A spaceborne InSAR atmospheric correction method combined with GACOS

Abstract

The present invention discloses a spaceborne InSAR atmospheric correction method combined with GACOS. The method comprises the following steps: first, obtaining original satellite SAR images, then co-registering the original satellite SAR images to a common master image, performing interferometric processing to obtain a entangled interferometric image, and finally obtaining an unentangled original interferometric image; then, using the GACOS online service to generate atmospheric correction data for all images, performing initial atmospheric correction on all the original interferometric images; then, recombining all the original interferometric images that have undergone initial atmospheric correction into several subsets according to the SAR images; then, performing principal component analysis on each subset, removing the principal component components that reach a threshold in each subset, and then restoring the subset to an interferometric image; finally, inputting the restored interferometric image into a small baseline set InSAR for time series analysis to generate cumulative deformation, deformation rate, and terrain error. The present invention is easy to operate, has good effects, saves resources, and has a wide range of applications and is not restricted by the platform.

Description

Technical Field

[0001] The present invention relates to the field of radar measurement technology, and in particular to a spaceborne InSAR atmospheric correction method combined with GACOS. Background Art

[0002] Synthetic aperture radar interferometry (InSAR) is an advanced geodetic tool with the characteristics of strong all-day and all-weather working capability, wide spatial coverage, high spatial resolution, high measurement accuracy, and no need for ground instruments. It has been widely used in high spatial resolution surface deformation measurement.

[0003] Synthetic Aperture Radar (InSAR) interferometry relies on SAR imagery generated by active microwave remote sensing satellites. SAR signals travel from the satellite, through the atmosphere, and then through the atmosphere before being received by the satellite. In the troposphere, the propagation speed of electromagnetic waves is linearly related to the refractive index. However, variations in atmospheric parameters such as temperature, pressure, and humidity within the troposphere cause significant differences in the refractive index at different locations and altitudes. Generating InSAR images requires interferometric processing of two SAR images taken at different times. However, the spatial distribution of the atmosphere at two different times varies significantly, resulting in a lack of regularity in the atmospheric errors in InSAR images, making them difficult to address with simple methods. Summary of the Invention

[0004] The purpose of the present invention is to overcome the problems existing in the above-mentioned prior art and provide a space-borne InSAR atmospheric correction method combined with GACOS, thereby solving the problems raised in the above-mentioned background technology.

[0005] To this end, the present invention provides a spaceborne InSAR atmospheric correction method combined with GACOS, comprising the following steps:

[0006] Step 1: Obtain the original satellite SAR image, as well as the satellite orbit data and terrain data corresponding to the original SAR image;

[0007] Step 2: The original satellite SAR image is co-registered to the common master image, and interferometric processing is performed to obtain a entangled interferometric image. The entangled interferometric image is then phase unwrapped using the minimum cost flow algorithm based on the Delaunay triangulation to form the unwrapped original interferometric image.

[0008] Step 3: Generate atmospheric correction data for all images using the GACOS online service, and perform initial atmospheric correction on all the original interferometric images;

[0009] Step 4: recombining all the original interferometric images that have undergone initial atmospheric correction into several subsets according to SAR images, wherein the subsets include: interferometric images with the SAR image as the primary image and interferometric images with the SAR image as the secondary image;

[0010] Step 5: Perform principal component analysis on each of the subsets, set a corresponding threshold value for each subset, remove the principal component components in each subset that reach the threshold value, and then restore the subset to an interference image;

[0011] Step 6: Input the interferometric image restored in step 5 into the small baseline set InSAR and perform time series analysis to obtain the cumulative deformation, deformation rate, and terrain error.

[0012] Furthermore, in step 5, when performing principal component analysis on the subsets respectively, the following steps are included:

[0013] Step 5-1: combining the interference images of each subset into a two-dimensional matrix;

[0014] Step 5-2: Perform singular value decomposition on each two-dimensional matrix, set a corresponding threshold for each subset, and remove the principal component components that reach the threshold in each subset;

[0015] Step 5-3: Restore the subset to the interferometric image.

[0016] Furthermore, in step 2, when the original interferometric image is obtained, high-precision position information is acquired using the orbital data, and the terrain phase is eliminated using the terrain data.

[0017] Furthermore, in step 6, the components removed during principal component analysis are adjusted according to the temporal resolution of different SAR images and the setting of the time threshold in the small baseline set InSAR.

[0018] The present invention provides a spaceborne InSAR atmospheric correction method combined with GACOS, which has the following beneficial effects:

[0019] The present invention takes the small baseline set InSAR time series as the research object, adopts the general atmospheric correction model (GACOS) and principal component analysis method to estimate and weaken the influence of atmospheric errors on all InSAR images in the small baseline set InSAR, so as to obtain better time series results. This is a new method for InSAR atmospheric error correction that is easy to operate, has good effects, saves resources, has a wide range of applications, and is not restricted by the use platform. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the processing flow of atmospheric correction of InSAR images;

[0021] Figure 2 This is a flowchart of principal component analysis;

[0022] Figure 3 This is an example of the result of atmospheric correction of InSAR image. DETAILED DESCRIPTION

[0023] Several specific embodiments of the present invention are described in detail below with reference to the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0024] Specifically, such as Figure 1-3 As shown, the present invention is based on small baseline set InSAR, uses a universal atmospheric correction model and principal component analysis method, and aims to use a simple and easy-to-operate method to obtain InSAR images with better correction effects.

