Benchmarking Phase Filtering Techniques for Coherence Enhancement and Persistent Scatterer Selection in PSInSAR
Yan Akhbar Pamungkas, Shou Hao Chiang

Center for Space and Remote Sensing Research, National Central University, Taiwan

Department of Urban and Regional Planning, Universitas Brawijaya, Indonesia

Abstract

The accuracy of Persistent Scatterer Interferometric Synthetic Aperture Radar (PSInSAR) relies on effective coherence estimation to identify optimal Persistent Scatterer Point Candidates (PSCs). This study aims to evaluate and compare the performance of various phase filtering techniques, namely Boxcar, Goldstein, GAMMA, and Lee Filtering, with no filtering as the baseline, to compute the Spatial and Temporal Coherence for PSCs selection. A total of 173 Sentinel 1A Single Look Complex (SLC) images in ascending orbit with IW2 subswath and VV polarization images over Jakarta Capital City, Indonesia, were used. The processing workflow is composed of orbit correction, coregistration, wrapped interferogram generation, coherence estimation, and PSCs mask generation under different filtering scenarios. The results demonstrate significant variations in coherence performance among phase filtering methods, with spatial coherence consistently outperforming temporal coherence (spatial mean: 0.41 - 0.76 & temporal mean: 0.07 - 0.12). GAMMA filtering yields the highest spatial coherence (mean = 0.76), indicating its superior ability to suppress speckle while preserving coherent signals in urban environments. In contrast, the no-filter scenario produces the lowest coherence values, highlighting the essential of filtering in PSInSAR processing. Goldstein and Lee filters deliver reduced spatial coherence (means = 0.42 and 0.46), resulting in less detail and accuracy in persistent scatterer identification. Notably, Boxcar filtering achieves a spatial coherence (mean = 0.72) comparable to GAMMA, suggesting selective coherence preservation but with potential trade-offs in spatial detail. These findings underscore the critical influence of filter selection on the quality of coherence computation and have significant implications for enhancing PSInSAR accuracy in urban deformation studies. Future work will focus on comparing the results with unwrapped and cleaned phase as the input.

Keywords: PSInSAR, Coherence Estimation, Phase Filtering, Persistent Scatterer, Sentinel-1

Topic: Topic A: General Remote Sensing