Abstract
This paper discusses a full interferometry processing chain based on dual-orbit Sentinel-1A and Sentinel-1B (S1) synthetic aperture radar data and a combination of open-source routines from the Sentinel Application Platform (SNAP), Stanford Method for Persistent Scatterers (StaMPS), and additional routines introduced by the authors. These are used to provide vertical and East-West horizontal velocity maps over a study area in the south-western sector of the Po Plain (Italy) where land subsidence is recognized. The processing of long time series of displacements from a cluster of continuous global navigation satellite system stations is used to provide a global reference frame for line-of-sight–projected velocities and to validate velocity maps after the decomposition analysis. We thus introduce the main theoretical aspects related to error propagation analysis for the proposed methodology and provide the level of uncertainty of the validation analysis at relevant points. The combined SNAP–StaMPS workflow is shown to be a reliable tool for S1 data processing. Based on the validation procedure, the workflow allows decomposed velocity maps to be obtained with an accuracy of 2 mm/yr with expected uncertainty levels lower than 2 mm/yr. Slant-oriented and decomposed velocity maps provide new insights into the ground deformation phenomena that affect the study area arising from a combination of natural and anthropogenic sources.
Highlights
Satellite radar interferometry is recognized as an effective technique in different applications focused on deformation phenomena that occur on the Earth surface
The present study introduces the strategies adopted in the processing of S1 dual-orbit data using the Sentinel Application Platform (SNAP) and PSI–Stanford Method for Persistent Scatterers (StaMPS) open-source routines with constraint of single orbit products to a global reference frame, decomposition analysis and accuracy assessment at validation sites complemented by an error propagation analysis
We presented a PSI-based workflow to process dual-orbit S1 radar data with open-source tools complemented by the use of GNSS observations as constraints for the global reference frame and final accuracy assessment of the vertical and East-West oriented velocity maps
Summary
Satellite radar interferometry is recognized as an effective technique in different applications focused on deformation phenomena that occur on the Earth surface. The successful application of this methodology is strictly related to the ability to depict the displacement of ground targets at a very high level of accuracy (1–2 mm/yr) using synthetic aperture radar (SAR) images and time series analysis of displacements oriented along the Line Of Sight (LOS) directions. Since the first applications in the early 1990s, with the first generation of SAR satellites (ERS-1 and Radarsat-1), the temporal and spatial resolution increased, and a number of research fields have taken advantage of satellite radar interferometry. Differential SAR interferometry (InSAR) was initially used to measure deformation of the land surface through interpretation of interferograms, combined with digital elevation models (DEM) to remove the topographic contributions. Approaches based on the stacking of interferograms are adopted more frequently, and the methodologies can be differentiated
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