On the ability of dual-polarimetric SAR measurements to observe lava flows under different volcanic environments

In this study, we discuss the extra-value of polarimetric information in observing the lava flow. Dual-polarimetric Synthetic Aperture Radar (SAR) measurements are processed using a polarimetric change detector that, instead of looking at the variation of the backscatter intensity between a pair of images collected before and after the event, looks at changes in the polarimetric scattering behavior. We demonstrate that the scattering changes detected by the proposed polarimetric approach well-correlate with the footprint of the lava flow provided by external sources. In addition, we also compare the performance of the polarimetric change detector with conventional single-polarization metrics showing that the former one always outperforms the incoherent single-polarization measurements. To further demonstrate the robustness of the polarimetric change detectors, we selected two test cases that refer to vulcanic eruptions calling for completely different environments. The first one, related to the Etna volcano, calls for a lava flow over a vegetation-free environment; the second one is related to the Nyiragongo volcano and calls for a lava flow in a vegetated environment. Experimental results show that the polarimetric change detectors automatically adapt to the changing environment outperforming the single-polarization detectors.