Agreement Index for Burned Area Mapping: Integration of Multiple Spectral Indices Using Sentinel-2 Satellite Images

Identifying fire-affected areas is of key importance to support post-fire management strategies and account for the environmental impact of fires. The availability of high spatial and temporal resolution optical satellite data enables the development of procedures for detailed and prompt post-fire mapping. This study proposes a novel approach for integrating multiple spectral indices to generate more accurate burned area maps by exploiting Sentinel-2 images. This approach aims to develop a procedure to combine multiple spectral indices using an adaptive thresholding method and proposes an agreement index to map the burned areas by optimizing omission and commission errors. The approach has been tested for the burned area classification of four study areas in Italy. The proposed agreement index combines multiple spectral indices to select the actual burned pixels, to balance the omission and commission errors, and to optimize the overall accuracy. The results showed the spectral indices singularly performed differently in the four study areas and that high levels of commission errors were achieved, especially for wildfires which occurred during the fall season (up to 0.93) Furthermore, the agreement index showed a good level of accuracy (minimum 0.65, maximum 0.96) for all the study areas, improving the performance compared to assessing the indices individually. This suggests the possibility of testing the methodology on a large set of wildfire cases in different environmental conditions to support the decision-making process. Exploiting the high resolution of optical satellite data, this work contributes to improving the production of detailed burned area maps, which could be integrated into operational services based on the use of Earth Observation products for burned area mapping to support the decision-making process

Spatial and auto correlation of ecological change: disturbance and perturbation analysis in Circeo National Park (South Latium, Italy).

“Ecological change” has different meanings: disturbance and perturbation. In this study, disturbance and perturbation were both spatially characterized using Normalize Vegetation Index (NDVI) delta maps (25 years: 1984-2009) derived by Landsat 5TM imagery. In Circeo National Park, the ecological change spatial pattern was characterized using geostatistic techniques. Instead, the spatial correlation of data was performed elaborating Euclidean Distance (ED) maps of urban and industrial areas and combining ED maps with disturbance cartography. At 45° a strong anisotropy was revealed by the empirical semivariogram of NDVI losses density, whereas NDVI's gains showed isotropy. The perturbation corresponds to processes of forests recolonization, whereas the disturbance was human induced

Agreement Index for Burned Area Mapping: Integration of Multiple Spectral Indices Using Sentinel-2 Satellite Images

Identifying fire-affected areas is of key importance to support post-fire management strategies and account for the environmental impact of fires. The availability of high spatial and temporal resolution optical satellite data enables the development of procedures for detailed and prompt post-fire mapping. This study proposes a novel approach for integrating multiple spectral indices to generate more accurate burned area maps by exploiting Sentinel-2 images. This approach aims to develop a procedure to combine multiple spectral indices using an adaptive thresholding method and proposes an agreement index to map the burned areas by optimizing omission and commission errors. The approach has been tested for the burned area classification of four study areas in Italy. The proposed agreement index combines multiple spectral indices to select the actual burned pixels, to balance the omission and commission errors, and to optimize the overall accuracy. The results showed the spectral indices singularly performed differently in the four study areas and that high levels of commission errors were achieved, especially for wildfires which occurred during the fall season (up to 0.93) Furthermore, the agreement index showed a good level of accuracy (minimum 0.65, maximum 0.96) for all the study areas, improving the performance compared to assessing the indices individually. This suggests the possibility of testing the methodology on a large set of wildfire cases in different environmental conditions to support the decision-making process. Exploiting the high resolution of optical satellite data, this work contributes to improving the production of detailed burned area maps, which could be integrated into operational services based on the use of Earth Observation products for burned area mapping to support the decision-making process

NDVI spatial pattern and the potential fragility of mixed forested areas in volcanic lake watersheds

Upland forested areas of watersheds undergo changes due to many factors including ecological succession, natural disturbances and human activity. The rate of natural and man-induced ecological changes in these landscapes is a function of the structural and functional characteristics of the component ecosystems. Analyzing spatial patterns and detecting fragile areas are thus crucial for making previsions about the chance and rate of disturbance propagation within and between the ecosystems. In this study we have tested the hypothesis of occurrence of a relationship between the extent of temporal change and spatial heterogeneity of mixed forested areas in the watershed of two Italian volcanic lakes by using remotely sensed data. Landsat images were acquired in summer 1987, 1992 and 2000, when Nature Reserves were established, and the temporal variation in the Normalized Difference Vegetation Index (NDVI) was determined by the change detection analysis. To analyze the spatial variability of NDVI, semivariograms were calculated using data from five randomly chosen forested areas (10 km(2)-wide) per watershed. Results show that NDVI varied greatly across the two study sites and most of the variation was spatially structured. NDVI varied also over time. A linear positive relationship was observed between the number of pixels changing between dates and the semivariogram range, as the maximum distance of spatial dependence estimated from the starting NDVI image. Spatial homogeneity of NDVI is thus suggested as an indicator of intrinsic fragility (i.e. susceptibility to change) of mixed forests and the semivariogram range as a rapid estimator that can be considered by forest managers and agencies. (C) 2012 Elsevier B.V. All rights reserved