Service Communautaire d'Information sur la Recherche et le Développement - CORDIS

Algorithm for the retrieval of soil moisture from satellite SAR data

A complete algorithm to generate soil moisture maps from SAR data in mountainous region has been developed and implemented. The algorithms includes the following phases:
- Extraction of the area of interest from SAR image.
- Calibration of backscattering coefficient taking into account the local incidence angle by means of the digital elevation model (DEM) and orbital parameters.
- Geocoding of the image.
- Masking of the SAR image for shadow and layover.
- Overlaying of a vegetation map, obtained from ground data, optical images or cross-polarized SAR data, to exclude forest areas from the analysis and to take into account the attenuation effect of the grass where it is present.
- Masking of image for forests.
- Correction for the effect of herbaceous vegetation on the backscattering coefficient by using a Discrete Element Radiative Transfer Model.
- Extraction of soil moisture at pixel scale by using an inversion approach based on a Neural Network trained with experimental or model generated data.
- Generation of soil moisture maps by aggregating a suitable number of pixels.

The algorithm has been tested on two test areas in North Italy: a flat agricultural area (Scrivia watershed) and a mountainous site (Cordevole watershed). In both cases, up to five levels of soil moisture between 10-15% and 45% have been identified, with a mean error of the 10%.

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