How to fuse optical and radar imagery?

Information extraction from multi-sensor remote sensing imagery is an important and challenging task for many applications such as urban area mapping and change detection. There exist a lot of publications on this topic, but quite often they follow the same strategy: put all data into one stack and search for the best classifier for one particular example. Transfer of the results to other examples quite often fails. Especially during optical and radar data fusion different aspects and factors such as different acquisition geometries, incommensurable nature of features and many other parameters should be accounted for. In this paper we shall present a general workflow for optical and radar/SAR data fusion and discuss the main problems occurring when applying it for classification applications.