SAR Backprojection Using Lock-Down Points for Non-Planar Scenes
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Solution Overview
Problem
Existing synthetic aperture radar (SAR) image generation techniques cause distortion and defocusing when imaging highly non-planar scenes due to projecting radar phase history to a tangential plane, leading to geo-registration errors.
Innovation Solution
Generate a non-planar surface by interpolating slant ranges based on lock down points and radar pulse data, and perform back-projection onto this surface to reduce phase errors and improve image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If radar phase history is projected to a tangential plane, then the SAR image can be generated with simple processing, but image distortion and defocusing occur when the scene is highly non-planar
Solution Approach 1:
The patent applies curvature by replacing the flat tangential plane with a non-planar surface that conforms to the actual terrain geometry. This non-planar surface is constructed using elevation data and lock-down points to create a curved projection surface that matches the topography, thereby eliminating image distortion and defocusing while maintaining processing feasibility
Solution Approach 2:
The patent changes the geometric parameters of the projection surface from a fixed tangential plane to a dynamic non-planar surface defined by multiple lock-down points and elevation data. This parameter change allows the projection surface to adapt to varying terrain heights and slopes, improving image quality for highly non-planar scenes
2Device complexity
If a tangential plane is used for back-projection, then geo-registration is simplified, but geo-registration errors increase for highly non-planar scenes
Solution Approach 1:
The patent uses a non-planar curved surface for back-projection that conforms to the actual terrain, replacing the simplified tangential plane. This curved surface maintains the correct geometric relationship between radar coordinates and ground coordinates across varying elevations, thereby improving geo-registration accuracy without excessive complexity
Solution Approach 2:
The patent performs preliminary construction of the non-planar surface using elevation data and lock-down points before the back-projection process. This preliminary action prepares the correct geometric framework in advance, ensuring accurate geo-registration during the actual image generation without adding complexity to the main processing flow
Data Source
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AI summary
Systems, devices, methods, and computer-readable media improved synthetic aperture radar (SAR) images. A method includes identifying, based on sourced elevation data, N lock down points on a synthetic aperture radar (SAR) image, where N is an integer greater than one, determining, based on radar pulse data and the N lock down points, a slant range for each of the N lock down points resulting in N slant ranges, interpolating, based on the N slant ranges, slant ranges for pixels on an imaging grid of the SAR image resulting in interpolated slant ranges, and back-projecting, based on the interpolated slant ranges and the N slant ranges, the radar pulse data resulting in the SAR image.