Long-term ERS/ENVISAT deformation time-series generation at full spatial resolution via the extended SBAS technique

Abstract

We extend the small baseline subset (SBAS) differential synthetic aperture radar (SAR) interferometry (DInSAR) approach to allow the generation of deformation time-series by processing, at the full spatial resolution scale, long sequences of European Remote Sensing (ERS-1 and ERS-2) and Environmental Satellite (ENVISAT) SAR data acquired with the same illumination geometry. In particular, we avoid the generation of ERS/ENVISAT cross-interferograms, which are severely affected by noise phenomena due to the carrier frequency separation of the two SAR systems, and we focus on single-platform interferograms only (i.e. ERS/ERS and ENVISAT/ENVISAT interferograms) that are properly combined by applying the singular value decomposition (SVD)-based SBAS approach. Moreover, we exploit the Doppler centroid variations of the post-2000 acquisitions of the ERS-2 sensor and the carrier frequency difference between the ERS-1/2 and the ENVISAT systems, in order to maximize the number of investigated SAR pixels and to improve their geocoding. The presented results, achieved on two data sets relevant to the Napoli Bay area and to the Murge region, both located in southern Italy, confirm the effectiveness of the extended SBAS technique and demonstrate the relevance of deformation analysis carried out at the scale of single buildings or human-made structures with more than 15 years of ERS and ENVISAT acquisitions.

Acknowledgements

This work was partially sponsored by the Italian Civil Protection Department (DPC), ESA and the Italian Space Agency (ASI). The precise ERS-1/2 satellite orbit state vectors have been provided by the Technical University of Delft, The Netherlands. The digital elevation model of the investigated area was acquired through the SRTM archive. We also thank Carlo Del Gaudio and Prospero De Martino of INGV-OV, who provided the levelling and GPS measurements, respectively, and Simone Guarino, Ferdinando Parisi and Maria Consiglia Rasulo for their technical support.

Notes

†No ERS-1 acquisitions are available after 1999 because the system was finally turned off.

‡Note that it may also include possible errors in the DEM used for the interferogram generation.