SAR-image derived soil moisture enhancement using GPR data

Measuring the spatial distribution of soil moisture is important for agricultural, hydrological, meteorological and climatological research and applications. In this study, a new technique is developed to create soil moisture maps, based on the inversion of SAR measurements (RADARSAT-2, fine quad polarization) combined with GPR measurements. The Integral Equation Model is used to invert the SAR measurements, assuming a constant surface roughness and correlation length for the entire field, while the GPR data are inverted using a full wave inversion method. High resolution GPR measurements taken at different times under different land and weather conditions are used to generate a relative soil moisture landscape. We assume that these soil moisture difference patterns show little variation over time. By combining the inverted SAR data with a transformation of the soil moisture difference landscape, a high resolution soil moisture map is generated. The high resolution soil moisture maps show good agreement with the measured GPR soil moisture maps. The advantage of this technique is that once the relative soil moisture difference landscape is created, it allows the creation of new high resolution soil moisture maps later, by only taking a SAR image.