Methodological advancements in using ERS SAR data for crop area estimation

The paper reports the results of methodological research into the use of multi-temporal ERS SAR data for crop area estimation. This work has been carried out as part of the pilot project on the use of ERS SAR data for rapid area estimates of agricultural crops which was initiated by the DG VI of the European Commission with the technical and scientific support from the MARS Agricultural Information Systems unit of the Joint Research Centre. In the paper, an innovative methodological framework is presented to generate multi-temporal ERS image composites for optimal crop classification. The use of this method for early season and full season time series is presented and discussed. We show that soil moisture and surface roughness induced variation in backscattering signatures needs careful consideration in a crop classification approach. The use of calibrated geocoded and speckle filtered ERS image data has lead to a classification accuracy, which for the given sites and crops, can be considered superior than those obtained with SPOT optical/IR data. It is shown that the further integration of ERS-derived crop area estimates in the MARS operational activities is feasible and recommendable, under the condition that certain operational constraints are met.