensure that the auxiliary image and the main image are consistent in the ground view direction, and lay the foundation for subsequent spatial alignment.

[0092] As a possible implementation manner of the embodiment, the step S3, the specific steps are:

[0093] Calculate the main image azimuth direction pixel resolution: , wherein is the main image platform flight speed, is the main image azimuth direction time resolution, which can clearly determine the spatial scale of the main image in the azimuth direction;​

[0094] If the azimuth pixel resolution of the auxiliary image is set to be the same as the azimuth temporal resolution of the primary image, then the azimuth pixel resolution of the auxiliary image will be: Inversely calculate the azimuth temporal resolution of the reconstructed auxiliary image. , To aid in the flight speed of the imaging platform.

[0095] As one possible implementation of this embodiment, step S4 specifically involves setting the range pixel resolution of the reconstructed auxiliary image. Distance pixel resolution relative to the main image Consistency, that is The simple and direct setup ensures consistency between primary and secondary images in terms of spatial scale in the distance direction, eliminating the need for complex calculations and intuitively and effectively improving the foundation for image matching.

[0096] As one possible implementation of this embodiment, step S5 specifically includes:

[0097] Doppler frequency from auxiliary image parameter file Azimuth time resolution and distance pixel resolution Modified to the reconstructed Doppler frequency Azimuth time resolution and distance pixel resolution Generate the reconstructed auxiliary image parameter file;

[0098] Geometric positioning models for auxiliary and reconstructed auxiliary images are established based on imaging parameters;

[0099] A reconstructed auxiliary image is created based on the size of the auxiliary image; then the image coordinates of the reconstructed auxiliary image points are used. Starting point, combined with local average elevation Calculate geographic coordinates based on the geometric positioning model Then, based on geographical coordinates and local average elevation Calculate the image coordinates of the corresponding auxiliary image points based on the geometric positioning model. According to image coordinates Pixel values ​​are obtained by interpolation sampling on the secondary image and then filled into the reconstructed secondary image. Image point location; thus, pixel-by-pixel localization and resampling processing is performed on the reconstructed auxiliary image to obtain the final reconstructed auxiliary image.

[0100] like Figure 2 As shown in the figure, an airborne multi-flight InSAR image reconstruction device provided by an embodiment of the present invention includes:

[0101] The data acquisition module is configured to acquire main image data and auxiliary image data of airborne multi-pass InSAR;

[0102] The Doppler frequency reconstruction module is configured to calculate a ground view direction of the main image according to imaging parameters of the main image, set a ground view direction of the auxiliary image to be consistent with the main image, and inversely solve the reconstructed Doppler frequency of the auxiliary image based on the ground view direction.

[0103] The azimuth parameter reconstruction module is configured to calculate an azimuth pixel resolution of the main image according to an azimuth time resolution and a flight speed of the main image, set an azimuth pixel resolution of the auxiliary image to be consistent with the main image, and inversely solve a reconstructed azimuth time resolution of the auxiliary image based on the azimuth pixel resolution and a flight speed of the auxiliary image.

[0104] The range parameter setting module is configured to set a reconstructed range pixel resolution of the auxiliary image to be consistent with a range pixel resolution of the main image.

[0105] The resampling module is configured to generate a reconstructed auxiliary image parameter file, establish a positioning relationship between the auxiliary image and the reconstructed auxiliary image, and resample the auxiliary image to obtain the reconstructed auxiliary image.

[0106] As a possible implementation manner of the embodiment, the Doppler frequency reconstruction module comprises:

[0107] The main image parameter calculation module is configured to select a center point of the main image, acquire an image coordinate of the center point, determine a corresponding platform flight speed according to an azimuth image coordinate, and calculate an oblique viewing angle of the main image.

[0108] The main image ground view direction determination module is configured to acquire an slant range according to a range image coordinate, calculate a projection length of the slant range in a normal side view direction, a ground range, a normal side view direction projection ground range, and a ground projection oblique viewing angle, and determine a ground view direction of the main image in combination with a heading azimuth angle of the main image.

[0109] The auxiliary image coordinate calculation module is configured to calculate geographical coordinates from the image coordinate of the center point of the main image in combination with a local average elevation, and then calculate an image coordinate of a corresponding auxiliary image point according to the geographical coordinates.

