Polarimetric Persistent Scatterer Interferometry for Ground Deformation Monitoring with VV-VH Sentinel-1 Data

With the launch of the Sentinel-1 satellites, it becomes easy to obtain long time-series dual-pol (i.e., VV and VH channels) SAR images over most areas of the world. By combining the information from both VV and VH channels, the polarimetric persistent scatterer interferometry (PolPSI) techniques is supposed to achieve better ground deformation monitoring results than conventional PSI techniques (using only VV channel) with Sentinel-1 data. According to the quality metric used for polarimetric optimizations, the most commonly used PolPSI techniques can be categorized into three main categories. They are PolPSI-ADI (amplitude dispersion index as the phase quality metric), PolPSI-COH (coherence as the phase quality metric), and PolPSI-AOS (taking adaptive optimization strategies). Different categories of PolPSI techniques are suitable for different study areas and with different performances. However, the study that simultaneously applies all the three types of PolPSI techniques on Sentinel-1 PolSAR images is rare. Moreover, there has been little discussion about different characteristics of the three types of PolPSI techniques and how to use them with Sentinel-1 data. To this end, in this study, three data sets in China have been used to evaluate the three types of PolPSI techniques’ performances. Based on results obtained, the different characteristics of PolPSI techniques have been discussed. The results show that all three PolPSI techniques can improve the phase quality of interferograms. Thus, more qualified pixels can be used for ground deformation estimation by PolPSI methods with respect to the PSI technique. Specifically, this pixel density improvement is 50%, 12%, and 348% for the PolPSI-ADI, PolPSI-COH, and POlPSI-AOS, respectively. PolPSI-ADI is the most efficient method, and it is the first choice for the area with abundant deterministic scatterers (e.g., urban areas). Benefitting from its adaptive optimization strategy, PolPSI-AOS has the best performances at the price of highest computation cost, which is suitable for rural area applications. On the other hand, limited by the medium resolution of Sentinel-1 PolSAR images, PolPSI-COH’s improvement with respect to conventional PSI is relatively insignificant.

DEFORMATION MONITORING AT EUROPEAN SCALE: THE COPERNICUS GROUND MOTION SERVICE

The Advanced Differential Interferometric SAR (A-DInSAR) technique is a class of powerful techniques to monitor ground motion. In the last two decades, the A-DInSAR technique has undergone an important development in terms of processing algorithms and the capability to monitor wide areas. This has been accompanied by an important increase of the Synthetic Aperture Radar (SAR) data acquisition capability by spaceborne sensors. An important step forward was the launch of the Copernicus Sentinel-1 constellation. The development of A-DInSAR based ground deformation services is now technically feasible. This paper describes some of the most important features of A-DInSAR. Then, it describes the European Ground Motion Service (EGMS), part of the Copernicus Land Monitoring Service, which represents a unique initiative for performing ground deformation monitoring on a European scale.

GROUND DEFORMATION MONITORING AT CONTINENTAL SCALE: THE EUROPEAN GROUND MOTION SERVICE

The Persistent Scatterer Interferometry is a powerful technique for ground motion detection and monitoring over wide areas. In the recent years, PSI has undergone a rapid evolution, largely thanks to the launch of the Copernicus Sentinel-1 constellation, the refinement of algorithms, and the increased computational capabilities. These factors allow for using Sentinel-1 interferometric data to develop ground deformation services for wide-area monitoring. Firstly, we review examples of services for national or regional deformation monitoring. The paper then describes the European Ground Motion Service (EGMS), part of the Copernicus Land Monitoring Service. The EGMS represents a unique initiative for performing ground deformation monitoring on a European scale.