Abstract
We investigate the applicability of the entropy (H)/ alpha (α̅) target decomposition realized by the temporally averaged coherency matrix, called temporal H/(α̅). We apply the temporal H/α̅ to ground-based synthetic aperture radar (GB-SAR) continuous monitoring data to characterize the scattering mechanism temporal change. As a case study, this work demonstrates the application of the temporal H/α̅ technique to landslide monitoring to detect and investigate the temporal scattering mechanism. The study acquired long-term GB-SAR polarimetric data over the postlandslide slope, Minami-Aso, Kumamoto, Japan. The study first investigated the property of the temporal H/α̅ parameters over selected land cover types by comparing it with that derived by spatial averaging (spatial H/α̅) to explain the landslide monitoring results. Also, the rainfall effects on the temporal H/α̅ parameters are demonstrated. The temporal H and α̅ values increase up to 0.07 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> and 13.54 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> , respectively, when the rainfall rate is 52.5 mm/h. The time-series analysis of the temporal H/α̅ indicates an obvious temporal transition of the scattering mechanism and a change of the backscattering stationarity when a landslide occurs. The applicability of the temporal H/α̅ for the change-detection is discussed by comparing it with the classical spatial H/α̅ parameters.
Highlights
S YNTHETIC aperture radar (SAR) is a coherent radar imaging sensor that is generally mounted on a moving platform, enabling Earth surface observation
We address an investigation of three land cover types, namely metal wire mesh cover (ROI-W), bare surface terrain (ROI-G), and vegetation cover (ROI-V)
We employed the dataset observed in the framework of a near-real-time polarimetric ground-based SAR (GB-SAR) monitoring campaign in Minami-Aso, Kumamoto, Japan
Summary
S YNTHETIC aperture radar (SAR) is a coherent radar imaging sensor that is generally mounted on a moving platform, enabling Earth surface observation. The ensemble averaging of the coherency matrix is typically performed by spatial multilooking due to insufficient polarimetric data along the temporal axis in spaceborne SAR [12]. Very few cases have been reported up to now, and all the above studies discussed only the applicability of polarimetric entropy out of the other decomposition parameters via temporally averaged coherency matrix. IZUMI AND SATO: TEMPORAL H/ALPHA TARGET DECOMPOSITION FOR LANDSLIDE MONITORING USING KU-BAND GB-SAR TIME SERIES exploit the advantage of continuous GB-SAR monitoring (i.e., a high acquisition rate and a stationary observation). The derived Htemp/αtemp time series is further compared with conventional H/αvalues derived by a spatially averaged coherency matrix referred to as Hspatial/αspatial.
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