[0110] The reconstructed auxiliary image Doppler frequency inverse solving module is configured to set the ground view direction of the auxiliary image to be consistent with the main image, calculate a ground projection oblique viewing angle of the auxiliary image according to a heading azimuth angle of the auxiliary image, and inversely solve the reconstructed Doppler frequency of the auxiliary image in combination with a platform flight speed of the auxiliary image, a slant range, and a flight height.

[0111] As a possible implementation manner of the embodiment, the azimuth parameter reconstruction module comprises:

[0112] The main image resolution calculation module is configured to calculate a main image azimuth pixel resolution by using a main image platform flight speed, and to determine a spatial scale of the main image in the azimuth direction.

[0113] The auxiliary image time resolution reverse calculation module is configured to set the auxiliary image azimuth pixel resolution and the main image azimuth time resolution to be consistent, and to reverse calculate the reconstructed auxiliary image azimuth time resolution by using an auxiliary image platform flight speed.

[0114] As a possible implementation manner of the embodiment, the resampling module comprises:

[0115] The parameter file generation module is configured to modify an auxiliary image parameter file, update a Doppler frequency to a reconstructed frequency, an azimuth time resolution to a reconstructed time resolution, and a range pixel resolution to a set resolution, and generate a reconstructed auxiliary image parameter file.

[0116] The positioning model establishment module is configured to establish a geometric positioning model of the auxiliary image and the reconstructed auxiliary image based on imaging parameters, and to determine a spatial mapping relationship between the auxiliary image and the reconstructed auxiliary image.

[0117] The interpolation sampling module is configured to initialize the reconstructed auxiliary image according to the auxiliary image size, to realize mapping from a reconstructed auxiliary image coordinate to an auxiliary image coordinate by using the positioning model, to obtain a pixel value by using an interpolation algorithm, to complete resampling, and to finally obtain the reconstructed auxiliary image which is spatially aligned with the main image.

[0118] The specific process of reconstructing the airborne multi-pass InSAR image by using the technical scheme of the embodiment is as follows.

[0119] Step 1: Obtain the airborne multi-pass InSAR main and auxiliary image data.

[0120] Collect the airborne multi-pass InSAR data of a certain region, including the original data and imaging parameters (a radar wavelength, a flight height, a flight speed, a Doppler frequency, azimuth / range resolutions, etc.) of the main image and the auxiliary image. This step provides basic data for the entire reconstruction process and is a prerequisite for subsequent processing. Different pass image data carries information of different perspectives and times of the target region, and these data need to be obtained to enable subsequent analysis and processing to achieve image reconstruction.

[0121] Step 2: Calculate the main image ground sight direction according to the main image imaging parameters, set the auxiliary image ground sight direction to be consistent with the main image, and reverse calculate the reconstructed auxiliary image Doppler frequency according to the ground sight direction.

[0122] Take the center point of the main image, and the image coordinates of the center point are , obtain the corresponding platform flight speed according to the azimuth image coordinates , and then calculate the oblique viewing angle :

[0123] ,

[0124] in, Main image Doppler frequency, The radar wavelength;

[0125] Based on distance image coordinates Obtaining the slope distance Calculate the projected length of the slant range in the frontal side view direction. ; Calculate the distance between the two places , Main image flight altitude; calculate the projected ground distance in the frontal and side views. ; Calculate the oblique angle of the ground projection Calculate the ground view direction of the main image. , The azimuth of the main image;

[0126] Based on the SAR image geometric positioning model, the image coordinates of the main image center point are used. Combined with local average elevation Calculate geographic coordinates Then, based on the geometric positioning model, by and Calculate the image coordinates of the auxiliary image points The range-Doppler (RD) model is used as the geometric positioning model, and the positioning model equation can be expressed as:

[0127] ,

[0128] in, The observation equation is for range imaging conditions. The observation equation for Doppler imaging conditions, For geographic coordinates, Image coordinates;

