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Nonlinear SAR image geometric correction method based on thin-plate spline interpolation

A thin-plate spline, nonlinear technology, applied in the field of radar, can solve the problems of image distortion, nonlinear error, matching error, etc., and achieve the effect of eliminating interference, improving fitting accuracy, and high correction accuracy.

Active Publication Date: 2017-03-29
XIDIAN UNIV
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Problems solved by technology

However, due to the existence of certain nonlinear geometric distortion in the real-time graph, the corresponding relationship of each matching point will have certain nonlinear errors. , resulting in image distortion

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  • Nonlinear SAR image geometric correction method based on thin-plate spline interpolation
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Embodiment Construction

[0020] The present invention will be described in further detail below with reference to accompanying drawing:

[0021] refer to figure 1 , the implementation steps of the present invention are as follows:

[0022] Step 1, SIFT-Like algorithm extracts feature points.

[0023] There are three main types of image features, namely point, line, and surface. Among them, point feature is one of the most common features, mainly including corner points of houses, edge points of images, intersection points of rivers, roads, etc., point feature extraction method There are Moravec algorithm, Forstner algorithm, SIFT algorithm and its improved algorithm, etc. The present invention utilizes a kind of improved algorithm SIFT-Like of SIFT algorithm to extract the feature points of reference map and airborne real-time map respectively, and its steps are as follows:

[0024] (1a) Using the undistorted image obtained from the spaceborne data as the reference image, generate SAR-Harris scale ...

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Abstract

The invention discloses a nonlinear SAR image geometric correction method based on thin-plate spline interpolation, and mainly aims to solve the problem that the nonlinear distortion of an image cannot be corrected precisely in the prior art. The method is implemented according to the following steps: (1) using an SIFT-Like algorithm to extract the feature points of a reference image and a real-time image; (2) using a similarity measure method to select matching points from the feature points of the reference image and the real-time image; (3) using an RANSAC algorithm to purify the matching points, calculating an affine transformation matrix, and getting an accurate affine transformation model, namely, the linear mapping relation of the images; and (4) using a thin-plate spline interpolation function to locally and nonlinearly fit the affine transformation matrix and the actual error on the affine transformation model to get the nonlinear mapping relation of the images, and thus, realizing precise geometric correction of the real-time image. The influence of nonlinear geometric distortion can be eliminated, and the correction accuracy is improved. The method can be used in precise geometric correction of nonlinear distortion of image signals received by radar.

Description

technical field [0001] The invention belongs to the technical field of radar, and mainly relates to a nonlinear SAR image correction method, which can be used for precise geometric correction of radar received image signals. Background technique [0002] As an important evaluation method of SAR system imaging, the research on SAR image geometric correction is the theoretical basis for imaging algorithm design and image-based target recognition. During the imaging process of synthetic aperture radar SAR, due to terrain fluctuations and changes in platform motion, the image has certain nonlinear geometric distortion, so the acquired image is distorted in geometric position. [0003] There is a certain degree of geometric deformation in SAR images, which includes linear mapping and nonlinear mapping. The current traditional method is to approximate the nonlinear mapping transformation relationship between images to a linear mapping relationship. Generally, the RANSAC algorith...

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G06T5/00G06T3/00
CPCG06T2207/10044G06T3/147G06T5/80
Inventor 李亚超项宇泽邹倩雅全英汇邓欢
Owner XIDIAN UNIV
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