Monitoring Soil Erosion in Agricultural Fields by Ers-1 Sar

Under the North Sea Agreement, Norway is obliged to reduce the discharge of nutrient salts from agricultural fields with 50% by 1995. In order to determine whether the policy have the desired effect, optical remote sensing will probably be used for monitoring the agricultural areas. However, the weather conditions in Norway in the late autumn makes it difficult to obtain cloud-free images, and is thus a limiting factor. In the paper an experiment is described that was carried out to determine whether S A R imagery can be used to detect late tillage in the autumn. The results of classifying images which have been speckle reduced, show that ploughed and stubble fields can be discriminated with a high degree of confidence when the soil moisture level is high. The best result is obtained using a field by field classification method. The experiments have also shown that radiometric and geometric correction of the image data using a terrain model is necessary to obtain the required accuracy.