Modeling and Processing L-Band Ground Based Radar Data for Landslides Early Warning

L-band radars have been proposed as possible way for monitoring landslides. In this paper, we examine and solve the principal difficulties arising in modeling and processing radar data, evidencing differences with more usual SAR imaging. Numerical examples in support of the proposed processing procedure are finally provided. 1. Introduction Amongst the different possible ways to have a continuous monitoring of areas which may be subject to landslides, L-band radars offer the possibility to penetrate foliage while still being able to get some understanding of the evolution of the scenario by means of differential imaging techniques. Differently from a large body of the literature, where imaging is performed by means of satellite-based radars (so that the movement of the satellite allows to rely on a synthetic aperture) the research activity considered in the following concern the exploitation of a fixed ground based radar, where the only eventually available movement of the sensor is achieved by a mechanical or electronic scanning of the antenna pattern. Such a circumstance implies a number of interesting differences, which are discussed in the following, with respect to more usual radar imaging modeling and processing techniques. In fact, a more detailed and difficult model is required for data simulation (which is useful to “tune” imaging procedure). Moreover, data processing requires more sophisticated techniques with respect to satellite-based imaging. On the other side, location on ground of the sensor allows a very simple deployment on those areas which are judged to have a risk of landslides. Also, the assumptions on “coherence” (see below), which are needed for differential imaging, are more easily verified with respect to differential interferometric SAR techniques. For the sake of simplicity of explanation, most concepts regarding simulation and processing are explained with reference to a simple “2D geometry,” that is, in a case where both fields and the scenario are invariant along one dimension, and the field is directed along such a direction. Such a simplifying assumption is then removed in Section 4. In the following, Section 2 is concerned with the problem of accurately simulating scenarios of interest, and attention is paid to the need of developing models which take into account the fact that the radar antenna is supposed to be in the near zone of the scenario under test. Then, Section 3 presents the basic idea for monitoring possible deformations of the soil on the basis of a differential imaging technique. In particular, the need of