[0129] The ground line of sight in the secondary image should be consistent with that in the primary image. Calculate the oblique angle of the ground projection based on the direction of the line of sight on the ground. , Auxiliary image azimuth angle; based on azimuth image coordinates Platform speed for acquiring auxiliary images Based on distance to image coordinates Obtaining the slope distance Calculate the distance between the image points and the ground in the auxiliary image. , For auxiliary imagery altitude; calculate the projected ground distance in the frontal and side views. ; Calculate the projected length of the slant range in the frontal side view direction , calculate auxiliary image squint angle , finally inverse reconstruct auxiliary image Doppler frequency , as shown in Figure 3 ;

[0130] The main image ground view direction determines the angle of radar observation on the ground, by setting the auxiliary image the same, can make the two unified in the observation direction; inverse Doppler frequency is the key parameter of adjusting auxiliary image, to match the observation characteristics of main image, to provide direction consistency guarantee for subsequent interference processing.

[0131] Step 3, according to the main image azimuth time resolution and flight speed to calculate the main image azimuth pixel resolution, set the auxiliary image azimuth pixel resolution and the main image azimuth pixel resolution consistent, according to the azimuth pixel resolution and auxiliary image platform flight speed inverse reconstruct auxiliary image azimuth time resolution.

[0132] Use the main image platform flight speed calculated in step 2 , calculate the main image azimuth pixel resolution , for the main image azimuth time resolution;

[0133] Set the auxiliary image azimuth pixel resolution and the main image consistent with , use the auxiliary image platform flight speed calculated in step 2 , inverse reconstruct auxiliary image azimuth time resolution ;

[0134] Step 3 unified the main auxiliary image in the azimuth direction of space scale, to ensure that the two in the azimuth pixel representative actual ground distance consistent, help to improve the image matching and interference processing precision.

[0135] Step 4, set the reconstructed auxiliary image range pixel resolution and the main image range pixel resolution consistent.

[0136] Set the reconstructed auxiliary image range pixel resolution and the main image range pixel resolution consistent, that is . The setting ensures that the main auxiliary image in the distance direction of space scale, make the image in the distance dimension has comparability, for subsequent image fusion and interference operation foundation.

[0137] Step 5, generate reconstructed auxiliary image parameter file, establish the positioning relationship between auxiliary image and reconstructed auxiliary image, resample the auxiliary image, get the reconstructed auxiliary image.

[0138] Modify the Doppler frequency in the auxiliary image parameter file Azimuth time resolution And range pixel resolution , modified to the reconstructed , Range pixel resolution , generate a reconstruction auxiliary image parameter file. According to the imaging parameters, the geometric positioning model of the auxiliary image and the reconstructed auxiliary image is established;

[0139] According to the size of the auxiliary image, the reconstructed auxiliary image is established. Then, starting from the image coordinates of the reconstructed auxiliary image points , combined with the local average elevation , the geographic coordinates are calculated according to the geometric positioning model ; and and According to the geometric positioning model, the image coordinates of the corresponding auxiliary image points are calculated , according to the image coordinates , interpolation sampling is carried out on the auxiliary image to obtain the pixel value, which is filled into the pixel position of the reconstructed auxiliary image; the reconstructed auxiliary image is processed by pixel-by-pixel positioning and resampling to obtain the final reconstructed auxiliary image;

[0140] The reconstruction auxiliary image parameter file integrates the parameters obtained in the previous steps, and provides the basis for image resampling; the positioning relationship is established, which clarifies the corresponding relationship between the new and old images; the resampling process is carried out according to the new parameters to resample the auxiliary image, and the reconstructed auxiliary image which is matched with the main image in spatial scale and direction is generated.

[0141] The electronic device provided by the embodiment of the application comprises a processor, a memory and a bus, the memory stores machine readable instructions executable by the processor, when the electronic device is running, the processor and the memory communicate through the bus, and the processor executes the machine readable instructions to execute the steps of the reconstruction method of the airborne multi-pass InSAR image.

[0142] Specifically, the above-mentioned memory and processor can be general memory and processor, which are not limited here, when the processor runs the computer program stored in the memory, the reconstruction method of the airborne multi-pass InSAR image can be executed.

[0143] Corresponding to the starting method of the above-mentioned application program, the embodiment of the application further provides a storage medium, the storage medium stores a computer program, when the computer program is run by the processor, the steps of the reconstruction method of the airborne multi-pass InSAR image are executed.

