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This document describes the second validation of the SENSAGRI Surface Soil Mositure (SSM) Product derived from Sentinel-1 and Sentinel-2 observations. The SSM information is provided at field scale (~0.1 km), where parcel borders are available, and at ~1km elsewhere. Time series of SSM product in 2017 and 2018 have been generated over the SENSAGRI test sites and stored in the SENSAGRI data repository. The validation consists of comparing time series of retrieved SSM against in situ measurements from ground campaigns and hydrologic networks. Standard metrics to quantify the retrieval accuracy have been adopted and the issue of the spatial representativeness error (SRE) of point-like SSM measurements is addressed. It results that SRE increases the ubrmse between 0.01m^3/m^3 and 0.02m^3/m^3, depending on the mean SSM values. Based on the available data set (N=4040), the estimated rmse is 0.06 m^3/m^3 (1sigma), after correcting for the SRE, and the Pearson correlation is 0.5. |
