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Summary of Proposal MTH0153

TitleGround deformation time series generation over a volcanic area by using X-Band SAR data
Investigator Sansosti, Eugenio - IREA-CNR, Remote Sensing
Team Members
Dr. Ricciardi, Giovanni Pasquale - Osservatorio Vesuviano INGV-OV, Geodesy
Summary

The objective of the proposed activity is to generate ground deformation time series over a time interval of about 2 years and by using TerraSAR-X data, via the application of Differential Interferometric SAR (DInSAR) techniques; subsequently, a validation of the obtained results will be carried out by comparison with independent measurements obtained via geodetic ground measurements (levelling and GPS).

The selected test site is the Campi Flegrei Caldera, a volcanic and highly urbanised area characterised by a restless ground deformation and by the availability of a dense network of levelling benchmarks and continuous GPS stations. For those reasons, the area is particularly suitable for testing ground deformation techniques that uses X-band SAR data.

In particular, we will apply the Small BASeline (SBAS) technique developed at IREA and whose details are reported in (Berardino et al., 2002). This algorithm allows an easy and effective combination of (unwrapped) multilook interferograms in order to obtain a ground deformation time series that satisfies a minimum energy constraint.

The required data are:

  • Stripmap Mode (SM);
  • single VV polarisation;
  • incidence angle around 23 deg, i.e., Strip_4;
  • Single Look Slant Range Complex (SSC) format.

The acquisition window should cover at least a two years time period, which is a reasonable time to build up a ground deformation time series and to have it validated by comparison with ground measurements, considered that ground campaigns are usually done once or twice a year.

The best acquisition plan would foresee as much acquisition as possible in order to reduce temporal decorrelation phenomena and reduce the sampling period of the deformation signal. The TerraSAR revisit time is 11 days, much shorter than currently available satellites. The possibility to have data so frequently would represent not only a benefit for the computation of the time series, but also an interesting feature of a deformation monitoring tool to be used in Civil Protection scenarios for volcano monitoring.

However, we understand that the TerraSAR-X satellite will be used half of its time for commercial purposes and half for scientific use. Therefore, we may reasonably expect to get data every 22 days as a minimum; more frequently acquisition are expected only if there is no conflict with any commercial order. With this acquisition plan, the total amount of data acquisition requested for a two years project would range between 33 and 66.

The proposal deliverables consist in two reports (one at the end of the first year, the other at the end of the project) that describe:

  • the implemented processing algorithm;
  • the difficulties encountered and the remedies adopted;
  • the results obtained;
  • assessment of the results via comparison with geodetic measurements.

The project has a strategic relevance for both IREA and Osservatorio Vesuviano and, therefore, will be funded by internal funds. IREA will provide all the support needed to set up the processing chain for X-band data, while Osservatorio Vesuviano will provide geodetic measurements to be used for validation.

References

P. Berardino, G. Fornaro, R. Lanari, E. Sansosti: “A new Algorithm for Surface Deformation Monitoring based on Small Baseline Differential SAR Interferograms”, IEEE Transactions on Geoscience and Remote Sensing, Vol. 40, No. 11, pp. 2375-2383, November 2002.

A. Pepe, E. Sansosti, P. Berardino, R. Lanari, “On the Generation of ERS/ENVISAT DInSAR Time-series via the SBAS Technique”, IEEE Geoscience and Remote Sensing Letters, Vol. 2, No. 3, pp. 265-269, July 2005.

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