[0144] It should be pointed out finally that the above embodiments are only used to illustrate the technical solutions of the present application but not to limit it. Although the present application has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that the specific embodiments of the present application can be modified or replaced equivalently without departing from the spirit and scope of the present application, and any modification or equivalent replacement without departing from the spirit and scope of the present application should be covered in the protection scope of the claims of the present application.

Claims

1. A method for reconstructing airborne multi-flight InSAR imagery, characterized in that, Includes the following steps: Step S1: Acquire airborne multi-flight InSAR main image data and auxiliary image data; Step S2: Calculate the ground viewing direction of the main image based on the imaging parameters of the main image, set the ground viewing direction of the auxiliary image to be consistent with the main image, and calculate the Doppler frequency of the reconstructed auxiliary image based on the ground viewing direction. Step S3: Calculate the azimuth pixel resolution of the main image based on the azimuth temporal resolution and flight speed of the main image, set the azimuth pixel resolution of the auxiliary image to be consistent with the azimuth pixel resolution of the main image, and calculate the azimuth temporal resolution of the reconstructed auxiliary image based on the azimuth pixel resolution and the flight speed of the auxiliary image platform. Step S4: Set the range pixel resolution of the reconstructed auxiliary image to be consistent with the range pixel resolution of the main image; Step S5: Generate a parameter file for the reconstructed auxiliary image, establish the positioning relationship between the auxiliary image and the reconstructed auxiliary image, resample the auxiliary image, and obtain the reconstructed auxiliary image.

2. The method for reconstructing airborne multi-flight InSAR imagery according to claim 1, characterized in that, Step S2 includes the following steps: Step S21: Select the center point of the main image, obtain its image coordinates, determine the corresponding platform flight speed based on the azimuth image coordinates, and calculate the oblique angle of the main image. Step S22: Obtain the slant range based on the distance to the image coordinates, calculate the projection length of the slant range in the frontal side view direction, the ground distance, the projection ground distance in the frontal side view direction, and the ground projection slant angle, and combine the main image heading azimuth angle to determine the ground line of sight direction of the main image. Step S23: Using the distance-Doppler model, the geographic coordinates are calculated by combining the image coordinates of the center point of the main image with the local average elevation, and then the image coordinates of the corresponding auxiliary image points are calculated based on the geographic coordinates. Step S24: Set the ground line of sight of the auxiliary image to be consistent with the ground line of sight of the main image. Calculate the ground projection angle based on the azimuth of the auxiliary image. Combine the flight speed, slant range, and altitude of the auxiliary image platform to inversely calculate the Doppler frequency of the reconstructed auxiliary image.

3. The method for reconstructing airborne multi-flight InSAR imagery according to claim 1, characterized in that, Step S3 includes the following steps: Step S31: Calculate the azimuth resolution of the main image using the flight speed of the main image platform to determine the spatial scale of the main image in the azimuth direction. Step S32: Set the azimuth pixel resolution of the auxiliary image to be the same as the azimuth temporal resolution of the main image, and use the flight speed of the auxiliary image platform to inversely calculate the azimuth temporal resolution of the reconstructed auxiliary image.

4. The method for reconstructing airborne multi-flight InSAR imagery according to claim 1, characterized in that, Step S5 includes the following steps: Step S51: Modify the auxiliary image parameter file, update the Doppler frequency to the reconstructed frequency, the azimuth temporal resolution to the reconstructed temporal resolution, and the range pixel resolution to the set resolution, and generate the reconstructed auxiliary image parameter file. Step S52: Based on the imaging parameters, establish a geometric positioning model of the auxiliary image and the reconstructed auxiliary image, and clarify the spatial mapping relationship between the two. Step S53: Initialize and reconstruct the auxiliary image according to the auxiliary image size. Pixel by pixel, the mapping from the coordinates of the reconstructed auxiliary image to the coordinates of the auxiliary image is realized through the positioning model. The pixel value is obtained by interpolation algorithm, and resampling is completed. Finally, the reconstructed auxiliary image aligned with the main image space is obtained.

