Forest biodiversity mapping based on PRISMA hyperspectral images

The current availability of hyperspectral images (HS) acquired by the PRecursore Iperspettrale della Missione Applicativa (PRISMA) mission of the Italian Space Agency and the recently launched Environmental Mapping and Analysis Program (EnMAP) mission of the German Space Agency, as well as the planned missions, e.g., the Copernicus Hyperspectral Imaging Mission for the Environment (CHIME) of the European Space Agency open unique perspectives for the multi-temporal mapping of forest biodiversity. In this work we use the high spectral resolution of spectral signatures provided by PRISMA images to derive unsupervised maps of vegetation diversity. Study areas are located in the National Parks of Gargano, Alta Murgia, Cilento-Vallo di Diano-Alburni, Appennino Lucano Val D’Agri Lagonegrese and Pollino, all in Southern Italy. Two indexes are used to pre-filter forested areas in HS images: Normalized Difference Vegetation Index (NDVI) and Normalized Difference Water Index (NDWI). The high spectral resolution of HS images allows to compute the different combinations of NIR and Red bands, for the computation of NDVI, and of NIR and SWIR bands for the computation of NDWI. This gives a more statistical weight to the thresholding of index maps to identify the areas covered by vegetation. The spectral signature profiles at the pixels, selected based on the index maps, are further processed using the Principal Component Analysis to reduce data dimensionality, and clustered using the K-means algorithm. As a result, a map of the vegetation diversity is obtained, with the location of pixels belonging to the different clusters identified by the K-means algorithms. The set of spectral signatures measured at pixels belonging to the same cluster are used to statistically characterize the reflectivity of vegetation.

 

ACKNOWLEDGMENTS

Project carried out using ORIGINAL PRISMA Products - © Italian Space Agency (ASI); the Products have been delivered under an ASI License to Use.