A 2+1D phase unwrapping for Advanced DInSAR data processing
Michele Crosetto(1), Oriol Monserrat(1), Marta Agudo(1), Monika Sawicka(1), Grazia Rossi(2), Laura Calcagni(2) and Bruno Crippa(2)
(1) Institute of Geomatics, Av. Canal Olimpic s/n, 08860 Castelldefels (Barcelona), Spain
(2) University of Milan, Via Cicognara, Milan, Italy
The paper will be focused on a new procedure to unwrap the interferometric phases in large stacks of A-DInSAR data (Advanced Differential Interferometric SAR). The A-DInSAR techniques make used of large stacks of complex SAR images acquired over the same target area, and of advanced processing and analysis procedures to estimate the land deformation, separating the deformation signal from the phase contributions due to topography, atmosphere and noise. A key step in any A-DInSAR technique is the unwrapping of the interferometric phases.
The DInSAR processing steps generate different kinds of errors, which propagate in the entire chain. This work will be focused on a particular type of error generated during the DInSAR processing: the unwrapping related errors. The errors generated during the unwrapping process and the use of a procedure to automatically detect and correct them will be presented in this work. By an iterative process and exploiting the SVD least squares method for outliers rejection, this procedure determines the phases values associated with each SAR image, starting from a stack of interferograms. It works on previously selected pixels and provides good results with high observation redundancy, i.e. when there is a good ratio between observations (the interferometric phases) and unknown parameters (basically the number of SAR images, which usually coincides with the samples of the estimated deformation time series). Two key features of the procedure will be presented and discussed:
- the phase unwrapping capabilities of the proposed procedure,
- and the capability to control the propagation of the unwrapping errors in the subsequent processing stages, e.g. the filtering of the atmospheric effects.
The effectiveness of the procedure will be illustrated by using ERS and ASAR SAR data acquired over Barcelona (Spain) and other sites processed by the Institute of Geomatics and the Earth Sciences Department of the University of Milan.
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,