[0025] Firstly, the original satellite SAR image and the satellite orbit data and terrain data corresponding to the original SAR image are obtained, the original SAR image is co-registered to the common master image, and the interferometric processing is performed to obtain the entangled interferometric image.

[0026] During interferometric image generation, orbital data is used to obtain high-precision position information, and the terrain data is used to eliminate terrain phase and suppress noise through multi-look operations.

[0027] Secondly, the phase of the entangled interference image is unwrapped using a minimum cost flow algorithm based on Delaunay triangulation to form an unwrapped original interference image.

[0028] Afterwards, the GACOS online service was used to generate atmospheric correction data for all images, and initial atmospheric correction was performed on all interferometric images.

[0029] All the interferometric images that have undergone initial atmospheric correction are reassembled into several subsets according to the SAR images, including: (1) interferometric images with the SAR image as the main image; (2) interferometric images with the SAR image as the secondary image.

[0030] Each subset is processed by principal component analysis, and a corresponding threshold is set for each subset. The principal component components that reach the threshold in each subset are removed, and then the subset is restored to an interferometric image to complete the atmospheric error correction of the principal component analysis.

[0031] The interferometric image that has been corrected for atmospheric errors after principal component analysis is input into the small baseline set InSAR to obtain the cumulative deformation, deformation rate, terrain error, etc.

[0032] According to the time resolution of different SAR images and the setting of the time threshold in the small baseline set InSAR, the components removed during principal component analysis can be adjusted to obtain the best effect.

[0033] When the present invention performs principal component analysis on the subsets respectively, Figure 2 As shown, first, the interference image of each subset is generated into a two-dimensional matrix; secondly, each two-dimensional matrix is ​​subjected to singular value decomposition, and a corresponding threshold is set according to each subset, and the principal component components in each subset that reach the threshold are removed; finally, the subset is restored to the interference image.

[0034] Figure 3 In the figure, the first row shows the original interferometric images, obtained by registering, interfering, and unwrapping the original SAR images. The second row shows the corrected images, obtained by applying the new correction method proposed in this invention to the original interferometric images. The standard deviation of each image is calculated, and the value of the corrected standard deviation minus the original standard deviation is displayed in the figure.

[0035] Depend on Figure 3 The effects of the invention can be seen. First, the atmospheric error in the corrected image is significantly weakened, and the long-wave influence of the atmospheric error is significantly improved. Second, the standard deviation of the corrected image is significantly reduced compared with the original interferometric image. Third, the correlation between the corrected image and the terrain is reduced.

[0036] The above disclosures are only a few specific embodiments of the present invention. However, the embodiments of the present invention are not limited thereto. Any changes that can be conceived by those skilled in the art should fall within the scope of protection of the present invention.

Claims

1. A spaceborne InSAR atmospheric correction method combined with GACOS, characterized in that: The steps include: Step 1: Obtain the original satellite SAR image, as well as the satellite orbit data and terrain data corresponding to the original SAR image; Step 2: The original satellite SAR image is co-registered to the common master image, and interferometric processing is performed to obtain a entangled interferometric image. The entangled interferometric image is then phase unwrapped using the minimum cost flow algorithm based on the Delaunay triangulation to form the unwrapped original interferometric image. Step 3: Generate atmospheric correction data for all images using the GACOS online service, and perform initial atmospheric correction on all the original interferometric images; Step 4: recombining all the original interferometric images that have undergone initial atmospheric correction into several subsets according to SAR images, wherein the subsets include: interferometric images with the SAR image as the primary image and interferometric images with the SAR image as the secondary image; Step 5: Perform principal component analysis on each of the subsets, set a corresponding threshold value for each subset, remove the principal component components in each subset that reach the threshold value, and then restore the subset to an interference image; Step 6: Input the interferometric image restored in step 5 into the small baseline set InSAR inversion algorithm and perform time series analysis to obtain the cumulative deformation, deformation rate, and terrain error; In step 5, when the principal component analysis is performed on the subsets respectively, the following steps are included: Step 5-1: generating a two-dimensional matrix from the interference image of each subset; Step 5-2: Perform singular value decomposition on each two-dimensional matrix, set a corresponding threshold for each subset, and remove the principal component components that reach the threshold in each subset; Step 5-3: Restore the subset to the interference image; In step 6, the components removed during principal component analysis are adjusted according to the temporal resolution of different SAR images and the setting of the time threshold in the small baseline set InSAR.

2. A method for atmospheric correction of spaceborne InSAR in combination with GACOS as claimed in claim 1, characterized in that: In step 2, when the original interferometric image is obtained, high-precision position information is acquired using the orbital data, and the terrain phase is eliminated using the terrain data.

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