5. A reconstruction device for airborne multi-flight InSAR imagery, characterized in that, include: The data acquisition module is used to acquire airborne multi-flight InSAR main image data and auxiliary image data; The Doppler frequency reconstruction module is used to calculate the ground line of sight of the main image based on the imaging parameters of the main image, set the ground line of sight of the auxiliary image to be consistent with the ground line of sight of the main image, and calculate the Doppler frequency of the reconstructed auxiliary image based on the ground line of sight. The azimuth parameter reconstruction module is used to calculate the azimuth pixel resolution of the main image based on the azimuth temporal resolution and flight speed of the main image, set the azimuth pixel resolution of the auxiliary image to be consistent with the azimuth pixel resolution of the main image, and inversely calculate the azimuth temporal resolution of the reconstructed auxiliary image based on the azimuth pixel resolution and the flight speed of the auxiliary image platform. The range parameter setting module is used to set the range pixel resolution of the reconstructed auxiliary image to be consistent with the range pixel resolution of the main image; The resampling module is used to generate a parameter file for the reconstructed auxiliary image, establish the positioning relationship between the auxiliary image and the reconstructed auxiliary image, and resample the auxiliary image to obtain the reconstructed auxiliary image.

6. The airborne multi-flight InSAR image reconstruction device according to claim 5, characterized in that, The Doppler frequency reconstruction module includes: The main image parameter calculation module is used to select the center point of the main image, obtain its image coordinates, determine the corresponding platform flight speed based on the azimuth image coordinates, and calculate the oblique angle of the main image. The main image ground line of sight direction determination module is used to obtain the slant distance from the image coordinates based on the distance, calculate the projection length of the slant distance in the front side view direction, the ground distance, the projection ground distance in the front side view direction, and the ground projection slant angle, and combine it with the main image heading azimuth angle to determine the main image ground line of sight direction; The auxiliary image coordinate calculation module is used to calculate the geographic coordinates of the main image center point by combining the image coordinates with the local average elevation using the distance-Doppler model, and then calculate the image coordinates of the corresponding auxiliary image points based on the geographic coordinates. The module for reconstructing the Doppler frequency of the auxiliary image is used to set the ground line of sight of the auxiliary image to be consistent with the ground line of sight of the main image. It calculates the ground projection angle based on the azimuth of the auxiliary image and, in combination with the flight speed, slant range and altitude of the auxiliary image platform, inversely calculates the Doppler frequency of the reconstructed auxiliary image.

7. The airborne multi-flight InSAR image reconstruction device according to claim 5, characterized in that, The azimuth parameter reconstruction module includes: The main image resolution calculation module is used to calculate the azimuth pixel resolution of the main image using the flight speed of the main image platform, and to determine the spatial scale of the main image in the azimuth direction. The auxiliary image temporal resolution inverse calculation module is used to set the azimuth pixel resolution of the auxiliary image to be consistent with the azimuth temporal resolution of the main image, and to inversely calculate the azimuth temporal resolution of the reconstructed auxiliary image using the flight speed of the auxiliary image platform.

8. The airborne multi-flight InSAR image reconstruction device according to claim 5, characterized in that, The resampling module includes: The parameter file generation module is used to modify the auxiliary image parameter file, update the Doppler frequency to the reconstructed frequency, the azimuth temporal resolution to the reconstructed temporal resolution, and the range pixel resolution to the set resolution, and generate the reconstructed auxiliary image parameter file. The localization model building module is used to build geometric localization models of auxiliary images and reconstructed auxiliary images based on imaging parameters, and to clarify the spatial mapping relationship between the two. The interpolation sampling module is used to initialize and reconstruct the auxiliary image according to the auxiliary image size. It uses a positioning model to map the coordinates of the reconstructed auxiliary image to the coordinates of the auxiliary image pixel by pixel, uses an interpolation algorithm to obtain pixel values, completes resampling, and finally obtains the reconstructed auxiliary image that is aligned with the main image space.

9. An electronic device, characterized in that, The device includes a processor, a memory, and a bus. The memory stores machine-readable instructions that the processor can execute. When the electronic device is running, the processor communicates with the memory via the bus, and the processor executes the machine-readable instructions to perform the steps of the airborne multi-flight InSAR image reconstruction method as described in any one of claims 1-4.

10. A storage medium, characterized in that, The storage medium stores a computer program that, when executed by a processor, performs the steps of the airborne multi-flight InSAR image reconstruction method as described in any one of claims 1-4.

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