Potential of ESA's Sentinel-2 for geological applications

Sentinel-2 is ESA's medium spatial resolution (10–60m) super-spectral instrument aimed at ensuring data continuity for global land surface monitoring of Landsat and SPOT. Several simulation studies have been conducted that show the potential of Sentinel-2 for estimating biophysical and biochemical parameters such as leaf area index, chlorophyll and nitrogen, and spectral products such as the red edge position and NDVI time series, providing data continuity for a number of other operational sensors. This paper aims at simulating Sentinel-2 products that are relevant to the geology and soil science community and we compare these to well established band ratio products from ASTER. As the basis for the simulation we use airborne hyperspectral imagery from the HyMAP sensor which were spectrally and spatially resampled to the resolutions of ASTER and Sentinel-2 using actual spectral response functions and pixel aggregate, respectively. The simulated image products demonstrate a good correspondence between ASTER and Sentinel-2 VNIR and SWIR bands. A number of band ratios are proposed for Sentinel-2 to derive the following products: ferric iron, ferrous iron, laterite, gossan, ferrous silicate and ferric oxides. These are compared to established band ratios of real ASTER data as well as simulated (from HyMAP) ASTER data and they correlate favourably. Investigating the spatial patterns reveals that there is a good match between the proposed Sentinel-2 band ratio products and those of ASTER. The resulting band ratio products are compared to the local geologic map of the imaged hydrothermal area (the Rodalquilar mining area, Cabo de Gata volcanic field, SE Spain). It is shown that they support the existing conceptual geologic model of the epithermal deposit.