Improvement of InSAR displacements based on GNSS station calibration over corner reflector

Abstract

This article presents an analysis of the effectiveness of performing a calibration through Global Navigation Satellite System (GNSS) data on different approaches of the Interferometric Synthetic Aperture Radar (InSAR). InSAR has become a key technique for monitoring ground surface, but its results often exhibit systematic biases and deviations from ground truth measurements. This study addresses the need for more reliable displacement data by evaluating a GNSS-based calibration approach across three InSAR processing approaches: i) Persistent Scattering Interferometry (PSI) method using the open-source software StaMPS, ii) PSI method using the commercial SARPROZ software and iii) the Quasi-PS method implemented with SARPROZ. Sentinel-1 A/B data from both ascending and descending orbits, covering the period from October 2017 to January 2019, were used. Displacement errors from the same points were modeled using polynomial regressions and calibrated using reference data from GNSS and levelling, both with submillimeter precision. The effectiveness of the calibration was assessed at two levels: locally (via a corner reflector) and globally (via a GNSS baseline several kilometers long). Results show that 25 out of 27 displacement time series required correction in the mean value, with StaMPS showing the greatest need for calibration. The calibration improved the original results at all scales and acted mainly on the mean difference, with linear calibration being the most robust and consistent option. These findings highlight the importance of incorporating ground truth data to enhance InSAR reliability and support its application in geodetic and structural monitoring.