  Detailed parcel-level crop type mapping for the whole European Union (EU) is
necessary for the evaluation of agricultural policies. The Copernicus program,
and Sentinel-1 (S1) in particular, offers the opportunity to monitor
agricultural land at a continental scale and in a timely manner. However, so
far the potential of S1 has not been explored at such a scale. Capitalizing on
the unique LUCAS 2018 Copernicus in-situ survey, we present the first
continental crop type map at 10-m spatial resolution for the EU based on S1A
and S1B Synthetic Aperture Radar observations for the year 2018. Random forest
classification algorithms are tuned to detect 19 different crop types. We
assess the accuracy of this EU crop map with three approaches. First, the
accuracy is assessed with independent LUCAS core in-situ observations over the
continent. Second, an accuracy assessment is done specifically for main crop
types from farmers declarations from 6 EU member countries or regions totaling
>3M parcels and 8.21 Mha. Finally, the crop areas derived by classification are
compared to the subnational (NUTS 2) area statistics reported by Eurostat. The
overall accuracy for the map is reported as 80.3% when grouping main crop
classes and 76% when considering all 19 crop type classes separately. Highest
accuracies are obtained for rape and turnip rape with user and produced
accuracies higher than 96%. The correlation between the remotely sensed
estimated and Eurostat reported crop area ranges from 0.93 (potatoes) to 0.99
(rape and turnip rape). Finally, we discuss how the framework presented here
can underpin the operational delivery of in-season high-resolution based crop
mapping.
