Process for radar measurements of the movement of city areas and landsliding zones

Process for radar measurements of movements of city areas and landsliding zones which, having N>20 images made available by a synthetic aperture radar or SAR over a multi-year period, identifies for every resolution cell, the scatterers whose electromagnetic characteristics remain unaltered over time, and which are called Permanent Scatterers or PS, characterized in that said PS are identified through the following steps:

• (a) N−1 differential interferograms are formed in relation to the main image, called master, using a digital elevation model or DEM with vertical accuracy better than 50 meters;
• (b) for every pixel of the image of point (a) selected on the statistical properties of the modulus of the reflectivity, a temporal series of the interferometric phases is generated, and then, differences among temporal series that belong to neighbouring pixels are formed;
• (c) for every differential temporal series of point (b) the linear phase components are calculated in relation to the baseline and the phase components connected to the displacement model, already known, in relation to the time;
• (d) the relative error between the precise elevation of the pixel supplied from DEM of point (a) is associated with the linear phase component of point (c) in relation to the baseline;
• (e) the relative movement of the pixel in the direction of the SAR is associated to the polynominal phase variation in relation to the time of point (c);
• (f) the phase residuals are formed by subtracting the contributions calculated at points (d) and (e) after a phase unwrapping procedure on the sparse grid of the previously selected pixels;
• (g) the spectral power density of the phase residuals is analysed and (g.1) if the residuals relating to each single image are spatially correlated, attributed to atmospheric artefacts and removed;
• if (g.2) the further residual dispersion relating to each single image is too large the pixel is discarded.