Geometric correction method for spotlight-mode satellite SAR (synthetic aperture radar) image

Abstract

The invention discloses a geometric correction method for a spotlight-mode satellite SAR image. The method comprises the following steps: (1) reading related parameters and echo data, and constructing a positioning equation; (2) calculating the coordinates of the position vector and velocity vector of a satellite in a non-rotating geocentric coordinate system at a moment of radar illumination center according to the spatial geometric relationship between the satellite and the earth; (3) completing slope distance and Doppler frequency correction; (4) acquiring the coordinates as well as longitude and latitude of a certain pixel point (i, j) of the satellite SAR image in the non-rotating coordinate system; (5) determining whether all of the pixel points of the satellite SAR image are processed; and (6) re-dividing the latitude-longitude grid, and outputting the geometric correction result. The method provided by the invention can be used for carrying out row-by-row geometric correction on the satellite SAR image, and can process the satellite SAR image in blocks as required due to the completely independent treatment process between the rows of the satellite SAR image, thereby further improving the treatment efficiency.

Description

technical field [0001] The invention belongs to the field of image processing, and relates to an image geometric correction method, in particular to a high-precision geometric correction method of a spaceborne SAR image in a spotlight mode. Background technique [0002] Synthetic Aperture Radar (SAR) satellites have developed rapidly in recent years. Since SAR satellites are not limited by factors such as weather, geography, and time, they can observe the earth all day long and have certain penetrating power, so they are widely used. It is used in military reconnaissance, topographic mapping, resource detection, ocean observation, ecological monitoring, natural disaster monitoring, rapid rescue, etc. [0003] With the development of spaceborne SAR, the quality requirements for spaceborne SAR images are getting higher and higher, which not only requires radar images to have high spatial resolution, but also requires radar images to have high geometric fidelity and radiometric...

AI Technical Summary

Problems solved by technology

Although this method improves the processing efficiency, the processing accuracy is greatly affected, and it is difficult to achieve high-precision geometric correction of spaceborne SAR images

[0008] However, both the geometric correction forward calculation method based on the range-Doppler (R-D) positioning model and the geometric correction inverse calculation method based on the simplified spaceborne SAR spatial geometric model are proposed for the spaceborne strip mode. When the algorithm is applied to the spotlight working mode or the sliding beam spotting working mode, the change of the antenna beam irradiation angle will lead to the mismatch of the equation parameters in the positioning processing, which will cause a large positioning error. Therefore, the traditional positioning processing algorithm does not Not suitable for positioning processing in beamforming mode or sliding beamforming mode

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