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This paper presents a new method, based on clustering and thresholding, to automatically perform binary change detection in multitemporal spectral indices. The method is denoted as Buffer-From-Cluster Approach (BFCA). To estimate the distributions of changed and unchanged pixels, as needed for the purpose of a reliable thresholding of a spectral index, a clustering algorithm is preliminarily applied to identify image objects possibly corresponding to areas where significant changes occurred. Then, a buffer zone is created around the selected cluster to identify unchanged areas surrounding changed ones. The cluster and the buffer zone are jointly analyzed to estimate the distributions of changed and unchanged pixels and to verify that they can be distinguished from each other. Finally, the results of thresholding and clustering are combined to generate the binary change map. The BFCA has been conceived to map the extent of the areas affected by a natural disaster like wildfire. To validate the proposed method, burned area maps produced by applying the BFCA to spectral indices derived from Sentinel-2 data have been compared to maps produced by the Copernicus Emergency Management Service. For testing the multi-hazard detection capability, the same kind of exercise has been carried out for a flooding test case too. The positive results of the comparison have confirmed the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

The proposed classification approach integrates multi-sensor, multi-source and contextual information associated with COSMO-SkyMed (CSK) and Pléiades images, thus formalizing the change-detection task in terms of a data fusion problem. Multi-temporal fusion "at the decision level" is used in this work. In particular, the change detection problem is operatively addressed through a multi-temporal supervised classification of multi-sensor CSK/Pléiades data. The method makes use of the Markov Random Field (MRF) theory to integrate the spatial context and the temporal correlation associated with the images acquired at the different dates, and is fully integrated with a region-based approach able to characterize the geometrical structures in the images through the employment of multiple segmentation maps at different scales. The approach has been applied to bespoke multi-temporal series consisting of pairs of CSK/Pléiades images that have been acquired as much as possible simultaneously, and provided by the Italian Space Agency (ASI) and the Centre National d'Études Spatiales (CNES) in the framework of CEOS (Committee on Earth Observation Satellites) Working Group on Disasters activities. The target is to monitor the changes in land cover classes. In order to exploit the potential of the change detection methodology and the spatial information of very high resolution (VHR) imagery, the proposed approach is implemented in the two following steps: - a first analysis conducted on the acquired imagery subsampled at a resolution of 10 m;- a second analysis performed on particularly interesting areas highlighted during the first step, making use of the imagery at the maximum available resolution.The target of the project is to test the potential of the proposed approach to monitor changes in the land use/land cover that can be related to:(i) the recovery phase after a natural disaster;(ii) the implementation of Disaster Risk Reduction (DRR) policies (e.g. monitoring of Sendai Framework Assessment - SFA indicators).Two case studies are presented:(i) The monitoring of the recovery phase in the aftermath of Hurricane Matthew in Haiti, which struck the Caribbean in October 2016, with a dataset composed of CSK/Pléiades pairs acquired in November 2015 (before the event), in October 2016 (few days after the event) and a year later, in October 2017.(ii) The monitoring of the surroundings of the city of Phnom Penh, Cambodia, at different time steps. The target is to monitor the changes in land cover classes related to SFA indicators. The focus is on a subset of the indicators C and D, which can be directly related to specific land cover classes. In particular C2-C, C-2FO, C-3, C-4, C-5, D2, D3, and D4.The work presented in this abstract is framed within the activity of the CEOS-DRM project (Committee on Earth Observation Satellites – Disaster Risk Management) funded by ASI. [ABSTRACT FROM AUTHOR]