Abstract
The permanent scatterers (PS) technique is a multi-interferogram algorithm for DInSAR analyses developed in the late nineties to overcome the difficulties related to the conventional approach, namely, phase decorrelation and atmospheric effects. The successful application of this technology to many geophysical studies is now pushing toward further improvements and optimizations. A possible strategy to increase the number of radar targets that can be exploited for surface deformation monitoring is the adoption of parametric super-resolution algorithms that can cope with multiple scattering centres within the same resolution cell. In fact, since a PS is usually modelled as a single pointwise scatterer dominating the background clutter, radar targets having cross-range dimension exceeding a few meters can be lost (at least in C-band datasets), due to geometrical decorrelation phenomena induced in the high normal baseline interferograms of the dataset. In this paper, the mathematical framework related to higher-order SAR interferometry is presented as well as preliminary results obtained on simulated and real data. It is shown how the PS density can be increased at the price of a higher computational load.
Highlights
Differential SAR interferometry (DInSAR) is a remote sensing technology capable of measuring possible displacements of radar targets along the line of sight (LOS) by computing the difference of the phase values of two SAR scenes gathered at different times over the same area of interest [1, 2, 3, 4, 5]
Since a permanent scatterers (PS) is usually modelled as a single pointwise scatterer dominating the background clutter, radar targets having cross-range dimension exceeding a few meters can be lost, due to geometrical decorrelation phenomena induced in the high normal baseline interferograms of the dataset
According to the hypothesis that a PS can be modelled as a single dominant target within the SAR resolution cell, the amplitude value of the signal backscattered by the target is independent of time and looking angle of the SAR acquisition, while the phase value φ of the ith interferogram relative to pixel P in the image can be modeled as φ P, ti = μ P, ti + CDi EMε(P) + η P, ti, i = 1, . . . , N, (1)
Summary
Differential SAR interferometry (DInSAR) is a remote sensing technology capable of measuring possible displacements of radar targets along the line of sight (LOS) by computing the difference of the phase values of two SAR scenes gathered at different times over the same area of interest [1, 2, 3, 4, 5]. The permanent scatterers (PS) technique [12, 13, 14], developed in the late nineties at Politecnico di Milano, takes advantage of long temporal series of SAR data, acquired over the area of interest along the same (nominal) satellite orbit, to filter out atmospheric artefacts and to identify a subset of image pixels where high-precision measurements can be carried out. Due to the adoption of a first-order scattering-centre model, amplitude data relative to the same image pixel are not used in the analysis, since they are supposed to be independent of time and aspect angle of the acquisition This simplifies the mathematical framework, since it involves (wrapped) phase data only and reduces the computational load.
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