This paper reports a comparison of the capabilities of radar and optical satellite sensor data to estimate crop canopy cover, which is a key component of productivity estimates for sugar beet crops. A version of the water-cloud model that had previously been calibrated for this crop, was inverted to calculate Leaf Area Index (LAI) and crop cover ( f ) from ERS Synthetic Aperture Radar (SAR) data. SPOT data were used to calculate the Optimized Soil Adjusted Vegetation Index (OSAVI), from which crop canopy cover was estimated using a relationship determined previously by canopy modelling. Direct comparison of crop cover estimates from the two data sources indicates that their interrelationship is consistent between dates and seasons.