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Deformation control using SAR interferometry: quantitative aspects

Michele Crosetto(1)

(1) Institut de Geomŕtica, Avinguda del Canal Olímpic, s/n, E-08860 Castelldefels (Barcelona), Spain

Abstract

The paper will consider the quantitative control of terrain deformations using the differential interferometric SAR (D-InSAR) technique. The capability of D-InSAR to measure wide area deformation fields has been extensively documented in the literature of the last decade. However, some of the published investigations rather focus on a qualitative use of the InSAR results, which is not adequate to support all the potential applications. An example is given by the deformation control in urban areas. This application, which is related to risk evaluation and public safety, needs to be characterised by high quality standards. In fact, in the management of the urban subsidence risk, a valuable support to the decision makers may be only provided through precise, accurate and reliable observations of the subsidence phenomena.

High quality standards in deformation monitoring are usually achieved by the geodetic techniques. D-InSAR may potentially offer a powerful and cost-effective alternative tool. However, different aspects of the D-InSAR technique have to be carefully considered. The paper will address in particular the following points: 1) The selection of the pixels used to estimate the deformation field. The proposed procedure uses the coherence to as selection criterion and adopt a phase unwrapping technique, which suitable to “sparse data”. In the selection there is a trade-off between the quality of the points and the sampling density. 2) The atmospheric effects that may severely degrade the accuracy and reliability of the D-InSAR results. We propose a procedure to assess these affects using stable areas located in the vicinity of the deformation area under analysis. 3) The estimation of the precision of the D-InSAR observations. The estimation of the precision of the D-InSAR observations, which represents a basic step to assess the actual capabilities and limits of the technique, requires a comprehensive analysis of all the sources of uncertainty that affect the D-InSAR results.

In the paper two D-InSAR scenarios will be considered: the simplest one, a single image pair, and the configuration based on the use of multiple observations. The latest one represents the best option in order to achieve quantitative results. However, there are several applications where at most only few image pairs are available.

The above mentioned aspects will be illustrated in the analysis of two test areas, which concern two important DInSAR applications: the observation of co-seismic deformations and the subsidence monitoring in urban areas. Particular attention will be paid to the quantitative aspects (precision, accuracy and reliability) of the estimated deformation fields.

 

Workshop presentation

Full paper

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry