On the retrieval of bio-physical parameters from a multi-temporal series of ERS-SAR PRI images

Radar backscattering is a potentially valuable tool for retrieving the spatial distribution of several bio-physical parameters such as vegetation characteristics, surface soil moisture content and soil roughness. However, effects of all these parameters are comprised within the backscattered signal and therefore make a simple retrieval for one of its constituent components from a single valued ERS image impossible. Several empirical and physically based models have been proposed to estimate the soil moisture content from the radar cross section, but problems occur with the determination of the roughness and vegetation parameters. Using multi-frequency or multipolarized data could partly overcome this parameterization problem, but this option is often not available on spaceborne platforms. It is however possible to use single frequency and single polarization images to map the spatial soil moisture pattern or to identify cities or woods by using a time series of radar images.