# Geometry-Driven Phase Error Estimation for Azimuth Multi-Channel SAR via Global Radar Landmark Control Point Library

## TL;DR

A new method for correcting phase errors in SAR imaging uses global radar landmarks to enable automatic and accurate calibration.

## Contribution

Introduces a geometry-driven phase error estimation framework using a global radar landmark control point library for automated SAR calibration.

## Key findings

- The proposed framework outperforms conventional methods in complex multi-scene environments.
- The method enables fully automated and reliable phase calibration for high-resolution wide-swath SAR systems.

## Abstract

What are the main findings?
A geometry-driven inter-channel phase error estimation framework is developed by introducing a Global Radar Landmark Control Point Library (GRL-CP) and automatic range–Doppler-based control point activation, eliminating scene-dependent and manual target selection.A frequency-domain correlation strategy based on activated radar landmarks enables robust and accurate phase error estimation, outperforming conventional correlation and subspace-based methods in complex multi-scene environments.

A geometry-driven inter-channel phase error estimation framework is developed by introducing a Global Radar Landmark Control Point Library (GRL-CP) and automatic range–Doppler-based control point activation, eliminating scene-dependent and manual target selection.

A frequency-domain correlation strategy based on activated radar landmarks enables robust and accurate phase error estimation, outperforming conventional correlation and subspace-based methods in complex multi-scene environments.

What is the main implication of the main findings?
The proposed framework enables fully automated, reliable, and scalable phase calibration for high-resolution wide-swath SAR systems, supporting operational and large-scale multi-channel SAR data processing.

The proposed framework enables fully automated, reliable, and scalable phase calibration for high-resolution wide-swath SAR systems, supporting operational and large-scale multi-channel SAR data processing.

Azimuth multi-channel synthetic aperture radar (SAR) is a core technology for achieving high-resolution wide-swath (HRWS) imaging. However, inter-channel phase inconsistency causes image amplitude distortion and phase accuracy degradation, which severely affects subsequent applications. Existing phase error estimation methods face specific limitations: the performance of subspace-based approaches degrades in complex scenes due to unreliable covariance matrix estimation, while conventional frequency-domain correlation methods rely on manual selection of strong scatterers, introducing inefficiency and subjectivity that precludes autonomous deployment. To address these issues, this paper proposes a geometry-driven inter-channel phase error estimation framework based on Global Radar Landmark Control Point Library (GRL-CP). The proposed framework replaces scene-dependent target selection with geometric-prior-driven control point activation. The GRL-CP library stores only the geodetic coordinates and scattering stability attributes of globally persistent radar landmarks, rather than image patches. For a new SAR acquisition, the echo position of these landmarks are predicted using a range–Doppler geometric model, enabling fully automatic and reliable control point activation. Based on the activated radar landmarks, inter-channel phase error is estimated using a frequency-domain correlation scheme. Experimental results on multi-channel spaceborne SAR datasets demonstrate that the proposed method achieves improved stability and accuracy under complex terrain scenarios.