On the application of PSI technique to landslide monitoring in the Daunia mountains, Italy

Fabio Bovenga(1) , L. Guerriero(2) , R. Nutricato(2) , A. Refice(3) , and J. Wasowski(4)

(1) Dip. Interateneo di Fisica - Bari, Via Amendola, 173, 70126, Italy
(2) Politecnico di Bari, Via Amendola, 173, 70126 Bari, Italy
(3) CNR-ISSIA, Via Amendola, 173, 70126 Bari, Italy
(4) CNR-IRPI, Via Amendola, 173, 70126 Bari , Italy

Abstract

Persistent Scatterers Interferometry (PSI) techniques allow to monitor millimetric displacements occurring on selected point targets exhibiting coherent radar backscattering properties. The technique is sensitive to the number and spatial distribution of point targets detected on the images, thus particular care must be used when dealing with scarcely-urbanized areas.

In the present work we apply the SPINUA (Stable Point Interferometry over Un-urbanised Areas) PSI processing technique [1] to the Daunia region located in Southern Apennines. This hilly region includes several isolated small hill-top towns affected by slope instability. In particular, an area of 25 x 25 km2, enclosing 10 urban centres, was selected for the analysis. A dataset of both descending (84) and ascending (51) ERS-1/2 acquisitions has been processed, to allow monitoring of slopes with a wide distribution of facing directions.

In the paper we focus on the reasons why different densities of stable targets are detected in apparently similar urban/peri-urban settings, and on some strategies to deal with this problem. In order to ensure an adequate distribution of coherent points for a reliable estimation of the atmospheric signal, the analysis has been limited to small image windows which enclose urban areas. This strategy, which has been also applied to other similar test sites [2], is justified by the fact that landslides with the highest socioeconomic impact are those involving the urban centres. The density of detected stable targets resulted suitable for 8 of the 10 investigated town areas, with a very good coverage of urban structures in 5 cases. The remaining 2 towns show a low number of PS, making difficult the detection of displacements. These outcomes could depend on the geometrical distribution of the coherent structures potentially corresponding to the PS. Although in several cases the displacement fields show clear evidence of moving objects located on urban and peri-urban areas, local knowledge of the investigated area and ground in situ inspections are required in order to interpret correctly the significance of PS motion data and to identify the main mechanism of the detected deformations.

Acknowledgements

This work was supported in part by the European Community (Contract No. EVGI 2001-00055 - Project LEWIS). Images were provided by ESA under the CAT-1 project number 2653, “Advanced SAR Interferometry techniques for landslide warning management”.

References [1] F. Bovenga, A. Refice, R. Nutricato, L. Guerriero, M.T. Chiaradia, “SPINUA: a flexible processing chain for ERS / ENVISAT long term interferometry”, Proc. ESA-ENVISAT Symposium 2004, Salzburg, Austria, 6-10 September, 2004.

[2] A. Refice, F. Bovenga, R. Nutricato, M.T. Chiaradia, J. Wasowski, “Land-cover classification-based Persistent Scatterers identification for peri-urban applications”, Proc. IGARSS’05, Seoul, Korea, 25-29 July 2005.

 

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