SAR Image Rotation via Pre-rotated Data Collection Grid

Solution Overview

Problem

Conventional Synthetic Aperture Radar (SAR) image rotation techniques are computationally expensive and lead to data fidelity loss, especially for complex images required in applications like Interferometric SAR and Coherent Change Detection, due to the need for multi-dimensional interpolation and resampling.

Innovation Solution

Adjusting the SAR data collection process to provide phase history data on a rotated grid in Fourier space, allowing for the formation of SAR images at arbitrary rotation angles without expensive interpolation or resampling operations by controlling radar parameters such as angular pulse spacing, waveform, and timing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If conventional image processing techniques are used to rotate SAR images, then the desired rotational orientation is achieved, but computational cost increases significantly and data fidelity is lost

Engineering Contradiction:

Improveimage rotation capabilityVSAvoiddata fidelity

Core Design Contradiction:

Ease of operationVSLoss of information

Solution Approach 1:

The patent applies preliminary action by pre-rotating the SAR data collection geometry before image formation. The radar antenna is positioned at a squint angle relative to the flight path, and the data is collected on a rotated grid in the Fourier domain. This preliminary rotation of the data collection process eliminates the need for post-processing rotation operations, thereby preserving data fidelity while achieving the desired image orientation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces the mechanical/image-processing system with a data-collection-system approach. Instead of rotating formed images using interpolation algorithms, the system rotates the data collection geometry itself. By adjusting the radar antenna angle and sampling positions during data acquisition, the desired image orientation is achieved directly from the collected data without requiring subsequent rotation operations.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of operation

If conventional image processing techniques are used to rotate SAR images, then the desired rotational orientation is achieved, but computational cost increases significantly

Engineering Contradiction:

Improveimage rotation capabilityVSAvoidprocessing efficiency

Core Design Contradiction:

Ease of operationVSProductivity

Solution Approach 1:

The patent applies preliminary action by pre-rotating the SAR data collection geometry before image formation. The radar antenna is positioned at a squint angle relative to the flight path, and the data is collected on a rotated grid in the Fourier domain. This preliminary rotation of the data collection process eliminates the need for post-processing rotation operations, thereby preserving data fidelity while achieving the desired image orientation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces the mechanical/image-processing system with a data-collection-system approach. Instead of rotating formed images using interpolation algorithms, the system rotates the data collection geometry itself. By adjusting the radar antenna angle and sampling positions during data acquisition, the desired image orientation is achieved directly from the collected data without requiring subsequent rotation operations.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Ease of manufacture

If SAR data is collected with antenna broadside to flight path, then data collection is simple, but image orientation is limited to natural coordinate system

Engineering Contradiction:

Improvedata collection simplicityVSAvoidimage orientation flexibility

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The patent applies dynamics by making the SAR data collection geometry adjustable and flexible. Instead of fixed broadside operation, the system dynamically adjusts the antenna squint angle and data sampling positions according to the desired image orientation. This dynamic capability allows the same SAR system to collect data for multiple different image orientations without hardware modifications, enhancing adaptability while maintaining operational simplicity.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent applies parameter changes by modifying the SAR data collection parameters - specifically the antenna squint angle and the sampling grid orientation in the Fourier domain. By changing these parameters during data acquisition, the system can produce images at arbitrary orientations directly from the collected data, providing orientation flexibility without complicating the fundamental data collection process.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS7436349B1Controlling data collection to support SAR image rotation

Publication Date: 2008.10.14 NATIONAL TECHNOLOGY & ENGINEERING SOLUTIONS OF SANDIA LLC

AI summary

A desired rotation of a synthetic aperture radar (SAR) image can be facilitated by adjusting a SAR data collection operation based on the desired rotation. The SAR data collected by the adjusted SAR data collection operation can be efficiently exploited to form therefrom a SAR image having the desired rotational orientation.