Abstract:
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Revisiting time constitutes a key constraint for continuous
monitoring activities based on space- and airborne
synthetic aperture radar (SAR) acquisitions. Conversely, the
employment of terrestrial platforms overcomes this limitation and
makes it possible to perform time-continuous observations of small
space-scale phenomena. New research lines of SAR dealing with
the backscattering evolution of different types of scenarios become
hence possible through the analysis of ground-based SAR (gbSAR)
data collections. The Remote Sensing Laboratory of the Universitat
Politècnica de Catalunya drove a one-year measurements
campaign in the village of Sallent, northeastern Spain, using its
X-Band gbSAR sensor. The field experiment aimed at studying
the subsidence phenomenon induced by the salt mining activity
carried out in this area during the past decades. In this paper,
the polarimetric behavior of an urban environment is investigated
at different time scales. After a brief description of the test site
and the measurement campaign, the analysis is focused on the
stability on man-made structures at different time scales. PolSAR
data monthly acquired from June 2006 to July 2007 are employed
to stress the presence of nonstationary backscattering processes
within the urban scene and the effect they have on differential
phase information. Then, a filtering procedure aiming at reducing
backscattering randomness in one-day and long-term data
collections is then put forward. The improvements provided by
the proposed technique are assessed using a new polarimetric
descriptor, the time entropy. In the end, the importance of preserving
the interferometric phase information from nonstationary
backscattering contaminations using fully polarimetric data is
discussed |