Temporal H/alpha Target Decomposition for Landslide Monitoring Using Ku-Band GB-SAR Time Series

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
^°
and 13.54
^°
, 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.