Satellite radar interferometry for deformation monitoring: a priori assessment of feasibility and accuracy

Conventional satellite repeat-pass radar interferometric measurements can be used for monitoring subsidence phenomena with high accuracies. This methodology was developed for mostly contiguous phase observations, enabling spatial coherence estimation and 2D phase unwrapping. Unfortunately, in many areas in the world, complete temporal decorrelation of the scattering characteristics occurs in a period reaching from days to months. In these circumstances, only urban areas and isolated stable scatterers maintain coherent. The problem is to detect these scatterers amidst their decorrelated neighbors, as spatial coherence estimation is not possible anymore. Methodology for the detection and analysis of such points, labeled permanent scatterers (PS), has been developed by Ferretti et al. [Ferretti, A., Prati, C., Rocca, F., 2000. Nonlinear subsidence rate estimation using permanent scatterers in differential SAR interferometry. IEEE Trans. Geosci. Remote Sens. 38(5), 2202-2212], using many (30 or more) SAR images of a particular site. This approach enables coherence estimation using temporal, pixel-based evaluation. Together, these points form a geodetic network of opportunity with different characteristics when compared to traditional geodetic network design. For practical purposes, it is necessary to define a set of guidelines to assess the feasibility of contiguous or PS radar interferometry for a specific deformation problem. This feasibility is dependent on the number of SAR data acquisitions available, their spatial and temporal baselines and observation statistics, and the expected spatial and temporal behavior of the deformation process. Here, we will discuss the evaluation procedure to assess a priori whether the techniques of contiguous and PS-InSAR are feasible for specific deformation studies in terms of precision and reliability. (c) 2004 Elsevier B.V. All rights reserved.