Potential of Using Phase Correlation in Distributed Scatterer InSAR Applied to Built Scenarios

Guoqiang Shi,Bo Huang,Peifeng Ma,Hui Lin,Yuzhou Liu,Bowen Zhang

doi:10.3390/rs12040686

Abstract

The improved spatial resolution of Synthetic Aperture Radar (SAR) images from newly launched sensors has promoted a more frequent use of distributed scatterer (DS) interferometry (DSI) in urban monitoring, pursuing sufficient and detailed measurements. However, the commonly used statistical methods for homogeneous pixel clustering by exploring amplitude information are firstly, computationally intensive; furthermore, their necessity when applied to high-coherent built scenarios is little discussed in the literature. This paper explores the potential of using phase information for the detection of homogeneous pixels on built surfaces. We propose a simple phase-correlated pixel (PCP) clustering and introduce a coherence-weighted phase link (WPL), i.e., PCPWPL, to pursue a faster processing of interferogram phase denoising. Rather than relying on the statistical tests of amplitude characteristics, we exploit vector correlation in the complex domain to identify PCPs with similar phase observations, thus, avoiding the intensive hypothesis test. A coherence-weighted phase linking is applied for DS phase reconstruction. The estimation of geophysical parameters, e.g., deformation, is completed using an integrated network of persistent scatterers (PS) and DS. Efficiency of the proposed method is fairly illustrated by both synthetic and real data experiments. Pros and cons of the proposed PCPWPL were analyzed with the comparison to a conventional amplitude-based strategy using an X-band CosmoSkyMed dataset. It is demonstrated that the use of phase correlation is sufficient for DS monitoring in built scenarios, with equivalent measurement quantity and cheaper computational cost.

Highlights

As a space-to-Earth monitoring technology, the Synthetic Aperture Radar Interferometry (InSAR) received great success in a variety of geodetic applications [1,2]
The persistent scatterer (PS) interferometry (PSI) method [6,7] and its extensions were often used for the extraction of 3D information and/or the stability detection of infrastructure [8,9,10]
distributed scatterer (DS)-like pixels can exist and even account for a significant proportion of InSAR measurements in built scenarios revealed by high resolution X-band datasets [16,17]

Summary

Introduction

As a space-to-Earth monitoring technology, the Synthetic Aperture Radar Interferometry (InSAR) received great success in a variety of geodetic applications [1,2]. On the pavements, asphalt roads, building facades, roofs, other concrete surfaces etc., radar returns are weak due to specular reflections [20] Pixels over these areas are normally with higher phase noise than those of a direct reflecting, which makes them behave like a DS. Given that phase stability over built surfaces is usually higher than that of natural land covers, phase information could be reliable for clustering homogeneous pixels. The built surfaces provide relatively long-time coherent radar return than natural lands [17], even the DS-like targets are usually of higher phase quality they are not on par with the PSs. We directly explore pixel homogeneity from their interferometric phases, using the correlation of complex-vectors [37,38]. The proposed method is easy to implement and was proved to be able to detect equivalent DS points over built surfaces with much cheaper computational cost

Methodologies

Combined Processing of PS and DS

Simulated Experiments

Real Data Experiment